Greenfield SA

General

Full name : Greenfield Susan A

First name : Susan A

Mail : University Department of Pharmacology\; Mansfield Road\; Oxford OX18 3QT

Zip Code :

City :

Country : United Kingdom

Email : susan.greenfield@pharm.ox.ac.uk

Phone : +441865271852

Fax :

Website : \/\/en.wikipedia.org\/wiki\/Susan_Greenfield

Directory :

References (76)

Title : A novel peptide 'T14' reflects age and photo-aging in human skin - Rocha_2023_Aging.(Albany.NY)_15_
Author(s) : Rocha S , Rates SG , Moswete T , Kalleberg K , Villa A , Harcup JP , Greenfield SA
Ref : Aging (Albany NY) , 15 : , 2023
Abstract : T14 is a 14mer peptide derived from the C-terminus of acetylcholinesterase (AChE). Once cleaved, it is independently bioactive of the parent molecule and enhances calcium influx in different cell types, in a range of scenarios: it binds to an allosteric site selectively on the alpha-7 receptor, where it modulates calcium influx and is thus a potential trophic agent, as already reported in a range of normal developmental scenarios. However, if inappropriately activated, this erstwhile beneficial effect converts to a toxic one, resulting in pathologies as disparate as Alzheimer's and various metastatic cancers. Given that epidermal keratinocyte cells have the same ectodermal origin as brain cells, as well as expressing AChE and the alpha-7 receptor, we have explored whether T14 plays a comparable role. Here we report that the T14 immunoreactivity is detectable in human keratinocytes with levels inversely related to age: this decrease is even more apparent with chronic photo-exposure and thus accelerated skin aging. We conclude that T14, an agent promoting cell growth and renewal in other parts of the body, also operates in skin, Moreover, monitoring of keratinocyte T14 levels might offer further insights into the now well reported link between degenerative diseases and epidermal cell profile.
ESTHER : Rocha_2023_Aging.(Albany.NY)_15_
PubMedSearch : Rocha_2023_Aging.(Albany.NY)_15_
PubMedID: 37382595

Title : A novel process driving Alzheimer's disease validated in a mouse model: Therapeutic potential - Greenfield_2022_Alzheimers.Dement.(N.Y)_8_e12274
Author(s) : Greenfield SA , Cole GM , Coen CW , Frautschy S , Singh RP , Mekkittikul M , Garcia-Rates S , Morrill P , Hollings O , Passmore M , Hasan S , Carty N , Bison S , Piccoli L , Carletti R , Tacconi S , Chalidou A , Pedercini M , Kroecher T , Astner H , Gerrard PA
Ref : Alzheimers Dement (N Y) , 8 :e12274 , 2022
Abstract : INTRODUCTION: The neuronal mechanism driving Alzheimer's disease (AD) is incompletely understood. METHODS: Immunohistochemistry, pharmacology, biochemistry, and behavioral testing are employed in two pathological contexts-AD and a transgenic mouse model-to investigate T14, a 14mer peptide, as a key signaling molecule in the neuropathology. RESULTS: T14 increases in AD brains as the disease progresses and is conspicuous in 5XFAD mice, where its immunoreactivity corresponds to that seen in AD: neurons immunoreactive for T14 in proximity to T14-immunoreactive plaques. NBP14 is a cyclized version of T14, which dose-dependently displaces binding of its linear counterpart to alpha-7 nicotinic receptors in AD brains. In 5XFAD mice, intranasal NBP14 for 14 weeks decreases brain amyloid and restores novel object recognition to that in wild-types. DISCUSSION: These findings indicate that the T14 system, for which the signaling pathway is described here, contributes to the neuropathological process and that NBP14 warrants consideration for its therapeutic potential.
ESTHER : Greenfield_2022_Alzheimers.Dement.(N.Y)_8_e12274
PubMedSearch : Greenfield_2022_Alzheimers.Dement.(N.Y)_8_e12274
PubMedID: 35415206

Title : Characterization of a Bioactive Peptide T14 in the Human and Rodent Substantia Nigra: Implications for Neurodegenerative Disease - Greenfield_2022_Int.J.Mol.Sci_23_
Author(s) : Greenfield SA , Ferrati G , Coen CW , Vadisiute A , Molnar Z , Garcia-Rates S , Frautschy S , Cole GM
Ref : Int J Mol Sci , 23 : , 2022
Abstract : The substantia nigra is generally considered to show significant cell loss not only in Parkinson's but also in Alzheimer's disease, conditions that share several neuropathological traits. An interesting feature of this nucleus is that the pars compacta dopaminergic neurons contain acetylcholinesterase (AChE). Independent of its enzymatic role, this protein is released from pars reticulata dendrites, with effects that have been observed in vitro, ex vivo and in vivo. The part of the molecule responsible for these actions has been identified as a 14-mer peptide, T14, cleaved from the AChE C-terminus and acting at an allosteric site on alpha-7 nicotinic receptors, with consequences implicated in neurodegeneration. Here, we show that free T14 is co-localized with tyrosine hydroxylase in rodent pars compacta neurons. In brains with Alzheimer's pathology, the T14 immunoreactivity in these neurons increases in density as their number decreases with the progression of the disease. To explore the functional implications of raised T14 levels in the substantia nigra, the effect of exogenous peptide on electrically evoked neuronal activation was tested in rat brain slices using optical imaging with a voltage-sensitive dye (Di-4-ANEPPS). A significant reduction in the activation response was observed; this was blocked by the cyclized variant of T14, NBP14. In contrast, no such effect of the peptide was seen in the striatum, a region lacking the T14 target, alpha-7 receptors. These findings add to the accumulating evidence that T14 is a key signaling molecule in neurodegenerative disorders and that its antagonist NBP14 has therapeutic potential.
ESTHER : Greenfield_2022_Int.J.Mol.Sci_23_
PubMedSearch : Greenfield_2022_Int.J.Mol.Sci_23_
PubMedID: 36361905

Title : An Alternative Approach to Study Primary Events in Neurodegeneration Using Ex Vivo Rat Brain Slices - Brai_2018_J.Vis.Exp__
Author(s) : Brai E , Cogoni A , Greenfield SA
Ref : J Vis Exp , : , 2018
Abstract : Despite numerous studies that attempt to develop reliable animal models which reflecting the primary processes underlying neurodegeneration, very few have been widely accepted. Here, we propose a new procedure adapted from the well-known ex vivo brain slice technique, which offers a closer in vivo-like scenario than in vitro preparations, for investigating the early events triggering cell degeneration, as observed in Alzheimer's disease (AD). This variation consists of simple and easily reproducible steps, which enable preservation of the anatomical cytoarchitecture of the selected brain region and its local functionality in a physiological milieu. Different anatomical areas can be obtained from the same brain, providing the opportunity to perform multiple experiments with the treatments in question in a site-, dose-, and time-dependent manner. Potential limitations which could affect the outcomes related to this methodology are related to the conservation of the tissue, i.e., the maintenance of its anatomical integrity during the slicing and incubation steps and the section thickness, which can influence the biochemical and immunohistochemical analysis. This approach can be employed for different purposes, such as exploring molecular mechanisms involved in physiological or pathological conditions, drug screening, or dose-response assays. Finally, this protocol could also reduce the number of animals employed in behavioral studies. The application reported here has been recently described and tested for the first time on ex vivo rat brain slices containing the basal forebrain (BF), which is one of the cerebral regions primarily affected in AD. Specifically, it has been demonstrated that the administration of a toxic peptide derived from the C-terminus of acetylcholinesterase (AChE) could prompt an AD-like profile, triggering, along the antero-posterior axis of the BF, a differential expression of proteins altered in AD, such as the alpha7 nicotinic receptor (alpha7-nAChR), phosphorylated Tau (p-Tau), and amyloid beta (Abeta).
ESTHER : Brai_2018_J.Vis.Exp__
PubMedSearch : Brai_2018_J.Vis.Exp__
PubMedID: 29708553

Title : Modulatory Effects of a Novel Cyclized Peptide in Reducing the Expression of Markers Linked to Alzheimer's Disease - Brai_2018_Front.Neurosci_12_362
Author(s) : Brai E , Simon F , Cogoni A , Greenfield SA
Ref : Front Neurosci , 12 :362 , 2018
Abstract : Despite many studies attempt to identify the primary mechanisms underlying neurodegeneration in Alzheimer's disease (AD), the key events still remain elusive. We have previously shown that a peptide cleaved from the acetylcholinesterase (AChE) C-terminus (T14) can play a pivotal role as a signaling molecule in neurodegeneration, via its interaction with the alpha7 nicotinic acetylcholine receptor. The main goal of this study is to determine whether a cyclized variant (NBP14) of the toxic AChE-derived peptide can antagonize the effects of its linear counterpart, T14, in modulating well-known markers linked to neurodegeneration. We investigate this hypothesis applying NBP14 on ex-vivo rat brain slices containing the basal forebrain. Western blot analysis revealed an inhibitory action of NBP14 on naturally occurring T14 peptide, as well as on endogenous amyloid beta, whereas the expression of the nicotinic receptor and phosphorylated Tau was relatively unaffected. These results further confirm the neurotoxic properties of the AChE-peptide and show for the first time in an ex-vivo preparation the possible neuroprotective activity of NBP14, over a protracted period of hours, indicating that T14 pathway may offer a new prospect for therapeutic intervention in AD pathobiology.
ESTHER : Brai_2018_Front.Neurosci_12_362
PubMedSearch : Brai_2018_Front.Neurosci_12_362
PubMedID: 29950969

Title : Tumor cell migration is inhibited by a novel therapeutic strategy antagonizing the alpha-7 receptor - Pepper_2017_Oncotarget_8_11414
Author(s) : Pepper C , Tu H , Morrill P , Garcia-Rates S , Fegan C , Greenfield SA
Ref : Oncotarget , 8 :11414 , 2017
Abstract : A 14mer peptide (T14) derived from the C-terminus of acetylcholinesterase (AChE) selectively activates metastatic breast cancer cells via the alpha-7 nicotinic receptor (alpha7 nAChR). This naturally occurring peptide is also present in brain, is elevated in Alzheimer's disease, and is antagonised by a cyclized variant (NBP-14). Here we investigated the effects of NBP-14 in six different cancer cell lines, primary leukemia B-cells and normal B-cells. All cells tested expressed alpha7 nAChR, intracellular and extracellular T14. However, NBP-14 showed low toxicity and weak anti-proliferative effects in the majority of the cell lines and was even less toxic in normal B-cells when compared to primary chronic lymphocytic leukemia cells (P < 0.001). Given the potential role of T14 peptide in metastasis, we next investigated the effects of NBP-14 on tumor cell migration, where it caused a dose-dependent reduction. The extent of NBP-14 inhibition positively correlated with the migration of the cells (r2 = 0.45; P = 0.06). Furthermore, NBP-14 preferentially inhibited the migration of primary leukemia cells when compared with normal B-cells (P = 0.0002); when the normal B-cell data was excluded, this correlation was strengthened (r2 = 0.80; P = 0.006). Importantly, the constitutive alpha7 nAChR expression positively correlated with intracellular T14 levels (r2 = 0.91; P = 0.0003) and inversely correlated with extracellular T14 levels in the cell culture supernatants (r2 = -0.79; P = 0.034). However, in the presence of NBP-14, alpha7 nAChR expression was reduced (P = 0.04) and the most migratory cells showed the largest reduction in expression. In conclusion, NBP-14-mediated antagonism of the alpha7 nAChR offers a novel therapeutic strategy with the potential to inhibit tumor cell migration.
ESTHER : Pepper_2017_Oncotarget_8_11414
PubMedSearch : Pepper_2017_Oncotarget_8_11414
PubMedID: 28077796

Title : Cancer and neurodegeneration: two sides, same coin? -
Author(s) : Garcia-Rates S , Greenfield SA
Ref : Oncotarget , 8 :22307 , 2017
PubMedID: 28423607

Title : A Novel Ex Vivo Model to Investigate the Underlying Mechanisms in Alzheimer's Disease - Brai_2017_Front.Cell.Neurosci_11_291
Author(s) : Brai E , Stuart S , Badin AS , Greenfield SA
Ref : Front Cell Neurosci , 11 :291 , 2017
Abstract : Currently there is no widely accepted animal model reproducing the full pathological profile of Alzheimer's disease (AD), since the basic mechanisms of neurodegeneration are still poorly understood. We have proposed that the interaction between the alpha7 nicotinic acetylcholine receptor (alpha7-nAChR) and a recently discovered toxic peptide, cleaved from the acetylcholinesterase (AChE) C-terminus, could account for the aberrant processes occurring in AD. In this article we describe a new application on ex vivo model procedure, which combines the advantages of both in vivo and in vitro preparations, to study the effects of the AChE-derived peptide on the rat basal forebrain (BF). Western blot analysis showed that the levels of alpha7-nAChR, p-Tau and Abeta are differentially expressed upon the AChE-peptide administration, in a selective site-dependent manner. In conclusion, this methodology demonstrates the action of a novel peptide in triggering an AD-like phenotype and proposes a new ex vivo approach for manipulating and monitoring neurochemical processes contributing to neurodegeneration, in a time-dependent and site-specific manner.
ESTHER : Brai_2017_Front.Cell.Neurosci_11_291
PubMedSearch : Brai_2017_Front.Cell.Neurosci_11_291
PubMedID: 29033787

Title : (I) Pharmacological profiling of a novel modulator of the alpha7 nicotinic receptor: Blockade of a toxic acetylcholinesterase-derived peptide increased in Alzheimer brains - Garcia-Rates_2016_Neuropharmacol_105_487
Author(s) : Garcia-Rates S , Morrill P , Tu H , Pottiez G , Badin AS , Tormo-Garcia C , Heffner C , Coen CW , Greenfield SA
Ref : Neuropharmacology , 105 :487 , 2016
Abstract : The primary cause of Alzheimer's disease is unlikely to be the much studied markers amyloid beta or tau. Their widespread distribution throughout the brain does not account for the specific identity and deep subcortical location of the primarily vulnerable neurons. Moreover an unusual and intriguing feature of these neurons is that, despite their diverse transmitters, they all contain acetylcholinesterase. Here we show for the first time that (1) a peptide derived from acetylcholinesterase, with independent trophic functions that turn toxic in maturity, is significantly raised in the Alzheimer midbrain and cerebrospinal fluid; (2) a synthetic version of this peptide enhances calcium influx and eventual production of amyloid beta and tau phosphorylation via an allosteric site on the alpha7 nicotinic receptor; (3) a synthetic cyclic version of this peptide is neuroprotective against the toxicity not only of its linear counterpart but also of amyloid beta, thereby opening up the prospect of a novel therapeutic approach.
ESTHER : Garcia-Rates_2016_Neuropharmacol_105_487
PubMedSearch : Garcia-Rates_2016_Neuropharmacol_105_487
PubMedID: 26867503

Title : (II) Physiological profiling of an endogenous peptide in the basal forebrain: Age-related bioactivity and blockade with a novel modulator - Badin_2016_Neuropharmacol_105_47
Author(s) : Badin AS , Morrill P , Devonshire IM , Greenfield SA
Ref : Neuropharmacology , 105 :47 , 2016
Abstract : Previous studies have suggested that neurodegeneration is an aberrant form of development, mediated by a novel peptide from the C-terminus of acetylcholinesterase (AChE). Using voltage-sensitive dye imaging we have investigated the effects of a synthetic version of this peptide in the in vitro rat basal forebrain, a key site of degeneration in Alzheimer's disease. The brain slice preparation enables direct visualisation in real-time of sub-second meso-scale neuronal coalitions ('Neuronal Assemblies') that serve as a powerful index of brain functional activity. Here we show that (1) assemblies are site-specific in their activity profile with the cortex displaying a significantly more extensive network activity than the sub-cortical basal forebrain; (2) there is an age-dependency, in both cortical and sub-cortical sites, with the younger brain (p14 rats) exhibiting more conspicuous assemblies over space and time compared to their older counterparts (p35-40 rats). (3) AChE-derived peptide significantly modulates the dynamics of neuronal assemblies in the basal forebrain of the p14 rat with the degree of modulation negatively correlated with age, (4) the differential in assembly size with age parallels the level of endogenous peptide in the brain, which also declines with maturity, and (5) this effect is completely reversed by a cyclised variant of AChE-peptide, 'NBP14'. These observations are attributed to an enhanced calcium entry that, according to developmental stage, could be either trophic or toxic, and as such may provide insight into the basic neurodegenerative process as well as an eventual therapeutic intervention.
ESTHER : Badin_2016_Neuropharmacol_105_47
PubMedSearch : Badin_2016_Neuropharmacol_105_47
PubMedID: 26773199

Title : High-resolution spatio-temporal bioactivity of a novel peptide revealed by optical imaging in rat orbitofrontal cortex in vitro: Possible implications for neurodegenerative diseases - Badin_2013_Neuropharmacol_73C_10
Author(s) : Badin AS , Eraifej J , Greenfield SA
Ref : Neuropharmacology , 73C :10 , 2013
Abstract : Acetylcholinesterase (AChE) is now well known to have a secondary, non-enzymatic function independent of cholinergic transmission. In the last decade, the part of the molecule responsible for this action has been identified, i.e. a 14 amino acid peptide fragment ('T14'), deriving from the C-terminus of AChE: this peptide has been shown to be bioactive in a range of preparations and to act at an allosteric site on alpha7 nicotinic acetylcholine receptors (alpha7-nAChRs). Of particular significance is the finding that AChE-related peptides trigger calcium-induced neurotoxicity that may be pivotal in the process of neurodegenerative diseases, such as Alzheimer's. However to date all studies have been performed on isolated cell preparations. The aim of this study was therefore to characterise the bioactivity of T14 on meso-scale in vitro cortical networks ('neuronal assemblies') from rat brain slices containing orbitofrontal cortex. Local field potential (LFP) recordings showed that the T14 peptide has a selective, holistic action on cortical networks in a modulatory biphasic manner i.e. predisposing excitation at concentrations of up to 1 muM, after which the trend is reversed in favour of inhibition at higher doses (>1 muM). By contrast, a scrambled variant of the T14 peptide sequence (S14), showed no significant changes in neuronal activation. Optical imaging using voltage-sensitive dyes (VSDI) corroborated the electrophysiological findings and also provided further insight into the spatial dynamics of the effects of the peptide: T14 application had a facilitatory effect i.e. increased the time-course of activation at sub-micromolar concentrations only (700 nM) without significantly affecting the spread of evoked assemblies. Moreover: co-applying T14 with the alpha7-nAChR competitive antagonist methyllycaconitine (MLA) produced inhibition in activation synchrony not seen with either agent on their own, suggesting an additive inhibitory effect. In conclusion, the T14 peptide derived from AChE produced a dose-dependent biphasic modulation of cortical networks activity dependent on the alpha7-nAChR: these findings should thus provide a more comprehensive insight into the immediate actions of a novel bioactive agent of high potential relevance to neurodegenerative disorders such as Alzheimer's disease.
ESTHER : Badin_2013_Neuropharmacol_73C_10
PubMedSearch : Badin_2013_Neuropharmacol_73C_10
PubMedID: 23711548

Title : Additive Toxicity of beta-Amyloid by a Novel Bioactive Peptide In Vitro: Possible Implications for Alzheimer's Disease - Garcia-Rates_2013_PLoS.One_8_e54864
Author(s) : Garcia-Rates S , Lewis M , Worrall R , Greenfield SA
Ref : PLoS ONE , 8 :e54864 , 2013
Abstract : BACKGROUND: beta-amyloid is regarded as a significant factor in Alzheimer's disease: but inefficient therapies based on this rationale suggests that additional signalling molecules or intermediary mechanisms must be involved in the actual initiation of the characteristic degeneration of neurons. One clue could be that acetylcholinesterase, also present in amyloid plaques, is aberrant in peripheral tissues such as blood and adrenal medulla that can be implicated in Alzheimer's disease. The aim of this study was to assess the bioactivity of a fragment of acetylcholinesterase responsible for its non-enzymatic functions, a thirty amino acid peptide ("T30") which has homologies with beta-amyloid.
METHODS: CELL VIABILITY WAS MEASURED BY SULFORHODAMINE B ASSAY AND ALSO LACTATE DEHYDROGENASE ASSAY: meanwhile, changes in the status of living cells was monitored by measuring release of acetylcholinesterase in cell perfusates using the Ellman reagent. FINDINGS: T30 peptide and beta-amyloid each have toxic effects on PC12 cells, comparable to hydrogen peroxide(.) However only the two peptides selectively then evoke a subsequent, enhanced release in acetylcholinesterase that could only be derived from the extant cells. Moreover, unlike hydrogen peroxide, the T30 peptide selectively shifted a sub-threshold dose of beta-amyloid to a toxic effect, which also resulted in a comparable enhanced release of acetylcholinesterase. INTERPRETATION: This is the first study comparing directly the bioactivity of beta-amyloid with a peptide derived from acetylcholinesterase: the similarity in action suggests that the sequence homology between the two compounds might have a functional and/or pathological relevance. The subsequent enhanced release of acetylcholinesterase from the extant cells could reflect a primary 'compensatory' response of cells prone to degeneration, paradoxically providing further availability of the toxic C-terminal peptide to modulate the potency of beta-amyloid. Such a cycle of events may provide new insights into the mechanism of continuing selective cell loss in Alzheimer's disease and related degenerative disorders.
ESTHER : Garcia-Rates_2013_PLoS.One_8_e54864
PubMedSearch : Garcia-Rates_2013_PLoS.One_8_e54864
PubMedID: 23390503

Title : From protein to peptides: a spectrum of non-hydrolytic functions of acetylcholinesterase - Halliday_2012_Protein.Pept.Lett_19_165
Author(s) : Halliday AC , Greenfield SA
Ref : Protein Pept Lett , 19 :165 , 2012
Abstract : Acetylcholinesterase (AChE), a member of the alpha/beta-hydrolase fold superfamily of proteins, is a serine hydrolase responsible for the hydrolysis of the well studied neurotransmitter acetylcholine (ACh). However, it is becoming clear that AChE has a range of actions other than this 'classical' role. Non-classical AChE functions have been identified in apoptosis, stress-responses, neuritogenesis, and neurodegeneration. Furthermore, these non-classical roles are attributable not only to the native protein, which appears to act as a mediary binding protein under a number of circumstances, but also to peptides cleaved from the parent protein. Peptides cleaved from AChE can act as independent signalling molecules. Here we discuss the implications of non-hydrolytic functions of this multi-tasking protein.
ESTHER : Halliday_2012_Protein.Pept.Lett_19_165
PubMedSearch : Halliday_2012_Protein.Pept.Lett_19_165
PubMedID: 21933122

Title : Evaluation of a technique to identify acetylcholinesterase C-terminal peptides in human serum samples - Halliday_2010_Chem.Biol.Interact_187_110
Author(s) : Halliday AC , Kim O , Bond CE , Greenfield SA
Ref : Chemico-Biological Interactions , 187 :110 , 2010
Abstract : A novel theory for neurodegeneration is that non-cholinergic functions of acetylcholinesterase (AChE) are responsible for the progressive death of global neurons. The C-terminal region of AChE has been shown to be responsible for non-cholinergic actions of AChE by binding to an allosteric site on the alpha 7-nicotinic acetylcholine receptor, thereby causing calcium influx; the resultant signal has trophic effects in immature neurons, but toxic effects in mature neurons. Although there is strong in vitro and in vivo evidence for the involvement of this C-terminal region of AChE in neurodegeneration, a cleaved C-terminal peptide has not yet been identified in human brains. This preliminary study aimed to identify the cleaved AChE C-terminal peptide in serum from human Alzheimer's disease patients using immunoaffinity purification. A number of antibodies were tested for sensitivity and specificity towards peptide sequences from the C-terminus. Although the antibodies were able to identify peptide in vitro, peptide was not detected using immunoaffinity purification of human serum, possibly due to insufficient detection limits of the antibody. Therefore more sensitive techniques are required to identify cleaved AChE C-terminal peptides in human samples. None the less, C-terminal AChE peptide might act as a signalling molecule in an as yet unexplored system.
ESTHER : Halliday_2010_Chem.Biol.Interact_187_110
PubMedSearch : Halliday_2010_Chem.Biol.Interact_187_110
PubMedID: 20156431

Title : Impact of detergents on the activity of acetylcholinesterase and on the effectiveness of its inhibitors - Zimmermann_2009_Biol.Chem_390_19
Author(s) : Zimmermann M , Westwell MS , Greenfield SA
Ref : Biol Chem , 390 :19 , 2009
Abstract : Acetylcholinesterase (AChE) plays a central role in the development of Alzheimer's disease: AChE inhibition for preventing the characteristic dwindling of acetylcholine levels constitutes the current standard treatment for the disorder. Amongst the diverse risk factors contributing to the degenerative process, high cholesterol causes a reduction in the effectiveness of the otherwise therapeutic inhibitors of AChE. Our biochemical study on the activity of AChE elucidates the effect of amphiphilic molecules on the activity and kinetics of AChE, and sheds light onto the nature of the impact of these amphiphilic molecules on enzyme-inhibitor interactions. Using kinetic studies we discovered that detergents alter the enzymatic activity of AChE through an uncompetitive mechanism. Additional experiments using AChE inhibitors (amphiphilic procaine hydrochloride, hydrophobic tetrabutylammonium bromide) in the absence or presence of detergent further illustrate the detergent-enzyme-solvent interactions. The results contribute to the understanding of the importance of hydrophobic-lipophilic interactions for the correct function of AChE and its inhibitors. We present a model system for the study of lipid-related alterations in the activity of isolated AChE in the central nervous system. This model may also be used to assess and predict the effectiveness of AChE inhibitors, which are traditionally used for the treatment of cognitive impairment, under pathological (high-cholesterol) conditions.
ESTHER : Zimmermann_2009_Biol.Chem_390_19
PubMedSearch : Zimmermann_2009_Biol.Chem_390_19
PubMedID: 19007306

Title : Upregulation of alpha7 Nicotinic Receptors by Acetylcholinesterase C-Terminal Peptides - Bond_2009_PLoS.One_4_e4846
Author(s) : Bond CE , Zimmermann M , Greenfield SA
Ref : PLoS ONE , 4 :e4846 , 2009
Abstract : BACKGROUND: The alpha-7 nicotinic acetylcholine receptor (alpha7-nAChR) is well known as a potent calcium ionophore that, in the brain, has been implicated in excitotoxicity and hence in the underlying mechanisms of neurodegenerative disorders such as Alzheimer's disease. Previous research implied that the activity of this receptor may be modified by exposure to a peptide fragment derived from the C-terminal region of the enzyme acetylcholinesterase. This investigation was undertaken to determine if the functional changes observed could be attributed to peptide binding interaction with the alpha7-nAChR, or peptide modulation of receptor expression. METHODOLOGY/PRINCIPAL FINDINGS: This study provides evidence that two peptides derived from the C-terminus of acetylcholinesterase, not only selectively displace specific bungarotoxin binding at the alpha7-nAChR, but also alter receptor binding properties for its familiar ligands, including the alternative endogenous agonist choline. Of more long-term significance, these peptides also induce upregulation of alpha7-nAChR mRNA and protein expression, as well as enhancing receptor trafficking to the plasma membrane. CONCLUSIONS/SIGNIFICANCE: The results reported here demonstrate a hitherto unknown relationship between the alpha7-nAChR and the non-enzymatic functions of acetylcholinesterase, mediated independently by its C-terminal domain. Such an interaction may prove valuable as a pharmacological tool, prompting new approaches for understanding, and combating, the process of neurodegeneration.
ESTHER : Bond_2009_PLoS.One_4_e4846
PubMedSearch : Bond_2009_PLoS.One_4_e4846
PubMedID: 19287501

Title : Selective enhancement of the activity of C-terminally truncated, but not intact, acetylcholinesterase - Zimmermann_2008_J.Neurochem_104_221
Author(s) : Zimmermann M , Grosgen S , Westwell MS , Greenfield SA
Ref : Journal of Neurochemistry , 104 :221 , 2008
Abstract : Acetylcholinesterase (AChE) is one of the fastest enzymes approaching the catalytic limit of enzyme activity. The enzyme is involved in the terminal breakdown of the neurotransmitter acetylcholine, but non-enzymatic roles have also been described for the entire AChE molecule and its isolated C-terminal sequences. These non-cholinergic functions have been attributed to both the developmental and degenerative situation: the major form of AChE present in these conditions is monomeric. Moreover, AChE has been shown to lose its typical characteristic of substrate inhibition in both development and degeneration. This study characterizes a form of AChE truncated after amino acid 548 (T548-AChE), whose truncation site is homologue to that of a physiological form of T-AChE detected in fetal bovine serum that has lost its C-terminal moiety supposedly due to proteolytic cleavage. Peptide sequences covered by this C-terminal sequence have been shown to be crucially involved in both developmental and degenerative mechanisms in vitro. Numerous studies have addressed the structure-function relationship of the AChE C-terminus with T548-AChE representing one of the most frequently studied forms of truncated AChE. In this study, we provide new insight into the understanding of the functional characteristics that T548-AChE acquires in solution: T548-AChE is incubated with agents of varying net charge and molecular weight. Together with kinetic studies and an analysis of different molecular forms and aggregation states of T548-AChE, we show that the enzymatic activity of T548-AChE, an enzyme verging at its catalytic limit is, nonetheless, apparently enhanced by up to 800%. We demonstrate, first, how the activity of T548-AChE can be enhanced through agents that contain highly positive charged moieties. Moreover, the un-competitive mechanism of activity enhancement most likely involves the peripheral anionic site of AChE that is reflected in delayed substrate inhibition being observed for activity enhanced T548-AChE. The data provides evidence towards a mechanistic and functional link between the form of AChE unique to both development and degeneration and a C-terminal peptide of T-AChE acting under those conditions.
ESTHER : Zimmermann_2008_J.Neurochem_104_221
PubMedSearch : Zimmermann_2008_J.Neurochem_104_221
PubMedID: 17986217

Title : Non-hydrolytic functions of acetylcholinesterase. The significance of C-terminal peptides - Greenfield_2008_FEBS.J_275_604
Author(s) : Greenfield SA , Zimmermann M , Bond CE
Ref : Febs J , 275 :604 , 2008
Abstract : This review explores the possibility that acetylcholinesterase may play a pivotal, non-hydrolytic role in neurodegeneration. More specifically, C-terminal sequences of acetylcholinesterase may act as signalling molecules in key brain regions characteristically vulnerable to Alzheimer's, Parkinson's and motor neuron disease.
ESTHER : Greenfield_2008_FEBS.J_275_604
PubMedSearch : Greenfield_2008_FEBS.J_275_604
PubMedID: 18205834

Title : Multiple cascade effects of oxidative stress on astroglia - Bond_2007_Glia_55_1348
Author(s) : Bond CE , Greenfield SA
Ref : Glia , 55 :1348 , 2007
Abstract : Many neurodegenerative diseases share common underlying features, most prominent of which are dysregulation of calcium homeostasis and reactive astrogliosis, ultimately triggered by oxidative stress. Interestingly, an additional feature of the early response to stress conditions is the upregulation and release of acetylcholinesterase (AChE). This study therefore investigates the link between oxidative stress, calcium influx, gene expression, protein synthesis, and AChE release. We report that, in astroglia and in an immortalized cell line, GH4-halpha7, acute oxidative stress causes influx of extracellular calcium through L-type voltage-gated calcium channels (L-VGCC), followed by increased release of AChE into the extracellular medium. Moreover, rapid and sustained changes in mRNA expression of AChE, L-VGCC, and melastatin-like transient receptor potential 2 (TRPM2) accompany profound suppression of global protein synthesis. Application of L-VGCC blockers selectively reduces stress-induced calcium influx and AChE release, mitigates changes in gene expression, and facilitates recovery from protein synthesis suppression. Although glia exhibit greater sensitivity in their responses, the results are comparable in astroglia and GH4-halpha7 cells, and suggest a generalized and integrated cellular response to stress conditions that characterizes changes observed in neurodegeneration.
ESTHER : Bond_2007_Glia_55_1348
PubMedSearch : Bond_2007_Glia_55_1348
PubMedID: 17654703

Title : An acetylcholinesterase-derived peptide inhibits endocytic membrane activity in a human metastatic breast cancer cell line - Onganer_2006_Biochim.Biophys.Acta_1760_415
Author(s) : Onganer PU , Djamgoz MB , Whyte K , Greenfield SA
Ref : Biochimica & Biophysica Acta , 1760 :415 , 2006
Abstract : Acetylcholinesterase (AChE) is well established as having non-cholinergic functions and is also expressed in breast tumours where its function(s) is not known. Recently, a candidate peptide sequence towards the C-terminal of the AChE molecule has been identified, as the salient site remote from normal catalysis in neurons, and possibly other cells. The main aim of this study was to explore the possibility that 'AChE-peptide' might also affect human breast cancer cells. Uptake of the non-cytotoxic tracer horseradish peroxidase (HRP) was used as an index of endocytosis, a key component of the metastatic cascade, representing exocytosis/secretory membrane activity and/or plasma membrane protein turnover. AChE-peptide had no affect on the weakly metastatic MCF-7 human breast cancer cell line. By contrast, application of AChE-peptide to the strongly metastatic MDA-MB-231 cells resulted in a dose-dependent inhibition of HRP uptake; treatment with a scrambled variant of the peptide of comparable amino acid length was ineffective. The action of AChE-peptide was suppressed by lowering the extracellular Ca2+ concentration and co-applying a selective antagonist of alpha7, but not alpha4/beta2, nicotinic receptor. The results suggest that AChE-peptide has a novel, selective bioactivity on breast cancer cells and can potentiate metastatic cell behaviour.
ESTHER : Onganer_2006_Biochim.Biophys.Acta_1760_415
PubMedSearch : Onganer_2006_Biochim.Biophys.Acta_1760_415
PubMedID: 16469451

Title : Astroglia up-regulate transcription and secretion of 'readthrough' acetylcholinesterase following oxidative stress - Bond_2006_Eur.J.Neurosci_24_381
Author(s) : Bond CE , Patel P , Crouch L , Tetlow N , Day T , Abu-Hayyeh S , Williamson C , Greenfield SA
Ref : European Journal of Neuroscience , 24 :381 , 2006
Abstract : Novel and diverse functions of glial cells are currently the focus of much attention [A. Volterra and J. Meldolesi (2005) Nature Rev. 6, 626-640]. Here we present evidence that rat astroglia release acetylcholinesterase (AChE) as part of their response to hypoxic damage. Exposure of astroglia to tert-butyl hydroperoxide, and hence oxidative stress, subsequently leads to a switching in mRNA from the classical membrane-bound T-AChE to a preferential increase in the splice variant for a soluble form, R-AChE, This change in expression is reflected in increased perinuclear and reduced cytoplasmic AChE staining of the insulted glial cells, with a concomitant and marked increase in extracellular secretion that peaks at 1 h post-treatment. An analogous increase in R-AChE, over a similar time scale, occurs in response to psychological stress [D. Kaufer et al. (1998) Nature 93, 373-377], as well as to head injury and stroke [E. Shohami et al. (1999) J. Neurotrauma 6, 365-76]. The data presented here suggest that glial cells may be key chemical intermediaries in such situations and, perhaps more generally in pathological conditions involving oxidative stress, such as neurodegeneration.
ESTHER : Bond_2006_Eur.J.Neurosci_24_381
PubMedSearch : Bond_2006_Eur.J.Neurosci_24_381
PubMedID: 16903848

Title : Correlation between dopaminergic neurons, acetylcholinesterase and nicotinic acetylcholine receptors containing the alpha3- or alpha5-subunit in the rat substantia nigra - Emmett_2005_J.Chem.Neuroanat_30_34
Author(s) : Emmett SR , Greenfield SA
Ref : Journal of Chemical Neuroanatomy , 30 :34 , 2005
Abstract : The aim of this study was to investigate the relationship between the cells possessing the alpha3 or alpha5 nicotinic acetylcholine receptor subunits and the enzyme acetylcholinesterase, with respect to tyrosine hydroxylase immunoreactive dopaminergic neurons in the rat substantia nigra. Most, but certainly not all, acetylcholinesterase immunoreactive cells were located in the pars compacta. In the substantia nigra pars compacta there were in turn two populations of acetylcholinesterase containing neurons: those that were tyrosine hydroxylase reactive and those that were not. Double label studies, that included an antibody immunoreactive against a common immunogen on alpha1 of muscle and alpha3 and alpha5 neuronal nicotinic acetylcholine receptor subunits, revealed that nearly all nicotinic receptor positive cells were also tyrosine hydroxylase neurons. However, a minority non-tyrosine hydroxylase population was alpha3- and/or alpha5-nAChR positive and these were always AChE-immunoreactive. In summary, there appears to be a close correlation between nicotinic receptors and acetylcholinesterase in the substantia nigra, irrespective of the transmitter phenotype in different neuronal subpopulations.
ESTHER : Emmett_2005_J.Chem.Neuroanat_30_34
PubMedSearch : Emmett_2005_J.Chem.Neuroanat_30_34
PubMedID: 15975762

Title : A peptide derived from acetylcholinesterase is a pivotal signalling molecule in neurodegeneration - Greenfield_2005_Chem.Biol.Interact_157-158_211
Author(s) : Greenfield SA
Ref : Chemico-Biological Interactions , 157-158 :211 , 2005
Abstract : It is now widely accepted that acetylcholinesterase (AChE) also displays non-cholinergic functions, completely independent of cholinergic transmission. Indeed, AChE has been implicated in a variety of trophic and toxic actions in a range of different systems. However, it is still uncertain what part of the AChE molecule may be responsible for these actions, and indeed via what receptor. Recent work has identified a peptide towards the C-terminus of the AChE molecule that appears to have very similar effects to non-cholinergic AChE itself. This action is to enhance calcium entry, in acute and chronic preparations across a trophic-toxic spectrum, depending on concentration applied and/or duration of exposure.
ESTHER : Greenfield_2005_Chem.Biol.Interact_157-158_211
PubMedSearch : Greenfield_2005_Chem.Biol.Interact_157-158_211
PubMedID: 16297900

Title : Poster (44) The role in neurodegeneration of a peptide derived from acetylcholinesterase. -
Author(s) : Greenfield SA
Ref : In: Cholinesterases in the Second Millennium: Biomolecular and Pathological Aspects , (Inestrosa NC, Campos EO) P. Universidad Catolica de Chile-FONDAP Biomedicina :344 , 2004
PubMedID:

Title : Bioactivity of a peptide derived from acetylcholinesterase: involvement of an ivermectin-sensitive site on the alpha 7 nicotinic receptor - Zbarsky_2004_Neurobiol.Dis_16_283
Author(s) : Zbarsky V , Thomas J , Greenfield SA
Ref : Neurobiol Dis , 16 :283 , 2004
Abstract : A peptide fragment of 14 amino acids, derived from the C-terminus of acetylcholinesterase (AChE), might underlie the now well-established noncholinergic effects of the enzyme. This peptide is bioactive in a variety of systems including acute (brain slices) and chronic (organotypic culture) preparations of hippocampus, a pivotal area in Alzheimer's disease (AD); invariably, the action of the peptide is mediated specifically via an as yet unknown receptor. In this study, the allosteric alpha 7 agent, ivermectin (IVM), had a modest inhibitory effect, whilst that of the peptide was significantly more marked. However, ivermectin rendered ineffective the toxicity of high doses of the peptide, that is, when the two were co-applied, only the smaller effects of ivermectin were seen. Ivermectin, therefore, is presumably acting at a site that is identical to, or at least strongly interactive with, the normal binding site for AChE-peptide. This observation could have important implications for eventual therapeutic targeting of the action of AChE-peptide, in neurodegeneration.
ESTHER : Zbarsky_2004_Neurobiol.Dis_16_283
PubMedSearch : Zbarsky_2004_Neurobiol.Dis_16_283
PubMedID: 15207285

Title : A novel peptide modulates alpha7 nicotinic receptor responses: implications for a possible trophic-toxic mechanism within the brain - Greenfield_2004_J.Neurochem_90_325
Author(s) : Greenfield SA , Day T , Mann EO , Bermudez I
Ref : Journal of Neurochemistry , 90 :325 , 2004
Abstract : The alpha7 nicotinic acetylcholine receptor (nAChR) plays a key role in neural development and neurodegeneration. Here, we identify a novel, modulatory receptor ligand, a 14-amino acid peptide (AEFHRWSSYMVHWK) derived from the C-terminus of acetylcholinesterase (AChE). In three different in vitro preparations, this 'AChE-peptide' is bioactive in a ligand-specific and concentration-dependent manner. First, it modulates acutely the effect of acetylcholine (ACh) on Xenopus oocytes transfected with human alpha7, but not alpha4/beta2, nAChR. The action persists when intracellular calcium is chelated with BAPTA or when calcium is substituted with barium ions. This observation suggests that intracellular Ca(2+) signals do not mediate the interaction between the peptide and nAChR, but rather that the interaction is direct: however, the intervention of other mediators cannot be excluded. Secondly, in recordings from the CA1 region in guinea-pig hippocampal slices, AChE-peptide modulates synaptic plasticity in a alpha-bungarotoxin (alpha-BgTx)-sensitive manner. Thirdly, in organotypic cultures of rat hippocampus, long-term exposure to peptide attenuates neurite outgrowth: this chronic, functional effect is selectively blocked by the alpha7 nAChR antagonists, alpha-BgTx and methyllycaconitine, but not by the alpha4/beta2-preferring blocker dihydro-beta-ethroidine. A scrambled peptide variant, and the analogous peptide from butyrylcholinesterase, are ineffective in all three paradigms. The consequences of this novel modulation of the alpha7 nAChR may be activation of a trophic-toxic axis, of relevance to neurodegeneration.
ESTHER : Greenfield_2004_J.Neurochem_90_325
PubMedSearch : Greenfield_2004_J.Neurochem_90_325
PubMedID: 15228589

Title : The role in neurodegeneration of a peptide derived from AChE -
Author(s) : Greenfield SA
Ref : In: Cholinesterases in the Second Millennium: Biomolecular and Pathological Aspects , (Inestrosa NC, Campos EO) P. Universidad Catolica de Chile-FONDAP Biomedicina :127 , 2004
PubMedID:

Title : A peptide derived from the C-terminal region of acetylcholinesterase modulates extracellular concentrations of acetylcholinesterase in the rat substantia nigra - Emmett_2004_Neurosci.Lett_358_210
Author(s) : Emmett SR , Greenfield SA
Ref : Neuroscience Letters , 358 :210 , 2004
Abstract : It is well established that acetylcholinesterase (AChE) has 'non-classical' functions independent of cholinergic transmission. A region of AChE distinct from the catalytic site may be responsible for these actions via a 14-residue peptide located between residues 586-599 at the C-terminus of human AChE. This AChE-peptide possesses a high amino acid sequence homology with a region of amyloid precursor protein and shares many biophysical and physiological characteristics. In this study, the effect of AChE-peptide (AEFHRWSSYMVHWK) on the extracellular levels of endogenous AChE was examined in rat substantia nigra in vitro. A chemiluminescent assay was used to continuously measure the soluble AChE concentration from tissue punches of the substantia nigra. Application of NMDA evoked an increase in extracellular AChE levels consistent with previous results obtained from in vivo models. AChE-peptide, when applied alone, had no effect on AChE release: however, when co-applied with NMDA, AChE-peptide reduced the effectiveness of NMDA to evoke release of AChE. These results indicate, in a region of the brain central to the aetiology of Parkinson's disease, that an AChE-peptide fragment derived from AChE displays a bioactivity that could involve regulation of Ca(2+) availability and hence the release of AChE.
ESTHER : Emmett_2004_Neurosci.Lett_358_210
PubMedSearch : Emmett_2004_Neurosci.Lett_358_210
PubMedID: 15039118

Title : Bioactivity of a peptide derived from acetylcholinesterase in hippocampal organotypic cultures - Day_2004_Exp.Brain.Res_155_500
Author(s) : Day T , Greenfield SA
Ref : Experimental Brain Research , 155 :500 , 2004
Abstract : While the molecular basis underlying the non-classical actions of acetylcholinesterase (AChE) is presently unknown, a candidate peptide sequence located at the C-terminus of AChE (AChE-peptide) has recently been identified. This study explored the bioactivity of synthetic AChE-peptide using in vitro organotypic cultures of rat hippocampus. Neurotrophic effects, detected as increased neurite outgrowth from MAP-immunopositive neurones, were apparent using 1 h exposure to 1-10 nM AChE-peptide. As exposure time increased, cell death occurred as indicated by TdT-mediated dUTP biotin nick-end labelling (TUNEL). This process was accelerated at higher AChE-peptide concentrations, with lactate dehydrogenase (LDH) efflux observed following prolonged exposure to 1-10 microM AChE-peptide. Apoptotic cells were detected by Hoechst 33342 staining following 24 h application of 10 nM AChE-peptide. However, propidium iodide reactivity revealed a simultaneous loss of membrane integrity indicative of necrosis, suggesting that AChE-peptide induces cell death via a continuum of apoptotic and necrotic processes. Prolonged exposure to AChE-peptide also resulted in a concentration-dependent reduction in neurite outgrowth from MAP2-positive neurons, although immunohistochemical studies provided some evidence of differential responsiveness in GABAergic, cholinergic and somatostatin neurones. In addition, bioactivity was sequence specific since a scrambled AChE-peptide analogue, as well as the corresponding BuChE-peptide, was ineffective. In conclusion, the bioactivity associated with the AChE-peptide sequence may account for the non-cholinergic actions of AChE, whilst its neurotrophic-apoptotic-necrotic spectrum of action may be involved in the aetiology of neurodegenerative disorders such as Alzheimer's disease.
ESTHER : Day_2004_Exp.Brain.Res_155_500
PubMedSearch : Day_2004_Exp.Brain.Res_155_500
PubMedID: 14685807

Title : A peptide derived from acetylcholinesterase induces neuronal cell death: characterisation of possible mechanisms - Day_2003_Exp.Brain.Res_153_334
Author(s) : Day T , Greenfield SA
Ref : Experimental Brain Research , 153 :334 , 2003
Abstract : Acetylcholinesterase (AChE) exhibits functions unrelated to the catalysis of acetylcholine (ACh) in particular during development. Although the underlying mechanism(s) is presently unknown, a candidate peptide fragment (AChE-peptide) has recently been identified, and been shown to induce a continuum of apoptotic and necrotic neuronal cell death in rat hippocampal organotypic cultures. The aim of this study was to trace the cell death pathway initiated by AChE-peptide. Using specific antagonists, it was possible to track a series of cellular events following application of 1 nM AChE-peptide: NMDA receptor activation, opening of the L-type voltage gated calcium channel, activation of calcium/calmodulin kinase II, generation of reactive oxygen species and caspase activation. Pharmacological interception at any stage of this cascade blocked the effect of 1 nM AChE-peptide on neurite retraction. Lactate dehydrogenase (LDH) release, a marker for cell lysis, was unaffected by 1 nM AChE-peptide. In contrast, cell death induced by 1 mM AChE-peptide, monitored as neurite retraction and increased LDH efflux, was not offset by any drug treatment. These data suggest that nanomolar concentrations of AChE-peptide exhibit pathophysiological activity via an apoptotic pathway that could play an important role in neuronal development and neurodegeneration.
ESTHER : Day_2003_Exp.Brain.Res_153_334
PubMedSearch : Day_2003_Exp.Brain.Res_153_334
PubMedID: 13680041

Title : Effects of acetylcholinesterase and butyrylcholinesterase on cell survival, neurite outgrowth, and voltage-dependent calcium currents of embryonic ventral mesencephalic neurons - Whyte_2003_Exp.Neurol_184_496
Author(s) : Whyte KA , Greenfield SA
Ref : Experimental Neurology , 184 :496 , 2003
Abstract : The aim of this study was to investigate the effect of butyrylcholinesterase (BuChE) and acetylcholinesterase (AChE) on cell survival, neurite outgrowth and voltage-dependent calcium currents in developing rat ventral mesencephalic (VM) neurons. Both BuChE and AChE have been shown to promote neurite outgrowth in postnatnal preparations. However, the effect of these substances has never been investigated on rat embryonic VM cells, which are used in animal models of foetal transplantation as a treatment for Parkinson's disease. The effects of incubation with BuChE and tetrameric (G(4))- or monomeric (G(1))-AChE on cell survival and neurite outgrowth were characterised over a 7-day period on dopaminergic cells within embryonic VM cultures. The acute effects of these treatments on voltage-dependent calcium currents from embryonic VM cells were then investigated using whole-cell voltage-clamp recordings. The chronic effect of modulating voltage-dependent calcium channels was subsequently explored using the selective calcium channel antagonists omega-agatoxin IVA, omega-conotoxin GVIA, and nifedipine. The results presented here demonstrate firstly trophic effects of BuChE and G(4)- and G(1)-AChE upon dopaminergic neurite outgrowth, secondly that BuChE and G(4)- and G(1)-AChE have an inhibitory effect on voltage-dependent calcium currents, and finally that selective voltage-dependent calcium channel inhibitors also have trophic effects upon dopaminergic neurite outgrowth.
ESTHER : Whyte_2003_Exp.Neurol_184_496
PubMedSearch : Whyte_2003_Exp.Neurol_184_496
PubMedID: 14637119

Title : Bioactivity of a peptide derived from acetylcholinesterase: electrophysiological characterization in guinea-pig hippocampus - Bon_2003_Eur.J.Neurosci_17_1991
Author(s) : Bon CL , Greenfield SA
Ref : European Journal of Neuroscience , 17 :1991 , 2003
Abstract : Acetylcholinesterase is well known to have noncholinergic functions. Only recently, however, has the salient part been identified of the molecule responsible for these nonclassical actions, a peptide of 14 amino acids towards the C-terminus of acetylcholinesterase. The aim of this study was to test the bioactivity of this 'acetylcholinesterase-peptide' using intracellular recordings in guinea-pig hippocampal slices. In the presence of tetrodotoxin, acetylcholinesterase-peptide alone affected neither the membrane potential nor the input resistance of CA1 neurons; however, a modulatory action was observed, as a concentration-dependent decrease of N-methyl-d-aspartic acid-induced depolarization. When calcium potentials were elicited by a depolarizing current pulse, application of acetylcholinesterase-peptide increased or reduced the degree of calcium spike firing in, respectively, the presence or absence of the N-methyl-d-aspartic acid antagonist d(-)-2-amino-5-phosphonopentanoic acid. In contrast, a peptide derived from the equivalent region of butyrylcholinesterase, which also hydrolyses acetylcholine, had no effect. In conclusion, acetylcholinesterase-peptide has a selective bioactivity in the hippocampus; it could thus offer new ways of targeting mechanisms of calcium-induced neurotoxicity.
ESTHER : Bon_2003_Eur.J.Neurosci_17_1991
PubMedSearch : Bon_2003_Eur.J.Neurosci_17_1991
PubMedID: 12752800

Title : A non-cholinergic, trophic action of acetylcholinesterase on hippocampal neurones in vitro: molecular mechanisms - Day_2002_Neurosci_111_649
Author(s) : Day T , Greenfield SA
Ref : Neuroscience , 111 :649 , 2002
Abstract : In this study neurite outgrowth from cultured hippocampal neurones was increased by addition of acetylcholinesterase acting in a non-cholinergic manner. Only monomeric acetylcholinesterase, a form of acetylcholinesterase dominant in development, increased neurite outgrowth (3-10 U/ml); moreover this effect was not blocked by active site blockers (echothiophate and galanthamine) but was sensitive to the addition of peripheral site blockers (fasciculin and BW284c51). It appears therefore that acetylcholinesterase has alternative, non-cholinergic functions, one of which could be in development, via a peripheral site. The possibility of a causal relationship between neurite outgrowth and calcium influx was explored using a spectrum of acetylcholinesterase variants, inhibitors and calcium channel blockers. Acetylcholinesterase regulation of outgrowth was shown to depend on an influx of extracellular calcium specifically via the L-type voltage-gated calcium channel. In summary, we propose that, independent of its catalytic activity, a selective form of acetylcholinesterase has a role in the development of hippocampal neurones via a selective voltage-gated calcium channel.
ESTHER : Day_2002_Neurosci_111_649
PubMedSearch : Day_2002_Neurosci_111_649
PubMedID: 12031351

Title : Parkinson's disease, Alzheimer's disease and motor neurone disease: identifying a common mechanism - Greenfield_2002_Neurosci_113_485
Author(s) : Greenfield SA , Vaux DJ
Ref : Neuroscience , 113 :485 , 2002
Abstract : Although Alzheimer's disease, Parkinson's disease, and motor neurone disease are distinct disorders, there could be a common neurodegenerative mechanism that characterises the death of selective neurone populations in each case. We propose that this mechanism could be an aberrantly activated, developmental process involving a non-classical, non-enzymatic action of acetylcholinesterase mediated via a short linear motif near the C-terminal end of the molecule. Since this motif has a highly conserved homology with part of the amyloid precursor protein, it may be particularly attractive as a target for novel therapeutic strategies in neurodegeneration.
ESTHER : Greenfield_2002_Neurosci_113_485
PubMedSearch : Greenfield_2002_Neurosci_113_485
PubMedID: 12150769

Title : Rat locomotion and release of acetylcholinesterase - Heiland_1999_Pharmacol.Biochem.Behav_62_81
Author(s) : Heiland B , Greenfield SA
Ref : Pharmacol Biochem Behav , 62 :81 , 1999
Abstract : In the substantia nigra acetylcholinesterase is released from the dopamine cells of the pars compacta independent of cholinergic transmission. In this study the effects of local and systemic amphetamine treatment were compared on acetylcholinesterase release in the rat substantia nigra in relation to concomitant behavior. Acetylcholinesterase release, measured "on-line" with a sensitive chemiluminescent system, was enhanced by amphetamine stimulation administered locally and could not be dissociated from simultaneous amphetamine-induced circling behavior. On the other hand, amphetamine administered systemically resulted in a general increase in locomotor behavior followed by a subsequent increase in acetylcholinesterase release. The alternative scenario of an initial rise in acetylcholinesterase release, subsequently followed by enhanced movement, was never seen. Hence, movement can enhance release of acetylcholinesterase from the substantia nigra, whereas "upstream" local nigral events can affect acetylcholinesterase release and movement simultaneously.
ESTHER : Heiland_1999_Pharmacol.Biochem.Behav_62_81
PubMedSearch : Heiland_1999_Pharmacol.Biochem.Behav_62_81
PubMedID: 9972849

Title : Non-Cholinergic Actions of Acetylcholinesterase in the Substantia Nigra -
Author(s) : Greenfield SA
Ref : In: Structure and Function of Cholinesterases and Related Proteins - Proceedings of Sixth International Meeting on Cholinesterases , (Doctor, B.P., Taylor, P., Quinn, D.M., Rotundo, R.L., Gentry, M.K. Eds) Plenum Publishing Corp. :557 , 1998
PubMedID:

Title : Non-cholinergic, trophic action of recombinant acetylcholinesterase on mid-brain dopaminergic neurons - Holmes_1997_J.Neurosci.Res_49_207
Author(s) : Holmes C , Jones SA , Budd TC , Greenfield SA
Ref : Journal of Neuroscience Research , 49 :207 , 1997
Abstract : Acetylcholinesterase (AChE) is secreted from various brain regions such as the substantia nigra, where levels of this molecule are disproportionately higher than those of choline acetyltransferase. It is thus possible that AChE may have alternative, non-cholinergic functions, one of which could be in development. Indeed, several recent studies have already demonstrated a neurotrophic action of AChE independent of hydrolysis of acetylcholine. In the developing nervous system the dominant forms of AChE differ from the tetramers (G4) that prevail in maturity, in that they are lower molecular weight monomers (G1) and dimers (G2). Therefore, the aims of this study were to explore the neurotrophic role of AChE by comparing the effects of mouse recombinant G1 and G4 AChE on the survival and development of mid-brain tyrosine hydroxylase immunoreactive neurons. Butyrylcholinesterase (BuChE), which also hydrolyses acetylcholine, and basic fibroblast growth factor (bFGF), an established trophic factor for midbrain neurons, were also tested. bFGF had no significant stimulatory effect: moreover, BuChE was also inefficacious, suggesting that the action of AChE was independent of its catalytic site. In contrast, mouse recombinant G1 and G4 AChE both increased the survival as well as the outgrowth of the cultured neurons. However, G1 AChE was more potent than G4 AChE suggesting that developmental forms of AChE exist. The implications of this finding for physiological and pathological functioning of the nervous system are discussed.
ESTHER : Holmes_1997_J.Neurosci.Res_49_207
PubMedSearch : Holmes_1997_J.Neurosci.Res_49_207
PubMedID: 9272643

Title : Characteristics of electrically evoked somatodendritic dopamine release in substantia nigra and ventral tegmental area in vitro - Rice_1997_J.Neurophysiol_77_853
Author(s) : Rice ME , Cragg SJ , Greenfield SA
Ref : Journal of Neurophysiology , 77 :853 , 1997
Abstract : Somatodendritic dopamine (DA) release from neurons of the midbrain represents a nonclassical form of neuronal signaling. We assessed characteristics of DA release during electrical stimulation of the substantia nigra pars compacta (SNc) in guinea pig midbrain slices. With the use of parameters optimized for this region, we compared stimulus-induced increases in extracellular DA concentration ([DA]o) in medial and lateral SNc, ventral tegmental area (VTA), and dorsal striatum in vitro. DA release was monitored directly with carbon-fiber microelectrodes and fast-scan cyclic voltammetry. Detection of DA in SNc was confirmed by electrochemical, pharmacological, and anatomic criteria. Voltammograms of the released substance had the same peak potentials as those of DA obtained during in vitro calibration, but different from those of the indoleamine 5-hydroxytryptamine. Similar voltammograms were also obtained in the DA-rich striatum during local electrical stimulation. Contribution from the DA metabolite 3,4-dihydroxyphenylacetic acid to somatodendritic release was negligible, as indicated by the lack of effect of the monoamine oxidase inhibitor pargyline (20 microM) on the signal. Lastly, DA voltammograms could only be elicited in regions that were subsequently determined to be positive for tyrosine hydroxylase immunoreactivity (TH-ir). The frequency dependence of stimulated DA release in SNc was determined over a range of 1-50 Hz, with a constant duration of 10 s. Release was frequency dependent up to 10 Hz, with no further increase at higher frequencies. Stimulation at 10 Hz was used in all subsequent experiments. With this paradigm, DA release in SNc was tetrodotoxin insensitive, but strongly Ca2+ dependent. Stimulated [DA]o in the midbrain was also site specific. At the midcaudal level examined, DA efflux was significantly greater in VTA (1.04 +/- 0.05 microM, mean +/- SE) than in medial SNc (0.52 +/- 0.05 microM), which in turn was higher than in lateral SNc (0.35 +/- 0.03 microM). This pattern followed the apparent density of TH-ir, which was also VTA > medial SNc > lateral SNc. This report has introduced a new paradigm for the study of somatodendritic DA release. Voltammetric recording with electrodes of 2-4 microns tip diameter permitted highly localized, direct detection of endogenous DA. The Ca2+ dependence of stimulated release indicated that the process was physiologically relevant. Moreover, the findings that somatodendritic release was frequency dependent across a range characteristic of DA cell firing rates and that stimulated [DA]o varied markedly among DA cell body regions have important implications for how dendritically released DA may function in the physiology and pathophysiology of substantia nigra and VTA.
ESTHER : Rice_1997_J.Neurophysiol_77_853
PubMedSearch : Rice_1997_J.Neurophysiol_77_853
PubMedID: 9065854

Title : Non-classical actions of cholinesterases: role in cellular differentiation, tumorigenesis and Alzheimer's disease. -
Author(s) : Greenfield SA
Ref : Neurochem Int , 28 :485 , 1996
PubMedID: 8792328

Title : Involvement of the NMDA receptor in a non-cholinergic action of acetylcholinesterase in guinea-pig substantia nigra pars compacta neurons - Webb_1996_Eur.J.Neurosci_8_837
Author(s) : Webb CP , Nedergaard S , Giles K , Greenfield SA
Ref : European Journal of Neuroscience , 8 :837 , 1996
Abstract : Evidence is accumulating that a soluble, secretory form of acetylcholinesterase may have novel, non-cholinergic functions in certain brain regions, such as the substantia nigra. In this study, application of human recombinant acetylcholinesterase (rhAChE) to pars compacta neurons in the rostral substantia nigra resulted in a sustained hyperpolarization that was not only mimicked by application of N-methyl-D-aspartate (NMDA) but also blocked by the NMDA receptor antagonists MK8O1 and 2-amino-5-phosphonopentanoic acid. Neither the rhAChE- nor the NMDA-induced hyperpolarization was seen when the calcium chelator BAPTA was injected into the neuron; hence the effect is mediated by accumulation of intracellular calcium. This intracellular calcium appears sufficient to compromise neuronal metabolism since the rhAChE-induced hyperpolarization was reversed by application of the K-ATP channel antagonist tolbutamide. Butyrylcholinesterase, a protein of similar molecular weight to acetylcholinesterase, which also hydrolyses acetylcholine, had no effect whatsoever. The results suggest that, independent of its normal catalytic function, acetylcholinesterase can act via the NMDA receptor complex to enhance calcium entry into nigral neurons and jeopardize cell metabolism. This non-classical action of acetylcholinesterase might thus be an important factor in the mechanisms underlying parkinsonian neurodegeneration.
ESTHER : Webb_1996_Eur.J.Neurosci_8_837
PubMedSearch : Webb_1996_Eur.J.Neurosci_8_837
PubMedID: 9081636

Title : Acetylcholinesterase-induced respiratory burst in macrophages: evidence for the involvement of the macrophage mannose-fucose receptor - Klegeris_1996_Biochim.Biophys.Acta_1289_159
Author(s) : Klegeris A , Budd TC , Greenfield SA
Ref : Biochimica & Biophysica Acta , 1289 :159 , 1996
Abstract : It has long been suggested that acetylcholinesterase is capable of functioning in a non-cholinergic manner. However, very little is known about the molecular structures which mediate the interaction between this protein and the cellular membrane. Previously it was demonstrated that acetylcholinesterase interacted in a carbohydrate-specific manner with peritoneal macrophages and induced the 'respiratory burst' [1]. This study aimed to establish whether a carbohydrate-binding site exists on the acetylcholinesterase molecule itself, or alternatively, whether the macrophage carbohydrate-binding receptor is involved. No carbohydrate binding properties intrinsic to acetylcholinesterase were detected using affinity chromatography with immobilised monosaccharides, erythrocyte agglutination and gel-diffusion techniques. The interaction between acetylcholinesterase and several monosaccharide columns observed in this study appeared to be due to ionic interactions. Moreover, it was shown that a specific inhibitor of the enzymatic activity of AChE, BW284C51, could inhibit the peritoneal cell response not only to acetylcholinesterase, but also to several other stimuli, thus exhibiting a non-specific effect on macrophages. However, the inhibitory effects of specific ligands of the macrophage mannose-fucose receptor and the inability of non-glycosylated acetylcholinesterase to interact with macrophages suggested that the effect of acetylcholinesterase on peritoneal cells is most probably mediated by the macrophage mannose-fucose receptor. The role of the mannose-fucose receptor in triggering the respiratory burst response was supported by the fact that several ligands of these receptors were capable of inducing the functional response of macrophages.
ESTHER : Klegeris_1996_Biochim.Biophys.Acta_1289_159
PubMedSearch : Klegeris_1996_Biochim.Biophys.Acta_1289_159
PubMedID: 8605227

Title : Comparison of the behavioural effects of infusion of carbachol and acetylcholinesterase into the rat substantia nigra - Hawkins_1996_Pharmacol.Biochem.Behav_55_67
Author(s) : Hawkins CA , Greenfield SA
Ref : Pharmacology, Biochemistry & Behavior , 55 :67 , 1996
Abstract : It has been postulated for many years that acetylcholinesterase (AChE) may play a nonclassical role in the substantia nigra, unrelated to its ability to hydrolyse acetylcholine. In this study the behavioural effects of unilateral infusion of AChE and a cholinergic agonist, carbachol, were compared. Carbachol induced ipsiversive circling over a very short time scale (minutes), whereas AChE induced contraversive circling, but over a longer time course-10 days. Both agents showed selectivity of response within the substantia nigra: acetylcholinesterase was only effective when infused into the most rostral region of the substantia nigra and its effects were limited to the pars compacta. In contrast, carbachol had effects in both the pars compacta and reticulata, with a graded sensitivity to carbachol in the rostral/caudal plane; infusions into rostral regions induced high rates of circling compared to more caudal areas, suggesting that the cholinergic input to the substantia nigra is not homogenous, but greater in rostral regions. This disparity between the effects of carbachol and AChE would, therefore, suggest that AChE is not exerting its long-term behavioural actions via a cholinergic mechanism, both in terms of time course of the response and the areas within the substantia nigra sensitive to these agents.
ESTHER : Hawkins_1996_Pharmacol.Biochem.Behav_55_67
PubMedSearch : Hawkins_1996_Pharmacol.Biochem.Behav_55_67
PubMedID: 8870040

Title : Inhibition of the ATP-sensitive potassium channel in the guinea pig substantia nigra by BMS 181100 is not mediated by a sigma-binding site - O'Callaghan_1995_J.Neurosci.Res_42_85
Author(s) : O'Callaghan JF , Greenfield SA
Ref : Journal of Neuroscience Research , 42 :85 , 1995
Abstract : Quantitative autoradiography of brain tissue has revealed a high density of binding sites for the K-ATP channel antagonists, the sulphonylureas, and for sigma-ligands in the substantia nigra (SN). In view of the high density of the two binding sites in the SN the possibility has been investigated that the K-ATP channel and the sigma-binding site are functionally linked. The K-ATP channel-mediated membrane hyperpolarisation and decrease in input resistance produced by hypoxia and by the metabolic inhibitor, cyanide, in rostral substantia nigra pars compacta neurons are antagonised by the sigma-ligand BMS 181100. In addition, BMS 181100 antagonises activation of the K-ATP channel by diazoxide; cromakalim is found to be without effect in these neurons. Antagonism of the cyanide-induced hyperpolarisation is dose dependent and is observed at concentrations of the drug which have no observable effect on the resting membrane properties of the neurons. By contrast, the nonselective sigma ligands 1,3-di-O-tolylguanidine (10 microM) and (+)-3-(3-hydroxyphenyl)-N-(1-propyl)piperidine (100 microM), and the selective sigma 1-ligand (+)-pentazocine (5-10 microM) have no effect on the cyanide-induced hyperpolarisation. 5-HT (50-100 microM) and the selective 5-HT1A receptor agonist 8-OH-DPAT (50 microM) also fail to antagonise the cyanide-induced hyperpolarisation. The antagonism of the cyanide-induced hyperpolarisation by BMS 181100 persists in the presence of tetrodotoxin (1 microM) and in the presence of high concentrations of (+)-3-(3-hydroxyphenyl)-N-(1-propyl)piperidine, but not under conditions of reduced calcium (0.1-0.2 mM) and raised magnesium (6 mM) concentrations, which block synaptic transmission. It is concluded that in substantia nigra phasic neurons the sigma-binding site does not regulate activation of the ATP-sensitive channel. However, BMS 181100 antagonises K-ATP channel activation in these neurons independently of sigma-binding sites and 5-HT receptors. This action of BMS 181100 is TTX insensitive and Ca2+ dependent.
ESTHER : O'Callaghan_1995_J.Neurosci.Res_42_85
PubMedSearch : O'Callaghan_1995_J.Neurosci.Res_42_85
PubMedID: 8531229

Title : Possible intermixing of neurons from the subthalamic nucleus and substantia nigra pars compacta in the guinea-pig - Overton_1995_Exp.Brain.Res_107_151
Author(s) : Overton PG , O'Callaghan JF , Greenfield SA
Ref : Experimental Brain Research , 107 :151 , 1995
Abstract : A population of cells in the anterior substantia nigra pars compacta (SNPc) of the guinea-pig have been reported previously that differ from classical dopaminergic neurons in terms of their active and passive membrane properties. To investigate this population further, anterior nigral neurons (n = 17) were compared with neurons in the adjacent subthalamic nucleus (STN: n = 26). The anterior nigral neurons were found to be indistinguishable from STN neurons in their action potential characteristics, firing rate, resting membrane potential and input resistance. A low-threshold calcium conductance and anomalous rectification could be demonstrated in cells from both groups. Furthermore, the gross morphological characteristics of anterior nigral neurons and STN neurons were very similar, as assessed following the intracellular injection of biocytin. A further similarity was seen in the response of the two cell groups to cyanide (200 microM) and apomorphine (500 microM). Cyanide hyperpolarised the membrane potential of all STN neurons and the majority (77.8%) of anterior nigral neurons, in both cases producing a concomitant reduction in firing rate. These changes were accompanied by an increase in membrane conductance for potassium ions. Apomorphine depolarised the membrane potential of all STN neurons and anterior nigral neurons, in most cases increasing the input resistance (83.3% of STN neurons and 100% of anterior nigral neurons). In both groups of cells, when firing rate was affected, an increase was usually seen. Given the physiological, morphological and pharmacological similarities of STN and anterior nigral neurons, the most parsimonious interpretation is that the anterior nigral neurons belong to the STN. However, the anterior nigral neurons were found in slices that, when resectioned, contained tyrosine hydroxylase (TH)-immunoreactive cell bodies in every section, in a location corresponding to the SNPc. The implication is that in the guinea pig the SNPc and STN (usually considered to be anatomically distinct nuclei) intermix at this level for several hundred microns. This close association of the STN and the compacta was further demonstrated by the presence of TH-positive varicose and non-varicose neuronal processes within the STN.
ESTHER : Overton_1995_Exp.Brain.Res_107_151
PubMedSearch : Overton_1995_Exp.Brain.Res_107_151
PubMedID: 8773236

Title : The effect of acetylcholinesterase on outgrowth of dopaminergic neurons in organotypic slice culture of rat mid-brain - Jones_1995_Cell.Tiss.Res_279_323
Author(s) : Jones SA , Holmes C , Budd TC , Greenfield SA
Ref : Cell & Tissue Research , 279 :323 , 1995
Abstract : This study has investigated the possibility that acetylcholinesterase could play a non-classical role as an adhesion factor or growth factor in the development of dopaminergic neurons in organotypic slice culture of postnatal day 1 rats. When the culture medium was supplemented with acetylcholinesterase (3 U/ml), outgrowth of tyrosine hydroxylase-immunoreactive neurites was significantly enhanced. Addition of a specific inhibitor of acetylcholinesterase, BW284c51, caused a decrease in the number of tyrosine hydroxylase neurons and a reduction in the cell body size and extent of neurite outgrowth of remaining neurons. However, echothiophate which also inhibits AChE activity, did not produce these effects. Therefore acetylcholinesterase could act as a growth enhancing factor for dopaminergic neurons, and disruption of an as yet unidentified site on the acetylcholinesterase molecule by BW284c51 could decrease the survival and outgrowth of these neurons.
ESTHER : Jones_1995_Cell.Tiss.Res_279_323
PubMedSearch : Jones_1995_Cell.Tiss.Res_279_323
PubMedID: 7895271

Title : A possible interaction between acetylcholinesterase and dopamine molecules during autoxidation of the amine - Klegeris_1995_Free.Rad.Biol.Med_18_223
Author(s) : Klegeris A , Korkina LG , Greenfield SA
Ref : Free Radic Biol Med , 18 :223 , 1995
Abstract : Acetylcholinesterase has an action in the central nervous system, independent of hydrolysis of acetylcholine. This study explored the possible interaction between the two molecules: the effects of acetylcholinesterase on the autoxidation of the catecholamine were tested, and, in turn, modification of the catalytic activity of the enzyme by products of dopamine oxidation were studied. Acetylcholinesterase selectively inhibited the speed of quinone production from dopamine as well as accumulation of hydrogen peroxide, whilst the rate of generation of superoxide was increased. Analysis of absorption spectra revealed the formation of a new product, which appeared after mixing acetylcholinesterase and dopamine in neutral pH. In all cases, butyrylcholinesterase was ineffective. Incubation of acetylcholinesterase in the presence of dopamine resulted in a significant decrease in the catalytic activity of the enzyme. The effects of application of preparations modifying autoxidation of dopamine (SOD, catalase, peroxidase) suggested that inactivation of the enzyme occurred as a result of the direct interaction of a quinone and/or semiquinone oxidation product with enzyme, as opposed to any effects of reactive oxygen species. Because acetylcholinesterase and dopamine are co-released from the neurons degenerating in Parkinson's disease, a direct chemical interaction between these two molecules could have significance both for the normal functioning of the substantia nigra and for related pathological states.
ESTHER : Klegeris_1995_Free.Rad.Biol.Med_18_223
PubMedSearch : Klegeris_1995_Free.Rad.Biol.Med_18_223
PubMedID: 7744305

Title : Uptake of acetylcholinesterase by neurons in the substantia nigra - Dickie_1995_Eur.J.Neurosci_7_351
Author(s) : Dickie BG , Budd TC , Vaux D , Greenfield SA
Ref : European Journal of Neuroscience , 7 :351 , 1995
Abstract : It is known that acetylcholinesterase is secreted by the dopaminergic neurons of the substantia nigra and has a subsequent action independent of cholinergic transmission. Although non-cholinergic actions of this protein have been demonstrated, the subsequent fate of acetylcholinesterase is unknown. One possibility is that acetylcholinesterase is taken up following secretion into the extracellular space. This hypothesis has been tested in vivo, in both conscious and anaesthetized guinea-pigs. Exogenous acetylcholinesterase (2-20 pM) was infused via a push-pull cannula implanted into either the substantia nigra or the surrounding extranigral regions: the amount subsequently recovered in the perfusate was then compared with control values. Only when the push-pull cannulae were implanted in the substantia nigra was there a marked decrease in the amount of acetylcholinesterase recovered; this selective retention was abolished when the perfusion medium was cooled to 4 degrees C or when the experiment was performed post mortem. Direct visualization of immunocytochemically identified nigral dopaminergic cells revealed co-localized deposits of labelled, exogenous acetylcholinesterase. Moreover, when exogenous acetylcholinesterase was boiled to prevent detection by the assay system and to eliminate any classical enzymatic action, an enhancement in perfusate levels of endogenous acetylcholinesterase was observed from nigral but not from extranigral sites, indicating that endogenous and exogenous acetylcholinesterases were in competition. These results suggest that, within the substantia nigra, secreted acetylcholinesterase may be subject to a temperature- and energy-dependent uptake mechanism.
ESTHER : Dickie_1995_Eur.J.Neurosci_7_351
PubMedSearch : Dickie_1995_Eur.J.Neurosci_7_351
PubMedID: 7773434

Title : Release of acetylcholinesterase from guinea-pig substantia nigra: effects of tryptaminergic drugs and dorsal raphe nucleus stimulation - Dickie_1995_Neuropharmacol_34_1191
Author(s) : Dickie BG , Greenfield SA
Ref : Neuropharmacology , 34 :1191 , 1995
Abstract : The guinea-pig substantia nigra receives a 5-hydroxytryptaminergic (5-HT ergic) projection from the dorsal raph nucleus. In this study we have attempted to identify the 5-HT receptor subtype mediating release of acetylcholinesterase (AChE) from nigral neurones, measured by assay of perfusate obtained via chronically implanted push-pull cannulae. The effects of direct nigral application of 5-HT, 2-methyl-5-HT and 5-methoxytryptamine. Application of submicromolar concentrations of 5-HT, 2,5,-dimethoxy-4- iodoamphetamine and alpha-methyl-5-HT significantly enhanced release of AChE, whereas 5-carboxamidotryptamine, sumatriptan, 2-methyl-5-HT and 5-methoxytryptamine were ineffective at a similar concentration range. Electrical stimulation (50 Hz, 20-300 mu A) of the dorsal raph nucleus evoked release of AChE from the substantia nigra, and induced a rotational behavioural effect for the duration of stimulation. Pretreatment with 5,7,-dihydroxytryptamine inhibited both DRN-evoked release of AChE and animal rotation. The 5-HT receptor antagonists ketanserin and ritanserin (10(-7)-10(-6)M, when applied to the substantia nigra, inhibited raph-stimulated AChE release. Drugs which inhibited raph-stimulated release of AChE had no effect on concomitant animal rotation, indicating that the behavioural events are mediated via distinct processes, unrelated to those mediating nigral AChE release. The data suggest that evoked release of AChE from the substantia nigra by stimulation of the dorsal raph nucleus may be mediated in part via a 5-HT2 receptor type. The 5-HT1D agonists 5-carboxamidotryptamine (10(-6)M and sumatriptan (10(-5)M also inhibited raph-evoked AChE release, suggesting a possible presynaptic autoinhibitory role for 5-HT1D receptors on raph-nigral nerve terminals.
ESTHER : Dickie_1995_Neuropharmacol_34_1191
PubMedSearch : Dickie_1995_Neuropharmacol_34_1191
PubMedID: 8532190

Title : A Non-Cholinergic Function for Acetylcholinesterase -
Author(s) : Greenfield SA
Ref : In Enzyme of the Cholinesterase Family - Proceedings of Fifth International Meeting on Cholinesterases , (Quinn, D.M., Balasubramanian, A.S., Doctor, B.P., Taylor, P., Eds) Plenum Publishing Corp. :415 , 1995
PubMedID:

Title : Recombinant acetylcholinesterase has behavioural effects in the rat substantia nigra not attributable to its enzymatic activity - Hawkins_1995_Neurosci.Lett_197_203
Author(s) : Hawkins CA , Greenfield SA
Ref : Neuroscience Letters , 197 :203 , 1995
Abstract : An unexplained action of acetylcholinesterase (AChE) has previously been demonstrated on motor behaviour in the substantia nigra: a single infusion of the protein induced long-term circling behaviour, reflecting sustained increased activity of the nigro-striatal pathway. In this study, a highly purified form of AChE was infused and the long-term behavioural effects were still observed. In addition, recombinant human AChE produced a similar response, suggesting that AChE itself, and not a contaminant, was responsible for these behavioural actions. Butyrylcholinesterase, which also hydrolyses acetylcholine, was without effect. Hence AChE is not exerting these actions by potentiating the neurotransmitter acetylcholine, but via some cholinergic-independent mechanism.
ESTHER : Hawkins_1995_Neurosci.Lett_197_203
PubMedSearch : Hawkins_1995_Neurosci.Lett_197_203
PubMedID: 8552299

Title : Evidence for a Putative Acetylcholinesterase Uptake Mechanism within the Substantia Nigra -
Author(s) : Budd TC , Dickie BG , Vaux D , Greenfield SA
Ref : In Enzyme of the Cholinesterase Family - Proceedings of Fifth International Meeting on Cholinesterases , (Quinn, D.M., Balasubramanian, A.S., Doctor, B.P., Taylor, P., Eds) Plenum Publishing Corp. :443 , 1995
PubMedID:

Title : Activation of Peritoneal Macrophages by Acetylcholinesterase is Independent of Catalytic Activity -
Author(s) : Klegeris A , Budd TC , Greenfield SA
Ref : In Enzyme of the Cholinesterase Family - Proceedings of Fifth International Meeting on Cholinesterases , (Quinn, D.M., Balasubramanian, A.S., Doctor, B.P., Taylor, P., Eds) Plenum Publishing Corp. :445 , 1995
PubMedID:

Title : The release of acetylcholinesterase in vivo is regulated by dopaminergic systems in the guinea-pig substantia nigra - Dally_1994_Neurochem.Int_25_339
Author(s) : Dally JJ , Greenfield SA
Ref : Neurochem Int , 25 :339 , 1994
Abstract : Acetylcholinesterase (AChE) and dopamine are both stored and released from dendrites within the substantia nigra: however, it is as yet unknown whether the regulation of these two purported neuromodulators is in any way related. Using a sensitive chemiluminescent system to monitor AChE release 'on-line', the effects of inhibiting synthesis and storage of dopamine with alpha-methyl-p-tyrosine (AMPT: 250 mg/kg, i.p.) and reserpine (6 mg/kg, i.p.), respectively, have been studied. Both these agents significantly reduced nigral tissue dopamine levels by decreases of 83% and 63%, respectively; however, only AMPT had a significant effect in vivo on the spontaneous release of AChE compared to conscious control animals (66% decrease). Co-application of both AMPT and reserpine resulted in a significant decrease in the tissue dopamine content (95%) and in spontaneous release of AChE compared to conscious control guinea-pigs (72%); however, these effects were not significantly different from when AMPT was employed alone. Application of potassium ions (60 mM) or veratridine (100 microM) both evoked release of AChE in control animals: however, when expressed as a percentage of basal levels, this increase in release was not influenced by drug treatment or state of consciousness. These results suggest that de novo dopamine synthesis may at least in part, have an influential effect on release (and possibly storage) of AChE in the substantia nigra.
ESTHER : Dally_1994_Neurochem.Int_25_339
PubMedSearch : Dally_1994_Neurochem.Int_25_339
PubMedID: 7820067

Title : The subthalamo-nigral pathway regulates movement and concomitant acetylcholinesterase release from the substantia nigra - Jones_1994_J.Neur.Transm_98_23
Author(s) : Jones SA , Dickie BG , Klegeris A , Greenfield SA
Ref : Journal of Neural Transmission General Section , 98 :23 , 1994
Abstract : Within the substantia nigra acetylcholinesterase is released independently of cholinergic transmission: this release could be related to some aspects of motor control. To investigate this possibility, acetylcholinesterase release was continuously monitored in relation to specific movements evoked by central electrical stimulation. Increased intensities of stimulation of the subthalamic nucleus in awake guinea-pigs produced a behavioural response, ranging from a decrease in spontaneous movement, to chewing, to both chewing and circling movements. Enhancement of acetylcholinesterase release occurred only when large scale movements (circling as well as chewing) were evoked by subthalamic stimulation: however, a similar protocol of stimulation during ketamine-induced anaesthesia did not produce any comparable movements nor any concomitant change in the release of acetylcholinesterase. Perfusion of the glutamate agonist N-methyl-D-aspartate (NMDA) into the substantia nigra also induced an increase in release of acetylcholinesterase from the substantia nigra of conscious animals, whereas (S)-alpha-amino-3-hydroxy-5-methylisoxazole-4-proprionic acid (AMPA) did not significantly enhance acetylcholinesterase levels. It is concluded that AChE release in the substantia nigra can occur as a result of activation of glutamatergic subthalamic afferents, and that this activation may also be associated with changes in movement.
ESTHER : Jones_1994_J.Neur.Transm_98_23
PubMedSearch : Jones_1994_J.Neur.Transm_98_23
PubMedID: 7536013

Title : Raphe nucleus-evoked release of acetylcholinesterase from guinea-pig substantia nigra - Dickie_1994_Neuroreport_5_769
Author(s) : Dickie BG , Greenfield SA
Ref : Neuroreport , 5 :769 , 1994
Abstract : Acetylcholinesterase (AChE) is released from dopaminergic dendrites in the guinea-pig substantia nigra. This release, measured by a chemiluminescent assay, is increased following electrical stimulation of the dorsal raph nucleus, which sends a 5-hydroxytryptaminergic input to the substantia nigra. Application of exogenous 5-hydroxytryptamine (5-HT) directly to the substantia nigra similarly enhanced release of AChE, whilst local application of cinanserin, a 5-HT antagonist, inhibited electrically-evoked release. Although the substantia nigra posseses a dense localization of 5-HT1D receptors, application of the 5-HT1D agonist sumatriptan did not effect AChE release. The results indicate that 5-HT, released from raph-nigral afferent nerves, enhances the dendritic release of AChE, although this effect is unlikely to be mediated via 5-HT1D receptors.
ESTHER : Dickie_1994_Neuroreport_5_769
PubMedSearch : Dickie_1994_Neuroreport_5_769
PubMedID: 8018847

Title : Acetylcholinesterase activation of peritoneal macrophages is independent of catalytic activity - Klegeris_1994_Cell.Mol.Neurobiol_14_89
Author(s) : Klegeris A , Budd TC , Greenfield SA
Ref : Cellular Molecular Neurobiology , 14 :89 , 1994
Abstract : 1. In diverse tissues, acetylcholinesterase appears to play a critical role in the functional state of cells completely dependent of cholinergic transmission. However, very little is known about the mechanisms and actual molecular structures mediating the fundamental interactions between this protein and the cellular membrane. 2. In this study, peritoneal macrophages were used as a model system to study the possible interaction between acetylcholinesterase, acting in a non-cholinergic capacity, and the cellular membrane. 3. When acetylcholinesterase was incubated with macrophages harvested from rat peritoneum, the rate of oxygen consumption was increased in a concentration-dependent manner that was independent of mitochondrial block with sodium cyanide. Furthermore, heat inactivation of enzymatic activity or application of BW 284C51 at a concentration which totally blocks catalytic activity did not eliminate the effect. 4. In contrast, incubation with bovine serum albumin or butyrylcholinesterase actually retarded oxygen consumption. 5. The effect of acetylcholinesterase depended on the presence of divalent cations and was inhibited by mannan and D-mannose, but not D-galactose. It is concluded that acetylcholinesterase can induce a "respiratory burst" in macrophages independent of its conventional catalytic site but involving either the mannose receptor of the monocyte-derived macrophage or a possible sugar binding site on acetylcholinesterase itself.
ESTHER : Klegeris_1994_Cell.Mol.Neurobiol_14_89
PubMedSearch : Klegeris_1994_Cell.Mol.Neurobiol_14_89
PubMedID: 7954662

Title : Differential cholinergic and non-cholinergic actions of acetylcholinesterase in the substantia nigra revealed by fasciculin- induced inhibition - Dajas_1993_Brain.Res_616_1
Author(s) : Dajas F , Silveira R , Costa G , Castello ME , Jerusalinsky D , Medina J , Levesque D , Greenfield SA
Ref : Brain Research , 616 :1 , 1993
Abstract : The effects of the peptide fasciculin (FAS), a potent inhibitor of acetylcholinesterase (AChE) have been examined, following unilateral microinfusion, on tissue levels of monoamines in the rat substantia nigra and concomitant circling behaviour. Although FAS inhibited 87% of total AChE, the levels of dopamine and its metabolites remained unchanged. Furthermore, the treatment induced modest contraversive rotation which was markedly enhanced in the presence of a systemic challenge with apomorphine. This behavioural effect of FAS was partially reversed by systemically administered atropine. Any possible interaction of FAS with nigral dopamine systems was further investigated by testing the peptide in animals that five days earlier had undergone a 6-hydroxydopamine (6-OHDA) lesion of the SN such that dopamine and AChE were significantly but not completely reduced. In a majority of these animals, FAS treatment caused a reversal of the lesion induced ipsiversive rotation, ie restored contraversive rotation. It is concluded that in the SN, FAS can have biochemical and behavioural actions independent of local dopamine systems and linked to cholinergic transmission. In addition, treatment with FAS in the substantia nigra also reveals the possible existence of at least two distinct pools of AChE with, respectively, non-cholinergic and cholinergic actions.
ESTHER : Dajas_1993_Brain.Res_616_1
PubMedSearch : Dajas_1993_Brain.Res_616_1
PubMedID: 7689409

Title : Non-cholinergic effects of acetylcholinesterase in the substantia nigra: a possible role for an ATP-sensitive potassium channel - Webb_1992_Exp.Brain.Res_89_49
Author(s) : Webb CP , Greenfield SA
Ref : Experimental Brain Research , 89 :49 , 1992
Abstract : Within the substantia nigra acetylcholinesterase has non-cholinergic actions that can be demonstrated at both behavioural and cellular levels: the aim of this study was, thus, to explore, in the in vitro guinea pig substantia nigra, the ionic mechanisms which mediate these non-classical phenomena. Acetylcholinesterase had a reversible hyperpolarizing action, via an opening of potassium channels, on a selective population of nigral neurons. These neurons could be identified by an ability to generate bursts of action potentials and by a sensitivity to either amphetamine or to a reduction of glucose in the perfusing medium. The acetylcholinesterase-induced hyperpolarization could not be attributed to a contaminant in the exogenous solution, since a highly purified preparation was even more potent. Furthermore, enzymatic action of any kind could be eliminated as boiled acetylcholinesterase was equally efficacious. The effect of acetylcholinesterase was not subject to tachyphylaxis and was resistant to blockade of potassium channels with tetraethylammonium: since both these phenomena are features of the D2 autoreceptor for dopamine within the substantia nigra, it seems unlikely that acetylcholinesterase is operating on the same target as dendritically released local dopamine. On the other hand, the actions of acetylcholinesterase were enhanced by low glucose and blocked by the sulfonylurea, tolbutamide. These results strongly suggest that acetylcholinesterase can exert a nonenzymatic action and that this action, in the substantia nigra, is mediated by an ATP-sensitive potassium channel.
ESTHER : Webb_1992_Exp.Brain.Res_89_49
PubMedSearch : Webb_1992_Exp.Brain.Res_89_49
PubMedID: 1350999

Title : Differential actions of acetylcholinesterase on the soma and dendrites of dopaminergic substantia nigra neurons in vitro - Hajos_1992_Brain.Res_585_416
Author(s) : Hajos M , Greenfield SA
Ref : Brain Research , 585 :416 , 1992
Abstract : In the substantia nigra, acetylcholinesterase (AChE) has non-cholinergic action on dopaminergic neurons. The subset of neurons particularly sensitive to AChE are characterized by functionally active apical dendrites extending into the pars reticulata and generating a powerful calcium conductance. This study thus attempted to establish directly the importance of these dendrites regarding the action of AChE. Segregation of the pars compacta from the pars reticulata did not affect the AChE-induced hyperpolarization on this sub-set of dopaminergic neurons. However, the ionic basis of the hyperpolarization was related to the integrity of the neurons: AChE caused an opening of potassium channels in intact cells. On the other hand when the pars reticulata containing apical dendrites was removed, an action of AChE involving the closure of calcium/sodium channels was revealed. The results demonstrate that the net effect of AChE need not be related to any particular segment of the dopaminergic neurons, whereas the nature of the mechanism underlying that effect depends on the presence, or otherwise, of the apical dendrites.
ESTHER : Hajos_1992_Brain.Res_585_416
PubMedSearch : Hajos_1992_Brain.Res_585_416
PubMedID: 1511329

Title : Non-cholinergic action of exogenous acetylcholinesterase in the rat substantia nigra. I. Differential effects on motor behaviour - Hawkins_1992_Behav.Brain.Res_48_153
Author(s) : Hawkins CA , Greenfield SA
Ref : Behavioural Brain Research , 48 :153 , 1992
Abstract : In the substantia nigra a non-cholinergic action of acetylcholinesterase has been demonstrated on motor behaviour. At the cellular level, electrophysiological studies have shown not only excitatory actions of AChE, but also inhibitory effects in response to larger amounts of the protein. In this study the possible dose-dependent effects of AChE were therefore explored in relation to circling behaviour. Both 'ipsiversive' turning (towards side of infusion and indicative of net decreased activity in the nigrostriatal pathway) and 'contraversive' turning (away from side of infusion and indicative of net increased activity) was observed for at least 2 weeks following a single unilateral AChE infusion. Ipsiversive turning occurred in 15-20% of animals in each group irrespective of dose. However, the actual number of animals exhibiting contraversive turning increased with increasing dose, whilst those not responding decreased. The most critical factor for direction of response appeared to be related not to dose, but cannula placement; infusion of AChE into more posterior regions of the substantia nigra evoked contraversive circling, whereas there appeared to be a discrete site in the anterior nigra in which AChE induced ipsiversive turning. This study thus suggests that subpopulations of nigrostriatal neurons show differential responsiveness to AChE.
ESTHER : Hawkins_1992_Behav.Brain.Res_48_153
PubMedSearch : Hawkins_1992_Behav.Brain.Res_48_153
PubMedID: 1616605

Title : Non-cholinergic action of exogenous acetylcholinesterase in the rat substantia nigra. II. Long-term interactions with dopamine metabolism - Hawkins_1992_Behav.Brain.Res_48_159
Author(s) : Hawkins CA , Greenfield SA
Ref : Behavioural Brain Research , 48 :159 , 1992
Abstract : Within the substantia nigra acetylcholinesterase (AChE) has a novel non-cholinergic action that is functionally manifest as chronic circling behaviour in rats. The aim of this study was to explore the possible biochemical mechanisms that could underlie the long-term behavioural effects of this protein, infused unilaterally into one substantia nigra. A single treatment of acetylcholinesterase induced modest but consistent circling behaviour in the presence of a systemic amphetamine challenge for the maximum time tested, up to 50 days: comparable infusions of saline were without effect. When animals received a challenge of the direct dopamine agonist apomorphine, no AChE-induced circling was observed: this result suggested that the phenomenon did not entail a down-regulation of striatal dopamine receptors. On the other hand, a challenge of the dopamine uptake inhibitor nomifensine resulted in AChE-induced circling that was indistinguishable from that seen in the presence of amphetamine: hence the circling behaviour seen could be attributable to an AChE-induced increase in availability of extracellular dopamine. In animals where AChE caused contraversive rotation, indicative of an enhanced activity in the nigrostriatal pathway, there was a significant elevation in the dopamine content of the striatum on the treated side. It is concluded that AChE can chronically enhance the release of dopamine from the nigrostriatal pathway such that motor behaviour is correspondingly modified, but to an extent sufficiently modest to avoid compensatory synaptic reversal mechanisms.
ESTHER : Hawkins_1992_Behav.Brain.Res_48_159
PubMedSearch : Hawkins_1992_Behav.Brain.Res_48_159
PubMedID: 1616606

Title : Acetylcholinesterase as a Modulatory Neuroprotein and its Influence on Motor Control -
Author(s) : Greenfield SA
Ref : In Multidisciplinary approaches to cholinesterase functions - Proceedings of Fourth International Meeting on Cholinesterases , (Shafferman, A. and Velan, B., Eds) Plenum Press, New York :233 , 1992
PubMedID:

Title : A Non-Cholinergic Function for AChE in the Substantia Nigra -
Author(s) : Greenfield SA
Ref : In: Cholinesterases: Structure, Function, Mechanism, Genetics, and Cell Biology , (Massoulie J, Barnard EA, Chatonnet A, Bacou F, Doctor BP, Quinn DM) American Chemical Society, Washington, DC :366 , 1991
PubMedID:

Title : Poster: Characterization of a non-cholinergic action of AChE on the membrane properties of Pars Compacta neurones -
Author(s) : Webb CP , Greenfield SA
Ref : In: Cholinesterases: Structure, Function, Mechanism, Genetics, and Cell Biology , (Massoulie J, Barnard EA, Chatonnet A, Bacou F, Doctor BP, Quinn DM) American Chemical Society, Washington, DC :382 , 1991
PubMedID:

Title : Poster: Distinct dose-dependency of the non-cholinergic effects of AChE on circling behaviour -
Author(s) : Levesque D , Greenfield SA
Ref : In: Cholinesterases: Structure, Function, Mechanism, Genetics, and Cell Biology , (Massoulie J, Barnard EA, Chatonnet A, Bacou F, Doctor BP, Quinn DM) American Chemical Society, Washington, DC :381 , 1991
PubMedID:

Title : Poster: AChE release from the Substantia Nigra is associated with certain types of movement : Direct evidence On-line -
Author(s) : Jones SA , Greenfield SA
Ref : In: Cholinesterases: Structure, Function, Mechanism, Genetics, and Cell Biology , (Massoulie J, Barnard EA, Chatonnet A, Bacou F, Doctor BP, Quinn DM) American Chemical Society, Washington, DC :380 , 1991
PubMedID:

Title : Behavioural correlates of the release and subsequent action of acetylcholinesterase secreted in the substantia nigra - Jones_1991_Eur.J.Neurosci_3_292
Author(s) : Jones SA , Greenfield SA
Ref : European Journal of Neuroscience , 3 :292 , 1991
Abstract : Acetylcholinesterase is secreted in the central nervous system (independently of cholinergic transmission) in a non-classic, non-enzymatic capacity. A light-emitting reaction has recently been established that demonstrates release of this protein from the substantia nigra of a guinea pig with a temporal resolution corresponding to real time, i.e. 'on-line'. In this study the technique has been applied to investigate the significance of this novel phenomenon in the generation of specific types of movement. During locomotion a 'pulsatile' release of acetylcholinesterase occurs much more frequently than in other situations. However, these pulses of released acetylcholinesterase are of shorter duration than the respective periods of locomotion that caused them. Furthermore, as episodes of movement are repeated, the release of acetylcholinesterase becomes less likely. These observations suggest that the phenomenon does not simply reflect ongoing movement. Indeed, chewing behaviour is frequently initiated when acetylcholinesterase release occurs during locomotor activity. Hence, acetylcholinesterase released in association with locomotion may favour the onset of further types of movement.
ESTHER : Jones_1991_Eur.J.Neurosci_3_292
PubMedSearch : Jones_1991_Eur.J.Neurosci_3_292
PubMedID: 12106207

Title : Pressure ejection of acetylcholinesterase within the guinea-pig substantia nigra has non-classical actions on the pars compacta cells independent of selective receptor and ion channel blockade - Greenfield_1989_Neurosci_29_21
Author(s) : Greenfield SA , Nedergaard S , Webb CP , French M
Ref : Neuroscience , 29 :21 , 1989
Abstract : In the substantia nigra, acetylcholinesterase may have a non-classical function unrelated to cholinergic transmission. Acetylcholinesterase is released from the dendrites of dopamine-containing nigrostriatal neurons and has a subsequent action on these cells, independent of hydrolysis of acetylcholine. The aim of this study was to explore further the precise nature of this "non-cholinergic" action of acetylcholinesterase. Acetylcholinesterase was pressure-ejected in the vicinity of the dendrites of putative nigrostriatal neurons in vitro, in near-physiological amounts, and the effects of this treatment on neuronal membrane properties were investigated. It was found that acetylcholinesterase reversibly hyperpolarized the nigrostriatal cell membrane independent of sodium and calcium channel blockade. Acetylcholinesterase pretreated with an irreversible inhibitor (Soman) of its classical catalytic site produced the same hyperpolarizing effect: however, butyrylcholinesterase, which hydrolyses acetylcholine, was inefficacious. These effects persisted in the presence of the dopamine receptor antagonist sulpiride. It is suggested the acetylcholinesterase can facilitate the generation of a long-duration conductance, which enhances the firing of nigrostriatal cells if the neuron is first hyperpolarized. Hence the action of acetylcholinesterase would be to modulate inputs. These actions are independent of direct interaction with acetylcholine and dopamine systems. Hence, in the substantia nigra, acetylcholinesterase might serve as a "neuromodulatory" secretory protein.
ESTHER : Greenfield_1989_Neurosci_29_21
PubMedSearch : Greenfield_1989_Neurosci_29_21
PubMedID: 89219601

Title : An electrophysiological action of acetylcholinesterase independent of its catalytic site - Greenfield_1988_Exp.Brain.Res_70_441
Author(s) : Greenfield SA , Jack JJ , Last AT , French M
Ref : Experimental Brain Research , 70 :441 , 1988
Abstract : Acetylcholinesterase (AChE) is released from the cell bodies and/or dendrites of dopaminergic neurones in the substantia nigra. Extracellular AChE can modify both the electrical activity of dopaminergic nigral neurones and the associated motor behaviour of the animal. These effects seem to be unrelated to hydrolysis of acetylcholine, but the underlying cellular mechanisms of these actions of AChE are unknown. The possible non-cholinergic action of AChE on the membrane properties of dopaminergic neurones was thus investigated by intracellular recording from midbrain slices in vitro. Application of AChE resulted in a marked hyperpolarization of the membrane accompanied by a decrease in input resistance, sometimes preceded by a period of spontaneous firing. Butyrylcholinesterase (BCHE) was without effect. AChE pre-treated with an irreversible inhibitor (Soman) of its enzymic activity caused similar changes to those seen following administration of untreated AChE. It is concluded that AChE can modify the membrane properties of nigrostriatal neurones in a way that is independent of its ability to hydrolyse acetylcholine. This novel biological property of AChE provides a possible mechanism by which this neurosecretory protein could modulate the functioning of the neurones from which it is secreted and suggests that other 'non-cholinergic' actions of AChE might exist.
ESTHER : Greenfield_1988_Exp.Brain.Res_70_441
PubMedSearch : Greenfield_1988_Exp.Brain.Res_70_441
PubMedID: 3384044

Title : On-line visualization of dendritic release of acetylcholinesterase from mammalian substantia nigra neurons - Llinas_1987_Proc.Natl.Acad.Sci.U.S.A_84_3047
Author(s) : Llinas RR , Greenfield SA
Ref : Proc Natl Acad Sci U S A , 84 :3047 , 1987
Abstract : This study presents, to our knowledge, the first on-line measurement of acetylcholinesterase (AcChoEase) release from brain tissue. It is now well established that a soluble form of the enzyme is released from central nervous system neurons, and it has been proposed on indirect grounds that such release may occur not only from presynaptic terminals but also from the dendrites of dopamine-containing nigrostriatal neurons. We have used a chemiluminescent reaction to examine the real-time release of AcChoEase from the substantia nigra in vitro in brainstem slices. The light emission was captured by two fiber optic systems, one in direct contact with the brain slice from below and the second 4-mm above the slice, allowing simultaneous imaging of the emitted light and quantitative photometry. It was determined that the light signals are not due to the spontaneous hydrolysis of acetylcholine or the presence of free choline, but are caused by the enzymatic action of AcChoEase. Using this technique, it can be directly shown that AcChoEase is spontaneously released from the soma or dendrites of nigral neurons. The release of the enzyme, which is stored in the subcisternal dendritic compartment, is resistant to blockade of voltage-dependent sodium conductances, is calcium dependent, and can be increased by addition of potassium to the bathing solution. The procedure we describe here will make it possible to study the release of endogenous AcChoEase on a time-scale close to that over which it functions.
ESTHER : Llinas_1987_Proc.Natl.Acad.Sci.U.S.A_84_3047
PubMedSearch : Llinas_1987_Proc.Natl.Acad.Sci.U.S.A_84_3047
PubMedID: 3472250

Title : Acetylcholinesterase has a non-cholinergic neuromodulatory action in the guinea-pig substantia nigra - Last_1987_Exp.Brain.Res_67_445
Author(s) : Last AT , Greenfield SA
Ref : Experimental Brain Research , 67 :445 , 1987
Abstract : Acetylcholinesterase is released within the substantia nigra from the soma/dendrites of nigrostriatal neurons. Previous work suggests that this phenomenon is independent of cholinergic systems, but rather serves to modulate the sensitivity of dopamine-containing nigrostriatal cells to synaptic events. This hypothesis was tested directly in the anaesthetized guinea-pig. Micro-infusion of acetylcholinesterase into the substantia nigra led to an increase in spontaneous firing of nigrostriatal neurons. Furthermore, the pattern of firing evoked by stimulation of the striatum was markedly enhanced. By contrast, administration of butyrylcholinesterase had no effect. It thus appears that acetylcholinesterase has a modulatory action on the firing of nigrostriatal cells, independent of hydrolysis of acetylcholine.
ESTHER : Last_1987_Exp.Brain.Res_67_445
PubMedSearch : Last_1987_Exp.Brain.Res_67_445
PubMedID: 3040458

Title : Application of acetylcholinesterase to the substantia nigra induces stereotypy in rats - Weston_1985_Behav.Brain.Res_18_71
Author(s) : Weston J , Greenfield SA
Ref : Behavioural Brain Research , 18 :71 , 1985
Abstract : In the substantia nigra, acetylcholinesterase may have a non-cholinergic function. Previous work suggests that release of acetylcholinesterase locally in the substantia nigra leads to a net increase in dopaminergic activity in the ipsilateral striatum. To investigate this hypothesis, acetylcholinesterase was microinjected bilaterally into the substantiae nigrae of awake rats and stereotyped behaviour used as an indication of increased dopaminergic activity in the striatum. Acetylcholinesterase increased stereotypy in rats, while butyrylcholinesterase and the vehicle, distilled water, were ineffective. The functional significance of acetylcholinesterase in the substantiae nigrae of freely moving animals is discussed in the light of its apparent association with dopaminergic rather than cholinergic systems.
ESTHER : Weston_1985_Behav.Brain.Res_18_71
PubMedSearch : Weston_1985_Behav.Brain.Res_18_71
PubMedID: 3911982

Title : A novel function for acetylcholinesterase in nigro striatal neurons -
Author(s) : Greenfield SA
Ref : In: Cholinesterases, fundamental and applied aspects : proceedings of the Second International Meeting on Cholinesterases , (Brzin M, Barnard EA, Sket D, Eds) De Gruyter :289 , 1984
PubMedID:

Title : A non-cholinergic function for acetylcholinesterase in the substantia nigra: behavioural evidence - Greenfield_1984_Exp.Brain.Res_54_513
Author(s) : Greenfield SA , Chubb IW , Grunewald RA , Henderson Z , May J , Portnoy S , Weston J , Wright MC
Ref : Experimental Brain Research , 54 :513 , 1984
Abstract : Acetylcholinesterase is released from substantia nigra neurons, independently of cholinergic transmission. In an attempt to discover the functional significance of this phenomenon, the behavioural effects of injecting acetylcholinesterase into one substantia nigra of the rat were investigated. Following a single injection of the enzyme, intraperitoneal amphetamine evoked circling behaviour in a direction away from the side of injection. Purified acetylcholinesterase with a similar electrophoretic mobility to the endogenous secreted form, was far more potent in eliciting circling than much higher activities of commercial enzyme, consisting of several molecular species of acetylcholinesterase. Similar infusions of butyrylcholinesterase did not induce circling. Depending upon the amount of enzyme initially given, the behavioural effects of a single injection of acetylcholinesterase persisted for up to thirty days. During this period apomorphine, administered systemically, induced transient circling towards the acetylcholinesterase-treated side. It is concluded that secreted acetylcholinesterase has a functional significance within the substantia nigra, independent of cholinergic transmission. This released enzyme could exert long-term changes in the activity of the nigrostriatal system, involving modification of dopamine striatal receptors.
ESTHER : Greenfield_1984_Exp.Brain.Res_54_513
PubMedSearch : Greenfield_1984_Exp.Brain.Res_54_513
PubMedID: 6202543

Title : Poster 38. Turning behaviour folowing microinjection of acetylcholinesterase and dopamine antagonists into the substantia nigra -
Author(s) : Weston J , Greenfield SA
Ref : In: Cholinesterases, fundamental and applied aspects : proceedings of the Second International Meeting on Cholinesterases , (Brzin M, Barnard EA, Sket D, Eds) De Gruyter , 1984
PubMedID:

Title : In vivo release of acetylcholinesterase in cat substantia nigra and caudate nucleus -
Author(s) : Greenfield SA , Cheramy A , Leviel V , Glowinski J
Ref : Nature , 284 :355 , 1980
PubMedID: 7360271