RAPID DECAY OF COCAINE-INDUCED BEHAVIORAL SENSITIZATION OF LOCOMOTOR BEHAVIOR

Sprague Dawley rats received three daily intraperitoneal (IF) injectio ns of saline or 15 mg/kg cocaine. Following an interval of 2, 5 or 8 d ays, the behavioral response of separate groups of rats to a challenge injection of cocaine (15 mg/kg) was tested in an open held. After rep eated cocaine (15 mg/kg) injection, movement in both the vertical and horizontal plane was increased in cocaine-treated rats 2, but not 5 or 8, days after treatment as compared to saline-treated subjects. In ad dition, behavioral ratings along an ordinal scale designed to reflect increases in behavioral activation were increased in cocaine-treated r ats 2, but not 5 or 8, days after treatment. These results stand in co ntrast to other reports demonstrating long-lasting neural and behavior al changes after similar treatment regimens. Taken together, the resul ts suggest that a treatment regimen of 15 mg/kg per day of cocaine for 3 days produces behavioral sensitization of locomotor behavior; howev er, this cocaine-induced behavioral sensitization does not persist bey ond a few (< 5) days after repeated cocaine treatment, using the curre nt experimental parameters. (C) 1997 Elsevier Science B.V.