Carotid chemoreceptor reflex effects on coronary flow and heart rate

Abstract

The innervated Langendorff's dog heart preparation in ventricular fibrillation with completely separated cross circulations to the head and heart was used for clarifying the mechanism of the carotid chemoreceptor reflex induced by nicotine, lobeline, 5-hydroxytryptamine, and acetylcholine. The effects of carotid chemoreflex were studied on the atrial rhythm and the coronary blood flow at constant pressure. A prompt decrease in atrial rate followed by a delayed acceleration was observed. Coronary dilation followed by constriction was observed concomitantly. In the atropinized heart evidences of a sympathetic component in the chemoreceptor reflex became evident. The sympathetic activity disappeared upon cooling of the head perfusion to 31 C, while the vagal action persisted. Warming to 40 C made the sympathetic effect more prominent. The reciprocal relation between the atrial rate and the coronary vascular tone may indicate a vagal coronary dilator and a sympathetic coronary constrictor effect in the dog.