Anatomy of the Auditory System

描述(申请人提供)：噪音导致的听力损失是一种无法治愈的疾病，通常是进行性的，损害了生活质量。该项目使用动物模型，提供了证据表明，除了耳蜗毛细胞丢失外，大脑中突触终末的退化也是这种疾病的主要因素。这项研究提供了初步的数据，即随着时间的推移，耳蜗核中兴奋性和抑制性终末之间的平衡向兴奋和多动转移。总体假设是，这些变化为噪音暴露后耳鸣和听力亢进提供了结构性基础。该项目将在细胞和分子水平上描述退化过程，并追踪突触组织的变化，包括令人兴奋的发现，即在最初的损伤后可以形成新的突触。这些实验旨在发现保护突触或促进噪音后恢复的因素。用光学显微镜和电子显微镜观察小鼠耳蜗核的损伤。兴奋性和抑制性终末比例的变化将在噪声暴露后1-120天内进行量化。光镜下的突触小泡组织化学将显示终末的数目和位置。电子显微镜将使用体视学方法来验证这一假设，从而显示兴奋或抑制细胞学的结局比例。通过光学和电子显微镜的免疫细胞化学方法可以确定这些变化背后的分子。与递质相关的分子，包括兴奋性和抑制性受体和转运体，将定位于特定类型的神经元和突触，并在生存期内进行跟踪。这些数据将精确定位耳蜗核何时何地可能在细胞中发生兴奋性毒性过程。神经营养因子和受体将被识别和定位，以表明营养机制的作用。成纤维细胞生长因子的作用将在过量表达成纤维细胞生长因子的转基因小鼠中进行评估。假说是，这种因子可以防止损伤，而神经营养因子促进突触的新生长。这一结果应该会带来新疗法的建议。

DESCRIPTION (provided by applicant): Noise-induced hearing loss is an incurable, often progressive disease that impairs the quality of life. This project, using animal models, has provided evidence for degeneration of synaptic endings in the brain, besides loss of cochlear hair cells, as a major factor in this disease. This research offers preliminary data that the balance between excitatory and inhibitory endings in the cochlear nucleus shifts over time towards excitation and hyperactivity. The overall hypothesis is that these shifts provide a structural basis for tinnitus and hyperacusis after noise exposure. The project will characterize the degenerative process, at the cell and molecular levels, and trace changes in synaptic organization, including the exciting discovery that new synapses can form after the initial damage. The experiments aim to uncover factors that protect synapses or promote recovery after noise. Light and electron microscopy are used to examine damage in the cochlear nucleus of mice. Changes in the proportion of excitatory and inhibitory endings will be quantitated over 1-120 days after noise exposure. Synaptic vesicle histochemistry with light microscopy will show the numbers and locations of endings. Electron microscopy will show the proportion of endings with excitatory or inhibitory cytology using stereological approaches to test the hypothesis. Immunocytochemistry by light and electron microscopy will identify molecules underlying these changes. Transmitter-related molecules, including excitatory and inhibitory receptors and transporters, will be localized to specific types of neurons and synapses and tracked over the survival period. These data will pinpoint where and when in the cochlear nucleus an excitotoxic process may occur in cells. Neurotrophic factors and receptors will be identified and localized to indicate a role for trophic mechanisms. The role of fibroblast growth factor will be evaluated in a transgenic mouse that over expresses this factor. The hypothesis is that this factor protects against damage, and neurotrophins promote new growth of synapses. The results should lead to proposals for new therapies.