MECHANOELECTRICAL TRANSDUCTION IN ADULT OUTER HAIR CELLS

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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.