Learning and meal-associated drinking: meal-related deficits produce adjustments in postprandial drinking.

Two experiments examined the effect of meal-related water deficits on the distribution of meal-associated drinking. In the first procedure free-feeding rats received 10-, 20-, or 30-min delays between the end of a meal and the subsequent availability of postprandial water. Each delay condition remained in effect for 10 consecutive days. The primary effect of the delay was to postpone the intake of postprandial drinking. None of the delay conditions produced an increase in preprandial drinking. However, when the rats were returned to baseline following the delay conditions a pronounced rebound effect was obtained in the proportion of postprandial drinking. The second experiment followed the same general procedure except that 5-min access to water was always presented after each meal and before the postprandial water restrictions. Under this procedure the rats increased their water intake during the 5-min period when the postprandial restrictions were imposed. These findings show that meal-related water deficits can affect the timing and proportion of postprandial drinking, but provide no evidence that meal-related deficits increase preprandial drinking. The results suggest that the anticipation of meal-related water deficits may play a role in shaping the rat's postprandial drinking pattern.