Immunocytochemical localization and quantitation of estrogen-binding cells in the male and female (virgin, pregnant, lactating) mouse brain.

Estrogen-binding cells in the brains of male, virgin, pregnant, and lactating female mice were localized and quantified using an immunocytochemical technique. Nuclear estrogen-receptors were detected in cells of the midbrain periventricular gray, the cortical and medial amygdaloid nucleus, the arcuate nucleus and ventromedial nucleus of the hypothalamus, the anterior hypothalamic area and the preoptic area in animals of all 4 experimental groups. In virgin females, immunostaining was also seen in the hippocampus, the entorhinal and piriform cortex and in the septal nuclei. In pregnant females the anterior amygdaloid area and the bed nucleus of the stria terminalis were labelled additionally. After the first 5 days of lactation, estrogen-binding cells could no longer be detected in the hippocampus, entorhinal and piriform cortex and anterior amygdaloid area. These apparent qualitative differences in the pattern of estrogen-receptor immunostaining among the experimental groups are further accentuated by significant quantitative differences in the absolute numbers and relative densities of labelled cells in a given nucleus. Pregnant females have the highest numbers of estrogen-binding cells in many nuclei, whereas lactating females have the highest densities of labelled cells. These differences suggest a dynamic regulation of the number and distribution of estrogen-target cells in the respective brain areas initiated by, or as a result of hormonal states of the animals. Functional implications are discussed.