Metabolic adjustment induced by exposure to elevated ambient temperature is impaired in rats bearing lesions in the preoptic area.

Metabolic adjustment was studied in rats with bilateral electrolytic lesions in the preoptic area which were exposed to heat (34 degrees C) and to normal temperature (25 degrees C) for 60 days. The metabolic rate measured at neutral temperature (29 degrees C) in preoptic-lesioned rats living at 25 degrees or 34 degrees C was reduced to 80% the rate of sham-operated controls. The increase in metabolic rate induced by heat (30 min at 34 degrees or 37 degrees C) in preoptic-lesioned rats, living at 25 degrees C, was markedly reduced to 10% the rate of sham-operated controls living at 25 degrees C. In preoptic-lesioned rats, the increased metabolic rate induced by heat exposure (34 degrees or 37 degrees C) was impaired, regardless of the living ambient temperature (25 degrees or 34 degrees C) of the animal. These data demonstrate the participation of the preoptic area in heat-induced increased oxygen consumption and provide additional evidence for its role in the integration of thermal inputs with energy-linked metabolic processes.