STIMULI PROMOTING SURVIVAL OF SPIRAL GANGLION NEURONS

去极化是一种对神经元的营养刺激，即阻止神经元 死亡。螺旋神经节神经元(SGN)在脱发后死亡 细胞。电刺激促进去传入神经节存活 活体，增加了使用电刺激维持 由于毛细胞功能丧失，人类耳聋患者SGN的存活率。 特别是，电子耳蜗植入物的功效将是 如果防止SGN死亡，则会大大增加。为此，我们建议 旨在确定去极化的机制的研究 促进SGN的生存。这些研究利用了体外实验的优势 神经营养刺激调节SGN存活的模型。vbl.使用 这个模型，我们发现去极化，功能是通过增加 细胞内钙离子是一种比神经营养因子更强的营养刺激。 有三个总体目标：第一个是进一步描述 去极化维持SGN存活的体外模型 和神经营养因子：(1)分子标准源于对 其他系统中的神经元凋亡将应用于SGN的死亡 确定它是否为凋亡性疾病。(2)是否有不同的亚群 不同的SGN由去极化和 神经营养因子？(3)停用营养支持多长时间 SGN变得致力于细胞死亡的命运？第二个目标是 开始研究去极化阻止 SGN的死亡变成了细胞死亡的命运？第二个目标 就是开始研究去极化阻止 SGN的体外死亡：(1)去极化是否通过以下途径促进存活 诱导螺旋神经节细胞的自养机制？各种各样的 技术将被用来检测神经营养因子的诱导， 神经营养因子受体和细胞凋亡抑制基因 培养中神经细胞和非神经细胞的去极化。(2) 细胞内信号通路(S)是用来实现去极化的 营养信号？这里提出的这些研究重点是通过信号传递 MAP激酶与CREB家族转录因子介导的信号转导 因为已知它们被神经营养因子激活，并通过 胞内钙离子。分子遗传学和药理学技术将是 用来激活或抑制这些通路中的特定分子以评估 它们参与神经营养信号的传递。第三个目标是 将这些体外去极化营养刺激的研究与 电刺激对SGN体内死亡的抑制作用(1)是 去传入神经节在体内的死亡？(2)电信号 刺激去传入的SGN在体内产生相同的分子 由去极化在体内诱导的事件：包括在 前两个目标将识别特定去极化诱导 与细胞存活有关的事件，例如，神经营养因子的诱导。 对耳聋大鼠的电刺激耳蜗组织进行检查 在活体中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.