The Endocochlear Potential Alters Cochlear Micromechanics

• Published in: Biophysical journal Vol. 100; no. 11; pp. 2586 - 2594
• Main Authors: Jacob, Stefan, Pienkowski, Martin, Fridberger, Anders
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 08.06.2011; Biophysical Society; The Biophysical Society
• Subjects: acoustics; Animals; Biological Systems and Multicellular Dynamics; Biomechanical Phenomena; Biophysics; Cell Movement; Cell Polarity; Cochlea - cytology; Cochlea - physiology; Ears & hearing; electrical properties; Electrophysiological Phenomena; Guinea Pigs; Hair Cells, Auditory, Outer - cytology; hearing; Hearing - physiology; image analysis; ion channels; Mechanical Phenomena; Mechanotransduction, Cellular; Medical imaging; Medicin och hälsovetenskap; Membrane Potentials; Membranes; Sound; Sound waves; Vibration
• ISSN: 0006-3495; 1542-0086; 1542-0086
• DOI: 10.1016/j.bpj.2011.05.002

Acoustic stimulation gates mechanically sensitive ion channels in cochlear sensory hair cells. Even in the absence of sound, a fraction of these channels remains open, forming a conductance between hair cells and the adjacent fluid space, scala media. Restoring the lost endogenous polarization of scala media in an in vitro preparation of the whole cochlea depolarizes the hair cell soma. Using both digital laser interferometry and time-resolved confocal imaging, we show that this causes a structural refinement within the organ of Corti that is dependent on the somatic electromotility of the outer hair cells (OHCs). Specifically, the inner part of the reticular lamina up to the second row of OHCs is pulled toward the basilar membrane, whereas the outer part (third row of OHCs and the Hensen's cells) unexpectedly moves in the opposite direction. A similar differentiated response pattern is observed for sound-evoked vibrations: restoration of the endogenous polarization decreases vibrations of the inner part of the reticular lamina and results in up to a 10-fold increase of vibrations of the outer part. We conclude that the endogenous polarization of scala media affects the function of the hearing organ by altering its geometry, mechanical and electrical properties.