MECHANOELECTRICAL TRANSDUCTION IN ADULT OUTER HAIR CELLS

描述（由申请人提供）：外毛细胞（OHC）是Corti器官中的两种受体细胞之一，在哺乳动物听力中起着关键作用。OHC通过耳蜗内的局部机械反馈过程增强基底膜运动，称为“耳蜗放大器”，通常认为耳蜗放大的基础是OHC的电压依赖性体细胞长度变化。在该方案中，换能器电流响应于声刺激而产生的受体电位为细胞的运动活动提供输入。因此，OHC被认为执行两种转换器功能，静纤毛中的常规机电或正向转换和基底外侧膜中的专门机电或反向转换。尽管已经很好地研究了低等脊椎动物和哺乳动物前庭毛细胞中的机电转换，但成年耳蜗毛细胞中的正向转换过程基本上尚未探索。主要是因为技术上的困难。因此，目前还不清楚换能器电流有多大，以及电流是否也具有像低等脊椎动物毛细胞中所见的适应性。此外，还没有人尝试测量直接基底膜运动引起的换能器电流。本探索性/开发性研究的目标是在更类似于体内且相对完整的制备物（半耳蜗）中同时记录OHC换能器电流和基底膜运动。具体地，将测量作为基底膜运动的函数的换能器电流和膜电位。还将确定成人OHC的换能器电流是否具有适应性。将从25- 30日龄沙鼠中制备半食草动物。全细胞膜片钳技术将被用来记录传感器电流和膜电位从OHC在基底膜运动引起的振动玻璃纤维。用光电技术测量基底膜的运动。同时记录传感器电流和基底膜运动是研究外毛细胞转导过程的重要一步。由于大多数美国听力损失患者（总共约3000万人）都有某种毛细胞损伤，因此了解OHC的运作对于毛细胞相关听力损失和耳聋的生物补救和预防至关重要。

DESCRIPTION (provided by applicant): The outer hair cell (OHC) is one of two receptor cells in the organ of Corti, and plays a critical role in mammalian hearing. OHCs enhance basilar membrane motion through a local mechanical feedback process within the cochlea, termed the 'cochlear amplifier', it is generally believed that the basis of cochlear amplification is a voltage-dependent somatic length change of OHCs. In this scheme, receptor potentials produced by transducer current in response to acoustic stimulation provide the input to the cell's motor activity. Consequently, the OHC is thought to perform two transducer functions, a conventional mechanoelectrical or forward transduction in the stereocilia and a specialized electromechanical or reverse transduction in the basolateral membrane, Although the mechanoelectrical transduction in low-vertebrate and mammalian vestibular hair cells has been well studied, the forward transduction process in adult cochlear hair ceils has essentially not been explored, primarily because of technical difficulties. Therefore, it is still unclear how large the transducer current is and whether the current also has adaptation like that seen in low-vertebrate hair cells. Furthermore, no attempt has ever been made to measure transducer currents as a result of direct basilar membrane motion. The goal of this Exploratory/Developmental Research is to record OHC transducer current and basilar membrane motion simultaneously in a more in vivo-like and relatively intact preparation, the hemicochlea. Specifically, the transducer currents and membrane potentials as a function of basilar membrane motion wilt be measured. Whether the transducer current of adult OHCs has adaptation will also be determined. Hemicochlea will be prepared from 25- to 30-day-old gerbils. Whole cell patch-clamp techniques will be used to record transducer currents and membrane potentials from OHCs during basilar membrane motion evoked by a vibrating glass fiber. The motion of the basic membrane will be measured by optoelectronical technique. Simultaneous recording of the transducer current and basilar membrane motion is a significant step forward in studying the transduction process in OHCs. Because the majority of Americans with hearing loss, some 30 million in all, have some kind of hair cell damage, understanding the operation of OHCs is essential to the biological remediation and prevention of hair cell-related hearing loss and deafness.