Reid_2013_Neurosci_234_53

The cholinergic system plays important roles in neurotransmission in both the peripheral and central nervous systems. The cholinergic neurotransmitter acetylcholine is synthesized by choline acetyltransferase (ChAT) and its action terminated by acetylcholinesterase (AChE) and butyrylcholinesterase (BCHE). The predominance of AChE has focused much attention on understanding the relationship of this enzyme to ChAT-positive cholinergic neurons. However, there is ample evidence that BCHE also plays an important role in cholinergic regulation. To elucidate the relationship of BCHE to neural elements that are producing acetylcholine, the distribution of this enzyme was compared to that of ChAT in the mouse CNS. Brain tissues from 129S1/SvImJ mice were stained for BCHE and ChAT using histochemical, immunohistochemical and immunofluorescent techniques. Both BCHE and ChAT were found in neural elements throughout the CNS. BCHE staining with histochemistry and immunohistochemistry produced the same distribution of labeling throughout the brain and spinal cord. Immunofluorescent double labeling demonstrated that many nuclei in the medulla oblongata, as well as regions of the spinal cord, had neurons that contained both BCHE and ChAT. BCHE-positive neurons without ChAT were found in close proximity with ChAT-positive neuropil in areas such as the thalamus and amygdala. BCHE-positive neuropil was also found closely associated with ChAT-positive neurons, particularly in tegmental nuclei of the pons. These observations provide further neuroanatomical evidence of a role for BCHE in the regulation of acetylcholine levels in the CNS.