抄録
INTRODUCTION We reported that, in ovariectomized rats, thermoregulation in the cold was attenuated. Systemic administration of 17-βestradiol (E2) restored the attenuated response. E2 increased cFOS immunoreactive cells in the medial preoptic area ( MPO ) and dorsomedial hypothalamus ( DMH ) in the cold. In the present study, we hypothesized that E2 would upregulate thermosensitivity to the cold at the level of the hypothalamus. To test this hypothesis, we assessed the effect of the local administration of E2 to the two hypothalamic areas on body temperature ( Tb ) in the cold. METHODS Adult female rats were ovariectomized, and a stainless steel canula was placed in the MPO, DMH, or horizontal limb diagonal band. At least 7 days after the surgery, E2 or cholesterol was administrated to this brain area through the canula. Forty-eight hours after the administration, a rat was exposed to 10°C or 25°C environment for 2h, and Tb was continuously measured. RESULTS During the 10°C exposure, Tb increased only in the group, which is administrated E2 in the MPO. Either cholesterol nor E2 in the other brain area had no effect on Tb. CONCLUSION The MPO has abundant estrogen receptors and so-called thermosensitive neurons, estrogen may modulate thermosensitivity to the cold in the MPO. We also clarified the mechanism, based on cFOS immunoreactivity in the hypothalamic areas and UCP1 mRNA expression in the interscapular brown adipose tissue. [J Physiol Sci. 2008;58 Suppl:S100]
