Hyperthermia evoked by the intracerebral injection of morphine sulphate in the rat: the effect of restraint.
Morphine sulphate (M) was microinjected intracerebrally into 26 sites in the free-moving and 11 sites in the restrained rat. The injections were made into the preoptic-anterior hypothalamic (POAH) region as core temperature (Tc) was measured. A marked increase in Tc was evoked from the free-moving rat following doses of M of 1 (n = 10); 10 (n = 19); 20 (n = 7); or 50 microgram (n = 6). On the other hand, no increase in Tc significantly above the control level was observed in the restrained rat following the intracerebral administration of M in doses of 10 (n = 8), 20 (n = 9), 50 (n = 10), or 70 microgram (n = 4). The control injection of the artificial cerebrospinal fluid (5-ion), used as the drug vehicle, caused a mild hyperthermia about 1.0 degrees C above the baseline level in both the free-moving and restrained rat. We conclude that morphine evokes a hyperthermia by its action on POAH neurons, but the M-induced hyperthermia can be attenuated by restraining the rat.
D000818:Animals; D001831:Body Temperature / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005334:Fever / Q000139:chemically induced*; D007031:Hypothalamus / Q000187:drug effects*; D007032:Hypothalamus, Anterior / Q000187:drug effects*; D007267:Injections; D008297:Male; D009020:Morphine / Q000008:administration & dosage*; D011301:Preoptic Area / Q000187:drug effects; D051381:Rats; D012149:Restraint, Physical
D009020:Morphine