CORONARY VASOCONSTRICTION BY LOCALLY ADMINISTERED ACETYLCHOLINE, CARBACHOL AND BETHANECHOL IN ISOLATED, DONOR‐PERFUSED, RAT HEARTS

Abstract

Experiments were carried out on rat isolated heart preparations in which the coronary vasculature was perfused through the aorta at a constant flow rate with arterial blood from donor animals. Single doses of drugs were injected into the aortic cannula. Small doses of acetylcholine, carbachol or bethanechol decreased perfusion pressure (PP) without markedly affecting left ventricular pressure (LVP) and heart rate (HR); larger doses of these drugs increased PP (vasoconstriction), and decreased LVP and HR in a dose‐dependent manner. Acetylcholine, carbachol and bethanechol had almost no effects when perfused through the aorta in such a way as to exclude the coronary vessels. Coronary vasoconstriction in response to acetylcholine, carbachol and bethanechol was not significantly affected by reserpine pretreatment, phentolamine or hexamethonium, but was antagonized by small doses of atropine. From these results it is concluded that in the coronary vasculature of the rat, the receptors involved in the vasoconstrictor actions of acetylcholine, carbachol and bethanechol are muscarinic. 1980 British Pharmacological Society