Central action of sodium chloride on whole body pressor responsiveness in the DOCA-treated rat

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This study investigated the effect of chronic intracerebroventricular (IVT) infusion of a hypertonic NaCI (400mmol/l) artificial cerebrospinal fluid (aCSF) on blood pressure and whole body pressor responsiveness, in control rats (CH) and in rats'implanted with deoxycorticosterone acetate (DOCA; DH). An isotonic aCSF was infused into another group of control (Cl) and DOCA (Dl) rats. Indirect systolic blood pressure (SBP) was measured using a tail-cuff technique once a week prior to and during the infusion period. Following 2 weeks of infusion, SBP increased significantly only in the DH and CH groups. In urethaneanaesthetized rats, the pressor response to intravenous infusions of norepinephrine and angiotensin II (Angll) increased significantly in DH rats. When compared with Cl and Dl rats, those from the CH group also exhibited an enhanced response to norepinephrine and Angll. However, this increase was not as great as in the DH animal. These results show that whole body pressor responses to norepinephrine and Ang II, increase in rats receiving chronic IVT infusion of hypertonic NaCI. These responses coincide with moderate but significant increases in SBP. These data indicate that sodium chloride acts at a central site to increase norepinephrine and Ang II pressor responsiveness in mineralocorticoid hypertension.

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