Chronic opioids impair acquisition of both radial maze and Y-maze choice escape.
Chronic morphine impaired acquisition of two dissimilar behavioral tasks. In the radial maze, the performance of saline-treated and morphine-treated groups diverged with the latter failing to improve despite extensive training. In contrast, rats treated with naltrexone became skilled in the procedure 2-4 times as rapidly as saline controls. Withdrawal of treatment significantly improved performance of morphine-treated rats, with no change for rats treated with saline or naltrexone. When a second group of rats was extensively trained prior to instituting chronic morphine treatment, performance scores were not affected, suggesting that morphine does not impair spatial working memory despite subjective evidence of other gross behavioral effects, such as ataxia. In the Y-maze choice escape task, acquisition of a response strategy was significantly impaired in rats that had been previously treated with morphine for 17-21 days, despite clear indications that morphine-treated rats were sensitive to the aversive stimulus.
Spain
J W
JW
Department of Biomedical Sciences, University of Illinois College of Medicine, Rockford 61107.
Newsom
G C
GC
D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects*; D001522:Behavior, Animal / Q000187:drug effects; D003071:Cognition / Q000187:drug effects; D004361:Drug Tolerance; D004597:Electroshock; D007858:Learning / Q000187:drug effects*; D009020:Morphine / Q000494:pharmacology; D009271:Naltrexone / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology*; D051381:Rats; D011930:Reaction Time / Q000187:drug effects; D012684:Sensory Thresholds / Q000187:drug effects; D014828:Vocalization, Animal / Q000187:drug effects
D009294:Narcotics; D009271:Naltrexone; D009020:Morphine