Molecular neuroanatomy of the cochlear nucleus in deafness

描述（由申请人提供）：我们的长期目标是了解听力和耳聋在传递受体的分布和表达中的作用。在本研究中，我们将重点关注听觉神经-耳蜗核（CN）界面，并特别关注三个主要投射神经元的突触回路：耳蜗核背侧的梭状细胞（FC）和耳蜗核前腹侧的球状和球形丛状细胞（GBC和SBC）。这些细胞在整合来自不同来源的聚合突触输入中起着关键作用。它们构成了启动上行听觉通路的神经元群的一部分，通过上行听觉通路，听觉信息被传递到更高的中枢。在这项建议中，我们有两个具体目标。在Aim 1中，我们将确定听力损失是否以及在多大程度上导致FC、GBC和SBC突触后膜谷氨酸受体的表达和亚基组成发生变化，而不是听神经突触。本研究将利用卡铂诱导的感音神经性耳聋来验证耳聋后谷氨酸突触分子组成发生变化的假设。我们将使用免疫金标记和电子显微镜检查耳聋对这些细胞上受体亚基的分布和类型的影响，并将其与听力正常的同伴进行比较。在目标2中。我们将确定传导性听力损失是否会导致FC、GBC和SBC突触后膜谷氨酸、甘氨酸和GABAA受体的表达和亚基组成的变化。我们将测试这一假设，即减少声刺激会导致类似类型的受体重塑。使用耳塞，我们将尝试确定“听力减少”对这些CN神经元上谷氨酸、甘氨酸和GABA受体表达的影响。该研究结合了三维重建和形态计量学分析以及光学和电子显微镜水平的定量免疫细胞化学。通过这些研究，我们将确定感音神经性和传导性听力损失对耳蜗核主要神经元的直接形态学和分子变化。这些研究结果可能揭示耳聋和听神经活动丧失引起的分子变化的本质。它们将与先天性耳聋患者试图保留或替代听力（通过人工耳蜗植入）的策略直接相关，并可能导致耳鸣的治疗范式。本研究将在谷氨酸能脑可塑性和听觉神经生物学领域做出新的贡献。

DESCRIPTION (provided by applicant): Our long-term goal is to understand the role of hearing and deafness in the distribution and expression of transmitter receptors. In this proposal, we will focus on the auditory nerve-cochlear nucleus (CN) interface with a special focus on the synaptic circuitry of three principal projection neurons: the fusiform cell (FC) in the dorsal cochlear nucleus, and globular and spherical bushy cells (GBC and SBC) in the anteroventral cochlear nucleus. These cells play key roles in the integration of converging synaptic inputs from diverse sources. They form part of the neuron population that initiates the ascending auditory pathways by which auditory information is communicated to higher centers. In this proposal, we have two specific objectives. In Aim 1, we will determine whether and to what extent hearing loss leads to changes on the expression and subunit composition of glutamate receptors at the postsynaptic membrane of FC, GBC and SBC opposed to auditory nerve synapses. This study will use carboplatin-induced sensorineural deafness to test the hypothesis that the molecular composition of the glutamate synapse will change after deafening. We will use immunogold labeling and electron microscopy to examine the effects of deafness on the distribution and type of receptor subunits on these cells as compared to that found in hearing littermates. In Aim 2. we will determine whether conductive hearing loss leads to changes in the expression and subunit composition of glutamate, glycine and GABAA receptors at the postsynaptic membrane of FC, GBC and SBC. We will test the hypothesis that a reduction in acoustic stimulation leads to similar types of receptor remodeling. Using ear plugs, we will attempt to determine the effects of "hearing reduction" on the expression of glutamate, glycine and GABA receptors on these CN neurons. The proposed research combines 3-D reconstruction and morphometric analysis together with quantitative immunocytochemistry at the light and electron microscopy level. Through these studies we will determine the immediate morphological and molecular changes caused by sensorineural and conductive hearing loss on the main neurons in the cochlear nucleus. The results of these studies may reveal the nature of molecular change induced by deafness and loss of auditory nerve activity. They will have direct relevance to strategies that attempt to preserve or replace hearing (via cochlear implants) in cases of congenital deafness, and may lead to treatment paradigms for tinnitus. The proposed research will make novel contributions to the field of glutamatergic brain plasticity and auditory neurobiology.