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

This study investigated the effect of chronic intracerebroventricular (IVT) infusion of a hypertonic NaCl (400 mmol/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 urethane-anaesthetized rats, the pressor response to intravenous infusions of norepinephrine and angiotensin II (Ang II) 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 Ang II. 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 NaCl. 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.