1
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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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2
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Chen YC, Chen PY, Wang YC, Wang TG, Han DS. Decreased swallowing function in the sarcopenic elderly without clinical dysphagia: a cross-sectional study. BMC Geriatr 2020; 20:419. [PMID: 33087067 PMCID: PMC7579958 DOI: 10.1186/s12877-020-01832-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2020] [Accepted: 10/13/2020] [Indexed: 11/17/2022] Open
Abstract
Background Sarcopenia and dysphagia are prevalent health issues as the elderly population continues to grow. However, whether sarcopenia, defined by either reduced handgrip strength or gait speed, would lead to pathological effects on swallowing function is still a matter of debate. Studies focusing on subclinical changes in the swallowing function in the sarcopenic elderly are lacking. This study evaluates the swallowing function in the sarcopenic elderly without dysphagia. Methods: A cross-sectional study was conducted including subjects recruited from the community. Ninety-four individuals aged 65 and older without dysphagia were divided into two groups: sarcopenia and nonsarcopenia. The swallowing assessment included tongue pressure measurement, hyoid displacement (HD), hyoid velocity (HV) measurement with submental ultrasonography, 100-ml water-swallowing test, and the 10-item Eating Assessment Tool (EAT-10). Results The average tongue pressure was 47.0 ± 13.7 and 48.6 ± 11.5 kPa in the sarcopenia and nonsarcopenia groups, respectively (p = 0.55), whereas the average HD during swallowing was 15.3 ± 4.4 and 13.0 ± 4.2 mm in the sarcopenia and nonsarcopenia groups, respectively (p < 0.05). The median of HV during swallowing was 19.5 (6.41–45.86) and 15.9 (3.7–39.7) mm/s in the sarcopenia and nonsarcopenia group (p < 0.05). The median of time needed for consuming 100 ml water was 12.43 (3.56–49.34) and 5.66 (2.07–19.13) seconds in the sarcopenia and nonsarcopenia groups, respectively (p < 0.05). The median of the EAT-10 score was 0 (0–2) and 0 (0–1) in the sarcopenia and nonsarcopenia groups, respectively (p < 0.05). Conclusions In elderly individuals, swallowing function was significantly impaired with sarcopenia before clinical symptoms become clear. However, tongue muscles exhibited resistance to sarcopenia. We observed compensative strategies in patients with sarcopenia, such as reduced swallowing speed and increased hyoid bone movement.
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Affiliation(s)
- Yen-Chih Chen
- Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, No.1, Changde Street, Zhongzheng District, Taipei City, 10048, Taiwan, Republic of China
| | - Pei-Yun Chen
- Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, No.1, Changde Street, Zhongzheng District, Taipei City, 10048, Taiwan, Republic of China
| | - Yu-Chen Wang
- Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, No.1, Changde Street, Zhongzheng District, Taipei City, 10048, Taiwan, Republic of China
| | - Tyng-Guey Wang
- Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, No.1, Changde Street, Zhongzheng District, Taipei City, 10048, Taiwan, Republic of China.
| | - Der-Sheng Han
- Physical Medicine & Rehabilitation, National Taiwan University Hospital, Bei-Hu Branch, No.87, Neijiang Street, Wanhua District, Taipei City, Taiwan
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3
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Multiple MuSK signaling pathways and the aging neuromuscular junction. Neurosci Lett 2020; 731:135014. [PMID: 32353380 DOI: 10.1016/j.neulet.2020.135014] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 04/23/2020] [Accepted: 04/24/2020] [Indexed: 12/16/2022]
Abstract
The neuromuscular junction (NMJ) is the vehicle for fast, reliable and robust communication between motor neuron and muscle. The unparalleled accessibility of this synapse to morphological, electrophysiological and genetic analysis has yielded an in depth understanding of many molecular components mediating its formation, maturation and stability. However, key questions surrounding the signaling pathways mediating these events and how they play out across the lifetime of the synapse remain unanswered. Such information is critical since the NMJ is necessary for normal movement and is compromised in several settings including myasthenia gravis, amyotrophic lateral sclerosis (ALS), spinal muscular atrophy (SMA), muscular dystrophy, sarcopenia and aging. Muscle specific kinase (MuSK) is a central player in most if not all contexts of NMJ formation and stability. However, elucidating the function of this receptor in this range of settings is challenging since MuSK participates in at least three signaling pathways: as a tyrosine kinase-dependent receptor for agrin-LRP4 and Wnts; and, as a kinase-independent BMP co-receptor. Here we focus on NMJ stability during aging and discuss open questions regarding the molecular mechanisms that govern active maintenance of the NMJ, with emphasis on MuSK and the potential role of its multiple signaling contexts.
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Cullins MJ, Wenninger JM, Cullen JS, Russell JA, Kleim JA, Connor NP. Tongue Force Training Induces Plasticity of the Lingual Motor Cortex in Young Adult and Aged Rats. Front Neurosci 2019; 13:1355. [PMID: 31920514 PMCID: PMC6931318 DOI: 10.3389/fnins.2019.01355] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Accepted: 12/02/2019] [Indexed: 11/24/2022] Open
Abstract
Tongue exercise programs are used clinically for dysphagia in aged individuals and have been shown to improve lingual strength. However, the neural mechanisms of age-related decline in swallowing function and its association with lingual strength are not well understood. Using an established rat model of aging and tongue exercise, we hypothesized that the motor cortex of aged rats would have a smaller lingual motor map area than young adult rats and would increase in size as a function of tongue exercise. Over 8 weeks, rats either underwent a progressive resistance tongue exercise program (TE), learned the task but did not exercise (trained controls, TC), or were naïve untrained controls (UC). Cortical motor map areas for tongue and jaw were determined using intracortical microstimulation (ICMS). Rats in the TE and TC groups had a significantly larger motor cortex region for the tongue than the UC group. Lingual cortical motor area was not correlated with protrusive tongue force gains and did not differ significantly with age. These results suggest that learning a novel tongue force skill was sufficient to induce plasticity of the lingual motor cortex yet increasing tongue strength with progressive resistance exercise did not significantly expand the lingual motor area beyond the gains that occurred through the skilled learning component.
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Affiliation(s)
- Miranda J. Cullins
- Department of Surgery, University of Wisconsin-Madison, Madison, WI, United States
- *Correspondence: Miranda J. Cullins,
| | - Julie M. Wenninger
- Department of Surgery, University of Wisconsin-Madison, Madison, WI, United States
| | - Jared S. Cullen
- Department of Surgery, University of Wisconsin-Madison, Madison, WI, United States
| | - John A. Russell
- Department of Surgery, University of Wisconsin-Madison, Madison, WI, United States
| | - Jeffrey A. Kleim
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ, United States
| | - Nadine P. Connor
- Department of Surgery, University of Wisconsin-Madison, Madison, WI, United States
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Sokoloff AJ, Douglas M, Rahnert JA, Burkholder T, Easley KA, Luo Q. Absence of morphological and molecular correlates of sarcopenia in the macaque tongue muscle styloglossus. Exp Gerontol 2016; 84:40-48. [PMID: 27566374 DOI: 10.1016/j.exger.2016.08.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Revised: 08/18/2016] [Accepted: 08/22/2016] [Indexed: 01/06/2023]
Abstract
INTRODUCTION Equivocal decline of tongue muscle performance with age is compatible with resistance of the tongue to sarcopenia, the loss of muscle volume and function that typically occurs with aging. To test this possibility we characterized anatomical and molecular indices of sarcopenia in the macaque tongue muscle styloglossus (SG). METHODS We quantified myosin heavy chain (MHC), muscle fiber MHC phenotype and size and total and phosphorylated growth- and atrophy-related proteins by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), immunoblot and immunohistochemistry (IHC) in the SG in twenty-four macaque monkeys (Macaca rhesus, age range 9months to 31years) categorized into Young (<8years of age), Middle-aged (15-21years of age) and Old (>22years of age) groups. RESULTS In Young, Middle and Old age groups, by SDS-PAGE MHCI comprised ~1/3 and MHCII ~2/3 of total MHC. MHCI relative frequency was lower and MHCII higher in Middle versus Young (p=0.0099) and Middle versus Old (p=0.052). Relative frequencies of MHC fiber phenotype were not different by age but were different by phenotype (rates 233, 641 and 111 per 1000 fibers for MHCI, MHCII and MHCI-II respectively, p=0.03). Few or no fibers were positive for developmental MHC. Mean cross-sectional area (CSA) was not different among the three age groups for MHCII and MHCI-II; however MHCI fibers tended to be larger in Middle versus Old and Young (mean=2257μm2,1917μm2 (p=0.05) and 1704μm2 (p=0.06), respectively). For each age group, mean CSA increased across MHC phenotype (lowest mean CSA for MHCI and highest mean CSA for MHCII). Spearman analysis demonstrated age-related increases in total p70 ribosomal protein S6 kinase (P70), phosphorylated P70421/424, phosphorylated P38 mitogen-activated protein kinase and muscle atrophy F-Box, a trend to age-related decrease in total extracellular signal-regulated kinase (ERK), and no age-related change in total protein kinase B (Akt/PKB), phosphorylated Akt, phosphorylated ERK, phosphorylated c-Jun N-terminal kinase (JNK46) and phosphorylated P70389. CONCLUSION Common anatomical and molecular indices of sarcopenia are absent in our sample of macaque SG. Relative frequencies of MHCII protein and phenotype are preserved with age. Although MAFbx expression increases with age, this is not associated with fiber atrophy, perhaps reflecting compensatory growth signaling by p70. The resistant nature of the styloglossus muscle to sarcopenia may be related to routine activation of tongue muscles in respiration and swallowing and the preservation of hypoglossal motoneuron number with age.
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Affiliation(s)
- Alan J Sokoloff
- Department of Physiology, Emory University School of Medicine, Atlanta, GA, United States.
| | - Megan Douglas
- Department of Physiology, Emory University School of Medicine, Atlanta, GA, United States
| | - Jill A Rahnert
- School of Applied Physiology, Georgia Institute of Technology, Atlanta, GA, United States
| | - Thomas Burkholder
- School of Applied Physiology, Georgia Institute of Technology, Atlanta, GA, United States
| | - Kirk A Easley
- Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, Atlanta, GA, United States
| | - Qingwei Luo
- Department of Physiology, Emory University School of Medicine, Atlanta, GA, United States
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Schaser AJ, Ciucci MR, Connor NP. Cross-activation and detraining effects of tongue exercise in aged rats. Behav Brain Res 2015; 297:285-96. [PMID: 26477376 DOI: 10.1016/j.bbr.2015.10.030] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2015] [Revised: 10/09/2015] [Accepted: 10/11/2015] [Indexed: 02/05/2023]
Abstract
Voice and swallowing deficits can occur with aging. Tongue exercise paired with a swallow may be used to treat swallowing disorders, but may also benefit vocal function due to cross-system activation effects. It is unknown how exercise-based neuroplasticity contributes to behavior and maintenance following treatment. Eighty rats were used to examine behavioral parameters and changes in neurotrophins after tongue exercise paired with a swallow. Tongue forces and ultrasonic vocalizations were recorded before and after training/detraining in young and old rats. Tissue was analyzed for neurotrophin content. Results showed tongue exercise paired with a swallow was associated with increased tongue forces at all ages. Gains diminished after detraining in old rats. Age-related changes in vocalizations, neurotrophin 4 (NT4), and brain derived neurotrophic factor (BDNF) were found. Minimal cross-system activation effects were observed. Neuroplastic benefits were demonstrated with exercise in old rats through behavioral improvements and up-regulation of BDNF in the hypoglossal nucleus. Tongue exercise paired with a swallow should be developed, studied, and optimized in human clinical research to treat swallowing and voice disorders in elderly people.
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Affiliation(s)
- Allison J Schaser
- Department of Communication Sciences and Disorders, Department of Surgery Division of Otolaryngology-Head and Neck Surgery, University of Wisconsin-Madison, 53706, United States.
| | - Michelle R Ciucci
- Department of Communication Sciences and Disorders, Department of Surgery Division of Otolaryngology-Head and Neck Surgery, University of Wisconsin-Madison, 53706, United States
| | - Nadine P Connor
- Department of Communication Sciences and Disorders, Department of Surgery Division of Otolaryngology-Head and Neck Surgery, University of Wisconsin-Madison, 53706, United States
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Russell JA, Ciucci MR, Hammer MJ, Connor NP. Videofluorographic assessment of deglutitive behaviors in a rat model of aging and Parkinson disease. Dysphagia 2013; 28:95-104. [PMID: 22763806 PMCID: PMC3554861 DOI: 10.1007/s00455-012-9417-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Accepted: 06/07/2012] [Indexed: 10/28/2022]
Abstract
Dysphagia is commonly associated with aging and Parkinson disease and can have a significant impact on a person's quality of life. In some cases, dysphagia may be life-threatening. Animal models may be used to study underlying mechanisms of dysphagia, but paradigms that allow adequate imaging of the swallow in combination with measurement of physiological variables have not been forthcoming. To begin development of methods that allow this, we used videofluorography to record the deglutition behaviors of 22 Fisher 344/Brown Norway rats in young adult (9 months old), old (32 months old), and parkinsonian (unilateral lesion to the medial forebrain bundle) groups. We hypothesized that the old and parkinsonian rats would manifest deficits in deglutition behaviors analogous to those found in human clinical populations. Our results supported our hypothesis in that the old group demonstrated reductions in bolus transport speeds and mastication rate while the parkinsonian rats showed impairments in oral processing. Interpretation of these results should consider the particular animal model, lesion type, and videofluorographic protocol used in this work. Future studies will link swallow imaging data of this kind with physiological and anatomical data in a manner not possible with human participants.
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Affiliation(s)
- John A Russell
- Otolaryngology Head and Neck Surgery, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA.
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8
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Nishimune H, Numata T, Chen J, Aoki Y, Wang Y, Starr MP, Mori Y, Stanford JA. Active zone protein Bassoon co-localizes with presynaptic calcium channel, modifies channel function, and recovers from aging related loss by exercise. PLoS One 2012; 7:e38029. [PMID: 22701595 PMCID: PMC3368936 DOI: 10.1371/journal.pone.0038029] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2012] [Accepted: 05/02/2012] [Indexed: 12/03/2022] Open
Abstract
The P/Q-type voltage-dependent calcium channels (VDCCs) are essential for synaptic transmission at adult mammalian neuromuscular junctions (NMJs); however, the subsynaptic location of VDCCs relative to active zones in rodent NMJs, and the functional modification of VDCCs by the interaction with active zone protein Bassoon remain unknown. Here, we show that P/Q-type VDCCs distribute in a punctate pattern within the NMJ presynaptic terminals and align in three dimensions with Bassoon. This distribution pattern of P/Q-type VDCCs and Bassoon in NMJs is consistent with our previous study demonstrating the binding of VDCCs and Bassoon. In addition, we now show that the interaction between P/Q-type VDCCs and Bassoon significantly suppressed the inactivation property of P/Q-type VDCCs, suggesting that the Ca2+ influx may be augmented by Bassoon for efficient synaptic transmission at NMJs. However, presynaptic Bassoon level was significantly attenuated in aged rat NMJs, which suggests an attenuation of VDCC function due to a lack of this interaction between VDCC and Bassoon. Importantly, the decreased Bassoon level in aged NMJs was ameliorated by isometric strength training of muscles for two months. The training increased Bassoon immunoreactivity in NMJs without affecting synapse size. These results demonstrated that the P/Q-type VDCCs preferentially accumulate at NMJ active zones and play essential role in synaptic transmission in conjunction with the active zone protein Bassoon. This molecular mechanism becomes impaired by aging, which suggests altered synaptic function in aged NMJs. However, Bassoon level in aged NMJs can be improved by muscle exercise.
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MESH Headings
- Aging/metabolism
- Aging/physiology
- Animals
- Calcium/metabolism
- Calcium Channels, N-Type
- Calcium Channels, P-Type/genetics
- Calcium Channels, P-Type/metabolism
- Calcium Channels, Q-Type/genetics
- Calcium Channels, Q-Type/metabolism
- Cell Line
- Cricetinae
- Gene Expression Regulation/physiology
- Image Processing, Computer-Assisted
- Immunohistochemistry
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Microscopy, Confocal
- Nerve Tissue Proteins/metabolism
- Neuromuscular Junction/physiology
- Patch-Clamp Techniques
- Physical Conditioning, Animal/physiology
- Presynaptic Terminals/metabolism
- Rats
- Rats, Sprague-Dawley
- Synaptic Transmission/physiology
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Affiliation(s)
- Hiroshi Nishimune
- Department of Anatomy and Cell Biology, University of Kansas Medical School, Kansas City, Kansas, United States of America
- * E-mail: (HN); (YM); (JAS)
| | - Tomohiro Numata
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Kyoto, Japan
| | - Jie Chen
- Department of Anatomy and Cell Biology, University of Kansas Medical School, Kansas City, Kansas, United States of America
| | - Yudai Aoki
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Kyoto, Japan
| | - Yonghong Wang
- Department of Molecular & Integrative Physiology, University of Kansas Medical School, Kansas City, Kansas, United States of America
| | - Miranda P. Starr
- Department of Molecular & Integrative Physiology, University of Kansas Medical School, Kansas City, Kansas, United States of America
| | - Yasuo Mori
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Kyoto, Japan
- * E-mail: (HN); (YM); (JAS)
| | - John A. Stanford
- Department of Molecular & Integrative Physiology, University of Kansas Medical School, Kansas City, Kansas, United States of America
- * E-mail: (HN); (YM); (JAS)
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9
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Behan M, Moeser AE, Thomas CF, Russell JA, Wang H, Leverson GE, Connor NP. The effect of tongue exercise on serotonergic input to the hypoglossal nucleus in young and old rats. JOURNAL OF SPEECH, LANGUAGE, AND HEARING RESEARCH : JSLHR 2012; 55:919-29. [PMID: 22232395 PMCID: PMC3326185 DOI: 10.1044/1092-4388(2011/11-0091)] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
PURPOSE Breathing and swallowing problems affect elderly people and may be related to age-associated tongue dysfunction. Hypoglossal motoneurons that innervate the tongue receive a robust, excitatory serotonergic (5HT) input and may be affected by aging. We used a rat model of aging and progressive resistance tongue exercise to determine whether age-related alterations in 5HT inputs to the hypoglossal nucleus can be modified. We hypothesized that tongue forces would increase with exercise, 5HT input to the tongue would decrease with age, and tongue exercise would augment 5HT input to the hypoglossal nucleus. METHOD Young (9-10 months), middle-aged (24-25 months), and old (32-33 months) male F344/BN rats received tongue exercise for 8 weeks. Immunoreactivity for 5HT was measured in digital images of sections through the hypoglossal nucleus using ImageJ software. RESULTS Tongue exercise resulted in increased maximum tongue forces at all ages. There was a statistically significant increase in 5HT immunoreactivity in the hypoglossal nucleus in exercised, young rats but only in the caudal third of the nucleus and primarily in the ventral half. CONCLUSION Specificity found in serotonergic input following exercise may reflect the topographic organization of motoneurons in the hypoglossal nucleus and the tongue muscles engaged in the exercise paradigm.
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10
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Basken JN, Connor NP, Ciucci MR. Effect of aging on ultrasonic vocalizations and laryngeal sensorimotor neurons in rats. Exp Brain Res 2012; 219:351-61. [PMID: 22562586 DOI: 10.1007/s00221-012-3096-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Accepted: 04/12/2012] [Indexed: 12/21/2022]
Abstract
While decline in vocal quality is prevalent in an aging population, the underlying neurobiological mechanisms contributing to age-related dysphonia are unknown and difficult to study in humans. Development of an animal model appears critical for investigating this issue. Using an established aging rat model, we evaluated if 50-kHz ultrasonic vocalizations in 10, 32-month-old (old) Fischer 344/Brown Norway rats differed from those in 10, 9-month-old (young adult) rats. The retrograde tracer, Cholera Toxin β, was injected to the thyroarytenoid muscle to determine if motoneuron loss in the nucleus ambiguus was associated with age. Results indicated that older rats had vocalizations with diminished acoustic complexity as demonstrated by reduced bandwidth, intensity, and peak frequency, and these changes were dependent on the type of 50-kHz vocalization. Simple calls of old rats had reduced bandwidth, peak frequency, and intensity while frequency-modulated calls of old rats had reduced bandwidth and intensity. Surprisingly, one call type, step calls, had increased duration in the aged rats. These findings reflect phonatory changes observed in older humans. We also found significant motoneuron loss in the nucleus ambiguus of aged rats, which suggests that motoneuron loss may be a contributing factor to decreased complexity and quality of ultrasonic vocalizations. These findings suggest that a rat ultrasonic phonation model may be useful for studying age-related changes in vocalization observed in humans.
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Affiliation(s)
- Jaime N Basken
- Department of Communicative Disorders, University of Wisconsin-Madison, Madison, WI 53706, USA.
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11
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Johnson AM, Connor NP. Effects of electrical stimulation on neuromuscular junction morphology in the aging rat tongue. Muscle Nerve 2011; 43:203-11. [PMID: 21254085 DOI: 10.1002/mus.21819] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Alterations in neuromuscular junction (NMJ) structure in cranial muscles may contribute to age-related deficits in critical sensorimotor actions such as swallowing. Neuromuscular electrical stimulation (NMES) is used in swallowing therapy, but it is unclear how NMJ structure is affected or if NMJ morphology is best measured in two or three dimensions. Two- and three-dimensional measurements of NMJ morphology in the genioglossus muscle were compared in rats that had undergone 8 weeks of hypoglossal nerve stimulation vs. untreated controls. The relationship between motor endplate volume and nerve terminal volume had a mean positive slope in 90% of the young adult controls, but it was positive in only 50% of the old controls; 89% of NMES old rats had a positive slope. NMJ measurements were more accurate when measured in three dimensions. In the NMJ, aging and NMES are associated with changes in the pre- and post-synaptic relationship.
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Affiliation(s)
- Aaron M Johnson
- Department of Surgery, University of Wisconsin-Madison, Madison, WI 53792, USA
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12
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Augustin H, Partridge L. Invertebrate models of age-related muscle degeneration. Biochim Biophys Acta Gen Subj 2009; 1790:1084-94. [PMID: 19563864 DOI: 10.1016/j.bbagen.2009.06.011] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2009] [Revised: 06/12/2009] [Accepted: 06/20/2009] [Indexed: 12/26/2022]
Abstract
Functional and structural deterioration of muscles is an inevitable consequence of ageing in a wide variety of animal species. What underlies these changes is a complex network of interactions between the muscle-intrinsic and muscle-extrinsic factors, making it very difficult to distinguish between the cause and the consequence. Many of the genes, structures, and processes implicated in mammalian skeletal muscle ageing are preserved in invertebrate species Drosophila melanogaster and Caenorhabditis elegans. The absence in these organisms of mechanisms that promote muscle regeneration, and substantially different hormonal environment, warrant caution when extrapolating experimental data from studies conducted in invertebrates to mammalian species. The simplicity and accessibility of these models, however, offer ample opportunities for studying age-related myopathologies as well as investigating drugs and therapies to alleviate them.
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Affiliation(s)
- Hrvoje Augustin
- Institute of Healthy Ageing and GEE, University College London, London WC1E 6BT, UK
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13
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Schwarz EC, Thompson JM, Connor NP, Behan M. The effects of aging on hypoglossal motoneurons in rats. Dysphagia 2008; 24:40-8. [PMID: 18716837 DOI: 10.1007/s00455-008-9169-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2007] [Accepted: 04/24/2008] [Indexed: 11/28/2022]
Abstract
Aging can result in a loss of neuronal cell bodies and a decrease in neuronal size in some regions of the brain and spinal cord. Motoneuron loss in the spinal cord is thought to contribute to the progressive decline in muscle mass and strength that occurs with age (sarcopenia). Swallowing disorders represent a large clinical problem in elderly persons; however, age-related alterations in cranial motoneurons that innervate muscles involved in swallowing have been understudied. We aimed to determine if age-related alterations occurred in the hypoglossal nucleus in the brainstem. If present, these changes might help explain alterations at the neuromuscular junction and changes in the contractile properties of tongue muscle that have been reported in older rats. We hypothesized that with increasing age there would be a loss of motoneurons and a reduction in neuronal size and the number of primary dendrites associated with each hypoglossal motoneuron. Neurons in the hypoglossal nucleus were visualized with the neuronal marker NeuN in young (9-10 months), middle-aged (24-25 months), and old (32-33 months) male F344/BN rats. Hypoglossal motoneurons were retrograde-labeled with injections of Cholera Toxin beta into the genioglossus muscle of the tongue and visualized using immunocytochemistry. Results indicated that the number of primary dendrites of hypoglossal motoneurons decreased significantly with age, while no age-associated changes were found in the number or size of hypoglossal motoneurons. Loss of primary dendrites could reduce the number of synaptic inputs and thereby impair function.
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Affiliation(s)
- Emilie C Schwarz
- Department of Comparative Biosciences, University of Wisconsin-Madison, Madison, WI 53706, USA
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Connor NP, Ota F, Nagai H, Russell JA, Leverson G. Differences in age-related alterations in muscle contraction properties in rat tongue and hindlimb. JOURNAL OF SPEECH, LANGUAGE, AND HEARING RESEARCH : JSLHR 2008; 51:818-827. [PMID: 18658053 PMCID: PMC2892886 DOI: 10.1044/1092-4388(2008/059)] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
PURPOSE Because of differences in muscle architecture and biomechanics, the purpose of this study was to determine whether muscle contractile properties of rat hindlimb and tongue were differentially affected by aging. METHOD Deep peroneal and hypoglossal nerves were stimulated in 6 young and 7 old Fischer 344-Brown Norway rats to allow recording of muscle contractile properties of tongue and extensor digitorum longus (EDL) muscle in the hindlimb. In the same animals, the following measurements were made: (a) twitch contraction time (CT; in milliseconds), (b) half decay time (HDT; in milliseconds), (c) maximum twitch force (in grams), (d) tetanic force, and (e) fatigue index determined from repetitive stimulation of the muscles. RESULTS No significant differences were observed in young versus old groups in retrusive tongue forces, whereas a significant (p < .05) decrement in EDL tetanic forces was found in old rats. Slower CT in old rats was observed only in the tongue. Old and young groups were not significantly different in fatigue index or HDT for tongue or EDL. CONCLUSIONS Old animals generated equivalent maximum tongue forces with stimulation, but they were slower in achieving these forces than young animals. Limb and cranial muscles were not affected equally by aging. As such, information derived from limb muscle studies may not easily generalize to the cranial motor system.
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Affiliation(s)
- Nadine P Connor
- University of Wisconsin Clinical Science Center, Madison, WI 53792-7375, USA.
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Zhang H, Bethel CS, Smittkamp SE, Stanford JA. Age-related changes in orolingual motor function in F344 vs F344/BN rats. Physiol Behav 2007; 93:461-6. [PMID: 17980393 DOI: 10.1016/j.physbeh.2007.10.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2007] [Revised: 08/30/2007] [Accepted: 10/05/2007] [Indexed: 10/22/2022]
Abstract
Normal aging is associated with both locomotor and orolingual motor deficits. Preclinical studies of motor function in normal aging, however, have focused primarily on locomotor activity. The purpose of this study was to measure age-related changes in orolingual motor function and compare these changes between two rat strains commonly used in aging studies: Fischer 344 (F344) and Fischer 344/Brown Norway hybrid (F344/BN) rats. Rats (6-, 12-, 18- and 24-months of age) were trained to lick water from an isometric force-sensing operandum so that the number of licks per session, licking rhythm (licks/second) and lick force could be measured. In both strains, the number of licks per session was greatest in the oldest group, while this measure was greater for F344/BN rats at all ages. Peak tongue force increased with age in F344/BN rats, did not change with age in the F344 rats, and was greater for the F344/BN rats at all ages. Both strains exhibited an age-related slowing of licking rhythm beginning with the 18-month-old group. These findings suggest that despite lifespan differences between these two rat strains, diminished tongue motility emerges at the same age.
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Affiliation(s)
- Hongyu Zhang
- Department of Molecular & Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, USA
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Tiago RSL, Faria FPD, Pontes PADL, Brasil ODOCD. Morphometric aspects of the human hypoglossal nerve in adults and the elderly. Braz J Otorhinolaryngol 2006; 71:554-8. [PMID: 16612513 DOI: 10.1016/s1808-8694(15)31256-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
AIM Perform a morphometric analysis of the myelinic fibers of the right hypoglossal nerve, in two age groups; to verify quantitative changes as a result of the aging process. STUDY DESIGN Anatomic. MATERIAL AND METHOD A 1 cm fragment of the right hypoglossal nerve was collected from 12 male corpses without any medical history of diseases such as: diabetes, alcoholism, and malignant neoplasia. The sample was divided in two groups: group with six corpses under sixty years old (adult), and another group with six corpses sixty years old or above (elderly). The material was fixed at 2.5% glutaldehyde and 2% paraformaldehyde solution; post-fixed at 2% osmium tetroxide; dehydrated with increasing ethanol concentrations, and included in epoxy resin. Semi-thin sections of 0.3 microm were obtaining, colored in 1% toluidine blue, and evaluated with light microscope combined with image analyzing system. The following morphometric data were quantified: intraperineural transversal section area, number, and diameter of the myelinic fibers. RESULTS The intraperineural area of the hypoglossal nerve was similar in both age groups (p=0.8691). The average area in the adult group was 1.697 mm2 and in the elderly group it was 1.649 mm2. The total number of myelinic fibers of the hypoglossal nerve was similar in both age groups (p=0.9018). The adult group presented an average of 10,286 +/- 2,308 myelinic fibers, and the elderly group presented an average of 10,141 +/- 1,590 myelinic fibers. A bimodal distribution of the myelinic fibers was observed, with a significant peak on the 9 microm fibers, and another smaller peak on the 2 microm fibers. CONCLUSION The intraperineural area and the total number of myelinic fibers of the right hypoglossal nerve are similar in both age groups.
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Affiliation(s)
- Romualdo Suzano Louzeiro Tiago
- Department of Otorhinolaryngology and Head and Neck Surgery, Federal University of Sao Paulo, Escola Paulista de Medicina.
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Ota F, Connor NP, Konopacki R. Alterations in contractile properties of tongue muscles in old rats. Ann Otol Rhinol Laryngol 2005; 114:799-803. [PMID: 16285271 DOI: 10.1177/000348940511401010] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
OBJECTIVES Fatigue and weakness are well-known signs of aging that are related to sarcopenia, or loss of skeletal muscle mass, organization, and strength. Sarcopenia may affect swallowing. The tongue plays a vital role in swallowing, but there is limited knowledge regarding age-related changes in lingual muscle contractile properties. Our purpose was to determine whether alterations in tongue force, temporal features of tongue muscle contraction, and fatigability are manifested as a function of aging in old rats. METHODS We evaluated tongue muscle contractile properties in young and old Fischer 344/Brown Norway rats. Contractions were elicited via bilateral electrical stimulation of the hypoglossal nerves. RESULTS Maximum tongue forces and fatigability were not significantly altered in old animals, but aging was associated with significantly longer twitch contraction time and longer half-decay recovery time intervals (p < .01). CONCLUSIONS The results indicated that old animals generated sufficient maximum tongue forces, but were slower in achieving these forces than young animals. These findings are consistent with reports of altered temporal parameters of tongue actions during swallowing in humans, and suggest that a disruption in the timing of muscle contraction onset and recovery may contribute to the altered tongue kinetics observed with aging.
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Affiliation(s)
- Fumikazu Ota
- Department of Surgery, Division of Otolaryngology-Head and Neck Surgery, University of Wisconsin, Madison, Wisconsin, USA
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