Abstracto

Nitric oxide and L-type calcium channel influences the changes in arterial blood pressure induced by central angiotesin II

Wilson Abrao Saad, Ismael Francisco Motta Siqueira Guarda, Luiz Antonio de Arruda, Camargo, Talmir Augusto Faria Brizola dos Santos

This study has determined whether voltage dependent calcium channels are involved inANG II-induced pressor effect bymeans of nitrergicmechanism. We have previously shown the central involvement of angiotensin II (ANGII) in the arterial blood pressure. The antipressor action of L-Type calcium channel antagonist, nifedipine, has been studied when it was injected into the trird ventricle (3rdV) prior toANGII. The influence of nitric oxide (NO) on nifedipine antipressor action has also been studied by utilizingNW-nitro-L-argininemethyl ester (L-NAME) (40g.0.2l-1) a nitric oxide synthase inhibitor (NOSI) and L-arginine (20g.0.2l-1), a nitric oxide donor agent). Rats Holtzman 200-250g, with cannulae implanted into the 3rd Vwere injected withANG II into the 3rd V.MAP increased afterANG II injection. Such increasewas potentiated by the prior injection of L-NAME. Losartan injected into the 3rdV, prior toANG II, blocked the pressor effect of ANGII. PD 123319 decreased the pressor effect of ANGII. Rats pretreated with either 50g.0.2l-1 or 100g.0.2l-1 of nifedipine, followed by 25 pmol.0.2l-1 of ANGII, decreased ANGII-pressor effect. However, LNAME (40g.0.2l-1) potentiated the pressor effect ofANGII, which was blocked by the prior injection of nifedipine and L-arginine (20g.0.2l-1). These data have shown the correlation between L-Type calcium channel and a free radical gas nitric oxide (NO) in the central control of ANG IIinduced pressor effect. This suggests that L-Type calcium channel participates in both short and long term neuronal actions of ANG II with the influence of nitrergic ways.