Effects of cholinergic and adrenergic drugs on intraluminal pressures and contractility of the rat testis and epididymis in vivo

Abstract

Intravenous administration of methacholine (200 μg/kg) caused no changes in the seminiferous tubules of rats, but significantly increased intraluminal pressures and contractility of the caput, the corpus and the cauda epididymis. The effect of methacholine was abolished by pretreatment with atropine (500 μg/kg), but not by phentolamine (400 μg/kg) or propranolol (400 μg/kg). Adrenaline (5-40 μg/kg), noradrenaline (5-40 μg/kg) and phenylephrine (100-400 μg/kg) had no effect on the seminiferous tubules, but dose-dependently elevated intraluminal pressures and enhanced the contractility of all regions of the epididymis. Isoproterenol (100-800 μg/kg) did not affect intraluminal pressures of the seminiferous tubules and the epididymal duct. The stimulatory effect of adrenergic agonists was specifically blocked by phentolamine, but not by propranolol or atropine. Cholinergic and adrenergic antagonists did not alter spontaneous contraction of the epididymis. The results suggest that the contractility of all segments of the rat epididymis, but not the seminiferous tubules, can be increased by autonomic drugs. The enhancing effect of adrenergic drugs is probably the result of activation through α-adrenergic receptors.