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ROLE OF 5‐HYDROXYTRYPTAMINE IN MORPHINE‐, PETHIDINE‐, AND METHADONE‐INDUCED HYPOTHERMIA IN RATS AT LOW AMBIENT AND ROOM TEMPERATURE
Author(s) -
OKA T.
Publication year - 1977
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1977.tb07503.x
Subject(s) - pethidine , hypothermia , morphine , methadone , narcotic , anesthesia , chemistry , (+) naloxone , hyperthermia , opioid , medicine , pharmacology , analgesic , receptor
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°C) or low ambient (12 ± 0.2°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.

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