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Longridge NS, Mallinson AI. A New Perspective to Interpret How the Vestibular Efferent System Correlates the Complexity of Routine Balance Maintenance with Management of Emergency Fall Prevention Strategies. Audiol Res 2024; 14:518-544. [PMID: 38920965 PMCID: PMC11200673 DOI: 10.3390/audiolres14030044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2024] [Revised: 06/13/2024] [Accepted: 06/13/2024] [Indexed: 06/27/2024] Open
Abstract
Bipedalism is unique among mammals. Until modern times, a fall and resulting leg fracture could be fatal. Balance maintenance after a destabilizing event requires instantaneous decision making. The vestibular system plays an essential role in this process, initiating an emergency response. The afferent otolithic neural response is the first directionally oriented information to reach the cortex, and it can then be used to initiate an appropriate protective response. Some vestibular efferent axons feed directly into type I vestibular hair cells. This allows for rapid vestibular feedback via the striated organelle (STO), which has been largely ignored in most texts. We propose that this structure is essential in emergency fall prevention, and also that the system of sensory detection and resultant motor response works by having efferent movement information simultaneously transmitted to the maculae with the movement commands. This results in the otolithic membrane positioning itself precisely for the planned movement, and any error is due to an unexpected external cause. Error is fed back via the vestibular afferent system. The efferent system causes macular otolithic membrane movement through the STO, which occurs simultaneously with the initiating motor command. As a result, no vestibular afferent activity occurs unless an error must be dealt with.
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Affiliation(s)
| | - Arthur I. Mallinson
- Division of Otolaryngology, Department of Surgery, Faculty of Medicine, University of British Columbia, Vancouver, BC V5Z 1M9, Canada
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Sinha AK, Lee C, Holt JC. KCNQ2/3 regulates efferent mediated slow excitation of vestibular afferents in mammals. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.12.30.573731. [PMID: 38260489 PMCID: PMC10802244 DOI: 10.1101/2023.12.30.573731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Primary vestibular afferents transmit information from hair cells about head position and movement to the CNS, which is critical for maintaining balance, gaze stability and spatial navigation. The CNS, in turn, modulates hair cells and afferents via the efferent vestibular system (EVS) and its activation of several cholinergic signaling mechanisms. Electrical stimulation of EVS neurons gives rise to three kinetically- and mechanistically-distinct afferent responses including a slow excitation, a fast excitation, and a fast inhibition. EVS-mediated slow excitation is attributed to odd-numbered muscarinic acetylcholine receptors (mAChRs) on the afferent whose activation leads to the closure of a potassium conductance and increased afferent discharge. Likely effector candidates include low-threshold, voltage-gated potassium channels belonging to the KCNQ (Kv7.X) family, which are involved in neuronal excitability across the nervous system and are subject to mAChR modulation. Specifically, KCNQ2/3 heteromeric channels may be the molecular correlates for the M-current, a potassium current that is blocked following the activation of odd-numbered mAChRs. To this end, multiple members of the KCNQ channel family, including KCNQ2 and KCNQ3, are localized to several microdomains within vestibular afferent endings, where they influence afferent excitability and could be targeted by EVS neurons. Additionally, the relative expression of KCNQ subunits appears to vary across the sensory epithelia and among different afferent types. However, it is unclear which KCNQ channel subunits are targeted by mAChR activation and whether that also varies among different afferent classes. Here we show that EVS-mediated slow excitation is blocked and enhanced by the non-selective KCNQ channel blocker XE991 and opener retigabine, respectively. Using KCNQ subunit-selective drugs, we observed that a KCNQ2 blocker blocks the slow response in irregular afferents, while a KCNQ2/3 opener enhances slow responses in regular afferents. The KCNQ2 blockers did not appear to affect resting afferent discharge rates, while KCNQ2/3 or KCNQ2/4 openers decreased afferent excitability. Here, we show pharmacological evidence that KCNQ2/3 subunits are likely targeted by mAChR activation in mammalian vestibular afferents. Additionally, we show that KCNQ3 KO mice have altered resting discharge rate as well as EVS-mediated slow response. These data together suggest that KCNQ channels play a role in slow response and discharge rate of vestibular afferents, which can be modulated by EVS in mammals.
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Sinha AK, Lee C, Holt JC. Elucidating the role of muscarinic acetylcholine receptor (mAChR) signaling in efferent mediated responses of vestibular afferents in mammals. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.31.549902. [PMID: 37577578 PMCID: PMC10418111 DOI: 10.1101/2023.07.31.549902] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
The peripheral vestibular system detects head position and movement through activation of vestibular hair cells (HCs) in vestibular end organs. HCs transmit this information to the CNS by way of primary vestibular afferent neurons. The CNS, in turn, modulates HCs and afferents via the efferent vestibular system (EVS) through activation of cholinergic signaling mechanisms. In mice, we previously demonstrated that activation of muscarinic acetylcholine receptors (mAChRs), during EVS stimulation, gives rise to a slow excitation that takes seconds to peak and tens of seconds to decay back to baseline. This slow excitation is mimicked by muscarine and ablated by the non-selective mAChR blockers scopolamine, atropine, and glycopyrrolate. While five distinct mAChRs (M1-M5) exist, the subtype(s) driving EVS-mediated slow excitation remain unidentified and details on how these mAChRs alter vestibular function is not well understood. The objective of this study is to characterize which mAChR subtypes drive the EVS-mediated slow excitation, and how their activation impacts vestibular physiology and behavior. In C57Bl/6J mice, M3mAChR antagonists were more potent at blocking slow excitation than M1mAChR antagonists, while M2/M4 blockers were ineffective. While unchanged in M2/M4mAChR double KO mice, EVS-mediated slow excitation in M3 mAChR-KO animals were reduced or absent in irregular afferents but appeared unchanged in regular afferents. In agreement, vestibular sensory-evoked potentials (VsEP), known to be predominantly generated from irregular afferents, were significantly less enhanced by mAChR activation in M3mAChR-KO mice compared to controls. Finally, M3mAChR-KO mice display distinct behavioral phenotypes in open field activity, and thermal profiles, and balance beam and forced swim test. M3mAChRs mediate efferent-mediated slow excitation in irregular afferents, while M1mAChRs may drive the same process in regular afferents.
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Lorincz D, Drury HR, Smith DW, Lim R, Brichta AM. Aged mice are less susceptible to motion sickness and show decreased efferent vestibular activity compared to young adults. Brain Behav 2023; 13:e3064. [PMID: 37401009 PMCID: PMC10454360 DOI: 10.1002/brb3.3064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 04/13/2023] [Accepted: 05/03/2023] [Indexed: 07/05/2023] Open
Abstract
INTRODUCTION The efferent vestibular system (EVS) is a feedback circuit thought to modulate vestibular afferent activity by inhibiting type II hair cells and exciting calyx-bearing afferents in the peripheral vestibular organs. In a previous study, we suggested EVS activity may contribute to the effects of motion sickness. To determine an association between motion sickness and EVS activity, we examined the effects of provocative motion (PM) on c-Fos expression in brainstem efferent vestibular nucleus (EVN) neurons that are the source of efferent innervation in the peripheral vestibular organs. METHODS c-Fos is an immediate early gene product expressed in stimulated neurons and is a well-established marker of neuronal activation. To study the effects of PM, young adult C57/BL6 wild-type (WT), aged WT, and young adult transgenic Chat-gCaMP6f mice were exposed to PM, and tail temperature (Ttail ) was monitored using infrared imaging. After PM, we used immunohistochemistry to label EVN neurons to determine any changes in c-Fos expression. All tissue was imaged using laser scanning confocal microscopy. RESULTS Infrared recording of Ttail during PM indicated that young adult WT and transgenic mice displayed a typical motion sickness response (tail warming), but not in aged WT mice. Similarly, brainstem EVN neurons showed increased expression of c-Fos protein after PM in young adult WT and transgenic mice but not in aged cohorts. CONCLUSION We present evidence that motion sickness symptoms and increased activation of EVN neurons occur in young adult WT and transgenic mice in response to PM. In contrast, aged WT mice showed no signs of motion sickness and no change in c-Fos expression when exposed to the same provocative stimulus.
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Affiliation(s)
- David Lorincz
- School of Biomedical Sciences and PharmacyThe University of NewcastleCallaghanNew South WalesAustralia
| | - Hannah R. Drury
- School of Biomedical Sciences and PharmacyThe University of NewcastleCallaghanNew South WalesAustralia
| | - Doug W. Smith
- School of Biomedical Sciences and PharmacyThe University of NewcastleCallaghanNew South WalesAustralia
| | - Rebecca Lim
- School of Biomedical Sciences and PharmacyThe University of NewcastleCallaghanNew South WalesAustralia
| | - Alan M. Brichta
- School of Biomedical Sciences and PharmacyThe University of NewcastleCallaghanNew South WalesAustralia
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Poppi L, Bigland M, Cresswell E, Tabatabaee H, Lorincz D, Drury H, Callister R, Holt J, Lim R, Brichta A, Smith D. Molecular and Functional Changes to Postsynaptic Cholinergic Signaling in the Vestibular Sensory Organs of Aging C57BL/6 Mice. J Gerontol A Biol Sci Med Sci 2023; 78:920-929. [PMID: 36840917 PMCID: PMC10235202 DOI: 10.1093/gerona/glad067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Indexed: 02/26/2023] Open
Abstract
Cholinergic circuits in the central nervous system are vulnerable to age-related functional decline, but it is not known if aging impacts cholinergic signaling in the vestibular sensory organs, which are critically important to balance maintenance and visual gaze stability. We have previously shown cholinergic neurotransmission between vestibular efferent terminals and type II mechanosensory hair cells requires the alpha9 (Chrna9) nicotinic receptor subunit. Homozygous knockout of the alpha9 subunit causes vestibulo-ocular reflex adaptation deficits that mirror those observed in aged mice. This prompted examination of cholinergic signaling in the vestibular sensory organs of aged mice. We confirmed older (>24 months) mice had impaired performance in a balance beam task compared to young (3-4 months) adult mice. While there was no qualitative loss of cholinergic axon varicosities in the crista ampullaris of old mice, qPCR analysis revealed reduced expression of nicotinic receptor subunit genes Chrna1, Chrna9, and Chrna10 in the cristae of old relative to young mice. Functionally, single-cell patch clamp recordings taken from type II vestibular hair cells exposed to acetylcholine show reduced conductance through alpha9/10 subunit-containing nicotinic receptors in older mice, despite preserved passive membrane properties and voltage-activated conductances. These findings suggest that cholinergic signaling in the peripheral vestibular sensory organs is vulnerable to aging processes, manifesting in dynamic molecular and functional age-related changes. Given the importance of these organs to our everyday activities, and the dramatic increase in fall incidence in the older, further investigation into the mechanisms of altered peripheral vestibular function in older humans is warranted.
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Affiliation(s)
- Lauren A Poppi
- Neurobiology of Aging and Dementia and Vestibular Neurobiology Laboratories, School of Biomedical Sciences and Pharmacy, The University of Newcastle, Newcastle, New South Wales, Australia
- Hunter Medical Research Institute, Newcastle, New South Wales, Australia
| | - Mark J Bigland
- Neurobiology of Aging and Dementia and Vestibular Neurobiology Laboratories, School of Biomedical Sciences and Pharmacy, The University of Newcastle, Newcastle, New South Wales, Australia
- Hunter Medical Research Institute, Newcastle, New South Wales, Australia
| | - Ethan T Cresswell
- Neurobiology of Aging and Dementia and Vestibular Neurobiology Laboratories, School of Biomedical Sciences and Pharmacy, The University of Newcastle, Newcastle, New South Wales, Australia
- Hunter Medical Research Institute, Newcastle, New South Wales, Australia
| | - Hessam Tabatabaee
- Neurobiology of Aging and Dementia and Vestibular Neurobiology Laboratories, School of Biomedical Sciences and Pharmacy, The University of Newcastle, Newcastle, New South Wales, Australia
- Hunter Medical Research Institute, Newcastle, New South Wales, Australia
| | - David Lorincz
- Neurobiology of Aging and Dementia and Vestibular Neurobiology Laboratories, School of Biomedical Sciences and Pharmacy, The University of Newcastle, Newcastle, New South Wales, Australia
- Hunter Medical Research Institute, Newcastle, New South Wales, Australia
| | - Hannah R Drury
- Neurobiology of Aging and Dementia and Vestibular Neurobiology Laboratories, School of Biomedical Sciences and Pharmacy, The University of Newcastle, Newcastle, New South Wales, Australia
- Hunter Medical Research Institute, Newcastle, New South Wales, Australia
| | - Robert J Callister
- Neurobiology of Aging and Dementia and Vestibular Neurobiology Laboratories, School of Biomedical Sciences and Pharmacy, The University of Newcastle, Newcastle, New South Wales, Australia
- Hunter Medical Research Institute, Newcastle, New South Wales, Australia
| | - Joseph C Holt
- Department of Otolaryngology, University of Rochester Medical Center, Rochester, New York, USA
| | - Rebecca Lim
- Neurobiology of Aging and Dementia and Vestibular Neurobiology Laboratories, School of Biomedical Sciences and Pharmacy, The University of Newcastle, Newcastle, New South Wales, Australia
- Hunter Medical Research Institute, Newcastle, New South Wales, Australia
| | - Alan M Brichta
- Neurobiology of Aging and Dementia and Vestibular Neurobiology Laboratories, School of Biomedical Sciences and Pharmacy, The University of Newcastle, Newcastle, New South Wales, Australia
- Hunter Medical Research Institute, Newcastle, New South Wales, Australia
| | - Doug W Smith
- Neurobiology of Aging and Dementia and Vestibular Neurobiology Laboratories, School of Biomedical Sciences and Pharmacy, The University of Newcastle, Newcastle, New South Wales, Australia
- Hunter Medical Research Institute, Newcastle, New South Wales, Australia
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Greguske EA, Maroto AF, Borrajo M, Palou A, Gut M, Esteve-Codina A, Barrallo-Gimeno A, Llorens J. Decreased expression of synaptic genes in the vestibular ganglion of rodents following subchronic ototoxic stress. Neurobiol Dis 2023; 182:106134. [PMID: 37100209 DOI: 10.1016/j.nbd.2023.106134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 04/14/2023] [Accepted: 04/23/2023] [Indexed: 04/28/2023] Open
Abstract
The vestibular ganglion contains primary sensory neurons that are postsynaptic to the transducing hair cells (HC) and project to the central nervous system. Understanding the response of these neurons to HC stress or loss is of great interest as their survival and functional competence will determine the functional outcome of any intervention aiming at repair or regeneration of the HCs. We have shown that subchronic exposure to the ototoxicant 3,3'-iminodipropionitrile (IDPN) in rats and mice causes a reversible detachment and synaptic uncoupling between the HCs and the ganglion neurons. Here, we used this paradigm to study the global changes in gene expression in vestibular ganglia using RNA-seq. Comparative gene ontology and pathway analyses of the data from both model species indicated a robust downregulation of terms related to synapses, including presynaptic and postsynaptic functions. Manual analyses of the most significantly downregulated transcripts identified genes with expressions related to neuronal activity, modulators of neuronal excitability, and transcription factors and receptors that promote neurite growth and differentiation. For choice selected genes, the mRNA expression results were replicated by qRT-PCR, validated spatially by RNA-scope, or were demonstrated to be associated with decreased expression of the corresponding protein. We conjectured that decreased synaptic input or trophic support on the ganglion neurons from the HC was triggering these expression changes. To support this hypothesis, we demonstrated decreased expression of BDNF mRNA in the vestibular epithelium after subchronic ototoxicity and also downregulated expression of similarly identified genes (e.g Etv5, Camk1g, Slc17a6, Nptx2, Spp1) after HC ablation with another ototoxic compound, allylnitrile. We conclude that vestibular ganglion neurons respond to decreased input from HCs by decreasing the strength of all their synaptic contacts, both as postsynaptic and presynaptic players.
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Affiliation(s)
- Erin A Greguske
- Departament de Ciències Fisiològiques, Universitat de Barcelona, Feixa Llarga s/n, 08907 l'Hospitalet de Llobregat, Catalunya, Spain; Institut de Neurociènces, Universitat de Barcelona, Barcelona, Catalunya, Spain; Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), 08907 l'Hospitalet de Llobregat, Catalunya, Spain
| | - Alberto F Maroto
- Departament de Ciències Fisiològiques, Universitat de Barcelona, Feixa Llarga s/n, 08907 l'Hospitalet de Llobregat, Catalunya, Spain; Institut de Neurociènces, Universitat de Barcelona, Barcelona, Catalunya, Spain; Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), 08907 l'Hospitalet de Llobregat, Catalunya, Spain
| | - Mireia Borrajo
- Departament de Ciències Fisiològiques, Universitat de Barcelona, Feixa Llarga s/n, 08907 l'Hospitalet de Llobregat, Catalunya, Spain; Institut de Neurociènces, Universitat de Barcelona, Barcelona, Catalunya, Spain; Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), 08907 l'Hospitalet de Llobregat, Catalunya, Spain.
| | - Aïda Palou
- Departament de Ciències Fisiològiques, Universitat de Barcelona, Feixa Llarga s/n, 08907 l'Hospitalet de Llobregat, Catalunya, Spain; Institut de Neurociènces, Universitat de Barcelona, Barcelona, Catalunya, Spain; Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), 08907 l'Hospitalet de Llobregat, Catalunya, Spain.
| | - Marta Gut
- CNAG-CRG, Centre for Genomic Regulation, Barcelona Institute of Science and Technology (BIST), Barcelona, Spain; Universitat Pompeu Fabra, Barcelona, Spain.
| | - Anna Esteve-Codina
- CNAG-CRG, Centre for Genomic Regulation, Barcelona Institute of Science and Technology (BIST), Barcelona, Spain; Universitat Pompeu Fabra, Barcelona, Spain.
| | - Alejandro Barrallo-Gimeno
- Departament de Ciències Fisiològiques, Universitat de Barcelona, Feixa Llarga s/n, 08907 l'Hospitalet de Llobregat, Catalunya, Spain; Institut de Neurociènces, Universitat de Barcelona, Barcelona, Catalunya, Spain; Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), 08907 l'Hospitalet de Llobregat, Catalunya, Spain.
| | - Jordi Llorens
- Departament de Ciències Fisiològiques, Universitat de Barcelona, Feixa Llarga s/n, 08907 l'Hospitalet de Llobregat, Catalunya, Spain; Institut de Neurociènces, Universitat de Barcelona, Barcelona, Catalunya, Spain; Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), 08907 l'Hospitalet de Llobregat, Catalunya, Spain.
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Bronson D, Kalluri R. Muscarinic Acetylcholine Receptors Modulate HCN Channel Properties in Vestibular Ganglion Neurons. J Neurosci 2023; 43:902-917. [PMID: 36604171 PMCID: PMC9908319 DOI: 10.1523/jneurosci.2552-21.2022] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Revised: 12/14/2022] [Accepted: 12/22/2022] [Indexed: 01/07/2023] Open
Abstract
Efferent modulation of vestibular afferent excitability is linked to muscarinic signaling cascades that close low-voltage-gated potassium channels (i.e., KCNQ). Here, we show that muscarinic signaling cascades also depolarize the activation range of hyperpolarization-activated cyclic-nucleotide gated (HCN) channels. We compared the voltage activation range and kinetics of HCN channels and induced firing patterns before and after administering the muscarinic acetylcholine receptor (mAChR) agonist oxotremorine-M (Oxo-M) in dissociated vestibular ganglion neurons (VGNs) from rats of either sex using perforated whole-cell patch-clamp methods. Oxo-M depolarized HCN channels' half-activation voltage (V 1/2) and sped up the rate of activation near resting potential twofold. HCN channels in large-diameter and/or transient firing VGN (putative cell bodies of irregular firing neuron from central epithelial zones) had relatively depolarized V 1/2 in control solution and were less sensitive to mAChR activation than those found in small-diameter VGN with sustained firing patterns (putatively belonging to regular firing afferents). The impact of mAChR on HCN channels is not a direct consequence of closing KCNQ channels since pretreating the cells with Linopirdine, a KCNQ channel blocker, did not prevent HCN channel depolarization by Oxo-M. Efferent signaling promoted ion channel configurations that were favorable to highly regular spiking in some VGN, but not others. This is consistent with previous observations that low-voltage gated potassium currents in VGN are conducted by mAChR agonist-sensitive and -insensitive channels. Connecting efferent signaling to HCN channels is significant because of the channel's impact on spike-timing regularity and nonchemical transmission between Type I hair cells and vestibular afferents.SIGNIFICANCE STATEMENT Vestibular afferents express a diverse complement of ion channels. In vitro studies identified low-voltage activated potassium channels and hyperpolarization-activated cyclic-nucleotide gated (HCN) channels as crucial for shaping the timing and sensitivity of afferent responses. Moreover, a network of acetylcholine-releasing efferent neurons controls afferent excitability by closing a subgroup of low-voltage activated potassium channels on the afferent neuron. This work shows that these efferent signaling cascades also enhance the activation of HCN channels by depolarizing their voltage activation range. The size of this effect varies depending on the endogenous properties of the HCN channel and on cell type (as determined by discharge patterns and cell size). Simultaneously controlling two ion-channel groups gives the vestibular efferent system exquisite control over afferent neuron activity.
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Affiliation(s)
- Daniel Bronson
- Hearing and Communications Neuroscience Training Program, University of Southern California, Los Angeles, California 90057
- Department of Otolaryngology-Head and Neck Surgery, Keck School of Medicine, University of Southern California, Los Angeles, California 90057
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90057
| | - Radha Kalluri
- Hearing and Communications Neuroscience Training Program, University of Southern California, Los Angeles, California 90057
- Department of Otolaryngology-Head and Neck Surgery, Keck School of Medicine, University of Southern California, Los Angeles, California 90057
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90057
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Mukhopadhyay M, Pangrsic T. Synaptic transmission at the vestibular hair cells of amniotes. Mol Cell Neurosci 2022; 121:103749. [PMID: 35667549 DOI: 10.1016/j.mcn.2022.103749] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2021] [Revised: 05/09/2022] [Accepted: 06/01/2022] [Indexed: 11/19/2022] Open
Abstract
A harmonized interplay between the central nervous system and the five peripheral end organs is how the vestibular system helps organisms feel a sense of balance and motion in three-dimensional space. The receptor cells of this system, much like their cochlear equivalents, are the specialized hair cells. However, research over the years has shown that the vestibular endorgans and hair cells evolved very differently from their cochlear counterparts. The structurally unique calyceal synapse, which appeared much later in the evolutionary time scale, and continues to intrigue researchers, is now known to support several forms of synaptic neurotransmission. The conventional quantal transmission is believed to employ the ribbon structures, which carry several tethered vesicles filled with neurotransmitters. However, the field of vestibular hair cell synaptic molecular anatomy is still at a nascent stage and needs further work. In this review, we will touch upon the basic structure and function of the peripheral vestibular system, with the focus on the various modes of neurotransmission at the type I vestibular hair cells. We will also shed light on the current knowledge about the molecular anatomy of the vestibular hair cell synapses and vestibular synaptopathy.
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Affiliation(s)
- Mohona Mukhopadhyay
- Experimental Otology Group, InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, and Institute for Auditory Neuroscience, 37075 Göttingen, Germany
| | - Tina Pangrsic
- Experimental Otology Group, InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, and Institute for Auditory Neuroscience, 37075 Göttingen, Germany; Auditory Neuroscience Group, Max Planck Institute for Multidisciplinary Sciences, 37075 Göttingen, Germany; Collaborative Research Center 889, University of Göttingen, Göttingen, Germany; Multiscale Bioimaging Cluster of Excellence (MBExC), University of Göttingen, 37075 Göttingen, Germany.
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Sadeghi SG, Géléoc GSG. Editorial: Commonalities and Differences in Vestibular and Auditory Pathways. Front Neurosci 2022; 16:876798. [PMID: 35401079 PMCID: PMC8984178 DOI: 10.3389/fnins.2022.876798] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 02/24/2022] [Indexed: 11/13/2022] Open
Affiliation(s)
- Soroush G. Sadeghi
- Center for Hearing and Deafness, Department of Communicative Disorders and Science, University at Buffalo, Buffalo, NY, United States
- *Correspondence: Soroush G. Sadeghi
| | - Gwenaëlle S. G. Géléoc
- Boston Children's Hospital and Harvard Medical School, Boston, MA, United States
- Gwenaëlle S. G. Géléoc
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Lorincz D, Poppi LA, Holt JC, Drury HR, Lim R, Brichta AM. The Long and Winding Road-Vestibular Efferent Anatomy in Mice. Front Neural Circuits 2022; 15:751850. [PMID: 35153679 PMCID: PMC8832101 DOI: 10.3389/fncir.2021.751850] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Accepted: 12/23/2021] [Indexed: 11/20/2022] Open
Abstract
The precise functional role of the Efferent Vestibular System (EVS) is still unclear, but the auditory olivocochlear efferent system has served as a reasonable model on the effects of a cholinergic and peptidergic input on inner ear organs. However, it is important to appreciate the similarities and differences in the structure of the two efferent systems, especially within the same animal model. Here, we examine the anatomy of the mouse EVS, from its central origin in the Efferent Vestibular Nucleus (EVN) of the brainstem, to its peripheral terminations in the vestibular organs, and we compare these findings to known mouse olivocochlear anatomy. Using transgenic mouse lines and two different tracing strategies, we examine central and peripheral anatomical patterning, as well as the anatomical pathway of EVS axons as they leave the mouse brainstem. We separately tag the left and right efferent vestibular nuclei (EVN) using Cre-dependent, adeno-associated virus (AAV)-mediated expression of fluorescent reporters to map their central trajectory and their peripheral terminal fields. We couple this with Fluro-Gold retrograde labeling to quantify the proportion of ipsi- and contralaterally projecting cholinergic efferent neurons. As in some other mammals, the mouse EVN comprises one group of neurons located dorsal to the facial genu, close to the vestibular nuclei complex (VNC). There is an average of just 53 EVN neurons with rich dendritic arborizations towards the VNC. The majority of EVN neurons, 55%, project to the contralateral eighth nerve, crossing the midline rostral to the EVN, and 32% project to the ipsilateral eighth nerve. The vestibular organs, therefore, receive bilateral EVN innervation, but without the distinctive zonal innervation patterns suggested in gerbil. Similar to gerbil, however, our data also suggest that individual EVN neurons do not project bilaterally in mice. Taken together, these data provide a detailed map of EVN neurons from the brainstem to the periphery and strong anatomical support for a dominant contralateral efferent innervation in mammals.
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Affiliation(s)
- David Lorincz
- School of Biomedical Sciences and Pharmacy, The University of Newcastle, Callaghan, NSW, Australia
| | - Lauren A. Poppi
- School of Biomedical Sciences and Pharmacy, The University of Newcastle, Callaghan, NSW, Australia
| | - Joseph C. Holt
- Department of Otolaryngology, University of Rochester, Rochester, NY, United States
| | - Hannah R. Drury
- School of Biomedical Sciences and Pharmacy, The University of Newcastle, Callaghan, NSW, Australia
| | - Rebecca Lim
- School of Biomedical Sciences and Pharmacy, The University of Newcastle, Callaghan, NSW, Australia
| | - Alan M. Brichta
- School of Biomedical Sciences and Pharmacy, The University of Newcastle, Callaghan, NSW, Australia
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Chang HHV, Morley BJ, Cullen KE. Loss of α-9 Nicotinic Acetylcholine Receptor Subunit Predominantly Results in Impaired Postural Stability Rather Than Gaze Stability. Front Cell Neurosci 2022; 15:799752. [PMID: 35095424 PMCID: PMC8792779 DOI: 10.3389/fncel.2021.799752] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Accepted: 11/29/2021] [Indexed: 11/13/2022] Open
Abstract
The functional role of the mammalian efferent vestibular system (EVS) is not fully understood. One proposal is that the mammalian EVS plays a role in the long-term calibration of central vestibular pathways, for example during development. Here to test this possibility, we studied vestibular function in mice lacking a functional α9 subunit of the nicotinic acetylcholine receptor (nAChR) gene family, which mediates efferent activation of the vestibular periphery. We focused on an α9 (−/−) model with a deletion in exons 1 and 2. First, we quantified gaze stability by testing vestibulo-ocular reflex (VOR, 0.2–3 Hz) responses of both α9 (−/−) mouse models in dark and light conditions. VOR gains and phases were comparable for both α9 (−/−) mutants and wild-type controls. Second, we confirmed the lack of an effect from the α9 (−/−) mutation on central visuo-motor pathways/eye movement pathways via analyses of the optokinetic reflex (OKR) and quick phases of the VOR. We found no differences between α9 (−/−) mutants and wild-type controls. Third and finally, we investigated postural abilities during instrumented rotarod and balance beam tasks. Head movements were quantified using a 6D microelectromechanical systems (MEMS) module fixed to the mouse’s head. Compared to wild-type controls, we found head movements were strikingly altered in α9 (−/−) mice, most notably in the pitch axis. We confirmed these later results in another α9 (−/−) model, with a deletion in the exon 4 region. Overall, we conclude that the absence of the α9 subunit of nAChRs predominately results in an impairment of posture rather than gaze.
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Affiliation(s)
| | - Barbara J. Morley
- Center for Sensory Neuroscience, Boys Town National Research Hospital, Omaha, NE, United States
| | - Kathleen E. Cullen
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, United States
- Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD, United States
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, United States
- Kavli Neuroscience Discovery Institute, Johns Hopkins University, Baltimore, MD, United States
- *Correspondence: Kathleen E. Cullen,
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12
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Lee C, Sinha AK, Henry K, Walbaum AW, Crooks PA, Holt JC. Characterizing the Access of Cholinergic Antagonists to Efferent Synapses in the Inner Ear. Front Neurosci 2022; 15:754585. [PMID: 34970112 PMCID: PMC8712681 DOI: 10.3389/fnins.2021.754585] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 11/15/2021] [Indexed: 11/13/2022] Open
Abstract
Stimulation of cholinergic efferent neurons innervating the inner ear has profound, well-characterized effects on vestibular and auditory physiology, after activating distinct ACh receptors (AChRs) on afferents and hair cells in peripheral endorgans. Efferent-mediated fast and slow excitation of vestibular afferents are mediated by α4β2*-containing nicotinic AChRs (nAChRs) and muscarinic AChRs (mAChRs), respectively. On the auditory side, efferent-mediated suppression of distortion product otoacoustic emissions (DPOAEs) is mediated by α9α10nAChRs. Previous characterization of these synaptic mechanisms utilized cholinergic drugs, that when systemically administered, also reach the CNS, which may limit their utility in probing efferent function without also considering central effects. Use of peripherally-acting cholinergic drugs with local application strategies may be useful, but this approach has remained relatively unexplored. Using multiple administration routes, we performed a combination of vestibular afferent and DPOAE recordings during efferent stimulation in mouse and turtle to determine whether charged mAChR or α9α10nAChR antagonists, with little CNS entry, can still engage efferent synaptic targets in the inner ear. The charged mAChR antagonists glycopyrrolate and methscopolamine blocked efferent-mediated slow excitation of mouse vestibular afferents following intraperitoneal, middle ear, or direct perilymphatic administration. Both mAChR antagonists were effective when delivered to the middle ear, contralateral to the side of afferent recordings, suggesting they gain vascular access after first entering the perilymphatic compartment. In contrast, charged α9α10nAChR antagonists blocked efferent-mediated suppression of DPOAEs only upon direct perilymphatic application, but failed to reach efferent synapses when systemically administered. These data show that efferent mechanisms are viable targets for further characterizing drug access in the inner ear.
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Affiliation(s)
- Choongheon Lee
- Department of Otolaryngology, University of Rochester, Rochester, NY, United States
| | - Anjali K Sinha
- Department of Neuroscience, University of Rochester, Rochester, NY, United States
| | - Kenneth Henry
- Department of Otolaryngology, University of Rochester, Rochester, NY, United States.,Department of Neuroscience, University of Rochester, Rochester, NY, United States
| | - Anqi W Walbaum
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Peter A Crooks
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Joseph C Holt
- Department of Otolaryngology, University of Rochester, Rochester, NY, United States.,Department of Neuroscience, University of Rochester, Rochester, NY, United States.,Department of Pharmacology & Physiology, University of Rochester, Rochester, NY, United States
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13
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Di Mizio G, Marcianò G, Palleria C, Muraca L, Rania V, Roberti R, Spaziano G, Piscopo A, Ciconte V, Di Nunno N, Esposito M, Viola P, Pisani D, De Sarro G, Raffi M, Piras A, Chiarella G, Gallelli L. Drug-Drug Interactions in Vestibular Diseases, Clinical Problems, and Medico-Legal Implications. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2021; 18:12936. [PMID: 34948545 PMCID: PMC8701970 DOI: 10.3390/ijerph182412936] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Revised: 11/28/2021] [Accepted: 12/03/2021] [Indexed: 12/23/2022]
Abstract
Peripheral vestibular disease can be treated with several approaches (e.g., maneuvers, surgery, or medical approach). Comorbidity is common in elderly patients, so polytherapy is used, but it can generate the development of drug-drug interactions (DDIs) that play a role in both adverse drug reactions and reduced adherence. For this reason, they need a complex kind of approach, considering all their individual characteristics. Physicians must be able to prescribe and deprescribe drugs based on a solid knowledge of pharmacokinetics, pharmacodynamics, and clinical indications. Moreover, full information is required to reach a real therapeutic alliance, to improve the safety of care and reduce possible malpractice claims related to drug-drug interactions. In this review, using PubMed, Embase, and Cochrane library, we searched articles published until 30 August 2021, and described both pharmacokinetic and pharmacodynamic DDIs in patients with vestibular disorders, focusing the interest on their clinical implications and on risk management strategies.
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Affiliation(s)
- Giulio Di Mizio
- Department of Law, Magna Graecia University of Catanzaro, 88100 Catanzaro, Italy
| | - Gianmarco Marcianò
- Department of Health Science, School of Medicine, University of Catanzaro, Clinical Pharmacology and Pharmacovigilance Unit, Mater Domini Hospital, 88100 Catanzaro, Italy
| | - Caterina Palleria
- Department of Health Science, School of Medicine, University of Catanzaro, Clinical Pharmacology and Pharmacovigilance Unit, Mater Domini Hospital, 88100 Catanzaro, Italy
| | - Lucia Muraca
- Department of Health Science, School of Medicine, University of Catanzaro, Clinical Pharmacology and Pharmacovigilance Unit, Mater Domini Hospital, 88100 Catanzaro, Italy
- Department of Primary Care, ASP 7, 88100 Catanzaro, Italy
| | - Vincenzo Rania
- Department of Health Science, School of Medicine, University of Catanzaro, Clinical Pharmacology and Pharmacovigilance Unit, Mater Domini Hospital, 88100 Catanzaro, Italy
| | - Roberta Roberti
- Department of Health Science, School of Medicine, University of Catanzaro, Clinical Pharmacology and Pharmacovigilance Unit, Mater Domini Hospital, 88100 Catanzaro, Italy
| | - Giuseppe Spaziano
- Department of Experimental Medicine L. Donatelli, Section of Pharmacology, School of Medicine, University of Campania Luigi Vanvitelli, 80123 Naples, Italy
| | - Amalia Piscopo
- Department of Law, Magna Graecia University of Catanzaro, 88100 Catanzaro, Italy
| | - Valeria Ciconte
- Department of Law, Magna Graecia University of Catanzaro, 88100 Catanzaro, Italy
- Department of Health Science, School of Medicine, University of Catanzaro, Clinical Pharmacology and Pharmacovigilance Unit, Mater Domini Hospital, 88100 Catanzaro, Italy
| | - Nunzio Di Nunno
- Department of History, Society and Studies on Humanity, University of Salento, 83100 Lecce, Italy
| | - Massimiliano Esposito
- Department of Medical, Surgical Sciences and Advanced Technologies "G. F. Ingrassia", University of Catania, 95121 Catania, Italy
| | - Pasquale Viola
- Unit of Audiology, Department of Experimental and Clinical Medicine, Regional Centre of Cochlear Implants and ENT Diseases, Magna Graecia University, 88100 Catanzaro, Italy
| | - Davide Pisani
- Unit of Audiology, Department of Experimental and Clinical Medicine, Regional Centre of Cochlear Implants and ENT Diseases, Magna Graecia University, 88100 Catanzaro, Italy
| | - Giovambattista De Sarro
- Department of Health Science, School of Medicine, University of Catanzaro, Clinical Pharmacology and Pharmacovigilance Unit, Mater Domini Hospital, 88100 Catanzaro, Italy
- Research Center FAS@UMG, Department of Health Science, University of Catanzaro, 88100 Catanzaro, Italy
| | - Milena Raffi
- Department of Biomedical and Neuromotor Sciences, University of Bologna, 40126 Bologna, Italy
| | - Alessandro Piras
- Department of Biomedical and Neuromotor Sciences, University of Bologna, 40126 Bologna, Italy
| | - Giuseppe Chiarella
- Unit of Audiology, Department of Experimental and Clinical Medicine, Regional Centre of Cochlear Implants and ENT Diseases, Magna Graecia University, 88100 Catanzaro, Italy
| | - Luca Gallelli
- Department of Health Science, School of Medicine, University of Catanzaro, Clinical Pharmacology and Pharmacovigilance Unit, Mater Domini Hospital, 88100 Catanzaro, Italy
- Research Center FAS@UMG, Department of Health Science, University of Catanzaro, 88100 Catanzaro, Italy
- Medifarmagen SRL, University of Catanzaro, 88100 Catanzaro, Italy
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Cullen KE, Wei RH. Differences in the Structure and Function of the Vestibular Efferent System Among Vertebrates. Front Neurosci 2021; 15:684800. [PMID: 34248486 PMCID: PMC8260987 DOI: 10.3389/fnins.2021.684800] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Accepted: 05/13/2021] [Indexed: 11/13/2022] Open
Abstract
The role of the mammalian vestibular efferent system in everyday life has been a long-standing mystery. In contrast to what has been reported in lower vertebrate classes, the mammalian vestibular efferent system does not appear to relay inputs from other sensory modalities to the vestibular periphery. Furthermore, to date, the available evidence indicates that the mammalian vestibular efferent system does not relay motor-related signals to the vestibular periphery to modulate sensory coding of the voluntary self-motion generated during natural behaviors. Indeed, our recent neurophysiological studies have provided insight into how the peripheral vestibular system transmits head movement-related information to the brain in a context independent manner. The integration of vestibular and extra-vestibular information instead only occurs at next stage of the mammalian vestibular system, at the level of the vestibular nuclei. The question thus arises: what is the physiological role of the vestibular efferent system in mammals? We suggest that the mammalian vestibular efferent system does not play a significant role in short-term modulation of afferent coding, but instead plays a vital role over a longer time course, for example in calibrating and protecting the functional efficacy of vestibular circuits during development and aging in a role analogous the auditory efferent system.
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Affiliation(s)
- Kathleen E. Cullen
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, United States
- Department of Otolaryngology, Johns Hopkins University School of Medicine, Baltimore, MD, United States
- Department of Neuroscience, Johns Hopkins University, Baltimore, MD, United States
- Kavli Neuroscience Discovery Institute, Johns Hopkins University, Baltimore, MD, United States
| | - Rui-Han Wei
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, United States
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