EFFECTS OF VARIOUS AUTONOMIC DRUGS ON ISOLATED, PERFUSED MESENTERIC ARTERIES

¹ Department of Pharmacology and Anesthesia, College of Medicine, University of Iowa, Iowa City, Iowa

An isolated preparation using the perfused mesenteric artery and small resistance vessels with its sympathetic nerve supply has been described. The responses to sympathetic nerve stimulation indicated that the electrodes were postganglionic. No evidence for cholinergic receptors or beta receptors was obtained. In this preparation yohimbine, guanethidine and reserpine were capable of inhibiting nerve stimulation, while ephedrine, amphetamine, tyramine and phenylephrine were capable of enhancing the responses to epinephrine, norepinephrine and nerve stimulation under certain conditions. Large doses of amphetamine, ephedrine and tyramine antagonized the pressor responses to injected catecholamines and to nerve stimulation. Ephedrine and tyramine demonstrated a direct sympathomimetic action only in the presence of recirculating catecholamines. -Phenylisopropylhydrazine prolonged the tyramine- -induced potentiation of the presser responses to injected catecholamines and to nerve stimulation. Cocaine appeared to prevent competitively the uptake and release of catecholamines from the nerve terminals. This appears to be a highly responsive preparation to study the action and interaction of drugs on resistance vessels using the mesenteric artery and splanchnic nerve.