The mammalian hearing organ, the cochlea, contains an active amplifier to boost the vibrational response to low level sounds. Hallmarks of this active process are sharp location-dependent frequency tuning and compressive nonlinearity over a wide stimulus range. The amplifier relies on outer hair cell (OHC) generated forces driven in part by the endocochlear potential (EP), the ~ +80 mV potential maintained in scala media, generated by the stria vascularis. We transiently eliminated the EP in vivo by an intravenous injection of furosemide and measured the vibrations of different layers in the cochlea’s organ of Corti using optical coherence tomography. Distortion product otoacoustic emissions (DPOAE) were monitored at the same times. Following the injection, the vibrations of the basilar membrane lost the best frequency (BF) peak and showed broad tuning similar to a passive cochlea. The intra-organ of Corti vibrations measured in the region of the OHCs lost their BF peak and showed low-pass responses, but retained nonlinearity, indicating that OHC electromotility was still operational. Thus, while electromotility is presumably necessary for amplification, its presence is not sufficient for amplification. The BF peak recovered nearly fully within 2 hours, along with a non-monotonic DPOAE recovery that suggests that physical shifts in operating condition are a final step in the recovery process.

中文翻译：

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从耳蜗内电位降低中，扩增滞后于非线性恢复

哺乳动物的听力器官耳蜗包含一个有源放大器，以增强对低级声音的振动响应。这一活跃过程的标志是在广泛的刺激范围内进行精确的位置相关频率调谐和压缩非线性。该放大器依靠外部毛细胞（OHC）产生的力，该力部分由耳蜗内电位（EP）驱动，该内耳电位是由血管纹产生的，在sc骨介质中保持的〜+80 mV电位。我们通过静脉内注射速尿来体内消除EP，并使用光学相干断层扫描技术测量了Corti耳蜗器官不同层的振动。同时监测失真产物的耳声发射（DPOAE）。注射后 基底膜的振动失去了最佳频率（BF）峰值，并表现出类似于被动耳蜗的宽调谐。在OHC区域内测量的器官内Corti振动丢失了其BF峰并显示出低通响应，但保留了非线性，这表明OHC电动力仍然有效。因此，虽然电动势可能是扩增所必需的，但其存在不足以进行扩增。高炉峰在2小时内几乎完全恢复，并且非单调DPOAE恢复表明操作条件的物理变化是恢复过程的最后一步。表明OHC电动性仍在运行。因此，虽然电动势可能是扩增所必需的，但其存在不足以进行扩增。高炉峰在2小时内几乎完全恢复，并且非单调DPOAE恢复表明操作条件的物理变化是恢复过程的最后一步。表明OHC电动性仍在运行。因此，虽然电动势可能是扩增所必需的，但其存在不足以进行扩增。高炉峰在2小时内几乎完全恢复，并且非单调DPOAE恢复表明操作条件的物理变化是恢复过程的最后一步。