ABSTRACT
Metabolic adjustment was studied in male Wistar rats weighing 180-200 g with bilateral electrolytic lesions in the preoptic area which were acclimatized to a hot envirnment (34-C, 30 rats) and to normal temperature (25-C, 20 rats) for 60 days. Oxygen consuption at 34-C and body weight were measured periodically. Preoptic-lesioned rats (POrats) showed a reduction in metabolic rate (from 46.2 ñ 2 to 33 ñ 2 Cal/m2 per h, P < 0.05) regardless of the temperatures to which they were adapted. Although the reduced metabolic rate of PO rats living at 25-C or 34-C could be an indicator of adaptation to heat, only the PO rats living at 25-C showed a weight gain (101 ñ 13 g) similar to that observed for the sham-operated control (75 ñ 11 g). In fact, the PO rats living at 34-C failed to increase their body weight during 60 days of exposure to heat. These data indicate that the preoptic area is essential to integrate the thermal imput with the energy-linked metabolic process involved in adaptation to hot environments
Subject(s)
Rats , Male , Animals , Adaptation, Physiological , Hot Temperature , Oxygen Consumption/physiology , Preoptic Area/physiology , Body Weight , Energy Metabolism , Rats, Inbred StrainsABSTRACT
Metabolic adjustment was studied in rats with bilateral electrolytic lesions in the preoptic area which were exposed to heat (34-C) anda to normal temperature (25-C) for 60 days. The metabolic rate measured at neutral temperature (29-C) in preoptic-lesioned rats living at 25- or 34-C was reduced to 80% the rate of sham-operated controls. The increase in metabolic rate induced by heat (30 min at 34- or 37-C) in preoptic-lesioned rats, living at 25-C, was markedly reduced to 10% the rate of sham-operated controls living at 25-C. In preoptic-lesioned rats, the increased metabolic rate induced by heat exposure (34- or 37-C) was impaired, regardless of the living ambient temperature (25- or 34-C) of the animal. These data demonstrate the participation of the preoptic area in heat-induced invreased oxygen consumption and provide additional evidence for its role in the integration of thermal imputs with energy-linked metabolic processes