Stretch sensitivity of the lateral wall of the auditory outer hair cell from the guinea pig

Multiscale asymptotic methods developed previously to study macromechanical wave propagation in cochlear models are generalized here to include active control of a cochlear partition having three subpartitions, the basilar membrane, the reticular lamina, and the tectorial membrane. Activation of outer hair cells by stereocilia displacement and/or by lateral wall stretching result in a frequencydependent force acting between the reticular lamina and basilar membrane. Wavelength-dependent fluid loads are estimated by using the unsteady Stokes' equations, except in the narrow gap between the tectorial membrane and reticular lamina, where lubrication theory is appropriate. The local wavenumber and subpartition amplitude ratios are determined from the zeroth order equations of motion. A solvability relation for the first order equations of motion determines the subpartition amplitudes. The main findings are as follows: The reticular lamina and tectorial membrane move in unison with essentially no squeezing of the gap; an active force level consistent with measurements on isolated outer hair cells can provide a 35-dB amplification and sharpening of subpartition waveforms by delaying dissipation and allowing a greater structural resonance to occur before the wave is cut off; however, previously postulated activity mechanisms for single partition models cannot achieve sharp enough tuning in subpartitioned models.The cochlea consists of a liquid-filled spiral helix channel embedded in the temporal bone. Cross-sections along its axis are divided into two main chambers, the scalae, by a cochlear partition (CP) composed of two parallel fibrous membranes, the basilar membrane (BM) and tectorial membrane (TM) with a complex cell structure between them. A thin gap separates the reticular lamina (RL), which is the upper surface of the cell complex, from the TM (Fig. 1). Both efferent and afferent nerve fibers are attached to the synaptic ends of two particular cell groups, the inner and outer hair cells (IHC and OHC, respectively). These cells derive their names from the bundles of hair-like projections called stereocilia. The stereocilia lie in the thin liquid-filled gap between the RL and TM with the tips of the OHC stereocilia embedded in the TM. Their displacement, caused by the CP motion, modulates both transmembrane and receptor potentials of both cell types. This property allows afferent neurons from the IHCs to carry neural discharges of encoded acoustic signals to the auditory cortex, while the efferent neurons to the OHCs evidently regulate their motility properties. The axial variations of the CP are known to effect spatial frequency filtering of the acoustic wave. Frequency discrimination is directly related to the sharpness of these spatial filters. Impressive frequency response quality factors (Q 10) have been measured for both neural discharges and CP mechanical oscillations. As this sharpness cannot be solely attributed to passive mechanicalThe publication costs of this article were defrayed in part by p...

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“…OHC (23). Here a, 03, and -y are electromechanical parameters depending on the OHC active properties and cross-sectional geometry.…”

Section: Mathematical Formulation and Solutionmentioning

confidence: 99%

Active control of waves in a cochlear model with subpartitions.

Chadwick

Dimitriadis

Iwasa

1996

Proc. Natl. Acad. Sci. U.S.A.

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“…Struc tural coupling of the cortical lattice to the plasma mem brane by the framework of micropillar structures could convey axial forces applied to the cell body to the lateral plasma membrane. Differences in stretch sensitivity of the OHC lateral wall have recently been described [5].…”

Section: Introductionmentioning

confidence: 99%

Cytoskeletal Basis for Contractility of Outer Hair Cells in the Normal Adult Human Organ of Corti: Comparisons with Vestibular Hair Cells

Anniko

Arnold²,

Stigbrand³

et al. 1995

ORL

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The present study is the first consecutive analysis of the adult normal human organ of Corti and vestibular hair cells with regard to the expression of F-actin, actin-associated proteins (alpha-actinin, alpha- and beta-spectrins, vinculin and tropomyosin), beta-tubulin and the calcium-binding protein synaptophysin. The expression of these cytoskeletal and their associated proteins in man is largely similar to, although not identical with, that previously described for several other mammalian species. However, a few very unusual staining patterns were found. In several long outer hair cells a rod of F-actin extended from the infracuticular area to the cell nucleus. Fluorescence for tropomyosin occurred both in the cuticular plates of the outer and inner hair cells, and in the area of close apposition between the base of the outer hair cell and the apical part of Deiter’s cell. In contrast, the vestibular hair cells showed immunoreactivity for tropomyosin only in the cuticular plates.

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“…Earlier studies 8,16 have reported mechanosensitive channels in the lateral wall of the outer hair cell. However, the parameters of the channels in the lateral wall have to be further investigated since the force sensitivity and density of the channels were several times lower than those in other mechanosensitive cellular membranes.…”

Section: Parameters Of the Channelsmentioning

confidence: 98%

“…By using Eqs. (11)(12)(13)(14)(15)(16)(17), we derive the following version of the balance of current in the cell…”

Section: Derivation Of the Receptor Potentialmentioning

confidence: 99%

“…33 Third, mechanosensitive channels, although with a relatively low response to the mechanical perturbation of the membrane, have been reported in the lateral wall of the cell. 8,16 Also, a mechanosensitive poration responsible for water permeability changes in the cell wall has been found. 24 In the present paper, we focus on the effect of the mechanosensitive channels in the lateral wall, but two other types of ion channels, the transducer channels and voltage-gated channels, are also included in our analysis.…”

Section: Introductionmentioning

confidence: 98%

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Mechanosensitive Channels in the Lateral Wall Can Enhance the Cochlear Outer Hair Cell Frequency Response

et al. 2005

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We present the results of a modeling study on the impact of mechanosensitive channels in the lateral wall of the outer hair cell on the cell frequency response. The model includes the electrical properties of the cell membrane, piezoelectricity associated with a membrane motor mechanism, and mechanosensitive channels in the cell lateral wall. The outer hair cell is loaded by the vibrating basilar and tectorial membranes, and this loading generates strain in the lateral wall. Our analysis reveals a property, the strain rate sensitivity, that, in concert with the piezoelectric effect, can enhance the cell frequency response. We discuss possible viscoelastic-type mechanisms of the channel's strain rate sensitivity that is consistent with the organization of the composite cell lateral wall. The parameters of our model are chosen on the basis of the previously estimated electrical and piezoelectric properties as well as typical conductance and density of the mechanosensitive channels in cells. We found that the strain rate sensitivity of the channels can result in receptor potentials greater than those predicted by the RC (resistance and capacitance) analysis. The effect of the channels is especially significant in an intermediate range of sound frequencies, and the channel-related gain is up to 3-4 times between 3 and 15 kHz.

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Stretch sensitivity of the lateral wall of the auditory outer hair cell from the guinea pig

Cited by 54 publications

References 11 publications

Active control of waves in a cochlear model with subpartitions.

Active control of waves in a cochlear model with subpartitions.

Cytoskeletal Basis for Contractility of Outer Hair Cells in the Normal Adult Human Organ of Corti: Comparisons with Vestibular Hair Cells

Mechanosensitive Channels in the Lateral Wall Can Enhance the Cochlear Outer Hair Cell Frequency Response

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