Effects of repeated alcohol deprivations on operant ethanol self-administration by alcohol-preferring (P) rats.

We reported that repeated alcohol deprivations prolonged the expression of an alcohol-deprivation effect (ADE) under 24-h free-choice alcohol-drinking access and that the duration of the initial deprivation period had a positive effect of prolonging the duration of the ADE. In the present study, operant techniques (including progressive ratio measures) were used to examine the effects of initial deprivation length and number of deprivation cycles on the magnitude and duration of the ADE in alcohol-preferring (P) rats to test the hypothesis that repeated deprivations can increase the reinforcing effects of ethanol (ETOH). Adult male P rats were trained in two-lever operant chambers to self-administer 15% ETOH (v/v) on a fixed-ratio 5 (FR-5) and water on a FR-1 schedule of reinforcement in daily 1-h sessions. Following 6 weeks of daily 1-h sessions, the P rats were randomly assigned to one of four groups (n=10/group): nondeprived or deprived of alcohol for 2, 5, or 8 weeks. Following this initial period, the deprived groups were given 15% ETOH again in the operant chambers for a 2-week period, following which they were deprived again for 2 weeks (all three deprived groups). Following the fourth deprivation, the rats underwent a progressive ratio test to determine the breakpoints (FR values) for the nondeprived and the deprived groups. Repeated deprivations increased both the magnitude and duration of the ADE as indicated by increased responding on the ETOH lever. However, the length of the initial deprivation had little effect on expression of the ADE except following the first deprivation, where an ADE was not observed for the 8-week group. Breakpoint values for responding on the ETOH lever for all three deprived groups were two-fold higher than the value for the nondeprived group. The results suggest that repeated cycles of alcohol deprivation and alcohol access increased the reinforcing effects of ETOH in the P rats.