Role of carotid body in pressure response of pulmonary circulation in rats.

We investigated how signals arising from peripheral chemoreceptors could affect pulmonary vasculature in rats. Effects of the hypoxic exposure (10%) on mean pulmonary arterial pressure (mPAP), abdominal aortic flow (Q) and the estimated total pulmonary vascular resistance (mPAP/Q) were determined in anesthetized, artificially ventilated, carotid sinus nerve intact or chemodenervated rats. The pressor response of PAP to hypoxia seen in intact rats changed to the depressor response after chemodenervation. Hypoxia elicited a decrease in Q and an increase in mPAP/Q in both intact and chemodenervated rats. Selective carotid body stimulation by the intra-carotid injection of sodium cyanide (NaCN) in normoxia elicited an immediate but transient increase in PAP and Q before and after bilateral vagotomy. The peak change in PAP slightly preceded that in Q. These responses to NaCN were completely abolished by chemodenervation. These results indicate that the immediate chemoreflex contributes to the short-term regulation of pulmonary vasculature in rats.