Effects of glucose-saccharin preloads on schedule- and deprivation-induced drinking in rats.

The present series of experiments found that high volumes of a glucose-saccharin solution consumed by rats prior to testing (i.e., a preload) produced a small, but significant suppression of established schedule-induced drinking (Experiment 2). This reduction in polydipsic drinking did not appear to be due to the caloric value of the preload (Experiment 1) or to any changes in food motivation, since Experiment 2 showed that there were no changes in lever pressing on a fixed-interval 1-min food schedule. In Experiment 3, the glucose-saccharin preloads produced a complete suppression of water deprivation-induced drinking. While schedule-induced drinking does appear to be a nonhomeostatic form of drinking, under certain testing conditions, it is sensitive to manipulations which affect homeostatic thirst mechanisms.