The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Tobias Moser - One of the best experts on this subject based on the ideXlab platform.
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Quantitative optical nanophysiology of Ca2+ signaling at Inner Hair Cell active zones
Nature Communications, 2018Co-Authors: Jakob Neef, Nicolai T. Urban, Tzu-lun Ohn, Katrin I. Willig, Philippe Jean, Stefan W Hell, Thomas Frank, Tobias MoserAbstract:Ca2+ influx triggers the release of synaptic vesicles at the presynaptic active zone (AZ). A quantitative characterization of presynaptic Ca2+ signaling is critical for understanding synaptic transmission. However, this has remained challenging to establish at the required resolution. Here, we employ confocal and stimulated emission depletion (STED) microscopy to quantify the number (20–330) and arrangement (mostly linear 70 nm × 100–600 nm clusters) of Ca2+ channels at AZs of mouse cochlear Inner Hair Cells (IHCs). Establishing STED Ca2+ imaging, we analyze presynaptic Ca2+ signals at the nanometer scale and find confined elongated Ca2+ domains at normal IHC AZs, whereas Ca2+ domains are spatially spread out at the AZs of bassoon-deficient IHCs. Performing 2D-STED fluorescence lifetime analysis, we arrive at estimates of the Ca2+ concentrations at stimulated IHC AZs of on average 25 µM. We propose that IHCs form bassoon-dependent presynaptic Ca2+-channel clusters of similar density but scalable length, thereby varying the number of Ca2+ channels amongst individual AZs.Quantitatively studying components of the presynapse requires high resolution optical methods. Here the authors use confocal microscopy as well as 2D- and 3D-STED nanoscopy to quantify the number and activity of active zone Ca2+ channels in Inner Hair Cells.
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the role of mobile calcium buffers in synaptic transmission at the Inner Hair Cell ribbon synapse
Biophysical Journal, 2012Co-Authors: Tina Pangrsic, Nicola Strenzke, Beat Schwaller, Tobias MoserAbstract:Temporally precise sound encoding at the Inner Hair Cell (IHC) ribbon synapse is tightly regulated by calcium. The mobile calcium buffers calbindin, parvalbumin alpha and calretinin might contribute to shaping the presynaptic Ca2+ signals. We investigated the function of these calcium binding proteins in IHC synaptic transmission by examining the auditory phenotype of double and triple buffer knockout mice. Our results show that buffer deficiency does not significantly alter hearing thresholds; however, we observed a slight increase in peak and steady-state sound-driven spike rates of spiral ganglion nerve fibers in knockout mice. The presynaptic function of IHCs was first studied by perforated patch-clamp recordings of Ca2+ currents and exocytic membrane capacitance increments. The absence of mobile calcium buffering proteins augmented sustained exocytosis in IHCs while leaving the amplitude and kinetics of exocytosis of the readily-releasable pool unchanged. Further, Ca2+-dependent inactivation of calcium currents was stronger in IHCs of triple buffer knockout mice. In ruptured patch experiments we then tried to restore the calcium buffer capacity by adding exogeneous buffers. We estimated the concentration of endogenous buffers in IHCs to be equivalent to 0.5-1 mM BAPTA, which agrees well with previous estimates obtained by quantitative immunogold electron microscopy (Hackney et al., 2005). Our results demonstrate that calbindin, parvalbumin alpha and calretinin are involved in the regulation of synaptic transmission at the IHC ribbon synapse; however they do not seem to be essential for hearing, at least not during transient sound stimulation.
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mechanisms underlying the temporal precision of sound coding at the Inner Hair Cell ribbon synapse
The Journal of Physiology, 2006Co-Authors: Tobias Moser, Andreas Neef, Darina KhimichAbstract:Our auditory system is capable of perceiving the azimuthal location of a low frequency sound source with a precision of a few degrees. This requires the auditory system to detect time differences in sound arrival between the two ears down to tens of microseconds. The detection of these interaural time differences relies on network computation by auditory brainstem neurons sharpening the temporal precision of the afferent signals. Nevertheless, the system requires the Hair Cell synapse to encode sound with the highest possible temporal acuity. In mammals, each auditory nerve fibre receives input from only one Inner Hair Cell (IHC) synapse. Hence, this single synapse determines the temporal precision of the fibre. As if this was not enough of a challenge, the auditory system is also capable of maintaining such high temporal fidelity with acoustic signals that vary greatly in their intensity. Recent research has started to uncover the Cellular basis of sound coding. Functional and structural descriptions of synaptic vesicle pools and estimates for the number of Ca2+ channels at the ribbon synapse have been obtained, as have insights into how the receptor potential couples to the release of synaptic vesicles. Here, we review current concepts about the mechanisms that control the timing of transmitter release in Inner Hair Cells of the cochlea.
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calcium dependence of exocytosis and endocytosis at the cochlear Inner Hair Cell afferent synapse
Neuron, 2001Co-Authors: Dirk Beutner, Thomas Voets, Erwin Neher, Tobias MoserAbstract:Release of neurotransmitter at the Inner Hair Cell (IHC) afferent synapse is a fundamental step in translating sound into auditory nerve excitation. To study the Ca2+ dependence of the underlying vesicle fusion and subsequent endocytosis, we combined Ca2+ uncaging with membrane capacitance measurements in mouse IHCs. Rapid elevations in [Ca2+]i above 8 microM caused a biphasic capacitance increase corresponding to the fusion of approximately 40,000 vesicles. The kinetics of exocytosis displayed a fifth-order Ca2+ dependence reaching maximal rates of >3 x 10(7) vesicle/s. Exocytosis was always followed by slow, compensatory endocytosis (tau congruent with 15 s). Higher [Ca2+]i increased the contribution of a faster mode of endocytosis with a Ca2+ independent time constant of approximately 300 ms. These properties provide for rapid and sustained transmitter release from this large presynaptic terminal.
Anthony J. Ricci - One of the best experts on this subject based on the ideXlab platform.
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Localization of Inner Hair Cell mechanotransducer channels using high-speed calcium imaging
Nature Neuroscience, 2009Co-Authors: Maryline Beurg, Robert Fettiplace, Jong-hoon Nam, Anthony J. RicciAbstract:Hair Cells detect vibrations of their stereociliary bundle by activation of mechanically sensitive transducer channels. Although evidence suggests the transducer channels are near the stereociliary tops and are opened by force imparted by tip links connecting contiguous stereocilia, the exact channel site remains controversial. We used fast confocal imaging of fluorescence changes reflecting calcium entry during bundle stimulation to localize the channels. Calcium signals were visible in single stereocilia of rat cochlear Inner Hair Cells and were up to tenfold larger and faster in the second and third stereociliary rows than in the tallest first row. The number of functional stereocilia was proportional to transducer current amplitude, indicating that there were about two channels per stereocilium. Comparable results were obtained in outer Hair Cells. The observations, supported by theoretical simulations, suggest there are no functional mechanically sensitive transducer channels in first row stereocilia and imply the channels are present only at the bottom of the tip links. Mechanically sensitive transducer channels are responsible for the detection of sound-induced Hair Cell vibrations. However, the location of these channels in the stereociliary bundle has been unclear. Using high-speed calcium imaging, this study demonstrates that there are no transduction channels in the tallest row of stereocilia in the mammalian cochlea. Instead, these channels are more likely to be present in the bottom stereociliary rows.
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localization of Inner Hair Cell mechanotransducer channels using high speed calcium imaging
Nature Neuroscience, 2009Co-Authors: Maryline Beurg, Robert Fettiplace, Anthony J. RicciAbstract:Mechanically sensitive transducer channels are responsible for the detection of sound-induced Hair Cell vibrations. However, the location of these channels in the stereociliary bundle has been unclear. Using high-speed calcium imaging, this study demonstrates that there are no transduction channels in the tallest row of stereocilia in the mammalian cochlea. Instead, these channels are more likely to be present in the bottom stereociliary rows.
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Localization of Inner Hair Cell mechanotransducer channels using high-speed calcium imaging
Nature neuroscience, 2009Co-Authors: Maryline Beurg, Robert Fettiplace, Jong-hoon Nam, Anthony J. RicciAbstract:Hair Cells detect vibrations of their stereociliary bundle by activation of mechanically sensitive transducer channels. Although evidence suggests the transducer channels are near the stereociliary tops and are opened by force imparted by tip links connecting contiguous stereocilia, the exact channel site remains controversial. We used fast confocal imaging of fluorescence changes reflecting calcium entry during bundle stimulation to localize the channels. Calcium signals were visible in single stereocilia of rat cochlear Inner Hair Cells and were up to tenfold larger and faster in the second and third stereociliary rows than in the tallest first row. The number of functional stereocilia was proportional to transducer current amplitude, indicating that there were about two channels per stereocilium. Comparable results were obtained in outer Hair Cells. The observations, supported by theoretical simulations, suggest there are no functional mechanically sensitive transducer channels in first row stereocilia and imply the channels are present only at the bottom of the tip links.
Maryline Beurg - One of the best experts on this subject based on the ideXlab platform.
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Localization of Inner Hair Cell mechanotransducer channels using high-speed calcium imaging
Nature Neuroscience, 2009Co-Authors: Maryline Beurg, Robert Fettiplace, Jong-hoon Nam, Anthony J. RicciAbstract:Hair Cells detect vibrations of their stereociliary bundle by activation of mechanically sensitive transducer channels. Although evidence suggests the transducer channels are near the stereociliary tops and are opened by force imparted by tip links connecting contiguous stereocilia, the exact channel site remains controversial. We used fast confocal imaging of fluorescence changes reflecting calcium entry during bundle stimulation to localize the channels. Calcium signals were visible in single stereocilia of rat cochlear Inner Hair Cells and were up to tenfold larger and faster in the second and third stereociliary rows than in the tallest first row. The number of functional stereocilia was proportional to transducer current amplitude, indicating that there were about two channels per stereocilium. Comparable results were obtained in outer Hair Cells. The observations, supported by theoretical simulations, suggest there are no functional mechanically sensitive transducer channels in first row stereocilia and imply the channels are present only at the bottom of the tip links. Mechanically sensitive transducer channels are responsible for the detection of sound-induced Hair Cell vibrations. However, the location of these channels in the stereociliary bundle has been unclear. Using high-speed calcium imaging, this study demonstrates that there are no transduction channels in the tallest row of stereocilia in the mammalian cochlea. Instead, these channels are more likely to be present in the bottom stereociliary rows.
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localization of Inner Hair Cell mechanotransducer channels using high speed calcium imaging
Nature Neuroscience, 2009Co-Authors: Maryline Beurg, Robert Fettiplace, Anthony J. RicciAbstract:Mechanically sensitive transducer channels are responsible for the detection of sound-induced Hair Cell vibrations. However, the location of these channels in the stereociliary bundle has been unclear. Using high-speed calcium imaging, this study demonstrates that there are no transduction channels in the tallest row of stereocilia in the mammalian cochlea. Instead, these channels are more likely to be present in the bottom stereociliary rows.
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Localization of Inner Hair Cell mechanotransducer channels using high-speed calcium imaging
Nature neuroscience, 2009Co-Authors: Maryline Beurg, Robert Fettiplace, Jong-hoon Nam, Anthony J. RicciAbstract:Hair Cells detect vibrations of their stereociliary bundle by activation of mechanically sensitive transducer channels. Although evidence suggests the transducer channels are near the stereociliary tops and are opened by force imparted by tip links connecting contiguous stereocilia, the exact channel site remains controversial. We used fast confocal imaging of fluorescence changes reflecting calcium entry during bundle stimulation to localize the channels. Calcium signals were visible in single stereocilia of rat cochlear Inner Hair Cells and were up to tenfold larger and faster in the second and third stereociliary rows than in the tallest first row. The number of functional stereocilia was proportional to transducer current amplitude, indicating that there were about two channels per stereocilium. Comparable results were obtained in outer Hair Cells. The observations, supported by theoretical simulations, suggest there are no functional mechanically sensitive transducer channels in first row stereocilia and imply the channels are present only at the bottom of the tip links.
Said Safieddine - One of the best experts on this subject based on the ideXlab platform.
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two photon imaging of calcium signalling at the mouse Inner Hair Cell ribbon synapse
Biophysical Journal, 2010Co-Authors: Jonathan Ashmore, Christine Petit, Siân Culley, Jacques Boutet De Monvel, Said SafieddineAbstract:The information sent from each cochlear Inner Hair Cell (IHC) to the afferent nerve is determined by 10-20 ribbon synapses, structures specialised for rapid release of vesicles upon Cell depolarization. To study the IHC calcium domains during transmitter release in mature wild-type mice, we have imaged and simultaneously measured currents in IHCs through an apical opening in the isolated temporal bone. Cells were recorded on the stage of an upright 2PCLSM at room temperature, superfused with medium containing 2mM Ca2+. IHCs could be visualised either with oblique optics or by using 830nm trans-illumination through bone structures. Using whole-Cell tight seal recording, with Cs+ containing pipettes to reduce large outward currents, the I-V curve of the IHCs exhibit a Ca current with peak magnitude of approx 80pA near −20mV. To observe the distribution of Ca2+ entry in the vicinity of the ribbon sites, Cells we pipette-loaded IHCs with either high or low affinity Ca2+ dyes (200uM OGB1 or OGB5N respectively) and imaged the basal IHC pole up to maximal rates of 70 frames/s during 20 ms or 100ms depolarizing steps to 0mV. At the fastest rates, the images derived from within single Cells showed an initial punctuate rise of Ca2+ at the presumed synaptic sites with a larger increase at the neural side, a possible correlate of differing afferent thresholds known to characterise auditory nerve fibres. The sites were correlated with fluorescent hotspot distribution identified by IHC FM-dye uptake. The distribution of sites, the localisation of signal maxima close to (<3um) the plasma-membrane and recovery time constant (∼100ms) of Ca2+ influx also suggests that intrinsic Ca2+ buffering near the ribbon synapse was not significantly perturbed. Supported by EuroHear, the Physiological Society (SC), and College de France (JBM).
Richard A Altschuler - One of the best experts on this subject based on the ideXlab platform.
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treatment with piribedil and memantine reduces noise induced loss of Inner Hair Cell synaptic ribbons
Scientific Reports, 2016Co-Authors: Richard A Altschuler, Noel L Wys, Diane M Prieskorn, Cathy Martin, Susan Deremer, Sanford C Bledsoe, Josef M MillerAbstract:Noise overstimulation can induce loss of synaptic ribbons associated with loss of Inner Hair Cell – Auditory Nerve synaptic connections. This study examined if systemic administration of Piribedil, a dopamine agonist that reduces the sound evoked auditory nerve compound action potential and/or Memantine, an NMDA receptor open channel blocker, would reduce noise-induced loss of Inner Hair Cell ribbons. Rats received systemic Memantine and/or Piribedil for 3 days before and 3 days after a 3 hour 4 kHz octave band noise at 117 dB (SPL). At 21 days following the noise there was a 26% and 38% loss of synaptic ribbons in regions 5.5 and 6.5 mm from apex, respectively, elevations in 4-, 8- and 20 kHz tonal ABR thresholds and reduced dynamic output at higher intensities of stimulation. Combined treatment with Piribedil and Memantine produced a significant reduction in the noise-induced loss of ribbons in both regions and changes in ABR sensitivity and dynamic responsiveness. Piribedil alone gave significant reduction in only the 5.5 mm region and Memantine alone did not reach significance in either region. Results identify treatments that could prevent the hearing loss and hearing disorders that result from noise-induced loss of Inner Hair Cell – Auditory Nerve synaptic connections.
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age related changes in auditory nerve Inner Hair Cell connections Hair Cell numbers auditory brain stem response and gap detection in um het4 mice
Neuroscience, 2015Co-Authors: Richard A Altschuler, David F Dolan, Karin Halsey, Ariane C Kanicki, N Deng, C Martin, J Eberle, David C Kohrman, Richard A Miller, Jochen SchachtAbstract:This study compared the timing of appearance of three components of age-related hearing loss that determine the pattern and severity of presbycusis: the functional and structural pathologies of sensory Cells and neurons and changes in Gap Detection, the latter as an indicator of auditory temporal processing. Using UM-HET4 mice, genetically heterogeneous mice derived from four inbred strains, we studied the integrity of Inner and outer Hair Cells by position along the cochlear spiral, Inner Hair Cell-auditory nerve connections, spiral ganglion neurons, and determined auditory thresholds, as well as pre-pulse and gap inhibition of the acoustic startle reflex (ASR). Comparisons were made between mice of 5-7, 22-24 and 27-29 months of age. There was individual variability among mice in the onset and extent of age-related auditory pathology. At 22-24 months of age a moderate to large loss of outer Hair Cells was restricted to the apical third of the cochlea and threshold shifts in auditory brain stem response were minimal. There was also a large and significant loss of Inner Hair Cell – auditory nerve connections and a significant reduction in Gap Detection. The expression of Ntf3 in the cochlea was significantly reduced. At 27-29 months of age there was no further change in the mean number of synaptic connections per Inner Hair Cell or in gap detection, but a moderate to large loss of outer Hair Cells was found across all cochlear turns as well as significantly increased ABR threshold shifts at 4, 12, 24 and 48 kHz. A statistical analysis of correlations on an individual animal basis revealed that neither the Hair Cell loss nor the ABR threshold shifts correlated with loss of gap detection or with the loss of connections, consistent with independent pathological mechanisms.
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neurotrophins can enhance spiral ganglion Cell survival after Inner Hair Cell loss
International Journal of Developmental Neuroscience, 1997Co-Authors: Josef M Miller, David H Chi, Leonard J Okeeffe, Paul Kruszka, Yehoash Raphael, Richard A AltschulerAbstract:Following destruction of sensory Cells of the organ of Corti, spiral ganglion Cells (SGC) in the guinea pig degenerate. Chronic electrical stimulation via cochlear prostheses can enhance their survival, with the effect blocked by stopping the electrically elicited action potentials with tetrodotoxin. Blocking action potentials in the normal hearing ear with tetrodotoxin, however, does not cause degeneration. This suggests that in the pathological ear VIII N activity acts as a survival factor, while in the normal ear there are other survival factors that maintain SGCs. We examined neurotrophins, as survival factors in the deafened ear. Two weeks of treatment with BDNF (brain derived neurotrophic factor) administered chronically via a mini-osmotic pump into scala tympani at 50 ng/ml, provided a statistically significant enhanced SGC survival over untreated deafened ears or deafened ears treated with artificial perilymph. Neurotrophin 3 provided some enhanced survival, but this was not statistically significant over untreated deafened ears. These observations suggest there are survival factors in the Inner ear, including those coupled to direct activation of the auditory nerve fibers, that may serve to maintain the auditory nerve. These factors may be applied following deafness to maintain and enhance neural populations and to increase benefits to the profoundly deaf receiving cochlear implants.