A comparison of the motivational properties of thirst induced by intracranial angiotensin and by water deprivation

Abstract

The motivational properties of angiotensin induced thirst (two doses) and water deprivation induced thirst (four levels) were compared. In an ad lib situation angiotensin injected rats drank more rapidly to satiation than water deprived controls. In quinine tolerance tests it was found that: (1) tolerance varied with the level of deprivation; (2) the least deprived group (20 ml overnight ration) resembled the angiotensin injected rats; and, (3) there was no significant difference elicited by 10 and 50 ng doses of angiotensin. In a work test in which the number of bar presses a rat had to make for a single water reward increased with each reward obtained, rats stimulated with angiotensin worked as hard as rats deprived of water for 24 hr. Both groups of rats pressed as many as 64 times for a single reward of 0.1 ml water. These experiments show that angiotensin produces motivated thirst, and that a level of water deprivation that produces comparable motivation can be found. The results support the suggestion that angiotensin may play a role in normal thirst; specifically, it could mediate a hypovolemic component of normal thirst.