Mechanisms of cochlear synaptopathy after noise or blast trauma

项目摘要/摘要 大约15%的美国人因暴露在噪音中而听力受损。经典的解释是对 耳蜗毛细胞。噪音导致听力损失的另一种机制是耳蜗性突触。那里 临床上是否没有有效的治疗方法来预防创伤性噪音后的听力损失？ 曝光。最近，我们发现内淋巴积水发生在冲击波或噪声创伤后，并且 内淋巴积水与耳蜗性突触有关。我们的中心假设是内淋巴管 水肿症是谷氨酸引起的听神经树突肿胀的替代标志物 兴奋性毒性。我们将通过三个目标来检验这一假设。首先，我们将确定听觉肿胀是否 神经树突与内淋巴积水相关。我们将在体内测量Scala介质的体积 使用体积光学相干层析成像和振动测量(VOCTV)。我们会同时想象 用双光子显微镜观察活体听神经纤维终末并测量其直径。第二，我们将 确定急性毛细胞功能障碍是否有必要产生以下生理后果 耳蜗性突触病。我们将用VOCTV测量基底膜振动调谐曲线来评估 耳蜗生理学。我们还将测量第一波听觉脑干反应(ABR)的峰间 波幅以评估听神经生理学。第三，我们将确定 耳蜗性突触病变是谷氨酸、内淋巴积水或树突状肿胀。我们将衡量Scala 噪声或低张刺激后受损小鼠的媒体音量、耳蜗增益和突触计数 转导或损害IHC-听神经突触的谷氨酸释放。因此，我们提议 最终证明或反驳我们的假设。此外，我们将了解生理后果 以及内淋巴积水和突触形成的机制。

Project Summary/Abstract About 15% of Americans have hearing loss due to noise exposure. The classical explanation is trauma to the cochlear hair cells. An additional mechanism of noise-induced hearing loss is cochlear synaptopathy. There are no effective treatments used clinically to prevent hearing loss via either mechanism after traumatic noise exposure. Recently, we identified that endolymphatic hydrops occurs after blast or noise trauma, and that endolymphatic hydrops correlated with cochlear synaptopathy. Our central hypothesis is that endolymphatic hydrops is a surrogate marker for swelling of auditory nerve dendrites that occurs in response to glutamate excitotoxicity. We will test this hypothesis with three aims. First, we will determine whether swelling of auditory nerve dendrites correlates with endolymphatic hydrops. We will measure the volume of scala media in vivo using volumetric optical coherence tomography and vibrometry (VOCTV). We will simultaneously image auditory nerve fiber terminals in vivo with two-photon microscopy and measure their diameter. Second, we will determine whether acute hair cell dysfunction is necessary to produce the physiological consequences of cochlear synaptopathy. We will measure basilar membrane vibratory tuning curves using VOCTV to assess cochlear physiology. We will also measure the wave 1 auditory brainstem response (ABR) peak-to-peak amplitude to assess auditory nerve physiology. Third, we will determine whether the inciting mechanism of cochlear synaptopathy is glutamate, endolymphatic hydrops, or dendritic swelling. We will measure scala media volume, cochlear gain, and synaptic counts after noise or hypotonic challenge in mice with impaired transduction or impaired glutamate release at the IHC-auditory nerve synapse. Therefore, we are proposing to definitively prove or disprove our hypothesis. Furthermore, we will understand the physiological consequences and mechanisms of endolymphatic hydrops and synaptopathy.