Physiological Role of Estrogen Receptor β Positive Cells in Liteinizing hormone surge.

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In this project, we investigated the physiological role of estrogen receptor β (ERβ) in sexual differentiation of developing brain and sex specific regulation of reproductive neuroendocrinology in the adult rats. By using non-isotoic in situ hybridizaiton and immunohistochemistry, we found a strikingly sex difference expression of the ERβ in the anteroventral periventricular nucleus (AVPV) of the rat preoptic area. In females more than in males, a significantly of larger number ERβ mRNA positive cells were visualized in the medial portion of the AVPV within 50 μm form the ependymal surface of the third ventricle. Orchidectomy of male neonates or estrogen treatment of female pups reversed the brain phenotype when examined on day 14. In the AVPV of adult females, ERα immunoreactivity colocalized in 83% of ERβ mRNA-positive cells.Infusion of ERβ antisense oligonucleotide into the third ventricle in the vicinity of the AVPV resulted in significantly longer days of successive estrus and a 50% reduction in the number of ERβ-immunoreactive cells in the AVPV. These findings provide support for the hypothesis that activation of ERβ in the AVPV is an important regulatory event in the female-typical induction of luteinizing hormone surge by estrogen. We further examine the interaction between ERβ and ERα in the regulation of luteinizing hormone surge by estrogen by using oligonucleotide infusion into the AVPV now.