Synaptic physiology of unipolar brush cells in the dorsal cochlear nucleus

耳蜗背核单极刷细胞的突触生理学

• 批准号: 8413590
• 负责人: Carolina Borges-Merjane
• 金额: $ 4.22万
• 依托单位: OREGON HEALTH & SCIENCE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-06-30 至 2015-06-29
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8413590
• 关键词: Acoustic Nerve; Action Potentials; Affect; Affinity; Auditory; Auditory system; Brain Stem; Brush Cell; Cell Nucleus; Cells; Cellular Structures; Characteristics; Cleaved cell; Coupled; Cytoplasmic Granules; Data; Dendrites; Disease; Disinhibition; Event; Exocytosis; Fiber; Foundations; Functional disorder; Glutamates; Goals; Head and neck structure; Health; Hearing; Hyperactive behavior; Image; Interneurons; Lead; Measures; Mediating; Methods; Microscopy; Modeling; Mus; Neurotransmitters; Output; Photons; Physiologic pulse; Physiological; Physiology; Positioning Attribute; Presynaptic Terminals; Probability; Process; Property; Proprioception; Research Training; Signal Transduction; Site; Sound Localization; Structure; Synapses; Synaptic Cleft; Synaptic Receptors; Synaptic Transmission; Testing; Time; Tinnitus; Vesicle; auditory stimulus; base; dorsal cochlear nucleus; feeding; granule cell; hearing impairment; innovation; insight; mossy fiber; mouse model; multisensory; patch clamp; postsynaptic; research study; response; sound; synaptic depression; synaptic function; transmission process

DESCRIPTION (provided by applicant): The dorsal cochlear nucleus (DCN) is one of the initial structures in the mammalian brainstem that processes sound, integrating multisensory and auditory nerve input. Multisensory modulation of auditory input is a basic feature of the DCN and may be a critical contributor to tinnitus, a common hearing impairment disorders characterized by the perception of sound without exterior auditory stimulus. Although multisensory modulation of auditory input in the DCN has been shown to be important for DCN function, the synaptic and cellular mechanisms underlying synaptic transmission from multisensory fibers to its primary targets within the DCN circuitry are not well known. Multisensory input to the DCN is relayed by mossy fibers (MF), whose primary synaptic targets are granule cells (GrCs). However, a large subset of GrCs receives input through an excitatory interneuron called unipolar brush cells (UBCs). UBCs have a single short dendrite that terminates in a brush-like structure and interdigitates with a single pre-synaptic terminal, formin an unusually large excitatory synaptic contact. A previous model suggests that prolonged entrapment of glutamate in the irregular synaptic cleft underlies the characteristic slow-decaying post-synaptic current (EPSC) of UBCs. The goal of this proposal is to investigate whether UBCs temporally amplify input from MF to GrCs for further integration with auditory input, and if so, what synaptic specializations promote such amplification. We propose that multivesicular release from MF terminals contributes to prolonged glutamate in the cleft and allows UBCs to provide temporal amplification of signals to GrCs. Aim 1 will determine the physiological postsynaptic response of GrCs to UBC mediated input These experiments will directly test for the first time the effect of UBCs input to GrCs using combined imaging and electrophysiological approaches in a GFP-tagged UBC mouse through 2- photon microscopy and patch-clamp recordings from connected UBC-GrC pairs. Aim 2 will determine the mode of exocytosis at the MF-UBC synapse. Preliminary data shows low variance in amplitude of evoked EPSCs in UBC upon MF stimulation with consistent synaptic depression, therefore suggesting a high probability of release the MF-UBC synapse. The proposed experiments will investigate the mode of release at these synapses with patch-clamp recordings and the analysis of the non-equilibrium inhibition of the post- synaptic receptors by low-affinity competitive antagonists coupled to multiple-probability fluctuation analysis. Through these methods the quantal size, the number of independent release sites and the probability of release at each site can be calculated. By investigating synaptic transmission through the main structure relaying multisensory input to the DCN, and the impact of UBCs to GrC activity, this proposal will provide the foundation for understanding how the DCN early processing of multisensory input affects integration with auditory input at the principal output cells. This will characterize the first cellular contributor pertaining to the modulation and triggers of somatic tinnitus at the DCN.

描述（由申请人提供）：耳蜗背核（DCN）是哺乳动物脑干中处理声音、整合多感觉和听觉神经输入的初始结构之一。听觉输入的多感觉调制是DCN的基本特征，并且可能是耳鸣的关键因素，耳鸣是一种常见的听力障碍，其特征在于在没有外部听觉刺激的情况下感知声音。虽然DCN中听觉输入的多感觉调制已被证明对DCN功能很重要，但DCN电路中从多感觉纤维到其主要目标的突触传递的突触和细胞机制尚不清楚。DCN的多感觉输入由苔藓纤维（MF）中继，其主要突触靶是颗粒细胞（GrCs）。然而，GrCs的一个大的子集通过称为单极刷细胞（UBC）的兴奋性中间神经元接收输入。UBC具有单个短树突，其终止于刷状结构，并与单个突触前末端交错，这是一种异常大的兴奋性突触接触。先前的模型表明，谷氨酸在不规则突触间隙中的长期滞留是UBC特征性慢衰减突触后电流（EPSC）的基础。这个建议的目标是调查是否UBC暂时放大输入MF到GrCs进一步整合与听觉输入，如果是这样，什么突触专业化促进这种放大。我们建议，从MF终端的多泡释放有助于延长谷氨酸的裂缝，并允许UBC提供时间放大的信号GrCs。目的1将确定GrCs对UBC介导的输入的生理突触后反应。这些实验将通过双光子显微镜和连接的UBC-GrC对的膜片钳记录，在GFP标记的UBC小鼠中使用组合成像和电生理方法首次直接测试UBC输入对GrCs的影响。目标2将确定MF-UBC突触处的胞吐模式。初步数据显示，MF刺激后，UBC中诱发的EPSC的振幅变化较小，具有一致的突触抑制，因此表明MF-UBC突触释放的可能性很高。拟进行的实验将采用膜片钳记录和低亲和力竞争性拮抗剂对突触后受体的非平衡抑制分析结合多概率波动分析来研究这些突触的释放模式。通过这些方法，可以计算量子尺寸、独立释放位点的数目和在每个位点的释放概率。通过研究通过主要结构中继多感觉输入到DCN的突触传递，以及UBC对GrC活动的影响，该提议将为理解DCN早期处理多感觉输入如何影响与主要输出细胞的听觉输入的整合提供基础。这将表征与DCN处的躯体耳鸣的调制和触发有关的第一细胞贡献者。