Effects of drugs on the temporal distribution of schedule-induced polydipsia in rats.

Drinking was induced in food-deprived rats by a fixed-time 1-min schedule of food presentation. With three rats, d-amphetamine (0.25, 0.5, 1.0, and 2.0 mg/kg) led to a dose-related increase in licking early in the interfood intervals, the peak of the temporal distribution of licking being shifted to earlier values. These effects were seen even when d-amphetamine had no effect on overall rates of licking and drinking. With another three rats, however, diazepam (0.5, 1.0, 2.0, and 4.0 mg/kg) did not shift the peak of the temporal distribution of licks in interfood intervals, even at doses that produced small increases in overall rates of licking and drinking. However, diazepam did reduce the peak of the distributions of licks at doses that did not decrease water intake and licks per minute.