Molecular analysis of sex difference in the hippocampus, a center for learning and memory

目前这项研究的目标是阐明学习和记忆中心海马体中的性别差异。(1)海马性激素浓度存在明显的性别差异。海马区雌二醇(E_2)是最强的雌激素，男性高于女性。在整个发情周期中，海马区的雌二醇组都有波动。海马区睾酮(T)浓度男性高于女性，无波动。(2)令人惊讶的是，在整个发情周期中，雌性大鼠海马区类固醇合成酶及其受体的表达水平没有性别差异，也没有波动。(3)雌性大鼠海马树突棘密度在整个发情周期中波动。脊柱总密度在Pro和D1时最大，EST和D2时最低，而男性在Pro或D1时高于女性。脊椎密度的波动规律与海马性类固醇浓度的波动规律相一致。总而言之，在海马体合成的性激素中存在明显的性别差异，性激素在调节树突棘密度方面起着至关重要的作用。

The goal of the current study is elucidation of sex difference in the hippocampus, a center for learning and memory. (1) Concentration of sex hormones in the hippocampus exhibited clear sex difference. Hippocampal concentration of estradiol (E2), the most potent estrogen, was higher in male than that in female. Hippocampal E2 fluctuated across the estrous cycle. The concentration of hippocampal testosterone (T) was higher in male than female, which did not fluctuate. (2) Surprisingly, the expression level of the steroidogenic enzymes and receptors in the hippocampus exhibited neither sex difference nor fluctuation across the estrous cycle.(3) The density of dendritic spines in female hippocampus fluctuated across the estrous cycle. The total spine density showed the maximum at Pro and D1, and the minimum at Est and D2 whereas the total spine density in male was as high as that in female at Pro or D1. The fluctuating pattern of spine density corresponded to that of hippocampal concentration of sex steroids. Taken together, there is clear sex difference in the hippocampus-synthesized sex hormones which play a crucial role in regulating the density of dendritic spines