Repeated exposure to high environmental temperature changes brain regional GABA metabolism.

The effects of repeated exposure (2 h/day) to high environmental temperatures (40 degrees C) for 7, 15 and 30 consecutive days on gamma-aminobutyric acid (GABA) metabolism in different regions of adult rat brain were investigated. The GABAergic activity in hypothalamus was increased with the increase in duration (7-30 days) of HET exposure. In corpus striatum, on the other hand, 7 days repeated HET-induced increase in GABAergic activity was attenuated on prolongation of HET exposure from 15-30 consecutive days. Repeated HET exposure for 7 consecutive days also enhanced cerebrocortical GABAergic activity that became normalized following 15 or 30 days repeated HET exposure. These results suggest that long-term (repeated HET exposure enhanced hypothalamic GABAergic activity to adapt to the environment with the regulation of body temperature.