Transmitter Release from Cochlear Hair Cells Is Phase Locked to Cyclic Stimuli of Different Intensities and Frequencies
Transmitter Release from Cochlear Hair Cells Is Phase Locked to Cyclic Stimuli of Different Intensities and Frequencies
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DOI：
10.1523/jneurosci.0457-12.2012
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发表时间：
2012-11-21
影响因子：
5.3
通讯作者：
Goutman, Juan D.
中科院分区：
文献类型：
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作者：
Goutman, Juan D.
听觉系统通过独立的脑干通路处理时间和强度，以获得空间位置以及声音的其他显著特征。时间和强度的独立编码开始于耳蜗，传入神经元可以在宽范围的刺激强度中以恒定相位激发动作电位。我们研究了大鼠毛细胞-传入突触的突触前和突触后同步记录的时间和强度编码。列车的去极化步骤的毛细胞被用来引发突触后电流发生在恒定的相位为一系列的膜电位超过释放概率变化显着。为了探索潜在的机制，使用单步到各种命令电压来检查释放。正如囊泡释放所预期的那样，随着突触前钙内流的增加，第一个突触事件发生得更早。然而，突触抑制产生较小的反应与较长的第一个潜伏期。因此，在重复的毛细胞刺激期间，由于毛细胞更强烈地去极化，增加的钙通道门控加快了递质的释放，但由此产生的囊泡消耗产生了补偿性减慢。丝带功能的定量模拟表明，这两个因素随着毛细胞去极化（刺激强度）的相互变化而产生恒定的突触相位。最后，我们建议，所观察到的快速囊泡补充将有助于维持囊泡池，这反过来又会平衡的刺激强度（因此开放的Ca 2+通道的数量），使列车的不同水平的平均阶段将被保存。
The auditory system processes time and intensity through separate brainstem pathways to derive spatial location as well as other salient features of sound. The independent coding of time and intensity begins in the cochlea, where afferent neurons can fire action potentials at constant phase throughout a wide range of stimulus intensities. We have investigated time and intensity coding by simultaneous presynaptic and postsynaptic recording at the hair cell-afferent synapse from rats. Trains of depolarizing steps to the hair cell were used to elicit postsynaptic currents that occurred at constant phase for a range of membrane potentials over which release probability varied significantly. To probe the underlying mechanisms, release was examined using single steps to various command voltages. As expected for vesicular release, first synaptic events occurred earlier as presynaptic calcium influx grew larger. However, synaptic depression produced smaller responses with longer first latencies. Thus, during repetitive hair cell stimulation, as the hair cell is more strongly depolarized, increased calcium channel gating hurries transmitter release, but the resulting vesicular depletion produces a compensatory slowing. Quantitative simulation of ribbon function shows that these two factors varied reciprocally with hair cell depolarization (stimulus intensity) to produce constant synaptic phase. Finally, we propose that the observed rapid vesicle replenishment would help maintain the vesicle pool, which in turn would equilibrate with the stimulus intensity (and therefore the number of open Ca2+ channels), so that for trains of different levels the average phase will be conserved.