Role of 5-hydroxytryptamine in morphine-, pethidine-, and methadone-induced hypothermia in rats at low ambient and room temperature.
1 The effect of morphine (10 or 20 mg/kg s.c.), pethidine (25 or 50 mg/kg s.c.) or methadone (4 or 8 mg/kg s.c.) on the body temperature of nontreated and p-chlorophenylalanine-pretreated rats was studied at room (21+/-0.2 degrees C) or low ambient (12+/-0.2 degrees C) temperature. 2 Neither pethidine nor smaller doses of morphine and methadone altered the mean rectal temperature of rats kept at room temperature but larger doses of morphine and methadone produced significant hypothermia. 3 All narcotic analgesics at doses used in the present investigation produced significant hypothermia in rats maintained in a low ambient temperature. The hypothermia was prevented by naloxone (1 mg/kg s.c.). 4 The administration of p-chlorophenylalanine (PCPA, 320 mg/kg i.p.) 48 h before the narcotic injection prevented the fall in body temperature both at room and low ambient temperature. 5 The administration of narcotic analgesics at doses, which when administered by themselves did not alter the body temperature of rats, produced significant hyperthermia in rats pretreated with PCPA. 6 When rats pretreated with PCPA were given 5-hydroxytryptophan (75 mg/kg s.c.) 30 min before narcotic administration, the usual response to narcotics was restored. 7 It appears that pethidine and methadone as well as morphine have both hyperthermic and hypothermic actions in rats and that 5-hydroxytryptamine may be involved in the narcotic-induced hypothermia not only at room temperature but also at low ambient temperature.
D006916:5-Hydroxytryptophan / Q000494:pharmacology; D000818:Animals; D001831:Body Temperature / Q000187:drug effects*; D003080:Cold Temperature; D003864:Depression, Chemical; D004347:Drug Interactions; D010134:Fenclonine / Q000494:pharmacology; D008297:Male; D008614:Meperidine / Q000494:pharmacology*; D008691:Methadone / Q000494:pharmacology*; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D051381:Rats; D012701:Serotonin / Q000502:physiology*; D013696:Temperature; D013997:Time Factors
D012701:Serotonin; D009270:Naloxone; D009020:Morphine; D008614:Meperidine; D006916:5-Hydroxytryptophan; D010134:Fenclonine; D008691:Methadone