Estrogen receptor immunoreactivity in ferret brain is regulated by estradiol in a region-specific manner

The effects of estrogen on estrogen receptor (ER) immunoreactivity in the male ferret brain were examined. Estrogen treatment reduced the mean number of ER-immunopositive (ER+) cells/unit area in periventricular preoptic area but increased the mean number of ER+ cells/unit area in the medial division of the ventromedial hypothalamic nucleus, while having no effect on the number of ER+ cells/unit area in the lateral VMH and arcuate nucleus. Thus, estrogen regulates brain ER immunoreactivity in male ferrets and the direction and magnitude of this regulation are brain region-specific.