Apparent analgesic effects of morphine in chickens may be confounded by motor deficits.
Three experiments were conducted with chickens to examine the effects of morphine on nociception and motor coordination. In Experiment 1, using shock-elicited vocalization as an index of pain, doses of 5, 20, and 30 mg/kg of morphine failed to affect vocalization thresholds. In the second experiment, 30 mg/kg of morphine failed to affect vocalization thresholds at varying times since injection. In Experiment 3, 30 mg/kg of morphine significantly impaired movement in response to nonaversive stimulation. These results show that previous evidence for an analgesic effect of morphine in chickens may have been due to morphine effects on motor initiation and/or coordination.
D000818:Animals; D001143:Arousal / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004597:Electroshock; D007274:Injections, Intraperitoneal; D009020:Morphine / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects*; D009048:Motor Skills / Q000187:drug effects*; D009619:Nociceptors / Q000187:drug effects*; D012684:Sensory Thresholds; D014828:Vocalization, Animal / Q000187:drug effects
D009020:Morphine