Oestrogen receptor β-immunoreactivity in gonadotropin releasing hormone-expressing neurones: Regulation by oestrogen

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