Androgen Receptor Expression in Developing Rat Forebrain

这项研究的总体目标是阐明睾酮对发育中的哺乳动物神经系统影响的潜在机制。睾丸激素塑造发育中的神经系统，确保大脑的性别表型与性腺的表型相匹配。在啮齿动物中，围产期的睾酮暴露不仅使中枢神经系统的形态、连通性和化学成分永久男性化，而且还使行为和神经内分泌功能变得男性化。睾酮和雌激素受体的雌激素代谢物在前脑男性化过程中的重要作用是毋庸置疑的。然而，令人信服的积累数据使我们假设，雄激素受体是睾酮对神经系统的组织效应的一个组成部分，雄激素受体表达和调控的时空变化有助于雄激素在调节大脑发育中的特定行动。我们将使用分子和解剖学的综合方法来研究大鼠脑中七个功能相关区域雄激素受体表达的发育和激素调节。这些研究将构成行为实验的基础，这些实验将测试发育过程中雄激素受体的激活是否会改变性别差异行为的发展。四个具体的假设将被检验：I.通过雄激素受体发挥作用的解剖学底物存在于前脑中；ii.产前睾酮在发育后期使雄激素受体的mRNA和蛋白水平男性化；iii.激素对雄激素受体表达的调节是发育阶段特有的；IV.雄激素暴露通过雄激素受体依赖的机制使行为男性化。大鼠将接受特定类固醇受体配体或拮抗剂的治疗，雄激素受体的mRNA和蛋白表达将通过原位杂交、免疫细胞化学和蛋白质印迹进行评估，或者将使用成人对激素的行为反应的标准指标进行行为分析。这些研究将确定雄激素受体mRNA和蛋白表达何时开始，雄激素受体蛋白表达细胞在发育过程中的表型，出生前或出生后雄激素是否调节随后的雄激素受体表达，以及何时出现雄激素受体调节模式，最后，雄激素受体表达和调节的变化是否影响对随后激素暴露的敏感性，并在成人性行为成熟中发挥作用。建议的研究将为剖析大脑性别分化过程中的复杂机制提供必要的数据，并有助于理解发育阶段对激素的特定反应。此外，这些研究将阐明神经和精神障碍的病因学，这些疾病在男性比女性中更普遍。

The overall goal of this research is to elucidate the mechanisms underlying the impact of testosterone on the developing mammalian nervous system. Testosterone sculpts the developing nervous system, insuring that the sexual phenotype of the brain matches that of the gonads. In rodents, testosterone exposure during the perinatal period permanently masculinizes not only the morphology, connectivity, and chemistry of the central nervous system but also behavioral and neuroendocrine functions. The prominent role of both estrogenic metabolites of testosterone and estrogen receptors in the process of forebrain masculinization is undisputed. Compelling accumulated data, however, have led us to hypothesize that androgen receptors are an integral component of the organizational effects of testosterone on the nervous system, and that spatial and temporal shifts in androgen receptor expression and regulation contribute to specific actions of androgens in modulation of brain development. An integrated molecular and anatomical approach will be used to examine the development and hormonal regulation of androgen receptor expression in seven functionally relevant regions of the rat brain. These studies will form the basis for behavioral experiments that will test whether androgen receptor activation during development modifies the development of sexually differentiated behaviors. Four specific hypotheses will be tested: I. The anatomical substrate for testosterone action via androgen receptors exists prenatally in the forebrain; II. Prenatal testosterone masculinizes androgen receptor mRNA and protein levels during later development; III. Hormonal regulation of androgen receptor expression is specific to the developmental stage; IV. Androgen exposure masculinizes behaviors via androgen receptor dependent mechanisms. Rats will be treated with specific steroid receptor ligands or antagonists, and androgen receptor mRNA and protein expression will be assessed using in situ hybridization, immunocytochemistry and western blots, or behaviors will be analyzed using standard measures of adult behavioral responses to hormones. These studies will determine when androgen receptor mRNA and protein expression begins, the cellular phenotype of androgen receptor protein expressing cells through development, whether pre or postnatal androgen modifies subsequent androgen receptor expression, and when adult patterns of androgen receptor regulation arise, and finally, whether alterations in androgen receptor expression and regulation affect sensitivity to subsequent hormone exposure and play a role in maturation of adult sexual behaviors. The studies proposed will provide data essential to dissecting the complex mechanisms underlying the process of sexual differentiation of the brain, and contribute to an understanding of developmental stage-specific responses to hormones. Further, these studies will shed light on the etiology of neurologic and mental disorders that are more prevalent in men vs. women.