Background: The alcohol deprivation effect (ADE) is a temporary increase in the ratio of ethanol/total fluid intake and the voluntary intake of ethanol solutions over baseline drinking conditions when ethanol access is reinstated after a period of alcohol deprivation. The ADE has been posited to be an animal model for alcohol craving. The current study examined the effects of initial deprivation length and number of deprivation exposures on the ADE in alcohol-preferring (P) rats.
Methods: Adult female P rats received 24-hr free-choice access to 10% (v/v) ethanol and water for 6 weeks. Rats were then randomly assigned to five groups deprived of ethanol for 0 (control), 2, 4, 6, or 8 weeks (W). All deprived groups were then given 24-hr access to ethanol for 2 weeks before being deprived of ethanol for another 2 weeks.
Results: After the initial ethanol deprivation period, the deprived groups displayed a similar 2-fold ADE (e.g., 4-W group; 4.6 +/- 0.5 for baseline vs. 10.5 +/- 0.3 g/kg/day for the 1st reinstatement day) during the initial 24-hr period. Ethanol consumption began to return to control levels 48 (7.1 +/- 0.4 g/kg/day) and 72 (6.4 +/- 0.4 g/kg/day) hrs later. In addition, each deprived group showed increases in the ratio of ethanol/total fluid intake upon reinstatement, and there was a tendency for sustained higher ethanol intake ratios during the first 3 postexposure days for the 4-, 6-, and 8-W groups, but only during the first 2 reinstatement days for the 2-W group. The second deprivation did not increase the magnitude of the ADE over that observed in the first deprivation during the initial 24-hr period of re-exposure, but it did prolong the duration of the ADE into the 2nd and 3rd reinstatement day for the 2-, 4-, and 6-W groups and into the 5th reinstatement day for the 8-W group.
Conclusions: Equivalent robust ADEs can be seen in P rats with deprivation periods of 2-8 W, which suggests that the ADE has a rapid onset and is not affected by the durations of deprivation that were tested. The duration of the ADE was prolonged in P rats exposed to a second deprivation period, suggesting that factors associated with the ADE phenomenon could be strengthened by repeated deprivations.