Influence of circulating angiotensin II and vasopressin on neurons of the nucleus of the solitary tract

The central cardiovascular effects of the circulating peptides angiotensin II (ANG II) and arginine vasopressin (AVP) may be mediated through the nucleus of the solitary tract (NTS). In this study, we used single-unit extracellular recording techniques to determine the effects of peripheral infusions of ANG II and AVP on NTS neurons. Barosensitive NTS neurons were characterized by their response to an increase in arterial pressure induced with phenylephrine (PE). Of 74 NTS neurons, 17 were excited by ANG II infusion. Of these, nine were also excited by activation of baroreceptors. ANG II inhibited 15 of 74 neurons, 13 of which were also baroinhibited. Of 77 NTS neurons, 13 were excited by AVP infusion, 7 of which were also baroexcited. One AVP-excited neuron was inhibited by a PE-induced increase in arterial pressure. Of 77 neurons, 21 were inhibited by AVP, 10 of which were also baroinhibited. Out of 21 AVP-inhibited neurons, 2 were excited by an increase in arterial pressure. These results indicate that some barosensitive NTS neurons may be independently influenced by circulating peptides and that separate populations of barosensitive and peptide-sensitive neurons are found in the NTS.