PRESSORECEPTOR REFLEXES FROM THE CAROTID SINUS

Abstract

A continuous artificial circuit with continuous gaseous equilibration of the perfusing fluid was used in studying carotid sinus reflexes in dogs anesthetized with morphine and urethane. The vascular reflex was definite and constant, responding with striking fineness to ordinary pressure fluctuations. At maximal sinus pressure vase. relaxation appeared to be maximal; at subliminal pressures vasomotor activity appeared completely unbridled, with the vagosympathetic-depressor trunks sectioned. Non-maintenance of the reflex blood-pressure changes in response to unnaturally abrupt intrasinus pressure changes demonstrated the vicarious activity of the aortic nerves and seemed related to reported characteristics of sinus receptor discharge. With aortic nerves intact, the heart reflex was more variable, more poorly maintained, and in many cases so weak relative to the aortic afferent system as to be secondarily completely reversed by the latter. The sympathetic (and humoral?) efferent component was consistently demonstrable after "vagotomy." Danielo-polu''s concept of "amphotropism" is considered untenable. The resp. reflex was the least constant of the 3, and like the heart reflex, was often completely reversed under the influence of intact aortic nerves.