Viscoelastic relaxation in the membrane of the auditory outer hair cell

Abstract

The outer hair cell (OHC) in the mammalian ear has a unique membrane potential-dependent motility, which is considered to be important for frequency discrimination (tuning). The OHC motile mechanism is located at the cell membrane and is strongly influenced by its passive mechanical properties. To study the viscoelastic properties of OHCs, we exposed cells to a hypoosmotic solution for varying durations and then punctured them, to immediately release the osmotic stress. Using video records of the cells, we determined both the imposed strain and the strain after puncturing, when stress was reset to zero. The strain data were described by a simple rheological model consisting of two springs and a dashpot, and the fit to this model gave a time constant of 40 +/- 19 s for the relaxation (reduction) of tension during prolonged strain. For time scales much shorter or longer than this, we would expect essentially elastic behavior. This relaxation process affects the membrane tension of the cell, and because it has been shown that membrane tension has a modulatory role in the OHC's motility, this relaxation process could be part of an adaptation mechanism, with which the motility system of the OHC can adjust to changing conditions and maintain optimum membrane tension.

Actuation of flexoelectric membranes in viscoelastic fluids with applications to outer hair cells

“…Both the direct and converse membrane flexoelectric effects are sensor-actuator properties when membrane curvature and polarization are coupled as in nematic LCs. Membrane flexoelectricity due to its inherent sensoractuator capabilities is an area of current interest in soft matter materials [1,7,8,[14][15][16][17][18][19][20][21][22][23][24]. Over the years, much literature has dealt with the problem of measuring flexoelectric coefficients in various LCs [11,13].…”

Linear oscillatory dynamics of flexoelectric membranes embedded in viscoelastic media with applications to outer hair cells

“…The present model, indeed inspired by the OHC, shares similar properties as a physical membrane embedded in viscoelastic surroundings that also functions as a mechanical amplifier at characteristic (resonant) frequencies [40,[63][64][65][66][67][68][69]. In this context, the dimensional power dissipation is given by the following expression:…”

Regulation of the lateral wall stiffness by acetylcholine and GABA in the outer hair cells of the guinea pig

“…, 2003). The motor mechanisms work against the mechanical load of the lateral wall (Ehrenstein & Iwasa, 1996; Dallos et al. , 1997).…”

“…The lateral wall of the outer hair cells (OHCs), representing the efferent arm of the cochlear amplifier, plays an important role in the active shape changes of these cells (slow and fast motility) (Arima et al, 1991;Holley et al, 1992;Batta et al, 2003). The motor mechanisms work against the mechanical load of the lateral wall (Ehrenstein & Iwasa, 1996;Dallos et al, 1997). The membrane voltage-dependent electromotility is generally considered as the basis of the local force feedback process within the cochlear partition, called cochlear amplifier (Ashmore, 1987).…”