1
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Reijntjes DO, Pyott SJ. The afferent signaling complex: Regulation of type I spiral ganglion neuron responses in the auditory periphery. Hear Res 2016; 336:1-16. [DOI: 10.1016/j.heares.2016.03.011] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 02/12/2016] [Accepted: 03/07/2016] [Indexed: 12/19/2022]
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2
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Wang HC, Bergles DE. Spontaneous activity in the developing auditory system. Cell Tissue Res 2015; 361:65-75. [PMID: 25296716 PMCID: PMC7046314 DOI: 10.1007/s00441-014-2007-5] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Accepted: 09/09/2014] [Indexed: 12/13/2022]
Abstract
Spontaneous electrical activity is a common feature of sensory systems during early development. This sensory-independent neuronal activity has been implicated in promoting their survival and maturation, as well as growth and refinement of their projections to yield circuits that can rapidly extract information about the external world. Periodic bursts of action potentials occur in auditory neurons of mammals before hearing onset. This activity is induced by inner hair cells (IHCs) within the developing cochlea, which establish functional connections with spiral ganglion neurons (SGNs) several weeks before they are capable of detecting external sounds. During this pre-hearing period, IHCs fire periodic bursts of Ca(2+) action potentials that excite SGNs, triggering brief but intense periods of activity that pass through auditory centers of the brain. Although spontaneous activity requires input from IHCs, there is ongoing debate about whether IHCs are intrinsically active and their firing periodically interrupted by external inhibitory input (IHC-inhibition model), or are intrinsically silent and their firing periodically promoted by an external excitatory stimulus (IHC-excitation model). There is accumulating evidence that inner supporting cells in Kölliker's organ spontaneously release ATP during this time, which can induce bursts of Ca(2+) spikes in IHCs that recapitulate many features of auditory neuron activity observed in vivo. Nevertheless, the role of supporting cells in this process remains to be established in vivo. A greater understanding of the molecular mechanisms responsible for generating IHC activity in the developing cochlea will help reveal how these events contribute to the maturation of nascent auditory circuits.
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Affiliation(s)
- Han Chin Wang
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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3
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Braude JP, Vijayakumar S, Baumgarner K, Laurine R, Jones TA, Jones SM, Pyott SJ. Deletion of Shank1 has minimal effects on the molecular composition and function of glutamatergic afferent postsynapses in the mouse inner ear. Hear Res 2015; 321:52-64. [PMID: 25637745 DOI: 10.1016/j.heares.2015.01.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Revised: 12/24/2014] [Accepted: 01/13/2015] [Indexed: 01/06/2023]
Abstract
Shank proteins (1-3) are considered the master organizers of glutamatergic postsynaptic densities in the central nervous system, and the genetic deletion of either Shank1, 2, or 3 results in altered composition, form, and strength of glutamatergic postsynapses. To investigate the contribution of Shank proteins to glutamatergic afferent synapses of the inner ear and especially cochlea, we used immunofluorescence and quantitative real time PCR to determine the expression of Shank1, 2, and 3 in the cochlea. Because we found evidence for expression of Shank1 but not 2 and 3, we investigated the morphology, composition, and function of afferent postsynaptic densities from defined tonotopic regions in the cochlea of Shank1(-/-) mice. Using immunofluorescence, we identified subtle changes in the morphology and composition (but not number and localization) of cochlear afferent postsynaptic densities at the lower frequency region (8 kHz) in Shank1(-/-) mice compared to Shank1(+/+) littermates. However, we detected no differences in auditory brainstem responses at matching or higher frequencies. We also identified Shank1 in the vestibular afferent postsynaptic densities, but detected no differences in vestibular sensory evoked potentials in Shank1(-/-) mice compared to Shank1(+/+) littermates. This work suggests that Shank proteins play a different role in the development and maintenance of glutamatergic afferent synapses in the inner ear compared to the central nervous system.
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Affiliation(s)
- Jeremy P Braude
- University of North Carolina Wilmington, Department of Biology and Marine Biology, 601 South College Road, Wilmington, NC 28403, USA
| | - Sarath Vijayakumar
- University of Nebraska Lincoln, Department of Special Education and Communication Disorders, 304B Barkley Memorial Center, Lincoln, NE 68583-0738, USA
| | - Katherine Baumgarner
- University of North Carolina Wilmington, Department of Biology and Marine Biology, 601 South College Road, Wilmington, NC 28403, USA
| | - Rebecca Laurine
- University of North Carolina Wilmington, Department of Biology and Marine Biology, 601 South College Road, Wilmington, NC 28403, USA
| | - Timothy A Jones
- University of Nebraska Lincoln, Department of Special Education and Communication Disorders, 304B Barkley Memorial Center, Lincoln, NE 68583-0738, USA
| | - Sherri M Jones
- University of Nebraska Lincoln, Department of Special Education and Communication Disorders, 304B Barkley Memorial Center, Lincoln, NE 68583-0738, USA
| | - Sonja J Pyott
- University of North Carolina Wilmington, Department of Biology and Marine Biology, 601 South College Road, Wilmington, NC 28403, USA.
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4
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Huang LC, Barclay M, Lee K, Peter S, Housley GD, Thorne PR, Montgomery JM. Synaptic profiles during neurite extension, refinement and retraction in the developing cochlea. Neural Dev 2012; 7:38. [PMID: 23217150 PMCID: PMC3545844 DOI: 10.1186/1749-8104-7-38] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Accepted: 11/26/2012] [Indexed: 12/23/2022] Open
Abstract
Background During development, excess synapses form between the central and peripheral nervous systems that are then eliminated to achieve correct connectivity. In the peripheral auditory system, the developing type I spiral ganglion afferent fibres undergo a dramatic re-organisation, initially forming connections with both sensory inner hair cells (IHCs) and outer hair cells (OHCs). The OHC connections are then selectively eliminated, leaving sparse innervation by type II afferent fibres, whilst the type I afferent synapses with IHCs are consolidated. Results We examined the molecular makeup of the synaptic contacts formed onto the IHCs and OHCs during this period of afferent fibre remodelling. We observed that presynaptic ribbons initially form at all the afferent neurite contacts, i.e. not only at the expected developing IHC-type I fibre synapses but also at OHCs where type I fibres temporarily contact. Moreover, the transient contacts forming onto OHCs possess a broad set of pre- and postsynaptic proteins, suggesting that functional synaptic connections are formed prior to the removal of type I fibre innervation. AMPA-type glutamate receptor subunits were transiently observed at the base of the OHCs, with their downregulation occurring in parallel with the withdrawal of type I fibres, dispersal of presynaptic ribbons, and downregulation of the anchoring proteins Bassoon and Shank. Conversely, at developing type I afferent IHC synapses, the presence of pre- and postsynaptic scaffold proteins was maintained, with differential plasticity in AMPA receptor subunits observed and AMPA receptor subunit composition changing around hearing onset. Conclusions Overall our data show a differential balance in the patterns of synaptic proteins at developing afferent IHC versus OHC synapses that likely reflect their stable versus transient fates.
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Affiliation(s)
- Lin-Chien Huang
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand
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5
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Jin D, Ohlemiller KK, Lei D, Dong E, Role L, Ryugo DK, Bao J. Age-related neuronal loss in the cochlea is not delayed by synaptic modulation. Neurobiol Aging 2010; 32:2321.e13-23. [PMID: 20580130 DOI: 10.1016/j.neurobiolaging.2010.05.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2009] [Revised: 04/25/2010] [Accepted: 05/12/2010] [Indexed: 02/07/2023]
Abstract
Age-related synaptic change is associated with the functional decline of the nervous system. It is unknown whether this synaptic change is the cause or the consequence of neuronal cell loss. We have addressed this question by examining mice genetically engineered to over- or underexpress neuregulin-1 (NRG1), a direct modulator of synaptic transmission. Transgenic mice overexpressing NRG1 in spiral ganglion neurons (SGNs) showed improvements in hearing thresholds, whereas NRG1 -/+ mice show a complementary worsening of thresholds. However, no significant change in age-related loss of SGNs in either NRG1 -/+ mice or mice overexpressing NRG1 was observed, while a negative association between NRG1 expression level and survival of inner hair cells during aging was observed. Subsequent studies provided evidence that modulating NRG1 levels changes synaptic transmission between SGNs and hair cells. One of the most dramatic examples of this was the reversal of lower hearing thresholds by "turning-off" NRG1 overexpression. These data demonstrate for the first time that synaptic modulation is unable to prevent age-related neuronal loss in the cochlea.
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Affiliation(s)
- David Jin
- Department of Otolaryngology, Washington University, St. Louis, MO 63110, USA
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6
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Two modes of release shape the postsynaptic response at the inner hair cell ribbon synapse. J Neurosci 2010; 30:4210-20. [PMID: 20335456 DOI: 10.1523/jneurosci.4439-09.2010] [Citation(s) in RCA: 134] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Cochlear inner hair cells (IHCs) convert sounds into receptor potentials and via their ribbon synapses into firing rates in auditory nerve fibers. Multivesicular release at individual IHC ribbon synapses activates AMPA-mediated EPSCs with widely ranging amplitudes. The underlying mechanisms and specific role for multivesicular release in encoding sound are not well understood. Here we characterize the waveforms of individual EPSCs recorded from afferent boutons contacting IHCs and compare their characteristics in immature rats (postnatal days 8-11) and hearing rats (postnatal days 19-21). Two types of EPSC waveforms were found in every recording: monophasic EPSCs, with sharp rising phases and monoexponential decays, and multiphasic EPSCs, exhibiting inflections on rising and decaying phases. Multiphasic EPSCs exhibited slower rise times and smaller amplitudes than monophasic EPSCs. Both types of EPSCs had comparable charge transfers, suggesting that they were activated by the release of similar numbers of vesicles, which for multiphasic EPSCs occurred in a less coordinated manner. On average, a higher proportion of larger, monophasic EPSCs was found in hearing compared to immature rats. In addition, EPSCs became significantly faster with age. The developmental increase in size and speed could improve auditory signaling acuity. Multiphasic EPSCs persisted in hearing animals, in some fibers constituting half of the EPSCs. The proportion of monophasic versus multiphasic EPSCs varied widely across fibers, resulting in marked heterogeneity of amplitude distributions. We propose that the relative contribution of two modes of multivesicular release, generating monophasic and multiphasic EPSCs, may underlie fundamental characteristics of auditory nerve fibers.
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Jones TA, Leake PA, Snyder RL, Stakhovskaya O, Bonham B. Spontaneous discharge patterns in cochlear spiral ganglion cells before the onset of hearing in cats. J Neurophysiol 2007; 98:1898-908. [PMID: 17686914 PMCID: PMC2234389 DOI: 10.1152/jn.00472.2007] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Spontaneous neural activity has been recorded in the auditory nerve of cats as early as 2 days postnatal (P2), yet individual auditory neurons do not respond to ambient sound levels <90-100 dB SPL until about P10. Significant refinement of the central projections from the spiral ganglion to the cochlear nucleus occurs during this neonatal period. This refinement may be dependent on peripheral spontaneous discharge activity. We recorded from single spiral ganglion cells in kittens aged P3-P9. The spiral ganglion was accessed through the round window through the spiral lamina. A total of 112 ganglion cells were isolated for study in nine animals. Spike rates in neonates were very low, ranging from 0.06 to 56 spikes/s, with a mean of 3.09 +/- 8.24 spikes/s. Ganglion cells in neonatal kittens exhibited remarkable repetitive spontaneous bursting discharge patterns. The unusual patterns were evident in the large mean interval CV (CV(i) = 2.9 +/- 1.6) and burst index of 5.2 +/- 3.5 across ganglion cells. Spontaneous bursting patterns in these neonatal mammals were similar to those reported for cochlear ganglion cells of the embryonic chicken, suggesting this may be a general phenomenon that is common across animal classes. Rhythmic spontaneous discharge of retinal ganglion cells has been shown to be important in the development of central retinotopic projections and normal binocular vision. Bursting rhythms in cochlear ganglion cells may play a similar role in the auditory system during prehearing periods.
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Affiliation(s)
- Timothy A Jones
- Communication Sciences and Disorders, School of Allied Health Sciences, East Carolina University, Greenville, NC 27858-4353, USA.
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8
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Niu X, Canlon B. The signal transduction pathway for the dopamine D1 receptor in the guinea-pig cochlea. Neuroscience 2006; 137:981-90. [PMID: 16330149 DOI: 10.1016/j.neuroscience.2005.10.044] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2005] [Revised: 09/28/2005] [Accepted: 10/07/2005] [Indexed: 11/24/2022]
Abstract
Dopamine released from lateral efferent fibers modulates the activity of the auditory nerve, but the signaling mechanism by which this is mediated is not known. The present study investigated the signal transduction pathway for the dopamine D1 receptor in the guinea-pig cochlea. D1 receptor immunolabeling was localized to the spiral ganglia neurons and at the base of the inner hair cells. Western immunoblotting on whole cochlear preparations revealed positive bands for the D1 receptor and for dopamine and the cyclic AMP-regulated phosphoprotein. The amplitude of the compound action potential was enhanced in the presence of the D1 receptor agonist, SKF 38393, an effect that was abolished by H89, a protein kinase A inhibitor. Conversely, SKF 83566, a D1 receptor antagonist decreased the amplitude of compound action potential, while forskolin, a protein kinase A activator prevented this effect. Furthermore, it was found that the level of glutamate receptor 1 phosphorylation at the protein kinase A site (Ser845) was increased by the D1 agonist, but decreased by D1 antagonist. Our results provide evidence that the D1 receptor is localized in the spiral ganglion neurons as well as the nerve endings under the inner hair cells and they can modulate auditory nerve function. One signal transduction pathway of D1 receptor in the auditory nerve is via protein kinase A-mediated glutamate receptor 1 phosphorylation.
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MESH Headings
- 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine/analogs & derivatives
- 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine/pharmacology
- Action Potentials/drug effects
- Action Potentials/physiology
- Animals
- Blotting, Western
- Cochlea/physiology
- Cochlear Nerve/physiology
- Cyclic AMP-Dependent Protein Kinases/antagonists & inhibitors
- Cyclic AMP-Dependent Protein Kinases/metabolism
- Dopamine Agonists/pharmacology
- Dopamine and cAMP-Regulated Phosphoprotein 32/metabolism
- Female
- Guinea Pigs
- Immunohistochemistry
- Isoquinolines/pharmacology
- Male
- Oxidopamine
- Perfusion
- Receptors, AMPA/metabolism
- Receptors, Dopamine D1/agonists
- Receptors, Dopamine D1/antagonists & inhibitors
- Receptors, Dopamine D1/physiology
- Signal Transduction/physiology
- Sulfonamides/pharmacology
- Sympathectomy, Chemical
- Sympatholytics
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Affiliation(s)
- X Niu
- Department of Physiology and Pharmacology, Karolinska Institutet, 171 77 Stockholm, Sweden
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9
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Eybalin M, Caicedo A, Renard N, Ruel J, Puel JL. Transient Ca2+-permeable AMPA receptors in postnatal rat primary auditory neurons. Eur J Neurosci 2004; 20:2981-9. [PMID: 15579152 DOI: 10.1111/j.1460-9568.2004.03772.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Fast excitatory transmission in the nervous system is mostly mediated by alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors whose subunit composition governs physiological characteristics such as ligand affinity and ion conductance properties. Here, we report that AMPA receptors at inner hair cell (IHC) synapses lack the GluR2 subunit and are transiently Ca2+-permeable before hearing onset as evidenced using agonist-induced Co2+ accumulation, Western blots and GluR2 confocal microscopy in the rat cochlea. AMPA (100 microM) induced Co2+ accumulation in primary auditory neurons until postnatal day (PND) 10. This accumulation was concentration-dependent, strengthened by cyclothiazide (50 microM) and blocked by GYKI 52466 (80 microM) and Joro spider toxin (1 microM). It was unaffected by D-AP5 (50 microM), and it could not be elicited by 56 mM K+ or 1 mM NMDA + 10 microM glycine. Western blots showed that GluR1 immunoreactivity, present in homogenates of immature cochleas, had disappeared by PND12. GluR2 immunoreactivity was not detected until PND10 and GluR3 and GluR4 immunoreactivities were detected at all the ages examined. Confocal microscopy confirmed that the GluR2 immunofluorescence was not located postsynaptically to IHCs before PND10. In conclusion, AMPA receptors on maturing primary auditory neurons differ from those on adult neurons. They are probably composed of GluR1, GluR3 and GluR4 subunits and have a high Ca2+ permeability. The postsynaptic expression of GluR2 subunits may be continuously regulated by the presynaptic activity allowing for variations in the Ca2+ permeability and physiological properties of the receptor.
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Affiliation(s)
- Michel Eybalin
- INSERM U583, Institut des Neurosciences, Hôpital St. Eloi, 80, Avenue Augustin Fliche, BP 74103, 34091 Montpellier cedex 5, France.
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10
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Peng BG, Li QX, Ren TY, Ahmad S, Chen SP, Chen P, Lin X. Group i metabotropic glutamate receptors in spiral ganglion neurons contribute to excitatory neurotransmissions in the cochlea. Neuroscience 2004; 123:221-30. [PMID: 14667457 DOI: 10.1016/j.neuroscience.2003.09.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Evidence has accumulated over the years supporting glutamate as the primary neurotransmitter used by hair cells in afferent cochlear neurotransmission. Besides acting on ionotropic glutamate receptors, glutamate also activates second messenger systems via G-protein-coupled metabotropic glutamate receptors (mGluRs) to modulate neuronal excitability. However, it is unclear whether mGluRs participate in cochlear neurotransmission. We present evidence directly supporting a functional role for group I metabotropic glutamate receptors (mGluRIs) in spiral ganglion (SG) neurons. The presence of mGluRI and downstream G-protein subunits was demonstrated by molecular biology and immunolabeling methods. Direct activation of mGluRIs in cultured SG neurons resulted in transient increases of intracellular Ca(++) concentration and transient inward currents that gave rise to firings of multiple action potentials. These responses showed mGluRI pharmacological specificity and quickly desensitized. We next examined changes in cochlear function after noise exposure as a result of pharmacologically manipulating cochlear glutamate neurotransmission. These in vivo tests showed that blocking non-N-methyl-D-aspartic acid glutamate receptors was sufficient to eliminate compound action potentials of the auditory nerve, and pharmacologically inhibiting mGluRIs in the cochlea did not significantly affect the hearing threshold. In contrast, blocking mGluRIs lowered the amplitude of compound action potentials at louder sound levels and reduced the noise-induced temporary threshold shift. Our results suggest that although mGluRIs did not initiate fast excitatory cochlear neurotransmission, their activation contributed to the growth of excitatory responses of the cochlea. As a result, the cochlea was more resistant to noise-induced temporary hearing losses without the activation of mGluRIs in SG neurons.
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Affiliation(s)
- B G Peng
- Section on Neurobiology, Leslie and Susan Gonda Department of Cell and Molecular Biology, 2100 West Third Street, House Ear Institute, Los Angeles, CA 90057, USA
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11
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Affiliation(s)
- Allen F Ryan
- Department of Surgery/Otolaryngology, University of California San Diego School of Medicine and San Diego Veterans Administration Medical Center, La Jolla, California 92093, USA
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12
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Puyal J, Sage C, Demêmes D, Dechesne CJ. Distribution of alpha-amino-3-hydroxy-5-methyl-4 isoazolepropionic acid and N-methyl-D-aspartate receptor subunits in the vestibular and spiral ganglia of the mouse during early development. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2002; 139:51-7. [PMID: 12414093 DOI: 10.1016/s0165-3806(02)00535-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We investigated the distribution of the glutamate receptor subunits, alpha-amino-3-hydroxy-5-methyl-4 isoazolepropionic acid (AMPA) GluR2 and GluR2/R3, and N-methyl-D-aspartate (NMDA) NR1, and the timing of their appearance during early development of the mouse vestibular and spiral ganglia. NMDA NR1 was the first to be expressed, in the statoacoustic ganglion neurons on E11. GluR2/R3 immunoreactivity was detected in these neurons on E12. This signal probably corresponded exclusively to GluR3, as no signal was obtained for GluR2 alone at this stage. The appearance of these proteins began much earlier than previously reported. GluR2 staining was observed later, on E14 in the vestibular neurons and on E17 in the spiral neurons. The sequence in which these three glutamate receptors appeared suggested possible differences in their roles in the establishment of neuronal circuitry in the inner ear sensory epithelia. The production of NR1 and GluR2/R3 began during the early period of neuron growth and fasciculation. GluR2 appeared later and its expression paralleled synaptogenesis in the vestibular sensory epithelia and in the organ of Corti.
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Affiliation(s)
- Julien Puyal
- INSERM U 432, Université de Montpellier II, UM 2, CC 89, Place Bataillon, 34095 Montpellier cedex 5, France
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13
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Abstract
The neurons of the cochlear ganglion transmit acoustic information between the inner ear and the brain. These placodally derived neurons must produce a topographically precise pattern of connections in both the inner ear and the brain. In this review, we consider the current state of knowledge concerning the development of these neurons, their peripheral and central connections, and their influences on peripheral and central target cells. Relatively little is known about the cellular and molecular regulation of migration or the establishment of precise topographic connection to the hair cells or cochlear nucleus (CN) neurons. Studies of mice with neurotrophin deletions are beginning to yield increasing understanding of variations in ganglion cell survival and resulting innervation patterns, however. Finally, existing evidence suggests that while ganglion cells have little influence on the differentiation of their hair cell targets, quite the opposite is true in the brain. Ganglion cell innervation and synaptic activity are essential for normal development of neurons in the cochlear nucleus.
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Affiliation(s)
- Edwin W Rubel
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology/Head and Neck Surgery, University of Washington, Seattle 98195-7923, USA.
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14
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Eybalin M, Renard N, Aure F, Safieddine S. Cysteine-string protein in inner hair cells of the organ of Corti: synaptic expression and upregulation at the onset of hearing. Eur J Neurosci 2002; 15:1409-20. [PMID: 12028351 DOI: 10.1046/j.1460-9568.2002.01978.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Cysteine-string protein is a vesicle-associated protein that plays a vital function in neurotransmitter release. We have studied its expression and regulation during cochlear maturation. Both the mRNA and the protein were found in primary auditory neurons and the sensory inner hair cells. More importantly, cysteine-string protein was localized on synaptic vesicles associated with the synaptic ribbon in inner hair cells and with presynaptic differentiations in lateral and medial olivocochlear terminals -- the cell bodies of which lie in the auditory brainstem. No cysteine-string protein was expressed by the sensory outer hair cells suggesting that the distinct functions of the two cochlear hair cell types imply different mechanisms of neurotransmitter release. In developmental studies in the rat, we observed that cysteine-string protein was present beneath the inner hair cells at birth and beneath outer hair cells by postnatal day 2 only. We found no expression in the inner hair cells before about postnatal day 12, which corresponds to the period during which the first cochlear action potentials could be recorded. In conclusion, the close association of cysteine-string protein with synaptic vesicles tethered to synaptic ribbons in inner hair cells and its synchronized expression with the appearance and maturation of the cochlear potentials strongly suggest that this protein plays a fundamental role in sound-evoked glutamate release by inner hair cells. This also suggests that this role may be common to ribbon synapses and conventional central nervous system synapses.
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MESH Headings
- Aging/metabolism
- Animals
- Animals, Newborn
- Cell Differentiation/physiology
- Gene Expression Regulation, Developmental/genetics
- Guinea Pigs
- HSP40 Heat-Shock Proteins
- Hair Cells, Auditory, Inner/cytology
- Hair Cells, Auditory, Inner/growth & development
- Hair Cells, Auditory, Inner/metabolism
- Hearing/physiology
- Immunohistochemistry
- Membrane Proteins/genetics
- Membrane Proteins/isolation & purification
- Membrane Proteins/metabolism
- Microscopy, Electron
- Molecular Sequence Data
- Neurotransmitter Agents/metabolism
- Organ of Corti/metabolism
- Organ of Corti/ultrastructure
- Parvalbumins/metabolism
- Presynaptic Terminals/metabolism
- Presynaptic Terminals/ultrastructure
- RNA, Messenger/metabolism
- Rats
- Sequence Homology, Amino Acid
- Spiral Ganglion/metabolism
- Spiral Ganglion/ultrastructure
- Synapses/metabolism
- Synapses/ultrastructure
- Synaptic Transmission/physiology
- Synaptic Vesicles/metabolism
- Synaptic Vesicles/ultrastructure
- Synaptophysin/metabolism
- Up-Regulation/physiology
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Affiliation(s)
- Michel Eybalin
- INSERM U. 254 and Université Montpellier 1, 34090 Montpellier, France.
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15
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Abstract
Before mice start to hear at approximately postnatal day 10, their cochlear inner hair cells (IHCs) spontaneously generate Ca(2+) action potentials. Therefore, immature IHCs could stimulate the auditory pathway, provided that they were already competent for transmitter release. Here, we combined patch-clamp capacitance measurements and fluorimetric [Ca(2+)](i) recordings to study the presynaptic function of IHCs during cochlear maturation. Ca(2+)-dependent exocytosis and subsequent endocytic membrane retrieval were already observed near the date of birth. Ca(2+) action potentials triggered exocytosis in immature IHCs, which probably activates the auditory pathway before it becomes responsive to sound. IHCs underwent profound changes in Ca(2+)-channel expression and secretion during their postnatal development. Ca(2+)-channel expression increased toward the end of the first week, providing for large secretory responses during this period and thereafter declined to reach mature levels. The efficacy whereby Ca(2+) influx triggers exocytosis increased toward maturation, such that vesicle fusion caused by a given Ca(2+) current occurred faster in mature IHCs. The observed changes in Ca(2+)-channel expression and synaptic efficacy probably reflected the ongoing synaptogenesis in IHCs that had been described previously in morphological studies.
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16
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Abstract
The ionotropic glutamate receptor (GluR) subtype known as the AMPA receptor, which mediates rapid excitatory synaptic transmission in many regions of the nervous system, is composed of four different protein subunits, termed GluRs 1-4. The functional properties of each AMPA receptor are determined by the relative levels of GluRs 1-4 and by post-transcriptional modifications of these proteins through mRNA editing and alternative exon splicing. The present paper reviews the published evidence for (1) localization of mRNAs and immunoreactivity for GluRs 1-4 in the cochlea and subcortical central nervous system auditory pathways of mammals and birds, and (2) involvement of AMPA receptors in synaptic transmission in the auditory system. Recent biochemical and electrophysiological evidence concerning the specialized properties of AMPA receptors on brainstem auditory neurons is also reviewed, along with data concerning how these properties emerge during normal development.
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Affiliation(s)
- T N Parks
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.
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17
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Hasegawa T, Doi K, Fuse Y, Fujii K, Uno Y, Nishimura H, Kubo T. Deafness induced up-regulation of GluR2/3 and NR1 in the spiral ganglion cells of the rat cochlea. Neuroreport 2000; 11:2515-9. [PMID: 10943714 DOI: 10.1097/00001756-200008030-00034] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Expressions of AMPA (GluR2, GluR3, and GluR4) and NMDA (NR1 and NR2) glutamate receptors in the spiral ganglion cells of the cochlea were analyzed both at protein and mRNA levels in control and deaf rats between week 0 (P14) and week 8 (P70) after deafness induced by a daily injection of kanamycin at P0-P14. In the deaf rats, significant up-regulations of GluR2, GluR3, and NR1 in the surviving spiral ganglion cells were observed, while expressions of GluR4 and NR2 were fairly constant. In contrast, in the control rats, the expressions of all these glutamate receptor subtypes were stable. These results suggest that drastic alterations in the diversity of GluR2/GluR3/NR1 receptor complexes in the surviving spiral ganglion cells, which result in alterations in Ca2+ permeability, may contribute to the deafness-related alterations in the structure and function of the cochlea.
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MESH Headings
- Age Factors
- Animals
- Animals, Newborn
- Cell Count/statistics & numerical data
- Deafness/chemically induced
- Deafness/metabolism
- Deafness/physiopathology
- Kainic Acid/pharmacology
- Nerve Degeneration/chemically induced
- Nerve Degeneration/metabolism
- Nerve Degeneration/physiopathology
- Polymerase Chain Reaction/methods
- RNA, Messenger/drug effects
- RNA, Messenger/metabolism
- Rats
- Rats, Sprague-Dawley
- Receptors, AMPA/drug effects
- Receptors, AMPA/genetics
- Receptors, AMPA/metabolism
- Receptors, N-Methyl-D-Aspartate/drug effects
- Receptors, N-Methyl-D-Aspartate/genetics
- Receptors, N-Methyl-D-Aspartate/metabolism
- Spiral Ganglion/drug effects
- Spiral Ganglion/metabolism
- Spiral Ganglion/pathology
- Spiral Ganglion/physiopathology
- Up-Regulation/drug effects
- Up-Regulation/physiology
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Affiliation(s)
- T Hasegawa
- Department of Otolaryngology and Sensory Organ Surgery, Osaka University Graduate School of Medicine, Suita, Japan
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18
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Ross KC, Coleman JR. Developmental and genetic audiogenic seizure models: behavior and biological substrates. Neurosci Biobehav Rev 2000; 24:639-53. [PMID: 10940439 DOI: 10.1016/s0149-7634(00)00029-4] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Audiogenic seizure (AGS) models of developmental or genetic origin manifest characteristic indices of generalized seizures such as clonus or tonus in rodents. Studies of seizure-resistant strains in which AGS is induced by intense sound exposure during postnatal development provide models in which other neural abnormalities are not introduced along with AGS susceptibility. A critical feature of all AGS models is the reduction of neural activity in the auditory pathways from deafness during development. The initiation and propagation of AGS activity relies upon hyperexcitability in the auditory system, particularly the inferior colliculus (IC) where bilateral lesions abolish AGS. GABAergic and glutaminergic mechanisms play crucial roles in AGS, as in temporal lobe models of epilepsy, and participate in AGS modulatory and efferent systems including the superior colliculus, substantia nigra, basal ganglia and structures of the reticular formation. Catecholamine and indolamine systems also influence AGS severity. AGS models are useful for elucidating the underlying mechanisms for formation and expression of generalized epileptic behaviors, and evaluating the efficacy of modern treatment strategies such as anticonvulsant medication and neural grafting.
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Affiliation(s)
- K C Ross
- Department of Psychology, University of South Carolina, Columbia, SC 29208, USA
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19
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Järlebark LE, Housley GD, Thorne PR. Immunohistochemical localization of adenosine 5'-triphosphate-gated ion channel P2X(2) receptor subunits in adult and developing rat cochlea. J Comp Neurol 2000; 421:289-301. [PMID: 10813788 DOI: 10.1002/(sici)1096-9861(20000605)421:3<289::aid-cne1>3.0.co;2-0] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Substantial in vitro and in vivo data support a role for extracellular adenosine 5;-triphosphate (ATP) and associated P2 receptors in cochlear function. However, the precise spatiotemporal distribution of the involved receptor protein(s) has not been determined. By using a specific antiserum and immunoperoxidase labeling, the tissue distribution of the P2X(2) subunit of the ATP-gated ion channel was investigated. Here, we describe the first extensive immunohistochemical mapping of P2X(2) receptor subunits in the adult and developing rat cochlea. In the adult, immunoreactivity was observed in most cells bordering on the endolymphatic compartment (scala media), particularly in the supporting cells. Hair cells were not immunostained by the P2X(2) antiserum, except for outer hair cell stereocilia. In addition, weak immunolabeling was observed in some spiral ganglion neurons. P2X(2) receptor subunit protein expression during labyrinthine ontogeny was detected first on embryonic day 19 in the spiral ganglion and in associated nerve fibers extending to the inner hair cells. Immunostaining also was observed underneath outer hair cells, and, by postnatal day 6 (P6), intense immunolabeling was seen in the synaptic regions of both types of hair cell. Supporting cells of the sensory epithelium were labeled at P0. This labeling became most prominent from the onset of cochlear function (P8-P12). Conversely, expression in the vascular stria declined from this time. By P21, the pattern of immunolabeling was similar to that found in the adult. The localization and timing of P2X(2) immunoreactivity suggest involvement of extracellular ATP and associated ATP-gated ion channels in important physiological events, such as inner ear ontogeny, sound transduction, cochlear micromechanics, electrochemical homeostasis, and auditory neurotransmission.
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MESH Headings
- Adenosine Triphosphate/metabolism
- Animals
- Cochlea/growth & development
- Cochlea/metabolism
- Female
- Hair Cells, Auditory, Inner/growth & development
- Hair Cells, Auditory, Inner/metabolism
- Hair Cells, Auditory, Outer/growth & development
- Hair Cells, Auditory, Outer/metabolism
- Ion Channels/metabolism
- Pregnancy
- Rats
- Rats, Wistar
- Receptors, Purinergic P2/metabolism
- Receptors, Purinergic P2X2
- Spiral Ganglion/growth & development
- Spiral Ganglion/metabolism
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Affiliation(s)
- L E Järlebark
- Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand
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20
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Chapter IX Glutamate neurotransmission in the mammalian inner ear. ACTA ACUST UNITED AC 2000. [DOI: 10.1016/s0924-8196(00)80050-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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21
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Housley GD, Luo L, Ryan AF. Localization of mRNA encoding the P2X2 receptor subunit of the adenosine 5?-triphosphate-gated ion channel in the adult and developing rat inner ear by in situ hybridization. J Comp Neurol 1998. [DOI: 10.1002/(sici)1096-9861(19980420)393:4<403::aid-cne1>3.0.co;2-4] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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22
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d'Aldin C, Caicedo A, Ruel J, Renard N, Pujol R, Puel JL. Antisense oligonucleotides to the GluR2 AMPA receptor subunit modify excitatory synaptic transmission in vivo. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1998; 55:151-64. [PMID: 9645970 DOI: 10.1016/s0169-328x(97)00352-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
In the brain, fast wxcitatory synaptic transmission is mostly mediated by the alpha-amino-3-hydroxy-5-methyl-isoxazole-propionic acid (AMPA) subtype of the glutamate receptors. Molecular cloning has revealed that four subunits, GluR1, GluR2, GluR3, and GluR4 form heteromeric receptors with high affinity for AMPA. Because antagonists and agonists do not discriminate between individual AMPA receptor subunits, we decided to use antisense oligonucleotides to block the expression of the GluR2 subunit within the receptor complex in adult animals. In the present study, we exploited several advantages afforded by the guinea pig cochlea to determine whether an antisense oligonucleotide directed to the mRNA of the GluR2 subunit could modify primary auditory neurotransmission. While a random probe with the same base composition had no effect, a GluR2 antisense oligonucleotide, continuously delivered into the cochlea, transiently reduced the compound action potential and diminished spontaneous activity of single auditory nerve fibers. Although antisense oligonucleotides penetrated a variety of cells, their effect could be physiologically localized to a single site of GluR2 antisense probe action, the primary auditory neuron. Subunit specificity of this effect was confirmed by a significant reduction in GluR2/3, but not GluR4 immunoreactivity in primary auditory neurons. Besides being the first demonstration that transient knockout of GluR2 subunit in adult animal modifies excitatory synaptic transmission in vivo, these results support the use of the antisense strategy as a powerful tool for blocking expression of any gene in the cochlea.
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MESH Headings
- Acoustic Stimulation
- Action Potentials/drug effects
- Animals
- Audiometry, Pure-Tone
- Cloning, Molecular
- Cochlear Nerve/physiology
- Diffusion
- Drug Delivery Systems
- Guinea Pigs
- Hair Cells, Auditory, Inner/drug effects
- Hair Cells, Auditory, Inner/physiology
- Nerve Tissue Proteins/antagonists & inhibitors
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/physiology
- Oligonucleotides, Antisense/administration & dosage
- Oligonucleotides, Antisense/genetics
- Oligonucleotides, Antisense/pharmacokinetics
- Oligonucleotides, Antisense/pharmacology
- Perilymph
- Receptors, AMPA/antagonists & inhibitors
- Receptors, AMPA/genetics
- Receptors, AMPA/physiology
- Synaptic Transmission/drug effects
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Affiliation(s)
- C d'Aldin
- INSERM U.254 Université Montpellier I, Laboratoire de Neurobiologie de l'Audition, Plasticité Synaptique, CHR Saint Charles, Montpellier, France
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23
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Pujol R, Lavigne-Rebillard M, Lenoir M. Development of Sensory and Neural Structures in the Mammalian Cochlea. DEVELOPMENT OF THE AUDITORY SYSTEM 1998. [DOI: 10.1007/978-1-4612-2186-9_4] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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