The effect of propranolol on sympathetic nerve stimulation in isolated vasa deferentia

Abstract

Abstract (±)-Propranolol hydrochloride (0·5 mg kg−1 twice daily, subcutaneously, for 3 days or approximately 2·4 mg kg−1 daily, orally, for 21 days) failed to produce ptosis or to affect responses to transmural stimulation of isolated vasa deferentia removed from treated mice. In guinea-pig isolated vasa deferentia responses to transmural stimulation through parallel electrodes were reduced by propranolol (1 to 20 μg ml−1); blockade was concentration dependent, fast to equilibrium (45 min), easily reversed by washing but not reversed by (+)-amphetamine sulphate (0·2 μg ml−1). At lower concentrations (0·04 and 0·2 μg ml−1), propranolol marginally potentiated responses to transmural stimulation. In contrast, guanethidine (0·2 μg ml−1) produced a slow onset blockade which was completely reversed by (+)-amphetamine. The response to electrical stimulation through concentric ring electrodes was reduced by low concentrations of propranolol but this effect is ascribed to the known local anaesthetic actions of propranolol and no evidence of true adrenergic neuron blockade was found.