Authors: Cynthia A Crawford Shelley A Baella Cristal M Farley Matthew S Herbert Leslie R Horn Rachel H Campbell Arturo R Zavala
Publish Date: 2010/09/17
Volume: 213, Issue: 1, Pages: 43-52
Abstract
Previous studies in rodents show that early exposure to methylphenidate alters later responsiveness to drugs of abuse An interesting feature of these studies is that early methylphenidate treatment decreases the rewarding value of cocaine when measured by conditioned place preference CPP but the same treatment increases cocaine selfadministrationRats were treated with methylphenidate 0 2 or 5 mg/kg from postnatal days PDs 11 to 20 and then cocaineinduced CPP or cocaine selfadministration was measured in separate groups of rats in adulthood The CPP procedure included 8 days of acquisition training 8 days of extinction training and a reinstatement test Rats were conditioned with 0 10 or 20 mg/kg cocaine Reinstatement was assessed after a priming dose of cocaine 10 mg/kg For the selfadministration experiment a jugular catheter was implanted and rats were trained to press a lever reinforced with cocaine 025 or 075 mg/kg/infusion on a fixed ratio FR one schedule Rats were gradually moved from an FR1 to an FR10 schedule and after criterion was reached rats were placed on a progressive ratio schedule for 5 daysCocaine produced robust rewarding effects as determined by both the CPP and selfadministration experiments however early methylphenidate exposure only enhanced the reinforcing effects of cocaine on the selfadministration paradigm Interestingly this methylphenidate enhancement was only seen in male rats
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