Title: Meproadifen enhances activation and desensitization of the acetylcholine receptor-ionic channel complex (AChR): single channel studies Aracava Y, Albuquerque EX Ref: FEBS Letters, 174:267, 1984 : PubMed
The effects of the quaternary agent meproadifen on ACh-activated channel currents were studied on myoballs cultured from hind limb muscles of neonatal rats. Meproadifen (0.02-0.1 microM) combined with ACh (0.1-0.3 microM) in the patch pipette caused an increase, followed by a decrease, in the frequency of channel openings. At concentrations greater than 0.2 microM the initial phase was not detected and a rapid and marked reduction in the opening frequency was observed. Meproadifen (up to 2.5 microM) produced no change in the duration or conductance of the open state of ACh-activated channels. In addition, this agent induced the appearance of events with a marked increase in the 'noise' during the opening phase. The lack of effect under inside-out patch conditions suggested that meproadifen binds to a site located at the external portion of the nicotinic macromolecule and has no access to it through the cell membrane. This study indicated that non-competitive antagonists such as meproadifen can facilitate receptor activation and desensitization.
        
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Aracava Y, Albuquerque EX (1984) Meproadifen enhances activation and desensitization of the acetylcholine receptor-ionic channel complex (AChR): single channel studies FEBS Letters174: 267-74
Aracava Y, Albuquerque EX (1984) FEBS Letters174: 267-74