Baroreceptors in the carotid sinus contribute to arterial baroreceptor reflexes in normotensive rats.

1. Baroreceptor reflex influences on renal sympathetic nerve activity (RSNA) were estimated with non-linear regression analysis (sigmoidal curve fitting) before and after transection of carotid sinus nerves (CSN) and aortic depressor nerves (ADN) in rats. 2. Transection of ADN reduced the gain of the reflex to 42% of basal levels with increases in arterial pressure (MAP) and RSNA. Subsequent transection of CSN eliminated the remaining sigmoidal correlation between MAP and RSNA without further changes in resting MAP and RSNA. 3. By comparison, the transection of CSN reduced the gain of the reflex to 53% of basal levels without affecting other variables. Additional transection of both ADN eliminated the remaining sigmoidal correlation between MAP and RSNA with further increases in resting MAP and RSNA. 4. These results indicate that carotid sinus baroreceptors exist in rats. They contribute to baroreceptor-mediated reflex changes in RSNA as do aortic baroreceptors, although the working range of MAP may increase with transection of the latter.