Potentiation by Smooth Muscle Stimulants of the Hypogastric Nerve — Vas Deferens Preparation from Normal and Castrated Guinea‐Pigs

It is shown that a variety of smooth muscle stimulants cause marked potentiation of the motor response of the isolated vas deferens to hypogastric nerve stimulation. The substances used were: adrenaline, noradrenaline, acetylcholine, histamine, serotonin, angiotensin, bradykinin, Substance P and barium chloride. The doses producing this potentiation were in most cases 10–1000 times lower than those necessary to cause a direct contraction of the vas deferens. There were no clearcut differences between castrated and normal animals. Oxytocin and vasopressin were without effect while different prostaglandins (PGE 1 , PGF 1 and a crude PG preparation) caused inconsistent responses. Possible mechanisms for the potentiation are discussed and it is suggested that the most probable explanation is a direct effect on the smooth muscle, but an effect on the transmitter stores of the postganglionic adrenergic neuron cannot be ruled out. Possible functional implications are further discussed.