EFFECTS OF COCAINE AND TETRAETHYLAMMONIUM ON THE SPIKE POTENTIALS AND CONTRACTIONS INDUCED BY TRANSMURAL STIMULATION IN THE RAT VAS DEFERENS

Abstract

Effects of cocaine and tetraethylammonium (TEA) on the spike potential induced by transmural nerve stimulation were investigated with microelectrodes in smooth muscle cells of rat vas deferens. Resting membrane potential was not changed by 10^-5M cocaine. 10^-5M cocaine reduced the amplitudes of spontaneous excitatory junction potentials and diminished generation of excitatory junction potentials induced by nerve stimulation. However, cocaine did not affect the electrophysiological parameters of spike potentials ; overshoot potential, threshold potential and duration of spikes were not changed by cocaine. Cocaine slightly inhibited the twitch contractions to transmural nerve stimulation. In contrast, 1-5 mM TEA increased the overshoot potentials and prolonged the duration of spikes dosedependently without changing the resting membrane potential. Twitch contractions to transmural nerve stimulation were greatly enhanced by 2.5 mM TEA. These results suggest that TEA, but not cocaine, may increase the Ca-influx which is believed to occur during spike generation in the smooth muscle cells of vas deferens.