Conditioning trial duration affects ethanol-induced conditioned place preference in mice

The present experiments were designed to determine the effect of conditioning trial duration on strength of ethanol-induced conditioned place preference in mice. In a counterbalanced, differential conditioning procedure, DBAI2J mice received four pairings of a distinctive tactile (floor) stimulus with injection of ethanol (2 g/kg); a different floor stimulus was paired with saline. Different groups were exposed to the floor stimuli for 5, 15, or 30 min after injection. Conditioned place preference was inversely related to trial duration, with mice in the 5-, 15-, and 30-mmn groups, spending 83%, 74%, and 66% of their time, respectively, on the ethanol-paired floor during a choice test. This outcome was replicated in a second experiment, which also showed that context familiarity can influence conditioned place preference. In general, these findings suggest that ethanol's rewarding effect is greatest shortly after injection.