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。 哺乳动物脊髓轴突分支的影响因素。背部 选择根传入投影作为模型系统是因为有四个 “神经营养因子”生长因子家族的成员已知 促进体外培养的背根神经节细胞突起生长。 此外，生理上指定的每一类DRG细胞 在脊髓中有一个特征性的轴突树枝，它可以 用脂溶示踪剂进行充分和方便的染色。 第一步是确定哪类DRG细胞表达哪些 Trk家族高亲和力神经营养因子受体的成员。大鼠 逆行鉴定表达不同trk的DRG细胞 从特征外围和中心目标区域追踪， 然后与TrkA、TrkB和trkC的探针进行原位杂交。 第二，我们将确定合成的发展时间进程 不同神经营养因子在背根神经节中心靶区的比较 细胞。原位杂交在大鼠脊髓发育中的应用 使用NGF、BDNF、NT3和NT5的探针进行检测。的表达 脊髓神经元的神经营养因子将与 不同类型背根节轴突分支的发育 脂溶性示踪剂染色显示细胞。最后，我们 将决定神经营养因子是否会影响背根轴突 在脊髓中的分支。将注射NGF、BDNF、NT3和NT5 进入子宫内的胚胎和背根的传入投射 对照和实验动物将被DIL染色。这个 轴突乔木的重要特征将被量化和 在对照和生长因子处理的动物中进行比较。 这些实验将确定哪些高亲和力神经营养因子 受体由识别的DRG细胞类别表达，即 神经营养因子在脊髓靶区的表达与脊髓损伤的关系 不同类型背根节神经元的树枝形成，以及 神经营养因子对大鼠背根神经节细胞的影响 活着。测定神经营养因子对细胞生长和生长的影响 背根轴突在活体内的分支对于评估 它们作为促进感觉神经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.