scholarly journals Absence of Voltage-Dependent Compliance in High-Frequency Cochlear Outer Hair Cells

2007 ◽  
Vol 8 (4) ◽  
pp. 464-473 ◽  
Author(s):  
Richard Hallworth
Keyword(s):  
Hair Cells ◽  
High Frequency ◽  
Outer Hair Cells ◽  
Voltage Dependent

scholarly journals Assessing evidence for adaptive evolution in two hearing-related genes important for high-frequency hearing in echolocating mammals

2021 ◽  
Author(s):  
Hui Wang ◽  
Hanbo Zhao ◽  
Yujia Chu ◽  
Jiang Feng ◽  
Keping Sun
Keyword(s):  
Adaptive Evolution ◽  
Hair Cells ◽  
High Frequency ◽  
Phylogenetic Trees ◽  
Outer Hair Cells ◽  
Functional Domain ◽  
Coding Region ◽  
Selective Pressures ◽  
Wide Range ◽  
Different Parts

Abstract High-frequency hearing is particularly important for echolocating bats and toothed whales. Previously, studies of the hearing-related genes Prestin, KCNQ4, and TMC1 documented that adaptive evolution of high-frequency hearing has taken place in echolocating bats and toothed whales. In this study, we present two additional candidate hearing-related genes, Shh and SK2, that may also have contributed to the evolution of echolocation in mammals. Shh is a member of the vertebrate Hedgehog gene family and is required in the specification of the mammalian cochlea. SK2 is expressed in both inner and outer hair cells, and it plays an important role in the auditory system. The coding region sequences of Shh and SK2 were obtained from a wide range of mammals with and without echolocating ability. The topologies of phylogenetic trees constructed using Shh and SK2 were different; however, multiple molecular evolutionary analyses showed that those two genes experienced different selective pressures in echolocating bats and toothed whales compared to non-echolocating mammals. In addition, several nominally significant positively selected sites were detected in the non-functional domain of the SK2 gene, indicating that different selective pressures were acting on different parts of the SK2 gene. This study has expanded our knowledge of the adaptive evolution of high-frequency hearing in echolocating mammals.

The CaV3.1 T-type Ca2+channel contributes to voltage-dependent calcium currents in rat outer hair cells

2008 ◽  
Vol 1201 ◽  
pp. 68-77 ◽  
Author(s):  
Akira Inagaki ◽  
Shinya Ugawa ◽  
Hisao Yamamura ◽  
Shingo Murakami ◽  
Shoichi Shimada
Keyword(s):  
Hair Cells ◽  
Outer Hair Cells ◽  
Calcium Currents ◽  
Voltage Dependent

Two types of voltage-dependent potassium channels in outer hair cells from the guinea pig cochlea

1999 ◽  
Vol 277 (5) ◽  
pp. C913-C925 ◽  
Author(s):  
Thierry van den Abbeele ◽  
Jacques Teulon ◽  
Patrice Tran Ba Huy
Keyword(s):  
Guinea Pig ◽  
Hair Cells ◽  
Basolateral Membrane ◽  
Outer Hair Cells ◽  
Catalytic Subunit ◽  
Patch Clamp Technique ◽  
Open Probability ◽  
Guinea Pig Cochlea ◽  
Voltage Dependent ◽  
Inside Out

Cell-attached and cell-free configurations of the patch-clamp technique were used to investigate the conductive properties and regulation of the major K+channels in the basolateral membrane of outer hair cells freshly isolated from the guinea pig cochlea. There were two major voltage-dependent K+ channels. A Ca2+-activated K+ channel with a high conductance (220 pS, P K/ P Na= 8) was found in almost 20% of the patches. The inside-out activity of the channel was increased by depolarizations above 0 mV and increasing the intracellular Ca2+concentration. External ATP or adenosine did not alter the cell-attached activity of the channel. The open probability of the excised channel remained stable for several minutes without rundown and was not altered by the catalytic subunit of protein kinase A (PKA) applied internally. The most frequent K+ channel had a low conductance and a small outward rectification in symmetrical K+ conditions (10 pS for inward currents and 20 pS for outward currents, P K/ P Na= 28). It was found significantly more frequently in cell-attached and inside-out patches when the pipette contained 100 μM acetylcholine. It was not sensitive to internal Ca2+, was inhibited by 4-aminopyridine, was activated by depolarization above −30 mV, and exhibited a rundown after excision. It also had a slow inactivation on ensemble-averaged sweeps in response to depolarizing pulses. The cell-attached activity of the channel was increased when adenosine was superfused outside the pipette. This effect also occurred with permeant analogs of cAMP and internally applied catalytic subunit of PKA. Both channels could control the cell membrane voltage of outer hair cells.

Voltage-dependent channels in dissociated outer hair cells of the guinea pig

1994 ◽  
Vol 251 (S1) ◽  
pp. S57-S60 ◽  
Author(s):  
T. Nakagawa ◽  
S. Kakehata ◽  
N. Akaike ◽  
S. Komune ◽  
T. Takasaka ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Hair Cells ◽  
Outer Hair Cells ◽  
Voltage Dependent

Prestin Expression in Cochlea of Bats Using Different Echolocation Systems

2014 ◽  
Vol 620 ◽  
pp. 248-252
Author(s):  
Qi Jiu Li ◽  
Xian De Zhang ◽  
Ting Ting Xu ◽  
Jiang Xia Yin
Keyword(s):  
Hair Cells ◽  
High Frequency ◽  
Low Frequency ◽  
Motor Protein ◽  
Outer Hair Cells ◽  
Intracellular Potential ◽  
First Time ◽  
Unique Ability

Outer hair cells (OHCs) have a unique ability to contract and elongate in response to changes in intracellular potential, and Prestin is the motor protein of the cochlea of the OHCs. It is the first time to invest the Prestin expression in different bat species. To invest Prestin expression in different bat species, which have different frequency, we did the coronal sections’ staining of the cochlea using immunhistochemistry. Experiment was designed to determine if the high-frequency bats’ OHCs have more expression than the low-frequency bats’OHCs. We found that the expression in three species was similar and had no obvious difference. Though the study of bats Prestin evolution suggested that Prestin has accelerating evolution in echolocation bats with high frequency, our we showed that the Prestin expression has nothing to do with the frequency, and the Prestin expression in high-frequency bats and low-frequency bats is similar.

Cisplatin blocks voltage-dependent calcium current in dissociated outer hair cells of guinea-pig cochlea

1994 ◽  
Vol 648 (2) ◽  
pp. 296-298 ◽  
Author(s):  
Takehito Yamamoto ◽  
Seiji Kakehata ◽  
Takehisa Saito ◽  
Hitoshi Saito ◽  
Norio Akaike
Keyword(s):  
Guinea Pig ◽  
Hair Cells ◽  
Calcium Current ◽  
Outer Hair Cells ◽  
Guinea Pig Cochlea ◽  
Voltage Dependent

Sensory transduction and frequency selectivity in the basal turn of the guinea-pig cochlea

1992 ◽  
Vol 336 (1278) ◽  
pp. 317-324 ◽  
Keyword(s):  
Guinea Pig ◽  
Hair Cells ◽  
High Frequency ◽  
Basilar Membrane ◽  
Receptor Potential ◽  
Outer Hair Cells ◽  
Sensory Transduction ◽  
Voltage Response ◽  
Operating Range ◽  
Dc Component

Receptor potentials recorded from outer hair cells (ohc ) and inner hair cells (ihc) in the basal highfrequency turn were com pared. The dc component of the ihc receptor potential is maximized to ensure that ihcs can signal a voltage response to high-frequency tones. The ohc dc component is minimized so that ohcs transduce in the most sensitive region of their operating range. The phase and magnitude of ohc receptor potentials were recorded as an indicator of the magnitude and phase of the energy which is fed back to the basilar membrane to provide the basis for the sharp tuning and fine sensitivity of the cochlea to tones. IHC receptor potentials were recorded to assess the net effect of the feedback on the mechanics of the cochlea. It was concluded that ohcs generate feedback which enhances the ihc responses only at the best frequency. At frequencies below cf, ihc dc responses are elicited only when the ohc ac responses begin to saturate.

Physiologically silent sodium channels in mammalian outer hair cells

1994 ◽  
Vol 72 (2) ◽  
pp. 1037-1040 ◽  
Author(s):  
C. M. Witt ◽  
H. Y. Hu ◽  
W. E. Brownell ◽  
D. Bertrand
Keyword(s):  
Sodium Channels ◽  
Hair Cells ◽  
Sodium Current ◽  
High Sensitivity ◽  
Outer Hair Cells ◽  
Inward Current ◽  
Cell Recording ◽  
Voltage Dependent

1. Voltage-dependent properties of isolated guinea pig outer hair cells (OHCs) were investigated using whole-cell recording. An inward current was detected in approximately 10% of the cells. This inward current was identified as belonging to the voltage-activated sodium current family on the basis of its high sensitivity to tetrodotoxin and the effect of substitution of impermeant ions. Although this is the first report of a sodium current in the mammalian cochlea, it differs from the classical neuronal sodium current by having a variable magnitude from cell to cell and an inactivation that is shifted to hyperpolarized potentials. The sensory processing role of hair cells in general and outer hair cells in particular could be disrupted by the presence of a regenerative voltage-dependent current. The functional role of the OHC sodium channels is puzzling, particularly as they may be silent in vivo.

Distribution of Ca2+ channels on cochlear outer hair cells revealed by fluorescent dihydropyridines

1996 ◽  
Vol 271 (3) ◽  
pp. C944-C949 ◽  
Author(s):  
T. Oshima ◽  
K. Ikeda ◽  
M. Furukawa ◽  
N. Ueda ◽  
H. Suzuki ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Hair Cells ◽  
Laser Scanning ◽  
Basolateral Membrane ◽  
Outer Hair Cells ◽  
Spatial Integration ◽  
Heterogeneous Distribution ◽  
Voltage Dependent ◽  
Basolateral Plasma Membrane ◽  
Ca2 Channels

Physiological evidence has shown that cochlear outer hair cells (OHC) possess L-type voltage-dependent Ca2+ channels through which Ca2+ enters the OHC during depolarization. Their subcellular distribution has, however, remained unclear. In this study, the distribution of L-type Ca2+ channels on the basolateral plasma membrane of OHC has been demonstrated by the use of a laser scanning confocal microscope (LSCM) and a fluorescent probe DMBODIPY-DHP. The fluorescent staining pattern on the basolateral wall is nonuniform, suggesting a heterogeneous distribution of the channels in the plasma membrane. Direct imaging of intracellular Ca2+ visualized in real time by means of the LSCM and the fluorescent Ca2+ probe fluo 3 revealed temporal and spatial integration of Ca2+ movements and Ca2+ channel distribution. Exposure to high-K+ solution induced heterogeneity in the subcellular increase in the intracellular Ca2+ concentration. These results suggest that the heterogeneous distribution of L-type Ca2+ channels on the basolateral membrane might induce heterogeneous intracellular Ca2+ distribution during electrical activity in the OHC.

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