Intravenous cocaine priming reinstates cocaine-induced conditioned place preference

Separate groups of rats underwent an unbiased conditioned place preference (CPP) procedure involving alternate pairings of distinct environments with intravenous (IV) injections of cocaine (.75 mg/kg) or saline immediately or 15 min after injection. A subsequent extinction phase consisted of exposure to both conditioning environments preceded by saline injection (Ext). Finally, an IV priming injection of cocaine was administered to reinstate the extinguished place preference (Rein). Time spent in the cocaine-paired chamber significantly increased from Pre-test to CPP, decreased from CPP to Ext and increased from Ext to Rein. The temporal delay had no significant effect on performance across all phases of the study. This study confirms previous studies of reinstatement and extends the route of administration under which reinstatement can be demonstrated by replicating the phenomenon with IV drug administration.