[Antidromic action of potassium in the neuromotor synapse].

The possibility of potassium accumulation in the synaptic cleft and a participation of its antidromic action in the regulation of presynaptic processes were estimated in experiments on neuromuscular junctions of the frog. In potassium-enriched solution, the reversal potential obtained by the linear extrapolation from the region of high membrane potentials was considerably altered according to the Takeuchi equation. The change of the reversal potential obtained by interpolation was insignificant as predicted by the Goldman--Hodgkin--Katz equation. In normal solution under the change of the nerve stimulation frequency from 0.5/sec to 50/sec the positive shift of the reversal potential occurred as revealed by both techniques. This indicates potassium accumulation in active synaptic segments during the activity. Elimination of the potassium component in the end-plate current by clamping of the membrane potential at the -130 mV level resulted in lowering of facilitation under paired nerve stimulation (20 msec interval) and in a decrease of the facilitation rate under 50/sec stimulation. The data corroborate an antidromic potassium action on the neuromuscular synapse.