The alcohol deprivation effect model for studying relapse behavior: a comparison between rats and mice.

Understanding the psychological mechanisms and underlying neurobiology of relapse behavior is essential for improving the treatment of addiction. Because the neurobiology of relapse behavior cannot be well studied in patients, we must rely on appropriate animal models. The alcohol deprivation effect (ADE) is a phenomenon in laboratory animals that models a relapse-like drinking situation, providing excellent face and predictive validity. In rodents, relapse-like behavior is largely influenced by the genetic make-up of an animal. It is not clear which other factors are responsible for variability of this behavior, but there seems to be no correlation between levels of baseline alcohol intake and the occurrence, duration, and robustness of the ADE. Rats that undergo long-term alcohol drinking for several months with repeated deprivation phases develop a compulsive drinking behavior during a relapse situation, characterized by insensitivity to taste adulteration with quinine, a loss of circadian drinking patterns during relapse-like drinking, and a shift toward drinking highly concentrated alcohol solutions to rapidly increase blood alcohol concentrations and achieve intoxication. Some mouse strains also exhibit an ADE, but this is usually of shorter duration than in rats. However, compulsive drinking in mice during a relapse situation has yet to be demonstrated. We extend our review section with original data showing that during long-term alcohol consumption, mice show a decline in alcohol intake, and the ADE fades with repeated deprivation phases. Furthermore, anti-relapse compounds that produce reliable effects on the ADE in rats produce paradoxical effects in mice. We conclude that the rat provides a better model system to study alcohol relapse and putative anti-relapse compounds.