Region-specific effects of ovarian hormones on estrogen receptor immunoreactivity

The cell groups in which nuclear estrogen receptor (ER) expressing neurons are found have unique, often coordinated, functions. Regulation of ER content may be one mechanism through which feedback responses can be adjusted to match the function of a specific brain region and physiological circumstance. In these immunocytochemical experiments, estrogen decreased staining intensity for ER in the ventrolateral hypothalamus and bed nucleus of the stria terminalis, but not in the periventricular preoptic area. ER staining intensity was further decreased by progesterone, following estrogen, but not in all brain regions. These results suggest that ER is regulated by estrogen in a region-specific manner. Furthermore, inhibition of responses to estrogen by progesterone may involve progesterone-induced down-regulation of ERs.