Sinoaortic baroreceptors and the control of blood volume in the nonhuman primate

The purpose of this study was to determine the role of the aortic and carotid baroreceptors in regulating blood volume in the conscious nonhuman primate. Eighteen control animals were surgically instrumented to permit the recording of blood pressure, pulse rate, and left atrial pressure. After a urethral catheter was inserted into the bladder, the animals were given an intravenous infusion equal to 20% of the estimated blood volume. Renal function was determined before and after the volume expansion. Nine monkeys received the same infusion after undergoing chronic sinoaortic denervation. The denervated animals responded with a potentiated diuresis and natriuresis. The control animals excreted 24% of the infused volume and 4% of the infused salt while the sinoaortic-denervated animals excreted a volume equal to 113% of that infused and an amount of sodium equal to 46% of that infused. We conclude that high-pressure receptors exert an inhibitory influence on whatever mechanisms are involved in the renal response to acute volume expansion.