Effects of selected opioid agonists and antagonists on DMT-and LSD-25-induced disruption of food-rewarded bar pressing behavior in the rat

✍ Scribed by Diane M. Ruffing; Edward F. Domino

• Publisher: Springer
• Year: 1981
• Tongue: English
• Weight: 564 KB
• Volume: 75
• Category: Article
• ISSN: 0033-3158
• DOI: 10.1007/bf00432428

✦ Synopsis

Several opioid agonists and antagonists interact with N,N-dimethyltryptamine (DMT) and lysergic acid diethylamide-25 (LSD) in adult male Hottzman rats trained on a positive reinforcement, fixed ratio 4 (FR4) behavioral schedule, i.e., a reward of 0.01 ml sugar-sweetened milk was earned on every fourth bar press. DMT (3.2 and 10.0 mg/kg) and LSD (0.1 mg/kg) given IP with 0.9 % NaC1 pretreatment, disrupted food-rewarded FR4 bar pressing. Animals were pretreated IP (10-15 min) with predetermined, behaviorally noneffective doses of morphine, methadone, naltrexone, and the (+)-and (-)-enantiomers of naloxone prior,to receiving DMT or LSD. Dose-dependent effects wereshown with opioid agonist pretreatment. Morphine (0.32-1.0 mg/kg) and methadone (0.32 mg/kg) significantly antagonized the bar pressing disruption induced by DMT and LSD. Larger doses of morphine (3.2mg/kg) and methadone (1.0-3.2 mg/kg) potentiated only LSD-induced effects, with no effect on DMT-treatedgroups. The opioid antagonists (-)naloxone and naltrexone potentiated the disruption of bar pressing induced by DMT and LSD. Failure of (+)-naloxone to potentiate the DMT effects was attributed to a stereospecific opioid antagonist effect of (-)-naloxone.