ATRIAL-NATRIURETIC-PEPTIDE REGULATION OF NORADRENALINE RELEASE IN THEANTERIOR HYPOTHALAMIC AREA OF SPONTANEOUSLY HYPERTENSIVE RATS

In spontaneously hypertensive rats (SHR), high NaCl diets increase art erial pressure and sympathetic nervous system activity by decreasing n oradrenaline release in the anterior hypothalamic area (AHA), thereby reducing the activation of sympathoinhibitory neurons in AHA. Atrial n atriuretic peptide (ANP) can inhibit the release of noradrenaline, and ANP concentration is elevated in the AHA of SHR. The present study te sts the hypothesis that in SHR, local ANP inhibits noradrenaline relea se from nerve terminals in AHA. Male SHR fed a basal or high NaCl diet for 2 wk and normotensive Wistar Kyoto rats (WKY) fed a basal NaCl di et were studied. In SHR on the basal diet, microperfusion of exogenous ANP into the AHA elicited a dose-related decrease in the concentratio n of the major noradrenaline metabolite 3-methoxy-4-hydroxy-phenylglyc ol (MOPEG) in the AHA; this effect was attenuated in the other two gro ups. In a subsequent study, the ANP-C (clearance) receptor agonist c-A NP was microperfused into the AHA to increase extracellular concentrat ion of endogenous ANP in AHA. c-ANP reduced AHA MOPEG concentration in SHR on the basal NaCl diet but not in the other two groups, These dat a support the hypothesis that local ANP inhibits noradrenaline release in the AHA and thereby contributes to NaCl-sensitive hypertension in SHR.