Abstract
We study the voltage dependent calcium channels and nitric oxide involvement in angiotensin II-induced pressor effect. The antipressor action of L-Type calcium channel antagonist, nifedipine, has been studied when it was injected into the third ventricle prior to angiotensin II. The influence of nitric oxide on nifedipine antipressor action has also been studied by utilizing NW-nitro-L-arginine methyl ester (LNAME) (40 μg/0.2 μl) a nitric oxide synthase inhibitor and L-arginine (20 μg/0.2 μl), a nitric oxide donor agent. Adult male Holtzman rats weighting 200–250 g, with cannulae implanted into the third ventricle were injected with angiotensin II. Angiotensin II produced an elevation in mean arterial pressure and a decreased in heart rate. Such effects were potentiated by the prior injection of LNAME. L-arginine and nifedipine blocked the effects of angiotensin II. These data showed the involvement of L-Type calcium channel and a free radical gas nitric oxide in the central control of angiotensin II-induced pressor effect. This suggested that L-Type calcium channel of the circunventricular structures of central nervous system participated in both short and long term neuronal actions of ANG II with the influence of nitrergic system.
Highlights
Nitric oxide plays an important role in the hydromineral and cardiovascular regulation and influence several central angiotensin physiological parameters [1,2]
Effects of nifedipine and L-arginine on the mean arterial pressure and heart rate induced by the injection of angiotensin II into the third ventricle Figure 2, 3
Nifedipine 50 μg injected into the third ventricle followed by angiotensin II decreased the pressor effect (∆11 ± 1 mmHg p < 0.01) with a decreased in heart rate ∆-10 ± 2 bpm p < 0.01)
Summary
Nitric oxide plays an important role in the hydromineral and cardiovascular regulation and influence several central angiotensin physiological parameters [1,2]. LNAME increases blood pressure which is at least in part salt sensitive [3]. The interaction between nifedipine (L-Type calcium channel blocked agent) and nitrergic system of the circumventricular third ventricle structures of the central nervous system on the angiotensin II cardiovascular regulation has not been demonstrated. The subfornical organ is an important circumventricular structure of the central nervous system that participated in the regulation of body fluid homeostasis [5,6,7]. LNAME significantly increased the discharge of neurons of the (page number not for citation purposes)
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