Limited access alcohol drinking in high- and low-alcohol preferring selected lines of mice

Background: Selection studies and genetic analyses of drinking behavior in rodents often involved unlimited access to alcohol over a period of weeks, with water and food freely available. Most studies investigating the pharma cology of alcohol drinking, on the other hand, use procedures in which acce ss to alcohol is limited to a particular time each day. Reconciliation of f indings between these two conditions likely depends on their sharing common genetic mechanisms as indicated, for example, by covariation in response t o selection. To this end, high- and low-alcohol preferring (HAP and LAP, re spectively) mice, selected for differences in 24-hr access alcohol drinking over a 4-week period, were subjected to a limited access alcohol drinking protocol. Methods: During 2-hr sessions, mice had access to various concentrations of alcohol (7-15%, v/v) in the home cage for 2 hr a day, with adlibitum acces s to food and water. Additional sessions were conducted with no food presen t. Results: Although both strains consumed alcohol and water during these sess ions, HAP mice drank far more alcohol than did LAP mice. HAP but not LAP mi ce drank alcohol at a high rate early in the session compared with later in the session. Additionally, HAP mice responded to changes in alcohol concen tration, whereas LAP mice did not. Removal of food did not influence alcoho l drinking, although water drinking decreased following food removal. HAP m ice reached appreciable blood alcohol concentrations after limited access. Conclusions: These findings indicate that in these selectively bred mice, a lcohol drinking during limited and unlimited access may be genetically rela ted, and that drinking during limited access sessions in HAP mice is likely for the pharmacological properties of alcohol.