HSP70 expression in the CNS in response to exercise and heat stress in rats

We have previously documented the regional distribution of 70-kDa heat shock protein (HSP70) in brains of rats made hyperthermic by brief exposure to high-powered microwaves (HPM; 2.06 GHz). We now compare HSP70 expression induced by HPM exposure to that induced by exertional and/or environmental heat stress. Rats were chronically implanted with a temperature probe guide in the hypothalamic region of the brain (T-br) After recovery, the following treatment groups were examined: HPM; sham exposed; treadmill exercise at room temperature (24 degrees C; Ex-1); treadmill exercise in a warm environment (34 degrees C; Ex-2); and sedentary groups (Sed-1 and Sed-2), in which ambient temperature was adjusted so that the T-br mimicked the T-br in the corresponding exercise groups. Significant HSP70 expression occurred only in the hyperthermic (Ex-2, Sed-2, and HPM) groups. The pattern of HSP70 expression was similar among Ex-2 and Sed-2 rats but differed from that in HPM rats. We conclude that 1) the pattern of HSP70 expression differs between HPM and non-microwave heating, and 2) exercise alone was not sufficient to induce central HSP70 expression.