Role of afferent renal nerves in the control of vasopressin secretion.

Several lines of evidence indicate that the kidneys can influence the secretion of vasopressin. We have reported that electrical stimulation of the renal nerves increases plasma vasopressin concentration in dogs and rabbits, and other investigators have reported that selective stimulation of afferent renal nerves in cats and rats increases plasma vasopressin concentration or the activity of neurosecretory neurons in the supraoptic nucleus. Intrarenal infusion of bradykinin, which is known to excite afferent renal nerves, has also been reported to increase the activity of putative vasopressin neurons in the supraoptic nucleus of rats. Recently, we observed that intrarenal infusion of bradykinin in rabbits increases plasma vasopressin concentration, and that this response is markedly reduced by renal denervation. We have also reported that activation of renal mechanoreceptors by elevating intrarenal pressure increases plasma vasopressin concentration in rabbits, and that this response is blocked by renal denervation. In order to determine if the kidneys participate in the physiological regulation of vasopressin release, we investigated the effect of renal denervation on the osmotic and non-osmotic control of vasopressin secretion in conscious, chronically-prepared rabbits. We found that renal denervation did not significantly reduce the vasopressin responses to hypertonic saline infusion, 24-hour water deprivation, hemorrhage or nitroprusside infusion. In summary, these observations indicate that the kidneys can influence the secretion of vasopressin via the afferent renal nerves. However, the physiological significance of the observations remains to be determined.