Central angiotensin II induces sodium bicarbonate intake in the rat

The aim of this work was to test mineral preference in hydrated rats that received a pulse intracerebroventricular (icvp) injection of ANG II at a dipsogenic dose (50 ng). The icvp ANG II induced a four-fold higher ingestion of 0.15 M NaHCO3 than of other mineral solutions at palatable concentrations (0.15 M NaCl, 0.05 mM CaCl2 and 0.01 M KCl) in a five-bottle test with water available in a fifth bottle; water intake was not consistently high in this test. Contrary to what is predicted by the mineralocorticoid/angiotensin II synergy hypothesis, the 0.15 M NaCl intake in the five-bottle test was not enhanced by icvp ANG II preceded by deoxycorticosterone (DOCA) treatment (2.5 mg/day for 3 days); neither was the NaHCO3 intake. This result contrasted with the vigorous ingestion of both isotonic sodium solutions, but mostly of NaCl, rather than of other fluids, by sodium-depleted (furosemide 10 mg sc + 24 h removal ambient sodium) rats in a sodium appetite test. The results suggest that mineralocorticoid combined to icvp ANG II does not simulate the sodium preference shown during sodium appetite. The results also show that a dipsogenic dose of central ANG II induces a reliable ingestion of isotonic sodium bicarbonate in the rat.