抄録
We examined the effect of heat exposure on proliferation and differentiation of neuronal progenitor cells in rat hypothalamus. Male Wistar rats, 5 weeks age, were initially maintained at an ambient temperature (Ta) of 24 °C under a 12:12-hour light-dark cycle. Then, heat-exposed rats (HE) were subjected to a constant Ta of 32 °C, while controls were kept at 24 °C. Bromodeoxyuridine (BrdU, 50 mg/kg/day, i.p.) was injected into the rats daily for 5 consecutive days starting on the 1st, 11th or 21st day after commencing heat exposure. Four weeks after termination of BrdU injection, the rats were anesthetized and the brains were sampled. Immunohistochemical analysis showed that in anterior hypothalamus, the numbers of BrdU-immunopositive cells of HE were significantly and consistently greater than those of controls. In HE, 3-4% of BrdU-immunopositive cells were stained by NeuN, a neuron marker, or APC, an oligodendrocyte marker, but rarely stained by GFAP, an astrocyte marker. The majority of BrdU-immunopositive cells were double-stained by doublecortin (70%), a marker of neuronal progenitors which differentiate into neurons. These results suggest that heat exposure facilitates proliferation of neuronal progenitor cells in anterior hypothalamus. Heat exposure also promotes differentiation of newly generated cells which may have a role in functional changes in the thermoregulatory center in heat-acclimated rats. [J Physiol Sci. 2008;58 Suppl:S100]
