EFFECT OF RESERPINE, PHENOXYBENZAMINE AND COCAINE ON NEUROMUSCULAR TRANSMISSION IN THE VAS DEFERENS OF THE GUINEA PIG

¹ Department of Pharmacology, State University of New York, Downstate Medical Center, Brooklyn, New York

Chemical analysis of vasa deferentia taken from guinea pigs pretreated with high doses of reserpine showed almost complete depletion of their norepinephrine stores. However, the contractile response of the reserpine-pretreated vas deferens to hypogastric nerve stimulation was still maintained at 60% of the control level. In vitro treatment with reserpine (1.6 x 10^-7 to 4.1 x 10^-5 M) had no inhibitory effect on neuromuscular transmission in the vas deferens. Phenoxybenzamine was found to be ineffective in blocking nerve-mediated responses of the vas deferens obtained from reserpine-pretreated guinea pigs. In fact, phenoxybenzamine, (1.77-2.95 x 10^-4 M) markly potentiated (about 5-fold) nervemediated responses and, in addition, always induced spontaneous contractions of the reserpine-pretreated vas deferens. In the presence of cocaine (3.2 x 10^-6 to 9.8 x 10^-5 M), contractions of the reserpine-pretreated vas deferens induced by hypogastric nerve stimulation remained totally unaffected, whereas responses to exogenous norepinephrine were augmented nearly 300-fold.