POSTSYNAPTIC TRANSDUCTION IN THE COCHLEAR NUCLEUS

耳蜗核中的突触后转导

• 批准号: 2127503
• 负责人: WILLIAM J SPAIN
• 金额: $ 10.51万
• 依托单位: UNIVERSITY OF WASHINGTON
• 依托单位国家: 美国
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-06-01 至 1998-05-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2127503
• 关键词: action potentials; chickens; cochlear nerve; electrophysiology; inhibitor /antagonist; neural transmission; neuroanatomy; neuropharmacology; potassium channel; sodium channel; synapses; tetrodotoxin

This project investigates the membrane properties of neurons from the avian cochlear nucleus, the nucleus magnocellularis (NM). The NM contains the cells which are homologous to the bushy cells of the mammalian anteroventral cochlear nucleus. NM neurons project to nucleus laminaris neurons which underlie the spatial localization of sound by generating action potentials in response to appropriately timed inputs from the ipsilateral and contralateral NM. In order for accurate localization of sound, NM neurons must relay precise timing information about the auditory stimulus. Stimulation of the auditory nerve results in rapid volleys of EPSPs in NM neurons. Since NM neurons fire action potentials in response to AC inputs but not to DC inputs, temporal summation of the EPSPs would not produce firing of action potentials in NM neurons. We have shown that there is a K+ current in NM neurons which causes the large synaptic potentials to decay rapidly with minimal temporal summation. The NM is tonotopically organized: neurons in the posterolateral NM receive auditory nerve inputs activated by the lowest sound frequencies while those in the anteromedial NM receive inputs activated by the highest sound frequencies. An intriguing question is whether there are differences in the membrane properties that permit anteromedial NM neurons to respond best to high frequency stimuli and posterolateral NM neurons to respond best to low frequency stimuli. We have evidence that the membrane properties do indeed vary because action potential threshold is more depolarized in NM neurons from the anterior region of the nucleus than neurons from the posterior region. The aim of this proposal is to determine how transduction properties of NM neurons vary along the tonotopic axis. The hypotheses to be tested are: I. Hypothesis: NM neurons contain several different types of K+ channels and their expression varies along the tonotopic axis. 2. Hypothesis: The density and/or characteristics of Na+ channels vary along the tonotopic axis of NM. 3. Hypothesis: The tonotopic variation of NM neuron membrane properties results in response properties that differ along the tonotopic axis. The electrotonically compact NM neurons are ideal central neurons for voltage-clamp studies. The K+ and Na+ conductances will be isolated in vitro and their contribution to post-synaptic transduction will be mapped with respect to the position of the cells on the tonotopic axis. This study will provide basic information about how the auditory system works. It will also provide a foundation for future investigations about how ion channel expression is regulated over space.

该项目研究了来自神经元的膜特性。 鸟类耳蜗核，即大细胞核（NM）。NM包含 与哺乳动物的丛状细胞同源的细胞 耳蜗前腹侧核 NM神经元投射至板层核 神经元是声音空间定位的基础， 动作电位响应于适当定时的输入， 同侧和对侧NM。为了准确定位 声音，NM神经元必须传递关于听觉的精确定时信息， 刺激。刺激听神经会导致快速的 NM神经元的EPSPs。由于NM神经元在反应中激发动作电位， 对于AC输入而不是DC输入，EPSP的时间求和将 在NM神经元中不产生动作电位的放电。我们已经证明 在NM神经元中存在K+电流，其引起大的突触 以最小的时间总和迅速衰减的电位。 核束的结构是有张力的：后外侧核束的神经元 接收由最低声音频率激活的听觉神经输入 而前内侧NM中的神经元则接收由最高的 声音频率一个有趣的问题是， 在允许前内侧NM神经元响应的膜特性中， 最好对高频刺激和后外侧核神经元作出反应 最好是低频刺激。我们有证据表明 特性确实不同，因为动作电位阈值 去极化的NM神经元从前面的区域的核比 后区的神经元。 该建议的目的是确定NM的转导特性如何 神经元沿着音调轴变化。待检验的假设为： I.假设：NM神经元含有几种不同类型的K+通道 并且它们的表达沿音调拓扑轴沿着变化。 2.假设：Na+通道的密度和/或特征不同 沿着NM的色调轴。 3.假设：NM神经元膜特性的色调变化 导致响应特性沿音调拓扑轴沿着不同。 电紧张致密的NM神经元是理想的中枢神经元， 电压钳研究。K+和Na+电导将被隔离， 体外和他们的贡献突触后转导将被映射 相对于细胞在音调拓扑轴上的位置。 这项研究将提供有关听觉系统如何 工程.它还将为未来的调查提供基础， 离子通道的表达是如何在空间上被调节的。