EFFECTS OF SPINAL SECTION AND RENAL DENERVATION ON THE RENAL RESPONSE TO BLOOD VOLUME EXPANSION

Abstract

Expansion of the blood volume with "artificial blood" infusion, previously shown to cause diuresis and natriuresis in anaesthetized dogs, failed to produce this renal response in chronic high-spinal dogs. This observation was considered best explained as the result of interruption of nervous pathways essential to a reflex mechanism. In other dogs, unilateral renal denervation did not significantly alter the time course of response or the magnitude of the diuresis, but did result in a reduced natriuresis. As there was no qualitative difference between the responses of the innervated and denervated kidneys in each animal, it is concluded that renal motor nerve supply is not involved in the effector limb of the reflex, which must then be humoral. Bilateral renal denervation led to a marked reduction in natriuretic response to infusion and, while not reducing the diuretic response, significantly delayed the maximum increase in urine flow. These effects, like those of spinal section, are attributed to the loss of sensory pathways. The hypothesis is advanced that receptors of extracellular fluid volume with spinal afferent pathways exist in the kidney and also in some extrarenal site, and that their activity is necessary to facilitate response of central nervous centers to increased discharge of receptors of intravascular volume.