Baroceptor reflex mechanisms in swine

Abstract

In swine with intact vagi and carotid sinuses, occlusion of both common carotid arteries caused a significant rise in blood pressure, whereas desocclusion of these vessels was followed by an immediate and equally significant drop in blood pressure to preocclusion values. Sectioning both vagi did not abolish this pressor reflex. Denervation of either carotid sinus area abolished the pressor reflexes arising from that side while from the intact side the reflex could still be elicited. Bilateral vagotomy and denervation of the carotid sinuses failed to abolish completely the pressor response produced by carotid occlusion, which lends support to the existence of cephalic baroceptors. The results indicate that swine exhibit cardiovascular reflexes initiated by baroceptor stimulation in the carotid sinus area. However, the sensitivity of the receptors seemed to be below that in some other animal species, i.e. the magnitude of the responses was by no means as great in the pig as in the dog. In every instance, the pressor response elicited by carotid occlusion was accompanied by a significant increase in heart rate, which returned to normal following desocclusion of the artery. Heart rate was also significantly increased by bilateral vagotomy.