Stress-induced analgesia in pigs.
In order to assess pain sensitivity in pigs, the tail-withdrawal reflex induced by immersing the tail into warm water was used. Reaction times were found to be a negative function of water temperature. They were not modified by 1 mg/kg morphine or naloxone. Higher doses of morphine (5 mg/kg) induced excitation which interfered with the assessment of the tail-withdrawal reflex. Low doses of xylazine (0.1-0.2 mg/kg) decreased reaction times while clearly sedative doses (10 mg/kg) had no effect. Various stressors (handling, exposure to a new environment, shock delivery, social isolation) enhanced reaction times and this increase was not blocked by naloxone.
D000698:Analgesia / Q000662:veterinary*; D000818:Animals; D005260:Female; D008297:Male; D009020:Morphine / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology; D010147:Pain Measurement / Q000379:methods / Q000662:veterinary*; D011930:Reaction Time; D012018:Reflex; D013312:Stress, Physiological / Q000662:veterinary*; D013552:Swine / Q000502:physiology*; D013623:Tail / Q000502:physiology; D013696:Temperature; D014991:Xylazine / Q000494:pharmacology
D014991:Xylazine; D009270:Naloxone; D009020:Morphine