1
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Kostrikov S, Hjortkjaer J, Dau T, Corfas G, Liberman LD, Liberman MC. A modiolar-pillar gradient in auditory-nerve dendritic length: A novel post-synaptic contribution to dynamic range? Hear Res 2025; 456:109172. [PMID: 39708764 PMCID: PMC11772111 DOI: 10.1016/j.heares.2024.109172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2024] [Revised: 12/06/2024] [Accepted: 12/17/2024] [Indexed: 12/23/2024]
Abstract
Auditory-nerve fibers (ANFs) from a given cochlear region can vary in threshold sensitivity by up to 60 dB, corresponding to a 1000-fold difference in stimulus level, although each fiber innervates a single inner hair cell (IHC) via a single synapse. ANFs with high-thresholds also have low spontaneous rates (SRs) and synapse on the side of the IHC closer to the modiolus, whereas the low-threshold, high-SR fibers synapse on the side closer to the pillar cells. Prior biophysical work has identified modiolar-pillar differences in both pre- and post-synaptic properties, but a comprehensive explanation for the wide range of sensitivities remains elusive. Here, in guinea pigs, we used immunostaining for several neuronal markers, including Caspr, a key protein in nodes of Ranvier, to reveal a novel modiolar-pillar gradient in the location of the first ANF heminodes, presumed to be the site of the spike generator, just outside the sensory epithelium. Along the cochlea, from apex to base, the unmyelinated terminal dendrites of modiolar ANFs were 2-4 times longer than those of pillar ANFs. This modiolar-pillar gradient in dendritic length, coupled with the 2-4 fold smaller caliber of modiolar dendrites seen in prior single-fiber labeling studies, suggests there could be a large difference in the number of length constants between the synapse and the spike initiation zone for low- vs high-SR fibers. The resultant differences in attenuation of post-synaptic potentials propagating along these unmyelinated dendrites could be a key contributor to the observed range of threshold sensitivities among ANFs.
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Affiliation(s)
- Serhii Kostrikov
- Department of Health Technology, Centre for Auditory Neuroscience, Hearing Systems, Technical University of Denmark, Lyngby, Denmark
| | - Jens Hjortkjaer
- Department of Health Technology, Centre for Auditory Neuroscience, Hearing Systems, Technical University of Denmark, Lyngby, Denmark
| | - Torsten Dau
- Department of Health Technology, Centre for Auditory Neuroscience, Hearing Systems, Technical University of Denmark, Lyngby, Denmark
| | - Gabriel Corfas
- Department of Otolaryngology-Head and Neck Surgery, Kresge Hearing Research Institute, University of Michigan, Ann Arbor, MI, United States
| | - Leslie D Liberman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA, United States
| | - M Charles Liberman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA, United States; Department of Otolaryngology-Head & Neck Surgery, Harvard Medical School, Boston, MA, United States.
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2
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Jaime Tobón LM, Moser T. Bridging the gap between presynaptic hair cell function and neural sound encoding. eLife 2024; 12:RP93749. [PMID: 39718472 DOI: 10.7554/elife.93749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2024] Open
Abstract
Neural diversity can expand the encoding capacity of a circuitry. A striking example of diverse structure and function is presented by the afferent synapses between inner hair cells (IHCs) and spiral ganglion neurons (SGNs) in the cochlea. Presynaptic active zones at the pillar IHC side activate at lower IHC potentials than those of the modiolar side that have more presynaptic Ca2+ channels. The postsynaptic SGNs differ in their spontaneous firing rates, sound thresholds, and operating ranges. While a causal relationship between synaptic heterogeneity and neural response diversity seems likely, experimental evidence linking synaptic and SGN physiology has remained difficult to obtain. Here, we aimed at bridging this gap by ex vivo paired recordings of murine IHCs and postsynaptic SGN boutons with stimuli and conditions aimed to mimic those of in vivo SGN characterization. Synapses with high spontaneous rate of release (SR) were found predominantly on the pillar side of the IHC. These high SR synapses had larger and more temporally compact spontaneous EPSCs, lower voltage thresholds, tighter coupling of Ca2+ channels and vesicular release sites, shorter response latencies, and higher initial release rates. This study indicates that synaptic heterogeneity in IHCs directly contributes to the diversity of spontaneous and sound-evoked firing of SGNs.
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Affiliation(s)
- Lina María Jaime Tobón
- Auditory Neuroscience and Synaptic Nanophysiology Group, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
- Institute for Auditory Neuroscience, University Medical Center Göttingen, Göttingen, Germany
- Collaborative Research Center, University of Göttingen, Göttingen, Germany
- Cluster of Excellence 'Multiscale Bioimaging of Excitable Cells', Göttingen, Germany
| | - Tobias Moser
- Auditory Neuroscience and Synaptic Nanophysiology Group, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
- Institute for Auditory Neuroscience, University Medical Center Göttingen, Göttingen, Germany
- Collaborative Research Center, University of Göttingen, Göttingen, Germany
- Cluster of Excellence 'Multiscale Bioimaging of Excitable Cells', Göttingen, Germany
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3
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Wang Y, Huang L, Cen X, Liang Y, Chen K. Canonical MAPK signaling in auditory neuropathy. Biochim Biophys Acta Mol Basis Dis 2024; 1871:167619. [PMID: 39662753 DOI: 10.1016/j.bbadis.2024.167619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2024] [Revised: 11/27/2024] [Accepted: 12/06/2024] [Indexed: 12/13/2024]
Abstract
Auditory neuropathy (AN) is an under-recognized form of hearing loss characterized by lesions in inner hair cells (IHCs), ribbon synapses and spiral ganglion neurons (SGNs). The lack of a targeted therapy for AN has increased the need for a better understanding of the pathogenic mechanism of AN. As mitogen-activated protein kinase (MAPK) signaling is ubiquitous in many biological processes, its alteration may facilitate the pathogenesis of multiple sites in AN. Here, we summaries the characteristics of AN under different molecular bases and first explore the mechanism of MAPK at different lesion sites. Alterations of extracellular signal-regulated kinase (ERK)/MAPK occur in IHCs and SGNs, whereas modulations of p38 and c-Jun NH2-terminal kinase (JNK) were found in ribbon synapses and SGNs. In conclusion, inductive MAPK alterations in the pathogenesis and development of AN are likely to represent a potential therapeutic target to guide the development of treatments.
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Affiliation(s)
- Yueying Wang
- Otorhinolaryngology Hospital, the First Affiliated Hospital, Sun Yat-sen University, Guangzhou 510080, China; Institute of Otorhinolaryngology, Sun Yat-sen University, Guangzhou 510080, China
| | - Lusha Huang
- Otorhinolaryngology Hospital, the First Affiliated Hospital, Sun Yat-sen University, Guangzhou 510080, China; Institute of Otorhinolaryngology, Sun Yat-sen University, Guangzhou 510080, China
| | - Xiaoqing Cen
- Otorhinolaryngology Hospital, the First Affiliated Hospital, Sun Yat-sen University, Guangzhou 510080, China; Institute of Otorhinolaryngology, Sun Yat-sen University, Guangzhou 510080, China
| | - Yue Liang
- Otorhinolaryngology Hospital, the First Affiliated Hospital, Sun Yat-sen University, Guangzhou 510080, China; Institute of Otorhinolaryngology, Sun Yat-sen University, Guangzhou 510080, China
| | - Kaitian Chen
- Otorhinolaryngology Hospital, the First Affiliated Hospital, Sun Yat-sen University, Guangzhou 510080, China; Institute of Otorhinolaryngology, Sun Yat-sen University, Guangzhou 510080, China.
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4
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Kostrikov S, Hjortkjaer J, Dau T, Corfas G, Liberman LD, Liberman MC. A modiolar-pillar gradient in auditory-nerve dendritic length: a novel post-synaptic contribution to dynamic range? BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.11.04.621861. [PMID: 39574647 PMCID: PMC11580876 DOI: 10.1101/2024.11.04.621861] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2024]
Abstract
Auditory-nerve fibers (ANFs) from a given cochlear region can vary in threshold sensitivity by up to 60 dB, corresponding to a 1000-fold difference in stimulus level, although each fiber innervates a single inner hair cell (IHC) via a single synapse. ANFs with high-thresholds also have low spontaneous rates (SRs) and synapse on the side of the IHC closer to the modiolus, whereas the low-threshold, high-SR fibers synapse on the side closer to the pillar cells. Prior biophysical work has identified modiolar-pillar differences in both pre- and post-synaptic properties, but a comprehensive explanation for the wide range of sensitivities remains elusive. Here, in guinea pigs, we used immunostaining for several neuronal markers, including Caspr, a key protein in nodes of Ranvier, to reveal a novel modiolar-pillar gradient in the location of the first ANF heminodes, presumed to be the site of the spike generator, just outside the sensory epithelium. Along the cochlea, from apex to base, the unmyelinated terminal dendrites of modiolar ANFs were 2 - 4 times longer than those of pillar ANFs. This modiolar-pillar gradient in dendritic length, coupled with the 2 - 4 fold smaller caliber of modiolar dendrites seen in prior single-fiber labeling studies, suggests there could be a large difference in the number of length constants between the synapse and the spike initiation zone for low- vs high-SR fibers. The resultant differences in attenuation of post-synaptic potentials propagating along these unmyelinated dendrites could be a key contributor to the observed range of threshold sensitivities among ANFs.
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5
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Cassinotti LR, Ji L, Yuk MC, Desai AS, Cass ND, Amir ZA, Corfas G. Hidden hearing loss in a Charcot-Marie-Tooth type 1A mouse model. JCI Insight 2024; 9:e180315. [PMID: 39178128 PMCID: PMC11466197 DOI: 10.1172/jci.insight.180315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Accepted: 08/15/2024] [Indexed: 08/25/2024] Open
Abstract
Hidden hearing loss (HHL), a recently described auditory neuropathy characterized by normal audiometric thresholds but reduced sound-evoked cochlear compound action potentials, has been proposed to contribute to hearing difficulty in noisy environments in people with normal hearing thresholds and has become a widespread complaint. While most studies on HHL pathogenesis have focused on inner hair cell (IHC) synaptopathy, we recently showed that transient auditory nerve (AN) demyelination also causes HHL in mice. To test the effect of myelinopathy on hearing in a clinically relevant model, we studied a mouse model of Charcot-Marie-Tooth type 1A (CMT1A), the most prevalent hereditary peripheral neuropathy in humans. CMT1A mice exhibited the functional hallmarks of HHL together with disorganization of AN heminodes near the IHCs with minor loss of AN fibers. These results support the hypothesis that mild disruptions of AN myelination can cause HHL and that heminodal defects contribute to the alterations in the sound-evoked cochlear compound action potentials seen in this mouse model. Furthermore, these findings suggest that patients with CMT1A or other mild peripheral neuropathies are likely to suffer from HHL. Furthermore, these results suggest that studies of hearing in patients with CMT1A might help develop robust clinical tests for HHL, which are currently lacking.
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Smith KE, Lezmy J, Arancibia-Cárcamo IL, Bullen A, Jagger DJ, Attwell D. Developmental shaping of node of Ranvier geometry contributes to spike timing maturation in primary auditory afferents. Cell Rep 2024; 43:114651. [PMID: 39178117 DOI: 10.1016/j.celrep.2024.114651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Revised: 06/06/2024] [Accepted: 08/01/2024] [Indexed: 08/25/2024] Open
Abstract
Sound is encoded by action potentials in spiral ganglion neurons (SGNs), the auditory afferents from the cochlea. Rapid action potential transmission along SGNs is crucial for quick reactions to sounds, and binaural differences in action potential arrival time at the SGN output synapses enable sound localization based on interaural time or phase differences. SGN myelination increases conduction speed but other cellular changes may contribute. We show that nodes of Ranvier along peripherally and centrally directed SGN neurites form around hearing onset, but peri-somatic nodes mature later. There follows an adjustment of nodal geometry, notably a decrease in length and increase in diameter. Computational modeling predicts this increases conduction speed by >4%, and that four additional myelin wraps would be required on internodes to achieve the same conduction speed increase. We propose that nodal geometry changes optimize signal conduction for mature sound coding and decrease the energy needed for myelination.
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Affiliation(s)
- Katie E Smith
- UCL Ear Institute, University College London, 332 Gray's Inn Road, London WC1X 8EE, UK.
| | - Jonathan Lezmy
- Department of Neuroscience, Physiology & Pharmacology, University College London, Gower St., London WC1E 6BT, UK
| | - I Lorena Arancibia-Cárcamo
- UK Dementia Research Institute, Institute of Neurology, London WC1N 3BG, UK; Francis Crick Institute, London NW1 1AT, UK
| | - Anwen Bullen
- UCL Ear Institute, University College London, 332 Gray's Inn Road, London WC1X 8EE, UK
| | - Daniel J Jagger
- UCL Ear Institute, University College London, 332 Gray's Inn Road, London WC1X 8EE, UK
| | - David Attwell
- Department of Neuroscience, Physiology & Pharmacology, University College London, Gower St., London WC1E 6BT, UK.
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7
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Cassinotti LR, Ji L, Yuk MC, Desai AS, Cass ND, Amir ZA, Corfas G. Hidden hearing loss in a Charcot-Marie-Tooth type 1A mouse model. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.12.14.571732. [PMID: 38168255 PMCID: PMC10760174 DOI: 10.1101/2023.12.14.571732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Hidden hearing loss (HHL), a recently described auditory neuropathy characterized by normal audiometric thresholds but reduced sound-evoked cochlear compound action potentials, has been proposed to contribute to hearing difficulty in noisy environments in people with normal hearing thresholds, a widespread complaint. While most studies on HHL pathogenesis have focused on inner hair cell (IHC) synaptopathy, we recently showed that transient auditory nerve (AN) demyelination also causes HHL in mice. To test the impact of myelinopathy on hearing in a clinically relevant model, we studied a mouse model of Charcot-Marie-Tooth type 1A (CMT1A), the most prevalent hereditary peripheral neuropathy in humans. CMT1A mice exhibited the functional hallmarks of HHL together with disorganization of AN heminodes near the IHCs with minor loss of AN fibers. These results support the hypothesis that mild disruptions of AN myelination can cause HHL, and that heminodal defects contribute to the alterations in the sound-evoked cochlear compound action potentials seen in this mouse model. Also, these findings suggest that patients with CMT1A or other mild peripheral neuropathies are likely to suffer from HHL. Furthermore, these results suggest that studies of hearing in CMT1A patients might help develop robust clinical tests for HHL, which are currently lacking.
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8
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Jaime Tobón LM, Moser T. Ca 2+ regulation of glutamate release from inner hair cells of hearing mice. Proc Natl Acad Sci U S A 2023; 120:e2311539120. [PMID: 38019860 DOI: 10.1073/pnas.2311539120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Accepted: 10/11/2023] [Indexed: 12/01/2023] Open
Abstract
In our hearing organ, sound is encoded at ribbon synapses formed by inner hair cells (IHCs) and spiral ganglion neurons (SGNs). How the underlying synaptic vesicle (SV) release is controlled by Ca2+ in IHCs of hearing animals remained to be investigated. Here, we performed patch-clamp SGN recordings of the initial rate of release evoked by brief IHC Ca2+-influx in an ex vivo cochlear preparation from hearing mice. We aimed to closely mimic physiological conditions by perforated-patch recordings from IHCs kept at the physiological resting potential and at body temperature. We found release to relate supralinearly to Ca2+-influx (power, m: 4.3) when manipulating the [Ca2+] available for SV release by Zn2+-flicker-blocking of the single Ca2+-channel current. In contrast, a near linear Ca2+ dependence (m: 1.2 to 1.5) was observed when varying the number of open Ca2+-channels during deactivating Ca2+-currents and by dihydropyridine channel-inhibition. Concurrent changes of number and current of open Ca2+-channels over the range of physiological depolarizations revealed m: 1.8. These findings indicate that SV release requires ~4 Ca2+-ions to bind to their Ca2+-sensor of fusion. We interpret the near linear Ca2+-dependence of release during manipulations that change the number of open Ca2+-channels to reflect control of SV release by the high [Ca2+] in the Ca2+-nanodomain of one or few nearby Ca2+-channels. We propose that a combination of Ca2+ nanodomain control and supralinear intrinsic Ca2+-dependence of fusion optimally links SV release to the timing and amplitude of the IHC receptor potential and separates it from other IHC Ca2+-signals unrelated to afferent synaptic transmission.
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Affiliation(s)
- Lina María Jaime Tobón
- Auditory Neuroscience and Synaptic Nanophysiology Group, Max Planck Institute for Multidisciplinary Sciences, Göttingen 37077, Germany
- Institute for Auditory Neuroscience, University Medical Center Göttingen, Göttingen 37075, Germany
- Collaborative Research Center 889, University of Göttingen, Göttingen 37075, Germany
- Multiscale Bioimaging of Excitable Cells, Cluster of Excellence, Göttingen 37075, Germany
| | - Tobias Moser
- Auditory Neuroscience and Synaptic Nanophysiology Group, Max Planck Institute for Multidisciplinary Sciences, Göttingen 37077, Germany
- Institute for Auditory Neuroscience, University Medical Center Göttingen, Göttingen 37075, Germany
- Collaborative Research Center 889, University of Göttingen, Göttingen 37075, Germany
- Multiscale Bioimaging of Excitable Cells, Cluster of Excellence, Göttingen 37075, Germany
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Moser T, Karagulyan N, Neef J, Jaime Tobón LM. Diversity matters - extending sound intensity coding by inner hair cells via heterogeneous synapses. EMBO J 2023; 42:e114587. [PMID: 37800695 PMCID: PMC10690447 DOI: 10.15252/embj.2023114587] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 06/26/2023] [Accepted: 08/07/2023] [Indexed: 10/07/2023] Open
Abstract
Our sense of hearing enables the processing of stimuli that differ in sound pressure by more than six orders of magnitude. How to process a wide range of stimulus intensities with temporal precision is an enigmatic phenomenon of the auditory system. Downstream of dynamic range compression by active cochlear micromechanics, the inner hair cells (IHCs) cover the full intensity range of sound input. Yet, the firing rate in each of their postsynaptic spiral ganglion neurons (SGNs) encodes only a fraction of it. As a population, spiral ganglion neurons with their respective individual coding fractions cover the entire audible range. How such "dynamic range fractionation" arises is a topic of current research and the focus of this review. Here, we discuss mechanisms for generating the diverse functional properties of SGNs and formulate testable hypotheses. We postulate that an interplay of synaptic heterogeneity, molecularly distinct subtypes of SGNs, and efferent modulation serves the neural decomposition of sound information and thus contributes to a population code for sound intensity.
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Affiliation(s)
- Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLabUniversity Medical Center GöttingenGöttingenGermany
- Auditory Neuroscience and Synaptic Nanophysiology GroupMax Planck Institute for Multidisciplinary SciencesGöttingenGermany
- Cluster of Excellence “Multiscale Bioimaging of Excitable Cells”GöttingenGermany
| | - Nare Karagulyan
- Institute for Auditory Neuroscience and InnerEarLabUniversity Medical Center GöttingenGöttingenGermany
- Auditory Neuroscience and Synaptic Nanophysiology GroupMax Planck Institute for Multidisciplinary SciencesGöttingenGermany
- Hertha Sponer CollegeCluster of Excellence “Multiscale Bioimaging of Excitable Cells” Cluster of ExcellenceGöttingenGermany
| | - Jakob Neef
- Institute for Auditory Neuroscience and InnerEarLabUniversity Medical Center GöttingenGöttingenGermany
- Auditory Neuroscience and Synaptic Nanophysiology GroupMax Planck Institute for Multidisciplinary SciencesGöttingenGermany
| | - Lina María Jaime Tobón
- Institute for Auditory Neuroscience and InnerEarLabUniversity Medical Center GöttingenGöttingenGermany
- Auditory Neuroscience and Synaptic Nanophysiology GroupMax Planck Institute for Multidisciplinary SciencesGöttingenGermany
- Hertha Sponer CollegeCluster of Excellence “Multiscale Bioimaging of Excitable Cells” Cluster of ExcellenceGöttingenGermany
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Khurana L, Harczos T, Moser T, Jablonski L. En route to sound coding strategies for optical cochlear implants. iScience 2023; 26:107725. [PMID: 37720089 PMCID: PMC10502376 DOI: 10.1016/j.isci.2023.107725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/19/2023] Open
Abstract
Hearing loss is the most common human sensory deficit. Severe-to-complete sensorineural hearing loss is often treated by electrical cochlear implants (eCIs) bypassing dysfunctional or lost hair cells by direct stimulation of the auditory nerve. The wide current spread from each intracochlear electrode array contact activates large sets of tonotopically organized neurons limiting spectral selectivity of sound coding. Despite many efforts, an increase in the number of independent eCI stimulation channels seems impossible to achieve. Light, which can be better confined in space than electric current may help optical cochlear implants (oCIs) to overcome eCI shortcomings. In this review, we present the current state of the optogenetic sound encoding. We highlight optical sound coding strategy development capitalizing on the optical stimulation that requires fine-grained, fast, and power-efficient real-time sound processing controlling dozens of microscale optical emitters as an emerging research area.
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Affiliation(s)
- Lakshay Khurana
- Institute for Auditory Neuroscience, University Medical Center Göttingen, Göttingen, Germany
- Auditory Neuroscience and Optogenetics Laboratory, German Primate Center, Göttingen, Germany
- Auditory Neuroscience and Synaptic Nanophysiology Group, Max-Planck-Institute for Multidisciplinary Sciences, Göttingen, Germany
- Junior Research Group “Computational Neuroscience and Neuroengineering”, Göttingen, Germany
- The Doctoral Program “Sensory and Motor Neuroscience”, Göttingen Graduate Center for Neurosciences, Biophysics, and Molecular Biosciences (GGNB), Göttingen, Germany
- InnerEarLab, University Medical Center Göttingen, Göttingen, Germany
| | - Tamas Harczos
- Institute for Auditory Neuroscience, University Medical Center Göttingen, Göttingen, Germany
- Auditory Neuroscience and Optogenetics Laboratory, German Primate Center, Göttingen, Germany
| | - Tobias Moser
- Institute for Auditory Neuroscience, University Medical Center Göttingen, Göttingen, Germany
- Auditory Neuroscience and Optogenetics Laboratory, German Primate Center, Göttingen, Germany
- Auditory Neuroscience and Synaptic Nanophysiology Group, Max-Planck-Institute for Multidisciplinary Sciences, Göttingen, Germany
- InnerEarLab, University Medical Center Göttingen, Göttingen, Germany
- Cluster of Excellence “Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells” (MBExC), University of Göttingen, Göttingen, Germany
| | - Lukasz Jablonski
- Institute for Auditory Neuroscience, University Medical Center Göttingen, Göttingen, Germany
- Auditory Neuroscience and Optogenetics Laboratory, German Primate Center, Göttingen, Germany
- Junior Research Group “Computational Neuroscience and Neuroengineering”, Göttingen, Germany
- InnerEarLab, University Medical Center Göttingen, Göttingen, Germany
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11
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Liu Y, Zhang H, Fan C, Liu F, Li S, Li J, Zhao H, Zeng X. Potential role of Bcl2 in lipid metabolism and synaptic dysfunction of age-related hearing loss. Neurobiol Dis 2023; 187:106320. [PMID: 37813166 DOI: 10.1016/j.nbd.2023.106320] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2023] [Revised: 09/25/2023] [Accepted: 10/06/2023] [Indexed: 10/11/2023] Open
Abstract
Age-related hearing loss (ARHL) is a prevalent condition affecting millions of individuals globally. This study investigated the role of the cell survival regulator Bcl2 in ARHL through in vitro and in vivo experiments and metabolomics analysis. The results showed that the lack of Bcl2 in the auditory cortex affects lipid metabolism, resulting in reduced synaptic function and neurodegeneration. Immunohistochemical analysis demonstrated enrichment of Bcl2 in specific areas of the auditory cortex, including the secondary auditory cortex, dorsal and ventral areas, and primary somatosensory cortex. In ARHL rats, a significant decrease in Bcl2 expression was observed in these areas. RNAseq analysis showed that the downregulation of Bcl2 altered lipid metabolism pathways within the auditory pathway, which was further confirmed by metabolomics analysis. These results suggest that Bcl2 plays a crucial role in regulating lipid metabolism, synaptic function, and neurodegeneration in ARHL; thereby, it could be a potential therapeutic target. We also revealed that Bcl2 probably has a close connection with lipid peroxidation and reactive oxygen species (ROS) production occurring in cochlear hair cells and cortical neurons in ARHL. The study also identified changes in hair cells, spiral ganglion cells, and nerve fiber density as consequences of Bcl2 deficiency, which could potentially contribute to the inner ear nerve blockage and subsequent hearing loss. Therefore, targeting Bcl2 may be a promising potential therapeutic intervention for ARHL. These findings provide valuable insights into the molecular mechanisms underlying ARHL and may pave the way for novel treatment approaches for this prevalent age-related disorder.
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Affiliation(s)
- Yue Liu
- Department of Graduate and Scientific Research, Zunyi Medical University Zhuhai Campus, Zhuhai 519041, China; Department of Otolaryngology, Longgang E.N.T Hospital & Shenzhen Key Laboratory of E.N.T, Institute of E.N.T, Shenzhen 518172, China.
| | - Huasong Zhang
- Department of Otolaryngology, Longgang E.N.T Hospital & Shenzhen Key Laboratory of E.N.T, Institute of E.N.T, Shenzhen 518172, China; Department of Otolaryngology, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, 510000, China; Department of Medical Research Center, Sun Yat-sen Memorial Hospital, Sun Yat-sen University; Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Guangzhou, 510000, China.
| | - Cong Fan
- Department of Medical Research Center, Sun Yat-sen Memorial Hospital, Sun Yat-sen University; Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Guangzhou, 510000, China
| | - Feiyi Liu
- Department of Medical Research Center, Sun Yat-sen Memorial Hospital, Sun Yat-sen University; Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Guangzhou, 510000, China
| | - Shaoying Li
- Department of Medical Research Center, Sun Yat-sen Memorial Hospital, Sun Yat-sen University; Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Guangzhou, 510000, China
| | - Juanjuan Li
- Department of Otolaryngology, Longgang E.N.T Hospital & Shenzhen Key Laboratory of E.N.T, Institute of E.N.T, Shenzhen 518172, China
| | - Huiying Zhao
- Department of Medical Research Center, Sun Yat-sen Memorial Hospital, Sun Yat-sen University; Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Guangzhou, 510000, China
| | - Xianhai Zeng
- Department of Graduate and Scientific Research, Zunyi Medical University Zhuhai Campus, Zhuhai 519041, China; Department of Otolaryngology, Longgang E.N.T Hospital & Shenzhen Key Laboratory of E.N.T, Institute of E.N.T, Shenzhen 518172, China.
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12
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Partouche E, Adenis V, Stahl P, Huetz C, Edeline JM. What Is the Benefit of Ramped Pulse Shapes for Activating Auditory Cortex Neurons? An Electrophysiological Study in an Animal Model of Cochlear Implant. Brain Sci 2023; 13:brainsci13020250. [PMID: 36831793 PMCID: PMC9954719 DOI: 10.3390/brainsci13020250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 01/19/2023] [Accepted: 01/30/2023] [Indexed: 02/04/2023] Open
Abstract
In all commercial cochlear implant (CI) devices, the activation of auditory nerve fibers is performed with rectangular pulses that have two phases of opposite polarity. Recently, several papers proposed that ramped pulse shapes could be an alternative shape for efficiently activating auditory nerve fibers. Here, we investigate whether ramped pulse shapes can activate auditory cortex (ACx) neurons in a more efficient way than the classical rectangular pulses. Guinea pigs were implanted with CI devices and responses of ACx neurons were tested with rectangular pulses and with four ramped pulse shapes, with a first-phase being either cathodic or anodic. The thresholds, i.e., the charge level necessary for obtaining significant cortical responses, were almost systematically lower with ramped pulses than with rectangular pulses. The maximal firing rate (FR) elicited by the ramped pulses was higher than with rectangular pulses. As the maximal FR occurred with lower charge levels, the dynamic range (between threshold and the maximal FR) was not modified. These effects were obtained with cathodic and anodic ramped pulses. By reducing the charge levels required to activate ACx neurons, the ramped pulse shapes should reduce charge consumption and should contribute to more battery-efficient CI devices in the future.
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Affiliation(s)
- Elie Partouche
- Jean-Marc Edeline Paris-Saclay Institute of Neurosciences (Neuro-PSI), CNRS UMR 9197, Universite Paris-Saclay, Campus CEA Saclay, Route de la Rotonde Bâtiment 151, 91400 Saclay, France
| | - Victor Adenis
- Jean-Marc Edeline Paris-Saclay Institute of Neurosciences (Neuro-PSI), CNRS UMR 9197, Universite Paris-Saclay, Campus CEA Saclay, Route de la Rotonde Bâtiment 151, 91400 Saclay, France
| | - Pierre Stahl
- Departement of Scientific and Clinical Research, Oticon Medical, 06220 Vallauris, France
| | - Chloé Huetz
- Jean-Marc Edeline Paris-Saclay Institute of Neurosciences (Neuro-PSI), CNRS UMR 9197, Universite Paris-Saclay, Campus CEA Saclay, Route de la Rotonde Bâtiment 151, 91400 Saclay, France
| | - Jean-Marc Edeline
- Jean-Marc Edeline Paris-Saclay Institute of Neurosciences (Neuro-PSI), CNRS UMR 9197, Universite Paris-Saclay, Campus CEA Saclay, Route de la Rotonde Bâtiment 151, 91400 Saclay, France
- Correspondence:
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13
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Mittring A, Moser T, Huet AT. Graded optogenetic activation of the auditory pathway for hearing restoration. Brain Stimul 2023; 16:466-483. [PMID: 36702442 PMCID: PMC10159867 DOI: 10.1016/j.brs.2023.01.1671] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 01/18/2023] [Accepted: 01/19/2023] [Indexed: 01/24/2023] Open
Abstract
Optogenetic control of neural activity enables innovative approaches to improve functional restoration of diseased sensory and motor systems. For clinical translation to succeed, optogenetic stimulation needs to closely match the coding properties of the targeted neuronal population and employ optimally operating emitters. This requires the customization of channelrhodopsins, emitters and coding strategies. Here, we provide a framework to parametrize optogenetic neural control and apply it to the auditory pathway that requires high temporal fidelity of stimulation. We used a viral gene transfer of ultrafast targeting-optimized Chronos into spiral ganglion neurons (SGNs) of the cochlea of mice. We characterized the light-evoked response by in vivo recordings from individual SGNs and neurons of the anteroventral cochlear nucleus (AVCN) that detect coincident SGN inputs. Our recordings from single SGNs demonstrated that their spike probability can be graded by adjusting the duration of light pulses at constant intensity, which optimally serves efficient laser diode operation. We identified an effective pulse width of 1.6 ms to maximize encoding in SGNs at the maximal light intensity employed here (∼35 mW). Alternatively, SGNs were activated at lower energy thresholds using short light pulses (<1 ms). An upper boundary of optical stimulation rates was identified at 316 Hz, inducing a robust spike rate adaptation that required a few tens of milliseconds to recover. We developed a semi-stochastic stimulation paradigm to rapidly (within minutes) estimate the input/output function from light to SGN firing and approximate the time constant of neuronal integration in the AVCN. By that, our data pave the way to design the sound coding strategies of future optical cochlear implants.
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Affiliation(s)
- Artur Mittring
- Auditory Circuit Lab, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany
| | - Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany; Auditory Neuroscience and Optogenetics Laboratory, German Primate Center, Göttingen, Germany; Auditory Neuroscience and Synaptic Nanophysiology Group, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany.
| | - Antoine Tarquin Huet
- Auditory Circuit Lab, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany; Auditory Neuroscience and Optogenetics Laboratory, German Primate Center, Göttingen, Germany.
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14
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James B, Piekarz P, Moya-Díaz J, Lagnado L. The Impact of Multivesicular Release on the Transmission of Sensory Information by Ribbon Synapses. J Neurosci 2022; 42:9401-9414. [PMID: 36344266 PMCID: PMC9794368 DOI: 10.1523/jneurosci.0717-22.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 10/01/2022] [Accepted: 10/06/2022] [Indexed: 11/09/2022] Open
Abstract
The statistics of vesicle release determine how synapses transfer information, but the classical Poisson model of independent release does not always hold at the first stages of vision and hearing. There, ribbon synapses also encode sensory signals as events comprising two or more vesicles released simultaneously. The implications of such coordinated multivesicular release (MVR) for spike generation are not known. Here we investigate how MVR alters the transmission of sensory information compared with Poisson synapses using a pure rate-code. We used leaky integrate-and-fire models incorporating the statistics of release measured experimentally from glutamatergic synapses of retinal bipolar cells in zebrafish (both sexes) and compared these with models assuming Poisson inputs constrained to operate at the same average rates. We find that MVR can increase the number of spikes generated per vesicle while reducing interspike intervals and latency to first spike. The combined effect was to increase the efficiency of information transfer (bits per vesicle) over a range of conditions mimicking target neurons of different size. MVR was most advantageous in neurons with short time constants and reliable synaptic inputs, when less convergence was required to trigger spikes. In the special case of a single input driving a neuron, as occurs in the auditory system of mammals, MVR increased information transfer whenever spike generation required more than one vesicle. This study demonstrates how presynaptic integration of vesicles by MVR can increase the efficiency with which sensory information is transmitted compared with a rate-code described by Poisson statistics.SIGNIFICANCE STATEMENT Neurons communicate by the stochastic release of vesicles at the synapse and the statistics of this process will determine how information is represented by spikes. The classical model is that vesicles are released independently by a Poisson process, but this does not hold at ribbon-type synapses specialized to transmit the first electrical signals in vision and hearing, where two or more vesicles can fuse in a single event by a process termed coordinated multivesicular release. This study shows that multivesicular release can increase the number of spikes generated per vesicle and the efficiency of information transfer (bits per vesicle) over a range of conditions found in the retina and peripheral auditory system.
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Affiliation(s)
- Ben James
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Brighton, BN1 9QG, United Kingdom
| | - Pawel Piekarz
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Brighton, BN1 9QG, United Kingdom
| | - José Moya-Díaz
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Brighton, BN1 9QG, United Kingdom
| | - Leon Lagnado
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Brighton, BN1 9QG, United Kingdom
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15
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Sharma K, Kang KW, Seo YW, Glowatzki E, Yi E. Low-voltage Activating K + Channels in Cochlear Afferent Nerve Fiber Dendrites. Exp Neurobiol 2022; 31:243-259. [PMID: 36050224 PMCID: PMC9471414 DOI: 10.5607/en22013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 06/18/2022] [Accepted: 07/29/2022] [Indexed: 11/19/2022] Open
Abstract
Cochlear afferent nerve fibers (ANF) are the first neurons in the ascending auditory pathway. We investigated the low-voltage activating K+ channels expressed in ANF dendrites using isolated rat cochlear segments. Whole cell patch clamp recordings were made from the dendritic terminals of ANFs. Outward currents activating at membrane potentials as low as -64 mV were observed in all dendrites studied. These currents were inhibited by 4-aminopyridine (4-AP), a blocker known to preferentially inhibit low-voltage activating K+ currents (IKL) in CNS auditory neurons and spiral ganglion neurons. When the dendritic IKL was blocked by 4-AP, the EPSP decay time was significantly prolonged, suggesting that dendritic IKL speeds up the decay of EPSPs and likely modulates action potentials of ANFs. To reveal molecular subtype of dendritic IKL, α-dendrotoxin (α-DTX), a selective inhibitor for Kv1.1, Kv1.2, and Kv1.6 containing channels, was tested. α-DTX inhibited 23±9% of dendritic IKL. To identify the α-DTXsensitive and α-DTX-insensitive components of IKL, immunofluorescence labeling was performed. Strong Kv1.1- and Kv1.2-immunoreactivity was found at unmyelinated dendritic segments, nodes of Ranvier, and cell bodies of most ANFs. A small fraction of ANF dendrites showed Kv7.2- immunoreactivity. These data suggest that dendritic IKL is conducted through Kv1.1and Kv1.2 channels, with a minor contribution from Kv7.2 and other as yet unidentified channels.
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Affiliation(s)
- Kushal Sharma
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, Korea
| | - Kwon Woo Kang
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, Korea
| | - Young-Woo Seo
- KBSI Gwangju Center, Korea Basic Science Institute, Gwangju 61186, Korea
| | - Elisabeth Glowatzki
- Department of Otolaryngology-Head and Neck Surgery and Neuroscience, The Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
| | - Eunyoung Yi
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, Korea
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16
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Ramirez MA, Ninoyu Y, Miller C, Andrade LR, Edassery S, Bomba-Warczak E, Ortega B, Manor U, Rutherford MA, Friedman RA, Savas JN. Cochlear ribbon synapse maturation requires Nlgn1 and Nlgn3. iScience 2022; 25:104803. [PMID: 35992071 PMCID: PMC9386149 DOI: 10.1016/j.isci.2022.104803] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Revised: 05/10/2022] [Accepted: 07/15/2022] [Indexed: 01/13/2023] Open
Abstract
Hearing depends on precise synaptic transmission between cochlear inner hair cells and spiral ganglion neurons through afferent ribbon synapses. Neuroligins (Nlgns) facilitate synapse maturation in the brain, but they have gone unstudied in the cochlea. We report Nlgn3 and Nlgn1 knockout (KO) cochleae have fewer ribbon synapses and have impaired hearing. Nlgn3 KO is more vulnerable to noise trauma with limited activity at high frequencies one day after noise. Furthermore, Nlgn3 KO cochleae have a 5-fold reduction in synapse number compared to wild type after two weeks of recovery. Double KO cochlear phenotypes are more prominent than the KOs, for example, 5-fold smaller synapses, 25% reduction in synapse density, and 30% less synaptic output. These observations indicate Nlgn3 and Nlgn1 are essential to cochlear ribbon synapse maturation and function.
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Affiliation(s)
- Miguel A. Ramirez
- Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Yuzuru Ninoyu
- Division of Otolaryngology, Department of Surgery, University of California, San Diego, 9500 Gilman Drive, Mail Code 0666, La Jolla, CA 92093, USA
| | - Cayla Miller
- Waitt Advanced Biophotonics Core, Salk Institute for Biological Studies, 10010 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | - Leonardo R. Andrade
- Waitt Advanced Biophotonics Core, Salk Institute for Biological Studies, 10010 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | - Seby Edassery
- Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Ewa Bomba-Warczak
- Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Briana Ortega
- Division of Otolaryngology, Department of Surgery, University of California, San Diego, 9500 Gilman Drive, Mail Code 0666, La Jolla, CA 92093, USA
| | - Uri Manor
- Waitt Advanced Biophotonics Core, Salk Institute for Biological Studies, 10010 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | - Mark A. Rutherford
- Department of Otolaryngology, Washington University in St. Louis School of Medicine, St. Louis, MO, USA
| | - Rick A. Friedman
- Division of Otolaryngology, Department of Surgery, University of California, San Diego, 9500 Gilman Drive, Mail Code 0666, La Jolla, CA 92093, USA
| | - Jeffrey N. Savas
- Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
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17
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Qi G, Shi L, Qin H, Jiang Q, Guo W, Yu N, Han D, Yang S. Morphology changes in the cochlea of impulse noise-induced hidden hearing loss. Acta Otolaryngol 2022; 142:455-462. [PMID: 35723705 DOI: 10.1080/00016489.2022.2086706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Abstract
BACKGROUND This study was focused on impulse noise induces hidden hearing loss. OBJECTIVES This study was designed to determine the morphology changes of noise-induced hidden hearing loss (NIHHL). METHOD Fifteen guinea pigs were divided into three groups: noise-induced hidden hearing loss (NIHHL) group, noise-induced hearing loss (NIHL) group, and normal control group. For the NIHHL group, guinea pigs were exposed to 15 times of impulse noise with peak intensity of 163 dB SPL at one time. For the NIHL group, animals were exposed to two rounds of 100 times impulse noise, and the time interval is 24 h. Auditory brain response (ABR) was tested before, immediately, 24 h, one week, and one month after noise exposure to evaluate cochlear physiology changes. One month after noise exposure, all guinea pigs in three groups were sacrificed, and basement membranes were carefully dissected immediately after ABR tests. The cochlea samples were observed by transmission electron microscopy (TEM) to find out the morphology changes. RESULT The ABR results showed that 15 times of impulse noise exposure could cause NIHHL in guinea pigs and 200 times could cause completely hearing loss. Impulse noise exposure could cause a dramatic increase of mitochondria in the inner hair cell. The structures of ribbon synapse and heminode were also obviously impaired compared to the normal group. The nerve fiber and myelin sheath remained intact after impulse noise exposure. CONCLUSION This research revealed that impulse noise could cause hidden hearing loss, and the changes in inner hair cells, ribbon synapse, and heminode all played a vital role in the pathogenesis of hidden hearing loss.
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Affiliation(s)
- Guowei Qi
- Senior Department of Otolaryngology-Head & Neck Surgery, The Sixth Medical Center of PLA General Hospital, National Clinical Research Center for Otolaryngologic Diseases, State Key Lab of Hearing Science, Ministry of Education, Beijing Key Lab of Hearing Impairment Prevention and Treatment Beijing, Beijing, China.,Graduate School of Navy, Medical University Shanghai, Shanghai, China.,Graduate School of Chinese, PLA General Hospital Beijing, Beijing, China
| | - Lei Shi
- Senior Department of Otolaryngology-Head & Neck Surgery, The Sixth Medical Center of PLA General Hospital, National Clinical Research Center for Otolaryngologic Diseases, State Key Lab of Hearing Science, Ministry of Education, Beijing Key Lab of Hearing Impairment Prevention and Treatment Beijing, Beijing, China.,Graduate School of Chinese, PLA General Hospital Beijing, Beijing, China
| | - Handai Qin
- Senior Department of Otolaryngology-Head & Neck Surgery, The Sixth Medical Center of PLA General Hospital, National Clinical Research Center for Otolaryngologic Diseases, State Key Lab of Hearing Science, Ministry of Education, Beijing Key Lab of Hearing Impairment Prevention and Treatment Beijing, Beijing, China.,Graduate School of Chinese, PLA General Hospital Beijing, Beijing, China
| | - Qingqing Jiang
- Senior Department of Otolaryngology-Head & Neck Surgery, The Sixth Medical Center of PLA General Hospital, National Clinical Research Center for Otolaryngologic Diseases, State Key Lab of Hearing Science, Ministry of Education, Beijing Key Lab of Hearing Impairment Prevention and Treatment Beijing, Beijing, China
| | - Weiwei Guo
- Senior Department of Otolaryngology-Head & Neck Surgery, The Sixth Medical Center of PLA General Hospital, National Clinical Research Center for Otolaryngologic Diseases, State Key Lab of Hearing Science, Ministry of Education, Beijing Key Lab of Hearing Impairment Prevention and Treatment Beijing, Beijing, China
| | - Ning Yu
- Senior Department of Otolaryngology-Head & Neck Surgery, The Sixth Medical Center of PLA General Hospital, National Clinical Research Center for Otolaryngologic Diseases, State Key Lab of Hearing Science, Ministry of Education, Beijing Key Lab of Hearing Impairment Prevention and Treatment Beijing, Beijing, China
| | - Dongyi Han
- Senior Department of Otolaryngology-Head & Neck Surgery, The Sixth Medical Center of PLA General Hospital, National Clinical Research Center for Otolaryngologic Diseases, State Key Lab of Hearing Science, Ministry of Education, Beijing Key Lab of Hearing Impairment Prevention and Treatment Beijing, Beijing, China
| | - Shiming Yang
- Senior Department of Otolaryngology-Head & Neck Surgery, The Sixth Medical Center of PLA General Hospital, National Clinical Research Center for Otolaryngologic Diseases, State Key Lab of Hearing Science, Ministry of Education, Beijing Key Lab of Hearing Impairment Prevention and Treatment Beijing, Beijing, China
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18
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Mukhopadhyay M, Pangrsic T. Synaptic transmission at the vestibular hair cells of amniotes. Mol Cell Neurosci 2022; 121:103749. [PMID: 35667549 DOI: 10.1016/j.mcn.2022.103749] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2021] [Revised: 05/09/2022] [Accepted: 06/01/2022] [Indexed: 11/19/2022] Open
Abstract
A harmonized interplay between the central nervous system and the five peripheral end organs is how the vestibular system helps organisms feel a sense of balance and motion in three-dimensional space. The receptor cells of this system, much like their cochlear equivalents, are the specialized hair cells. However, research over the years has shown that the vestibular endorgans and hair cells evolved very differently from their cochlear counterparts. The structurally unique calyceal synapse, which appeared much later in the evolutionary time scale, and continues to intrigue researchers, is now known to support several forms of synaptic neurotransmission. The conventional quantal transmission is believed to employ the ribbon structures, which carry several tethered vesicles filled with neurotransmitters. However, the field of vestibular hair cell synaptic molecular anatomy is still at a nascent stage and needs further work. In this review, we will touch upon the basic structure and function of the peripheral vestibular system, with the focus on the various modes of neurotransmission at the type I vestibular hair cells. We will also shed light on the current knowledge about the molecular anatomy of the vestibular hair cell synapses and vestibular synaptopathy.
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Affiliation(s)
- Mohona Mukhopadhyay
- Experimental Otology Group, InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, and Institute for Auditory Neuroscience, 37075 Göttingen, Germany
| | - Tina Pangrsic
- Experimental Otology Group, InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, and Institute for Auditory Neuroscience, 37075 Göttingen, Germany; Auditory Neuroscience Group, Max Planck Institute for Multidisciplinary Sciences, 37075 Göttingen, Germany; Collaborative Research Center 889, University of Göttingen, Göttingen, Germany; Multiscale Bioimaging Cluster of Excellence (MBExC), University of Göttingen, 37075 Göttingen, Germany.
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19
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Sadeghi SG, Géléoc GSG. Editorial: Commonalities and Differences in Vestibular and Auditory Pathways. Front Neurosci 2022; 16:876798. [PMID: 35401079 PMCID: PMC8984178 DOI: 10.3389/fnins.2022.876798] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 02/24/2022] [Indexed: 11/13/2022] Open
Affiliation(s)
- Soroush G. Sadeghi
- Center for Hearing and Deafness, Department of Communicative Disorders and Science, University at Buffalo, Buffalo, NY, United States
- *Correspondence: Soroush G. Sadeghi
| | - Gwenaëlle S. G. Géléoc
- Boston Children's Hospital and Harvard Medical School, Boston, MA, United States
- Gwenaëlle S. G. Géléoc
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20
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Chakrabarti R, Jaime Tobón LM, Slitin L, Redondo Canales M, Hoch G, Slashcheva M, Fritsch E, Bodensiek K, Özçete ÖD, Gültas M, Michanski S, Opazo F, Neef J, Pangrsic T, Moser T, Wichmann C. Optogenetics and electron tomography for structure-function analysis of cochlear ribbon synapses. eLife 2022; 11:79494. [PMID: 36562477 PMCID: PMC9908081 DOI: 10.7554/elife.79494] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Accepted: 11/28/2022] [Indexed: 12/24/2022] Open
Abstract
Ribbon synapses of cochlear inner hair cells (IHCs) are specialized to indefatigably transmit sound information at high rates. To understand the underlying mechanisms, structure-function analysis of the active zone (AZ) of these synapses is essential. Previous electron microscopy studies of synaptic vesicle (SV) dynamics at the IHC AZ used potassium stimulation, which limited the temporal resolution to minutes. Here, we established optogenetic IHC stimulation followed by quick freezing within milliseconds and electron tomography to study the ultrastructure of functional synapse states with good temporal resolution in mice. We characterized optogenetic IHC stimulation by patch-clamp recordings from IHCs and postsynaptic boutons revealing robust IHC depolarization and neurotransmitter release. Ultrastructurally, the number of docked SVs increased upon short (17-25 ms) and long (48-76 ms) light stimulation paradigms. We did not observe enlarged SVs or other morphological correlates of homotypic fusion events. Our results indicate a rapid recruitment of SVs to the docked state upon stimulation and suggest that univesicular release prevails as the quantal mechanism of exocytosis at IHC ribbon synapses.
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Affiliation(s)
- Rituparna Chakrabarti
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany,Center for Biostructural Imaging of Neurodegeneration, University Medical Center GöttingenGöttingenGermany,Collaborative Research Center 889 "Cellular Mechanisms of Sensory Processing"GöttingenGermany
| | - Lina María Jaime Tobón
- Collaborative Research Center 889 "Cellular Mechanisms of Sensory Processing"GöttingenGermany,Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany,Auditory Neuroscience & Synaptic Nanophysiology Group, Max Planck Institute for Multidisciplinary SciencesGöttingenGermany
| | - Loujin Slitin
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany,Center for Biostructural Imaging of Neurodegeneration, University Medical Center GöttingenGöttingenGermany,Collaborative Research Center 889 "Cellular Mechanisms of Sensory Processing"GöttingenGermany
| | - Magdalena Redondo Canales
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany,Center for Biostructural Imaging of Neurodegeneration, University Medical Center GöttingenGöttingenGermany,Collaborative Research Center 889 "Cellular Mechanisms of Sensory Processing"GöttingenGermany
| | - Gerhard Hoch
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany,Auditory Neuroscience & Synaptic Nanophysiology Group, Max Planck Institute for Multidisciplinary SciencesGöttingenGermany
| | - Marina Slashcheva
- Göttingen Graduate School for Neuroscience and Molecular Biosciences, University of GöttingenGöttingenGermany
| | - Elisabeth Fritsch
- Göttingen Graduate School for Neuroscience and Molecular Biosciences, University of GöttingenGöttingenGermany
| | - Kai Bodensiek
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany
| | - Özge Demet Özçete
- Collaborative Research Center 889 "Cellular Mechanisms of Sensory Processing"GöttingenGermany,Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany,Auditory Neuroscience & Synaptic Nanophysiology Group, Max Planck Institute for Multidisciplinary SciencesGöttingenGermany
| | - Mehmet Gültas
- Faculty of Agriculture, South Westphalia University of Applied SciencesSoestGermany
| | - Susann Michanski
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany,Center for Biostructural Imaging of Neurodegeneration, University Medical Center GöttingenGöttingenGermany,Collaborative Research Center 889 "Cellular Mechanisms of Sensory Processing"GöttingenGermany
| | - Felipe Opazo
- Center for Biostructural Imaging of Neurodegeneration, University Medical Center GöttingenGöttingenGermany,NanoTag Biotechnologies GmbHGöttingenGermany,Institute of Neuro- and Sensory Physiology, University Medical Center GöttingenGöttingenGermany
| | - Jakob Neef
- Collaborative Research Center 889 "Cellular Mechanisms of Sensory Processing"GöttingenGermany,Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany,Auditory Neuroscience & Synaptic Nanophysiology Group, Max Planck Institute for Multidisciplinary SciencesGöttingenGermany
| | - Tina Pangrsic
- Collaborative Research Center 889 "Cellular Mechanisms of Sensory Processing"GöttingenGermany,Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany,Auditory Neuroscience & Synaptic Nanophysiology Group, Max Planck Institute for Multidisciplinary SciencesGöttingenGermany,Multiscale Bioimaging: from Molecular Machines to Networks of Excitable CellsGöttingenGermany,Synaptic Physiology of Mammalian Vestibular Hair Cells Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany
| | - Tobias Moser
- Collaborative Research Center 889 "Cellular Mechanisms of Sensory Processing"GöttingenGermany,Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany,Auditory Neuroscience & Synaptic Nanophysiology Group, Max Planck Institute for Multidisciplinary SciencesGöttingenGermany,Multiscale Bioimaging: from Molecular Machines to Networks of Excitable CellsGöttingenGermany
| | - Carolin Wichmann
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany,Center for Biostructural Imaging of Neurodegeneration, University Medical Center GöttingenGöttingenGermany,Collaborative Research Center 889 "Cellular Mechanisms of Sensory Processing"GöttingenGermany,Multiscale Bioimaging: from Molecular Machines to Networks of Excitable CellsGöttingenGermany
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21
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Panganiban CH, Barth JL, Tan J, Noble KV, McClaskey CM, Howard BA, Jafri SH, Dias JW, Harris KC, Lang H. Two distinct types of nodes of Ranvier support auditory nerve function in the mouse cochlea. Glia 2021; 70:768-791. [DOI: 10.1002/glia.24138] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2021] [Revised: 11/12/2021] [Accepted: 12/17/2021] [Indexed: 11/09/2022]
Affiliation(s)
- Clarisse H. Panganiban
- Department of Pathology and Laboratory Medicine Medical University of South Carolina Charleston South Carolina USA
- Wolfson Centre for Age‐Related Diseases King's College London London UK
| | - Jeremy L. Barth
- Department of Regenerative Medicine and Cell Biology Medical University of South Carolina Charleston South Carolina USA
| | - Junying Tan
- Department of Pathology and Laboratory Medicine Medical University of South Carolina Charleston South Carolina USA
| | - Kenyaria V. Noble
- Department of Pathology and Laboratory Medicine Medical University of South Carolina Charleston South Carolina USA
| | - Carolyn M. McClaskey
- Department of Otolaryngology & Head and Neck Surgery Medical University of South Carolina Charleston South Carolina USA
| | - Blake A. Howard
- Department of Pathology and Laboratory Medicine Medical University of South Carolina Charleston South Carolina USA
| | - Shabih H. Jafri
- Department of Pathology and Laboratory Medicine Medical University of South Carolina Charleston South Carolina USA
| | - James W. Dias
- Department of Otolaryngology & Head and Neck Surgery Medical University of South Carolina Charleston South Carolina USA
| | - Kelly C. Harris
- Department of Otolaryngology & Head and Neck Surgery Medical University of South Carolina Charleston South Carolina USA
| | - Hainan Lang
- Department of Pathology and Laboratory Medicine Medical University of South Carolina Charleston South Carolina USA
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22
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Navntoft CA, Landsberger DM, Barkat TR, Marozeau J. The Perception of Ramped Pulse Shapes in Cochlear Implant Users. Trends Hear 2021; 25:23312165211061116. [PMID: 34935552 PMCID: PMC8724057 DOI: 10.1177/23312165211061116] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The electric stimulation provided by current cochlear implants (CI) is not power
efficient. One underlying problem is the poor efficiency by which information
from electric pulses is transformed into auditory nerve responses. A novel
stimulation paradigm using ramped pulse shapes has recently been proposed to
remedy this inefficiency. The primary motivation is a better biophysical fit to
spiral ganglion neurons with ramped pulses compared to the rectangular pulses
used in most contemporary CIs. Here, we tested the hypotheses that ramped pulses
provide more efficient stimulation compared to rectangular pulses and that a
rising ramp is more efficient than a declining ramp. Rectangular, rising ramped
and declining ramped pulse shapes were compared in terms of charge efficiency
and discriminability, and threshold variability in seven CI listeners. The tasks
included single-channel threshold detection, loudness-balancing, discrimination
of pulse shapes, and threshold measurement across the electrode array. Results
showed that reduced charge, but increased peak current amplitudes, was required
at threshold and most comfortable levels with ramped pulses relative to
rectangular pulses. Furthermore, only one subject could reliably discriminate
between equally-loud ramped and rectangular pulses, suggesting variations in
neural activation patterns between pulse shapes in that participant. No
significant difference was found between rising and declining ramped pulses
across all tests. In summary, the present findings show some benefits of charge
efficiency with ramped pulses relative to rectangular pulses, that the direction
of a ramped slope is of less importance, and that most participants could not
perceive a difference between pulse shapes.
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Affiliation(s)
- Charlotte Amalie Navntoft
- Hearing Systems Group, Department of Health Technology, 5205Technical University of Denmark, Kgs. Lyngby, Denmark.,Brain and Sound Lab, Department of Biomedicine, 27209Basel University, Basel, Switzerland
| | - David M Landsberger
- Department of Otolaryngology, 12296New York University School of Medicine, New York, USA
| | - Tania Rinaldi Barkat
- Brain and Sound Lab, Department of Biomedicine, 27209Basel University, Basel, Switzerland
| | - Jeremy Marozeau
- Hearing Systems Group, Department of Health Technology, 5205Technical University of Denmark, Kgs. Lyngby, Denmark
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23
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Suthakar K, Liberman MC. Auditory-nerve responses in mice with noise-induced cochlear synaptopathy. J Neurophysiol 2021; 126:2027-2038. [PMID: 34788179 DOI: 10.1152/jn.00342.2021] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Cochlear synaptopathy is the noise-induced or age-related loss of ribbon synapses between inner hair cells (IHCs) and auditory-nerve fibers (ANFs), first reported in CBA/CaJ mice. Recordings from single ANFs in anesthetized, noise-exposed guinea pigs suggested that neurons with low spontaneous rates (SRs) and high thresholds are more vulnerable than low-threshold, high-SR fibers. However, there is extensive postexposure regeneration of ANFs in guinea pigs but not in mice. Here, we exposed CBA/CaJ mice to octave-band noise and recorded sound-evoked and spontaneous activity from single ANFs at least 2 wk later. Confocal analysis of cochleae immunostained for pre- and postsynaptic markers confirmed the expected loss of 40%-50% of ANF synapses in the basal half of the cochlea; however, our data were not consistent with a selective loss of low-SR fibers. Rather they suggested a loss of both SR groups in synaptopathic regions. Single-fiber thresholds and frequency tuning recovered to pre-exposure levels; however, response to tone bursts showed increased peak and steady-state firing rates, as well as decreased jitter in first-spike latencies. This apparent gain-of-function increased the robustness of tone-burst responses in the presence of continuous masking noise. This study suggests that the nature of noise-induced synaptic damage varies between different species and that, in mouse, the noise-induced hyperexcitability seen in central auditory circuits is also observed at the level of the auditory nerve.NEW & NOTEWORTHY Noise-induced damage to synapses between inner hair cells and auditory-nerve fibers (ANFs) can occur without permanent hair cell damage, resulting in pathophysiology that "hides" behind normal thresholds. Prior single-fiber neurophysiology in guinea pig suggested that noise selectively targets high-threshold ANFs. Here, we show that the lingering pathophysiology differs in mouse, with both ANF groups affected and a paradoxical gain-of-function in surviving low-threshold fibers, including increased onset rate, decreased onset jitter, and reduced maskability.
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Affiliation(s)
- Kirupa Suthakar
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, Massachusetts.,Department of Otolaryngology Head and Neck Surgery, Harvard Medical School, Boston, Massachusetts
| | - M Charles Liberman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, Massachusetts.,Department of Otolaryngology Head and Neck Surgery, Harvard Medical School, Boston, Massachusetts
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24
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Shuster B, Casserly R, Lipford E, Olszewski R, Milon B, Viechweg S, Davidson K, Enoch J, McMurray M, Rutherford MA, Ohlemiller KK, Hoa M, Depireux DA, Mong JA, Hertzano R. Estradiol Protects against Noise-Induced Hearing Loss and Modulates Auditory Physiology in Female Mice. Int J Mol Sci 2021; 22:12208. [PMID: 34830090 PMCID: PMC8620009 DOI: 10.3390/ijms222212208] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 11/05/2021] [Accepted: 11/08/2021] [Indexed: 12/13/2022] Open
Abstract
Recent studies have identified sex-differences in auditory physiology and in the susceptibility to noise-induced hearing loss (NIHL). We hypothesize that 17β-estradiol (E2), a known modulator of auditory physiology, may underpin sex-differences in the response to noise trauma. Here, we gonadectomized B6CBAF1/J mice and used a combination of electrophysiological and histological techniques to study the effects of estrogen replacement on peripheral auditory physiology in the absence of noise exposure and on protection from NIHL. Functional analysis of auditory physiology in gonadectomized female mice revealed that E2-treatment modulated the peripheral response to sound in the absence of changes to the endocochlear potential compared to vehicle-treatment. E2-replacement in gonadectomized female mice protected against hearing loss following permanent threshold shift (PTS)- and temporary threshold shift (TTS)-inducing noise exposures. Histological analysis of the cochlear tissue revealed that E2-replacement mitigated outer hair cell loss and cochlear synaptopathy following noise exposure compared to vehicle-treatment. Lastly, using fluorescent in situ hybridization, we demonstrate co-localization of estrogen receptor-2 with type-1C, high threshold spiral ganglion neurons, suggesting that the observed protection from cochlear synaptopathy may occur through E2-mediated preservation of these neurons. Taken together, these data indicate the estrogen signaling pathways may be harnessed for the prevention and treatment of NIHL.
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Affiliation(s)
- Benjamin Shuster
- Department of Otorhinolaryngology—Head and Neck Surgery, University of Maryland School of Medicine, Baltimore, MD 21201, USA; (B.S.); (R.C.); (E.L.); (B.M.); (M.M.)
| | - Ryan Casserly
- Department of Otorhinolaryngology—Head and Neck Surgery, University of Maryland School of Medicine, Baltimore, MD 21201, USA; (B.S.); (R.C.); (E.L.); (B.M.); (M.M.)
| | - Erika Lipford
- Department of Otorhinolaryngology—Head and Neck Surgery, University of Maryland School of Medicine, Baltimore, MD 21201, USA; (B.S.); (R.C.); (E.L.); (B.M.); (M.M.)
| | - Rafal Olszewski
- Auditory Development and Restoration Program, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD 20892, USA; (R.O.); (M.H.)
| | - Béatrice Milon
- Department of Otorhinolaryngology—Head and Neck Surgery, University of Maryland School of Medicine, Baltimore, MD 21201, USA; (B.S.); (R.C.); (E.L.); (B.M.); (M.M.)
| | - Shaun Viechweg
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; (S.V.); (K.D.); (J.E.); (J.A.M.)
| | - Kanisa Davidson
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; (S.V.); (K.D.); (J.E.); (J.A.M.)
| | - Jennifer Enoch
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; (S.V.); (K.D.); (J.E.); (J.A.M.)
| | - Mark McMurray
- Department of Otorhinolaryngology—Head and Neck Surgery, University of Maryland School of Medicine, Baltimore, MD 21201, USA; (B.S.); (R.C.); (E.L.); (B.M.); (M.M.)
| | - Mark A. Rutherford
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO 63110, USA; (M.A.R.); (K.K.O.)
| | - Kevin K. Ohlemiller
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO 63110, USA; (M.A.R.); (K.K.O.)
| | - Michael Hoa
- Auditory Development and Restoration Program, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD 20892, USA; (R.O.); (M.H.)
| | | | - Jessica A. Mong
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; (S.V.); (K.D.); (J.E.); (J.A.M.)
| | - Ronna Hertzano
- Department of Otorhinolaryngology—Head and Neck Surgery, University of Maryland School of Medicine, Baltimore, MD 21201, USA; (B.S.); (R.C.); (E.L.); (B.M.); (M.M.)
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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25
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Liu W, Liu Q, Crozier RA, Davis RL. Analog Transmission of Action Potential Fine Structure in Spiral Ganglion Axons. J Neurophysiol 2021; 126:888-905. [PMID: 34346782 DOI: 10.1152/jn.00237.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Action potential waveforms generated at the axon initial segment (AIS) are specialized between and within neuronal classes. But is the fine structure of each electrical event retained when transmitted along myelinated axons or is it rapidly and uniformly transmitted to be modified again at the axon terminal? To address this issue action potential axonal transmission was evaluated in a class of primary sensory afferents that possess numerous types of voltage-gated ion channels underlying a complex repertoire of endogenous firing patterns. In addition to their signature intrinsic electrophysiological heterogeneity, spiral ganglion neurons are uniquely designed. The bipolar, myelinated somata of type I neurons are located within the conduction pathway, requiring that action potentials generated at the first heminode must be conducted through their electrically excitable membrane. We utilized this unusual axonal-like morphology to serve as a window into action potential transmission to compare locally-evoked action potential profiles to those generated peripherally at their glutamatergic synaptic connections with hair cell receptors. These comparisons showed that the distinctively-shaped somatic action potentials were highly correlated with the nodally-generated, invading ones for each neuron. This result indicates that the fine structure of the action potential waveform is maintained axonally, thus supporting the concept that analog signaling is incorporated into each digitally-transmitted action potential in the specialized primary auditory afferents.
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Affiliation(s)
- Wenke Liu
- Department of Cell Biology and Neuroscience, Rutgers, The State University of New Jersey, Piscataway, NJ, United States.,Institute for System Genetics, New York University School of Medicine, New York, NY, United States
| | - Qing Liu
- Department of Cell Biology and Neuroscience, Rutgers, The State University of New Jersey, Piscataway, NJ, United States.,Inscopix, Inc., Palo Alto, California, United States
| | - Robert A Crozier
- Department of Cell Biology and Neuroscience, Rutgers, The State University of New Jersey, Piscataway, NJ, United States.,Synergy Pharmaceuticals Inc., New York, NY, United States
| | - Robin L Davis
- Department of Cell Biology and Neuroscience, Rutgers, The State University of New Jersey, Piscataway, NJ, United States
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26
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Walia A, Lee C, Hartsock J, Goodman SS, Dolle R, Salt AN, Lichtenhan JT, Rutherford MA. Reducing Auditory Nerve Excitability by Acute Antagonism of Ca 2+-Permeable AMPA Receptors. Front Synaptic Neurosci 2021; 13:680621. [PMID: 34290596 PMCID: PMC8287724 DOI: 10.3389/fnsyn.2021.680621] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 05/31/2021] [Indexed: 11/13/2022] Open
Abstract
Hearing depends on glutamatergic synaptic transmission mediated by α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs). AMPARs are tetramers, where inclusion of the GluA2 subunit reduces overall channel conductance and Ca2+ permeability. Cochlear afferent synapses between inner hair cells (IHCs) and auditory nerve fibers (ANFs) contain the AMPAR subunits GluA2, 3, and 4. However, the tetrameric complement of cochlear AMPAR subunits is not known. It was recently shown in mice that chronic intracochlear delivery of IEM-1460, an antagonist selective for GluA2-lacking AMPARs [also known as Ca2+-permeable AMPARs (CP-AMPARs)], before, during, and after acoustic overexposure prevented both the trauma to ANF synapses and the ensuing reduction of cochlear nerve activity in response to sound. Surprisingly, baseline measurements of cochlear function before exposure were unaffected by chronic intracochlear delivery of IEM-1460. This suggested that cochlear afferent synapses contain GluA2-lacking CP-AMPARs alongside GluA2-containing Ca2+-impermeable AMPA receptors (CI-AMPARs), and that the former can be antagonized for protection while the latter remain conductive. Here, we investigated hearing function in the guinea pig during acute local or systemic delivery of CP-AMPAR antagonists. Acute intracochlear delivery of IEM-1460 or systemic delivery of IEM-1460 or IEM-1925 reduced the amplitude of the ANF compound action potential (CAP) significantly, for all tone levels and frequencies, by > 50% without affecting CAP thresholds or distortion product otoacoustic emissions (DPOAE). Following systemic dosing, IEM-1460 levels in cochlear perilymph were ~ 30% of blood levels, on average, consistent with pharmacokinetic properties predicting permeation of the compounds into the brain and ear. Both compounds were metabolically stable with half-lives >5 h in vitro, and elimination half-lives in vivo of 118 min (IEM-1460) and 68 min (IEM-1925). Heart rate monitoring and off-target binding assays suggest an enhanced safety profile for IEM-1925 over IEM-1460. Compound potency on CAP reduction (IC50 ~ 73 μM IEM-1460) was consistent with a mixture of GluA2-lacking and GluA2-containing AMPARs. These data strongly imply that cochlear afferent synapses of the guinea pig contain GluA2-lacking CP-AMPARs. We propose these CP-AMPARs may be acutely antagonized with systemic dosing, to protect from glutamate excitotoxicity, while transmission at GluA2-containing AMPARs persists to mediate hearing during the protection.
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Affiliation(s)
- Amit Walia
- Department of Otolaryngology, Washington University in St. Louis School of Medicine, St. Louis, MO, United States
| | - Choongheon Lee
- Department of Otolaryngology, Washington University in St. Louis School of Medicine, St. Louis, MO, United States
| | - Jared Hartsock
- Department of Otolaryngology, Washington University in St. Louis School of Medicine, St. Louis, MO, United States
| | - Shawn S Goodman
- Department of Communication Sciences and Disorders, University of Iowa, Iowa City, IA, United States
| | - Roland Dolle
- Department of Biochemistry and Molecular Biophysics, Washington University Center for Drug Discovery, Washington University in St. Louis School of Medicine, St. Louis, MO, United States
| | - Alec N Salt
- Department of Otolaryngology, Washington University in St. Louis School of Medicine, St. Louis, MO, United States
| | - Jeffery T Lichtenhan
- Department of Otolaryngology, Washington University in St. Louis School of Medicine, St. Louis, MO, United States
| | - Mark A Rutherford
- Department of Otolaryngology, Washington University in St. Louis School of Medicine, St. Louis, MO, United States
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27
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Kohrman D, Borges BC, Cassinotti L, Ji L, Corfas G. Axon-glia interactions in the ascending auditory system. Dev Neurobiol 2021; 81:546-567. [PMID: 33561889 PMCID: PMC9004231 DOI: 10.1002/dneu.22813] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 11/25/2020] [Accepted: 02/05/2021] [Indexed: 11/09/2022]
Abstract
The auditory system detects and encodes sound information with high precision to provide a high-fidelity representation of the environment and communication. In mammals, detection occurs in the peripheral sensory organ (the cochlea) containing specialized mechanosensory cells (hair cells) that initiate the conversion of sound-generated vibrations into action potentials in the auditory nerve. Neural activity in the auditory nerve encodes information regarding the intensity and frequency of sound stimuli, which is transmitted to the auditory cortex through the ascending neural pathways. Glial cells are critical for precise control of neural conduction and synaptic transmission throughout the pathway, allowing for the precise detection of the timing, frequency, and intensity of sound signals, including the sub-millisecond temporal fidelity is necessary for tasks such as sound localization, and in humans, for processing complex sounds including speech and music. In this review, we focus on glia and glia-like cells that interact with hair cells and neurons in the ascending auditory pathway and contribute to the development, maintenance, and modulation of neural circuits and transmission in the auditory system. We also discuss the molecular mechanisms of these interactions, their impact on hearing and on auditory dysfunction associated with pathologies of each cell type.
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Affiliation(s)
- David Kohrman
- Kresge Hearing Research Institute and Department of Otolaryngology - Head and Neck Surgery, University of Michigan, 1150 West. Medical Center Dr., Ann Arbor, MI 48109, USA
| | - Beatriz C. Borges
- Kresge Hearing Research Institute and Department of Otolaryngology - Head and Neck Surgery, University of Michigan, 1150 West. Medical Center Dr., Ann Arbor, MI 48109, USA
| | - Luis Cassinotti
- Kresge Hearing Research Institute and Department of Otolaryngology - Head and Neck Surgery, University of Michigan, 1150 West. Medical Center Dr., Ann Arbor, MI 48109, USA
| | - Lingchao Ji
- Kresge Hearing Research Institute and Department of Otolaryngology - Head and Neck Surgery, University of Michigan, 1150 West. Medical Center Dr., Ann Arbor, MI 48109, USA
| | - Gabriel Corfas
- Kresge Hearing Research Institute and Department of Otolaryngology - Head and Neck Surgery, University of Michigan, 1150 West. Medical Center Dr., Ann Arbor, MI 48109, USA
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28
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Peterson AJ, Heil P. A simplified physiological model of rate-level functions of auditory-nerve fibers. Hear Res 2021; 406:108258. [PMID: 34010767 DOI: 10.1016/j.heares.2021.108258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 03/09/2021] [Accepted: 04/23/2021] [Indexed: 12/24/2022]
Abstract
Several approaches have been used to describe the rate-level functions of auditory-nerve fibers (ANFs). One approach uses descriptive models that can be fitted easily to data. Another derives rate-level functions from comprehensive physiological models of auditory peripheral processing. Here, we seek to identify the minimal set of components needed to provide a physiologically plausible account of rate-level functions. Our model consists of a first-order Boltzmann mechanoelectrical transducer function relating the instantaneous stimulus pressure to an instantaneous output, followed by a lowpass filter that eliminates the AC component, followed by an exponential synaptic transfer function relating the DC component to the mean spike rate. This is perhaps the simplest physiologically plausible model capable of accounting for rate-level functions under the assumption that the model parameters for a given ANF and stimulus frequency are level-independent. We find that the model typically accounts well for rate-level functions from cat ANFs for all stimulus frequencies. More complicated model variants having saturating synaptic transfer functions do not perform significantly better, implying the system operates far away from synaptic saturation. Rate saturation in the model is caused by saturation of the DC component of the filter output (e.g., the receptor potential), which in turn is due to the saturation of the transducer function. The maximum mean spike rate is approximately constant across ANFs, such that the slope parameter of the exponential synaptic transfer function decreases with increasing spontaneous rate. If the synaptic parameters for a given ANF are assumed to be constant across stimulus frequencies, then frequency- and level-dependent input nonlinearities are derived that are qualitatively similar to those reported in the literature. Contrary to assumptions in the literature, such nonlinearities are obtained even for ANFs having high spontaneous rates. Finally, spike-rate adaptation is examined and found to be accounted for by a decrease in the slope parameter of the synaptic transfer function over time following stimulus onset.
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Affiliation(s)
- Adam J Peterson
- Department of Systems Physiology of Learning, Leibniz Institute for Neurobiology, Magdeburg, Germany
| | - Peter Heil
- Department of Systems Physiology of Learning, Leibniz Institute for Neurobiology, Magdeburg, Germany; Center for Behavioral Brain Sciences, Magdeburg, Germany.
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29
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Payne SA, Joens MS, Chung H, Skigen N, Frank A, Gattani S, Vaughn K, Schwed A, Nester M, Bhattacharyya A, Iyer G, Davis B, Carlquist J, Patel H, Fitzpatrick JAJ, Rutherford MA. Maturation of Heterogeneity in Afferent Synapse Ultrastructure in the Mouse Cochlea. Front Synaptic Neurosci 2021; 13:678575. [PMID: 34220482 PMCID: PMC8248813 DOI: 10.3389/fnsyn.2021.678575] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 05/11/2021] [Indexed: 12/11/2022] Open
Abstract
Auditory nerve fibers (ANFs) innervating the same inner hair cell (IHC) may have identical frequency tuning but different sound response properties. In cat and guinea pig, ANF response properties correlate with afferent synapse morphology and position on the IHC, suggesting a causal structure-function relationship. In mice, this relationship has not been fully characterized. Here we measured the emergence of synaptic morphological heterogeneities during maturation of the C57BL/6J mouse cochlea by comparing postnatal day 17 (p17, ∼3 days after hearing onset) with p34, when the mouse cochlea is mature. Using serial block face scanning electron microscopy and three-dimensional reconstruction we measured the size, shape, vesicle content, and position of 70 ribbon synapses from the mid-cochlea. Several features matured over late postnatal development. From p17 to p34, presynaptic densities (PDs) and post-synaptic densities (PSDs) became smaller on average (PDs: 0.75 to 0.33; PSDs: 0.58 to 0.31 μm2) and less round as their short axes shortened predominantly on the modiolar side, from 770 to 360 nm. Membrane-associated synaptic vesicles decreased in number from 53 to 30 per synapse from p17 to p34. Anatomical coupling, measured as PSD to ribbon distance, tightened predominantly on the pillar side. Ribbons became less spherical as long-axes lengthened only on the modiolar side of the IHC, from 372 to 541 nm. A decreasing gradient of synaptic ribbon size along the modiolar-pillar axis was detected only at p34 after aligning synapses of adjacent IHCs to a common reference frame (median volumes in nm3 × 106: modiolar 4.87; pillar 2.38). The number of ribbon-associated synaptic vesicles scaled with ribbon size (range 67 to 346 per synapse at p34), thus acquiring a modiolar-pillar gradient at p34, but overall medians were similar at p17 (120) and p34 (127), like ribbon surface area (0.36 vs. 0.34 μm2). PD and PSD morphologies were tightly correlated to each other at individual synapses, more so at p34 than p17, but not to ribbon morphology. These observations suggest that PDs and PSDs mature according to different cues than ribbons, and that ribbon size may be more influenced by cues from the IHC than the surrounding tissue.
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Affiliation(s)
- Shelby A. Payne
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO, United States
| | - Matthew S. Joens
- Center for Cellular Imaging, Washington University in St. Louis, St. Louis, MO, United States
- TESCAN USA, Inc., Warrendale, PA, United States
| | - Heather Chung
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO, United States
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Natalie Skigen
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Adam Frank
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Sonali Gattani
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Kya Vaughn
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Allison Schwed
- Graduate Program in Audiology and Communications Sciences, Washington University School of Medicine, St. Louis, MO, United States
| | - Matt Nester
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Atri Bhattacharyya
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO, United States
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Guhan Iyer
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Bethany Davis
- Graduate Program in Audiology and Communications Sciences, Washington University School of Medicine, St. Louis, MO, United States
| | - Jason Carlquist
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO, United States
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Honey Patel
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - James A. J. Fitzpatrick
- Center for Cellular Imaging, Washington University in St. Louis, St. Louis, MO, United States
- Department of Neuroscience, Washington University School of Medicine, St. Louis, MO, United States
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, United States
- Department of Biomedical Engineering, Washington University School of Medicine, St. Louis, MO, United States
| | - Mark A. Rutherford
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO, United States
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30
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Kitcher SR, Pederson AM, Weisz CJC. Diverse identities and sites of action of cochlear neurotransmitters. Hear Res 2021; 419:108278. [PMID: 34108087 DOI: 10.1016/j.heares.2021.108278] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 04/30/2021] [Accepted: 05/18/2021] [Indexed: 11/18/2022]
Abstract
Accurate encoding of acoustic stimuli requires temporally precise responses to sound integrated with cellular mechanisms that encode the complexity of stimuli over varying timescales and orders of magnitude of intensity. Sound in mammals is initially encoded in the cochlea, the peripheral hearing organ, which contains functionally specialized cells (including hair cells, afferent and efferent neurons, and a multitude of supporting cells) to allow faithful acoustic perception. To accomplish the demanding physiological requirements of hearing, the cochlea has developed synaptic arrangements that operate over different timescales, with varied strengths, and with the ability to adjust function in dynamic hearing conditions. Multiple neurotransmitters interact to support the precision and complexity of hearing. Here, we review the location of release, action, and function of neurotransmitters in the mammalian cochlea with an emphasis on recent work describing the complexity of signaling.
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Affiliation(s)
- Siân R Kitcher
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD 20892, United States
| | - Alia M Pederson
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD 20892, United States
| | - Catherine J C Weisz
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD 20892, United States.
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Young ED, Wu 武靜靜 JS, Niwa M, Glowatzki E. Resolution of subcomponents of synaptic release from postsynaptic currents in rat hair-cell/auditory-nerve fiber synapses. J Neurophysiol 2021; 125:2444-2460. [PMID: 33949889 DOI: 10.1152/jn.00450.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The synapse between inner hair cells and auditory nerve fiber dendrites shows large excitatory postsynaptic currents (EPSCs), which are either monophasic or multiphasic. Multiquantal or uniquantal (flickering) release of neurotransmitter has been proposed to underlie the unusual multiphasic waveforms. Here the nature of multiphasic waveforms is analyzed using EPSCs recorded in vitro in rat afferent dendrites. Spontaneous EPSCs were deconvolved into a sum of presumed release events having monophasic EPSC waveforms. Results include, first, the charge of EPSCs is about the same for multiphasic versus monophasic EPSCs. Second, EPSC amplitudes decline with the number of release events per EPSC. Third, there is no evidence of a mini-EPSC. Most results can be accounted for by versions of either uniquantal or multiquantal release. However, serial neurotransmitter release in multiphasic EPSCs shows properties that are not fully explained by either model, especially that the amplitudes of individual release events are established at the beginning of a multiphasic EPSC, constraining possible models of vesicle release.NEW & NOTEWORTHY How do monophasic and multiphasic waveshapes arise in auditory-nerve dendrites; mainly are they uniquantal, arising from release of a single vesicle, or multiquantal, requiring several vesicles? The charge injected by excitatory postsynaptic currents (EPSCs) is the same for monophasic or multiphasic EPSCs, supporting uniquantal release. Serial adaptation of responses to sequential EPSCs favors a multiquantal model. Finally, neurotransmitter partitioning into similar sized release boluses occurs at the first bolus in the EPSC, not easily explained with either model.
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Affiliation(s)
- Eric D Young
- Center for Hearing and Balance, Johns Hopkins School of Medicine, Baltimore, Maryland.,Department of Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore, Maryland.,Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins School of Medicine, Baltimore, Maryland.,Department of Neuroscience, Johns Hopkins School of Medicine, Baltimore, Maryland
| | - Jingjing Sherry Wu 武靜靜
- Center for Hearing and Balance, Johns Hopkins School of Medicine, Baltimore, Maryland.,Department of Neuroscience, Johns Hopkins School of Medicine, Baltimore, Maryland
| | - Mamiko Niwa
- Center for Hearing and Balance, Johns Hopkins School of Medicine, Baltimore, Maryland.,Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins School of Medicine, Baltimore, Maryland
| | - Elisabeth Glowatzki
- Center for Hearing and Balance, Johns Hopkins School of Medicine, Baltimore, Maryland.,Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins School of Medicine, Baltimore, Maryland.,Department of Neuroscience, Johns Hopkins School of Medicine, Baltimore, Maryland
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32
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Rutherford MA, von Gersdorff H, Goutman JD. Encoding sound in the cochlea: from receptor potential to afferent discharge. J Physiol 2021; 599:2527-2557. [PMID: 33644871 PMCID: PMC8127127 DOI: 10.1113/jp279189] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Accepted: 02/22/2021] [Indexed: 12/17/2022] Open
Abstract
Ribbon-class synapses in the ear achieve analog to digital transformation of a continuously graded membrane potential to all-or-none spikes. In mammals, several auditory nerve fibres (ANFs) carry information from each inner hair cell (IHC) to the brain in parallel. Heterogeneity of transmission among synapses contributes to the diversity of ANF sound-response properties. In addition to the place code for sound frequency and the rate code for sound level, there is also a temporal code. In series with cochlear amplification and frequency tuning, neural representation of temporal cues over a broad range of sound levels enables auditory comprehension in noisy multi-speaker settings. The IHC membrane time constant introduces a low-pass filter that attenuates fluctuations of the receptor potential above 1-2 kHz. The ANF spike generator adds a high-pass filter via its depolarization-rate threshold that rejects slow changes in the postsynaptic potential and its phasic response property that ensures one spike per depolarization. Synaptic transmission involves several stochastic subcellular processes between IHC depolarization and ANF spike generation, introducing delay and jitter that limits the speed and precision of spike timing. ANFs spike at a preferred phase of periodic sounds in a process called phase-locking that is limited to frequencies below a few kilohertz by both the IHC receptor potential and the jitter in synaptic transmission. During phase-locking to periodic sounds of increasing intensity, faster and facilitated activation of synaptic transmission and spike generation may be offset by presynaptic depletion of synaptic vesicles, resulting in relatively small changes in response phase. Here we review encoding of spike-timing at cochlear ribbon synapses.
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Affiliation(s)
- Mark A. Rutherford
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Henrique von Gersdorff
- Vollum Institute, Oregon Hearing Research Center, Oregon Health and Sciences University, Portland, Oregon 97239
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Krinner S, Predoehl F, Burfeind D, Vogl C, Moser T. RIM-Binding Proteins Are Required for Normal Sound-Encoding at Afferent Inner Hair Cell Synapses. Front Mol Neurosci 2021; 14:651935. [PMID: 33867935 PMCID: PMC8044855 DOI: 10.3389/fnmol.2021.651935] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 02/22/2021] [Indexed: 11/19/2022] Open
Abstract
The afferent synapses between inner hair cells (IHC) and spiral ganglion neurons are specialized to faithfully encode sound with sub-millisecond precision over prolonged periods of time. Here, we studied the role of Rab3 interacting molecule-binding proteins (RIM-BP) 1 and 2 – multidomain proteins of the active zone known to directly interact with RIMs, Bassoon and CaV1.3 – in IHC presynaptic function and hearing. Recordings of auditory brainstem responses and otoacoustic emissions revealed that genetic disruption of RIM-BPs 1 and 2 in mice (RIM-BP1/2–/–) causes a synaptopathic hearing impairment exceeding that found in mice lacking RIM-BP2 (RIM-BP2–/–). Patch-clamp recordings from RIM-BP1/2–/– IHCs indicated a subtle impairment of exocytosis from the readily releasable pool of synaptic vesicles that had not been observed in RIM-BP2–/– IHCs. In contrast, the reduction of Ca2+-influx and sustained exocytosis was similar to that in RIMBP2–/– IHCs. We conclude that both RIM-BPs are required for normal sound encoding at the IHC synapse, whereby RIM-BP2 seems to take the leading role.
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Affiliation(s)
- Stefanie Krinner
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Collaborative Research Center 1286, University of Göttingen, Göttingen, Germany.,Auditory Neuroscience Group, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Friederike Predoehl
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany
| | - Dinah Burfeind
- Presynaptogenesis and Intracellular Transport in Hair Cells Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany
| | - Christian Vogl
- Auditory Neuroscience Group, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Presynaptogenesis and Intracellular Transport in Hair Cells Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany
| | - Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Collaborative Research Center 1286, University of Göttingen, Göttingen, Germany.,Auditory Neuroscience Group, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Multiscale Bioimaging Cluster of Excellence, University of Göttingen, Göttingen, Germany
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34
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Brown WGA, Needham K, Begeng JM, Thompson AC, Nayagam BA, Kameneva T, Stoddart PR. Response of primary auditory neurons to stimulation with infrared light in vitro. J Neural Eng 2021; 18:046003. [PMID: 33724234 DOI: 10.1088/1741-2552/abe7b8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
OBJECTIVE Infrared light can be used to modulate the activity of neuronal cells through thermally-evoked capacitive currents and thermosensitive ion channel modulation. The infrared power threshold for action potentials has previously been found to be far lower in the in vivo cochlea when compared with other neuronal targets, implicating spiral ganglion neurons (SGNs) as a potential target for infrared auditory prostheses. However, conflicting experimental evidence suggests that this low threshold may arise from an intermediary mechanism other than direct SGN stimulation, potentially involving residual hair cell activity. APPROACH Patch-clamp recordings from cultured SGNs were used to explicitly quantify the capacitive and ion channel currents in an environment devoid of hair cells. Neurons were irradiated by a 1870 nm laser with pulse durations of 0.2-5.0 ms and powers up to 1.5 W. A Hodgkin-Huxley-type model was established by first characterising the voltage dependent currents, and then incorporating laser-evoked currents separated into temperature-dependent and temperature-gradient-dependent components. This model was found to accurately simulate neuronal responses and allowed the results to be extrapolated to stimulation parameter spaces not accessible during this study. MAIN RESULTS The previously-reported low in vivo SGN stimulation threshold was not observed, and only subthreshold depolarisation was achieved, even at high light exposures. Extrapolating these results with our Hodgkin-Huxley-type model predicts an action potential threshold which does not deviate significantly from other neuronal types. SIGNIFICANCE This suggests that the low-threshold response that is commonly reported in vivo may arise from an alternative mechanism, and calls into question the potential usefulness of the effect for auditory prostheses. The step-wise approach to modelling optically-evoked currents described here may prove useful for analysing a wider range of cell types where capacitive currents and conductance modulation are dominant.
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Affiliation(s)
- William G A Brown
- Faculty of Science, Engineering and Technology, Swinburne University of Technology, John Street, Hawthorn VIC 3122, Australia
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35
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Liu W, Luque M, Li H, Schrott-Fischer A, Glueckert R, Tylstedt S, Rajan G, Ladak H, Agrawal S, Rask-Andersen H. Spike Generators and Cell Signaling in the Human Auditory Nerve: An Ultrastructural, Super-Resolution, and Gene Hybridization Study. Front Cell Neurosci 2021; 15:642211. [PMID: 33796009 PMCID: PMC8008129 DOI: 10.3389/fncel.2021.642211] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Accepted: 02/22/2021] [Indexed: 11/23/2022] Open
Abstract
Background: The human auditory nerve contains 30,000 nerve fibers (NFs) that relay complex speech information to the brain with spectacular acuity. How speech is coded and influenced by various conditions is not known. It is also uncertain whether human nerve signaling involves exclusive proteins and gene manifestations compared with that of other species. Such information is difficult to determine due to the vulnerable, "esoteric," and encapsulated human ear surrounded by the hardest bone in the body. We collected human inner ear material for nanoscale visualization combining transmission electron microscopy (TEM), super-resolution structured illumination microscopy (SR-SIM), and RNA-scope analysis for the first time. Our aim was to gain information about the molecular instruments in human auditory nerve processing and deviations, and ways to perform electric modeling of prosthetic devices. Material and Methods: Human tissue was collected during trans-cochlear procedures to remove petro-clival meningioma after ethical permission. Cochlear neurons were processed for electron microscopy, confocal microscopy (CM), SR-SIM, and high-sensitive in situ hybridization for labeling single mRNA transcripts to detect ion channel and transporter proteins associated with nerve signal initiation and conductance. Results: Transport proteins and RNA transcripts were localized at the subcellular level. Hemi-nodal proteins were identified beneath the inner hair cells (IHCs). Voltage-gated ion channels (VGICs) were expressed in the spiral ganglion (SG) and axonal initial segments (AISs). Nodes of Ranvier (NR) expressed Nav1.6 proteins, and encoding genes critical for inter-cellular coupling were disclosed. Discussion: Our results suggest that initial spike generators are located beneath the IHCs in humans. The first NRs appear at different places. Additional spike generators and transcellular communication may boost, sharpen, and synchronize afferent signals by cell clusters at different frequency bands. These instruments may be essential for the filtering of complex sounds and may be challenged by various pathological conditions.
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Affiliation(s)
- Wei Liu
- Section of Otolaryngology, Department of Surgical Sciences, Head and Neck Surgery, Uppsala University Hospital, Uppsala, Sweden
| | - Maria Luque
- Department of Otorhinolaryngology, Medical University of Innsbruck, Innsbruck, Austria
| | - Hao Li
- Section of Otolaryngology, Department of Surgical Sciences, Head and Neck Surgery, Uppsala University Hospital, Uppsala, Sweden
| | | | - Rudolf Glueckert
- Department of Otorhinolaryngology, Medical University of Innsbruck, Innsbruck, Austria
| | - Sven Tylstedt
- Department of Olaryngology, Västerviks Hospital, Västervik, Sweden
| | - Gunesh Rajan
- Department of Otolaryngology, Head & Neck Surgery, Luzerner Kantonsspital, Luzern, Switzerland
- Department of Otolaryngology, Head & Neck Surgery, Division of Surgery, Medical School, University of Western Australia, Perth, WA, Australia
| | - Hanif Ladak
- Department of Otolaryngology-Head and Neck Surgery, Department of Medical Biophysics and Department of Electrical and Computer Engineering, Western University, London, ON, Canada
| | - Sumit Agrawal
- Department of Otolaryngology-Head and Neck Surgery, Western University, London, ON, Canada
| | - Helge Rask-Andersen
- Section of Otolaryngology, Department of Surgical Sciences, Head and Neck Surgery, Uppsala University Hospital, Uppsala, Sweden
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36
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Phase-Locking Requires Efficient Ca 2+ Extrusion at the Auditory Hair Cell Ribbon Synapse. J Neurosci 2021; 41:1625-1635. [PMID: 33446517 DOI: 10.1523/jneurosci.1324-18.2020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Revised: 08/25/2020] [Accepted: 12/27/2020] [Indexed: 11/21/2022] Open
Abstract
Proper perception of sounds in the environment requires auditory signals to be encoded with extraordinary temporal precision up to tens of microseconds, but how it originates from the hearing organs in the periphery is poorly understood. In particular, sound-evoked spikes in auditory afferent fibers in vivo are phase-locked to sound frequencies up to 5 kHz, but it is not clear how hair cells can handle intracellular Ca2+ changes with such high speed and efficiency. In this study, we combined patch-clamp recording and two-photon Ca2+ imaging to examine Ca2+ dynamics in hair cell ribbon synapses in the bullfrog amphibian papilla of both sexes. We found that Ca2+ clearance from single synaptic ribbons followed a double exponential function, and the weight of the fast component, but not the two time constants, was significantly reduced for prolonged stimulation, and during inhibition of the plasma membrane Ca2+ ATPase (PMCA), the mitochondrial Ca2+ uptake (MCU), or the sarcolemma/endoplasmic reticulum Ca2+ ATPase (SERCA), but not the Na+/Ca2+ exchanger (NCX). Furthermore, we found that both the basal Ca2+ level and the Ca2+ rise during sinusoidal stimulation were significantly increased by inhibition of PMCA, MCU, or SERCA. Consistently, phase-locking of synaptic vesicle releases from hair cells was also significantly reduced by blocking PMCA, MCU, or SERCA, but not NCX. We conclude that, in addition to fast diffusion mediated by mobile Ca2+ buffer, multiple Ca2+ extrusion pumps are required for phase-locking at the auditory hair cell ribbon synapse.SIGNIFICANCE STATEMENT Hair cell synapses can transmit sound-driven signals precisely in the kHz range. However, previous studies of Ca2+ handling in auditory hair cells have often been conducted in immature hair cells, with elevated extracellular Ca2+ concentration, or through steady-state stimulation that may not be physiologically relevant. Here we examine Ca2+ clearance from hair cell synaptic ribbons in a fully mature preparation at physiological concentration of external Ca2+ and at physiological temperature. By stimulating hair cells with sinusoidal voltage commands that mimic pure sound tones, we recapitulated the phase-locking of hair cell exocytosis with an in vitro approach. This allowed us to reveal the Ca2+ extrusion mechanisms that are required for phase-locking at auditory hair cell ribbon synapses.
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37
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Petitpré C, Bourien J, Wu H, Diuba A, Puel JL, Lallemend F. Genetic and functional diversity of primary auditory afferents. CURRENT OPINION IN PHYSIOLOGY 2020. [DOI: 10.1016/j.cophys.2020.09.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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38
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Kim WB, Kang KW, Sharma K, Yi E. Distribution of K v3 Subunits in Cochlear Afferent and Efferent Nerve Fibers Implies Distinct Role in Auditory Processing. Exp Neurobiol 2020; 29:344-355. [PMID: 33154197 PMCID: PMC7649084 DOI: 10.5607/en20043] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 10/14/2020] [Accepted: 10/16/2020] [Indexed: 11/19/2022] Open
Abstract
Kv3 family K+ channels, by ensuring speedy repolarization of action potential, enable rapid and high frequency neuronal firing and high precision temporal coding of auditory information in various auditory synapses in the brain. Expression of different Kv3 subtypes within the auditory end organ has been reported. Yet, their precise role at the hair cell synaptic transmission has not been fully elucidated. Using immunolabeling and confocal microscopy we examined the expression pattern of different Kv3 family K+ channel subunits in the nerve fibers innervating the cochlear hair cells. Kv3.1b was found in NKA-positive type 1 afferent fibers, exhibiting high signal intensity at the cell body, the unmyelinated dendritic segment, first heminode and nodes of Ranvier. Kv3.3 signal was detected in the cell body and the unmyelinated dendritic segment of NKA-positive type 1 afferent fibers but not in peripherin-positive type 2 afferent. Kv3.4 was found in ChAT-positive LOC and MOC efferent fibers as well as peripherin-positive type 2 afferent fibers. Such segregated expression pattern implies that each Kv3 subunits participate in different auditory tasks, for example, Kv3.1b and Kv3.3 in ascending signaling while Kv3.4 in feedback upon loud noise exposure.
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Affiliation(s)
- Woo Bin Kim
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, Korea
| | - Kwon-Woo Kang
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, Korea
| | - Kushal Sharma
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, Korea
| | - Eunyoung Yi
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, Korea
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39
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Markowitz AL, Kalluri R. Gradients in the biophysical properties of neonatal auditory neurons align with synaptic contact position and the intensity coding map of inner hair cells. eLife 2020; 9:e55378. [PMID: 32639234 PMCID: PMC7343388 DOI: 10.7554/elife.55378] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 06/24/2020] [Indexed: 02/07/2023] Open
Abstract
Sound intensity is encoded by auditory neuron subgroups that differ in thresholds and spontaneous rates. Whether variations in neuronal biophysics contributes to this functional diversity is unknown. Because intensity thresholds correlate with synaptic position on sensory hair cells, we combined patch clamping with fiber labeling in semi-intact cochlear preparations in neonatal rats from both sexes. The biophysical properties of auditory neurons vary in a striking spatial gradient with synaptic position. Neurons with high thresholds to injected currents contact hair cells at synaptic positions where neurons with high thresholds to sound-intensity are found in vivo. Alignment between in vitro and in vivo thresholds suggests that biophysical variability contributes to intensity coding. Biophysical gradients were evident at all ages examined, indicating that cell diversity emerges in early post-natal development and persists even after continued maturation. This stability enabled a remarkably successful model for predicting synaptic position based solely on biophysical properties.
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Affiliation(s)
- Alexander L Markowitz
- Neuroscience Graduate Program, University of Southern CaliforniaLos AngelesUnited States
- Department of Otolaryngology, Keck School of Medicine, University of Southern CaliforniaLos AngelesUnited States
| | - Radha Kalluri
- Neuroscience Graduate Program, University of Southern CaliforniaLos AngelesUnited States
- Department of Otolaryngology, Keck School of Medicine, University of Southern CaliforniaLos AngelesUnited States
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern CaliforniaLos AngelesUnited States
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40
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Tserga E, Damberg P, Canlon B, Cederroth CR. Auditory synaptopathy in mice lacking the glutamate transporter GLAST and its impact on brain activity. PROGRESS IN BRAIN RESEARCH 2020; 262:245-261. [PMID: 33931183 DOI: 10.1016/bs.pbr.2020.04.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Neurotransmission of acoustic signals from the hair cells to the auditory nerve relies on a tightly controlled communication between pre-synaptic ribbons and post-synaptic glutamatergic terminals. After noise overexposure, de-afferentation occurs as a consequence of excessive glutamate release. What maintains synaptic integrity in the cochlea is poorly understood. The objective of this study is to evaluate the role of GLAST in maintaining synaptic integrity in the cochlea in absence or presence of noise, and its impact on sound-evoked brain activity using manganese-enhanced MRI (MeMRI). The glutamate aspartate transporter GLAST is present in supporting cells near the afferent synapse and its genetic deletion leads to greater synaptic swelling after noise overexposure. At baseline, GLAST knockout (GLAST KO) mice displayed two-fold lower wave 1 amplitude of the auditory brainstem response (ABR) when compared to their wild-type littermates in spite of similar ABR and distortion product otoacoustic emissions (DPOAE) thresholds. While the abundance of ribbons was not affected by the loss of GLAST function, the number of paired synapses was halved in GLAST KO mice, suggestive of a pre-existing auditory synaptopathy. Immediately after the noise exposure ABR thresholds rose by 41-62dB to a similar degree in GLAST WT and KO mice and DPOAE remained unaffected. In the acute phase following noise exposure, GLAST KO mice showed near complete de-afferentation unlike WT mice which maintained four to seven paired synapses per IHC. Brain activity using MeMRI found noise exposure to cause greater activity in the inferior colliculus in GLAST KO but not in WT mice. No changes in brain activity was found in GLAST KO mice at baseline in spite of affected afferent synapses, suggesting that auditory synaptopathy may not be sufficient to alter brain activity in the absence of noise exposure.
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Affiliation(s)
- Evangelia Tserga
- Laboratory of Experimental Audiology, Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Peter Damberg
- Karolinska Experimental Research and Imaging Center, Karolinska University Hospital, Stockholm, Sweden
| | - Barbara Canlon
- Laboratory of Experimental Audiology, Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Christopher R Cederroth
- Laboratory of Experimental Audiology, Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
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41
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Wu JS, Yi E, Manca M, Javaid H, Lauer AM, Glowatzki E. Sound exposure dynamically induces dopamine synthesis in cholinergic LOC efferents for feedback to auditory nerve fibers. eLife 2020; 9:52419. [PMID: 31975688 PMCID: PMC7043886 DOI: 10.7554/elife.52419] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Accepted: 01/23/2020] [Indexed: 11/13/2022] Open
Abstract
Lateral olivocochlear (LOC) efferent neurons modulate auditory nerve fiber (ANF) activity using a large repertoire of neurotransmitters, including dopamine (DA) and acetylcholine (ACh). Little is known about how individual neurotransmitter systems are differentially utilized in response to the ever-changing acoustic environment. Here we present quantitative evidence in rodents that the dopaminergic LOC input to ANFs is dynamically regulated according to the animal's recent acoustic experience. Sound exposure upregulates tyrosine hydroxylase, an enzyme responsible for dopamine synthesis, in cholinergic LOC intrinsic neurons, suggesting that individual LOC neurons might at times co-release ACh and DA. We further demonstrate that dopamine down-regulates ANF firing rates by reducing both the hair cell release rate and the size of synaptic events. Collectively, our results suggest that LOC intrinsic neurons can undergo on-demand neurotransmitter re-specification to re-calibrate ANF activity, adjust the gain at hair cell/ANF synapses, and possibly to protect these synapses from noise damage.
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Affiliation(s)
- Jingjing Sherry Wu
- Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, United States.,The Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, United States.,The Center for Hearing and Balance, The Johns Hopkins University School of Medicine, Baltimore, United States
| | - Eunyoung Yi
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan-gun, Republic of Korea
| | - Marco Manca
- The Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, United States.,The Center for Hearing and Balance, The Johns Hopkins University School of Medicine, Baltimore, United States.,Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University School of Medicine, Baltimore, United States
| | - Hamad Javaid
- The Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, United States.,The Center for Hearing and Balance, The Johns Hopkins University School of Medicine, Baltimore, United States.,Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University School of Medicine, Baltimore, United States
| | - Amanda M Lauer
- The Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, United States.,The Center for Hearing and Balance, The Johns Hopkins University School of Medicine, Baltimore, United States.,Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University School of Medicine, Baltimore, United States
| | - Elisabeth Glowatzki
- Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, United States.,The Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, United States.,The Center for Hearing and Balance, The Johns Hopkins University School of Medicine, Baltimore, United States.,Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University School of Medicine, Baltimore, United States
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42
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C Kohrman D, Wan G, Cassinotti L, Corfas G. Hidden Hearing Loss: A Disorder with Multiple Etiologies and Mechanisms. Cold Spring Harb Perspect Med 2020; 10:cshperspect.a035493. [PMID: 30617057 DOI: 10.1101/cshperspect.a035493] [Citation(s) in RCA: 86] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Hidden hearing loss (HHL), a recently described auditory disorder, has been proposed to affect auditory neural processing and hearing acuity in subjects with normal audiometric thresholds, particularly in noisy environments. In contrast to central auditory processing disorders, HHL is caused by defects in the cochlea, the peripheral auditory organ. Noise exposure, aging, ototoxic drugs, and peripheral neuropathies are some of the known risk factors for HHL. Our knowledge of the causes and mechanisms of HHL are based primarily on animal models. However, recent clinical studies have also shed light on the etiology and prevalence of this cochlear disorder and how it may affect auditory perception in humans. Here, we review the current knowledge regarding the causes and cellular mechanisms of HHL, summarize information on available noninvasive tests for differential diagnosis, and discuss potential therapeutic approaches for treatment of HHL.
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Affiliation(s)
- David C Kohrman
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, Michigan 48109
| | - Guoqiang Wan
- MOE Key Laboratory of Model Animals for Disease Study, Model Animal Research Center of Nanjing University, Nanjing 210061, Jiangsu Province, China.,Institute for Brain Sciences, Nanjing University, Nanjing 210061, Jiangsu Province, China
| | - Luis Cassinotti
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, Michigan 48109
| | - Gabriel Corfas
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, Michigan 48109
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Moser T, Grabner CP, Schmitz F. Sensory Processing at Ribbon Synapses in the Retina and the Cochlea. Physiol Rev 2020; 100:103-144. [DOI: 10.1152/physrev.00026.2018] [Citation(s) in RCA: 80] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
In recent years, sensory neuroscientists have made major efforts to dissect the structure and function of ribbon synapses which process sensory information in the eye and ear. This review aims to summarize our current understanding of two key aspects of ribbon synapses: 1) their mechanisms of exocytosis and endocytosis and 2) their molecular anatomy and physiology. Our comparison of ribbon synapses in the cochlea and the retina reveals convergent signaling mechanisms, as well as divergent strategies in different sensory systems.
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Affiliation(s)
- Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Auditory Neuroscience Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany; Synaptic Nanophysiology Group, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany; and Institute for Anatomy and Cell Biology, Department of Neuroanatomy, Medical School, Saarland University, Homburg, Germany
| | - Chad P. Grabner
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Auditory Neuroscience Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany; Synaptic Nanophysiology Group, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany; and Institute for Anatomy and Cell Biology, Department of Neuroanatomy, Medical School, Saarland University, Homburg, Germany
| | - Frank Schmitz
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Auditory Neuroscience Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany; Synaptic Nanophysiology Group, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany; and Institute for Anatomy and Cell Biology, Department of Neuroanatomy, Medical School, Saarland University, Homburg, Germany
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Dombrowski T, Rankovic V, Moser T. Toward the Optical Cochlear Implant. Cold Spring Harb Perspect Med 2019; 9:cshperspect.a033225. [PMID: 30323016 DOI: 10.1101/cshperspect.a033225] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
When hearing fails, cochlear implants (CIs) provide open speech perception to most of the currently half a million CI users. CIs bypass the defective sensory organ and stimulate the auditory nerve electrically. The major bottleneck of current CIs is the poor coding of spectral information, which results from wide current spread from each electrode contact. As light can be more conveniently confined, optical stimulation of the auditory nerve presents a promising perspective for a fundamental advance of CIs. Moreover, given the improved frequency resolution of optical excitation and its versatility for arbitrary stimulation patterns the approach also bears potential for auditory research. Here, we review the current state of the art focusing on the emerging concept of optogenetic stimulation of the auditory pathway. Developing optogenetic stimulation for auditory research and future CIs requires efforts toward viral gene transfer to the neurons, design and characterization of appropriate optogenetic actuators, as well as engineering of multichannel optical implants.
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Affiliation(s)
- Tobias Dombrowski
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center, 37075 Göttingen, Germany.,Department of Otorhinolaryngology, Head and Neck Surgery, Ruhr University Bochum, St. Elisabeth Hospital, 44787 Bochum, Germany
| | - Vladan Rankovic
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center, 37075 Göttingen, Germany.,Auditory Neuroscience and Optogenetics Group, German Primate Center, 37077 Göttingen, Germany
| | - Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center, 37075 Göttingen, Germany.,Auditory Neuroscience and Optogenetics Group, German Primate Center, 37077 Göttingen, Germany.,Auditory Neuroscience Group, Max-Planck-Institute for Experimental Medicine, 37075 Göttingen, Germany
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How to Build a Fast and Highly Sensitive Sound Detector That Remains Robust to Temperature Shifts. J Neurosci 2019; 39:7260-7276. [PMID: 31315946 DOI: 10.1523/jneurosci.2510-18.2019] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Revised: 06/13/2019] [Accepted: 07/09/2019] [Indexed: 12/26/2022] Open
Abstract
Frogs must have sharp hearing abilities during the warm summer months to successfully find mating partners. This study aims to understand how frog hair cell ribbon-type synapses preserve both sensitivity and temporal precision during temperature changes. Under room (∼24°C) and high (∼32°C) temperature, we performed in vitro patch-clamp recordings of hair cells and their afferent fibers in amphibian papillae of either male or female bullfrogs. Afferent fibers exhibited a wide heterogeneity in membrane input resistance (Rin) from 100 mΩ to 1000 mΩ, which may contribute to variations in spike threshold and firing frequency. At higher temperatures, most fibers increased their frequency of spike firing due to an increase in spontaneous EPSC frequencies. Hair cell resting membrane potential (Vrest) remained surprisingly stable during temperature increases, because Ca2+ influx and K+ outflux increased simultaneously. This increase in Ca2+ current likely enhanced spontaneous EPSC frequencies. These larger "leak currents" at Vrest also lowered Rin and produced higher electrical resonant frequencies. Lowering Rin will reduce the hair cells receptor potential and presumably moderate the systems sensitivity. Using membrane capacitance measurements, we suggest that hair cells can partially compensate for this reduced sensitivity by increasing exocytosis efficiency and the size of the readily releasable pool of synaptic vesicles. Furthermore, paired recordings of hair cells and their afferent fibers showed that synaptic delays shortened and multivesicular release becomes more synchronous at higher temperatures, which should improve temporal precision. Together, our results explain many previous in vivo observations on the temperature dependence of spikes in auditory nerves.SIGNIFICANCE STATEMENT The vertebrate inner ear detects and transmits auditory information over a broad dynamic range of sound frequency and intensity. It achieves remarkable sensitivity to soft sounds and precise frequency selectivity. How does the ear of cold-blooded vertebrates maintain its performance level as temperature changes? More specifically, how does the hair cell to afferent fiber synapse in bullfrog amphibian papilla adjust to a wide range of physiological temperatures without losing its sensitivity and temporal fidelity to sound signals? This study uses in vitro experiments to reveal the biophysical mechanisms that explain many observations made from in vivo auditory nerve fiber recordings. We find that higher temperature facilitates vesicle exocytosis and electrical tuning to higher sound frequencies, which benefits sensitivity and selectivity.
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Liu W, Wang X, Wang M, Wang H. Protection of Spiral Ganglion Neurons and Prevention of Auditory Neuropathy. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1130:93-107. [DOI: 10.1007/978-981-13-6123-4_6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/28/2023]
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Phase Locking of Auditory-Nerve Fibers Reveals Stereotyped Distortions and an Exponential Transfer Function with a Level-Dependent Slope. J Neurosci 2019; 39:4077-4099. [PMID: 30867259 DOI: 10.1523/jneurosci.1801-18.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 02/28/2019] [Accepted: 03/07/2019] [Indexed: 12/16/2022] Open
Abstract
Phase locking of auditory-nerve-fiber (ANF) responses to the fine structure of acoustic stimuli is a hallmark of the auditory system's temporal precision and is important for many aspects of hearing. Period histograms from phase-locked ANF responses to low-frequency tones exhibit spike-rate and temporal asymmetries, but otherwise retain an approximately sinusoidal shape as stimulus level increases, even beyond the level at which the mean spike rate saturates. This is intriguing because apical cochlear mechanical vibrations show little compression, and mechanoelectrical transduction in the receptor cells is thought to obey a static sigmoidal nonlinearity, which might be expected to produce peak clipping at moderate and high stimulus levels. Here we analyze phase-locked responses of ANFs from cats of both sexes. We show that the lack of peak clipping is due neither to ANF refractoriness nor to spike-rate adaptation on time scales longer than the stimulus period. We demonstrate that the relationship between instantaneous pressure and instantaneous rate is well described by an exponential function whose slope decreases with increasing stimulus level. Relatively stereotyped harmonic distortions in the input to the exponential can account for the temporal asymmetry of the period histograms, including peak splitting. We show that the model accounts for published membrane-potential waveforms when assuming a power-of-three, but not a power-of-one, relationship to exocytosis. Finally, we demonstrate the relationship between the exponential transfer functions and the sigmoidal pseudotransducer functions obtained in the literature by plotting the maxima and minima of the voltage responses against the maxima and minima of the stimuli.SIGNIFICANCE STATEMENT Phase locking of auditory-nerve-fiber responses to the temporal fine structure of acoustic stimuli is important for many aspects of hearing, but the mechanisms underlying phase locking are not fully understood. Intriguingly, period histograms retain an approximately sinusoidal shape across sound levels, even when the mean rate has saturated. We find that neither refractoriness nor spike-rate adaptation is responsible for this behavior. Instead, the peripheral auditory system operates as though it contains an exponential transfer function whose slope changes with stimulus level. The underlying mechanism is distinct from the comparatively weak cochlear mechanical compression in the cochlear apex, and likely resides in the receptor cells.
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Takago H, Oshima-Takago T, Moser T. Disruption of Otoferlin Alters the Mode of Exocytosis at the Mouse Inner Hair Cell Ribbon Synapse. Front Mol Neurosci 2019; 11:492. [PMID: 30687007 PMCID: PMC6338019 DOI: 10.3389/fnmol.2018.00492] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2018] [Accepted: 12/19/2018] [Indexed: 11/24/2022] Open
Abstract
Sound encoding relies on Ca2+-mediated exocytosis at the ribbon synapse between cochlear inner hair cells (IHCs) and type I spiral ganglion neurons (SGNs). Otoferlin, a multi-C2 domain protein, is proposed to regulate Ca2+-triggered exocytosis at this synapse, but the precise mechanisms of otoferlin function remain to be elucidated. Here, performing whole-cell voltage-clamp recordings of excitatory postsynaptic currents (EPSCs) from SGNs in otoferlin mutant mice, we investigated the impact of Otof disruption at individual synapses with single release event resolution. Otof deletion decreased the spontaneous release rate and abolished the stimulus-secretion coupling. This was evident from failure of potassium-induced IHC depolarization to stimulate release and supports the proposed role of otoferlin in Ca2+ sensing for fusion. A missense mutation in the Otof gene (pachanga), in which otoferlin level at the IHC plasma membrane was lowered without changing its Ca2+ binding, also reduced the spontaneous release rate but spared the stimulus-secretion coupling. The slowed stimulated release rate supports the hypothesis that a sufficient abundance of otoferlin at the plasma membrane is crucial for the vesicle supply. Large-sized monophasic EPSCs remained present upon Otof deletion despite the drastic reduction of the rate of exocytosis. However, EPSC amplitude, on average, was modestly decreased. Moreover, a reduced contribution of multiphasic EPSC was observed in both Otof mutants. We argue that the presence of large monophasic EPSCs despite the exocytic defect upon Otof deletion supports the uniquantal hypothesis of transmitter release at the IHC ribbon synapse. Based upon the reduced contribution of multiphasic EPSC, we propose a role of otoferlin in regulating the mode of exocytosis in IHCs.
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Affiliation(s)
- Hideki Takago
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Department of Rehabilitation for Sensory Functions, Research Institute, National Rehabilitation Center for Persons with Disabilities, Saitama, Japan.,Collaborative Research Center 889 Cellular Mechanisms of Sensory Processing, Göttingen, Germany
| | - Tomoko Oshima-Takago
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Department of Rehabilitation for Sensory Functions, Research Institute, National Rehabilitation Center for Persons with Disabilities, Saitama, Japan.,Collaborative Research Center 889 Cellular Mechanisms of Sensory Processing, Göttingen, Germany.,Göttingen Graduate School for Neurosciences and Molecular Biosciences, University of Göttingen, Göttingen, Germany
| | - Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Collaborative Research Center 889 Cellular Mechanisms of Sensory Processing, Göttingen, Germany.,Göttingen Graduate School for Neurosciences and Molecular Biosciences, University of Göttingen, Göttingen, Germany.,Auditory Neuroscience Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany.,Synaptic Nanophysiology Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
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49
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Pangrsic T, Singer JH, Koschak A. Voltage-Gated Calcium Channels: Key Players in Sensory Coding in the Retina and the Inner Ear. Physiol Rev 2019; 98:2063-2096. [PMID: 30067155 DOI: 10.1152/physrev.00030.2017] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Calcium influx through voltage-gated Ca (CaV) channels is the first step in synaptic transmission. This review concerns CaV channels at ribbon synapses in primary sense organs and their specialization for efficient coding of stimuli in the physical environment. Specifically, we describe molecular, biochemical, and biophysical properties of the CaV channels in sensory receptor cells of the retina, cochlea, and vestibular apparatus, and we consider how such properties might change over the course of development and contribute to synaptic plasticity. We pay particular attention to factors affecting the spatial arrangement of CaV channels at presynaptic, ribbon-type active zones, because the spatial relationship between CaV channels and release sites has been shown to affect synapse function critically in a number of systems. Finally, we review identified synaptopathies affecting sensory systems and arising from dysfunction of L-type, CaV1.3, and CaV1.4 channels or their protein modulatory elements.
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Affiliation(s)
- Tina Pangrsic
- Synaptic Physiology of Mammalian Vestibular Hair Cells Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen and Auditory Neuroscience Group, Max Planck Institute of Experimental Medicine , Göttingen, Germany ; Department of Biology, University of Maryland , College Park, Maryland ; and Pharmacology and Toxicology, Institute of Pharmacy, University of Innsbruck , Innsbruck , Austria
| | - Joshua H Singer
- Synaptic Physiology of Mammalian Vestibular Hair Cells Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen and Auditory Neuroscience Group, Max Planck Institute of Experimental Medicine , Göttingen, Germany ; Department of Biology, University of Maryland , College Park, Maryland ; and Pharmacology and Toxicology, Institute of Pharmacy, University of Innsbruck , Innsbruck , Austria
| | - Alexandra Koschak
- Synaptic Physiology of Mammalian Vestibular Hair Cells Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen and Auditory Neuroscience Group, Max Planck Institute of Experimental Medicine , Göttingen, Germany ; Department of Biology, University of Maryland , College Park, Maryland ; and Pharmacology and Toxicology, Institute of Pharmacy, University of Innsbruck , Innsbruck , Austria
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Peterson AJ, Huet A, Bourien J, Puel JL, Heil P. Recovery of auditory-nerve-fiber spike amplitude under natural excitation conditions. Hear Res 2018; 370:248-263. [DOI: 10.1016/j.heares.2018.08.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 08/20/2018] [Accepted: 08/22/2018] [Indexed: 12/23/2022]
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