Center for Hearing and Communication Research, Karolinska Institutet, Department of Clinical Neuroscience, M1 Karolinska University Hospital, Stockholm, Sweden.
Biophys J. 2011 Jun 8;100(11):2586-94. doi: 10.1016/j.bpj.2011.05.002.
Acoustic stimulation gates mechanically sensitive ion channels in cochlear sensory hair cells. Even in the absence of sound, a fraction of these channels remains open, forming a conductance between hair cells and the adjacent fluid space, scala media. Restoring the lost endogenous polarization of scala media in an in vitro preparation of the whole cochlea depolarizes the hair cell soma. Using both digital laser interferometry and time-resolved confocal imaging, we show that this causes a structural refinement within the organ of Corti that is dependent on the somatic electromotility of the outer hair cells (OHCs). Specifically, the inner part of the reticular lamina up to the second row of OHCs is pulled toward the basilar membrane, whereas the outer part (third row of OHCs and the Hensen's cells) unexpectedly moves in the opposite direction. A similar differentiated response pattern is observed for sound-evoked vibrations: restoration of the endogenous polarization decreases vibrations of the inner part of the reticular lamina and results in up to a 10-fold increase of vibrations of the outer part. We conclude that the endogenous polarization of scala media affects the function of the hearing organ by altering its geometry, mechanical and electrical properties.
声刺激门控耳蜗感觉毛细胞中的机械敏感离子通道。即使在没有声音的情况下，这些通道的一部分仍然保持开放，在毛细胞和相邻的液腔（中阶）之间形成电导。在整个耳蜗的体外标本中恢复中阶失去的内源性极化会使毛细胞体去极化。我们使用数字激光干涉测量法和时间分辨共聚焦成像，表明这会导致柯蒂氏器内的结构细化，这取决于外毛细胞（OHC）的体电动性。具体而言，网状板的内部分（直到第二排 OHC）被拉向基底膜，而外部分（第三排 OHC 和 Hensen 细胞）出人意料地向相反方向移动。对于声音诱发的振动，也观察到类似的分化反应模式：恢复内源性极化会降低网状板内部分的振动，并导致外部分的振动增加多达 10 倍。我们得出结论，中阶的内源性极化通过改变其几何形状、机械和电学特性来影响听觉器官的功能。
