THE STIMULATING EFFECT OF ACETYLCHOLINE ON THE MAMMALIAN HEART AND THE LIBERATION OF AN EPINEPHRINE-LIKE SUBSTANCE BY THE ISOLATED HEART

Abstract

The injn. of ACh into the isolated atropinized heart of dogs, cats, rabbits and guinea pigs regularly causes an epinephrine-like effect, i.e., an increase of heart rate and amplitude, as well as a change of blood flow in the coronary vessels. The positive ino- and chrono-tropic effects of ACh are abolished by ergotamine, by curare, and by nicotine. The pharmacologic characteristics of the stimulating action of ACh on the heart enable us to designate it as "nicotine-like." In the perfusate of the isolated heart, it is possible to identify the presence of an epinephrine-like substance liberated when ACh or nicotine are injected into the heart. Under the stimulus of these drugs the perfusate acquires an activity which can be demonstrated by its positive inotropic action on the hypodynamic frog heart and by a relaxing effect on the rectal cecum of the fowl and on the small intestine of the rabbit.