Metabolic adjustments during adaptation to high ambient temperature by preoptic-lesioned rats

RESUMO

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