Effects of renal receptor activation on neurosecretory vasopressin cells.

Electrical stimulation of afferent renal nerves (ARN) has been shown to excite neurosecretory vasopressin (AVP) cells of the supraoptic nucleus (SON). To investigate the sensory modality of the ARN involved, the present study examined in pentobarbital-anesthetized rats the responses of putative AVP cells to procedures intended to differentially activate renal receptor populations. Neurosecretory SON cells were identified by antidromic invasion from the neurohypophysis and classified as AVP secreting on the basis of spontaneous activity patterns and responses to arterial baroreceptor activation. Neither elevation of systemic arterial pressure (50-100 mmHg, 9 cells) following sinoaortic and cardiopulmonary afferent nerve transection nor renal venous occlusion (15 cells) altered AVP cell discharge. Renal ischemia, produced by renal arterial occlusion (50-120 s, 14 cells), and renal arterial infusion of adenosine (1-50 micrograms, 8 cells) were also without effect. However, infusions into the renal artery of bradykinin (1-3 micrograms) excited 9/15, of capsaicin (1-3 micrograms) excited 13/15, and of sodium cyanide (5-40 micrograms) excited 1/11 AVP cells examined. These data demonstrate that, in the anesthetized rat, putative neurosecretory AVP cells in the SON are responsive to activation of bradykinin- and capsaicin-sensitive renal receptors and suggest that activation of these receptors contributes to the hormonal regulation of the circulation.