NGF MODULATION OF SENSORY NEURON ACTION POTENTIALS

这些研究涉及调节背神经元的兴奋性。 根神经节（DRG）神经元的生长因子（GF）。 DRG神经元AP是 其特征在于复极化阶段的“平台”，这是由于 内向Ca++电流 我们已经证明，神经生长因子（NGF） 缩短AP的持续时间（APD）在2天内暴露，当 DRG神经元不再需要NGF来存活。 APD反转至更长 暴露于抗NGF后1天内的持续时间。 这项研究的目的之一是 为了确定NGF对神经元细胞的作用的离子电导变化， APD。 分析将使用胚胎的3周龄分离培养物， 新生儿和成人DRG神经元。 首先，通过细胞内和全细胞 记录APD的（电流钳）测量值、过冲大小 后超极化相（AHP）的振幅和持续时间将是 在对照组和神经生长因子处理的神经元中进行比较。 二、系统分析 的离子电导介导这些参数将进行 使用全细胞电压钳记录。 可能的NGF依赖性 待定量的改变将包括那些电压依赖性Ca++ （N，L，T）和K+（延迟整流，A电流，K（ca））电导。 受NGF影响的宏观电流将通过特定的通道进行识别 阻滞剂。 可以检测到APD缩短的最早时间将 下定决心。 合成机制可能介导这一效应 将使用RNA和蛋白质合成抑制剂进行测试。 其他GF， 神经营养活性（碱性成纤维细胞生长因子、表皮生长 因子、胰岛素样生长因子、胰岛素和脑源性神经营养因子 因素）将测试其改变DRG兴奋性的能力 特性. 此外，本身不是生长因子但 对DRG神经元具有神经营养活性（8-取代的cAMP类似物） 会得到考验 如果这些分子是活性的，则它们的离子基础 将其效果与NGF的效果进行比较。 协同效应 将研究NGF和其他GF对DRG兴奋性的影响。 这些研究可以确定，NGF和其他神经营养性GF可以 调节神经元的生理特性，而不受对 生存 一个长期的目标是了解分子调控 在成熟的神经系统中，神经营养因子对通道的影响。 这可能 可用于治疗某些神经变性疾病。

These studies concern regulation of the excitability properties of dorsal root ganglion (DRG) neurons by growth factors (GFs). The DRG neuron AP is characterized by a "plateau" on the repolarizing phase which is due to an inward Ca++ current. We have demonstrated that nerve growth factor (NGF) shortens the duration of the AP (APD) within 2 days for exposure when the DRG neurons no longer require NGF for survival. The APD reverses to longer duration within 1 day after exposure to anti-NGF. One aim of this study is to identify the ionic conductance changes underlying the effect of NGF on the APD. Analysis will use 3-week old dissociated cultures of embryonic, neonatal and adult DRG neurons. First, by intracellular and whole-cell recording (current clamp) measurements of the APD, size of the overshoot and amplitude and duration of the after hyperpolarizing phase (AHP) will be compared in control and NGF-treated neurons. Second, systematic analysis of the ionic conductances mediating these parameters will be carried out using whole-cell voltage clamp recording. Possible NGF-dependent alterations to be quantitated will include those n voltage-dependent Ca++ (N,L,T) and K+ (delayed rectifier, A current, K(ca)) conductances. Macroscopic currents affected by NGF will identified with specific channel blockers. The earliest time at which APD shortening can be detected will be determined. Possible mediation of this effect by synthetic mechanisms will be tested using RNA and protein synthesis inhibitors. Other GFs with neurotrophic activities (basic fibroblast growth factor, epidermal growth factor, insulin-like growth factor, insulin, and brain-derived neurotrophic factor) will be tested for their capacities to alter DRG excitability properties. Also, compounds which are not growth factors per se, but which have neurotrophic activities on DRG neurons (8-substituted cAMP analogs) will be tested. If such molecules are active, the ionic basis of their effects will be compared with those for NGF. Synergistic effects between NGF and other GFs on DRG excitability properties will be investigated. These studies could establish that NGF and other neurotrophic GFs can modulate physiological properties of neurons independently from effects on survival. A long-term objective is to understand the molecular regulation of channels by neurotrophic factors in the mature nervous system. This may be useful in the treatment of certain neurodegenerative diseases.