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ON THE SIGNAL TRANSDUCTION MECHANISMS AT THE SECONDARY AND THE TERTIARY COCHLEAR NUCLEL

耳蜗二级核和三级核信号传导机制的探讨

基本信息

批准号：
05680719
负责人：
KOYANO Konomi
金额：
$ 1.41万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

项目摘要

Avian magno cellular nucleus (NMC) is one of cochlear nuclei which is known to encode the temporal information of sound. The higher auditory nuclei are supposed to detect interaural time difference to locate a sound origin using the temporal information from NMC.In this project, we investigated the membrane properties and ionic currents of the NMC neuron which enable to carry the temporal information of sound using a whole-cell recording form brain stcm slice preparation of a chick embryo. Under current-clamp condition, NMC neuron showed Na-dependent action potentials with a threshold of about-44mV.The neuron generated only a single action potential with a fixed timing at the initial phase of depolarizing current stimuli. This excitable nature was independent from the intensity and the duration of the current stimuli. This characteristic excitability is seemed to be useful to carry the temporal information of the sound. In voltage-clamp condition, the neurone revealed a TTX-sensitive Na current, a low voltage activated (LVA) Ca current and a high voltage (HVA) Ca current. The LVA Ca current and the HVA Ca current were sensitive to Ni (0.1mM) and nifedipime (20 muM) , respectively. The neuron showed at least a TEA-sensitive K.current and a 4-AP-sensitive K current. In the presence of 4-AP (0.5 mM) , the NMC neuron generated multiple action potentials from a lower threshold, in response to long depolarizing current injections. The onset of spikes showed marked fluctuation at smaller current injections. Ni (0.1 mM) prevented effects of 4-AP on the threshold value and the variability of action potential onsets. In voltage clamp experiment, 4-AP uncovered the LVA Ca current at more negative potential than the normal action potential threshold of-44mV.We have conchuded that a 4-AP-sensitive K current overcomes the LVA Ca current to set a higher threshold level to generate a single action potential at the initial phase of synaptic inputs.

鸟类的大细胞核（NMC）是编码声音时间信息的耳蜗核团之一。本研究利用鸡胚脑stcm切片全细胞记录技术，研究了携带声时信息的神经元膜特性和离子电流。在电流钳条件下，NMC神经元表现出钠依赖性动作电位，阈值约为-44mV。在去极化电流刺激的起始相，该神经元只产生单一的动作电位，且时间固定。这种兴奋性与电流刺激的强度和持续时间无关。这种特征性的兴奋性似乎是有用的携带时间信息的声音。在电压钳条件下，神经元显示一个TTX敏感的Na电流，一个低电压激活（LVA）的Ca电流和一个高电压（HVA）的Ca电流。LVA Ca电流和HVA Ca电流分别对Ni（0.1mM）和硝苯啶（20 μ M）敏感。该神经元至少显示出TEA敏感的钾电流和4-AP敏感的钾电流。在4-AP（0.5 mM）的存在下，NMC神经元产生多个动作电位从一个较低的阈值，响应于长的去极化电流注射。尖峰的出现在较小的电流注入显示出显着的波动。镍（0.1 mM）阻止4-AP对阈值和动作电位起始的变异性的影响。在电压钳实验中，4-AP在比正常动作电位阈值（-44mV）更负的电位上显示了LVA Ca电流。我们认为，4-AP敏感的K电流克服了LVA Ca电流，从而在突触输入的起始相设置了更高的阈值水平，产生了单一的动作电位。