Effects of pain, morphine and naloxone on the duration of animal hypnosis.
Previous research has shown that animal hypnosis (tonic immobility) in the rabbit may be elicited in a condition of prolonged nociceptive stimulation. These experiments show that long-lasting irritative pain, produced within 15 min of formalin injection, potentiates the duration of hypnosis. Morphine, in the absence of painful stimuli, also potentiates hypnosis duration and this effect is antagonized by naloxone. Naloxone reduces hypnosis duration, but only at high doses (15 mg/kg). In a condition of irritative pain, the potentiation of hypnosis duration is abolished by naloxone (5 mg/kg). Hypnosis response is abolished in 6 out of 7 morphine-tolerant rabbits, but prolonged pain restores the response. The hypothesis that an opioid mechanism may be activated during animal hypnosis is discussed.
D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects; D004569:Electroencephalography; D005071:Evoked Potentials / Q000187:drug effects; D006185:Habituation, Psychophysiologic / Q000187:drug effects / Q000502:physiology; D006990:Hypnosis; D007103:Immobilization; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology*; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology*; D011817:Rabbits; D011957:Receptors, Opioid / Q000187:drug effects
D011957:Receptors, Opioid; D009270:Naloxone; D009020:Morphine