Zimmermann U, Fermin C
Department of Otolaryngology, University of Tübingen, Germany.
Acta Otolaryngol. 1996 May;116(3):395-400. doi: 10.3109/00016489609137863.
Cochlear outer hair cells (OHC) are commonly assumed to function as mechanical effectors as well as sensory receptors in the organ of Corti (OC) of the inner ear. OHC in vitro and in organ explants exhibit mechanical responses to electrical, chemical or mechanical stimulation which may represent an aspect of their effector process that is expected in vivo. A detailed description, however, of an OHC effector operation in situ is still missing. Specifically, little is known as to how OHC movements influence the geometry of the OC in situ. Previous work has demonstrated that the motility of isolated OHCs in response to electrical stimulation and to K(+)-gluconate is probably under voltage control and causes depolarisation (shortening) and hyperpolarization (elongation). This work was undertaken to investigate if the movements that were observed in isolated OHC, and which are induced by ionic stimulation, could change the geometry of the OC. A synchronized depolarization of OHC was induced in guinea pig cochleae by exposing the entire OC to artificial endolymph (K+). Subsequent morphometry of mid-modiolar sections from these cochleae revealed that the distance between the basilar membrane (BM) and the reticular lamina (RL) had decreased considerably. Furthermore, in the three upper turns OHC had significantly shortened in all rows. The results suggest that OHC can change their length in the organ of Corti (OC) thus deforming the geometry of the OC. The experiments reveal a tonic force generation within the OC that may change the position of RL and/or BM, contribute to damping, modulate the BM-RL-distance and control the operating points of RL and sensory hair bundles. Thus, the results suggest active self-adjustments of cochlear mechanics by slow OHC length changes. Such mechanical adjustments have recently been postulated to correspond to timing elements of animal communication, speech or music.
人们普遍认为，耳蜗外毛细胞（OHC）在内耳柯蒂氏器（OC）中既作为机械效应器又作为感觉感受器发挥作用。体外和器官外植体中的OHC对电、化学或机械刺激表现出机械反应，这可能代表了其效应过程在体内预期的一个方面。然而，关于原位OHC效应器操作的详细描述仍然缺失。具体而言，关于OHC运动如何影响原位OC的几何形状，人们知之甚少。先前的研究表明，分离的OHC对电刺激和K(+) - 葡萄糖酸盐的运动性可能受电压控制，并导致去极化（缩短）和超极化（伸长）。本研究旨在调查在分离的OHC中观察到的、由离子刺激诱导的运动是否会改变OC的几何形状。通过将整个OC暴露于人工内淋巴（K+），在豚鼠耳蜗中诱导OHC的同步去极化。随后对这些耳蜗的中轴切片进行形态测量，结果显示基底膜（BM）和网状板（RL）之间的距离显著减小。此外，在三个上转中，所有排的OHC都明显缩短。结果表明，OHC可以在柯蒂氏器（OC）中改变其长度，从而使OC的几何形状变形。实验揭示了在OC内产生的张力，这可能会改变RL和/或BM的位置，有助于阻尼，调节BM - RL距离，并控制RL和感觉毛束的工作点。因此，结果表明通过OHC长度的缓慢变化对耳蜗力学进行主动自我调节。最近有人推测，这种机械调节与动物交流、语音或音乐的时间元素相对应。
