Subchronic cocaine produces training paradigm-dependent learning deficits in laboratory rats

The effect of cocaine on spatial learning was investigated by exposing male Sprague-Dawley rats to 0, 20, or 40 mg/kg cocaine prior to and during trai ning on a water maze task. Half the animals were pretrained on cued trials prior to hidden platform trials, while the remaining animals completed hidd en platform trials immediately. Escape latencies for all animals improved w ith training, but pretrained animals located the hidden platform faster tha n untrained animals (P<.001). Pretraining also decreased the effect of coca ine. In pretrained animals, only the high dose of cocaine caused significan t increases in escape latency (P<.001), while in the untrained group the lo wer dose of cocaine also caused a significant increase (P<.001). On working memory measures, cocaine affected both the pretrained (P<.01) and untraine d (P<.001) groups. Dwell ratio measurements indicated unaffected reference memory in both pretrained (P<.001) and untrained (P<.001) animals, and no s ignificant differences were detected among the treatment conditions in eith er group (P>.05). Thus, while cocaine did not abolish learning, the efficie ncy with which the task was learned was compromised How-ever, this effect w as reduced by pretraining. (C) 2001 Elsevier Science Inc. All rights reserv ed.