ERGOMETRINE CONTRACTS ISOLATED CANINE CORONARY-ARTERIES BY A SEROTONERGIC MECHANISM - NO ROLE FOR ALPHA-ADRENOCEPTORS

Abstract

Studies were performed on isolated canine coronary artery segments to characterize the mechanism of the constrictor response of ergometrine (ergonovine), an agent used to induce coronary vasospasm in patients with variant angina. Changes in isometric tension were measured in coronary ring segments suspended in organ baths at 37 degrees C filled with a buffered salt solution. Single concentration-response curves were obtained in each tissue by cumulative addition of agonist. Maximum responses to 5-hydroxytryptamine (5-HT) were greater than for ergometrine or phenylephrine, but ergometrine had the lowest EC50. Alpha adrenoceptor block by prazosin (10 nM) or the irreversible antagonist benextra..