Is compensatory vasoconstrictor tone in the hindquarter vascular region induced by hemorrhage in conscious spontaneously hypertensive rats?

We investigated whether a compensatory vasoconstrictor action would be indu ced by a hypotensive intervention in the hindquarter vascular region of con scious spontaneously hypertensive rats (SHRs). Mean arterial pressure and h indquarter blood flow were recorded. After hemorrhage (withdrawing blood, 0 .3 ml/100 g body weight), hindquarter resistance (HQR) was increased signif icantly. The decrease in HQR induced by the administration of a ganglionic blocker (C6; 25 mg/kg, i.v.) was significantly greater in SHRs with hemorrh age than in those without hemorrhage. The present results suggest that a de tectable hindquarter compensator tone occurs due to hemorrhage in SHRs, alt hough an abnormal substantial vasoconstrictor tone already exists in the hi ndquarters.