Reflex Cardiovascular Effects of Epicardial Stimulation by Acetylstrophanthidin in Dogs

Abstract

Application of 25 to 100 µg of acetylstrophanthidin to the epicardium of the left ventricle of anesthetized and unanesthetized dogs caused hypotension and bradycardia without signs of discomfort. The response developed after an average latency of 8 seconds and lasted up to 12 minutes. Cooling the cervical vagi to 8 to 10°C or prior application of 0.1% procaine hydrochloride to the epicardium of the heart blocked the response. The response was, therefore, a reflex; the sensory receptors were located in the surface layers of the left ventricle. Electrophysiological recordings from single and multifiber preparations of the right recurrent cardiac nerve showed that the receptors for this reflex were mechanoreceptors whose fibers belonged to the C group. The sinus bradycardia caused by digitalis glycosides may result partly from excitation of these receptors.