[Seasonal changes in neuromuscular transmission in experiments on dissected or curarized frog muscles]

Abstract

The end-plate currents and potentials (EPCs and EPPs) in cut or curarized muscles were investigated in frogs maintained at different temperatures (5 and 20-25 degrees C) before experiments in summer and in winter. EPCs and EPPs were elicited by nerve stimulation with different frequencies (1 and 100/s). Seasonal changes in amplitude, facilitation and depression of the EPPs and EPCs observed in curarized and cut (not curarized) muscles differed quantitatively and qualitatively. These differences may be explained assuming that sensitivity of the neuromuscular junction to the curare action (probably, a presynaptic one) is season-variable.