Kinetic Membrane Model of Outer Hair Cells

The effectiveness of outer hair cells (OHCs) in amplifying the motion of the organ of Corti, and thereby contributing to the sensitivity of mammalian hearing, depends on the mechanical power output of these cells. Electromechanical coupling in OHCs, which enables these cells to convert electrical energy into mechanical energy, has been analyzed in detail using isolated cells using primarily static membrane models. In the preceding reports, mechanical output of OHC was evaluated by developing a kinetic theory based on a simplified onedimensional (1D) model for OHCs. Here such a kinetic description of OHCs is extended by using the membrane model, which has been used for analyzing in vitro experiments. The present theory predicts, for systems without inertial load, that elastic load enhances positive shift of voltage dependence of the membrane capacitance due to turgor pressure. For systems with inertia, mechanical power output also depends on turgor pressure. The maximal power output is, however, similar to the previous prediction of up to ∼10 fW based on the 1D model. Statement of Significance This paper is an attempt for developing a physical model to clarify the mechanism of outer hair cells in performing their role as an amplifier in mammalian hearing. Specifically, this paper extends a static model of these cells into a dynamic one to evaluate mechanical power production, which is essential for the function of these cells. It clarifies the assumptions essential for a previous phenomenological theory, a 1-D model. In addition, it describes the effect of turgor pressure on mechanical power generation.