Centrally applied vasopressin intensifies hypotension and bradycardia after hemorrhage in SHR rats

Spontaneuosly hypertensive rats (SHR) have been shown to exhibit several alterations in function of the intrabrain vasopressinergic system. The present study was designed to find out whether centrally administered vasopressin (AVP) may influence the cardiovascular adaptation to hypotensive hypovolemia in SHR rats. Two series of experiments were performed on conscious 17 SHR rats chronically implanted with lateral cerebral ventricle (LCV) cannulas and with femoral artery catheters. Mean arterial pressure (MAP) and heart rate (HR) were monitored before and after arterial bleeding (1,3% body weight) performed during LCV infusion of 1) artificial cerebrospinal fluid 5µl/hour (aCSF); and 2) arginine vasopressin, 100ng/hour/5µl of aCSF (AVP). Central administration of aCSF and AVP had no effect on MAP and HR under resting conditions. Hemorrhage evoked significant hypotension (p<0.001) and bradycardia (p<0.001). During central infusion of AVP hemorrhage resulted in significantly greater hypotension than during central infusion of aCSF alone (p<0,05). The results provide evidence that centrally applied vasopressin significantly modulates cardivascular adjustments to hypotensive hemorrhage in SHR.