Inhibition of central angiotensin II-induced pressor responses by hydrogen peroxide

Hydrogen peroxide (H(2)O(2)) important reactive oxygen species produced endogenously, may have different physiological actions The superoxide anion (O(2)(-)) is suggested to be part of the signaling mechanisms activated by angiotensin II (ANG II) and central virus mediated overexpression of the enzyme superoxide dismutase (that dismutates O(2)(-) to H(2)O(2)) reduces pressor and dipsogenic responses to central ANG II Whether this result might reflect elevation of H(2)O(2) rather than depletion of O(2)(-) has not been addressed Here we investigated the effects of H(2)O(2) injected intracerebroventricularly (i c v) or ATZ (3-amino-1 2 4 triazole, a catalase inhibitor) injected intravenously (i v) or i c v on the pressor responses induced by i c v injections of ANG II Normotensive male Holtzman rats (280-320 g n=5-13/group) with stainless steel cannulas implanted in the lateral ventricle were used Prior injection of H(2)O(2) (5 mu mol/1 mu l) or ATZ (5 nmol/1 mu l) i c v almost abolished the pressor responses induced by ANG II (50 nmol/1 mu l) also injected ic v (7+/-3 and 5+/-3 mm Hg, respectively, vs control 19+/-4 mm Hg) Injection of ATZ (3 6 mmol/kg b wt) i v also reduced central ANG II induced pressor responses Injections of H(2)O(2) c v and ATZ i c v or I v alone produced no effect on base line arterial pressure Central ANG II, H(2)O(2) or ATZ did not affect heart rate The results show that central injections of H(2)O(2) and central or peripheral injections of ATZ reduced the pressor responses induced by i c v ANG II, suggesting that exogenous or endogenous H(2)O(2) may inhibit central pressor mechanisms activated by ANG II (C) 2010 IBRO Published by Elsevier Ltd All rights reserved