Cardiopulmonary and sinoaortic baroreceptors and volume expansion in the monkey

Experiments were performed to determine the effect of combined cardiopulmonary and and sinoaortic baroreceptor denervation on the renal responses of the anesthetized nonhuman primate to acute intravascular volume expansion. Adult male Macaca fascicularis monkeys underwent chronic bilateral thoracic sympathectomy (middle cervical ganglion--T6) or sham surgery performed in two stages. After a 1-3 week recovery period, each animal was anesthetized with sodium pentobarbital and subjected to cervical vagotomy--sinoaortic denervation or further sham denervation. Estimated blood volume was then acutely expanded 20% with 6% dextran in isotonic saline. Control renal excretory function did not differ between the two groups, and both groups had similar increases in urine flow, sodium excretion, osmolar clearance, free water clearance and renal plasma flow after volume expansion. The patterns of the responses showed some group differences in that the increases in renal excretion after volume-loading had an earlier onset in the denervated animals. These results demonstrate that combined ablation of thoracic sympathetic, vagal and sinoaortic neural pathways does not compromise the ability of the nonhuman primate to increase salt and water excretion when blood volume is acutely expanded. Therefore, these neural mechanisms are not necessary for eliciting the renal responses to this hypervolemic stimulus in this species during the anesthetized state.