Chan Dylan K, Hudspeth A J
Howard Hughes Medical Institute and Laboratory of Sensory Neuroscience, The Rockefeller University, New York, New York 10021-6399, USA.
Biophys J. 2005 Dec;89(6):4382-95. doi: 10.1529/biophysj.105.070474. Epub 2005 Sep 16.
The detection of sound by the cochlea involves a complex mechanical interplay among components of the cochlear partition. An in vitro preparation of the second turn of the jird's cochlea provides an opportunity to measure cochlear responses with subcellular resolution under controlled mechanical, ionic, and electrical conditions that simulate those encountered in vivo. Using photodiode micrometry, laser interferometry, and stroboscopic video microscopy, we have assessed the mechanical responses of the cochlear partition to acoustic and electrical stimuli near the preparation's characteristic frequency. Upon acoustic stimulation, the partition responds principally as a rigid plate pivoting around its insertion along the spiral lamina. The radial motion at the reticular lamina greatly surpasses that of the tectorial membrane, giving rise to shear that deflects the mechanosensitive hair bundles. Electrically evoked mechanical responses are qualitatively dissimilar from their acoustically evoked counterparts and suggest the recruitment of both hair-bundle- and soma-based electromechanical transduction processes. Finally, we observe significant changes in the stiffness of the cochlear partition upon tip-link destruction and tectorial-membrane removal, suggesting that these structures contribute considerably to the system's mechanical impedance and that hair-bundle-based forces can drive active motion of the cochlear partition.
耳蜗对声音的检测涉及耳蜗隔板各组成部分之间复杂的机械相互作用。沙鼠耳蜗第二圈的体外制备提供了一个机会，可在模拟体内条件的可控机械、离子和电条件下，以亚细胞分辨率测量耳蜗反应。利用光电二极管测微术、激光干涉测量法和频闪视频显微镜，我们评估了耳蜗隔板在制剂特征频率附近对声学和电刺激的机械反应。在声学刺激下，隔板主要表现为围绕其沿螺旋板插入处枢转的刚性板。网状板处的径向运动大大超过盖膜的径向运动，从而产生使机械敏感毛束偏转的剪切力。电诱发的机械反应在性质上与其声学诱发的对应反应不同，这表明基于毛束和体细胞的机电转导过程均被激活。最后，我们观察到在破坏顶连接和去除盖膜后，耳蜗隔板的刚度发生了显著变化，这表明这些结构对系统的机械阻抗有很大贡献，并且基于毛束的力可以驱动耳蜗隔板的主动运动。
