[Effect of verapamil and manganese ions on the acetylcholine sensitivity of the membrane of innervated and denervated frog muscle fibers].

Experiments on frogs were made to examine the effect of verapamil and Mn2+ on acetylcholine sensitivity of the postsynaptic membrane of intact and denervated muscle fibers. The inhibitory action of verapamil on acetylcholine sensitivity of denervated muscle fibers was found to be more pronounced than that on intact ones. Ca2+ replacement by Mn2+ in a solution slightly lowered acetylcholine sensitivity of the membrane of denervated and intact muscle fibers. It is concluded that the synaptic and extrasynaptic cholinoreceptors of the frog muscle membrane differ as regards the effect produced on them by verapamil. At the same time the effect of verapamil on the cholinoreceptors is not reduced to the drug property to restrict the ingress of Ca2+ to muscle fibers.