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Olthof BMJ, Lyzwa D, Gartside SE, Rees A. Nitric oxide signalling underlies salicylate-induced increases in neuronal firing in the inferior colliculus: A central mechanism of tinnitus? Hear Res 2022; 424:108585. [DOI: 10.1016/j.heares.2022.108585] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 06/17/2022] [Accepted: 07/21/2022] [Indexed: 11/16/2022]
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2
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Can GABAkines Quiet the Noise? The GABAA Receptor Neurobiology and Pharmacology of Tinnitus. Biochem Pharmacol 2022; 201:115067. [DOI: 10.1016/j.bcp.2022.115067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 04/21/2022] [Accepted: 04/25/2022] [Indexed: 11/20/2022]
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3
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Cerrah Gunes M, Gunes MS, Vural A, Aybuga F, Bayram A, Bayram KK, Sahin MI, Dogan ME, Ozdemir SY, Ozkul Y. Change in gene expression levels of GABA, glutamate and neurosteroid pathways due to acoustic trauma in the cochlea. J Neurogenet 2021; 35:45-57. [PMID: 33825593 DOI: 10.1080/01677063.2021.1904922] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The characteristic feature of noise-induced hearing loss (NIHL) is the loss or malfunction of the outer hair cells (OHC) and the inner hair cells (IHC) of the cochlea. 90-95% of the spiral ganglion neurons, forming the cell bodies of cochlear nerve, synapse with the IHCs. Glutamate is the most potent excitatory neurotransmitter for IHC-auditory nerve synapses. Excessive release of glutamate in response to acoustic trauma (AT), may cause excitotoxicity by causing damage to the spiral ganglion neurons (SGN) or loss of the spiral ganglion dendrites, post-synaptic to the IHCs. Another neurotransmitter, GABA, plays an important role in the processing of acoustic stimuli and central regulation after peripheral injury, so it is potentially related to the regulation of hearing function and sensitivity after noise. The aim of this study is to evaluate the effect of AT on the expressions of glutamate excitotoxicity, GABA inhibition and neurosteroid synthesis genes.We exposed 24 BALB/c mice to AT. Controls were sacrificed without exposure to noise, Post-AT(1) and Post-AT(15) were sacrificed on the 1st and 15th day, respectively, after noise exposure. The expressions of various genes playing roles in glutamate, GABA and neurosteroid pathways were compared between groups by real-time PCR.Expressions of Cyp11a1, Gls, Gabra1, Grin2b, Sult1a1, Gad1, and Slc1a2 genes in Post-AT(15) mice were significantly decreased in comparison to control and Post-AT(1) mice. No significant differences in the expression of Slc6a1 and Slc17a8 genes was detected.These findings support the possible role of balance between glutamate excitotoxicity and GABA inhibition is disturbed during the post AT days and also the synthesis of some neurosteroids such as pregnenolone sulfate may be important in this balance.
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Affiliation(s)
- Meltem Cerrah Gunes
- Department of Medical Genetics, School of Medicine, Erciyes University, Kayseri, Turkey
| | - Murat Salih Gunes
- Department of Otolaryngology, Izmit Seka State Hospital, Kocaeli, Turkey
| | - Alperen Vural
- Department of Otolaryngology, School of Medicine, Erciyes University, Kayseri, Turkey
| | | | - Arslan Bayram
- Etlik Zübeyde Hanım Women's Diseases Education and Research Hospital, Health Sciences University, T.R. Ministry of Health, Ankara, Turkey
| | - Keziban Korkmaz Bayram
- Department of Medical Genetics, School of Medicine, Yıldirim Beyazit University, Ankara, Turkey
| | - Mehmet Ilhan Sahin
- Department of Otolaryngology, School of Medicine, Erciyes University, Kayseri, Turkey
| | - Muhammet Ensar Dogan
- Department of Medical Genetics, School of Medicine, Erciyes University, Kayseri, Turkey
| | - Sevda Yesim Ozdemir
- Department of Medical Genetics, School of Medicine, Uskudar University, Istanbul, Turkey
| | - Yusuf Ozkul
- Department of Medical Genetics, School of Medicine, Erciyes University, Kayseri, Turkey.,Center of Genome and Stem Cell, Kayseri, Turkey
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4
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Manohar S, Russo FY, Seigel GM, Salvi R. Dynamic Changes in Synaptic Plasticity Genes in Ipsilateral and Contralateral Inferior Colliculus Following Unilateral Noise-induced Hearing Loss. Neuroscience 2020; 436:136-153. [PMID: 32278721 DOI: 10.1016/j.neuroscience.2020.04.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 03/07/2020] [Accepted: 04/03/2020] [Indexed: 12/27/2022]
Abstract
Unilateral noise-induced hearing loss reduces the input to the central auditory pathway disrupting the excitatory and inhibitory inputs to the inferior colliculus (IC), an important binaural processing center. Little is known about the compensatory synaptic changes that occur in the IC as a consequence of unilateral noise-induced hearing loss. To address this issue, Sprague-Dawley rats underwent unilateral noise exposure resulting in severe unilateral hearing loss. IC tissues from the contralateral and ipsilateral IC were evaluated for acute (2-d) and chronic (28-d) changes in the expression of 84 synaptic plasticity genes on a PCR array. Arc and Egr1 genes were further visualized by in situ hybridization to validate the PCR results. None of the genes were upregulated, but many were downregulated post-exposure. At 2-d post-exposure, more than 75% of the genes were significantly downregulated in the contralateral IC, while only two were downregulated in the ipsilateral IC. Many of the downregulated genes were related to long-term depression, long-term potentiation, cell adhesion, immediate early genes, neural receptors and postsynaptic density. At 28-d post-exposure, the gene expression pattern was reversed with more than 85% of genes in the ipsilateral IC now downregulated. Most genes previously downregulated in the contralateral IC 2-d post-exposure had recovered; less than 15% remained downregulated. These time-dependent, asymmetric changes in synaptic plasticity gene expression could shed new light on the perceptual deficits associated with unilateral hearing loss and the dynamic structural and functional changes that occur in the IC days and months following unilateral noise-induced hearing loss.
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Affiliation(s)
| | | | - Gail M Seigel
- Center for Hearing and Deafness, University at Buffalo, Buffalo, NY 14214, USA
| | - Richard Salvi
- Center for Hearing and Deafness, University at Buffalo, Buffalo, NY 14214, USA.
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Zhou M, Yuan J, Yan Z, Dai J, Wang X, Xu T, Xu Z, Wang N, Liu J. Intrinsic and Miniature Postsynaptic Current Changes in Rat Principal Neurons of the Lateral Superior Olive after Unilateral Auditory Deprivation at an Early Age. Neuroscience 2019; 428:2-12. [PMID: 31866557 DOI: 10.1016/j.neuroscience.2019.12.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2019] [Revised: 11/30/2019] [Accepted: 12/02/2019] [Indexed: 01/13/2023]
Abstract
Unilateral auditory deprivation results in lateralization changes in the central auditory system, interfering with the integration of binaural information and thereby leading to a decrease in binaural auditory functions such as sound localization. Principal neurons of the lateral superior olive (LSO) are responsible for computing the interaural intensity differences that are critical for sound localization in the horizontal plane. To investigate changes caused by unilateral auditory deprivation, electrophysiological activity was recorded from LSO principal neurons in control rats and rats with unilateral cochlear ablation. At one week after unilateral cochlear ablation, the excitability of LSO principal neurons on the side ipsilateral to the ablation (the ablated side) was greater than that on the side contralateral to the ablation (the intact side); however, the input resistance increased on both sides. Furthermore, by analysing the miniature inhibitory postsynaptic currents and miniature excitatory postsynaptic currents, we found that unilateral auditory deprivation weakened the inhibitory driving force on the intact side, whereas it strengthened the excitatory driving force on the ablated side. In summary, asymmetric changes in the electrophysiological activity of LSO principal neurons were found on both sides at postnatal day 19, one week after unilateral cochlear ablation.
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Affiliation(s)
- Mo Zhou
- Department of Otorhinolaryngology Head and Neck Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China
| | - Jingjing Yuan
- Department of Otorhinolaryngology Head and Neck Surgery, Beijing Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
| | - Zhanfeng Yan
- Department of Otorhinolaryngology Head and Neck Surgery, Beijing Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
| | - Jinsheng Dai
- Department of Otorhinolaryngology Head and Neck Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China
| | - Xing Wang
- Department of Otorhinolaryngology Head and Neck Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China
| | - Tao Xu
- Department of Neurobiology, Beijing Key Laboratory of Neural Regeneration and Repair, Beijing Laboratory of Brain Disorders (Ministry of Science and Technology), Beijing Institute of Brain Disorders, Capital Medical University, Beijing, China
| | - Zhiqing Xu
- Department of Neurobiology, Beijing Key Laboratory of Neural Regeneration and Repair, Beijing Laboratory of Brain Disorders (Ministry of Science and Technology), Beijing Institute of Brain Disorders, Capital Medical University, Beijing, China
| | - Ningyu Wang
- Department of Otorhinolaryngology Head and Neck Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China.
| | - Jinfeng Liu
- Department of Otorhinolaryngology Head and Neck Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China.
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Presacco A, Simon JZ, Anderson S. Speech-in-noise representation in the aging midbrain and cortex: Effects of hearing loss. PLoS One 2019; 14:e0213899. [PMID: 30865718 PMCID: PMC6415857 DOI: 10.1371/journal.pone.0213899] [Citation(s) in RCA: 62] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 03/04/2019] [Indexed: 01/24/2023] Open
Abstract
Age-related deficits in speech-in-noise understanding pose a significant problem for older adults. Despite the vast number of studies conducted to investigate the neural mechanisms responsible for these communication difficulties, the role of central auditory deficits, beyond peripheral hearing loss, remains unclear. The current study builds upon our previous work that investigated the effect of aging on normal-hearing individuals and aims to estimate the effect of peripheral hearing loss on the representation of speech in noise in two critical regions of the aging auditory pathway: the midbrain and cortex. Data from 14 hearing-impaired older adults were added to a previously published dataset of 17 normal-hearing younger adults and 15 normal-hearing older adults. The midbrain response, measured by the frequency-following response (FFR), and the cortical response, measured with the magnetoencephalography (MEG) response, were recorded from subjects listening to speech in quiet and noise conditions at four signal-to-noise ratios (SNRs): +3, 0, -3, and -6 dB sound pressure level (SPL). Both groups of older listeners showed weaker midbrain response amplitudes and overrepresentation of cortical responses compared to younger listeners. No significant differences were found between the two older groups when the midbrain and cortical measurements were analyzed independently. However, significant differences between the older groups were found when investigating the midbrain-cortex relationships; that is, only hearing-impaired older adults showed significant correlations between midbrain and cortical measurements, suggesting that hearing loss may alter reciprocal connections between lower and higher levels of the auditory pathway. The overall paucity of differences in midbrain or cortical responses between the two older groups suggests that age-related temporal processing deficits may contribute to older adults' communication difficulties beyond what might be predicted from peripheral hearing loss alone; however, hearing loss does seem to alter the connectivity between midbrain and cortex. These results may have important ramifications for the field of audiology, as it indicates that algorithms in clinical devices, such as hearing aids, should consider age-related temporal processing deficits to maximize user benefit.
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Affiliation(s)
- Alessandro Presacco
- Department of Otolaryngology, University of California, Irvine, CA, United States of America
- Center for Hearing Research, University of California, Irvine, CA, United States of America
- * E-mail:
| | - Jonathan Z. Simon
- Department of Electrical & Computer Engineering, University of Maryland, College Park, MD, United States of America
- Department of Biology, University of Maryland, College Park, MD, United States of America
- Institute for Systems Research, University of Maryland, College Park, MD, United States of America
- Neuroscience and Cognitive Science Program, University of Maryland, College Park, MD, United States of America
| | - Samira Anderson
- Neuroscience and Cognitive Science Program, University of Maryland, College Park, MD, United States of America
- Department of Hearing and Speech Sciences, University of Maryland, College Park, MD, United States of America
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Corelease of Inhibitory Neurotransmitters in the Mouse Auditory Midbrain. J Neurosci 2017; 37:9453-9464. [PMID: 28847813 DOI: 10.1523/jneurosci.1125-17.2017] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Revised: 08/07/2017] [Accepted: 08/23/2017] [Indexed: 11/21/2022] Open
Abstract
The central nucleus of the inferior colliculus (ICC) of the auditory midbrain, which integrates most ascending auditory information from lower brainstem regions, receives prominent long-range inhibitory input from the ventral nucleus of the lateral lemniscus (VNLL), a region thought to be important for temporal pattern discrimination. Histological evidence suggests that neurons in the VNLL release both glycine and GABA in the ICC, but functional evidence for their corelease is lacking. We took advantage of the GlyT2-Cre mouse line (both male and female) to target expression of ChR2 to glycinergic afferents in the ICC and made whole-cell recordings in vitro while exciting glycinergic fibers with light. Using this approach, it was clear that a significant fraction of glycinergic boutons corelease GABA in the ICC. Viral injections were used to target ChR2 expression specifically to glycinergic fibers ascending from the VNLL, allowing for activation of fibers from a single source of ascending input in a way that has not been previously possible in the ICC. We then investigated aspects of the glycinergic versus GABAergic current components to probe functional consequences of corelease. Surprisingly, the time course and short-term plasticity of synaptic signaling were nearly identical for the two transmitters. We therefore conclude that the two neurotransmitters may be functionally interchangeable and that multiple receptor subtypes subserving inhibition may offer diverse mechanisms for maintaining inhibitory homeostasis.SIGNIFICANCE STATEMENT Corelease of neurotransmitters is a common feature of the brain. GABA and glycine corelease is particularly common in the spinal cord and brainstem, but its presence in the midbrain is unknown. We show corelease of GABA and glycine for the first time in the central nucleus of the inferior colliculus of the auditory midbrain. Glycine and GABA are both inhibitory neurotransmitters involved in fast synaptic transmission, so we explored differences between the currents to establish a physiological foundation for functional differences in vivo In contrast to the auditory brainstem, coreleased GABAergic and glycinergic currents in the midbrain are strikingly similar. This apparent redundancy may ensure homeostasis if one neurotransmitter system is compromised.
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8
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Acquired hearing loss and brain plasticity. Hear Res 2017; 343:176-190. [DOI: 10.1016/j.heares.2016.05.008] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 04/29/2016] [Accepted: 05/19/2016] [Indexed: 12/19/2022]
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9
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Gauvin DV, Yoder JD, Tapp RL, Baird TJ. Small Compartment Toxicity: CN VIII and Quality of Life: Hearing Loss, Tinnitus, and Balance Disorders. Int J Toxicol 2017; 36:8-20. [PMID: 27194512 DOI: 10.1177/1091581816648905] [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: 11/16/2022]
Abstract
Life experiences, industrial/environmental exposures, and administration of Food and Drug Administration (FDA)-approved drugs may have unintended but detrimental effects on peripheral and central auditory pathways. Most relevant to the readership of this journal is the role that drug treatments approved by the FDA as safe and effective appear to interact with 3 independent modes of toxicity within the small compartment of the ear. What may seem to be trivial drug-induced toxicity has the potential to change important measures of quality of life and functional capacity of mid- to late-life patients. Drugs meant to treat can become the source of interference in the activities of daily living, and as a result, treatment compliance may be jeopardized. Ototoxicity has been defined as the tendency of certain therapeutic agents and other chemical substances to cause functional impairments and cellular degeneration of the tissues of the inner ear resulting in hearing loss. However, one of the largest contributors to hospitalizations is fall-related injuries in the elderly patients associated with disorders of vestibular function linked to progressive and drug-induced toxicities. Tinnitus affects 35 to 50 million adults representing approximately 25% of the US population, with 12 million seeking medical care and 2 to 3 million reporting symptoms that were severely debilitating. This review is intended to highlight these targets of neurotoxicity that threaten the usefulness of drug treatments deemed safe and effective prior to access by the general public.
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Affiliation(s)
- David V Gauvin
- Neurobehavioral Sciences, MPI Research Inc, Mattawan, MI, USA
| | - Joshua D Yoder
- Neurobehavioral Sciences, MPI Research Inc, Mattawan, MI, USA
| | - Rachel L Tapp
- Neurobehavioral Sciences, MPI Research Inc, Mattawan, MI, USA
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10
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Eggermont JJ. Can Animal Models Contribute to Understanding Tinnitus Heterogeneity in Humans? Front Aging Neurosci 2016; 8:265. [PMID: 27895575 PMCID: PMC5107573 DOI: 10.3389/fnagi.2016.00265] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 10/24/2016] [Indexed: 12/30/2022] Open
Abstract
The brain activity of humans with tinnitus of various etiologies is typically studied with electro- and magneto-encephalography and functional magnetic resonance imaging-based imaging techniques. Consequently, they measure population responses and mostly from the neocortex. The latter also underlies changes in neural networks that may be attributed to tinnitus. However, factors not strictly related to tinnitus such as hearing loss and hyperacusis, as well as other co-occurring disorders play a prominent role in these changes. Different types of tinnitus can often not be resolved with these brain-imaging techniques. In animal models of putative behavioral signs of tinnitus, neural activity ranging from auditory nerve to auditory cortex, is studied largely by single unit recordings, augmented by local field potentials (LFPs), and the neural correlates of tinnitus are mainly based on spontaneous neural activity, such as spontaneous firing rates and pair-wise spontaneous spike-firing correlations. Neural correlates of hyperacusis rely on measurement of stimulus-evoked activity and are measured as increased driven firing rates and LFP amplitudes. Connectivity studies would rely on correlated neural activity between pairs of neurons or LFP amplitudes, but are only recently explored. In animal models of tinnitus, only two etiologies are extensively studied; tinnitus evoked by salicylate application and by noise exposure. It appears that they have quite different neural biomarkers. The unanswered question then is: does this different etiology also result in different tinnitus?
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Affiliation(s)
- Jos J Eggermont
- Department of Physiology and Pharmacology, University of Calgary, CalgaryAB, Canada; Department of Psychology, University of Calgary, CalgaryAB, Canada
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11
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Clarkson C, Antunes FM, Rubio ME. Conductive Hearing Loss Has Long-Lasting Structural and Molecular Effects on Presynaptic and Postsynaptic Structures of Auditory Nerve Synapses in the Cochlear Nucleus. J Neurosci 2016; 36:10214-27. [PMID: 27683915 PMCID: PMC5039262 DOI: 10.1523/jneurosci.0226-16.2016] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Revised: 08/03/2016] [Accepted: 08/12/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Sound deprivation by conductive hearing loss increases hearing thresholds, but little is known about the response of the auditory brainstem during and after conductive hearing loss. Here, we show in young adult rats that 10 d of monaural conductive hearing loss (i.e., earplugging) leads to hearing deficits that persist after sound levels are restored. Hearing thresholds in response to clicks and frequencies higher than 8 kHz remain increased after a 10 d recovery period. Neural output from the cochlear nucleus measured at 10 dB above threshold is reduced and followed by an overcompensation at the level of the lateral lemniscus. We assessed whether structural and molecular substrates at auditory nerve (endbulb of Held) synapses in the cochlear nucleus could explain these long-lasting changes in hearing processing. During earplugging, vGluT1 expression in the presynaptic terminal decreased and synaptic vesicles were smaller. Together, there was an increase in postsynaptic density (PSD) thickness and an upregulation of GluA3 AMPA receptor subunits on bushy cells. After earplug removal and a 10 d recovery period, the density of synaptic vesicles increased, vesicles were also larger, and the PSD of endbulb synapses was larger and thicker. The upregulation of the GluA3 AMPAR subunit observed during earplugging was maintained after the recovery period. This suggests that GluA3 plays a role in plasticity in the cochlear nucleus. Our study demonstrates that sound deprivation has long-lasting alterations on structural and molecular presynaptic and postsynaptic components at the level of the first auditory nerve synapse in the auditory brainstem. SIGNIFICANCE STATEMENT Despite being the second most prevalent form of hearing loss, conductive hearing loss and its effects on central synapses have received relatively little attention. Here, we show that 10 d of monaural conductive hearing loss leads to an increase in hearing thresholds, to an increased central gain upstream of the cochlear nucleus at the level of the lateral lemniscus, and to long-lasting presynaptic and postsynaptic structural and molecular effects at the endbulb of the Held synapse. Knowledge of the structural and molecular changes associated with decreased sensory experience, along with their potential reversibility, is important for the treatment of hearing deficits, such as hyperacusis and chronic otitis media with effusion, which is prevalent in young children with language acquisition or educational disabilities.
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Affiliation(s)
| | | | - Maria E Rubio
- Departments of Otolaryngology and Neurobiology and Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
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12
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Tighilet B, Dutheil S, Siponen MI, Noreña AJ. Reactive Neurogenesis and Down-Regulation of the Potassium-Chloride Cotransporter KCC2 in the Cochlear Nuclei after Cochlear Deafferentation. Front Pharmacol 2016; 7:281. [PMID: 27630564 PMCID: PMC5005331 DOI: 10.3389/fphar.2016.00281] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 08/16/2016] [Indexed: 12/26/2022] Open
Abstract
While many studies have been devoted to investigating the homeostatic plasticity triggered by cochlear hearing loss, the cellular and molecular mechanisms involved in these central changes remain elusive. In the present study, we investigated the possibility of reactive neurogenesis after unilateral cochlear nerve section in the cochlear nucleus (CN) of cats. We found a strong cell proliferation in all the CN sub-divisions ipsilateral to the lesion. Most of the newly generated cells survive up to 1 month after cochlear deafferentation in all cochlear nuclei (except the dorsal CN) and give rise to a variety of cell types, i.e., microglial cells, astrocytes, and neurons. Interestingly, many of the newborn neurons had an inhibitory (GABAergic) phenotype. This result is intriguing since sensory deafferentation is usually accompanied by enhanced excitation, consistent with a reduction in central inhibition. The membrane potential effect of GABA depends, however, on the intra-cellular chloride concentration, which is maintained at low levels in adults by the potassium chloride co-transporter KCC2. The KCC2 density on the plasma membrane of neurons was then assessed after cochlear deafferentation in the cochlear nuclei ipsilateral and contralateral to the lesion. Cochlear deafferentation is accompanied by a strong down-regulation of KCC2 ipsilateral to the lesion at 3 and 30 days post-lesion. This study suggests that reactive neurogenesis and down-regulation of KCC2 is part of the vast repertoire involved in homeostatic plasticity triggered by hearing loss. These central changes may also play a role in the generation of tinnitus and hyperacusis.
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Affiliation(s)
- Brahim Tighilet
- Laboratoire de Neurosciences Intégratives et Adaptatives, UMR 7260 - Comportement, Cerveau, Cognition (Behavior, Brain, and Cognition) - Aix-Marseille Université - Centre National de la Recherche Scientifique Marseille, France
| | - Sophie Dutheil
- Department of Psychiatry, School of Medicine, Yale University, New Haven CT, USA
| | - Marina I Siponen
- Laboratoire de Neurosciences Intégratives et Adaptatives, UMR 7260 - Comportement, Cerveau, Cognition (Behavior, Brain, and Cognition) - Aix-Marseille Université - Centre National de la Recherche Scientifique Marseille, France
| | - Arnaud J Noreña
- Laboratoire de Neurosciences Intégratives et Adaptatives, UMR 7260 - Comportement, Cerveau, Cognition (Behavior, Brain, and Cognition) - Aix-Marseille Université - Centre National de la Recherche Scientifique Marseille, France
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13
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Manohar S, Dahar K, Adler HJ, Dalian D, Salvi R. Noise-induced hearing loss: Neuropathic pain via Ntrk1 signaling. Mol Cell Neurosci 2016; 75:101-12. [PMID: 27473923 DOI: 10.1016/j.mcn.2016.07.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 06/30/2016] [Accepted: 07/25/2016] [Indexed: 12/18/2022] Open
Abstract
Severe noise-induced damage to the inner ear leads to auditory nerve fiber degeneration thereby reducing the neural input to the cochlear nucleus (CN). Paradoxically, this leads to a significant increase in spontaneous activity in the CN which has been linked to tinnitus, hyperacusis and ear pain. The biological mechanisms that lead to an increased spontaneous activity are largely unknown, but could arise from changes in glutamatergic or GABAergic neurotransmission or neuroinflammation. To test this hypothesis, we unilaterally exposed rats for 2h to a 126dB SPL narrow band noise centered at 12kHz. Hearing loss measured by auditory brainstem responses exceeded 55dB from 6 to 32kHz. The mRNA from the exposed CN was harvested at 14 or 28days post-exposure and qRT-PCR analysis was performed on 168 genes involved in neural inflammation, neuropathic pain and glutamatergic or GABAergic neurotransmission. Expression levels of mRNA of Slc17a6 and Gabrg3, involved in excitation and inhibition respectively, were significantly increased at 28days post-exposure, suggesting a possible role in the CN spontaneous hyperactivity associated with tinnitus and hyperacusis. In the pain and inflammatory array, noise exposure upregulated mRNA expression levels of four pain/inflammatory genes, Tlr2, Oprd1, Kcnq3 and Ntrk1 and decreased mRNA expression levels of two more genes, Ccl12 and Il1β. Pain/inflammatory gene expression changes via Ntrk1 signaling may induce sterile inflammation, neuropathic pain, microglial activation and migration of nerve fibers from the trigeminal, cuneate and vestibular nuclei into the CN. These changes could contribute to somatic tinnitus, hyperacusis and otalgia.
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Affiliation(s)
- Senthilvelan Manohar
- Center for Hearing & Deafness, State University of New York at Buffalo, Buffalo, NY 14214, United States.
| | - Kimberly Dahar
- Center for Hearing & Deafness, State University of New York at Buffalo, Buffalo, NY 14214, United States
| | - Henry J Adler
- Center for Hearing & Deafness, State University of New York at Buffalo, Buffalo, NY 14214, United States
| | - Ding Dalian
- Center for Hearing & Deafness, State University of New York at Buffalo, Buffalo, NY 14214, United States
| | - Richard Salvi
- Center for Hearing & Deafness, State University of New York at Buffalo, Buffalo, NY 14214, United States
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14
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Krauss P, Tziridis K, Buerbank S, Schilling A, Schulze H. Therapeutic Value of Ginkgo biloba Extract EGb 761® in an Animal Model (Meriones unguiculatus) for Noise Trauma Induced Hearing Loss and Tinnitus. PLoS One 2016; 11:e0157574. [PMID: 27315063 PMCID: PMC4912078 DOI: 10.1371/journal.pone.0157574] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Accepted: 06/01/2016] [Indexed: 01/15/2023] Open
Abstract
Noise induced hearing loss (NIHL) is a common disease in modern societies and may lead to maladaptations within the auditory system that finally result in subjective tinnitus. Available therapies may only alleviate the symptoms rather than restore normal hearing. In a previous study we demonstrated that the prophylactic application of Ginkgo biloba extract EGb 761® significantly reduces NIHL and tinnitus development in our Mongolian gerbil (Meriones unguiculatus) animal model. Here, we tested whether the application of EGb 761® has beneficial effects after the formation of permanent NIHL and tinnitus. To this end we monitored the therapeutic effects of EGb 761® on noise trauma-induced changes in signal processing within the auditory system of our animal model by behavioral (acoustic startle response, ASR) and electrophysiological approaches (auditory brainstem responses, ABR). We found that–in contrast to vehicle–three weeks of daily oral EGb 761® treatment (100 mg/kg body weight) led to a restoration of hearing thresholds back to pre-trauma conditions. In addition, all 9 animals that displayed behavioral signs of subjective tinnitus showed improvement, with 7 of them showing complete relief of tinnitus symptoms during the time of EGb 761® treatment. After discontinuation of EGb 761® treatment, tinnitus related behavior reappeared in all but one of these animals while auditory thresholds remained restored. A detailed analysis of ABR waves revealed that EGb 761® treatment did not simply change auditory processing back to pre-trauma conditions, but led to subtle changes of ABR wave amplitude and latency at different levels of the auditory pathway, with an overall increase of response to low stimulus intensities and a decrease at high intensities. The functional relevance of these changes may be the observed improvement of hearing thresholds while at the same time suppression of responses to high stimulus intensities may point to a global inhibitory mechanism that counteracts tinnitus.
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Affiliation(s)
- Patrick Krauss
- Experimental Otolaryngology, Friedrich-Alexander Universität Erlangen-Nürnberg, Waldstrasse 1, 91054, Erlangen, Germany
| | - Konstantin Tziridis
- Experimental Otolaryngology, Friedrich-Alexander Universität Erlangen-Nürnberg, Waldstrasse 1, 91054, Erlangen, Germany
| | - Stefanie Buerbank
- Experimental Otolaryngology, Friedrich-Alexander Universität Erlangen-Nürnberg, Waldstrasse 1, 91054, Erlangen, Germany
| | - Achim Schilling
- Experimental Otolaryngology, Friedrich-Alexander Universität Erlangen-Nürnberg, Waldstrasse 1, 91054, Erlangen, Germany
| | - Holger Schulze
- Experimental Otolaryngology, Friedrich-Alexander Universität Erlangen-Nürnberg, Waldstrasse 1, 91054, Erlangen, Germany
- * E-mail:
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15
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Neural Hyperactivity of the Central Auditory System in Response to Peripheral Damage. Neural Plast 2016; 2016:2162105. [PMID: 26881094 PMCID: PMC4736999 DOI: 10.1155/2016/2162105] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 11/12/2015] [Accepted: 11/15/2015] [Indexed: 11/19/2022] Open
Abstract
It is increasingly appreciated that cochlear pathology is accompanied by adaptive responses in the central auditory system. The cause of cochlear pathology varies widely, and it seems that few commonalities can be drawn. In fact, despite intricate internal neuroplasticity and diverse external symptoms, several classical injury models provide a feasible path to locate responses to different peripheral cochlear lesions. In these cases, hair cell damage may lead to considerable hyperactivity in the central auditory pathways, mediated by a reduction in inhibition, which may underlie some clinical symptoms associated with hearing loss, such as tinnitus. Homeostatic plasticity, the most discussed and acknowledged mechanism in recent years, is most likely responsible for excited central activity following cochlear damage.
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16
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Carney LH, Kim DO, Kuwada S. Speech Coding in the Midbrain: Effects of Sensorineural Hearing Loss. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 894:427-435. [PMID: 27080684 DOI: 10.1007/978-3-319-25474-6_45] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
In response to voiced speech sounds, auditory-nerve (AN) fibres phase-lock to harmonics near best frequency (BF) and to the fundamental frequency (F0) of voiced sounds. Due to nonlinearities in the healthy ear, phase-locking in each frequency channel is dominated either by a single harmonic, for channels tuned near formants, or by F0, for channels between formants. The alternating dominance of these factors sets up a robust pattern of F0-synchronized rate across best frequency (BF). This profile of a temporally coded measure is transformed into a mean rate profile in the midbrain (inferior colliculus, IC), where neurons are sensitive to low-frequency fluctuations. In the impaired ear, the F0-synchronized rate profile is affected by several factors: Reduced synchrony capture decreases the dominance of a single harmonic near BF on the response. Elevated thresholds also reduce the effect of rate saturation, resulting in increased F0-synchrony. Wider peripheral tuning results in a wider-band envelope with reduced F0 amplitude. In general, sensorineural hearing loss reduces the contrast in AN F0-synchronized rates across BF. Computational models for AN and IC neurons illustrate how hearing loss would affect the F0-synchronized rate profiles set up in response to voiced speech sounds.
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Affiliation(s)
- Laurel H Carney
- Departments of Biomedical Engineering, Neurobiology & Anatomy, Electrical & Computer Engineering, University of Rochester, Rochester, NY, USA.
| | - Duck O Kim
- Department f Neuroscience, University of Connecticut Health Center, Farmington, CT, USA
| | - Shigeyuki Kuwada
- Department f Neuroscience, University of Connecticut Health Center, Farmington, CT, USA
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17
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Yoo YB, Maskey D, Kim MJ. Changes in the immunohistochemical localization of the glycine receptor in the superior olivary complex of adult circling mice. Mol Med Rep 2015; 12:7927-32. [PMID: 26498980 PMCID: PMC4758291 DOI: 10.3892/mmr.2015.4431] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Accepted: 09/09/2015] [Indexed: 11/06/2022] Open
Abstract
Circling mice is a mutant model of spontaneous deafness exhibiting degenerated spiral ganglion cells in the cochlea and loss of organ of Corti. The balance between glycinergic inhibition and glutamatergic excitation in the lateral superior olive (LSO) is essential for the detection of interaural level differences. Long term weakening of glycinergic synaptic inhibition in the LSO may lead to the downregulation of synaptic release of glycine in dorsal cochlear nucleus and downregulation of postsynaptic glycine receptor (GlyR) activity in the LSO, which may contribute to hearing loss. The present study utilized an immunohistochemical method to assess changes in GlyR immunoreactivity (IR) and the cell number in the superior olivary complex (SOC) of heterozygote (+/cir) and homozygote (cir/cir) circling mice. A significant decrease in the IR was observed in all nuclei of the SOC of homozygous mice. Loss of GlyR immunoreactive cells and a decrement in cell size was also observed in the homozygotes. A decrease in the GlyR IR in the neurons and neuropils, cell number and size of the cir/cir, may lead to profound changes in inhibitory transmission and the functional properties in the SOC nuclei. Therefore, the functional loss of inhibitory neurotransmitters in the brainstem may result in deafness of adult cir/cir mice.
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Affiliation(s)
- Young-Bok Yoo
- Department of Anatomy, Dankook University, College of Medicine, Cheonan‑si, South Chungcheong 330‑714, Republic of Korea
| | - Dhiraj Maskey
- Department of Anatomy, Nepalese Army Institute of Health Sciences‑College of Medicine, Sanobharyang, Kathmandu 10160, Nepal
| | - Myeung Ju Kim
- Department of Anatomy, Dankook University, College of Medicine, Cheonan‑si, South Chungcheong 330‑714, Republic of Korea
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18
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Eggermont JJ, Roberts LE. Tinnitus: animal models and findings in humans. Cell Tissue Res 2015; 361:311-36. [PMID: 25266340 PMCID: PMC4487353 DOI: 10.1007/s00441-014-1992-8] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Accepted: 08/14/2014] [Indexed: 12/19/2022]
Abstract
Chronic tinnitus (ringing of the ears) is a medically untreatable condition that reduces quality of life for millions of individuals worldwide. Most cases are associated with hearing loss that may be detected by the audiogram or by more sensitive measures. Converging evidence from animal models and studies of human tinnitus sufferers indicates that, while cochlear damage is a trigger, most cases of tinnitus are not generated by irritative processes persisting in the cochlea but by changes that take place in central auditory pathways when auditory neurons lose their input from the ear. Forms of neural plasticity underlie these neural changes, which include increased spontaneous activity and neural gain in deafferented central auditory structures, increased synchronous activity in these structures, alterations in the tonotopic organization of auditory cortex, and changes in network behavior in nonauditory brain regions detected by functional imaging of individuals with tinnitus and corroborated by animal investigations. Research on the molecular mechanisms that underlie neural changes in tinnitus is in its infancy and represents a frontier for investigation.
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Affiliation(s)
- Jos J Eggermont
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, and Department of Psychology, University of Calgary, 2500 University Drive N.W, Calgary, AB, Canada,
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19
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Chen Z, Yuan W. Central plasticity and dysfunction elicited by aural deprivation in the critical period. Front Neural Circuits 2015; 9:26. [PMID: 26082685 PMCID: PMC4451366 DOI: 10.3389/fncir.2015.00026] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Accepted: 05/13/2015] [Indexed: 12/31/2022] Open
Abstract
The acoustic signal is crucial for animals to obtain information from the surrounding environment. Like other sensory modalities, the central auditory system undergoes adaptive changes (i.e., plasticity) during the developmental stage as well as other stages of life. Owing to its plasticity, auditory centers may be susceptible to various factors, such as medical intervention, variation in ambient acoustic signals and lesion of the peripheral hearing organ. There are critical periods during which auditory centers are vulnerable to abnormal experiences. Particularly in the early postnatal development period, aural inputs are essential for functional maturity of auditory centers. An aural deprivation model, which can be achieved by attenuating or blocking the peripheral acoustic afferent input to the auditory center, is ideal for investigating plastic changes of auditory centers. Generally, auditory plasticity includes structural and functional changes, some of which can be irreversible. Aural deprivation can distort tonotopic maps, disrupt the binaural integration, reorganize the neural network and change the synaptic transmission in the primary auditory cortex or at lower levels of the auditory system. The regulation of specific gene expression and the modified signal pathway may be the deep molecular mechanism of these plastic changes. By studying this model, researchers may explore the pathogenesis of hearing loss and reveal plastic changes of the auditory cortex, facilitating the therapeutic advancement in patients with severe hearing loss. After summarizing developmental features of auditory centers in auditory deprived animals and discussing changes of central auditory remodeling in hearing loss patients, we aim at stressing the significant of an early and well-designed auditory training program for the hearing rehabilitation.
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Affiliation(s)
- Zhiji Chen
- Department of Otorhinolaryngology Head and Neck Surgery, Southwest Hospital, Third Military Medical University Chongqing, China
| | - Wei Yuan
- Department of Otorhinolaryngology Head and Neck Surgery, Southwest Hospital, Third Military Medical University Chongqing, China
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20
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Godfrey DA, Chen K, Godfrey MA, Lee AC, Crass SP, Shipp D, Simo H, Robinson KT. Cochlear ablation effects on amino acid levels in the chinchilla cochlear nucleus. Neuroscience 2015; 297:137-59. [PMID: 25839146 DOI: 10.1016/j.neuroscience.2015.03.055] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Revised: 03/06/2015] [Accepted: 03/24/2015] [Indexed: 10/23/2022]
Abstract
Inner ear damage can lead to hearing disorders, including tinnitus, hyperacusis, and hearing loss. We measured the effects of severe inner ear damage, produced by cochlear ablation, on the levels and distributions of amino acids in the first brain center of the auditory system, the cochlear nucleus. Measurements were also made for its projection pathways and the superior olivary nuclei. Cochlear ablation produces complete degeneration of the auditory nerve, which provides a baseline for interpreting the effects of partial damage to the inner ear, such as that from ototoxic drugs or intense sound. Amino acids play a critical role in neural function, including neurotransmission, neuromodulation, cellular metabolism, and protein construction. They include major neurotransmitters of the brain - glutamate, glycine, and γ-aminobutyrate (GABA) - as well as others closely related to their metabolism and/or functions - aspartate, glutamine, and taurine. Since the effects of inner ear damage develop over time, we measured the changes in amino acid levels at various survival times after cochlear ablation. Glutamate and aspartate levels decreased by 2weeks in the ipsilateral ventral cochlear nucleus and deep layer of the dorsal cochlear nucleus, with the largest decreases in the posteroventral cochlear nucleus (PVCN): 66% for glutamate and 63% for aspartate. Aspartate levels also decreased in the lateral part of the ipsilateral trapezoid body, by as much as 50%, suggesting a transneuronal effect. GABA and glycine levels showed some bilateral decreases, especially in the PVCN. These results may represent the state of amino acid metabolism in the cochlear nucleus of humans after removal of eighth nerve tumors, which may adversely result in destruction of the auditory nerve. Measurement of chemical changes following inner ear damage may increase understanding of the pathogenesis of hearing impairments and enable improvements in their diagnosis and treatment.
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Affiliation(s)
- D A Godfrey
- Department of Neurology, University of Toledo College of Medicine, Mail Stop 1195, 3000 Arlington Avenue, Toledo, OH 43614, USA; Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, 3000 Arlington Avenue, Toledo, OH 43614, USA.
| | - K Chen
- Department of Neurology, University of Toledo College of Medicine, Mail Stop 1195, 3000 Arlington Avenue, Toledo, OH 43614, USA; Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, 3000 Arlington Avenue, Toledo, OH 43614, USA
| | - M A Godfrey
- Department of Neurology, University of Toledo College of Medicine, Mail Stop 1195, 3000 Arlington Avenue, Toledo, OH 43614, USA; Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, 3000 Arlington Avenue, Toledo, OH 43614, USA
| | - A C Lee
- Department of Neurology, University of Toledo College of Medicine, Mail Stop 1195, 3000 Arlington Avenue, Toledo, OH 43614, USA; Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, 3000 Arlington Avenue, Toledo, OH 43614, USA
| | - S P Crass
- Department of Neurology, University of Toledo College of Medicine, Mail Stop 1195, 3000 Arlington Avenue, Toledo, OH 43614, USA; Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, 3000 Arlington Avenue, Toledo, OH 43614, USA
| | - D Shipp
- Department of Neurology, University of Toledo College of Medicine, Mail Stop 1195, 3000 Arlington Avenue, Toledo, OH 43614, USA; Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, 3000 Arlington Avenue, Toledo, OH 43614, USA
| | - H Simo
- Department of Neurology, University of Toledo College of Medicine, Mail Stop 1195, 3000 Arlington Avenue, Toledo, OH 43614, USA; Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, 3000 Arlington Avenue, Toledo, OH 43614, USA
| | - K T Robinson
- Department of Neurology, University of Toledo College of Medicine, Mail Stop 1195, 3000 Arlington Avenue, Toledo, OH 43614, USA; Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, 3000 Arlington Avenue, Toledo, OH 43614, USA
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21
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Berger JI, Coomber B. Tinnitus-related changes in the inferior colliculus. Front Neurol 2015; 6:61. [PMID: 25870582 PMCID: PMC4378364 DOI: 10.3389/fneur.2015.00061] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Accepted: 03/09/2015] [Indexed: 12/21/2022] Open
Abstract
Tinnitus is highly complex, diverse, and difficult to treat, in part due to the fact that the underlying causes and mechanisms remain elusive. Tinnitus is generated within the auditory brain; however, consolidating our understanding of tinnitus pathophysiology is difficult due to the diversity of reported effects and the variety of implicated brain nuclei. Here, we focus on the inferior colliculus (IC), a midbrain structure that integrates the vast majority of ascending auditory information and projects via the thalamus to the auditory cortex. The IC is also a point of convergence for corticofugal input and input originating outside the auditory pathway. We review the evidence, from both studies with human subjects and from animal models, for the contribution the IC makes to tinnitus. Changes in the IC, caused by either noise exposure or drug administration, involve fundamental, heterogeneous alterations in the balance of excitation and inhibition. However, differences between hearing loss-induced pathology and tinnitus-related pathology are not well understood. Moreover, variability in tinnitus induction methodology has a significant impact on subsequent neural and behavioral changes, which could explain some of the seemingly contradictory data. Nonetheless, the IC is likely involved in the generation and persistence of tinnitus perception.
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Affiliation(s)
- Joel I Berger
- Medical Research Council Institute of Hearing Research, University of Nottingham , Nottingham , UK
| | - Ben Coomber
- Medical Research Council Institute of Hearing Research, University of Nottingham , Nottingham , UK
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22
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Coomber B, Kowalkowski VL, Berger JI, Palmer AR, Wallace MN. Modulating central gain in tinnitus: changes in nitric oxide synthase in the ventral cochlear nucleus. Front Neurol 2015; 6:53. [PMID: 25806021 PMCID: PMC4354362 DOI: 10.3389/fneur.2015.00053] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 02/25/2015] [Indexed: 01/30/2023] Open
Abstract
A significant challenge in tinnitus research lies in explaining how acoustic insult leads to tinnitus in some individuals, but not others. One possibility is genetic variability in the expression and function of neuromodulators – components of neural signaling that alter the balance of excitation and inhibition in neural circuits. An example is nitric oxide (NO) – a free radical and potent neuromodulator in the mammalian brain – that regulates plasticity via both pre-synaptic and postsynaptic mechanisms. Changes in NO have previously been implicated in tinnitus generation, specifically in the ventral cochlear nucleus (VCN). Here, we examined nitric oxide synthase (NOS) – the enzyme responsible for NO production – in the guinea pig VCN following acoustic trauma. NOS was present in most cell types – including spherical and globular bushy cells, small, medium, and large multipolar cells, and octopus cells – spanning the entire extent of the VCN. The staining pattern was symmetrical in control animals. Unilateral acoustic over-exposure (AOE) resulted in marked asymmetries between ipsilateral and contralateral sides of the VCN in terms of the distribution of NOS across the cochlear nuclei in animals with behavioral evidence of tinnitus: fewer NOS-positive cells and a reduced level of NOS staining was present across the whole extent of the contralateral VCN, relative to the ipsilateral VCN. The asymmetric pattern of NOS-containing cells was observed as early as 1 day after AOE and was also present in some animals at 3, 7, and 21 days after AOE. However, it was not until 8 weeks after AOE, when tinnitus had developed, that asymmetries were significant overall, compared with control animals. Asymmetrical NOS expression was not correlated with shifts in the threshold hearing levels. Variability in NOS expression between animals may represent one underlying difference that can be linked to whether or not tinnitus develops after noise exposure.
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Affiliation(s)
- Ben Coomber
- MRC Institute of Hearing Research , Nottingham , UK
| | - Victoria L Kowalkowski
- MRC Institute of Hearing Research , Nottingham , UK ; Otology and Hearing, Division of Clinical Neuroscience, University of Nottingham , Nottingham , UK
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23
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Deep brain stimulation in tinnitus: current and future perspectives. Brain Res 2015; 1608:51-65. [PMID: 25758066 DOI: 10.1016/j.brainres.2015.02.050] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Revised: 02/25/2015] [Accepted: 02/26/2015] [Indexed: 11/22/2022]
Abstract
Chronic tinnitus, also known as ringing in the ears, affects up to 15% of the adults and causes a serious socio-economic burden. At present, there is no treatment available which substantially reduces the perception of this phantom sound. In the past few years, preclinical and clinical studies have unraveled central mechanisms involved in the pathophysiology of tinnitus, replacing the classical periphery-based hypothesis. In subcortical auditory and non-auditory regions, increased spontaneous activity, neuronal bursting and synchrony were found. When reaching the auditory cortex, these neuronal alterations become perceptually relevant and consequently are perceived as phantom sound. A therapy with a potential to counteract deeply located pathological activity is deep brain stimulation, which has already been demonstrated to be effective in neurological diseases such as Parkinson's disease. In this review, several brain targets are discussed as possible targets for deep brain stimulation in tinnitus. The potential applicability of this treatment in tinnitus is discussed with examples from the preclinical field and clinical case studies.
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24
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Ropp TJF, Tiedemann KL, Young ED, May BJ. Effects of unilateral acoustic trauma on tinnitus-related spontaneous activity in the inferior colliculus. J Assoc Res Otolaryngol 2014; 15:1007-22. [PMID: 25255865 PMCID: PMC4389963 DOI: 10.1007/s10162-014-0488-2] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Accepted: 09/08/2014] [Indexed: 12/13/2022] Open
Abstract
This study describes the long-term effects of sound-induced cochlear trauma on spontaneous discharge rates in the central nucleus of the inferior colliculus (ICC). As in previous studies, single-unit recordings in Sprague-Dawley rats revealed pervasive increases in spontaneous discharge rates. Based on differences in their sources of input, it was hypothesized that physiologically defined neural populations of the auditory midbrain would reveal the brainstem sources that dictate ICC hyperactivity. Abnormal spontaneous activity was restricted to target neurons of the ventral cochlear nucleus. Nearly identical patterns of hyperactivity were observed in the contralateral and ipsilateral ICC. The elevation in spontaneous activity extended to frequencies well below and above the region of maximum threshold shift. This lack of frequency organization suggests that ICC hyperactivity may be influenced by regions of the brainstem that are not tonotopically organized. Sound-induced hyperactivity is often observed in animals with behavioral signs of tinnitus. Prior to electrophysiological recording, rats were screened for tinnitus by measuring gap pre-pulse inhibition of the acoustic startle reflex (GPIASR). Rats with positive phenotypes did not exhibit unique patterns of ICC hyperactivity. This ambiguity raises concerns regarding animal behavioral models of tinnitus. If our screening procedures were valid, ICC hyperactivity is observed in animals without behavioral indications of the disorder. Alternatively, if the perception of tinnitus is strictly linked to ongoing ICC hyperactivity, our current behavioral approach failed to provide a reliable assessment of tinnitus state.
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Affiliation(s)
- Tessa-Jonne F. Ropp
- />Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205 USA
| | - Kerrie L. Tiedemann
- />Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205 USA
| | - Eric D. Young
- />Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205 USA
| | - Bradford J. May
- />Department of Otolaryngology, Head and Neck Surgery, Johns Hopkins University School of Medicine, Traylor Research Building, Room 521 720 Rutland Avenue, Baltimore, MD 21205 USA
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25
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Lee AC, Godfrey DA. Cochlear damage affects neurotransmitter chemistry in the central auditory system. Front Neurol 2014; 5:227. [PMID: 25477858 PMCID: PMC4237057 DOI: 10.3389/fneur.2014.00227] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Accepted: 10/20/2014] [Indexed: 02/04/2023] Open
Abstract
Tinnitus, the perception of a monotonous sound not actually present in the environment, affects nearly 20% of the population of the United States. Although there has been great progress in tinnitus research over the past 25 years, the neurochemical basis of tinnitus is still poorly understood. We review current research about the effects of various types of cochlear damage on the neurotransmitter chemistry in the central auditory system and document evidence that different changes in this chemistry can underlie similar behaviorally measured tinnitus symptoms. Most available data have been obtained from rodents following cochlear damage produced by cochlear ablation, intense sound, or ototoxic drugs. Effects on neurotransmitter systems have been measured as changes in neurotransmitter level, synthesis, release, uptake, and receptors. In this review, magnitudes of changes are presented for neurotransmitter-related amino acids, acetylcholine, and serotonin. A variety of effects have been found in these studies that may be related to animal model, survival time, type and/or magnitude of cochlear damage, or methodology. The overall impression from the evidence presented is that any imbalance of neurotransmitter-related chemistry could disrupt auditory processing in such a way as to produce tinnitus.
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Affiliation(s)
- Augustine C Lee
- Department of Neurology, University of Toledo College of Medicine , Toledo, OH , USA ; Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine , Toledo, OH , USA
| | - Donald A Godfrey
- Department of Neurology, University of Toledo College of Medicine , Toledo, OH , USA ; Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine , Toledo, OH , USA
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26
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Auerbach BD, Rodrigues PV, Salvi RJ. Central gain control in tinnitus and hyperacusis. Front Neurol 2014; 5:206. [PMID: 25386157 PMCID: PMC4208401 DOI: 10.3389/fneur.2014.00206] [Citation(s) in RCA: 259] [Impact Index Per Article: 25.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Accepted: 09/30/2014] [Indexed: 12/02/2022] Open
Abstract
Sensorineural hearing loss induced by noise or ototoxic drug exposure reduces the neural activity transmitted from the cochlea to the central auditory system. Despite a reduced cochlear output, neural activity from more central auditory structures is paradoxically enhanced at suprathreshold intensities. This compensatory increase in the central auditory activity in response to the loss of sensory input is referred to as central gain enhancement. Enhanced central gain is hypothesized to be a potential mechanism that gives rise to hyperacusis and tinnitus, two debilitating auditory perceptual disorders that afflict millions of individuals. This review will examine the evidence for gain enhancement in the central auditory system in response to cochlear damage. Further, it will address the potential cellular and molecular mechanisms underlying this enhancement and discuss the contribution of central gain enhancement to tinnitus and hyperacusis. Current evidence suggests that multiple mechanisms with distinct temporal and spectral profiles are likely to contribute to central gain enhancement. Dissecting the contributions of these different mechanisms at different levels of the central auditory system is essential for elucidating the role of central gain enhancement in tinnitus and hyperacusis and, most importantly, the development of novel treatments for these disorders.
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Affiliation(s)
- Benjamin D Auerbach
- Department of Communicative Disorders and Sciences, Center for Hearing and Deafness, University at Buffalo, The State University of New York , Buffalo, NY , USA
| | - Paulo V Rodrigues
- Department of Communicative Disorders and Sciences, Center for Hearing and Deafness, University at Buffalo, The State University of New York , Buffalo, NY , USA
| | - Richard J Salvi
- Department of Communicative Disorders and Sciences, Center for Hearing and Deafness, University at Buffalo, The State University of New York , Buffalo, NY , USA
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27
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Fuentes-Santamaría V, Alvarado JC, López-Muñoz DF, Melgar-Rojas P, Gabaldón-Ull MC, Juiz JM. Glia-related mechanisms in the anteroventral cochlear nucleus of the adult rat in response to unilateral conductive hearing loss. Front Neurosci 2014; 8:319. [PMID: 25352772 PMCID: PMC4195288 DOI: 10.3389/fnins.2014.00319] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Accepted: 09/19/2014] [Indexed: 11/13/2022] Open
Abstract
Conductive hearing loss causes a progressive decline in cochlear activity that may result in functional and structural modifications in auditory neurons. However, whether these activity-dependent changes are accompanied by a glial response involving microglia, astrocytes, or both has not yet been fully elucidated. Accordingly, the present study was designed to determine the involvement of glial related mechanisms in the anteroventral cochlear nucleus (AVCN) of adult rats at 1, 4, 7, and 15 d after removing middle ear ossicles. Quantitative immunohistochemistry analyses at light microscopy with specific markers of microglia or astroglia along with immunocytochemistry at the electron microscopy level were used. Also, in order to test whether trophic support by neurotrophins is modulated in glial cells by auditory activity, the expression and distribution of neurotrophin-3 (NT-3) and its colocalization with microglial or astroglial markers was investigated. Diminished cochlear activity after middle ear ossicle removal leads to a significant ipsilateral increase in the mean gray levels and stained area of microglial cells but not astrocytes in the AVCN at 1 and 4 d post-lesion as compared to the contralateral side and control animals. These results suggest that microglial cells but not astrocytes may act as dynamic modulators of synaptic transmission in the cochlear nucleus immediately following unilateral hearing loss. On the other hand, NT-3 immunostaining was localized mainly in neuronal cell bodies and axons and was upregulated at 1, 4 and 7 d post-lesion. Very few glial cells expressed this neurotrophin in both control and experimental rats, suggesting that NT-3 is primarily activated in neurons and not as much in glia after limiting auditory activity in the AVCN by conductive hearing loss.
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Affiliation(s)
- Verónica Fuentes-Santamaría
- Facultad de Medicina, Instituto de Investigación en Discapacidades, Neurológicas (IDINE), Universidad de Castilla-La Mancha Albacete, Spain
| | - Juan C Alvarado
- Facultad de Medicina, Instituto de Investigación en Discapacidades, Neurológicas (IDINE), Universidad de Castilla-La Mancha Albacete, Spain
| | - Diego F López-Muñoz
- Facultad de Medicina, Instituto de Investigación en Discapacidades, Neurológicas (IDINE), Universidad de Castilla-La Mancha Albacete, Spain
| | - Pedro Melgar-Rojas
- Facultad de Medicina, Instituto de Investigación en Discapacidades, Neurológicas (IDINE), Universidad de Castilla-La Mancha Albacete, Spain
| | - María C Gabaldón-Ull
- Facultad de Medicina, Instituto de Investigación en Discapacidades, Neurológicas (IDINE), Universidad de Castilla-La Mancha Albacete, Spain
| | - José M Juiz
- Facultad de Medicina, Instituto de Investigación en Discapacidades, Neurológicas (IDINE), Universidad de Castilla-La Mancha Albacete, Spain
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Gröschel M, Hubert N, Müller S, Ernst A, Basta D. Age-dependent changes of calcium related activity in the central auditory pathway. Exp Gerontol 2014; 58:235-43. [DOI: 10.1016/j.exger.2014.08.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Revised: 07/31/2014] [Accepted: 08/28/2014] [Indexed: 10/24/2022]
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Acute and long-term effects of noise exposure on the neuronal spontaneous activity in cochlear nucleus and inferior colliculus brain slices. BIOMED RESEARCH INTERNATIONAL 2014; 2014:909260. [PMID: 25110707 PMCID: PMC4119618 DOI: 10.1155/2014/909260] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Revised: 06/20/2014] [Accepted: 06/20/2014] [Indexed: 11/17/2022]
Abstract
Noise exposure leads to an immediate hearing loss and is followed by a long-lasting permanent threshold shift, accompanied by changes of cellular properties within the central auditory pathway. Electrophysiological recordings have demonstrated an upregulation of spontaneous neuronal activity. It is still discussed if the observed effects are related to changes of peripheral input or evoked within the central auditory system. The present study should describe the intrinsic temporal patterns of single-unit activity upon noise-induced hearing loss of the dorsal and ventral cochlear nucleus (DCN and VCN) and the inferior colliculus (IC) in adult mouse brain slices. Recordings showed a slight, but significant, elevation in spontaneous firing rates in DCN and VCN immediately after noise trauma, whereas no differences were found in IC. One week postexposure, neuronal responses remained unchanged compared to controls. At 14 days after noise trauma, intrinsic long-term hyperactivity in brain slices of the DCN and the IC was detected for the first time. Therefore, increase in spontaneous activity seems to develop within the period of two weeks, but not before day 7. The results give insight into the complex temporal neurophysiological alterations after noise trauma, leading to a better understanding of central mechanisms in noise-induced hearing loss.
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Protective effects of Ginkgo biloba extract EGb 761 against noise trauma-induced hearing loss and tinnitus development. Neural Plast 2014; 2014:427298. [PMID: 25028612 PMCID: PMC4083883 DOI: 10.1155/2014/427298] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Revised: 04/25/2014] [Accepted: 04/29/2014] [Indexed: 01/16/2023] Open
Abstract
Noise-induced hearing loss (NIHL) and resulting comorbidities like subjective tinnitus are common diseases in modern societies. A substance shown to be effective against NIHL in an animal model is the Ginkgo biloba extract EGb 761. Further effects of the extract on the cellular and systemic levels of the nervous system make it a promising candidate not only for protection against NIHL but also for its secondary comorbidities like tinnitus. Following an earlier study we here tested the potential effectiveness of prophylactic EGb 761 treatment against NIHL and tinnitus development in the Mongolian gerbil. We monitored the effects of EGb 761 and noise trauma-induced changes on signal processing within the auditory system by means of behavioral and electrophysiological approaches. We found significantly reduced NIHL and tinnitus development upon EGb 761 application, compared to vehicle treated animals. These protective effects of EGb 761 were correlated with changes in auditory processing, both at peripheral and central levels. We propose a model with two main effects of EGb 761 on auditory processing, first, an increase of auditory brainstem activity leading to an increased thalamic input to the primary auditory cortex (AI) and second, an asymmetric effect on lateral inhibition in AI.
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31
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Gold JR, Bajo VM. Insult-induced adaptive plasticity of the auditory system. Front Neurosci 2014; 8:110. [PMID: 24904256 PMCID: PMC4033160 DOI: 10.3389/fnins.2014.00110] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Accepted: 04/28/2014] [Indexed: 01/10/2023] Open
Abstract
The brain displays a remarkable capacity for both widespread and region-specific modifications in response to environmental challenges, with adaptive processes bringing about the reweighing of connections in neural networks putatively required for optimizing performance and behavior. As an avenue for investigation, studies centered around changes in the mammalian auditory system, extending from the brainstem to the cortex, have revealed a plethora of mechanisms that operate in the context of sensory disruption after insult, be it lesion-, noise trauma, drug-, or age-related. Of particular interest in recent work are those aspects of auditory processing which, after sensory disruption, change at multiple—if not all—levels of the auditory hierarchy. These include changes in excitatory, inhibitory and neuromodulatory networks, consistent with theories of homeostatic plasticity; functional alterations in gene expression and in protein levels; as well as broader network processing effects with cognitive and behavioral implications. Nevertheless, there abounds substantial debate regarding which of these processes may only be sequelae of the original insult, and which may, in fact, be maladaptively compelling further degradation of the organism's competence to cope with its disrupted sensory context. In this review, we aim to examine how the mammalian auditory system responds in the wake of particular insults, and to disambiguate how the changes that develop might underlie a correlated class of phantom disorders, including tinnitus and hyperacusis, which putatively are brought about through maladaptive neuroplastic disruptions to auditory networks governing the spatial and temporal processing of acoustic sensory information.
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Affiliation(s)
- Joshua R Gold
- Department of Physiology, Anatomy and Genetics, University of Oxford Oxford, UK
| | - Victoria M Bajo
- Department of Physiology, Anatomy and Genetics, University of Oxford Oxford, UK
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Coomber B, Berger JI, Kowalkowski VL, Shackleton TM, Palmer AR, Wallace MN. Neural changes accompanying tinnitus following unilateral acoustic trauma in the guinea pig. Eur J Neurosci 2014; 40:2427-41. [PMID: 24702651 PMCID: PMC4215599 DOI: 10.1111/ejn.12580] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 03/03/2014] [Indexed: 12/31/2022]
Abstract
Animal models of tinnitus allow us to study the relationship between changes in neural activity and the tinnitus percept. Here, guinea pigs were subjected to unilateral noise trauma and tested behaviourally for tinnitus 8 weeks later. By comparing animals with tinnitus with those without, all of which were noise-exposed, we were able to identify changes unique to the tinnitus group. Three physiological markers known to change following noise exposure were examined: spontaneous firing rates (SFRs) and burst firing in the inferior colliculus (IC), evoked auditory brainstem responses (ABRs), and the number of neurons in the cochlear nucleus containing nitric oxide synthase (NOS). We obtained behavioural evidence of tinnitus in 12 of 16 (75%) animals. Both SFRs and incidences of burst firing were elevated in the IC of all noise-exposed animals, but there were no differences between tinnitus and no-tinnitus animals. There were significant decreases in ipsilateral ABR latencies in tinnitus animals, contrary to what might be expected with a small hearing loss. Furthermore, there was an ipsilateral-contralateral asymmetry in NOS staining in the ventral cochlear nucleus (VCN) that was only apparent in tinnitus animals. Tinnitus animals had a significantly greater number of NOS-containing neurons on the noise-exposed side, whereas no-tinnitus animals did not. These data suggest that measuring NOS in the VCN and recording ABRs supplement behavioural methods for confirming tinnitus in animals, and that nitric oxide is involved in plastic neural changes associated with tinnitus.
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Affiliation(s)
- Ben Coomber
- MRC Institute of Hearing Research, University Park, Nottingham, NG7 2RD, UK
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Abstract
Tinnitus and cochlear damage have been associated with changes in somatosensory-auditory integration and plasticity in the dorsal cochlear nucleus (DCN). Recently, we demonstrated in vivo that DCN bimodal plasticity is stimulus timing-dependent, with Hebbian and anti-Hebbian timing rules that reflect in vitro spike timing-dependent plasticity. In this in vivo study, we assessed the stimulus timing dependence of bimodal plasticity in a tinnitus model. Guinea pigs were exposed to a narrowband noise that produced a temporary elevation of auditory brainstem response thresholds. A total of 60% of the guinea pigs developed tinnitus as indicated by gap-induced prepulse inhibition of the acoustic startle. After noise exposure and tinnitus induction, stimulus timing-dependent plasticity was measured by comparing responses to sound before and after paired somatosensory and auditory stimulation presented with varying intervals and orders. In comparison with Sham and noise-exposed animals that did not develop tinnitus, timing rules in verified tinnitus animals were more likely to be anti-Hebbian and broader for those bimodal intervals in which the neural activity showed enhancement. Furthermore, units from exposed animals with tinnitus were more weakly suppressed than either Sham animals or exposed animals without tinnitus. The broadened timing rules in the enhancement phase in animals with tinnitus, and in the suppressive phase in exposed animals without tinnitus was in contrast to narrow, Hebbian-like timing rules in Sham animals. These findings implicate alterations in DCN bimodal spike timing-dependent plasticity as underlying mechanisms in tinnitus, opening the way for a therapeutic target.
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Godfrey DA, Jin YM, Liu X, Godfrey MA. Effects of cochlear ablation on amino acid levels in the rat cochlear nucleus and superior olive. Hear Res 2014; 309:44-54. [PMID: 24291808 PMCID: PMC5819880 DOI: 10.1016/j.heares.2013.11.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Revised: 11/05/2013] [Accepted: 11/19/2013] [Indexed: 11/21/2022]
Abstract
Amino acids have important roles in the chemistry of the auditory system, including communication among neurons. There is much evidence for glutamate as a neurotransmitter from auditory nerve fibers to cochlear nucleus neurons. Previous studies in rodents have examined effects of removal of auditory nerve input by cochlear ablation on levels, uptake and release of glutamate in cochlear nucleus subdivisions, as well as on glutamate receptors. Effects have also been reported on uptake and release of γ-aminobutyrate (GABA) and glycine, two other amino acids strongly implicated in cochlear nucleus synaptic transmission. We mapped the effects of cochlear ablation on the levels of amino acids, including glutamate, GABA, glycine, aspartate, glutamine, taurine, serine, threonine, and arginine, in microscopic subregions of the rat cochlear nucleus. Submicrogram-size samples microdissected from freeze-dried brainstem sections were assayed for amino acid levels by high performance liquid chromatography. After cochlear ablation, glutamate and aspartate levels decreased by 2 days in regions receiving relatively dense innervation from the auditory nerve, whereas the levels of most other amino acids increased. The results are consistent with a close association of glutamate and aspartate with auditory nerve fibers and of other amino acids with other neurons and glia in the cochlear nucleus. A consistent decrease of GABA level in the lateral superior olive could be consistent with a role in some lateral olivocochlear neurons. The results are compared with those obtained with the same methods for the rat vestibular nerve root and nuclei after vestibular ganglionectomy.
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Affiliation(s)
- Donald A Godfrey
- Department of Neurology and Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, Toledo, OH, USA.
| | - Yong-Ming Jin
- Department of Neurology and Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, Toledo, OH, USA
| | - Xiaochen Liu
- Department of Neurology and Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, Toledo, OH, USA
| | - Matthew A Godfrey
- Department of Neurology and Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, Toledo, OH, USA
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Grande G, Negandhi J, Harrison RV, Wang LY. Remodelling at the calyx of Held-MNTB synapse in mice developing with unilateral conductive hearing loss. J Physiol 2014; 592:1581-600. [PMID: 24469075 DOI: 10.1113/jphysiol.2013.268839] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Structure and function of central synapses are profoundly influenced by experience during developmental sensitive periods. Sensory synapses, which are the indispensable interface for the developing brain to interact with its environment, are particularly plastic. In the auditory system, moderate forms of unilateral hearing loss during development are prevalent but the pre- and postsynaptic modifications that occur when hearing symmetry is perturbed are not well understood. We investigated this issue by performing experiments at the large calyx of Held synapse. Principal neurons of the medial nucleus of the trapezoid body (MNTB) are innervated by calyx of Held terminals that originate from the axons of globular bushy cells located in the contralateral ventral cochlear nucleus. We compared populations of synapses in the same animal that were either sound deprived (SD) or sound experienced (SE) after unilateral conductive hearing loss (CHL). Middle ear ossicles were removed 1 week prior to hearing onset (approx. postnatal day (P) 12) and morphological and electrophysiological approaches were applied to auditory brainstem slices taken from these mice at P17-19. Calyces in the SD and SE MNTB acquired their mature digitated morphology but these were structurally more complex than those in normal hearing mice. This was accompanied by bilateral decreases in initial EPSC amplitude and synaptic conductance despite the CHL being unilateral. During high-frequency stimulation, some SD synapses displayed short-term depression whereas others displayed short-term facilitation followed by slow depression similar to the heterogeneities observed in normal hearing mice. However SE synapses predominantly displayed short-term facilitation followed by slow depression which could be explained in part by the decrease in release probability. Furthermore, the excitability of principal cells in the SD MNTB had increased significantly. Despite these unilateral changes in short-term plasticity and excitability, heterogeneities in the spiking fidelity among the population of both SD and SE synapses showed similar continuums to those in normal hearing mice. Our study suggests that preservations in the heterogeneity in spiking fidelity via synaptic remodelling ensures symmetric functional stability which is probably important for retaining the capability to maximally code sound localization cues despite moderate asymmetries in hearing experience.
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Affiliation(s)
- Giovanbattista Grande
- Corresponding Author L.-Y. Wang, The Hospital for Sick Children, 555 University Ave, Toronto, Ontario, Canada M5G 1X8.
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36
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Shaikh AG, Finlayson PG. Forskolin induced increase in spontaneous activity of auditory brainstem neurons is comparable to acoustic stimulus evoked responses. Neurosci Lett 2012; 531:69-73. [PMID: 23127850 DOI: 10.1016/j.neulet.2012.10.053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2012] [Revised: 10/05/2012] [Accepted: 10/26/2012] [Indexed: 10/27/2022]
Abstract
Contemporary proposals for the pathophysiology of tinnitus due to cochlear damage underscore increased spontaneous activity of auditory brainstem neurons. One of the several consequences of the cochlear injury is the activation of the ERK pathway, suppression of phosphodiestase E activity, and putatively setting a long-term increase in intracellular levels of cyclic AMP at central auditory neurons. Local application of forskolin also increases intracellular cyclic AMP and spontaneous neural activity. We measured the effects of locally applied forskolin on spontaneous firing rate of isolated neurons in the peri-olivary region of the superior olive complex in anesthetized adult Long Evan rats. Forskolin induced increase in spontaneous neural activity was comparable to supra-threshold tone evoke neural responses. These results are viewed in context of hyperexcitability as a correlate of tinnitus.
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Affiliation(s)
- Aasef G Shaikh
- Department of Neurology, Case Western Reserve University, Cleveland, OH, United States.
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37
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Kraus KS, Canlon B. Neuronal connectivity and interactions between the auditory and limbic systems. Effects of noise and tinnitus. Hear Res 2012; 288:34-46. [DOI: 10.1016/j.heares.2012.02.009] [Citation(s) in RCA: 162] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2011] [Revised: 12/09/2011] [Accepted: 02/22/2012] [Indexed: 01/01/2023]
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Schaette R, Kempter R. Computational models of neurophysiological correlates of tinnitus. Front Syst Neurosci 2012; 6:34. [PMID: 22586377 PMCID: PMC3347476 DOI: 10.3389/fnsys.2012.00034] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2012] [Accepted: 04/17/2012] [Indexed: 11/13/2022] Open
Abstract
The understanding of tinnitus has progressed considerably in the past decade, but the details of the mechanisms that give rise to this phantom perception of sound without a corresponding acoustic stimulus have not yet been pinpointed. It is now clear that tinnitus is generated in the brain, not in the ear, and that it is correlated with pathologically altered spontaneous activity of neurons in the central auditory system. Both increased spontaneous firing rates and increased neuronal synchrony have been identified as putative neuronal correlates of phantom sounds in animal models, and both phenomena can be triggered by damage to the cochlea. Various mechanisms could underlie the generation of such aberrant activity. At the cellular level, decreased synaptic inhibition and increased neuronal excitability, which may be related to homeostatic plasticity, could lead to an over-amplification of natural spontaneous activity. At the network level, lateral inhibition could amplify differences in spontaneous activity, and structural changes such as reorganization of tonotopic maps could lead to self-sustained activity in recurrently connected neurons. However, it is difficult to disentangle the contributions of different mechanisms in experiments, especially since not all changes observed in animal models of tinnitus are necessarily related to tinnitus. Computational modeling presents an opportunity of evaluating these mechanisms and their relation to tinnitus. Here we review the computational models for the generation of neurophysiological correlates of tinnitus that have been proposed so far, and evaluate predictions and compare them to available data. We also assess the limits of their explanatory power, thus demonstrating where an understanding is still lacking and where further research may be needed. Identifying appropriate models is important for finding therapies, and we therefore, also summarize the implications of the models for approaches to treat tinnitus.
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Mechanisms contributing to central excitability changes during hearing loss. Proc Natl Acad Sci U S A 2012; 109:8292-7. [PMID: 22566618 DOI: 10.1073/pnas.1116981109] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
Abstract
Exposure to loud sound causes cochlear damage resulting in hearing loss and tinnitus. Tinnitus has been related to hyperactivity in the central auditory pathway occurring weeks after loud sound exposure. However, central excitability changes concomitant to hearing loss and preceding those periods of hyperactivity, remain poorly explored. Here we investigate mechanisms contributing to excitability changes in the dorsal cochlear nucleus (DCN) shortly after exposure to loud sound that produces hearing loss. We show that acoustic overexposure alters synaptic transmission originating from the auditory and the multisensory pathway within the DCN in different ways. A reduction in the number of myelinated auditory nerve fibers leads to a reduced maximal firing rate of DCN principal cells, which cannot be restored by increasing auditory nerve fiber recruitment. In contrast, a decreased membrane resistance of DCN granule cells (multisensory inputs) leads to a reduced maximal firing rate of DCN principal cells that is overcome when additional multisensory fibers are recruited. Furthermore, gain modulation by inhibitory synaptic transmission is disabled in both auditory and multisensory pathways. These cellular mechanisms that contribute to decreased cellular excitability in the central auditory pathway are likely to represent early neurobiological markers of hearing loss and may suggest interventions to delay or stop the development of hyperactivity that has been associated with tinnitus.
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40
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Middleton JW, Tzounopoulos T. Imaging the neural correlates of tinnitus: a comparison between animal models and human studies. Front Syst Neurosci 2012; 6:35. [PMID: 22586378 PMCID: PMC3343475 DOI: 10.3389/fnsys.2012.00035] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2012] [Accepted: 04/17/2012] [Indexed: 12/22/2022] Open
Abstract
Tinnitus is the perception of a sound, a so-called "phantom sound," in the absence of a physical sound. The phantom perception persists after transection of the auditory nerve, indicating that the site of tinnitus manifestation is in the central nervous system. Imaging studies in tinnitus sufferers have revealed increased neuronal activity-hyperactivity-in subcortical and cortical auditory centers. These studies have demonstrated that non-auditory brain areas, such as the limbic system, are involved in the neural basis of tinnitus, Finally human imaging studies have led to novel hypotheses for the generation of tinnitus, such as the thalamocortical dysrhythmia hypothesis. Imaging in animal models of tinnitus exhibit similarities to results from human studies and have revealed hyperexcitability of auditory brain centers as a neural correlate of tinnitus. We propose that the comparison between animal model and human studies will aid in the design of appropriate experimental paradigms aimed at elucidating the cellular and circuit mechanisms underlying tinnitus.
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Affiliation(s)
- Jason W Middleton
- Department of Otolaryngology, University of Pittsburgh, Pittsburgh PA, USA
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41
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Manzoor NF, Licari FG, Klapchar M, Elkin RL, Gao Y, Chen G, Kaltenbach JA. Noise-induced hyperactivity in the inferior colliculus: its relationship with hyperactivity in the dorsal cochlear nucleus. J Neurophysiol 2012; 108:976-88. [PMID: 22552192 DOI: 10.1152/jn.00833.2011] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Intense noise exposure causes hyperactivity to develop in the mammalian dorsal cochlear nucleus (DCN) and inferior colliculus (IC). It has not yet been established whether the IC hyperactivity is driven by hyperactivity from extrinsic sources that include the DCN or instead is maintained independently of this input. We have investigated the extent to which IC hyperactivity is dependent on input from the contralateral DCN by comparing recordings of spontaneous activity in the IC of noise-exposed and control hamsters before and after ablation of the contralateral DCN. One group of animals was binaurally exposed to intense sound (10 kHz, 115 dB SPL, 4 h), whereas the control group was not. Both groups were studied electrophysiologically 2-3 wk later by first mapping spontaneous activity along the tonotopic axis of the IC to confirm induction of hyperactivity. Spontaneous activity was then recorded at a hyperactive IC locus over two 30-min periods, one with DCNs intact and the other after ablation of the contralateral DCN. In a subset of animals, activity was again mapped along the tonotopic axis after the time course of the activity was recorded before and after DCN ablation. Following recordings, the brains were fixed, and histological evaluations were performed to assess the extent of DCN ablation. Ablation of the DCN resulted in major reductions of IC hyperactivity. Levels of postablation activity in exposed animals were similar to the levels of activity in the IC of control animals, indicating an almost complete loss of hyperactivity in exposed animals. The results suggest that hyperactivity in the IC is dependent on support from extrinsic sources that include and may even begin with the DCN. This finding does not rule out longer term compensatory or homeostatic adjustments that might restore hyperactivity in the IC over time.
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Affiliation(s)
- N F Manzoor
- Department of Neurosciences, Lerner Research Institute, Head and Neck Institute, The Cleveland Clinic, Cleveland, OH, USA
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Browne CJ, Morley JW, Parsons CH. Tracking the expression of excitatory and inhibitory neurotransmission-related proteins and neuroplasticity markers after noise induced hearing loss. PLoS One 2012; 7:e33272. [PMID: 22428005 PMCID: PMC3299769 DOI: 10.1371/journal.pone.0033272] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Accepted: 02/10/2012] [Indexed: 11/19/2022] Open
Abstract
Excessive exposure to loud noise can damage the cochlea and create a hearing loss. These pathologies coincide with a range of CNS changes including reorganisation of frequency representation, alterations in the pattern of spontaneous activity and changed expression of excitatory and inhibitory neurotransmitters. Moreover, damage to the cochlea is often accompanied by acoustic disorders such as hyperacusis and tinnitus, suggesting that one or more of these neuronal changes may be involved in these disorders, although the mechanisms remain unknown. We tested the hypothesis that excessive noise exposure increases expression of markers of excitation and plasticity, and decreases expression of inhibitory markers over a 32-day recovery period. Adult rats (n = 25) were monaurally exposed to a loud noise (16 kHz, 1/10(th) octave band pass (115 dB SPL)) for 1-hour, or left as non-exposed controls (n = 5). Animals were euthanased at either 0, 4, 8, 16 or 32 days following acoustic trauma. We used Western Blots to quantify protein levels of GABA(A) receptor subunit α1 (GABA(A)α1), Glutamic-Acid Decarboxylase-67 (GAD-67), N-Methyl-D-Aspartate receptor subunit 2A (NR2A), Calbindin (Calb1) and Growth Associated Protein 43 (GAP-43) in the Auditory Cortex (AC), Inferior Colliculus (IC) and Dorsal Cochlear Nucleus (DCN). Compared to sham-exposed controls, noise-exposed animals had significantly (p<0.05): lower levels of GABA(A)α1 in the contralateral AC at day-16 and day-32, lower levels of GAD-67 in the ipsilateral DCN at day-4, lower levels of Calb1 in the ipsilateral DCN at day-0, lower levels of GABA(A)α1 in the ipsilateral AC at day-4 and day-32. GAP-43 was reduced in the ipsilateral AC for the duration of the experiment. These complex fluctuations in protein expression suggests that for at least a month following acoustic trauma the auditory system is adapting to a new pattern of sensory input.
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Affiliation(s)
| | | | - Carl H. Parsons
- Department of Anatomy and Cell Biology, School of Medicine, The University of Western Sydney, Sydney, New South Wales, Australia
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Abstract
Interaural differences in stimulus intensity and timing are major cues for sound localization. In mammals, these cues are first processed in the lateral and medial superior olive by interaction of excitatory and inhibitory synaptic inputs from ipsi- and contralateral cochlear nucleus neurons. To preserve sound localization acuity following changes in the acoustic environment, the processing of these binaural cues needs neuronal adaptation. Recent studies have shown that binaural sensitivity adapts to stimulation history within milliseconds, but the actual extent of binaural adaptation is unknown. In the current study, we investigated long-term effects on binaural sensitivity using extracellular in vivo recordings from single neurons in the dorsal nucleus of the lateral lemniscus that inherit their binaural properties directly from the lateral and medial superior olives. In contrast to most previous studies, we used a noninvasive approach to influence this processing. Adult gerbils were exposed for 2 weeks to moderate noise with no stable binaural cue. We found monaural response properties to be unaffected by this measure. However, neuronal sensitivity to binaural cues was reversibly altered for a few days. Computational models of sensitivity to interaural time and level differences suggest that upregulation of inhibition in the superior olivary complex can explain the electrophysiological data.
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Plasticity of serotonergic innervation of the inferior colliculus in mice following acoustic trauma. Hear Res 2011; 283:89-97. [PMID: 22101024 DOI: 10.1016/j.heares.2011.11.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2011] [Revised: 10/11/2011] [Accepted: 11/03/2011] [Indexed: 01/30/2023]
Abstract
Acoustic trauma often results in permanent damage to the cochlea, triggering changes in processing within central auditory structures such as the inferior colliculus (IC). The serotonergic neuromodulatory system, present in the IC, is responsive to chronic changes in the activity of sensory systems. The current study investigated whether the density of serotonergic innervation in the IC is changed following acoustic trauma. The trauma stimulus consisted of an 8 kHz pure tone presented at a level of 113 dB SPL for six consecutive hours to anesthetized CBA/J mice. Following a minimum recovery period of three weeks, serotonergic fibers were visualized via histochemical techniques targeting the serotonin reuptake transporter (SERT) and quantified using stereologic probes. SERT-positive fiber densities were then compared between the traumatized and protected hemispheres of unilaterally traumatized subjects and those of controls. A significant effect of acoustic trauma was found between the hemispheres of unilaterally traumatized subjects such that the IC contralateral to the ear of exposure contained a lower density of SERT-positive fibers than the IC ipsilateral to acoustic trauma. No significant difference in density was found between the hemispheres of control subjects. Additional dimensions of variability in serotonergic fibers were seen among subdivisions of the IC and with age. The central IC had a slightly but significantly lowered density of serotonergic fibers than other subdivisions of the IC, and serotonergic fibers also declined with age. Overall, the results indicate that acoustic trauma is capable of producing modest but significant decreases in the density of serotonergic fibers innervating the IC.
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Wang H, Brozoski TJ, Caspary DM. Inhibitory neurotransmission in animal models of tinnitus: maladaptive plasticity. Hear Res 2011; 279:111-7. [PMID: 21527325 DOI: 10.1016/j.heares.2011.04.004] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2010] [Revised: 03/15/2011] [Accepted: 04/03/2011] [Indexed: 11/17/2022]
Abstract
Tinnitus is a phantom auditory sensation experienced by up to 14% of the United States population with a smaller percentage experiencing decreased quality of life. A compelling hypothesis is that tinnitus results from a maladaptive plastic net down-regulation of inhibitory amino acid neurotransmission in the central auditory pathway. This loss of inhibition may be a compensatory response to loss of afferent input such as that caused by acoustic insult and/or age-related hearing loss, the most common causes of tinnitus in people. Compensatory plastic changes may result in pathologic neural activity that underpins tinnitus. The neural correlates include increased spontaneous spiking, increased bursting and decreased variance of inter-spike intervals. This review will examine evidence for chronic plastic neuropathic changes in the central auditory system of animals with psychophysically-defined tinnitus. Neurochemical studies will focus on plastic tinnitus-related changes of inhibitory glycinergic neurotransmission in the adult dorsal cochlear nucleus (DCN). Electrophysiological studies will focus on functional changes in the DCN and inferior colliculus (IC). Tinnitus was associated with increased spontaneous activity and altered response properties of fusiform cells, the major output neurons of DCN. Coincident with these physiologic alterations were changes in glycine receptor (GlyR) subunit composition, its anchoring/trafficking protein, gephyrin and the number and affinity of membrane GlyRs revealed by receptor binding. In the IC, the primary afferent target of DCN fusiform cells, multi-dimensional alterations in unit-spontaneous activity (rate, burst rate, bursting pattern) were found in animals with behavioral evidence of chronic tinnitus more than 9 months following the acoustic/cochlear insult. In contrast, immediately following an intense sound exposure, acute alterations in IC spontaneous activity resembled chronic tinnitus-related changes but were not identical. This suggests that long-term neuroplastic changes responsible for chronic tinnitus are likely to be responsible for its persistence. A clear understanding of tinnitus-related plasticity in the central auditory system and its associated neurochemistry may help define unique targets for therapeutic drug development.
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Affiliation(s)
- Hongning Wang
- Department of Pharmacology, Southern Illinois University School of Medicine, P.O. Box 19629, Springfield, IL 62794-9629, USA
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Noreña AJ. An integrative model of tinnitus based on a central gain controlling neural sensitivity. Neurosci Biobehav Rev 2011; 35:1089-109. [PMID: 21094182 DOI: 10.1016/j.neubiorev.2010.11.003] [Citation(s) in RCA: 285] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2010] [Revised: 10/20/2010] [Accepted: 11/12/2010] [Indexed: 02/03/2023]
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Lee JH, Pradhan J, Maskey D, Park KS, Hong SH, Suh MW, Kim MJ, Ahn SC. Glutamate co-transmission from developing medial nucleus of the trapezoid body – Lateral superior olive synapses is cochlear dependent in kanamycin-treated rats. Biochem Biophys Res Commun 2011; 405:162-7. [DOI: 10.1016/j.bbrc.2010.12.129] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2010] [Accepted: 12/29/2010] [Indexed: 01/03/2023]
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Wang H, Brozoski TJ, Ling L, Hughes LF, Caspary DM. Impact of sound exposure and aging on brain-derived neurotrophic factor and tyrosine kinase B receptors levels in dorsal cochlear nucleus 80 days following sound exposure. Neuroscience 2011; 172:453-9. [PMID: 21034795 PMCID: PMC3057525 DOI: 10.1016/j.neuroscience.2010.10.056] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2010] [Revised: 10/18/2010] [Accepted: 10/19/2010] [Indexed: 11/22/2022]
Abstract
Recent studies suggested that acute sound exposure resulting in a temporary threshold shift in young adult animals within a series of maladaptive plasticity changes in central auditory structures. Brain-derived neurotrophic factor (BDNF), a member of the neurotrophin family, is involved in post-trauma peripheral hair cell and spiral ganglion cell survival and has been shown to modulate synaptic strength in cochlear nucleus following sound exposure. The present study evaluated levels of BDNF and its receptor (tyrosine kinase B, [TrkB]) in the dorsal cochlear nucleus (DCN) following a unilateral moderate sound exposure in young (7-8 months) and aged (28-29 months) Fischer Brown Norway (FBN) rats. Eighty days post-exposure, auditory brainstem response (ABR) thresholds for young exposed rats approached control values while aged exposed rats showed residual permanent threshold shifts (PTS) relative to aged controls. BDNF protein levels were significantly up-regulated by 9% in young exposed fusiform cells ipsilateral to the exposure. BDNF levels in aged sound-exposed fusiform cells increased 31% ipsilateral to the exposure. Protein levels of the BDNF receptor, TrkB, were also significantly increased in aged but not in young sound-exposed DCN fusiform cells. The present findings suggest a relationship between the up-regulation of BDNF/TrkB and the increase in spontaneous and driven activity previously observed for aged and sound-exposed fusiform cells. This might be due to a selective maladaptive compensatory down-regulation of glycinergic inhibition in DCN fusiform cells.
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MESH Headings
- Acoustic Stimulation/adverse effects
- Acoustic Stimulation/methods
- Aging/metabolism
- Animals
- Brain-Derived Neurotrophic Factor/biosynthesis
- Brain-Derived Neurotrophic Factor/metabolism
- Cell Survival/physiology
- Cochlear Nucleus/metabolism
- Cochlear Nucleus/pathology
- Cochlear Nucleus/physiopathology
- Disease Models, Animal
- Hearing Loss, Central/metabolism
- Hearing Loss, Central/pathology
- Hearing Loss, Central/physiopathology
- Hearing Loss, Noise-Induced/metabolism
- Hearing Loss, Noise-Induced/pathology
- Hearing Loss, Noise-Induced/physiopathology
- Male
- Noise/adverse effects
- Rats
- Rats, Inbred F344
- Receptor, trkB/biosynthesis
- Receptor, trkB/metabolism
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Affiliation(s)
- Hongning Wang
- Department of Pharmacology, Southern Illinois University School of Medicine, P.O. Box 19629, Springfield, IL 62794-9629, USA
| | - Thomas J. Brozoski
- Department of Surgery, Southern Illinois University School of Medicine, Springfield, IL 62794-9629, USA
| | - Lynne Ling
- Department of Pharmacology, Southern Illinois University School of Medicine, P.O. Box 19629, Springfield, IL 62794-9629, USA
| | - Larry F. Hughes
- Department of Surgery, Southern Illinois University School of Medicine, Springfield, IL 62794-9629, USA
| | - Donald M. Caspary
- Department of Pharmacology, Southern Illinois University School of Medicine, P.O. Box 19629, Springfield, IL 62794-9629, USA
- Department of Surgery, Southern Illinois University School of Medicine, Springfield, IL 62794-9629, USA
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Kaltenbach JA. Tinnitus: Models and mechanisms. Hear Res 2010; 276:52-60. [PMID: 21146597 DOI: 10.1016/j.heares.2010.12.003] [Citation(s) in RCA: 176] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/24/2010] [Revised: 12/02/2010] [Accepted: 12/03/2010] [Indexed: 10/18/2022]
Abstract
Over the past decade, there has been a burgeoning of scientific interest in the neurobiological origins of tinnitus. During this period, numerous behavioral and physiological animal models have been developed which have yielded major clues concerning the likely neural correlates of acute and chronic forms of tinnitus and the processes leading to their induction. The data increasingly converge on the view that tinnitus is a systemic problem stemming from imbalances in the excitatory and inhibitory inputs to auditory neurons. Such changes occur at multiple levels of the auditory system and involve a combination of interacting phenomena that are triggered by loss of normal input from the inner ear. This loss sets in motion a number of plastic readjustments in the central auditory system and sometimes beyond the auditory system that culminate in the induction of aberrant states of activation that include hyperactivity, bursting discharges and increases in neural synchrony. This article will review was has been learned about the biological origins of these alterations, summarize where they occur and examine the cellular and molecular mechanisms that are most likely to underlie them.
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Affiliation(s)
- James A Kaltenbach
- Department of Neurosciences, NE-63, Lerner Research Institute/Head and Neck Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44122, USA.
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