STIMULI PROMOTING SURVIVAL OF SPIRAL GANGLION NEURONS

去极化是神经元的营养刺激，即，防止神经元 死亡 螺旋神经节神经元（SGN）在毛发脱落后死亡 细胞 电刺激促进去传入SGN的存活， 体内，提高了使用电刺激来维持 由于毛细胞功能丧失而失聪的人中SGN的存活。 特别是，电子耳蜗植入的功效将是 如果防止SGN死亡，则会大大增加。 为此，我们建议 旨在确定去极化机制的研究 促进SGN的生存。 这些研究利用体外 通过神经营养刺激调节SGN存活的模型。 使用 这个模型，我们发现去极化，通过增加 胞质Ca ~（2+）是比神经营养因子更强的营养刺激物。 总的目标有三个：一是进一步定性 通过去极化维持SGN存活的体外模型 和神经营养因子：（1）来自研究的分子标准 其他系统中的神经元凋亡将应用于SGN的死亡， 确定是否为凋亡。 (2)是否有不同的亚群 SGN的去极化支持能力不同， 神经营养因子？ (3)营养支持退出后多久， SGN变成了一个细胞死亡的命运？ 第二个目标是 开始研究去极化阻止 SGN的死亡会导致细胞死亡吗 第二个目标 是开始研究去极化阻止 体外SGN的死亡：（1）去极化是否通过 诱导螺旋神经节细胞的自养机制？ 各种 技术将用于检测神经营养因子的诱导， 神经营养因子受体，以及通过 培养物中神经元和非神经元细胞的去极化。 （二） 去极化是通过什么样的细胞内信号通路来实现的 营养信号 本文提出的这些研究重点是通过 MAP激酶和通过CREB家族转录因子的信号传导 因为已知这些蛋白质会被神经营养因子和 胞浆Ca ~（2+）。 分子遗传学和药理学技术将是 用于激活或抑制这些途径中的特定分子， 参与神经营养信号传导。 第三个目标是 将这些通过体外去极化进行的营养刺激的研究与 通过电刺激抑制SGN在体内的死亡。 (1)是 去传入的SGN在体内凋亡死亡？ (2)电气是否 在体内刺激去传入的SGN导致相同的分子 由去极化在体内诱导的事件： 前两个目标将识别特定的去极化引起的 与细胞存活相关的事件，例如，诱导神经营养因子。 将检查来自麻醉大鼠的电刺激耳蜗， 在体内表达这些相同的事件。

Depolarization is a trophic stimulus for neurons, i.e., prevents neuronal death. Spiral ganglion neurons (SGNs) die following the loss of hair cells. Electrical stimulation promotes survival of deafferented SGNs in vivo, raising the possibility of using electrical stimulation to maintain survival of SGNs in humans deaf as a result of loss of hair cell function. In particular, the efficacy of electronic cochlear implants would be greatly augmented if SGN death was prevented. To this end, we propose studies directed towards determining the mechanism by which depolarization promotes survival of SGNs. These studies take advantage of an in vitro model of the regulation of SGN survival by neurotrophic stimuli. Using this model, we find that depolarization, functioning by increasing cytosolic Ca2+, is a stronger trophic stimulus than neurotrophic factors. There are three general objectives: The first is to further characterize the in vitro model of the maintenance of SGN survival by depolarization and neurotrophic factors: (1) Molecular criteria derived from studies of neuronal apoptosis in other systems will be applied to the death of SGNs to determine if it is apoptotic. (2) Are there different subpopulations of SGNs that differ in their ability to be supported by depolarization and neurotrophic factors? (3) How long after withdrawal of trophic support do SGNs become committed to a cell death fate? The second objective is to initiate studies of the mechanism by which depolarization prevents the death of SGNs become committed to a cell death fate? The second objective is to initiate studies of the mechanism by which depolarization prevents the death of SGNs in vitro: (1) Does depolarization promote survival by inducing autotrophic mechanisms in the spiral ganglion cells? A variety of techniques will be used to detect induction of neurotrophic factors, neurotrophic factor receptors, and apoptosis-inhibiting genes by depolarization in neuronal and non-neuronal cells in the culture. (2) What intracellular signal pathway(s) does depolarization use to accomplish trophic signaling? These studies proposed here focus on signaling through MAP kinases and on signaling through CREB family transcription factors because these are known to be activated by neurotrophic factors and by cytosolic Ca2+. Molecular genetic and pharmacologic techniques will be used to activate or inhibit specific molecules in these pathways to assess their involvement in neurotrophic signaling . The third objective is to relate these studies of trophic stimulation by depolarization in vitro to the inhibition of SGN death in vivo by electrical stimulation. (1) Is the death of deafferented SGNs in vivo apoptotic? (2) Does electrical stimulation of deafferented SGNs in vivo result in the same molecular events that are induced in vivo by depolarization: The studies included in the first two objective will identify particular depolarization-induced events relevant to cell survival, e.g., induction of neurotrophic factors. Electrically stimulated cochlea from deafened rats will be examined for expression of these same events in vivo.