Intravenous ethanol self-administration in C57BL/6J and DBA/2J mice

Two strains of mice, C57BL/6J (B6) and DBA/2J (D2) were allowed to self-administer intravenous (iv) ethanol. These two strains were selected because they differ greatly in their preference for drinking ethanol solutions: B6 mice are preferrers, whereas D2 mice are avoiders of ethanol. Of interest was whether these strains would also differ in self-administration of iv ethanol when taste factors presumably do not influence consumption. Mice were trained with either 60, 75, or 90 mg/kg per infusion. Mice from both strains acquired nose-poking for all of these doses on an FR-3 schedule of reinforcement during 2-hr daily sessions. Additionally, mice in both strains acquired an equal preference for nosepoking on the side resulting in ethanol infusion, compared with the side that had no scheduled consequence, although B6 mice took somewhat more ethanol early in training than did D2 mice. Mice in both strains achieved equal levels of responding at the conclusion of training, when response rates had stabilized. A subset of animals were then tested at doses of ethanol ranging from 25 to 125 mg/kg per infusion. Although their responding tended to decrease over time regardless of changes in the unit dose of ethanol, these mice showed lower response rates for higher doses of ethanol, and less responding for saline than for ethanol. Together, these findings imply that iv ethanol has reinforcing properties in both these strains, despite the strain difference in preference for oral ethanol. Self-administration of iv ethanol in mice may prove a valuable addition to existing animal models for the study of ethanol reward.