Effect of dexamethasone on cardiovascular response induced by norepinephrine in nucleus tractus solitarii

AIM: To study the effect of dexamethasone on cardiovascular response induced by norepinephrine (NE) in nucleus tractus solitarii (NTS). METHODS: The variations of cardiovascular action caused by these drugs were observed after injection of mifepristone (Mif), dexamethasone (Dex), bicuculline (Bic), and NE into the medial and intermediate NTS. RESULTS: Microinjection of Dex (0.39 mmol.L-1, 0.1 mu L) into the medial and intermediate NTS abolished the vasodepressed response to NE (8 mmol.L-1, 0.1 mu L) microinjected into the same area 10 min later, and the inhibition did not disappear until 4 h. The rapid inhibitory effects of Dex on NE vasodepression was not antagonized by Mif (4.66 mu mol.L-1, 0.1 mu L), but it was blocked by Bic (3.24 mu mol.L-1, 0.1 mu L). CONCLUSION: Dex abolished cardiovascular response to NE microinjected into NTS which may be mediated by GABA(A) receptor.