Oestrogen Receptor β‐Immunoreactivity in Gonadotropin Releasing Hormone‐Expressing Neurones: Regulation by Oestrogen

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Abstract
Double-label immunohistochemistry was employed to establish whether immunoreactivity for the β subtype of the oestrogen receptor (ERβ-IR) is present in gonadotropin releasing hormone (GnRH)-containing cells. In the immortalized GnRH cell line, GT1-7, almost all nuclei were immunoreactive for ERβ. In the preoptic area of ovariectomized rats, more than one-half of the GnRH neurones (52.0–63.5%) contained ERβ-IR within the nucleus; a smaller proportion of these neurones (5–10%) displayed a particularly intense nuclear signal for ERβ. The presence of ERβ-IR in the nuclei of GT1-7 cells and GnRH neurones is consistent with recent reports of ERβ mRNA in these cells. Oestrogen treatment reduced the percentage of GnRH neurones with detectable ERβ-IR. The range of signal intensity for ERβ and the incidence of the ERβ signal in GnRH neurones were comparable following double-label immunohistochemistry involving either bright field or fluorescent techniques. These findings raise the possibility that ERβ receptors mediate direct effects of oestrogen on GnRH neurones.