Inhibition Shapes Acoustic Responsiveness in Spherical Bushy Cells
Inhibition Shapes Acoustic Responsiveness in Spherical Bushy Cells
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DOI：
10.1523/jneurosci.0133-15.2015
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发表时间：
2015-06-03
影响因子：
5.3
通讯作者：
Ruebsamen, Rudolf
中科院分区：
文献类型：
--
作者：
Keine, Christian;Ruebsamen, Rudolf
听觉脑干中的信号处理基于神经元兴奋和抑制的相互作用。迄今为止，我们还不完全了解两者的动态相互作用如何影响信号编码的处理能力和时间特性。前腹侧耳蜗核 (AVCN) 的球形丛状细胞 (SBC) 通过听觉神经纤维通过称为 Held 端球的大型轴体突触末端以及额外的声驱动抑制输入接收主要兴奋性输入。 SBC 为脑干声源定位电路的下游核提供输入，例如依赖于时间精确输入的内侧和外侧上橄榄。在这项研究中，我们使用麻醉蒙古沙鼠的近细胞记录来评估声诱发抑制对 SBC 输入输出功能和 SBC 尖峰时间精度的影响。声诱发抑制被证明足以以刺激依赖性方式抑制 SBC 的动作电位 (AP)。抑制表现出缓慢的起始和抵消动态以及在较高声音强度下强度的增加。此外，抑制降低了 EPSP 的上升斜率并延长了 EPSP 到 AP 的过渡时间。这两种效果都可以通过甘氨酸的离子电渗疗法来模拟。抑制还可以通过充当增益控制来抑制不合时宜的 EPSP 生成突触后 AP，从而在声音强度范围内保持精确的 SBC 尖峰，从而改善 SBC AP 与低频音调的锁相。目前的数据表明，抑制极大地提高了上行听觉系统中二级神经元的处理能力。
Signal processing in the auditory brainstem is based on an interaction of neuronal excitation and inhibition. To date, we have incomplete knowledge of how the dynamic interplay of both contributes to the processing power and temporal characteristics of signal coding. The spherical bushy cells (SBCs) of the anteroventral cochlear nucleus (AVCN) receive their primary excitatory input through auditory nerve fibers via large, axosomatic synaptic terminals called the endbulbs of Held and by additional, acoustically driven inhibitory inputs. SBCs provide the input to downstream nuclei of the brainstem sound source localization circuitry, such as the medial and lateral superior olive, which rely on temporal precise inputs. In this study, we used juxtacellular recordings in anesthetized Mongolian gerbils to assess the effect of acoustically evoked inhibition on the SBCs input-output function and on temporal precision of SBC spiking. Acoustically evoked inhibition proved to be strong enough to suppress action potentials (APs) of SBCs in a stimulus-dependent manner. Inhibition shows slow onset and offset dynamics and increasing strength at higher sound intensities. In addition, inhibition decreases the rising slope of the EPSP and prolongs the EPSP-to-AP transition time. Both effects can be mimicked by iontophoretic application of glycine. Inhibition also improves phase locking of SBC APs to low-frequency tones by acting as a gain control to suppress poorly timed EPSPs from generating postsynaptic APs to maintain precise SBC spiking across sound intensities. The present data suggest that inhibition substantially contributes to the processing power of second-order neurons in the ascending auditory system.