Body fluid balance, taste, and post-prandial factors in schedule-induced polydipsia.

Abstract

Schedule-induced polytiipsia did not develop in hungry rats given vegetable oil on a VI reinforcement schedule, but appeared when dry food pellets were used. Analyses of plasma and muscle samples indicated that drinking continued in polydipsic rats despite the dilution and overhy-dration of body fluids and tissues. Thirst due to tissue water needs thus seems neither necessary nor sufficient in explaining polydipsia. Postprandial effects such as dry mouth are probably an important factor in producing polydipsia. These effects are ordinarily subordinate to the hunger drive, but become apparent when feeding is unfavorable interrupted and Ss [subjects] learn to use the intervals between pellet delivery to reduce this motivation by drinking.