Renal sympathetic baroreflex during normoxia and during hypoxia in conscious and in anesthetized rabbits.

The responses of renal sympathetic nerve activity (RSNA) to changes in mean arterial pressure (MAP) during normoxia and hypoxia was studied in conscious rabbits and during anesthesia with pentobarbitone (PB) by determining the RSNA baroreflex curves. In conscious rabbits, the gain in RSNA response was greater and the range of MAP between minimum and maximum levels of RSNA was narrower than in anesthetized rabbits. The renal sympathetic baroreflex was augmented by hypoxia, indicating a central excitatory interaction between the effects of baro- and chemoreceptor stimulation. However, hypoxia produced no significant change in median blood pressure. During anesthesia with PB, resting MAP was decreased, median blood pressure was lowered, and renal sympathetic baroreflexes were less pronounced. Renal sympathetic baroreflex was augmented by hypoxia, and there was a significant increase in median blood pressure. These results provide direct evidence of an inhibitory effect of PB on the response of RSNA to baro- and chemoreceptor stimulation.