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Fogarty MJ, Drieberg-Thompson JR, Bellingham MC, Noakes PG. Timeline of hypoglossal motor neuron death and intrinsic tongue muscle denervation in high-copy number SOD1 G93A mice. Front Neurol 2024; 15:1422943. [PMID: 39119557 PMCID: PMC11306148 DOI: 10.3389/fneur.2024.1422943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2024] [Accepted: 07/10/2024] [Indexed: 08/10/2024] Open
Abstract
In amyotrophic lateral sclerosis (ALS) postmortem tissue and the SOD1 mouse model at mid-disease, death of hypoglossal motor neurons (XII MNs) is evident. These XII MNs innervate the intrinsic and extrinsic tongue muscles, and despite their importance in many oral and lingual motor behaviours that are affected by ALS (e.g., swallowing, speech, and respiratory functions), little is known about the timing and extent of tongue muscle denervation. Here in the well-characterised SOD1G93A (high-copy) mouse model, we evaluated XII MN numbers and intrinsic tongue muscle innervation using standard histopathological approaches, which included stereological evaluation of Nissl-stained brainstem, and the presynaptic and postsynaptic evaluation of neuromuscular junctions (NMJs), using synapsin, neurofilament, and α-bungarotoxin immunolabelling, at presymptomatic, onset, mid-disease, and endstage timepoints. We found that reduction in XII MN size at onset preceded reduced XII MN survival, while the denervation of tongue muscle did not appear until the endstage. Our study suggests that denervation-induced weakness may not be the most pertinent feature of orolingual deficits in ALS. Efforts to preserve oral and respiratory functions of XII MNs are incredibly important if we are to influence patient outcomes.
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Affiliation(s)
- Matthew J. Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States
- School of Biomedical Sciences, St Lucia, QLD, Australia
| | | | | | - Peter G. Noakes
- School of Biomedical Sciences, St Lucia, QLD, Australia
- Queensland Brain Institute, St Lucia, QLD, Australia
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Rudy SL, Wealing JC, Banayat T, Black C, Funk GD, Revill AL. A muscarinic, GIRK channel-mediated inhibition of inspiratory-related XII nerve motor output emerges in early postnatal development in mice. J Appl Physiol (1985) 2023; 135:1041-1052. [PMID: 37767557 PMCID: PMC10911762 DOI: 10.1152/japplphysiol.00042.2023] [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: 01/19/2023] [Revised: 09/06/2023] [Accepted: 09/21/2023] [Indexed: 09/29/2023] Open
Abstract
In neonatal rhythmic medullary slices, muscarinic acetylcholine receptor (mAChR) activation of hypoglossal (XII) motoneurons that innervate the tongue has a net excitatory effect on XII inspiratory motor output. Conversely, during rapid eye movement sleep in adult rodents, XII motoneurons experience a loss of excitability partly due to activation of mAChRs. This may be mediated by activation of G-protein-coupled inwardly rectifying potassium (GIRK) channels. Therefore, this study was designed to evaluate whether muscarinic modulation of XII inspiratory motor output in mouse rhythmic medullary slices includes GIRK channel-mediated inhibition and, if so, when this inhibitory mechanism emerges. Local pressure injection of the mAChR agonist muscarine potentiated inspiratory bursting by 150 ± 28% in postnatal day (P)0-P5 rhythmic medullary slice preparations. In the absence of muscarine, pharmacological GIRK channel block by Tertiapin-Q did not affect inspiratory burst parameters, whereas activation with ML297 decreased inspiratory burst area. Blocking GIRK channels by local preapplication of Tertiapin-Q revealed a developmental change in muscarinic modulation of inspiratory bursting. In P0-P2 rhythmic medullary slices, Tertiapin-Q preapplication had no significant effect on muscarinic potentiation of inspiratory bursting (a negligible 6% decrease). However, preapplication of Tertiapin-Q to P3-P5 rhythmic medullary slices caused a 19% increase in muscarinic potentiation of XII inspiratory burst amplitude. Immunofluorescence experiments revealed expression of GIRK 1 and 2 subunits and M1, M2, M3, and M5 mAChRs from P0 to P5. Overall, these data support that mechanisms underlying muscarinic modulation of inspiratory burst activity change postnatally and that potent GIRK-mediated inhibition described in adults emerges early in postnatal life.NEW & NOTEWORTHY Muscarinic modulation of inspiratory bursting at hypoglossal motoneurons has a net excitatory effect in neonatal rhythmic medullary slice preparations and a net inhibitory effect in adult animals. We demonstrate that muscarinic modulation of inspiratory bursting undergoes maturational changes from postnatal days 0 to 5 that include emergence of an inhibitory component mediated by G-protein-coupled inwardly rectifying potassium channels after postnatal day 3 in neonatal mouse rhythmic medullary slice preparations.
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Affiliation(s)
- Samantha L Rudy
- Arizona College of Osteopathic Medicine, Midwestern University, Glendale, Arizona, United States
| | - Jesse C Wealing
- Arizona College of Osteopathic Medicine, Midwestern University, Glendale, Arizona, United States
| | - Tatum Banayat
- Department of Physiology, College of Graduate Studies, Midwestern University, Glendale, Arizona, United States
| | - Chody Black
- Arizona College of Osteopathic Medicine, Midwestern University, Glendale, Arizona, United States
| | - Gregory D Funk
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada
- Women and Children's Health Research Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Ann L Revill
- Arizona College of Osteopathic Medicine, Midwestern University, Glendale, Arizona, United States
- Department of Physiology, College of Graduate Studies, Midwestern University, Glendale, Arizona, United States
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Bolte KN, Wealing JC, Revill AL. Arginine vasopressin potentiates inspiratory bursting in hypoglossal motoneurons of neonatal mice. Respir Physiol Neurobiol 2023; 314:104087. [PMID: 37269889 PMCID: PMC10443434 DOI: 10.1016/j.resp.2023.104087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 05/24/2023] [Accepted: 05/26/2023] [Indexed: 06/05/2023]
Abstract
Vasopressin (AVP) acts as a neurotransmitter and its activity can potentiate respiratory activity. Hypoglossal (XII) motoneurons that innervate the tongue express V1a vasopressin receptors, which are excitatory. Therefore, we hypothesized that V1a receptor activation at XII motoneurons would potentiate inspiratory bursting. We developed this study to determine whether AVP can potentiate inspiratory bursting in rhythmic medullary slice preparations in neonatal (postnatal, P0-5) mice. Bath or local application of AVP potentiated inspiratory bursting compared to baseline XII inspiratory burst amplitude. Antagonizing V1a receptors revealed significant attenuation of the AVP-mediated potentiation of inspiratory bursting, while antagonism of oxytocin receptors (at which AVP has similar binding affinity) revealed a trend to attenuate AVP-mediated potentiation of inspiratory bursting. Finally, we discovered that the AVP-mediated potentiation of inspiratory bursting increases significantly with postnatal maturation from P0-5. Overall, these data support that AVP potentiates inspiratory bursting directly at XII motoneurons.
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Affiliation(s)
- K N Bolte
- Arizona College of Osteopathic Medicine, Midwestern University, Glendale, AZ, United States
| | - J C Wealing
- Arizona College of Osteopathic Medicine, Midwestern University, Glendale, AZ, United States
| | - A L Revill
- Arizona College of Osteopathic Medicine, Midwestern University, Glendale, AZ, United States; Department of Physiology, College of Graduate Studies, Midwestern University, Glendale, AZ, United States.
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Fogarty MJ. Loss of larger hypoglossal motor neurons in aged Fischer 344 rats. Respir Physiol Neurobiol 2023:104092. [PMID: 37331418 DOI: 10.1016/j.resp.2023.104092] [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: 05/05/2023] [Revised: 06/06/2023] [Accepted: 06/15/2023] [Indexed: 06/20/2023]
Abstract
The intrinsic (longitudinal, transversalis and verticalis) and extrinsic (genioglossus, styloglossus, hyoglossus and geniohyoid) tongue muscles are innervated by hypoglossal motor neurons (MNs). Tongue muscle activations occur during many behaviors: maintaining upper airway patency, chewing, swallowing, vocalization, vomiting, coughing, sneezing and grooming/sexual activities. In the tongues of the elderly, reduced oral motor function and strength contribute to increased risk of obstructive sleep apnoea. Tongue muscle atrophy and weakness is also described in rats, yet hypoglossal MN numbers are unknown. In young (6-months, n=10) and old (24-months, n=8) female and male Fischer 344 (F344) rats, stereological assessment of hypoglossal MN numbers and surface areas were performed on 16µm Nissl-stained brainstem cryosections. We observed a robust loss of ~15% of hypoglossal MNs and a modest ~8% reduction in their surface areas with age. In the larger size tertile of hypoglossal MNs, age-associated loss of hypoglossal MNs approached ~30% These findings uncover a potential neurogenic locus of pathology for age-associated tongue dysfunctions.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN 55905.
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Doyle BM, Singer ML, Fleury-Curado T, Rana S, Benevides ES, Byrne BJ, Polotsky VY, Fuller DD. Gene delivery to the hypoglossal motor system: preclinical studies and translational potential. Gene Ther 2021; 28:402-412. [PMID: 33574581 PMCID: PMC8355248 DOI: 10.1038/s41434-021-00225-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 12/16/2020] [Accepted: 01/15/2021] [Indexed: 12/15/2022]
Abstract
Dysfunction and/or reduced activity in the tongue muscles contributes to conditions such as dysphagia, dysarthria, and sleep disordered breathing. Current treatments are often inadequate, and the tongue is a readily accessible target for therapeutic gene delivery. In this regard, gene therapy specifically targeting the tongue motor system offers two general strategies for treating lingual disorders. First, correcting tongue myofiber and/or hypoglossal (XII) motoneuron pathology in genetic neuromuscular disorders may be readily achieved by intralingual delivery of viral vectors. The retrograde movement of viral vectors such as adeno-associated virus (AAV) enables targeted distribution to XII motoneurons via intralingual viral delivery. Second, conditions with impaired or reduced tongue muscle activation can potentially be treated using viral-driven chemo- or optogenetic approaches to activate or inhibit XII motoneurons and/or tongue myofibers. Further considerations that are highly relevant to lingual gene therapy include (1) the diversity of the motoneurons which control the tongue, (2) the patterns of XII nerve branching, and (3) the complexity of tongue muscle anatomy and biomechanics. Preclinical studies show considerable promise for lingual directed gene therapy in neuromuscular disease, but the potential of such approaches is largely untapped.
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Affiliation(s)
- Brendan M Doyle
- Department of Physical Therapy, University of Florida, Gainesville, FL, USA
- McKnight Brain Institute, University of Florida, Gainesville, FL, USA
- Rehabilitation Science PhD Program, University of Florida, Gainesville, FL, USA
- Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL, USA
| | - Michele L Singer
- Department of Physical Therapy, University of Florida, Gainesville, FL, USA
- McKnight Brain Institute, University of Florida, Gainesville, FL, USA
- Rehabilitation Science PhD Program, University of Florida, Gainesville, FL, USA
- Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL, USA
| | - Thomaz Fleury-Curado
- Department of Pediatrics and Powell Gene Therapy Center, University of Florida, Gainesville, FL, USA
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Sabhya Rana
- Department of Physical Therapy, University of Florida, Gainesville, FL, USA
- McKnight Brain Institute, University of Florida, Gainesville, FL, USA
- Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL, USA
| | - Ethan S Benevides
- Department of Physical Therapy, University of Florida, Gainesville, FL, USA
- McKnight Brain Institute, University of Florida, Gainesville, FL, USA
- Rehabilitation Science PhD Program, University of Florida, Gainesville, FL, USA
- Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL, USA
| | - Barry J Byrne
- Department of Pediatrics and Powell Gene Therapy Center, University of Florida, Gainesville, FL, USA
| | - Vsevolod Y Polotsky
- Department of Pediatrics and Powell Gene Therapy Center, University of Florida, Gainesville, FL, USA
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - David D Fuller
- Department of Physical Therapy, University of Florida, Gainesville, FL, USA.
- McKnight Brain Institute, University of Florida, Gainesville, FL, USA.
- Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL, USA.
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Fogarty MJ, Sieck GC. Tongue muscle contractile, fatigue, and fiber type properties in rats. J Appl Physiol (1985) 2021; 131:1043-1055. [PMID: 34323593 DOI: 10.1152/japplphysiol.00329.2021] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The intrinsic and extrinsic tongue muscles manipulate the position and shape of the tongue and are activated during many oral and respiratory behaviors. In the present study, in 6-mo-old Fischer 344 rats, we examined mechanical and fatigue properties of tongue muscles in relation to their fiber type composition. In an ex vivo preparation, isometric force and fatigue was assessed by direct muscle stimulation. Tongue muscles were frozen in melting isopentane and transverse sections cut at 10 µm. In hematoxylin-eosin (H&E)-stained muscle sections, the relative fractions of muscle versus extracellular matrix were determined. Muscle fibers were classified as type I, IIa and IIx, and/or IIb based on immunoreactivity to specific myosin heavy chain isoform antibodies. Cross-sectional areas (CSAs) and proportions of different fiber types were used to calculate their relative contribution to total muscle CSAs. We found that the superior and inferior longitudinal intrinsic muscles (4.4 N/cm2) and genioglossus muscle (3.0 N/cm2) generated the greatest maximum isometric force compared with the transversalis muscle (0.9 N/cm2). The longitudinal muscles and the transversalis muscle displayed greater fatigue during repetitive stimulation consistent with the greater relative contribution of type IIx and/or IIb fibers. By contrast, the genioglossus, comprising a higher proportion of type I and IIa fibers, was more fatigue resistant. This study advances our understanding of the force, fatigue, and fiber type-specific properties of individual tongue musculature. The assessments and approach provide a readily accessible muscular readout for scenarios where motor control dysfunction or tongue weakness is evident.NEW & NOTEWORTHY For the individual tongue muscles, relatively little quantification of uniaxial force, fatigue, and fiber type-specific properties has been documented. Here, we assessed uniaxial-specific force generation, fatigability, and muscle fiber type-specific properties in the superior and inferior longitudinal muscles, the transversalis, and the genioglossus in Fischer 344 rats. The longitudinal muscles produced the greatest isometric tetanic-specific forces. The genioglossus was more fatigue resistant and comprised higher proportions of I and IIa fibers.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, grid.66875.3aMayo Clinic, Rochester, Minnesota
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, grid.66875.3aMayo Clinic, Rochester, Minnesota
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Cao R, Zhang MJ, Zhou YT, Liu YJ, Wang HH, Zhang QX, Shi YW, Li JC, Wong TS, Yin M. The dorsal and the ventral side of hypoglossal motor nucleus showed different response to chronic intermittent hypoxia in rats. Sleep Breath 2020; 25:325-330. [PMID: 32562172 DOI: 10.1007/s11325-020-02125-x] [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: 03/08/2020] [Revised: 06/03/2020] [Accepted: 06/05/2020] [Indexed: 11/29/2022]
Abstract
PURPOSE To study neurochemical reactions to chronic intermittent hypoxia (CIH) in the hypoglossal nucleus (HN) of rats. METHODS Adult male Sprague-Dawley rats (n = 12) were randomly divided into two groups (the CIH and the control group). The CIH rats were housed in a hypoxic chamber with the fraction of oxygen volume alternating between 21% and 5% by providing air for 60 s and then providing nitrogen for 60 s from 8:30 am to 16:30 pm each day for 35 days. The control group was housed in a cabin with normal oxygen levels. We studied the expression of c-fos protein, 5-hydroxytryptamine (5-HT) positive terminals, and its 2A receptors in hypoglossal nuclei by immunohistochemistry. RESULTS The expression of c-fos, 5-HT positive terminals, and accordingly 5-HT 2A receptors in the CIH group were significantly higher than that in the controls (p < 0.05). The ventral side of the HN showed a clearly higher expression of 5-HT and its 2A receptors than the dorsal side (p < 0.05). CONCLUSION There were 2 responses of the HN to CIH. First, CIH induced a higher expression of 5-HT positive terminals and its 2A receptors, and second, this reaction was much more evident in ventral side than in the dorsal side. We postulate that these responses may serve to be a protective and compensatory mechanism for CIH.
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Affiliation(s)
- Rui Cao
- Department of Otorhinolaryngology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, China
| | - Min-Juan Zhang
- Department of Otorhinolaryngology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, China
| | - Yun-Tao Zhou
- Experimental Teaching Demonstration Centre, School of Rehabilitation Medicine, Nanjing Medical University, Nanjing, China
| | - Ya-Jie Liu
- Department of Otorhinolaryngology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, China
| | - Huan-Huan Wang
- Department of Otorhinolaryngology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, China
| | - Qin-Xin Zhang
- Department of Otorhinolaryngology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, China
| | - Ya-Wen Shi
- Department of Otorhinolaryngology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, China
| | - Jia-Chen Li
- Department of Otorhinolaryngology, The First Affiliated Hospital of Soochow University, Suzhou, 215006, China
| | - Thian-Sze Wong
- Division of Head and Neck, the department of surgery, the faculty of medicine, The University of Hong Kong, Hong Kong, China
| | - Min Yin
- Department of Otorhinolaryngology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, China.
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