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Acetylcholine Release from Isolated Synaptic Vesicles Related to Ionic Permeability Changes: Continuous Detection with a Chemiluminescent Method
Author(s) -
Diebler M. F.
Publication year - 1982
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1982.tb12584.x
Subject(s) - protonophore , valinomycin , chemistry , ionophore , acetylcholine , biophysics , vesicle , divalent , synaptic vesicle , calcium , nigericin , membrane potential , chromatography , biochemistry , membrane , endocrinology , organic chemistry , biology
The effect of ionic permeability changes on acetylcholine (ACh) release from isolated cholinergic synaptic vesicles of Torpedo was studied using a chemiluminescent method for continuous ACh detection. Vesicles rendered freely permeable to potassium by valinomycin lost most of their ACh content in K + media, if the accompanying anion was permeant; it thus appeared that ACh leakage occurred as the result of internal osmotic changes. Upon addition of ionophores that catalyse monovalent cation/H + exchange (gramicidin D or a mixture of valinomycin plus protonophore FCCP), a rapid but transient ACh release was observed. Surprisingly, nigericin which also catalyses K + /H + exchange, had no effect on ACh release. The divalent cation ionophore A23187 promoted ACh release only when calcium (and not magnesium) was introduced into the external medium in a millimolar concentration range. As the simultaneous addition of the protonophore FCCP and A23187 decreased this calcium‐dependent ACh leakage, a releasing effect of A23187 through Ca 2+ /H + exchange is suspected. The present results emphasise the role of internal protons for ACh retention inside synaptic vesicles.