ROLE OF BARORECEPTORS IN HYPOTENSION AND RENAL SYMPHATHOINHIBITION INDUCED BY BLOCKADE OF THE MEDIAN PREOPTIC NUCLEUS

Abstract

The present study sought to evaluated the autonomic and cardiovascular effects of the MnPO inhibition following the sinoaortic denervation. Male Wistar (WT) rats and spontaneously hypertensive rats (SHR; 250‐300g) were anesthetized (ketamine 100mg.kg‐1, b.wt.; and xylazin 20mg.kg‐1, b.wt.), and submitted to sinoaortic denervation. Femoral artery and vein were catheterized and led subcutaneously to exit between the scapulae. In the following day, animals were anesthetized with urethane (1.2g.kg‐1, b.wt.) and instrumented for recording renal sympathetic nerve activity (RSNA) and for nanoinjections of saline (NaCl; 150 mM) and muscimol (GABAA agonist; 4 mM) into the MnPO. In WT group, the inhibition of the MnPO with muscimol reduced MAP in both sham (n=5) and denervated (17.5±0.8 vs. ‐28.0±6.5 mmHg, respectively; 3min; n=5). This response was maintained throughout the experimental period (‐15.9±2.3 vs. ‐22.5±4.3 mmHg; 30min). The sympathoinhibition induced by inhibition of MnPO were similar between sham (‐23.2±1.8%; 3min) and denervated WT rats (‐22.0±5.2%; 3min). In SHR groups, the blockade of the MnPO also promoted decrease in MAP, however this response was greater in denervated SHR (‐44.7 ± 7.1 mmHg; n=4) compared to the sham (‐21.0 ± 5.6 mmHg; n=5). We also observed similar decrease of RSNA induced by MnPO inhibition in SHR (‐34.9±8.2%; 3min) and denervated SHR (37.5±8.6%; 30min). The results demonstrated that aortic and carotids afferents participate in the modulation of autonomic and cardiovascular responses induced by the blockade of the MnPO.SupportCNPq and FAPEG.