[Effect of low-concentration potassium ion solution on the frog neuromuscular synapse].

The effect of solution with low potassium concentration ([K+]o = 0.2 mM) on neuromuscular synapse was studied in m. cutaneus pectoris of the frog. The MPs of muscle fibers and the amplitudes of m.e.p.p. practically did not change after Ringer's solution had been replaced by low potassium one. The frequency of m.e.p.p. increased up to 100/sec. The latency of e.p.p. increased the rise time of e.p.p. decreased slightly. The amplitude and quantum content of e.p.p. decreased also. After 5 min of action of the low potassium solution the blockade of synaptic transmission occurred. The data suggest the depolarization of motor nerve terminals in the presence of low--potassium solution to be a result of the depressed activity of the ionic pump.