Effect of neurohumoral modulators on the morphine-induced hyperthermia in non-tolerant rats.
Wistar rats from one supplier have been shown to exhibit the atypical body temperature responses to morphine. In contrast to commonly used rats, in which morphine induced dose-dependent changes in body temperature, the initial administration of morphine (5, 10, 20, and 40 mg/kg, s.c.) to rats of this particular strain produced a consistent and prominent hyperthermia. This hyperthermia is mediated via an action on the typical morphine receptors since it was completely prevented by a specific narcotic antagonist, naloxone. Effects of neurohumoral modulators on the hyperthermia have been investigated in these rats. Pretreatment of animals with p-chlorophenylalanine, alpha-methyltyrosine, phenoxybenzamine or propranolol did not alter the hyperthermia. In contrast, the s.c. administration of 1 mg/kg of either tertiary or quaternary anticholinergic drug such as scopolamine, atrophine, methscopolamine and methylatropine significantly inhibited the hyperthermia. These results suggest that morphine causes  hyperthermia in some strains of rats by a cholinergic mechanism and the involvement of an adrenergic or serotonergic mechanism in this case appears unlikely.
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001286:Atropine Derivatives; D001831:Body Temperature / Q000187:drug effects*; D004347:Drug Interactions; D004361:Drug Tolerance; D008297:Male; D009020:Morphine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000502:physiology*; D051381:Rats; D012601:Scopolamine / Q000494:pharmacology; D012602:Scopolamine Derivatives; D013268:Stimulation, Chemical; D013997:Time Factors
D001286:Atropine Derivatives; D018377:Neurotransmitter Agents; D012602:Scopolamine Derivatives; D009270:Naloxone; D009020:Morphine; D001285:Atropine; D012601:Scopolamine