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

2001 ◽  
Vol 280 (3) ◽  
pp. C473-C480 ◽  
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.

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

1996 ◽  
Vol 76 (2) ◽  
pp. 995-1004 ◽  
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.

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

2004 ◽  
Vol 19 (2) ◽  
pp. 155-169 ◽  
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.

Temporal Bone Studies of the Human Peripheral Vestibular System

2000 ◽  
Vol 109 (5_suppl) ◽  
pp. 20-25 ◽  
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.

Architecture of the Mouse Utricle: Macular Organization and Hair Bundle Heights

2008 ◽  
Vol 99 (2) ◽  
pp. 718-733 ◽  
Author(s):  
A. Li ◽  
J. Xue ◽  
E. H. Peterson
Keyword(s):  
Hair Cell ◽  
Hair Cells ◽  
Quantitative Data ◽  
Posterior Margin ◽  
Adult Mouse ◽  
Type I ◽  
Type Ii ◽  
Cell Type ◽  
Vestibular Hair Cells ◽  
Utricular Macula

Hair bundles are critical to mechanotransduction by vestibular hair cells, but quantitative data are lacking on vestibular bundles in mice or other mammals. Here we quantify bundle heights and their variation with macular locus and hair cell type in adult mouse utricular macula. We also determined that macular organization differs from previous reports. The utricle has ∼3,600 hair cells, half on each side of the line of polarity reversal (LPR). A band of low hair cell density corresponds to a band of calretinin-positive calyces, i.e., the striola. The relation between the LPR and the striola differs from previous reports in two ways. First, the LPR lies lateral to the striola instead of bisecting it. Second, the LPR follows the striolar trajectory anteriorly, but posteriorly it veers from the edge of the striola to reach the posterior margin of the macula. Consequently, more utricular bundles are oriented mediolaterally than previously supposed. Three hair cell classes are distinguished in calretinin-stained material: type II hair cells, type ID hair cells contacting calretinin-negative (dimorphic) afferents, and type IC hair cells contacting calretinin-positive (calyceal) afferents. They differ significantly on most bundle measures. Type II bundles have short stereocilia. Type IC bundles have kinocilia and stereocilia of similar heights, i.e., KS ratios (ratio of kinocilium to stereocilia heights) ∼1, unlike other receptor classes. In contrast to these class-specific differences, bundles show little regional variation except that KS ratios are lowest in the striola. These low KS ratios suggest that bundle stiffness is greater in the striola than in the extrastriola.

scholarly journals Supporting cells remove and replace sensory receptor hair cells in a balance organ of adult mice

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Stephanie A Bucks ◽  
Brandon C Cox ◽  
Brittany A Vlosich ◽  
James P Manning ◽  
Tot B Nguyen ◽  
...  
Keyword(s):  
Hair Cells ◽  
Head Movements ◽  
Sensory Receptor ◽  
Type I ◽  
Type Ii ◽  
Supporting Cells ◽  
Definitive Evidence ◽  
Vestibular Hair Cells ◽  
Adult Mice ◽  
Vestibular Organs

Vestibular hair cells in the inner ear encode head movements and mediate the sense of balance. These cells undergo cell death and replacement (turnover) throughout life in non-mammalian vertebrates. However, there is no definitive evidence that this process occurs in mammals. We used fate-mapping and other methods to demonstrate that utricular type II vestibular hair cells undergo turnover in adult mice under normal conditions. We found that supporting cells phagocytose both type I and II hair cells. Plp1-CreERT2-expressing supporting cells replace type II hair cells. Type I hair cells are not restored by Plp1-CreERT2-expressing supporting cells or by Atoh1-CreERTM-expressing type II hair cells. Destruction of hair cells causes supporting cells to generate 6 times as many type II hair cells compared to normal conditions. These findings expand our understanding of sensorineural plasticity in adult vestibular organs and further elucidate the roles that supporting cells serve during homeostasis and after injury.

scholarly journals Efferent synaptic transmission at the vestibular type II hair cell synapse

2020 ◽  
Vol 124 (2) ◽  
pp. 360-374 ◽  
Author(s):  
Zhou Yu ◽  
J. Michael McIntosh ◽  
Soroush G. Sadeghi ◽  
Elisabeth Glowatzki
Keyword(s):  
Hair Cells ◽  
Nerve Fibers ◽  
Type I ◽  
Type Ii ◽  
Vestibular Hair Cells ◽  
Efferent Neurons ◽  
The Brain ◽  
Cell Synapse ◽  
Stimulation Of

Type II vestibular hair cells (HCs) receive inputs from efferent neurons in the brain stem. We used in vitro optogenetic and electrical stimulation of vestibular efferent fibers to study their synaptic inputs to type II HCs. Stimulation of efferents inhibited type II HCs, similar to efferent effects on cochlear HCs. We propose that efferent inputs adjust the contribution of signals from type I and II HCs to vestibular nerve fibers.

Vestibular hair cells of the chick express the nicotinic acetylcholine receptor subunit α9

1999 ◽  
Vol 9 (5) ◽  
pp. 359-367
Author(s):  
Lawrence R. Lustig ◽  
Hakim Hiel ◽  
Paul A. Fuchs
Keyword(s):  
Acetylcholine Receptor ◽  
Nicotinic Acetylcholine Receptor ◽  
Hair Cells ◽  
Type I ◽  
Type Ii ◽  
Receptor Subunit ◽  
Rt Pcr ◽  
Nicotinic Acetylcholine ◽  
Vestibular Hair Cells ◽  
Cholinergic Signaling

The efferent cholinergic pathways to the vestibular periphery have yet to be fully characterized. While the nicotinic acetylcholine receptor subunit (nAChR) α9 is now regarded as the principle receptor for efferent cholinergic signaling to the organ of Corti, there is still uncertainty over how the more complex efferent effects of the labyrinth are produced. Recent experimental work has demonstrated that the nAChR α9 is present in the vestibular end-organs of the rat and mouse, suggesting that α9 may be one of the mediators of efferent cholinergic signaling in the vestibular periphery as well. In this experiment, we sought to determine whether α9 was also present in the vestibular end-organs of the chick. A homologue of α9 has been cloned recently from the chick cochlea. Using reverse transcription polymerase chain reaction (RT-PCR), individual vestibular end-organ preparations, including posterior ampulla, combined horizontal and superior ampulla, saccule, utricle, and the vestibular ganglion were screened for α9 messenger RNA expression. In each end-organ and the vestibular ganglion, a cDNA of the expected size was obtained by RT-PCR and was confirmed to be α9 by sequence analysis. Further, α9 mRNA was identified by RT-PCR from individually isolated type I and type II vestibular hair cells (single-cell RT-PCR). Lastly, insitu hybridization using digoxigenin-labeled α9 riboprobes confirmed the presence of α9 in type I and type II hair cells throughout the vestibular periphery. These results demonstrate the expression of α9 in the vestibular end-organs of the chick, and lend further support for the role of α9 as a mediator of efferent cholinergic signaling in vestibular hair cells.

scholarly journals Current Response in CaV1.3–/– Mouse Vestibular and Cochlear Hair Cells

2021 ◽  
Vol 15 ◽  
Author(s):  
Marco Manca ◽  
Piece Yen ◽  
Paolo Spaiardi ◽  
Giancarlo Russo ◽  
Roberta Giunta ◽  
...  
Keyword(s):  
Hair Cells ◽  
Signal Transmission ◽  
Basolateral Membrane ◽  
Semicircular Canals ◽  
Type I ◽  
Current Response ◽  
Type Ii ◽  
Current Profile ◽  
Cochlear Hair Cells ◽  
Vestibular Hair Cells

Signal transmission by sensory auditory and vestibular hair cells relies upon Ca2+-dependent exocytosis of glutamate. The Ca2+ current in mammalian inner ear hair cells is predominantly carried through CaV1.3 voltage-gated Ca2+ channels. Despite this, CaV1.3 deficient mice (CaV1.3–/–) are deaf but do not show any obvious vestibular phenotype. Here, we compared the Ca2+ current (ICa) in auditory and vestibular hair cells from wild-type and CaV1.3–/– mice, to assess whether differences in the size of the residual ICa could explain, at least in part, the two phenotypes. Using 5 mM extracellular Ca2+ and near-body temperature conditions, we investigated the cochlear primary sensory receptors inner hair cells (IHCs) and both type I and type II hair cells of the semicircular canals. We found that the residual ICa in both auditory and vestibular hair cells from CaV1.3–/– mice was less than 20% (12–19%, depending on the hair cell type and age investigated) compared to controls, indicating a comparable expression of CaV1.3 Ca2+ channels in both sensory organs. We also showed that, different from IHCs, type I and type II hair cells from CaV1.3–/– mice were able to acquire the adult-like K+ current profile in their basolateral membrane. Intercellular K+ accumulation was still present in CaV1.3–/– mice during IK,L activation, suggesting that the K+-based, non-exocytotic, afferent transmission is still functional in these mice. This non-vesicular mechanism might contribute to the apparent normal vestibular functions in CaV1.3–/– mice.

scholarly journals A Biophysical Model of Nonquantal Transmission at the Vestibular Hair Cell-Calyx Synapse: KLV currents Modulate Fast Electrical and Slow K+ potentials in the Synaptic Cleft

2021 ◽  
Author(s):  
Aravind Chenrayan Govindaraju ◽  
Imran H Quraishi ◽  
Anna Lysakowski ◽  
Ruth Anne Eatock ◽  
Robert M Raphael
Keyword(s):  
Hair Cell ◽  
Hair Cells ◽  
Low Voltage ◽  
Electrical Potential ◽  
Synaptic Cleft ◽  
Biophysical Model ◽  
Afferent Neuron ◽  
Type I ◽  
Significant Finding ◽  
Vestibular Hair Cells

Vestibular hair cells transmit information about head position and motion across synapses to primary afferent neurons. At some of these synapses, the afferent neuron envelopes the hair cell, forming an enlarged synaptic terminal referred to as a calyx. The vestibular hair cell-calyx synapse supports nonquantal transmission (NQT), a neurotransmitter-independent mechanism that is exceptionally fast. The underlying biophysical mechanisms that give rise to NQT are not fully understood. Here we present a computational model of NQT that integrates morphological and electrophysiological data. The model predicts that NQT involves two processes: changes in cleft K+ concentration, as previously recognized, and very fast changes in cleft electrical potential. A significant finding is that changes in cleft electrical potential are faster than changes in [K+] or quantal transmission. The electrical potential mechanism thus provides a basis for the exceptional speed of neurotransmission between type I hair cells and primary neurons and explains experimental observations of fast postsynaptic currents. The [K+] mechanism increases the gain of NQT. Both processes are mediated by current flow through low-voltage-activated K+ (KLV) channels located in both pre-synaptic (hair cell) and post-synaptic (calyx inner face) membranes. The model further demonstrates that the calyx morphology is necessary for NQT; as calyx height is increased, NQT increases in size, speed and efficacy at depolarizing the afferent neuron. We propose that the calyx evolved to enhance NQT and speed up signals that drive vestibular reflexes essential for stabilizing the eyes and neck and maintaining balance during rapid and complex head motions.

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