Fridberger Anders, de Monvel Jacques Boutet, Zheng Jiefu, Hu Ning, Zou Yuan, Ren Tianying, Nuttall Alfred
Center for Hearing and Communication Research, Department of Clinical Neuroscience, Karolinska Institutet, SE-171 76 Stockholm, Sweden.
J Neurosci. 2004 Nov 10;24(45):10057-63. doi: 10.1523/JNEUROSCI.2711-04.2004.
During sound stimulation, receptor potentials are generated within the sensory hair cells of the cochlea. Prevailing theory states that outer hair cells use the potential-sensitive motor protein prestin to convert receptor potentials into fast alterations of cellular length or stiffness that boost hearing sensitivity almost 1000-fold. However, receptor potentials are attenuated by the filter formed by the capacitance and resistance of the membrane of the cell. This attenuation would limit cellular motility at high stimulus frequencies, rendering the above scheme ineffective. Therefore, Dallos and Evans (1995a) proposed that extracellular potential changes within the organ of Corti could drive cellular motor proteins. These extracellular potentials are not filtered by the membrane. To test this theory, both electric potentials inside the organ of Corti and basilar membrane vibration were measured in response to acoustic stimulation. Vibrations were measured at sites very close to those interrogated by the recording electrode using laser interferometry. Close comparison of the measured electrical and mechanical tuning curves and time waveforms and their phase relationships revealed that those extracellular potentials indeed could drive outer hair cell motors. However, to achieve the sharp frequency tuning that characterizes the basilar membrane, additional mechanical processing must occur inside the organ of Corti.
在声音刺激期间，耳蜗的感觉毛细胞内会产生感受器电位。流行的理论认为，外毛细胞利用电位敏感的马达蛋白——prestin，将感受器电位转化为细胞长度或硬度的快速变化，从而使听力灵敏度提高近1000倍。然而，感受器电位会被细胞的膜电容和电阻形成的滤波器衰减。这种衰减会限制高刺激频率下的细胞运动性，使上述机制失效。因此，达洛斯和埃文斯（1995a）提出，柯蒂氏器内的细胞外电位变化可能驱动细胞马达蛋白。这些细胞外电位不会被细胞膜过滤。为了验证这一理论，研究人员测量了柯蒂氏器内部的电位以及基底膜在声刺激下的振动情况。使用激光干涉测量法在非常靠近记录电极所检测位置的地方测量振动。对测得的电调谐曲线和机械调谐曲线、时间波形及其相位关系进行仔细比较后发现，那些细胞外电位确实能够驱动外毛细胞马达。然而，为了实现表征基底膜的尖锐频率调谐，柯蒂氏器内部必须进行额外的机械处理。
