STEROIDS STIMULATE AXON REGENERATION IN THE ADULT BRAIN

成人神经系统的适当融合取决于精确的模式。 在发育过程中建立的神经元连接。在更高的 脊椎动物，中枢神经系统的神经元可塑性是有限的 到改变突触的形态和功效。相比之下， 鸣禽在成鸟身上表现出极大程度的神经元可塑性 中枢神经系统。几个大脑核团，与学习和产生 歌，经历了戏剧性的、季节性的变化，并与波动相关 血浆睾酮水平。高血浆睾酮水平可导致 纹状体腹侧部神经元数量的增加 Caudale(HVC)下降50%，每天增加新的 神经元数量达到0.5%。大多数新的HVC神经元投射轴突 通过密集的髓鞘脑区到达它们的靶神经元 粗壮的弓状体核(RA)。有强有力的证据表明 睾酮调节有丝分裂后事件，而不是细胞 扩散。这项提案将调查睾丸素在 在髓鞘存在下刺激轴突生长，导致 功能性神经元连接的形成。这项体外研究将 利用分离培养的HVC神经元接种到冰冻切片上 成年鸣禽的大脑。此外，HVC的轴突引导机制-- 神经元将在活的、长期的脑切片准备中得到解决。 将用DiI和腺病毒标记待研究的HVC-神经元- 绿色荧光蛋白和/或β-受体的介导性表达 半乳糖苷酶。这些报告基因的表达是由不同的 启动子在HV/c-神经元或其他细胞中实现独占表达 与学习和产生歌曲有关的神经元群。钥匙 建议研究中使用的方法包括实时视频显微镜。 下相和DIC光学、荧光显微镜、免疫细胞化学 组织化学染色。理解睾丸激素的原理-- 在髓鞘存在的情况下依赖轴突的生长可以改善我们的 关于成年哺乳动物中枢神经系统功能再生的知识。

The proper fusion of the adult nervous system depends on a precise pattern of neuronal connections established during development. In higher vertebrates, neuronal plasticity in the central nervous system is limited to modifications of the morphology and efficacy of synapses. In contrast, songbirds exhibit a tremendous degree of neuronal plasticity in the adult CNS. Several brain nuclei, associated with learning and production of song, undergo dramatic, seasonal changes and correlated with fluctuating plasma testosterone levels. High plasma testosterone levels induce increases in neuronal cell number in the hyperstriatum ventrale pars caudale (HVc) by as much as 50% with a daily rate of addition of new neurons reaching 0.5%. The majority of new HVc-neurons project axons through densely myelinated brain regions to their target neurons in the robust nucleus of the archistriatum (RA). There is strong evidence that testosterone regulates post-mitotic events rather than cellular proliferation. This proposal will investigate the role of testosterone in stimulating axon outgrowth in the presence of myelin resulting in th formation of functional neuronal connections. This in vitro study will utilize HVc-neurons in dissociated cultures and seeded onto cryosections of adult songbirds brain. Furthermore, axon guidance mechanisms of HVc- neurons will be addressed in living, long-term brain slice preparations. HVc-neurons to be studied will be labeled with DiI and by adenoviral- mediated expression of green fluorescent protein and/or beta- galactosidase. Expression of these reporter genes is driven by various promoters to achieve exclusive expression in HV/c-neurons or other neuronal population associated with learning and production of song. Key methods employed in the proposed research include live video microscopy under phase and DIC optics, fluorescence microscopy, immunocytochemical and histochemical staining. Understanding the principal of testosterone- dependent axon outgrowth in the presence of myelin could improve our knowledge to address functional regeneration in the adult mammalian CNS.