Antagonism of vasopressin V1 receptors in NTS attenuates baroreflex control of renal nerve activity.

Abstract

Previous work has shown that arginine vasopressin (AVP) present in the nucleus tractus solitarius (NTS) contributes to the control of peripheral cardiovascular parameters such as arterial pressure, heart rate, and sympathetic activity. In this study, we attempted to elucidate the influence of AVP in the NTS on baroreflex control of mean arterial pressure (MAP) and renal sympathetic nerve activity (RSNA) in urethan-anesthetized rats. To test the baroreflex, the aortic depressor nerve (ADN) was stimulated over a range of frequencies (1-15 Hz) to produce frequency-response curves for MAP and RSNA. The vasopressin V1-receptor antagonist [d(CH2)5Tyr(Me)]AVP (aAVP) was microinjected bilaterally or unilaterally into the caudal NTS to eliminate the influence of endogenous AVP on decreases in MAP and RSNA elicited by ADN stimulation. Bilateral microinjection of 10 or 100 ng aAVP significantly attenuated the decreases in RSNA elicited by ADN stimulation. Decreases in MAP were only attenuated following bilateral microinjection of 100 ng aAVP. Unilateral microinjection of the same doses of aAVP did not influence baroreflex control of MAP or RSNA. These results indicate that endogenous AVP within the NTS contributes to cardiovascular regulation. They also suggest that AVP within the NTS may specifically influence baroreflex control of RSNA.