REPEATED INTRAVENOUS COCAINE ADMINISTRATION TO RATS PRODUCES BEHAVIORAL SENSITIZATION WITHOUT CHANGING BRAIN COCAINE LEVELS

Repeated intraperitoneal (i.p.) administration of cocaine to rats results in behavioral sensitization. However, augmented brain cocaine levels are also produced by this treatment. In the present study, a 43% increase in cocaine levels was observed in striatum in response to eight once-daily i.p. injections of cocaine (10 mg/kg). It has been suggested that this dispositional change does not occur with intravenous (i.v.) cocaine administration. In agreement with this suggestion, the striatal cocaine levels observed following either a single i.v. injection or eight once-daily i.v. injections of cocaine (1 mg/kg) were similar. Nonetheless, the rats became behaviorally sensitized in response to the repeated i.v. cocaine administration. These results suggest that the increased brain levels of cocaine observed following repeated i.p. cocaine administration cannot completely account for behavioral sensitization.