Normalization of arterial pressure after barodenervation: role of pressure natriuresis

Studies in several species have demonstrated that mean arterial pressure (MAP) is normal or only slightly elevated after chronic arterial baroreceptor denervation. We hypothesized that the absence of sustained hypertension after barodenervation was the result of a pressure natriuresis response, secondary to sympathetic vasoconstriction of nonrenal vasculature. To test this hypothesis, MAP, sodium balance (NaBal), and water balance were measured before and after aortic baroreceptor denervation (ABD), sinoaortic denervation (SAD), or sham surgery in conscious rats. MAP was increased 20.0 +/- 3.7 mmHg 1 day after ABD but returned to control by day 3. ABD had no significant effect on daily NaBal or water balance. The responses to SAD were similar to those after ABD, with the exception that a significant natriuresis was observed the first day after SAD. However, this was followed by a significant antinatriuresis on day 2, when MAP was still elevated. By day 3 after SAD, MAP, NaBal, and water balance were not significantly different from control. These results suggest that the normalization of MAP after ABD or SAD is not the result of pressure natriuresis but rather failure to maintain a chronic elevation of sympathetic activity after barodenervation.