Thirst and sodium appetite in Dahl rats

Abstract

In confirmation of a previous study, rats of the Dahl S and R sublines exhibited no spontaneous preference for dilute NaCl solutions and an aversion for isotonic and hypertonic NaCl solutions when they were offered in a 2-bottle choice with water. A hysteresis effect was observed when choice was offered between water and a descending series of concentrations of NaCl solution compared with a preceding increasing series. In response to either chronic dietary administration of an angiotensin I converting enzyme inhibitor (ACEI) or acute sodium depletion, rats of the R subline developed a strong NaCl appetite, but the S subline did not. In contrast, rats of both sublines showed an NaCl appetite in response to a regimen of deoxycorticosterone acetate (DOCA). In acute drinking tests, rats of the S subline drank less water than those of the R subline in response to administration of either isoproterenol, ACEIs, or hypovolemia. Both R and S sublines drank similar amounts of water after SC administration of angiotensins I and II, and hypertonic NaCl. Compared with R rats, S rats had lower plasma renin activity in several of the above conditions, and their decreased thirst and sodium appetite appears to be a direct result of an underactive renin-angiotensin system.