Effects of vasopressin and V1 receptors blockade on blood pressure and heart rate in spontaneously hypertensive rats.

The aim of the present study was to compare effects of intravenous infusion of vasopressin AVP and V1 receptors blockade on blood pressure and heart rate in normotensive (WKY) and spontaneously hypertensive (SHR) rats. A 20 min vasopressin infusion (1.2 ng/kg/min) elicited significantly greater increase in mean blood pressure (MP) in SHR than in WKY. Heart rate was significantly reduced in SHR while nonsignificantly in WKY. A 20 min dEt2 AVP (V1 antagonist) infusion (0.5 microgram/kg/min) elicited significant decrease in MP and increase in heart rate (HR) in SHR, but produced no effect in WKY. The data indicate that SHR are more susceptible to pressor and hypotensive effects of sustained elevation of AVP and AVP antagonist. The results support the hypothesis that AVP may contribute to pathogenesis of hypertension.