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

Double-label immunohistochemistry was employed to establish whether immunor eactivity for the beta subtype of the oestrogen receptor (ER beta -IR) is p resent in gonadotropin releasing hormone (GnRH)-containing cells. In the im mortalized GnRH cell line, GT1-7, almost all nuclei were immunoreactive for ER beta. In the preoptic area of ovariectomized rats, more than one-half o f the GnRH neurones (52.0-63.5%) contained ER beta -IR within the nucleus; a smaller proportion of these neurones (5-10%) displayed a particularly int ense nuclear signal for ERP. The presence of ER beta -IR in the nuclei of G T1-7 cells and GnRH neurones is consistent with recent reports of ER beta m RNA in these cells. Oestrogen treatment reduced the percentage of GnRH neur ones with detectable ER beta -IR. The range of signal intensity for ER beta and the incidence of the ER beta signal in GnRH neurones were comparable f ollowing double-label immunohistochemistry involving either bright field or fluorescent techniques. These findings raise the possibility that ER beta receptors mediate direct effects of oestrogen on GnRH neurones.