Receptor potentials of lizard cochlear hair cells with free‐standing stereocilia in response to tones.

Holton, Thomas; Weiß, Thomas

doi:10.1113/jphysiol.1983.sp014975

Cited by 51 publications

(27 citation statements)

References 50 publications

(70 reference statements)

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“…It is against this background that responses to a sound stimulus may be played out. Although I A would not be active at most auditory frequencies as a result of a positive shift in the DC potential (Holton and Weiss, 1983), once efferents hyperpolarize the cell, the A-channel may act as a current shunt and alter the membrane time constant, thereby dampening or increasing the overall response, depending on its relative speeds of activation and deactivation. Modeling of K ϩ currents, such as I K , shows that they can act as high-pass filters (Hutcheon and Yarom, 2000).…”

Section: Discussionmentioning

confidence: 99%

Identification and Localization of an Arachidonic Acid-Sensitive Potassium Channel in the Cochlea

Sokolowski¹,

Sakai²,

Harvey³

et al. 2004

J. Neurosci.

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Receptor cells of the auditory and vestibular end organs of vertebrates acquire various types of potassium channels during development. Their expression and kinetics can differ along the tonotopic axis as well as in different cell types of the sensory epithelium. These variations can play a crucial role in modulating sensory transduction and cochlear tuning. Whole-cell tight-seal recordings of isolated hair cells revealed the presence of an arachidonic acid-sensitive A-type channel in the short (outer) hair cells of the chicken cochlea. This polyunsaturated fatty acid blocked the A-current, thereby increasing the amplitude and duration of the voltage response in these cells. We identified the gene encoding this channel as belonging to a member of the Shal subfamily, Kv4.2. Expression of the recombinant channel shows half-activation and inactivation potentials shifted to more positive values relative to native channels, suggesting that the native channel is coexpressed with an accessory subunit. RT-PCR revealed that transcription begins early in development, whereas in situ hybridization showed mRNA expression limited to the intermediate and short hair cells located in specific regions of the adult cochlea. Additional localization, using immunofluorescent staining, revealed clustering in apical-lateral regions of the receptor cell as well as in the cochlear ganglion. These experiments provide evidence that in addition to membrane proteins modulating excitation in these receptor cells, fatty acids contribute to the coding of auditory stimuli via these channels.

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Section: Discussionmentioning

confidence: 99%

Identification and Localization of an Arachidonic Acid-Sensitive Potassium Channel in the Cochlea

Sokolowski¹,

Sakai²,

Harvey³

et al. 2004

J. Neurosci.

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“…The resolution in level was I dB. The algorithm used to measure these iso-voltage contours (Holton & Weiss, 1983) was similar to the iso-AO contour algorithm. Unless otherwise noted, iso-AO contours presented in this paper have been 'smoothed' by a 3-point digital filter which replaced each data point, x, (except end points) by (x_1 + 2xn+ xn+i)/4.…”

Section: Methodsmentioning

confidence: 99%

“…Most of the techniques used in these two sets of experiments were similar, and technical details of animal surgery, acoustic stimulus generation and response recording are described elsewhere (Weiss, Mulroy, Turner & Pike, 1976;Holton, 1980;Baden-Kristensen & Weiss, 1983;Holton & Weiss, 1983). In brief, the basilar papilla of anaesthetized alligator lizards was exposed by opening and enlarging the round window.…”

Section: Methodsmentioning

confidence: 99%

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Frequency selectivity of hair cells and nerve fibres in the alligator lizard cochlea.

Holton¹,

Weiß²

1983

The Journal of Physiology

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SUMMARY1. Receptor potentials of hair cells and spike discharges of cochlear nerve fibres were recorded with micropipettes from the free-standing region of the basilar papilla of anaesthetized alligator lizards in response to tones. In this region the hair-cell stereocilia are free-standing, i.e. they protrude directly into endolymph and are not in contact with a tectorial membrane.2. The frequency selectivity of hair-cell responses was measured by means of isovoltage contours of the d.c. ( VJ) and fundamental-a.c. (V1) component of the receptor potential, i.e. iso-Vo and iso-V1 contours. The frequency selectivity of the nerve-fibre discharge was measured by iso-rate (iso-A0) contours. Iso-V0, iso-V1 and iso-A0 contours are basically V-shaped with a characteristic frequency (c.f.) defined as the frequency at which minimum sound pressure (Pmin) is required to evoke the criterion value of the response.3. Receptor potential iso-V0 contours and neural iso-A0 contours have similar slopes: the mean slopes of the low-frequency sides (dB/decade) are -43 0 and -44-3; the slopes of the high-frequency sides are 85-0 and 802. The band widths of iso-V0 and iso-A0 contours away from c.f. are similar (mean values of Q30dB are 040 and 053, respectively). The band widths of iso-A0 contours near c.f. are narrower than those of iso-V0 contours (mean values of QlodB are 2-34 and 1-20, respectively). However, the shapes of the contours near c.f. depend on the iso-response criteria, and we have not determined whether or not iso-V0 and iso-A0 contours are similar near c.f. The shapes of iso-V1 contours differ from those of iso-V0 and iso-A0 contours.4. Nerve fibre c.f.s are tonotopically organized in the nerve, with lowest c.f.s recorded from fibres innervating the border of free-standing and tectorial regions, a region in which hair-cell stereocilia are longest, and the highest c.f.s recorded from fibres innervating the end of the free-standing region in which hair-cell stereocilia are shortest. The c.f. of nerve-fibre response (and by implication hair-cell response) is, therefore, correlated with the height of the stereociliary tuft.

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“…Adaptation in the peripheral auditory system is likely localized to the cochlear hair cell afferent synapse because hair cell receptor potentials do not adapt to maintained acoustic stimulation (Russell and Sellick 1978;Holton and Weiss 1983). Synaptic vesicles in hair cells, like other sensory receptors and second-order neurons, are tethered at active zones to a specialized synaptic structure called a ''ribbon.''…”

Section: Introductionmentioning

confidence: 99%

Evidence That Rapid Vesicle Replenishment of the Synaptic Ribbon Mediates Recovery from Short-Term Adaptation at the Hair Cell Afferent Synapse

Spassova

Avissar

Furman

et al. 2004

JARO

104

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We have employed both in vitro patch clamp recordings of hair cell synaptic vesicle fusion and in vivo single unit recording of cochlear nerve activity to study, at the same synapse, the time course, control, and physiological significance of readily releasable pool dynamics. Exocytosis of the readily releasable pool was fast, saturating in less than 50 ms, and recovery was also rapid, regaining 95% of its initial amplitude following a 200-ms period of repolarization. Longer depolarizations (greater than 250 ms) yielded a second, slower kinetic component of exocytosis. Both the second component of exocytosis and recovery of the readily releasable pool were blocked by the slow calcium buffer, EGTA. Sound-evoked afferent synaptic activity adapted and recovered with similar time courses as readily releasable pool exhaustion and recovery. Comparison of readily releasable pool amplitude, capture distances of calcium buffers, and number of vesicles tethered to the synaptic ribbon suggested that readily releasable pool dynamics reflect the depletion of release-ready vesicles tethered to the synaptic ribbon and the reloading of the ribbon with vesicles from the cytoplasm. Thus, we submit that rapid recovery of the cochlear hair cell afferent fiber synapse from short-term adaptation depends on the timely replenishment of the synaptic ribbon with vesicles from a cytoplasmic pool. This apparent rapid reloading of the synaptic ribbon with vesicles underscores important functional differences between synaptic ribbons in the auditory and visual systems.

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Receptor potentials of lizard cochlear hair cells with free‐standing stereocilia in response to tones.

Cited by 51 publications

References 50 publications

Identification and Localization of an Arachidonic Acid-Sensitive Potassium Channel in the Cochlea

Identification and Localization of an Arachidonic Acid-Sensitive Potassium Channel in the Cochlea

Frequency selectivity of hair cells and nerve fibres in the alligator lizard cochlea.

Evidence That Rapid Vesicle Replenishment of the Synaptic Ribbon Mediates Recovery from Short-Term Adaptation at the Hair Cell Afferent Synapse

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