A dynamic model of outer hair cell motility including intracellular and extracellular fluid viscosity

The deformation response of a guinea pig outer hair cell is modeled for mechanical and electrical stimulation up to 25 kHz. The analysis uses a Fourier series technique for a finite length cell surrounded internally and externally by a much larger continuum of viscous fluid. The analytical solution predicts that outer hair cell length changes occur due to applied mechanical or electrical stimulation without significant resonance, characteristic of a highly damped system. The deformation is found to have little attenuation up to a corner frequency of about 2 kHz for long cells and 10 kHz for short cells, in agreement with published experimental results. For electrical loading of 1 mV across the lateral cell wall, deformation for short cells is calculated to be greater than 1 nm for frequencies up to 20 kHz. These results support the proposition that in vivo the outer hair cell modifies the character of basilar membrane deformation on a cycle-by-cycle basis. An estimate of the capability of the cell to supply energy to the basilar membrane is given based on published values of outer hair cell material properties.