Ionic currents and current-clamp depolarisations of type I and type II hair cells from the developing rat utricle

1. Type I vestibular hair cells were isolated from the cristae ampullares of the semicircular canals of the Mongolian gerbil (Meriones unguiculatus) and the white king pigeon (Columba livia). Dissociated type I cells were distinguished from type II hair cells by their neck to plate ratio (NPR) and their characteristic amphora shape. 2. The membrane properties of gerbil and pigeon type I hair cells were studied in whole-cell voltage- and current-clamp using the perforated patch technique with amphotericin B as the perforating agent. 3. In whole-cell current-clamp, the average zero-current potential, Vz, measured for pigeon type I hair cells, was -70 +/- 7 (SD) mV (n = 18) and -71 +/- 11 mV (n = 83) for gerbil type I hair cells. 4. At Vz, for both gerbil and pigeon type I hair cells, a potassium current (IKI) was > or = 50% activated. This current deactivated rapidly when the membrane potential was hyperpolarized below -90 mV. 5. IKI was blocked by externally applied 4-aminopyridine (4-AP) (5 mM) and by internally applied 20 mM tetraethylammonium (TEA). It was also reduced when 4 mM barium was present in the external solution. The degree of block by barium increased as the membrane potential became more positive. External cesium (5 mM) blocked the inward component of IKI. When IKI was pharmacologically blocked, Vz depolarized by approximately 40 mV. Therefore IKI appears to be a delayed rectifier and to set the more negative Vz noted for isolated type I hair cells when compared to isolated type II hair cells, which do not have IKI. 6. A second, smaller potassium current was present at membrane potential depolarizations above -40 mV. This current was blocked by 30-50 mM, externally applied TEA, 100 microM quinidine, 100 nM apamin, but not 100 nM charybdotoxin, indicating that this is a calcium-activated potassium current, IK(Ca), different from the maxi-K calcium-activated potassium current found in most other hair cells.

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A delayed rectifier conductance in type I hair cells of the mouse utricle

Journal of Neurophysiology ◽

10.1152/jn.1996.76.2.995 ◽

1996 ◽

Vol 76 (2) ◽

pp. 995-1004 ◽

Cited By ~ 90

Author(s):

A. Rusch ◽

R. A. Eatock

Keyword(s):

Hair Cells ◽

Time Course ◽

Dissociation Constants ◽

Resting Potential ◽

Delayed Rectifier ◽

Type I ◽

Type Ii ◽

Voltage Range ◽

Average Maximum

1. Membrane currents of hair cells in acutely excised or cultured mouse utricles were recorded with the whole cell voltage-clamp method at temperatures between 23 and 36 degrees C. 2. Type I and II hair cells both had delayed rectifier conductances that activated positive to -55 mV. 3. Type I, but not type II, hair cells had an additional delayed rectifier conductance (gK,L) with an activation range that was unusually negative and variable. At 23-25 degrees C, V(1/2) values ranged from -88 to -62 mV in 57 cells. 4. gK,L was very large. At 23-25 degrees C, the average maximum chord conductance was 75 +/- 65 nS (mean +/- SD, n = 57; measured at -54 mV), or approximately 21 nS/pF of cell capacitance. 5. gK,L was highly selective for K+ over Na+ (permeability ratio PNa+/PK+:0.006), but unlike other delayed rectifiers, gK,L was significantly permeable to Cs+ (PCs+/PK+:0.31). gK,L was independent of extracellular Ca2+. 6. At -64 mV, Ba2+ and 4-aminopyridine blocked gK,L with apparent dissociation constants of 2.0 mM and 43 microM, respectively. Extracellular Cs+ (5 mM) blocked gK,L by 50% at -124 mV. Apamin (100 nM) and dendrotoxin (10 nM) has no effect. 7. The kinetic data of gK,L are consistent with a sequential gating model with at least two closed states and one open state. The slow activation kinetics (principal time constants at 23-25 degrees C:600-200 ms) had a thermal Q10 of 2.1. Inactivation (Q10:2.7) was partial at all temperatures. Deactivation followed a double-exponential time course and had a Q10 of 2.0. 8. At 23-25 degrees C, gK,L was appreciably activated at the mean resting potential of type I hair cells (-77 +/- 3.1 mV, n = 62), so that input conductances were often more than an order of magnitude larger than those of type II cells. If these conditions hold in vivo, type I cells would produce unusually small receptor potentials. Warming the cells to 36 degrees C produced parallel shifts in gK,L's activation range (0.8 +/- 0.3 mV/degrees C, n = 8), and in the resting potential (0.6 +/- 0.3 mV/degrees C, n = 4). Thus the high input conductances were not an artifact of unphysiological temperatures but remained high near body temperature. It remains possible that in vivo gK,L's activation range is less negative and input conductances are lower; the large variance in the voltage range of activation suggests that it may be subject to modulation.

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Ionic Currents and Electromotility in Inner Ear Hair Cells From Humans

Journal of Neurophysiology ◽

10.1152/jn.1998.79.4.2235 ◽

1998 ◽

Vol 79 (4) ◽

pp. 2235-2239 ◽

Cited By ~ 22

Author(s):

John S. Oghalai ◽

Jeffrey R. Holt ◽

Takashi Nakagawa ◽

Thomas M. Jung ◽

Newton J. Coker ◽

...

Keyword(s):

Inner Ear ◽

Hair Cells ◽

Ionic Currents ◽

Sensory Epithelium ◽

Outer Hair Cells ◽

Sensory Receptor ◽

Surgical Removal ◽

Type I ◽

Vestibular Hair Cells ◽

Sensory Receptor Cells

Oghalai, John S., Jeffrey R. Holt, Takashi Nakagawa, Thomas M. Jung, Newton J. Coker, Herman A. Jenkins, Ruth Anne Eatock, and William E. Brownell. Ionic currents and electromotility in inner ear hair cells from humans. J. Neurophysiol. 79: 2235–2239, 1998. The upright posture and rich vocalizations of primates place demands on their senses of balance and hearing that differ from those of other animals. There is a wealth of behavioral, psychophysical, and CNS measures characterizing these senses in primates, but no prior recordings from their inner ear sensory receptor cells. We harvested human hair cells from patients undergoing surgical removal of life-threatening brain stem tumors and measured their ionic currents and electromotile responses. The hair cells were either isolated or left in situ in their sensory epithelium and investigated using the tight-seal, whole cell technique. We recorded from both type I and type II vestibular hair cells under voltage clamp and found four voltage-dependent currents, each of which has been reported in hair cells of other animals. Cochlear outer hair cells demonstrated electromotility in response to voltage steps like that seen in rodent animal models. Our results reveal many qualitative similarities to hair cells obtained from other animals and justify continued investigations to explore quantitative differences that may be associated with normal or pathological human sensation.

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Molecular characterization of an inward rectifier channel (IKir) found in avian vestibular hair cells: cloning and expression of pKir2.1

Physiological Genomics ◽

10.1152/physiolgenomics.00096.2004 ◽

2004 ◽

Vol 19 (2) ◽

pp. 155-169 ◽

Cited By ~ 11

Author(s):

Manning J. Correia ◽

Thomas G. Wood ◽

Deborah Prusak ◽

Tianxiang Weng ◽

Katherine J. Rennie ◽

...

Keyword(s):

Hair Cells ◽

Cho Cells ◽

Dwell Time ◽

Single Channel ◽

Cloning And Expression ◽

Single Type ◽

Type I ◽

Type Ii ◽

Vestibular Hair Cells ◽

Inwardly Rectifying

A fast inwardly rectifying current has been observed in some of the sensory cells (hair cells) of the inner ear of several species. While the current was presumed to be an IKir current, contradictory evidence existed as to whether the cloned channel actually belonged to the Kir2.0 subfamily of potassium inward rectifiers. In this paper, we report for the first time converging evidence from electrophysiological, biochemical, immunohistochemical, and genetic studies that show that the Kir2.1 channel carries the fast inwardly rectifying currents found in pigeon vestibular hair cells. Following cytoplasm extraction from single type II and multiple pigeon vestibular hair cells, mRNA was reverse transcribed, amplified, and sequenced. The open reading frame (ORF), consisting of a 1,284-bp nucleotide sequence, showed 94, 85, and 83% identity with Kir2.1 subunit sequences from chick lens, Kir2 sequences from human heart, and a mouse macrophage cell line, respectively. Phylogenetic analyses revealed that pKir2.1 formed an immediate node with hKir2.1 but not with hKir2.2–2.4. Hair cells (type I and type II) and supporting cells in the sensory epithelium reacted positively with a Kir2.1 antibody. The whole cell current recorded in oocytes and CHO cells, transfected with pigeon hair cell Kir2.1 (pKir2.1), demonstrated blockage by Ba2+ and sensitivity to changing K+ concentration. The mean single-channel linear slope conductance in transfected CHO cells was 29 pS. The open dwell time was long (∼300 ms at −100 mV), and the closed dwell time was short (∼34 ms at −100 mV). Multistates ranging from 3–6 were noted in some single-channel responses. All of the above features have been described for other Kir2.1 channels. Current clamp studies of native pigeon vestibular hair cells illustrated possible physiological roles of the channel and showed that blockage of the channel by Ba2+ depolarized the resting membrane potential by ∼30 mV. Negative currents hyperpolarized the membrane ∼20 mV before block but ∼60 mV following block. RT-PCR studies revealed that the pKir2.1 channels found in pigeon vestibular hair cells were also present in pigeon vestibular nerve, vestibular ganglion, lens, neck muscle, brain (brain stem, cerebellum and optic tectum), liver, and heart.

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Axodendritic versus axosomatic cochlear efferent termination is determined by afferent type in a hierarchical logic of circuit formation

Science Advances ◽

10.1126/sciadv.abd8637 ◽

2021 ◽

Vol 7 (4) ◽

pp. eabd8637

Author(s):

Jemma L. Webber ◽

John C. Clancy ◽

Yingjie Zhou ◽

Natalia Yraola ◽

Kazuaki Homma ◽

...

Keyword(s):

Hair Cells ◽

Fiber Type ◽

Afferent Fiber ◽

Outer Hair Cells ◽

Type I ◽

Type Ii ◽

Efferent Neurons ◽

Distinct Pair ◽

Mechanosensory Hair Cells ◽

Circuit Formation

Hearing involves a stereotyped neural network communicating cochlea and brain. How this sensorineural circuit assembles is largely unknown. The cochlea houses two types of mechanosensory hair cells differing in function (sound transmission versus amplification) and location (inner versus outer compartments). Inner (IHCs) and outer hair cells (OHCs) are each innervated by a distinct pair of afferent and efferent neurons: IHCs are contacted by type I afferents receiving axodendritic efferent contacts; OHCs are contacted by type II afferents and axosomatically terminating efferents. Using an Insm1 mouse mutant with IHCs in the position of OHCs, we discover a hierarchical sequence of instructions in which first IHCs attract, and OHCs repel, type I afferents; second, type II afferents innervate hair cells not contacted by type I afferents; and last, afferent fiber type determines if and how efferents innervate, whether axodendritically on the afferent, axosomatically on the hair cell, or not at all.

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Quantal and Nonquantal Transmission in Calyx-Bearing Fibers of the Turtle Posterior Crista

Journal of Neurophysiology ◽

10.1152/jn.00332.2007 ◽

2007 ◽

Vol 98 (3) ◽

pp. 1083-1101 ◽

Cited By ~ 40

Author(s):

Joseph C. Holt ◽

Shilpa Chatlani ◽

Anna Lysakowski ◽

Jay M. Goldberg

Keyword(s):

Ampa Receptor ◽

Hair Cells ◽

Ultrastructural Study ◽

Nerve Fibers ◽

Type I ◽

Outer Face ◽

Type Ii ◽

Intracellular Recordings ◽

External Concentration ◽

Voltage Gated

Intracellular recordings were made from nerve fibers in the posterior ampullary nerve near the neuroepithelium. Calyx-bearing afferents were identified by their distinctive efferent-mediated responses. Such fibers receive inputs from both type I and type II hair cells. Type II inputs are made by synapses on the outer face of the calyx ending and on the boutons of dimorphic fibers. Quantal activity, consisting of brief mEPSPs, is reduced by lowering the external concentration of Ca2+ and blocked by the AMPA-receptor antagonist CNQX. Poisson statistics govern the timing of mEPSPs, which occur at high rates (250–2,500/s) in the absence of mechanical stimulation. Excitation produced by canal-duct indentation can increase mEPSP rates to nearly 5,000/s. As the rate increases, mEPSPs can change from a monophasic depolarization to a biphasic depolarizing–hyperpolarizing sequence, both of whose components are blocked by CNQX. Blockers of voltage-gated currents affect mEPSP size, which is decreased by TTX and is increased by linopirdine. mEPSP size decreases severalfold after impalement. The size decrease, although it may be triggered by the depolarization occurring during impalement, persists even at hyperpolarized membrane potentials. Nonquantal transmission is indicated by shot-noise calculations and by the presence of voltage modulations after quantal activity is abolished pharmacologically. An ultrastructural study shows that inner-face inputs from type I hair cells outnumber outer-face inputs from type II hair cells by an almost 6:1 ratio.

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Temporal Bone Studies of the Human Peripheral Vestibular System

Annals of Otology Rhinology & Laryngology ◽

10.1177/00034894001090s504 ◽

2000 ◽

Vol 109 (5_suppl) ◽

pp. 20-25 ◽

Cited By ~ 38

Author(s):

Kojiro Tsuji ◽

Steven D. Rauch ◽

Conrad Wall ◽

Luis Velázquez-Villaseñor ◽

Robert J. Glynn ◽

...

Keyword(s):

Hair Cell ◽

Hair Cells ◽

Ganglion Cells ◽

Significant Loss ◽

Small Sample ◽

Type I ◽

Type Ii ◽

Vestibular Hair Cells ◽

Scarpa's Ganglion ◽

Temporal Bones

Quantitative assessments of vestibular hair cells and Scarpa's ganglion cells were performed on 17 temporal bones from 10 individuals who had well-documented clinical evidence of aminoglycoside ototoxicity (streptomycin, kanamycin, and neomycin). Assessment of vestibular hair cells was performed by Nomarski (differential interference contrast) microscopy. Hair cell counts were expressed as densities (number of cells per 0.01 mm2 surface area of the sensory epithelium). The results were compared with age-matched normal data. Streptomycin caused a significant loss of both type I and type II hair cells in all 5 vestibular sense organs. In comparing the ototoxic effect on type I versus type II hair cells, there was greater type I hair cell loss for all 3 cristae, but not for the maculae. The vestibular ototoxic effects of kanamycin appeared to be similar to those of streptomycin, but the small sample size precluded definitive conclusions from being made. Neomycin did not cause loss of vestibular hair cells. Within the limits of this study (maximum postototoxicity survival time of 12 months), there was no significant loss of Scarpa's ganglion cells for any of the 3 drugs. The findings have implications in several clinical areas, including the correlation of vestibular test results to pathological findings, the rehabilitation of patients with vestibular ototoxicity, the use of aminoglycosides to treat Meniere's disease, and the development of a vestibular prosthesis.

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Efferent Synaptic Transmission at the Vestibular Type II Hair Cell Synapse

10.1101/2020.03.14.992180 ◽

2020 ◽

Author(s):

Zhou Yu ◽

J. Michael McIntosh ◽

Soroush Sadeghi ◽

Elisabeth Glowatzki

Keyword(s):

Hair Cells ◽

Nerve Fibers ◽

Repetitive Stimulation ◽

Vestibular Nerve ◽

Type I ◽

Type Ii ◽

Optogenetic Stimulation ◽

Vestibular Afferents ◽

Stimulation Of

ABSTRACTIn the vestibular peripheral organs, type I and type II hair cells (HCs) transmit incoming signals via glutamatergic quantal transmission onto afferent nerve fibers. Additionally, type I HCs transmit via ‘non-quantal’ transmission to calyx afferent fibers, by accumulation of glutamate and potassium in the synaptic cleft. Vestibular efferent inputs originating in the brainstem contact type II HCs and vestibular afferents. Here, we aimed at characterizing the synaptic efferent inputs to type II HCs using electrical and optogenetic stimulation of efferent fibers combined with in vitro whole-cell patch clamp recording from type II HCs in the rodent vestibular crista. Properties of efferent synaptic currents in type II HCs were similar to those found in cochlear hair cells and mediated by activation of α9/α10 nicotinic acetylcholine receptors (AChRs) and SK potassium channels. While efferents showed a low probability of release at low frequencies of stimulation, repetitive stimulation resulted in facilitation and increased probability of release. Notably, the membrane potential of type II HCs measured during optogenetic stimulation of efferents showed a strong hyperpolarization even in response to single pulses and was further enhanced by repetitive stimulation. Such efferent-mediated inhibition of type II HCs can provide a mechanism to adjust the contribution of signals from type I and type II HCs to vestibular nerve fibers. As a result, the relative input of type I hair cells to vestibular afferents will be strengthened, emphasizing the phasic properties of the incoming signal that are transmitted via fast non-quantal transmission.New and NoteworthyType II vestibular hair cells (HCs) receive inputs from efferent fibers originating in the brainstem. We used in vitro optogenetic and electrical stimulation of efferent fibers to study their synaptic inputs to type II HCs. Efferent inputs inhibited type II HCs, similar to cochlear efferent effects. We propose that efferent inputs adjust the contribution of signals from type I and type II HCs that report different components of the incoming signal to vestibular nerve fibers.

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Effects of KCNQ channel blockers on K+ currents in vestibular hair cells

AJP Cell Physiology ◽

10.1152/ajpcell.2001.280.3.c473 ◽

2001 ◽

Vol 280 (3) ◽

pp. C473-C480 ◽

Cited By ~ 29

Author(s):

Katherine J. Rennie ◽

Tianxiang Weng ◽

Manning J. Correia

Keyword(s):

Steady State ◽

Hair Cells ◽

Low Voltage ◽

Dissociation Constants ◽

Channel Blockers ◽

Type I ◽

Type Ii ◽

Kcnq Channels ◽

Vestibular Hair Cells ◽

Inward Currents

Linopirdine and XE991, selective blockers of K+ channels belonging to the KCNQ family, were applied to hair cells isolated from gerbil vestibular system and to hair cells in slices of pigeon crista. In type II hair cells, both compounds inhibited a slowly activating, slowly inactivating component of the macroscopic current recruited at potentials above −60 mV. The dissociation constants for linopirdine and XE991 block were <5 μM. A similar component of the current was also blocked by 50 μM capsaicin in gerbil type II hair cells. All three drugs blocked a current component that showed steady-state inactivation and a biexponential inactivation with time constants of ∼300 ms and 4 s. Linopirdine (10 μM) reduced inward currents through the low-voltage-activated K+ current in type I hair cells, but concentrations up to 200 μM had little effect on steady-state outward K+ current in these cells. These results suggest that KCNQ channels may be present in amniote vestibular hair cells.

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Temporal Bone Studies of the Human Peripheral Vestibular System

Annals of Otology Rhinology & Laryngology ◽

10.1177/00034894001090s502 ◽

2000 ◽

Vol 109 (5_suppl) ◽

pp. 3-13 ◽

Cited By ~ 110

Author(s):

Saumil N. Merchant ◽

Kojiro Tsuji ◽

Conrad Wall ◽

Luis Velázquez-Villaseñor ◽

Robert J. Glynn ◽

...

Keyword(s):

Hair Cell ◽

Hair Cells ◽

Type I ◽

Type Ii ◽

Sense Organs ◽

Age Related ◽

The Mean ◽

Cell Densities ◽

Temporal Bones ◽

Total Type

Quantitative studies of the vestibular system with serially sectioned human temporal bones have been limited because of difficulty in distinguishing hair cells from supporting cells and type I from type II hair cells. In addition, there is only a limited amount of normative data available regarding vestibular hair cell counts in humans. In this study, archival temporal bone sections were examined by Nomarski (differential interference contrast) microscopy, which permitted visualization of the cuticular plate and stereociliary bundle so as to allow unambiguous identification of hair cells. The density of type I, type II, and total numbers of vestibular hair cells in each of the 5 sense organs was determined in a set of 67 normal temporal bones that ranged from birth through 100 years of age. The mean total densities at birth were 76 to 79 cells per 0.01 mm2 in the cristae, 68 cells per 0.01 mm2 in the utricle, and 61 cells per 0.01 mm2 in the saccule. The ratio of type I to type II hair cells at birth was 2.4:1 in the cristae and 1.3:1 in the maculae. There was a highly significant age-related decline in all sense organs for total, type I, and type II hair cell densities that was best fit by a linear regression model. The cristae lost type I cells with advancing age at a significantly greater rate than the maculae, whereas age-related losses for type II cells occurred at the same rate for all 5 sense organs. Hair cell densities in the cristae were significantly higher at the periphery than at the center. There were no significant sex or interaural differences for any of the counts. Mathematical models were developed to calculate the mean and 95% prediction intervals for the total, type I, and type II hair cell densities in each sense organ on the basis of age. There was overall good agreement between the hair cell densities determined in this study and those reported by others using surface preparation techniques. Our data and related models will serve as a normative database that will be useful for comparison to counts made from subjects with known vestibular disorders.

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