Contribution of the sympathetic nervous system to salt-sensitivity in lifetime captopril-treated spontaneously hypertensive rats

Objective: To test the hypothesis that, in lifetime captopril-treated spontaneously hypertensive rats (SHR), the sympathetic nervous system contributes importantly to the hypertensive effect of dietary sodium chloride supplementation. Methods: Male SHR (aged 6 weeks) that had been treated from conception onward with either captopril or vehicle remained on a basal sodium chloride diet or were fed a high sodium chloride diet. After 2 weeks, the rats were subjected to ganglionic blockade and 2 days later, an infusion of clonidine. Results: Lifetime captopril treatment significantly lowered mean arterial pressure in both groups. Intravenous infusion of the ganglionic blocker hexamethonium resulted in a rapid decline in MAP that eliminated the dietary sodium chloride-induced increase in MAP in both groups. Infusion of the central nervous system a₂-adrenergic receptor agonist clonidine also resulted in a greater reduction in MAP in both groups of SHR that were fed the high (compared with the basal) sodium chloride diet. Conclusions: In both lifetime captopril-treated and control SHR, the sympathetic nervous system contributes to the pressor effects of a high sodium chloride diet.