Effects of perinatal steroid hormonal changes on the cytoarchitecture of brain

为了阐明两性二态性的形成机制，我们检测了不同发育阶段雄性和雌性大鼠内侧视前核凋亡细胞的数量。出生后第1天和第4天，视前脑室周围核出现大量凋亡细胞，且男性细胞数量明显多于女性。视神经内侧前核凋亡细胞数量在出生后第4天和第7天明显增加，且雌性明显多于雄性。我们发现凋亡细胞的分布与性别、区域位置和出生时间有关，表明细胞凋亡有助于内侧视前区性别二态性的形成。内侧视前区含有最多数量的雌激素受体。因此，我们扩大了实验范围，研究了雌激素受体在培养细胞中的亚细胞定位，其中与GFP相关的雌激素受体过表达。无论有无配体，雌激素受体的亚细胞定位都在细胞核内，而不是在细胞质内。结果表明，脑内性别二态性至少部分是由于特定区域的神经元凋亡，而这些细胞凋亡与类固醇激素受体的基因表达密切相关。

To elucidate the mechanism of the formation of sexual dimorphism, we examined the number of apoptotic cells in the medial preoptic nucleus in male and female rats of various developing stages. Many apoptotic cells in the postnatal day 1 and 4 were found in the preoptic periventricular nucleus and its number was significantly larger in male than in female. The number of apoptotic cells in the medial preoptic nucleus was increased in the postnatal day 4 and 7 and significantly larger in female than in male. It was found that the distribution of apoptotic cells depends on the sexuality, the location of the area and postnatal period, indicating that the apoptosis contributes the formation of sexual dimorphism in the medial preoptic area. The medial preoptic area contains highest number of estrogen receptors. Therefore we expanded our experiments to investigate the subcellular localization of estrogen receptor in cultured cells, in which estrogen receptor linked to GFP was over expressed. With or without ligand, the subcellular localization of estrogen receptor was localized in the nucleus, not in the cytoplasm.It was concluded that the sexual dimorphism in the brain was due, at least in part, to the apotosis of the neurons in the specific areas and these apoptosis was strongly linked to the gene expression of steroid hormone receptor.