title: Effects of dose on effector mechanisms in morphine-induced hyperthermia and poikilothermia.
abstract: The effect of a variety of morphine doses on thermoregulatory effector systems was examined in ambient temperatures of 27.0 degrees C and 4.0 degrees C. Rats were given saline or morphine sulfate (5, 15, or 25 mg/kg); their core temperature, oxygen consumption, and activity were monitored for 4 or 6 h post-injection. The results suggest two distinct actions of morphine, possibly mediated by two opiate receptors. Low doses of morphine produce hyperthermia that is the result of a direct activation of activity and whole body heat production. High doses produce effects dependent on ambient temperature: hypermetabolism and hyperthermia in the 27.0 degrees C environment; hypometabolism, vasodilation, and hypothermia in the 4.0 degrees C environment. The findings suggest limitations in current set-point theories of morphine's thermic actions.
authors.affiliation: Department of Psychology University of Wisconsin, Madison 53706.
authors.forename: D E
authors.initials: DE
authors.lastname: Jorenby
authors.forename: R E
authors.initials: RE
authors.lastname: Keesey
authors.forename: T B
authors.initials: TB
authors.lastname: Baker
mesh_terms: D000818:Animals; D001833:Body Temperature Regulation / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004734:Energy Metabolism / Q000187:drug effects; D005508:Food Deprivation; D009020:Morphine / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects; D010101:Oxygen Consumption / Q000187:drug effects; D051381:Rats; D012119:Respiration / Q000187:drug effects; D013997:Time Factors
chemical_list: D009020:Morphine