Effect of post-training administration of cocaine, diazepam and their combination on a win-stay task

Abstract

According to the memory-enhancing hypothesis of addictive drugs, post-training administration of cocaine should enhance consolidation and thus facilitate learning. This hypothesis has not been tested in appetitive tasks reinforced by sucrose.The current study assessed the effect of post-training cocaine administration on the acquisition of a win-stay task, and modulation of this effect by co-administration of diazepam. Male Sprague–Dawley rats (n=63) were trained for 5days on a win-stay task performed on an 8-arm radial maze, and were administered cocaine (0, 2.5, 7.5 or 20mg/kg), diazepam (1mg/kg), or cocaine (7.5mg/kg)+diazepam (1mg/kg) immediately following each training session. Post-training cocaine caused dose-dependent impairments that appeared linked to the development of cocaine-induced sucrose taste avoidance and/or cocaine-induced anxiety. When it was attempted to modify these learned side effects of cocaine by co-administration of diazepam, it was observed that the drug combination slowed task completion and reduced overall number of nose pokes.These findings suggest that post-training cocaine can alter behavior on appetitive tasks through learned motivational deficits rather than through a selective action on memory consolidation. The implications for the memory-enhancing hypothesis of addictive drugs are discussed.