Sensitization to cocaine's reinforcing effects produced by various cocainepretreatment regimens in rats

A number of studies have demonstrated sensitization to the behavioral effec ts of cocaine following pretreatment. In most cases, pretreatments have bee n administered in the test environment. The present study determined the ef fects of home-cage administrations of cocaine on thr acquisition of cocaine self-administration. Initial groups established that the latency to acquis ition of cocaine self-administration varied inversely with dose. The effect of cocaine pretreatment on latency to acquisition of cocaine self-administ ration (0.25 mg/kg/infusion) was then determined in other groups. On each o f 5 pretreatment days, separate groups received homecage administrations of cocaine as either a single injection (20.0 mg/kg), or two (20.0 mg/kg) or three (10.0 mg/kg) injections separated by 1 h. Testing commenced 3 days fo llowing the last of the pretreatments. only the pretreatment consisting of two daily injections of 20.0 mg/kg cocaine decreased the latency to acquisi tion of self-administration. These data are consistent with a sensitized re sponse to cocaine's reinforcing effects and provide minimum pretreatment co nditions for its development. (C) 2000 Elsevier Science Inc.