Modeling of mechanical stimulation of hair cells in otolithic organs Original Research Article

Experimental investigations of the function of hair cell bundles (HCB) are based on artificial mechanical stimulation of the HCB by probes and fluid-jets. The purpose of the present work is to estimate the parameters of these stimulations and to analyze their correspondence to natural stimulation of the HCB in otoliths. This analysis is based on results of the previous modeling of transformations of mechanical input in the following series: acceleration of the otolithic membrane (OM), displacement of the OM gel layer, deflection of hair cell bundle, deformation of the ciliary tip-links, and formation of a temporal pattern of polarization [Kondrachuk, A.V. Models of the dynamics of the otolithic membrane and the hair cell bundle mechanics. J. Vest. Res. 11, 29–38, 2001; Kondrachuk, A.V. Models of otolithic membrane-hair cell bundle interaction. Hear. Res. 166, 96–112, 2002]. It is suggested that during natural stimulation, the contacts between the HCBs and the surrounding substance are spatially distributed over the body of the HCBs. The comparison of experimental and modeling data indicates that probe stimulation cannot imitate the effects of spatially distributed contacts. Stimulation of the HCB by fluid jet mimics the fluid-like gel interaction with the HCB, but application of the fluid jet is restricted by the low viscosity of the solution. The parameters of fluid jet stimulation indicate that inertial force, rather than viscous force, is responsible for the HCB deflection in these experiments. This could be verified by direct measurements of the parameters of fluid-jet stimulation. The present results show that the scarce and contradictory data about the nature and parameters of the substance that surrounds the surface of the HCBs of the otolithic organs is a great obstacle to understanding the function of the HCB.