Modeling Intracellular Ion Transport in the Outer Hair Cell

William Triffo, Rice University

The outer hair cell (OHC) of the mammalian cochlea changes length in response to variations in transmembrane potential. This phenomenon, known as electromotility, is responsible for the exquisite sensitivity and frequency discrimination evident in the mechanical response of the organ of Corti. Our understanding of peripheral auditory physiology and subsequent direction for treatment of deafness are therefore correlated to our comprehension of the physical basis of OHC operation. Due to the coupling between transmembrane potential and axial deformation in the OHC, interpretation of in vitro experimental results and understanding of in vivo OHC physiology depend on an accurate characterization of the development of the potential field over space and time. Because the charge carriers are ions in solution, correct depiction of the potential necessitates examination of intracellular ion transport. Previous studies of OHC electrophysiology have been limited to the one-dimensional (1D) case. We are currently implementing higher dimension finite element codes to apply conventional continuum theories of ion transport to the OHC involving the Nernst-Planck description of electrodiffusion. This implementation frees us from the restrictions of symmetry assumptions required of 1D approximations. We discuss our progress in the application of these codes and comment on the usage of tomographic methods to better define subcellular structure relevant to this problem in the OHC.

Abstract Author(s): William J. Triffo and Robert M. Raphael