The response to transmural stimulation of isolated arterial strips and its modification by drugs

Abstract

Transmural electrical stimulation of isolated aortic strips of rabbits, induced contractions of the muscle which were blocked by concentrations of cocaine and lignocaine which augmented the response to noradrenaline. The adrenergic neurone blocking agents bretylium, guanethidine and bethanidine also blocked selectively the response to transmural stimulation. With bretylium and guanethidine the responses to noradrenaline were augmented. α-Receptor blockade with piperoxan, phentolamine, phenoxybenzamine and dihydrogenated ergot alkaloids also blocked the responses to transmural stimulation. Cocaine in low concentration and dexamphetamine augmented the responses to electrical stimulation. They also delayed onset of block with adrenergic neurone blocking drugs and reversed this when it was already established. Hexamethonium and pentolinium, in concentrations which in other tissues are known to cause complete blockade of ganglionic transmission. had no effect on electrical stimulation. It is concluded that the responses to electrical stimulation are the result of excitation of post-ganglionic adrenergic axons in the walls of the arterial preparation. Strips of common carotid, superior mesenteric, renal, pulmonary and common iliac arteries of the rabbit gave responses to electrical stimulation similar to those of the aorta.