Effects of morphine and related drugs on core temperature of two strains of rat.
The changes in core temperature induced by low (5 mg/kg) and high (40 mg/kg) doses of morphine were compared in Wistar and Sprague-Dawley rats. In Sprague-Dawley rats the low dose caused a hyperthermia and the high dose a hypothermia but in Wistar rats both doses caused a hyperthermia. In either case the change in core temperature was antagonized by naloxone (2 mg/kg). Tolerance to the effects of the high dose of morphine developed in both strains of rat. Dextromoramide (3.75 and 15 mg/kg) also had an effect on core temperature, but in this case the responses of the strains were opposite to those seen with morphine. Laevomoramide was relatively ineffective. Naloxone (2 mg/kg) had no effect on the ability of rats of either strain to withstand heat or cold stress, providing no evidence that endogenous morphine-like substances have a physiological role in thermoregulation.
D000818:Animals; D001831:Body Temperature / Q000187:drug effects*; D003080:Cold Temperature; D003916:Dextromoramide / Q000494:pharmacology; D006358:Hot Temperature; D006801:Humans; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009021:Morphine Dependence / Q000503:physiopathology; D009025:Morpholines / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013045:Species Specificity; D013237:Stereoisomerism; D013997:Time Factors
D009025:Morpholines; D009294:Narcotics; D009020:Morphine; C018992:levomoramide; D003916:Dextromoramide