INTRACELLULAR ION ENVIRONMENT DURING THE ONTOGENY AS A DETERMINANT OF SEXUAL PHENOTYPE OF RAT BRAIN

在大鼠中，雌激素决定了大脑的性别表型，在新生儿的关键时期起作用。这样建立的性表型在形态和电生理学上都持续到成年。成年男性视前区的性二形核(SDN-POA)体积大于女性。女性的前腹侧脑室周围核(AVPV)充满雌激素受体(ER)ss阳性神经元，而男性的这些细胞散布在更外侧的区域。雌激素调节女性下丘脑腹内侧和视前区完全相反方向的投射神经元的轴突兴奋性，但对男性不起作用。男性的表型取决于新生儿时雌激素的存在；缺乏雌激素会导致女性的表型。这个研究项目集中在细胞内的信号级联，这些信号级联由雌激素通过雌激素受体(ER)α激活，最终导致神经发生、迁移或细胞死亡。1)利用5‘-RACE技术鉴定了ER-α基因的一个新的先导外显子和未翻译的内部外显子。2)在由ERα启动子0/B控制下表达α的转基因大鼠的一个性状中，α阳性神经元是荧光的，而邻近区域不表达。时间推移电影显示，SDN-POA是神经元迁移的结果；3)在转基因大鼠的另一个特征，其中促性腺激素释放激素(GnRH)神经元被绿色荧光蛋白标记，激活GABAA_A受体使成年GnRH神经元去极化，因为它们的高氯离子含量；4)DNA微阵列，聚合酶链式反应和蛋白质印迹分析显示，在SDN-POA和AVPV中，凋亡和迁移相关基因的调节是位点特异的，相反。

In the rat, estrogen determines sexual phenotype of the brain, acting at a critical period as neonates. The sexual phenotype thus established persists into adulthood, both in morphology and electrophysiology. In the adults, the volume of the sexually dimorphic nucleus of the preoptic area (SDN-POA) is larger in males than in females. The anteroventral periventricular nucleus (AVPV) is packed with estrogen receptor (ER) ss-positive neurons in females but these cells scatter in the more lateral areas in males. Estrogen regulates axonal excitability of projection neurons in the ventromedial hypothalamus and those in the preoptic area in diametrically opposite directions in females but not in males. Male phenotype depends on the presence of estrogen as neonates ; the lack leads to the female phenotype. This research project focused intracellular signal cascades, which are kindled by estrogen through estrogen receptor (ER) α and culminate in neurogenesis, migration or cell death. 1) By using 5'-RACE we identified a new leader exon and untranslated internal exons in ERα gene. These exons were used for site-specific transcription of ERα ; 2) In a trait of transgenic rat, which express EGFP under the control of ERα promoter 0/B, ERα-positive neurons in the SDN-POA, but not those in the adjacent areas, were fluorescent. Time lapse movies showed the establishment of the SDN-POA as a result of neuronal migration ; 3) In another trait of transgenic rat, in which gonadotropin-releasing hormone (GnRH) neurons were tagged by EGFP, activation of GABAA_A receptors depolarized adult GnRH neurons due to their high chloride ion content ; 4) DNA microarray, PCR and Western-blot analysis demonstrated site-specific, opposite regulations of apoptosis- and migration-related genes in the SDN-POA and AVPV.