Adaptive rewiring of the mature brain after injury

描述(由申请人提供)：中风或创伤性脑损伤的恢复受到成熟神经元无法显著重组其连接的部分限制。这种重组可能既需要积极的刺激来激活神经元的内在生长状态，也需要方法来克服通常抑制生长的抑制信号。肌苷是一种嘌呤核苷，它激活了一条细胞信号通路，调节对轴突生长至关重要的基因的表达。在成年大鼠中，肌苷在横断特定纤维束或单侧中风后刺激主要皮质通路的重组。这种重组允许来自完整半球的投射部分地重新支配失去正常输入的脑干和脊髓区域，并导致改善行为结果。目的1将调查有助于克服对轴突生长的抑制影响的药物是否可以增强肌苷对神经重组和行为结果的影响。目的2将探讨单侧脑损伤后强化训练本身是否促进轴突重组，以及这种训练是否会增强肌苷治疗的效果。最后，脑损伤后有一个有限的时间窗口，在这一时间窗口内必须开始肌苷治疗，以实现长期的益处。AIM 3将尝试识别其表达使神经元在这一“机会之窗”对肌苷作出反应的基因，以及在此期间肌苷治疗的结果表达的基因。这将使用激光捕获显微切割来分离皮质锥体细胞和微阵列，以识别其表达被选择性改变的基因。Aim 3的第二部分将使用基因治疗方法来研究改变皮质锥体细胞中与轴突生长相关的基因表达的效果。这些研究将增加我们对成熟大脑可塑性的理解，并有可能使我们能够改善损伤后的功能结果。

DESCRIPTION (provided by applicant): Recovery from stroke or traumatic brain injury is limited in part by the inability of mature neurons to reorganize their connections significantly. Such reorganization may require both positive stimuli to activate neurons' intrinsic growth state and methods to overcome inhibitory signals that normally suppress growth. Inosine, a purine nucleoside, activates a cellular signaling pathway that regulates the expression of genes important for axon outgrowth. In mature rats, inosine stimulates the reorganization of major cortical pathways after transecting a specific fiber tract or after a unilateral stroke. This reorganization allows projections from the intact hemisphere to partially reinnervate brainstem and spinal cord areas that have lost their normal inputs, and results in improved behavioral outcome. Aim 1 will investigate whether agents that help overcome inhibitory influences on axon growth can enhance the effects of inosine on neural reorganization and behavioral outcome. Aim 2 will investigate whether intensive training after unilateral brain damage itself promotes axonal reorganization, and whether such training will augment the effects of inosine treatment. Finally, there is a limited time window after brain injury in which inosine treatment must begin in order to achieve long-lasting benefits. Aim 3 will attempt to identify genes whose expression enables neurons to respond to inosine during this "window of opportunity", as well as genes that are expressed as a result of inosine treatment during this period. This will be done using laser-capture microdissection to isolate cortical pyramidal cells and microarrays to identify genes whose expression is selectively altered. The second part of Aim 3 will use a gene therapy approach to investigate the effects of altering the expression of genes related to axon growth in cortical pyramidal cells. These studies will increase our understanding of plasticity in the mature brain and potentially enable us to improve functional outcome after injury.