Thermal homeostasis in rats after intrahypothalamic injections of 6-hyroxydopamine.
Specific destruction of at least 90% of the noradrenergic neurons in the preoptic/anterior hypothalamic region (PO/AH) by local injection of 9-hyroxydopamine (6-HDA) did not disrupt thermoregulation by rats either in the heat or the cold. Examination of the multiple effector mechanisms suggested that thermal balance was maintained in a normal fashion, and that compensatory adjustments did not conceal individual dysfunctions. In contrast with the ineffectual 6-HDA lesions of the PO/AH were the outstanding impairments seen in rats following electrolytic lesions of this area. All the latter animals became severely hyperthermic during the 1st h of exposure to an ambient temperature of 40 degrees C, and half of them were additionally unable to maintain body temperatures when exposed to an ambient temperature of 6 degrees C. The electrolytic lesions reduced norepinephrine levels in the PO/AH, but the 50-70% depletions were substantially smaller than those found in 6-HDA-treated rats. These results raise new doubts about whether central noradrenergic fibers have an important role in the regulation of body temperature by rats.
D000818:Animals; D001831:Body Temperature; D001833:Body Temperature Regulation / Q000187:drug effects*; D004556:Electric Injuries; D004566:Electrodes; D004594:Electrophysiology; D006892:Hydroxydopamines / Q000008:administration & dosage / Q000494:pharmacology*; D007031:Hypothalamus / Q000502:physiology*; D007032:Hypothalamus, Anterior / Q000502:physiology*; D007276:Injections, Intraventricular; D008297:Male; D010101:Oxygen Consumption; D011301:Preoptic Area / Q000502:physiology*; D051381:Rats
D006892:Hydroxydopamines