REGULATION OF DORSAL ROOT AXON BRANCHING BY NEUROTROPHIN

这项工作的目的是评估神经元生长的影响 在哺乳动物脊髓轴突分支的因素。 背 根传入投射已被选为模型系统，因为四个 已知生长因子的“神经营养蛋白”家族的成员 促进体外培养的背根神经节（DRG）细胞突起生长。 此外，DRG细胞的生理学上指定的类别中的每一个 在脊髓中有一个特征性的轴突分支， 用脂溶性示踪剂充分和方便地染色。 第一步是确定哪类DRG细胞表达哪类DRG细胞。 高亲和力神经营养素受体的TrK家族成员。 大鼠 将通过逆行免疫荧光法鉴定表达不同trk的DRG细胞。 从特征性的外围和中心目标场追踪， 然后用trkA、trkB和trkC的探针进行原位杂交。 第二，我们将确定综合的发展时间进程 不同的神经营养因子在DRG的中央靶区 细胞 原位杂交在发育中的大鼠脊髓中的应用 用NGF、BDNF、NT 3和NT 5的探针进行。 表达 脊髓神经元的神经营养因子将与 不同类型DRG轴突分支的发育 通过用脂溶性示踪剂染色显示的细胞。 最后我们 将确定神经营养因子是否能影响背根轴突 在脊髓中形成分支 将注射NGF、BDNF、NT 3和NT 5 子宫内的胚胎和背根传入投射， 对照和实验动物将用Dil染色。 的 将对轴突乔木的重要特征进行定量， 与对照组和生长因子治疗组动物相比。 这些实验将确定哪种高亲和力神经营养因子 受体由已鉴定的DRG细胞类别表达， 脊髓靶区神经营养因子表达与脊髓损伤的关系 不同类别的DRG神经元的分支的发展，以及 神经营养因子是否可以影响DRG细胞的脊髓分支， vivo. 确定神经营养素对生长和发育的影响。 背根轴突在体内的分支对于评估 它们作为促进感觉轴突再生的试剂的潜力， 脊髓

The purpose of this work is to assess the influence of neuronal growth factors on axon branching in the mammalian spinal cord. The dorsal root afferent projection has been chosen as a model system because four members of the "neurotrophin" family of growth factors are known to promote neurite outgrowth of dorsal root ganglion (DRG) cells in vitro. Furthermore, each of the physiologically specified classes of DRG cells has a characteristic axonal arborization in the spinal cord that can be fully and conveniently stained with lipid-soluble tracers. A first step is to determine which classes of DRG cells express which members of the trk family of high-affinity neurotrophin receptors. Rat DRG cells expressing different trk's will be identified by retrograde tracing from characteristic peripheral and central target fields, followed by in situ hybridization with probes for trkA, trkB, and trkC. Second, we will determine the developmental time course of synthesis of the different neurotrophins in the central target fields of DRG cells. In situ hybridization in developing rat spinal cord will be performed with probes for NGF, BDNF, NT3, and NT5. Expression of neurotrophins by spinal cord neurons will be correlated with the development of axonal arborizations of the different classes of DRG cells as revealed by staining with lipid-soluble tracers. Finally, we will determine whether neurotrophins can influence dorsal root axon branching in the spinal cord. NGF, BDNF, NT3, and NT5 will in injected into embryos in utero and the dorsal root afferent projections in control and experimental animals will be stained with Dil. The important characteristics of axonal arbors will be quantitated and compared in control and growth factor-treated animals. These experiments will determine which high-affinity neurotrophin receptors are expressed by identified classes of DRG cells, the relationship of neurotrophin expression in spinal target fields to the development of arborizations of different classes of DRG neurons, and whether neurotrophins can influence the spinal arbors of DRG cells in vivo. Determining the effects of neurotrophins on the growth and branching of dorsal root axons in vivo is crucial to an assessment of their potential as agents to promote regeneration of sensory axons in the spinal cord.