Comparison of isolated outer hair cells from five mammalian species

Zajic, Gary; Schacht, Jochen

doi:10.1016/0378-5955(87)90061-x

Cited by 99 publications

(51 citation statements)

References 18 publications

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“…In order to differentiate basal and apical outer hair cells, the 2 first turns (from the base of the cochlea) and the 2 apical turns of the organ of Corti were collected and sampled separately. These were kept at room temperature (20-22°C) in Hank's Balanced Salt Solution (HBSS: 137 rnM-NaCl, 5.4 mM KCl, 1.25 mM CaCl,, 0.5 mM MgCl,, 0.4 mM MgSO,, 0.33 mM Na,HPO,, 0.44 mM KH,PO,, 5.5 mM D-glucose; Gibco Laboratories, Grand Island, NY) buffered to pH 7.4 with 5 mM sodium HEPES (Dulon et al, 1987;Zajic and Schacht, 1987). After a lo-min incubation with 0.5 mg collagenase (type IV, Sigma, St, Louis, MO) per ml HBSS.…”

Section: Methodsmentioning

confidence: 99%

Increasing intracellular free calcium induces circumferential contractions in isolated cochlear outer hair cells

1990

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The relationship between intracellular free calcium and the motile responses of outer hair cells isolated from the guinea pig cochlea was examined. Calcium levels were modulated by the addition of the calcium ionophores ionomycin or A23187 to the incubation medium and monitored with the fluorescent calcium indicator fluo-3. In the presence of 1.25 mM external calcium, the application of either ionophore (10 microM) led to an increase in intracellular free calcium from 157 +/- 76 nM to 1200 +/- 500 nM within 30–60 sec. Concurrently, cells elongated by 1–2 microns, cell diameter decreased, and cell volume shrank by 269 +/- 220 microns 3 (5.0 +/- 4.1%). The reduction in diameter was most pronounced in the middle portion of the cell (4.4% +/- 4.2%), also evident in the apical region (3.1% +/- 4.8%) but not significant in the basal region near the nucleus. This response was observed in outer hair cells from basal and apical turns of the cochlea and was reversed when the cells were rinsed with calcium-free medium supplemented with 2 mM EGTA. Optical imaging of the cell membrane with the potentiometric dye 1-(3- sulfonatopropyl)-4-[beta] [2-(di-n-butylaminol)-6-naphthyl vinyl] pyridinium betaine during the elevation of intracellular calcium demonstrated features of contractility at the lateral cell membrane. A rise in intracellular calcium as well as the motile response was still observed after a 5-min exposure of the cells to a calcium-free solution (supplemented with 2 mM EGTA), indicating that the ionophore was also able to liberate calcium from intracellular sites. However, depletion of calcium stores through prolonged incubation of the cells in calcium- free medium (30–60 min) suppressed both the calcium signal and the cell response. The calmodulin inhibitors trifluoperazine and pimozide (30 microM) blocked the cell motility induced by ionomycin while they left the increase of intracellular calcium unaffected. These observations suggest that calcium-dependent circumferential contractions in outer hair cells are mediated by calmodulin. The application to the extracellular medium of putative neurotransmitters of the cochlear efferent system such as acetylcholine and GABA led to neither an increase in intracellular calcium nor a modification of cell shape. Therefore, these neurotransmitters may not be directly involved in calcium-induced contractions in outer hair cells. The circumferential contractions altered the stiffness of the plasma membrane and the turgor of the cell. Under normal conditions, changes in cell volume were inversely proportional to the osmotic pressure of the extracellular medium following van't Hoff's law.(ABSTRACT TRUNCATED AT 400 WORDS)

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Section: Methodsmentioning

confidence: 99%

Increasing intracellular free calcium induces circumferential contractions in isolated cochlear outer hair cells

1990

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“…The coils were gently transferred with a 70 Al volume of MEM to a perfusion chamber. This procedure usually yielded a large number of healthy isolated outer hair cells (Zajic and Schacht, 1987). The outer hair cells retained their normal morphology for an average time of 4 h. Stable currents could be usually recorded from such outer hair cells for more than 1 h when perfused with control solutions, drug-containing solutions, followed by control solutions for washout.…”

Section: Methodsmentioning

confidence: 99%

Inhibition of K+ currents of outer hair cells in guinea pig cochlea by fluoxetine

Bian

Yeh

Aistrup

et al. 2002

European Journal of Pharmacology

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The effects of fluoxetine (ProzacR), a widely used antidepressant drug, on K + channel in outer hair cells isolated from guinea pig cochlea were studied using the whole-cell patch clamp technique. Fluoxetine potently inhibited leak K + currents with an IC 50 of 0.78 AM. The inhibition was reversible and voltage-independent. At 45-to 103-fold higher concentrations than the plasma levels, fluoxetine reversibly blocked voltage-activated K + currents. Kinetics of the current in the presence of fluoxetine resembled the control current, and the inhibition was not use-dependent. Neither the activation curve nor the reversal potential was affected by fluoxetine. This inhibition was voltagedependent with an electric distance (d value) of the binding site of at least 26% of the membrane field from the cytoplasmic side. Useindependent inhibition suggests that fluoxetine blocks the channel before its opening or instantly blocks the open channel. This is the first study of the action of this compound on K + channel of outer hair cells of the mammalian inner ear. We conclude that the block of the leak K + currents can occur at therapeutic levels of fluoxetine. Since the voltage-activated K + currents are not potently blocked by fluoxetine, this action might not be related to its antidepressant action or adverse effects. D

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“…Mammalian OHCs are slender cylindrical structures with fairly uniform diameters (8-10 mm), and with lengths ranging from 20-30 mm in the high-frequency cochlear base to approximately about 80-100 mm in the lowfrequency apex (Dallos et al, 1991). Zajic and Schacht (1987) isolated OHCs from guinea pigs, chinchillas, rats, mice, and gerbils. They found that the morphological features of these OHCs were similar and that the cells were cylindrical.…”

Section: Discussionmentioning

confidence: 99%

Specialized features of the outer hair cell shapes in the cochlear fovea of bats

Zhu

et al. 2015

Genet. Mol. Res.

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ABSTRACT. In this study, we examined the specialized features of the outer hair cells (OHCs) and the stereocilium bundles of the bat cochlear fovea. Bat cochlea hair cells were observed by scanning and transmission electron microscopy, and the auditory brainstem response thresholds were assessed. The stereocilia bundles of the OHCs were extremely short. The OHC bodies were flask-shaped and cambiform or ball-shape in the cochlear fovea. Digitations in the Deiters cells had exaggerated lengths, and cup formation of the Deiters cell, housed at the bottom of the OHC in the base of the cell, showed a specialized shape. Our results provide the first evidence that different shapes of the OHCs in the cochlea fovea are related to the high-frequency function of auditory response. Echolocating bats have cochlear morphologies that differ from those of non-echolocating animals. Bat cochlear foveae are specialized for analyzing the Doppler-shifted echoes of the first-harmonics of the CF 2 component; these are overrepresented in the frequency range around the dominant harmonic of the echolocation calls of bats. However, the OHCs of the bat cochlear fovea have not been fully characterized. 9530-9542 (2015)

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Comparison of isolated outer hair cells from five mammalian species

Cited by 99 publications

References 18 publications

Increasing intracellular free calcium induces circumferential contractions in isolated cochlear outer hair cells

Increasing intracellular free calcium induces circumferential contractions in isolated cochlear outer hair cells

Inhibition of K+ currents of outer hair cells in guinea pig cochlea by fluoxetine

Specialized features of the outer hair cell shapes in the cochlear fovea of bats

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