Inhibition of constrictor responses of dog coronary artery by atropine. A possible effectiveness of atropine on variant form of angina pectoris.

A possible effectiveness of atropine on variant form of angina pectoris was investigated using the left circumflex coronary arterial strips of dogs. Acetylcholine 10(-5)--10(-3) Gm/ml dose-dependently constricted the isolated arterial strips during potassium-contracture in 6 cases, and repetitive applications of acetylcholine could produce the similar contractions to the control. In 18 strips atropine 10(-6) Gm/ml significantly depressed the contractions of coronary arteries induced by acetylcholine 10(-5)--10(-3) Gm/ml. In 5 arterial strips atropine 10(-6) Gm/ml significantly inhibited norepinephrine-induced responses of these arteries, and by 10(-5) Gm/ml further suppression of the responses was obtained. The results suggest that atropine may suppress the contractile responses of the coronary artery induce by acetylcholine and nonrepinephrine through a muscarinic-receptor blocking action and simultaneously partly through an adrenergic alpha-receptor blocking action.