By common consensus, outer hair cells (OHCs) are the key requisites of the mammalian cochlea's ability to process sound with high sensitivity and exquisite frequency resolution over a wide frequency range. OHC deficit, arising from environmental insults, disease or from the aging process, tends to be the initial cause of most sensorineural hearing loss. Such loss may affect as many as 20 million Americans. The existence of local mechanical feedback within the mammalian cochlea is now well accepted. In this scheme inner hair cells (IHC) are the true sensory receptors of the ear and, transmit auditory information to the central nervous system. In contrast, outer hair cells (OHC) are assumed not to have significant (auditory) receptor function but a major role as effector (motor) elements in a mechanical feedback loop which ultimately controls the input to IHCs. This feedback represents the cochlear amplification process. Shape changes (motility) of OHCs are assumed to be mechanism whereby energy is fed back to the vibrating cochlear partition. An array of experiments is proposed to assess and quantify various motile properties of isolated outer hair cells. Both electrically induced (electromotility) and ciliary displacement induced (mechanomotility) somatic shape change responses are studied. In addition, alterations in ciliary bundle responsiveness, related to membrane potential changes and somatic motile responses, are examined. Techniques developed in our Laboratory permit these measurements to he made in a simulated in vivo environment, at nanometer resolution, and over and exceeding the full audio bandwidth. The purpose of these studies is to elucidate the biophysics of cellular and ciliary motility as possible bases of the cochlear amplifier and to understand OHC function.

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Research Project (R01)
Project #
5R01DC000708-09
Application #
2683908
Study Section
Hearing Research Study Section (HAR)
Project Start
1990-04-01
Project End
2000-03-31
Budget Start
1998-04-01
Budget End
1999-03-31
Support Year
9
Fiscal Year
1998
Total Cost
Indirect Cost
Name
Northwestern University at Chicago
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
City
Evanston
State
IL
Country
United States
Zip Code
60201
Emadi, Gulam; Richter, Claus-Peter (2008) Developmental changes of mechanics measured in the gerbil cochlea. J Assoc Res Otolaryngol 9:22-32
He, David Z Z; Cheatham, Mary Ann; Pearce, Malini et al. (2004) Mouse outer hair cells lacking the alpha9 ACh receptor are motile. Brain Res Dev Brain Res 148:19-25
Emadi, Gulam; Richter, Claus-Peter; Dallos, Peter (2004) Stiffness of the gerbil basilar membrane: radial and longitudinal variations. J Neurophysiol 91:474-88
He, D Z; Zheng, J; Dallos, P (2001) Development of acetylcholine receptors in cultured outer hair cells. Hear Res 162:113-25
Keiler, S; Richter, C P (2001) Cochlear dimensions obtained in hemicochleae of four different strains of mice: CBA/CaJ, 129/CD1, 129/SvEv and C57BL/6J. Hear Res 162:91-104
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Sziklai, I; Szonyi, M; Dallos, P (2001) Phosphorylation mediates the influence of acetylcholine upon outer hair cell electromotility. Acta Otolaryngol 121:153-6
Dallos, P; He, D Z (2000) Two models of outer hair cell stiffness and motility. J Assoc Res Otolaryngol 1:283-91
He, D Z; Zheng, J; Edge, R et al. (2000) Isolation of cochlear inner hair cells. Hear Res 145:156-60
He, D Z; Dallos, P (2000) Properties of voltage-dependent somatic stiffness of cochlear outer hair cells. J Assoc Res Otolaryngol 1:64-81

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