Assessment of autonomic and non-autonomic components of resting hindlimb vascular resistance and reactivity to pressor substances in renal hypertensive rabbits.

1. Hindlimb vascular resistance (HVR) was measured before and after pharmacological autonomic blockade in unanesthetized renal cellophan-wrap hypertensive or normotensive rabbits with previously implanted Doppler ultrasonic flowmeters. 2. When the blood pressure was restored to resting values after autonomic block, the elevated resting HVR in the hypertensive rabbits was entirely accounted for by an increased non-autonomic component (i.e. HVR after block). If the pressure was not restored after block the autonomic component (i.e. resting HVR minus non-autonomic HVR) was overestimated and the non-autonomic component was underestimated. 3. During maximum vasodilatation the minimum HVR was significantly higher in the hypertensive rabbits than in the normotensive group, probably due to structural differences of resistance vessels. 4. Reactivity of the hindlimb bed to noradrenaline, angiotensin II and vasopressin injections was approximately twice as great in the hypertensive rabbits as in the sham-operated group, probably as a consequence of the structural changes.