Satiation of thirst and termination of drinking: Roles of plasma osmolality and absorption

Abstract

Experiment I determined the relationship between time spent drinking and decline in rate of intake of thirsty rats, in order to establish an objective criterion for satiation. The satiety criterion derived from the data was: a rat was considered to be satiated if its intake rate declined to 0.2 ml/min or less for 3 consecutive min. In Experiment II, measurements were made of plasma osmotic pressure, plasma volume and postingestional absorption in rats drinking to this criterion. These measurements were made at various stages of adaptation to 23.5 hr water deprivation. Animals with different amounts of adaptation experience drank different amounts, but stopped drinking in roughly equivalent times. They also stopped drinking after similar osmotic pressure decreases, similar postingestional absorption, and without significant vascular volume shifts. The results of Experment III showed that cessation of drinking was coincident with a return of plasma osmolality to approximately ad lib levels. These results strongly support a cellular rehydration interpretation of the termination of drinking. © 1970.