Evidence for behavioral sensitization to cocaine in preweanling rat pups

Sought to determine whether promoting context-dependent sensitization might facilitate expression of sensitization in preweanlings. Sprague-Dawley rats were injected daily from postnatal day 14 to postnatal day 20 with 0, 5, 15, or 30 mg/kg cocaine hydrochloride and placed for 30 min in either the experimental chamber or home cage. On postnatal day 21 (test day), Ss were challenged with either 15 mg/kg cocaine or saline prior to placement in the experimental chamber. Significant sensitization of cocaine-induced stereotyped head movements was evident in animals given 15 or 30 mg/kg chronically in the experimental chamber, but not when these same doses were given in the home cage. Less consistent evidence for cocaine-induced sensitization was seen when examining locomotion, although trends for sensitization of this behavior were seen in animals chronically injected in either the test chamber or home cage. Thus, preweanlings can exhibit cocaine sensitization, particularly in terms of stereotypy, when tested shortly after the chronic exposure period, with expression of this sensitization being facilitated by pairing the chronic injections with the test context. ((c) 1998 APA/PsycINFO, all rights reserved)