Prior episodes of sodium depletion increase the need-free sodium intake of the rat.

Prior episodes of sodium depletion increase the daily 3% NaCl intake of rats. They ingest large volumes and continue to do so for as long as 3 months after recovery from sodium deficit while eating sodium-rich food and while plasma sodium concentration and renal function are normal. The increased daily intake of sodium is, therefore, need-free. There is a marked sex difference in the need-free intake of 3% NaCl. Female rats drink more salt than do male rats when they are sodium replete and depletion naive. Repeated depletions raise the need-free intakes of both sexes but the effect is greater in females. Plasma concentrations of angiotensin II and aldosterone, which are markedly elevated by each episode of sodium depletion, return to basal levels between and after depletions, and are not the cause of the chronically increased need-free salt intake of the multi-depleted rat. These results suggest that the persistent increase in daily 3% NaCl intake that occurs in the rat with a history of repeated sodium depletions is a permanent, nonpathological increase in avidity for the taste of salty substances that results in life-long overconsumption of salt.