Duration of sensitization to the locomotor stimulant effects of ethanol in mice.

Behavioral sensitization to the psychomotor stimulant effects of some drugs can be quite persistent, lasting for weeks to months after cessation of drug exposure. We investigated the duration of sensitization to the locomotor stimulant effects of 2.0 g/kg ethanol (EtOH) and determined whether repeated EtOH administration would lead to alterations in blood EtOH clearance rates. Female mice were injected (IP) daily for up to 10 consecutive days with saline or EtOH. Baseline activity and acute EtOH locomotor responses were evaluated in Omnitech automated activity monitors (10-min test), with horizontal distance traveled as the measure of locomotion. Locomotor activity response to EtOH was reevaluated immediately after the final daily EtOH injection, and at 5-day intervals during which no EtOH was administered. Tail blood samples for determination of blood ethanol concentrations (BECs) were collected from EtOH-treated mice at the end of activity sessions. Sensitization lasted for up to 29 days, and in two of three of the behavioral sensitization studies, repeated EtOH treatment resulted in elevated BECs. There was no significant effect of repeated EtOH exposure on EtOH clearance rate in a study involving no behavioral testing. The demonstration of persistent behavioral sensitization may imply a lasting hypersensitivity of certain neural pathways to EtOH, thus increasing the reinforcing value of EtOH and the probability of relapse to EtOH drinking after abstinence.