Morphine and naloxone effects on tonic immobility and the dorsal immobility response in the rat.
Adult male Wistar rats treated with morphine sulfate (0.5, 5.0, and 10.0 mg/kg, SC) showed a dose-dependent potentiation of tonic immobility (TI) and dorsal immobility response (DIR) durations. Naloxone (4.0 mg/kg, SC) did not affect the DIR durations but reversed the potentiated morphine effects on both TI and DIR. These results suggest that although opiate receptors may be involved, mu-opiate receptor function is not essential for modulating various complex immobility responses.
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D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D007103:Immobilization; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000378:metabolism; D017450:Receptors, Opioid, mu
D011957:Receptors, Opioid; D017450:Receptors, Opioid, mu; D009270:Naloxone; D009020:Morphine