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Perilymph Osmolality Modulates Cochlear Function

Authors

  • Chul-Hee Choi PhD,

    1. From the The Bobby R. Alford Department of Otolaryngology–Head and Neck Surgery Houston, Texas, U.S.A.
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  • John S. Oghalai MD

    Corresponding author
    1. From the The Bobby R. Alford Department of Otolaryngology–Head and Neck Surgery Houston, Texas, U.S.A.
    2. Department of Neuroscience, Baylor College of Medicine Houston, Texas, U.S.A.
    3. Department of Bioengineering, Rice University, Houston, Texas, U.S.A.
    • Send correspondence to John S. Oghalai, MD, The Bobby R. Alford Department of Otolaryngology–Head and Neck Surgery, One Baylor Plaza, NA102, Baylor College of Medicine, Houston, TX 77030
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  • Editor's Note: This Manuscript was accepted for publication April 2, 2008. Dr. Choi's current affiliation: Hough Ear Institute, Oklahoma City, Oklahoma, U.S.A. and Free Radical Biology and Aging Program, Oklahoma Medical Research Foundation, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, U.S.A.

Abstract

Objectives/Hypothesis: The cochlear amplifier is required for the exquisite sensitivity of mammalian hearing. Outer hair cells underlie the cochlear amplifier and they are unique in that they maintain an intracellular turgor pressure. Changing the turgor pressure of an isolated outer hair cells through osmotic challenge modulates its ability to produce electromotile force. We sought to determine the effect of osmotic challenge on cochlear function.

Study Design: In vivo animal study.

Methods: Hypotonic and hypertonic artificial perilymph was perfused through the scala tympani of anesthetized guinea pigs. Cochlear function was assessed by measuring the compound action potential, distortion product otoacoustic emissions, the cochlear microphonic, and the endocochlear potential.

Results: Hypotonic perilymph decreased and hypertonic perilymph increased compound action potential and distortion product otoacoustic emission thresholds in a dose-dependent and reversible manner. The cochlear microphonic quadratic distortion product magnitude increased after hypotonic perfusion and decreased with hypertonic perfusion. There were no changes in the stimulus intensity growth curve of the low-frequency cochlear microphonic. The endocochlear potential was not affected by perilymph osmolality.

Conclusions: These data demonstrate that perilymph osmolality can modulate cochlear function and are consistent with what would be expected if outer hair cells turgor pressure changes the gain of the cochlear amplifier in vivo.

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