부산대학교 도서관

In this paper, the relation between the current and displacement responses due to an external mechanical stimulus on the outer hair cell (OHC) hair bundle (HB) is studied using a theoretical approach. We seek to understand the interplay between the time constants of the external loading and those intrinsic to the HB. To incorporate HB adaptation and channel gating, we used the model of an isolated HB, denoted as the TMJ model. We solved the nonlinear equations for the bundle dynamic response due to an externally applied force that consisted of an exponential temporal rise to a constant value. We determined the dependence of the bundle displacement over which the current continued to increase (the apparent operating range (OR)) on the rise time (τF) of the applied force. In addition, we developed a model linearized about the resting open probabilities for a given static, biasing load to provide closed-form approximations of the dependence on the stimulus rise time, τF, and bundle adaptation time constants. Finally, we wanted to determine if the inclusion of more precise kinematics of the tip link motion relative to the stereociliary rotation influenced model predictions of the channel opening and bundle stiffness. Hence, we developed geometrical relations between the two rows of stereocilia to establish coupled kinematic relations for inclusion in our HB kinetic model. We predict an OR of 30−50 nm for small τF and an overestimation by a factor of 10 in the OR for τF higher than the slow adaptation time constant. Finally, with accurate bundle kinematics, lower HB displacement, current, and adaptation motor displacement were predicted in contrast to the TMJ model. We are exploring the implications of this model on nanoscale mechano-electrical transduction. [ABSTRACT FROM AUTHOR]