NEUROTROPHIN CONTROL OF THALAMOCORTICAL DEVELOPMENT

在初级体感（SmI）皮层中颅面外周有序表征（啮齿动物的须状）的正常发育需要外周输入。虽然很明显，皮层模式形成之间的竞争。因此，竞争性相互作用可能不是基于电事件，而是基于对中枢神经系统产生的生长促进物质的获取。在这里，我们建议评估通常存在于这些区域的神经营养素在丘脑皮质事件（TCAs）发展中的作用。基于对发育中的视觉系统（Cabelli et al., 1995）和三叉神经初级事件（Project 1）的观察，我们假设tca在发育的关键时期竞争获得特定神经营养物质的有限供应，神经营养物质在发育的关键时期的时空分布，以及神经营养物质的时空分布是丘脑皮质结构和功能的重要决定因素。具体来说，NT-3会产生轴突树突，BDNF会产生轴突伸长。NT-3和BDNF的增强递送将通过三种验证方法完成，包括浸渍Elvax植入物（实验1a）、转基因过表达（实验1b）和移植含有转基因的神经诱导胚胎干细胞，这些转基因设计用于有条件地过表达每种神经营养因子（实验2）。在实验1和2中，因变量评估TCA形态学指标，包括单纤维和总产量分析，使用神经生物素和DiI死后顺行标记。实验2将评估含有转基因的神经干细胞的整合和分化，以过度表达神经营养因子。实验3将皮质桶状模式与实验1和2中观察到的个体TCA形态和地形变化进行比较。Core A将对胚胎干细胞上的TCA和第四层神经元进行标记，并对TCA突触进行立体超微结构分析。Core B将产生四环素调控的NT-3/BDNF转基因小鼠。Core C将量化TCA形态和皮质C共聚焦显微镜，并在Core C中使用体视学方法进行量化。这些研究将为移植的胚胎干细胞提供见解，这些研究将与使用移植恢复功能丧失的治疗策略相关，无论个体非区域承诺的神经前体是否能够整合到SmI皮层的正常体位组织中，以及是否存在临界敏感期。

Normal development of ordered representations of the craniofacial periphery (whisker pattern in rodents) in the primary somatosensory (SmI) cortex requires peripheral input. Although it is clear that competition between cortical pattern formation. Thus, competitive interactions may not be based upon electrical events, but rather, access to a growth-promoting substance(s) that (are) produce in the central nervous system. Here, we propose to evaluate the actions of neurotrophins, normally present in these areas, upon the development of thalamocortical afferents (TCAs). Based upon observations in the developing visual system (Cabelli et al., 1995) and trigeminal primary afferents (Project 1), we hypothesize that TCAs compete for access to a limited supply of particular neurotrophins during critical periods of development, and that the spatial and temporal distribution of neurotrophins during critical periods of development, and that the spatial and temporal distribution of neurotrophins is an important determinant of thalamocortical structure and function. Specifically, NT-3 will produce axon arborization and BDNF will produce axon elongation. Augmented delivery of NT-3 and BDNF will be accomplished using three corroborative approaches that include impregnated Elvax implants (Experiment 1a), transgenic over- expression (Experiment 1b), and transplantation of neural induced ES cells containing transgenes designed to conditionally over-express each neurotrophin (Experiment 2). In Experiments 1 & 2, the dependent variable assess TCA morphologic indices including single fiber and total production analysis using neurobiotin and DiI post-mortem anterograde labeling. Experiment 2 will assess integration and differentiation of neural ES cells containing transgenes to over-express the neurotrophins. Experiment 3 will compare cortical barrel patterns to individual TCA morphologic and topographic changes observed in Experiments 1 & 2. Core A will perform labeling of TCAs and layer IV neurons and stereologic ultrastructural analysis of TCA synapses upon ES cells. Core B will produce the tetracycline regulated NT-3/BDNF transgenic mice. Core C will quantify TCA morphology and cortical C confocal microscope and quantified using stereologic methods in Core C. These studies will provide insights with transplanted ES cells will be relevant to therapeutic strategies using transplantation to restore function lost whether individual non-regionally committed neural precursors are capable of being integrated into the normal somatotopic organization of the SmI cortex and if a critical-sensitive period exists.