Increased ethanol self-administration after a period of imposed ethanol deprivation in rats trained in a limited access paradigm.

A predominant feature in human alcohol abuse is the reported desire or "craving" to consume ethanol along with frequent episodes of drinking after periods of abstinence. These and other factors may be responsible for relapse to uncontrolled ethanol drinking. When relapse occurs after a period of abstinence, ethanol drinking has been shown to be temporarily increased. Two aspects of drug dependence could contribute to these increases. One may be the development of a need state; the other may involve changes in the perception of the positive reinforcing effects of ethanol when reinforcer access is limited. To investigate this phenomenon further, the present study was conducted to examine in nondependent rats the effect of forced time-off on oral ethanol self-administration in a limited access paradigm (30 min/day). Male Wistar rats were trained to respond for ethanol (10% w/v) or water in a two-lever, free-choice condition using a saccharin fading procedure. After the establishment of stable baseline responding for ethanol, various ethanol deprivation periods (3, 5, 7, 14, or 28 days) were imposed, during which no ethanol was available. Responding for ethanol increased as a function of the duration of the deprivation period when compared with baseline levels. This increase was temporary and returned to baseline levels within 2 to 3 days. Given that the shortest time-off period was 5 days and the rats showed no signs of withdrawal, this transient increase in ethanol responding does not seem to be related to the manifestation of dependence and withdrawal, and may be related to changes in ethanol's reinforcement properties. These results with rats may provide a useful tool to elucidate mechanisms underlying human alcohol seeking behavior and relapse.