Effect of vagotomy and thoracic sympathectomy on responses of the monkey to water immersion.

Cardiopulmonary stretch receptors have been implicated as part of a reflex mechanism linking changes in blood volume to changes in renal excretion. Experiments were performed to determine whether total denervation of these receptors by combined cervical vagotomy and thoracic sympathectomy affects the renal responses of the monkey to head-out water immersion, a maneuver that translocates blood to the thorax and elicits an increase in renal salt and water excretion. Macaca fascicularis monkeys first underwent chronic bilateral thoracic sympathectomy or sham denervation performed in two stages a week apart. One to two weeks later, they were anesthetized with pentobarbital sodium, and the sympathectomized animals underwent bilateral cervical vagotomy. Control renal function did not differ between the two groups. Immersion of 90-min duration increased central venous and mean arterial pressures by similar amounts in both groups, but heart rate increased only in the sham-denervated animals. Denervation did not affect the magnitudes or delay the times of onset of the increases in urine flow, absolute and fractional sodium excretion, and osmolar and free water clearances occurring with immersion. These results demonstrate that in the anesthetized monkey cardiopulmonary receptors are not necessary for eliciting the renal responses to immersion.