Morphine potentiation of tonic immobility: effects of naloxone, PCPA, and 5,6-DHT.
The duration of tonic immobility in chickens, a catatonic-like state produced by brief restraint, was greatly potentiated by a single 1.0 mg/kg injection of morphine. Naloxone by itself, however, had no effect on tonic immobility, and only an exceptionally large dose of naloxone blocked the morphine potentiation. Pretreatment with PCPA and 5,6-dihydroxytryptamine completely eliminated the morphine enhancement. The effect of morphine on tonic immobility may be mediated by a central serotonergic-raphe system.
D015115:5,6-Dihydroxytryptamine / Q000494:pharmacology*; D000818:Animals; D002375:Catalepsy / Q000139:chemically induced*; D002645:Chickens; D004347:Drug Interactions; D010134:Fenclonine / Q000494:pharmacology*; D006801:Humans; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology*
D009270:Naloxone; D009020:Morphine; D010134:Fenclonine; D015115:5,6-Dihydroxytryptamine