[Eserine-induced change in membrane potential of frog muscle fibers]

The action of eserine of acetylcholinesterase (AchE) reversible inhibitor of frog muscle fibres membrane potential (MP) under various physico-chemical conditions in external solution was studied. The data obtained show that changes of external pH in any direction decrease the depolarisation of the membrane produced by eserine. The dose-effect curve is linear at pH 7, but it has saturation at pH 6 and pH 9. Dependence of the membrane depolarisation in the presence of eserine upon calcium ions concentration in external solution is S-shape. Protonophore 3C1CCP (carbonilcianamid-m-3C1-phenylhydrazon) depolarises the membrane further in the presence of eserine. Valinomycin under these conditions completely restores the MP. Evidence is obtained that eserine reduces potassium permeability of the muscle membrane. It is supposed that membrane-bound AchE is involved in the ionic permeability regulation of the muscle membrane at rest.