Central ANP attenuates pressor responses to central AVP in WKY and SHR.

Blood pressure and heart rate responses to intracerebroventricular (ICV) injections of atrial natriuretic peptide (ANP, 125 ng) arginine vasopressin (AVP, 10 ng), combination of ANP (125 ng) and AVP (10 ng) or artificial cerebrospinal fluid (acsf, 5 microliters) were compared in conscious normotensive (WKY) and spontaneously hypertensive (SHR) rats. In both strains, ICV injection of AVP elicited significant increase of mean blood pressure (MP) and heart rate (HR). Increase of MP but not of HR was significantly greater in SHR than in WKY (p less than 0.05). Injection of acsf or ANP, as well as simultaneous administration of ANP and AVP, did not elicit significant changes of MP either in WKY or in SHR. In SHR, HR was significantly elevated by ICV injections of AVP and ANP + AVP, whereas in WKY HR was increased only after AVP. The data suggest that interaction of ANP and AVP at a central level may result in significant attenuation of central pressor effects of vasopressin.