Cheatham M A, Dallos P
Hugh Knowles Center, Northwestern University, Evanston, Illinois 60208-3550, USA.
J Acoust Soc Am. 1999 Feb;105(2 Pt 1):799-810. doi: 10.1121/1.426269.
Inner hair cell (IHC) responses are recorded from the apical three turns of the guinea pig cochlea in order to define the relationship between hair cell depolarization and position of the basilar membrane. At low frequencies, inner hair cell depolarization is generally observed near basilar membrane velocity to scala vestibuli, reflecting the putative freestanding nature of the IHC's stereocilia. While this is consistent with previous IHC results, independent of location, and with neural responses for fibers with low best frequencies, it is inconsistent with single-unit results from the base of the cochlea, where response phase is associated with basilar membrane velocity to scala tympani. Results suggest that the temporal disparity between IHC and neural data from the base of the cochlea may relate to several factors that influence transmembrane voltage in IHCs. First, extracellular voltages (Ingvarsson, 1981; Sellick et al., 1982; Russell and Sellick, 1983) can potentially affect low- and high-frequency regions differently because electrical interactions are more likely in the base of the cochlea than in the apex (Dallos, 1983, 1985). Second, waveform distortion and kinetic properties associated with voltage-dependent ion channels in the IHC's basolateral membrane can both influence response phase by adding harmonic components and lagging the receptor potential by as much as 90 deg. Third, the velocity dependence of IHCs in the apex appears to extend to higher frequencies than the velocity dependence demonstrated for IHCs in the base of the cochlea. These features, which influence the timing of discharges in the auditory nerve, are compared and evaluated.
为了确定毛细胞去极化与基底膜位置之间的关系，我们记录了豚鼠耳蜗顶部三圈的内毛细胞（IHC）反应。在低频时，通常在基底膜朝向前庭阶的速度附近观察到内毛细胞去极化，这反映了内毛细胞静纤毛假定的独立性质。虽然这与先前的内毛细胞结果一致，与位置无关，也与最佳频率较低的纤维的神经反应一致，但与耳蜗底部的单单元结果不一致，在耳蜗底部，反应相位与基底膜朝向鼓阶的速度相关。结果表明，耳蜗底部内毛细胞与神经数据之间的时间差异可能与影响内毛细胞跨膜电压的几个因素有关。首先，细胞外电压（英瓦尔松，1981年；塞利克等人，1982年；拉塞尔和塞利克，1983年）可能对低频和高频区域产生不同的影响，因为耳蜗底部比顶部更可能发生电相互作用（达洛斯，1983年，1985年）。其次，与内毛细胞基底外侧膜中电压依赖性离子通道相关的波形失真和动力学特性，都可以通过添加谐波成分和使感受器电位滞后多达90度来影响反应相位。第三，耳蜗顶部内毛细胞的速度依赖性似乎延伸到比耳蜗底部内毛细胞所显示的速度依赖性更高的频率。我们对这些影响听神经放电时间的特征进行了比较和评估。
