Comparing salt appetites: induction with intracranial hormones or dietary sodium restriction

To raise a natural sodium appetite in the laboratory requires approximately 10 days on a very low sodium diet. Most other regimens induce sodium appetite more rapidly, but also result in behavioral or physiological changes not observed in the deprivation-induced state. We compared the characteristics of need-free sodium appetite induced either by systemic aldosterone combined with an intracerebroventricular (ICV) injection of angiotensin II or by a single ICV injection of renin with an appetite induced by 10 days of sodium deprivation. We measured the latency to drink water and 3% NaCl, as well as the amount of these fluids consumed at 30 min, 3 h, and 24 h. Angiotensin induced the shortest latency for both water and salt drinking, but the overall salt intake was lower. In 24 h, renin and sodium deprivation both induced about 14 ml of NaCl consumption, but the time course of the fluid intake differed for the two regimens.