Transient receptor potential M2 channel in the hypothalamic preoptic area and its impact on thermoregulation during menopause.

BACKGROUND: Decreased estrogen levels can cause abnormal thermosensitivity of the preoptic area (POA) in the hypothalamus during menopause, which may cause hot flashes. Thermosensitive transient receptors (ThermoTRPs) affect the thermosensitivity of neurons. It is worth exploring whether ThermoTRPs change under low estrogen state and participate in the abnormal thermoregulation of POA. METHODS: Adult female Sprague-Dawley rats were randomly divided into sham operation (SHAM), ovariectomy (OVX) and estrogen treatment after ovariectomy (OVX+E) groups. Under 10 â„ƒ, 18 â„ƒ, 25 â„ƒ, 37 â„ƒ and 45 â„ƒ incubations, their skin temperature was monitored and the expression of TRPA1, TRPM8, TRPM2, and TRPV1 in POA were investigated. RESULTS: The skin temperature of ovariectomized rats changed faster and more dramatically under different incubation temperatures. The results at mRNA level show that only the expression of TRPM2 decreased in POA of OVX group compared with the other two groups at 25 â„ƒ, TRPA1 expression in POA of the three groups increased at 10 â„ƒ, TRPM8 increased at 10 â„ƒ and 18 â„ƒ, TRPV1 increased at 10 â„ƒ and 45 â„ƒ, while the expression of TRPM2 decreased at 10 â„ƒ and 18 â„ƒ and increased at 37 â„ƒ and 45 â„ƒ. In all these cases, the magnitudes of the changes were less in the OVX group relative to the other two groups. The further immunohistochemical and Western blot results of TRPM2 and the activated TRPM2 positive cells labeled by c-Fos were consistent with the results of mRNA level. CONCLUSIONS: The expression and thermosensitivity of TRPM2 in POA changed greatly under different incubation temperatures, but the changes in ovariectomized rats were less. This may be the key factor triggering thermoregulation dysfunction under low estrogen and may cause hot flashes.