Inhibition of Constrictor Responses of Dog Coronary Artery by Atropine

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Abstract
A possible effect of atropine on a variant form of angina pectoris was studied using the left circumflex coronary arterial strips of dogs. Acetylcholine 10-5-10-3 g/ml dose-dependently constricted the isolated arterial strips during K-contracture in 6 cases, and repetitive applications of acetylcholine could produce similar contractions in the control. In 18 strips atropine 10-6 g/ml depressed the contractions of coronary arteries induced by acetylcholine 10-5-10-3 g/ml. In 5 arterial strips atropine 10-6 g/ml inhibited norepinephrine-induced responses of the arteries and by 10-5 g/ml further suppression of the responses was obtained. Atropine may suppress the contractile responses of the coronary artery induced by acetylcholine and norepinephrine through a muscarinic-receptor blocking action and simultaneously partly through an adrenergic .alpha.-receptor blocking action.