[Arterial baroreflex in the renal hypertensive rabbits]

In 14 anesthetized male rabbits subjected bilateral renal wrapping 12 weeks before, the baroreflex control of heart rate (HR), hindlimb vascular resistance (HVR) and renal sympathetic nerve activity (RSNA) was examined during arterial baroreceptor loading and unloading by injecting phenylephrine (PE) and nitroprusside (NP). The results were as follows: (1) The mean arterial pressure (131 +/- 9 mmHg) of the kidney-wrapped rabbits was significantly higher than that (95 +/- 10 mmHg) of the control rabbits (P less than 0.001). (2) With the buffer nerves intact, the baroreflex control of HR was obviously impaired in the hypertensive rabbits (P less than 0.01), whereas the reflex control of HVR and RSNA remained unchanged as compared with the normotensive rabbits (P greater than 0.05), indicating a dissociation of baroreflex control of HR from that of peripheral circulation. However, in response to local intraarterial injection of PE and NP, the changes in HVR showed no difference between the hypertensive and normotensive rabbits. (3) After aortic or carotid baroreceptor denervation, the reflex control of HR was further reduced in the hypertensive rabbits, and the reflex control of HVR and RSNA was also significantly reduced (P less than 0.01), suggesting an impairment of potential baroreflex regulation of the circulation. It is likely that the changes of baroreflex in hypertensive rabbits may be attributed to the abnormalities in both baroreceptor and central integrating mechanism.