Effect of Chronic Administration of Deoxycorticosterone Acetate on Salt Appetite of Captopril-Treated Rats*

Chronic dietary administration of the angiotensin I-converting enzyme inhibitor, captopril (1.0 g/kg food), induced an appetite for 0.15 M NaCl solution relative to distilled water in a two-bottle ad libitum access paradigm. Graded doses of deoxycorticosterone acetate (DOCA) were administered to the captopril-treated rats via Silastic tubes implanted sc. A U-shaped dose-response relationship was observed between dose of DOCA and intake of 0.15 M NaCl solution. The lowest intake of NaCl occurred with a dose of 102.1 micrograms DOCA/day (333 micrograms/kg X day). Water and food intakes were not affected significantly. At the end of the first week of treatment with DOCA, pilocarpine (3.0 mg/kg, ip.)-stimulated salivary chloride concentration was measured. The relationship between salivary chloride concentration and mean intake of 0.15 M NaCl solution was also U shaped, with the minimal NaCl intake associated with a salivary chloride concentration of 54 meq/liter. During the second week of treatment with DOCA, all rats were offered a choice between 0.25 M NaCl solution and distilled water. Rats receiving DOCA at doses of 102.1 micrograms/day or greater had a significantly lower intake of NaCl solution than those receiving either captopril alone or 66.5 micrograms DOCA/day in combination with captopril. These results indicate that the appetite for NaCl solution induced by captopril can be inhibited by concurrent administration of DOCA. They also suggest that changes in the concentration of electrolytes in saliva may be associated with changes in the appetite for NaCl solution.