RECOVERY OF ARTERIAL-PRESSURE CONTROL AFTER PARTIAL BARORECEPTOR DENERVATION IN AWAKE RABBITS

We examined recovery of control of heart rate (HR) and total peripheral resistance (TPR) by arterial baroreceptors after bilateral carotid sinus and aortic denervation or unilateral carotid sinus and aortic denervation in conscious rabbits. In one group of animals, HR responses to changes in mean arterial pressure (MAP) after injection of nitroglycerin or phenylephrine were measured in control studies and at 2, 5, 10, and 15 days after partial baroreceptor denervation. All denervation procedures increased MAP and HR at 2 and 5 days after denervation. Reflex sensitivity decreased to 57-67% of control on day 2 after denervation. HR responses recovered by day 10 after bilateral aortic or carotid sinus denervation; however, recovery following unilateral denervation was less complete. In a second group of animals, studied after implantation of aortic flowmeters, TPR changes following reduction in cardiac output by inferior vena caval occlusion were 49% of control responses on day 2 after denervation and returned close to control level on day 5. Controls of HR and TPR recovered substantially and were not significantly different from control 10 days after partial denervation. Recovery apparently occurred through the remaining arterial baroreceptors, possibly due to central reorganization of reflex pathways.