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Mantilla CB, Ermilov LG, Greising SM, Gransee HM, Zhan WZ, Sieck GC. Electrophysiological effects of BDNF and TrkB signaling at type-identified diaphragm neuromuscular junctions. J Neurophysiol 2023; 129:781-792. [PMID: 36883761 PMCID: PMC10069962 DOI: 10.1152/jn.00015.2023] [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: 01/13/2023] [Revised: 02/27/2023] [Accepted: 03/01/2023] [Indexed: 03/09/2023] Open
Abstract
Previous studies show that synaptic quantal release decreases during repetitive stimulation, i.e., synaptic depression. Neurotrophin brain-derived neurotrophic factor (BDNF) enhances neuromuscular transmission via activation of tropomyosin-related kinase receptor B (TrkB). We hypothesized that BDNF mitigates synaptic depression at the neuromuscular junction and that the effect is more pronounced at type IIx and/or IIb fibers compared to type I or IIa fibers given the more rapid reduction in docked synaptic vesicles with repetitive stimulation. Rat phrenic nerve-diaphragm muscle preparations were used to determine the effect of BDNF on synaptic quantal release during repetitive stimulation at 50 Hz. An ∼40% decline in quantal release was observed during each 330-ms duration train of nerve stimulation (intratrain synaptic depression), and this intratrain decline was observed across repetitive trains (20 trains at 1/s repeated every 5 min for 30 min for 6 sets). BDNF treatment significantly enhanced quantal release at all fiber types (P < 0.001). BDNF treatment did not change release probability within a stimulation set but enhanced synaptic vesicle replenishment between sets. In agreement, synaptic vesicle cycling (measured using FM4-64 fluorescence uptake) was increased following BDNF [or neurotrophin-4 (NT-4)] treatment (∼40%; P < 0.05). Conversely, inhibiting BDNF/TrkB signaling with the tyrosine kinase inhibitor K252a and TrkB-IgG (which quenches endogenous BDNF or NT-4) decreased FM4-64 uptake (∼34% across fiber types; P < 0.05). The effects of BDNF were generally similar across all fiber types. We conclude that BDNF/TrkB signaling acutely enhances presynaptic quantal release and thereby may serve to mitigate synaptic depression and maintain neuromuscular transmission during repetitive activation.NEW & NOTEWORTHY Neurotrophin brain-derived neurotrophic factor (BDNF) enhances neuromuscular transmission via activation of tropomyosin-related kinase receptor B (TrkB). Rat phrenic nerve-diaphragm muscle preparations were used to determine the rapid effect of BDNF on synaptic quantal release during repetitive stimulation. BDNF treatment significantly enhanced quantal release at all fiber types. BDNF increased synaptic vesicle cycling (measured using FM4-64 fluorescence uptake); conversely, inhibiting BDNF/TrkB signaling decreased FM4-64 uptake.
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Affiliation(s)
- Carlos B Mantilla
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, United States
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
| | - Leonid G Ermilov
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
| | - Sarah M Greising
- School of Kinesiology, University of Minnesota, Minneapolis, Minnesota, United States
| | - Heather M Gransee
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, United States
| | - Wen-Zhi Zhan
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
| | - Gary C Sieck
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, United States
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
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Pareja-Cajiao M, Gransee HM, Sieck GC, Mantilla CB. TrkB signaling contributes to transdiaphragmatic pressure generation in aged mice. J Neurophysiol 2021; 125:1157-1163. [PMID: 33596726 PMCID: PMC8282218 DOI: 10.1152/jn.00004.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 02/12/2021] [Accepted: 02/13/2021] [Indexed: 12/19/2022] Open
Abstract
Ventilatory deficits are common in old age and may result from neuromuscular dysfunction. Signaling via the tropomyosin-related kinase receptor B (TrkB) regulates neuromuscular transmission and, in young mice, is important for the generation of transdiaphragmatic pressure (Pdi). Loss of TrkB signaling worsened neuromuscular transmission failure and reduced maximal Pdi, and these effects are similar to those observed in old age. Administration of TrkB agonists such as 7,8-dihydroxyflavone (7,8-DHF) improves neuromuscular transmission in young and old mice (18 mo; 75% survival). We hypothesized that TrkB signaling contributes to Pdi generation in old mice, particularly during maximal force behaviors. Old male and female TrkBF616A mice, with a mutation that induces 1NMPP1-mediated TrkB kinase inhibition, were randomly assigned to systemic treatment with vehicle, 7,8-DHF, or 1NMPP1 1 h before experiments. Pdi was measured during eupneic breathing (room air), hypoxia-hypercapnia (10% O2/5% CO2), tracheal occlusion, spontaneous deep breaths ("sighs"), and bilateral phrenic nerve stimulation (Pdimax). There were no differences in the Pdi amplitude across treatments during ventilatory behaviors (eupnea, hypoxia-hypercapnia, occlusion, or sigh). As expected, Pdi increased from eupnea and hypoxia-hypercapnia (∼7 cm H2O) to occlusion and sighs (∼25 cm H2O), with no differences across treatments. Pdimax was ∼50 cm H2O in the vehicle and 7,8-DHF groups and ∼40 cm H2O in the 1NMPP1 group (F8,74 = 2; P = 0.02). Our results indicate that TrkB signaling is necessary for generating maximal forces by the diaphragm muscle in old mice and are consistent with aging effects of TrkB signaling on neuromuscular transmission.NEW & NOTEWORTHY TrkB signaling is necessary for generating maximal forces by the diaphragm muscle. In 19- to 21-mo-old TrkBF616A mice susceptible to 1NMPP1-induced inhibition of TrkB kinase activity, maximal Pdi generated by bilateral phrenic nerve stimulation was ∼20% lower after 1NMPP1 compared with vehicle-treated mice. Treatment with the TrkB agonist 7,8-dihydroxyflavone did not affect Pdi generation when compared with age-matched mice. Inhibition of TrkB kinase activity did not affect the forces generated during lower force behaviors in old age.
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Affiliation(s)
- Miguel Pareja-Cajiao
- Departments of Anesthesiology and Perioperative Medicine, Mayo Clinic, College of Medicine and Science, Rochester, Minnesota
| | - Heather M Gransee
- Departments of Anesthesiology and Perioperative Medicine, Mayo Clinic, College of Medicine and Science, Rochester, Minnesota
| | - Gary C Sieck
- Departments of Anesthesiology and Perioperative Medicine, Mayo Clinic, College of Medicine and Science, Rochester, Minnesota
- Physiology and Biomedical Engineering, Mayo Clinic, College of Medicine and Science, Rochester, Minnesota
| | - Carlos B Mantilla
- Departments of Anesthesiology and Perioperative Medicine, Mayo Clinic, College of Medicine and Science, Rochester, Minnesota
- Physiology and Biomedical Engineering, Mayo Clinic, College of Medicine and Science, Rochester, Minnesota
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3
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Pareja-Cajiao M, Gransee HM, Cole NA, Sieck GC, Mantilla CB. Inhibition of TrkB kinase activity impairs transdiaphragmatic pressure generation. J Appl Physiol (1985) 2020; 128:338-344. [PMID: 31944892 PMCID: PMC7052584 DOI: 10.1152/japplphysiol.00564.2019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Revised: 11/14/2019] [Accepted: 01/15/2020] [Indexed: 12/18/2022] Open
Abstract
Signaling via the tropomyosin-related kinase receptor subtype B (TrkB) regulates neuromuscular transmission, and inhibition of TrkB kinase activity by 1NMPP1 in TrkBF616A mice worsens neuromuscular transmission failure (NMTF). We hypothesized that acute inhibition of TrkB kinase activity will impair the ability of the diaphragm muscle to produce maximal transdiaphragmatic pressure (Pdi) without impacting the ability to generate forces associated with ventilation, consistent with the greater susceptibility to NMTF in motor units responsible for higher-force nonventilatory behaviors. Adult male and female TrkBF616A mice were injected with 1NMPP1 (n = 8) or vehicle (DMSO; n = 8) 1 h before Pdi measurements during eupneic breathing, hypoxia/hypercapnia (10% O2/5% CO2), tracheal occlusion, spontaneous deep breaths ("sighs") and during maximal activation elicited by bilateral phrenic nerve stimulation. In the vehicle-treated group, Pdi increased from ~10 cmH2O during eupnea and hypoxia/hypercapnia, to ~35 cmH2O during sighs and tracheal occlusion, and to ~65 cm H2O during maximal stimulation. There was no effect of acute 1NMPP1 treatment on Pdi generated during most behaviors, except during maximal stimulation (~30% reduction; P < 0.05). This reduction in maximal Pdi is generally similar to the worsening of NMTF previously reported with TrkB kinase inhibition in rodents. Accordingly, impaired TrkB signaling limits the range of motor behaviors accomplished by the diaphragm muscle and may contribute to neuromuscular dysfunction, primarily by impacting fatigable, higher force-generating motor units.NEW & NOTEWORTHY TrkB signaling plays an important role in maintaining neuromuscular function in the diaphragm muscle and may be necessary to accomplish the various motor behaviors ranging from ventilation to expulsive, behaviors requiring near-maximal forces. This study shows that inhibition of TrkB kinase activity impairs maximal pressure generation by the diaphragm muscle, but the ability to generate the lower pressures required for ventilatory behaviors is not impacted.
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Affiliation(s)
- Miguel Pareja-Cajiao
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, College of Medicine and Science, Rochester, Minnesota
| | - Heather M Gransee
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, College of Medicine and Science, Rochester, Minnesota
| | - Naomi A Cole
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, College of Medicine and Science, Rochester, Minnesota
| | - Gary C Sieck
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, College of Medicine and Science, Rochester, Minnesota
- Department of Physiology and Biomedical Engineering, Mayo Clinic, College of Medicine and Science, Rochester, Minnesota
| | - Carlos B Mantilla
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, College of Medicine and Science, Rochester, Minnesota
- Department of Physiology and Biomedical Engineering, Mayo Clinic, College of Medicine and Science, Rochester, Minnesota
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Brandenburg JE, Fogarty MJ, Sieck GC. Why individuals with cerebral palsy are at higher risk for respiratory complications from COVID-19. J Pediatr Rehabil Med 2020; 13:317-327. [PMID: 33136080 DOI: 10.3233/prm-200746] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Respiratory dysfunction is a leading cause of morbidity and mortality in individuals with cerebral palsy (CP). In children and adults with CP, movement and physical function is always affected. Yet, many clinicians overlook potential for impaired movement and function of the diaphragm muscle (DIAm) in individuals with CP. Since individuals with pre-existing respiratory disorders are at greater risk for respiratory complications if they contract COVID-19, understanding potential risks to individuals with CP is important. In this review we present research on respiratory function and DIAm force generation in children with CP. We compare this clinical work to basic science research investigating phrenic motor neuron and DIAm motor unit dysfunction in an animal model with CP symptoms, the spa mouse. Finally, we integrate the clinical and basic science work in respiratory function in CP, discussing potential for individuals with CP to have severe respiratory symptoms from COVID-19.
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Affiliation(s)
- Joline E Brandenburg
- Department of Physical Medicine and Rehabilitation, Mayo Clinic College of Medicine, Rochester, MN, USA.,Department of Pediatric and Adolescent Medicine, Mayo Clinic College of Medicine, Rochester, MN, USA
| | - Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN, USA
| | - Gary C Sieck
- Department of Physical Medicine and Rehabilitation, Mayo Clinic College of Medicine, Rochester, MN, USA.,Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN, USA
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5
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Brandenburg JE, Fogarty MJ, Sieck GC. A Critical Evaluation of Current Concepts in Cerebral Palsy. Physiology (Bethesda) 2019; 34:216-229. [PMID: 30968751 PMCID: PMC7938766 DOI: 10.1152/physiol.00054.2018] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Revised: 01/11/2019] [Accepted: 01/23/2019] [Indexed: 11/22/2022] Open
Abstract
Spastic cerebral palsy (CP), despite the name, is not consistently identifiable by specific brain lesions. CP animal models focus on risk factors for development of CP, yet few reproduce the diagnostic symptoms. Animal models of CP must advance beyond risk factors to etiologies, including both the brain and spinal cord.
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Affiliation(s)
- Joline E Brandenburg
- Department of Physical Medicine and Rehabilitation, Mayo Clinic College of Medicine , Rochester, Minnesota
- Department of Pediatric and Adolescent Medicine, Mayo Clinic College of Medicine , Rochester, Minnesota
| | - Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine , Rochester, Minnesota
| | - Gary C Sieck
- Department of Physical Medicine and Rehabilitation, Mayo Clinic College of Medicine , Rochester, Minnesota
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine , Rochester, Minnesota
- Department of Anesthesiology, Mayo Clinic College of Medicine , Rochester, Minnesota
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6
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Fogarty MJ, Sieck GC. Evolution and Functional Differentiation of the Diaphragm Muscle of Mammals. Compr Physiol 2019; 9:715-766. [PMID: 30873594 PMCID: PMC7082849 DOI: 10.1002/cphy.c180012] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Symmorphosis is a concept of economy of biological design, whereby structural properties are matched to functional demands. According to symmorphosis, biological structures are never over designed to exceed functional demands. Based on this concept, the evolution of the diaphragm muscle (DIAm) in mammals is a tale of two structures, a membrane that separates and partitions the primitive coelomic cavity into separate abdominal and thoracic cavities and a muscle that serves as a pump to generate intra-abdominal (Pab ) and intrathoracic (Pth ) pressures. The DIAm partition evolved in reptiles from folds of the pleural and peritoneal membranes that was driven by the biological advantage of separating organs in the larger coelomic cavity into separate thoracic and abdominal cavities, especially with the evolution of aspiration breathing. The DIAm pump evolved from the advantage afforded by more effective generation of both a negative Pth for ventilation of the lungs and a positive Pab for venous return of blood to the heart and expulsive behaviors such as airway clearance, defecation, micturition, and child birth. © 2019 American Physiological Society. Compr Physiol 9:715-766, 2019.
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Affiliation(s)
- Matthew J Fogarty
- Mayo Clinic, Department of Physiology & Biomedical Engineering, Rochester, Minnesota, USA
| | - Gary C Sieck
- Mayo Clinic, Department of Physiology & Biomedical Engineering, Rochester, Minnesota, USA
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7
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Mantilla CB, Zhan WZ, Gransee HM, Prakash YS, Sieck GC. Phrenic motoneuron structural plasticity across models of diaphragm muscle paralysis. J Comp Neurol 2018; 526:2973-2983. [PMID: 30411341 DOI: 10.1002/cne.24503] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 07/09/2018] [Indexed: 12/19/2022]
Abstract
Structural plasticity in motoneurons may be influenced by activation history and motoneuron-muscle fiber interactions. The goal of this study was to examine the morphological adaptations of phrenic motoneurons following imposed motoneuron inactivity while controlling for diaphragm muscle inactivity. Well-characterized rat models were used including unilateral C2 spinal hemisection (SH; ipsilateral phrenic motoneurons and diaphragm muscle are inactive) and tetrodotoxin phrenic nerve blockade (TTX; ipsilateral diaphragm muscle is paralyzed while phrenic motoneuron activity is preserved). We hypothesized that inactivity of phrenic motoneurons would result in a decrease in motoneuron size, consistent with a homeostatic increase in excitability. Phrenic motoneurons were retrogradely labeled by ipsilateral diaphragm muscle injection of fluorescent dextrans or cholera toxin subunit B. Following 2 weeks of diaphragm muscle paralysis, morphological parameters of labeled ipsilateral phrenic motoneurons were assessed quantitatively using fluorescence confocal microscopy. Compared to controls, phrenic motoneuron somal volumes and surface areas decreased with SH, but increased with TTX. Total phrenic motoneuron surface area was unchanged by SH, but increased with TTX. Dendritic surface area was estimated from primary dendrite diameter using a power equation obtained from three-dimensional reconstructed phrenic motoneurons. Estimated dendritic surface area was not significantly different between control and SH, but increased with TTX. Similarly, TTX significantly increased total phrenic motoneuron surface area. These results suggest that ipsilateral phrenic motoneuron morphological adaptations are consistent with a normalization of motoneuron excitability following prolonged alterations in motoneuron activity. Phrenic motoneuron structural plasticity is likely more dependent on motoneuron activity (or descending input) than muscle fiber activity.
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Affiliation(s)
- Carlos B Mantilla
- Department of Anesthesiology & Perioperative Medicine, Mayo Clinic, Rochester, Minnesota.,Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Wen-Zhi Zhan
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Heather M Gransee
- Department of Anesthesiology & Perioperative Medicine, Mayo Clinic, Rochester, Minnesota
| | - Y S Prakash
- Department of Anesthesiology & Perioperative Medicine, Mayo Clinic, Rochester, Minnesota.,Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Gary C Sieck
- Department of Anesthesiology & Perioperative Medicine, Mayo Clinic, Rochester, Minnesota.,Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
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8
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Brandenburg JE, Gransee HM, Fogarty MJ, Sieck GC. Differences in lumbar motor neuron pruning in an animal model of early onset spasticity. J Neurophysiol 2018; 120:601-609. [PMID: 29718808 DOI: 10.1152/jn.00186.2018] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Motor neuron (MN) development in early onset spasticity is poorly understood. For example, spastic cerebral palsy (sCP), the most common motor disability of childhood, is poorly predicted by brain imaging, yet research remains focused on the brain. By contrast, MNs, via the motor unit and neurotransmitter signaling, are the target of most therapeutic spasticity treatments and are the final common output of motor control. MN development in sCP is a critical knowledge gap, because the late embryonic and postnatal periods are not only when the supposed brain injury occurs but also are critical times for spinal cord neuromotor development. Using an animal model of early onset spasticity [ spa mouse (B6.Cg- Glrbspa/J) with a glycine (Gly) receptor mutation], we hypothesized that removal of effective glycinergic neurotransmitter inputs to MNs during development will influence MN pruning (including primary dendrites) and MN size. Spa (Glrb-/-) and wild-type (Glrb+/+) mice, ages 4-9 wk, underwent unilateral retrograde labeling of the tibialis anterior muscle MNs via peroneal nerve dip in tetramethylrhodamine. After 3 days, mice were euthanized and perfused with 4% paraformaldehyde, and the spinal cord was excised and processed for confocal imaging. Spa mice had ~61% fewer lumbar tibialis anterior MNs ( P < 0.01), disproportionately affecting larger MNs. Additionally, a ~23% reduction in tibialis anterior MN somal surface area ( P < 0.01) and a 12% increase in primary dendrites ( P = 0.046) were observed. Thus MN pruning and MN somal surface area are abnormal in early onset spasticity. Fewer and smaller MNs may contribute to the spastic phenotype. NEW & NOTEWORTHY Motor neuron (MN) development in early onset spasticity is poorly understood. In an animal model of early onset spasticity, spa mice, we found ~61% fewer lumbar tibialis anterior MNs compared with controls. This MN loss disproportionately affected larger MNs. Thus number and heterogeneity of the MN pool are decreased in spa mice, likely contributing to the spastic phenotype.
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Affiliation(s)
- Joline E Brandenburg
- Department of Physical Medicine and Rehabilitation, Mayo Clinic College of Medicine , Rochester, Minnesota.,Department of Pediatric and Adolescent Medicine, Mayo Clinic College of Medicine , Rochester, Minnesota
| | - Heather M Gransee
- Department of Anesthesiology, Mayo Clinic College of Medicine , Rochester, Minnesota
| | - Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine , Rochester, Minnesota.,School of Biomedical Sciences, The University of Queensland , Brisbane , Australia
| | - Gary C Sieck
- Department of Physical Medicine and Rehabilitation, Mayo Clinic College of Medicine , Rochester, Minnesota.,Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine , Rochester, Minnesota.,Department of Anesthesiology, Mayo Clinic College of Medicine , Rochester, Minnesota
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9
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Gill LC, Gransee HM, Sieck GC, Mantilla CB. Functional recovery after cervical spinal cord injury: Role of neurotrophin and glutamatergic signaling in phrenic motoneurons. Respir Physiol Neurobiol 2015; 226:128-36. [PMID: 26506253 DOI: 10.1016/j.resp.2015.10.009] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Revised: 10/15/2015] [Accepted: 10/17/2015] [Indexed: 11/19/2022]
Abstract
Cervical spinal cord injury (SCI) interrupts descending neural drive to phrenic motoneurons causing diaphragm muscle (DIAm) paralysis. Recent studies using a well-established model of SCI, unilateral spinal hemisection of the C2 segment of the cervical spinal cord (SH), provide novel information regarding the molecular and cellular mechanisms of functional recovery after SCI. Over time post-SH, gradual recovery of rhythmic ipsilateral DIAm activity occurs. Recovery of ipsilateral DIAm electromyogram (EMG) activity following SH is enhanced by increasing brain-derived neurotrophic factor (BDNF) in the region of the phrenic motoneuron pool. Delivery of exogenous BDNF either via intrathecal infusion or via mesenchymal stem cells engineered to release BDNF similarly enhance recovery. Conversely, recovery after SH is blunted by quenching endogenous BDNF with the fusion-protein TrkB-Fc in the region of the phrenic motoneuron pool or by selective inhibition of TrkB kinase activity using a chemical-genetic approach in TrkB(F616A) mice. Furthermore, the importance of BDNF signaling via TrkB receptors at phrenic motoneurons is highlighted by the blunting of recovery by siRNA-mediated downregulation of TrkB receptor expression in phrenic motoneurons and by the enhancement of recovery evident following virally-induced increases in TrkB expression specifically in phrenic motoneurons. BDNF/TrkB signaling regulates synaptic plasticity in various neuronal systems, including glutamatergic pathways. Glutamatergic neurotransmission constitutes the main inspiratory-related, excitatory drive to motoneurons, and following SH, spontaneous neuroplasticity is associated with increased expression of ionotropic N-methyl-d-aspartate (NMDA) receptors in phrenic motoneurons. Evidence for the role of BDNF/TrkB and glutamatergic signaling in recovery of DIAm activity following cervical SCI is reviewed.
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Affiliation(s)
- Luther C Gill
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN 55906, United States
| | - Heather M Gransee
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN 55906, United States
| | - Gary C Sieck
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN 55906, United States; Department of Anesthesiology, Mayo Clinic, Rochester, MN 55906, United States
| | - Carlos B Mantilla
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN 55906, United States; Department of Anesthesiology, Mayo Clinic, Rochester, MN 55906, United States.
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10
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Abstract
Brain-derived neurotrophic factor (BDNF) supports innervation of the carotid body by neurons projecting from the petrosal ganglion. Although carotid body glomus cells also express TrkB, BDNF's high affinity receptor, the role of BDNF in carotid body growth and O2 sensitivity has not been studied. Neonatal rats were treated with the TrkB antagonist K252a (100 μg kg(-1), i.p., b.i.d.) or vehicle on postnatal days P0-P6 and studied on P7. Carotid body volume was decreased by 35% after chronic K252a (P<0.001); a reduction in carotid body size was also elicited using the more selective TrkB antagonist ANA-12 (500 μg kg(-1), i.p., b.i.d.). In contrast, single-unit chemoafferent responses to 5% O2, measured in vitro, were unaffected by chronic K252a administration. Normoxic and hypoxic ventilation, measured by head-body plethysmography, were also normal after chronic K252a administration, but acute K252a administration produced a slower, deeper breathing pattern during the transition into hypoxia. These data suggest that BDNF regulates postnatal carotid body growth but does not influence the development of glomus cell O2 sensitivity.
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11
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Sieck GC, Mantilla CB. CrossTalk opposing view: The diaphragm muscle does not atrophy as a result of inactivity. J Physiol 2015; 591:5259-62. [PMID: 24187074 DOI: 10.1113/jphysiol.2013.254698] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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12
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Greising SM, Ermilov LG, Sieck GC, Mantilla CB. Ageing and neurotrophic signalling effects on diaphragm neuromuscular function. J Physiol 2014; 593:431-40. [PMID: 25630263 DOI: 10.1113/jphysiol.2014.282244] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Accepted: 10/23/2014] [Indexed: 12/22/2022] Open
Abstract
The age-related mechanisms underlying sarcopenia are largely unknown. We hypothesize that age-related neuromuscular changes depend on brain-derived neurotrophic factor (BDNF) acting through the tropomyosin-related kinase receptor B (TrkB). Maximal specific force and neuromuscular transmission failure were assessed at 6, 18 and 24 months following control, BDNF or phosphoprotein phosphatase 1 derivative (1NMPP1) treatment in male TrkB(F616A) mice. Phosphoprotein phosphatase-1 derivatives such as 1NMPP1 inhibit TrkB kinase activity as a result of this single amino acid mutation in the ATP binding domain. Maximal twitch and isometric tetanic force were reduced at 24 months compared to 6 and 18 months (P < 0.001). Neuromuscular transmission failure significantly increased at 18 and 24 months compared to 6 months (age × treatment interaction: P < 0.001). Neuromuscular transmission was improved following BDNF at 6 and 18 months and was impaired only at 6 months following 1NMPP1 treatment. Age and inhibition of TrkB kinase activity had similar effects on neuromuscular transmission failure, supporting a critical role for BDNF/TrkB signalling on neuromuscular changes in ageing. These results suggest that an age-related loss of endogenous BDNF precedes reductions in TrkB kinase activity in the diaphragm muscle.
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Affiliation(s)
- Sarah M Greising
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
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13
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Mantilla CB, Stowe JM, Sieck DC, Ermilov LG, Greising SM, Zhang C, Shokat KM, Sieck GC. TrkB kinase activity maintains synaptic function and structural integrity at adult neuromuscular junctions. J Appl Physiol (1985) 2014; 117:910-20. [PMID: 25170066 DOI: 10.1152/japplphysiol.01386.2013] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Activation of the tropomyosin-related kinase receptor B (TrkB) by brain-derived neurotrophic factor acutely regulates synaptic transmission at adult neuromuscular junctions (NMJs). The role of TrkB kinase activity in the maintenance of NMJ function and structure at diaphragm muscle NMJs was explored using a chemical-genetic approach that permits reversible inactivation of TrkB kinase activity in TrkB(F616A) mice by 1NMPP1. Inhibiting TrkB kinase activity for 7 days resulted in significant, yet reversible, impairments in neuromuscular transmission at diaphragm NMJs. Neuromuscular transmission failure following 2 min of repetitive phrenic nerve stimulation increased from 42% in control to 59% in 1NMPP1-treated TrkB(F616A) mice (P = 0.010). Recovery of TrkB kinase activity following withdrawal of 1NMPP1 treatment improved neuromuscular transmission (P = 0.006). Electrophysiological measurements at individual diaphragm NMJs documented lack of differences in quantal content in control and 1NMPP1-treated mice (P = 0.845). Morphological changes at diaphragm NMJs were modest following inhibition and recovery of TrkB kinase activity. Three-dimensional reconstructions of diaphragm NMJs revealed no differences in volume at motor end plates (labeled by α-bungarotoxin; P = 0.982) or presynaptic terminals (labeled by synaptophysin; P = 0.515). Inhibition of TrkB kinase activity by 1NMPP1 resulted in more compact NMJs, with increased apposition of presynaptic terminals and motor end plates (P = 0.017) and reduced fragmentation of motor end plates (P = 0.005). Recovery of TrkB kinase activity following withdrawal of 1NMPP1 treatment resulted in postsynaptic remodeling likely reflecting increased gutter depth (P = 0.007), without significant presynaptic changes. These results support an essential role for TrkB kinase activity in maintaining synaptic function and structural integrity at NMJs in the adult mouse diaphragm muscle.
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Affiliation(s)
- Carlos B Mantilla
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota; Department of Anesthesiology, Mayo Clinic College of Medicine, Rochester, Minnesota; and
| | - Jessica M Stowe
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota
| | - Dylan C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota
| | - Leonid G Ermilov
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota
| | - Sarah M Greising
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota
| | - Chao Zhang
- Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, California
| | - Kevan M Shokat
- Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, California
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota; Department of Anesthesiology, Mayo Clinic College of Medicine, Rochester, Minnesota; and
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14
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Mantilla CB, Greising SM, Stowe JM, Zhan WZ, Sieck GC. TrkB kinase activity is critical for recovery of respiratory function after cervical spinal cord hemisection. Exp Neurol 2014; 261:190-5. [PMID: 24910201 DOI: 10.1016/j.expneurol.2014.05.027] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Revised: 05/27/2014] [Accepted: 05/30/2014] [Indexed: 01/24/2023]
Abstract
Neuroplasticity following spinal cord injury contributes to spontaneous recovery over time. Recent studies highlight the important role of brain-derived neurotrophic factor (BDNF) signaling via the high-affinity tropomyosin-related kinase (Trk) receptor subtype B (TrkB) in recovery of rhythmic diaphragm activity following unilateral spinal hemisection at C2 (C2SH). We hypothesized that TrkB kinase activity is necessary for spontaneous recovery of diaphragm activity post-C2SH. A chemical-genetic approach employing adult male TrkB(F616A) mice (n=49) was used to determine the impact of inhibiting TrkB kinase activity by the phosphoprotein phosphatase 1 inhibitor derivative 1NMPP1 on recovery of ipsilateral hemidiaphragm EMG activity. In mice, C2SH was localized primarily to white matter tracts comprising the lateral funiculus. The extent of damaged spinal cord (~27%) was similar regardless of the presence of functional recovery, consistent with spontaneous recovery reflecting neuroplasticity primarily of contralateral spared descending pathways to the phrenic motor pools. Ipsilateral hemidiaphragm EMG activity was verified as absent in all mice at 3days post-C2SH. By 2weeks after C2SH, ipsilateral hemidiaphragm EMG activity was present in 39% of vehicle-treated mice compared to 7% of 1NMPP1-treated mice (P=0.03). These data support the hypothesis that BDNF/TrkB signaling involving TrkB kinase activity plays a critical role in spontaneous recovery of diaphragm activity following cervical spinal cord injury.
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Affiliation(s)
- Carlos B Mantilla
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN 55905, USA; Department of Anesthesiology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
| | - Sarah M Greising
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
| | - Jessica M Stowe
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
| | - Wen-Zhi Zhan
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN 55905, USA; Department of Anesthesiology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
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15
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Bordoni B, Zanier E. Anatomic connections of the diaphragm: influence of respiration on the body system. J Multidiscip Healthc 2013; 6:281-91. [PMID: 23940419 PMCID: PMC3731110 DOI: 10.2147/jmdh.s45443] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The article explains the scientific reasons for the diaphragm muscle being an important crossroads for information involving the entire body. The diaphragm muscle extends from the trigeminal system to the pelvic floor, passing from the thoracic diaphragm to the floor of the mouth. Like many structures in the human body, the diaphragm muscle has more than one function, and has links throughout the body, and provides the network necessary for breathing. To assess and treat this muscle effectively, it is necessary to be aware of its anatomic, fascial, and neurologic complexity in the control of breathing. The patient is never a symptom localized, but a system that adapts to a corporeal dysfunction.
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Affiliation(s)
- Bruno Bordoni
- Rehabilitation Cardiology Institute of Hospitalization and Care with Scientific Address, S Maria Nascente Don Carlo Gnocchi Foundation
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16
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Personius KE, Parker SD. TrkB expression at the neuromuscular junction is reduced during aging. Muscle Nerve 2012. [PMID: 23180620 DOI: 10.1002/mus.23616] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
INTRODUCTION Full-length tyrosine kinase B (TrkB.FL) and truncated TrkB (TrkB.t1) receptors are colocalized with acetylcholine receptors (AChRs) at the neuromuscular junction. We have recently shown that reduced TrkB expression leads to age-related alterations in AChR structure, neurotransmission failure, and muscle weakness. METHODS We investigated whether TrkB expression is reduced in the soleus muscle during aging. RESULTS TrkB protein expression was decreased in senescent (24-month-old) compared with 3-12-month-old mice. Loss of TrkB expression was concurrent with age-related changes in AChR morphology. Changes in mRNA levels did not correlate with protein expression, because TrkB.FL copy number was increased in the senescent soleus. No change was seen in TrkB.t1 levels. CONCLUSIONS The results suggest that reduced TrkB expression during aging may result from reduced TrkB.FL mRNA translation or increased TrkB protein turnover. Thus, maintaining adequate TrkB signaling is a potential therapeutic tool to improve muscle function during senescence.
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Affiliation(s)
- Kirkwood E Personius
- Program in Neuroscience, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York, USA.
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17
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Greising SM, Gransee HM, Mantilla CB, Sieck GC. Systems biology of skeletal muscle: fiber type as an organizing principle. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2012; 4:457-73. [PMID: 22811254 DOI: 10.1002/wsbm.1184] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Skeletal muscle force generation and contraction are fundamental to countless aspects of human life. The complexity of skeletal muscle physiology is simplified by fiber type classification where differences are observed from neuromuscular transmission to release of intracellular Ca(2+) from the sarcoplasmic reticulum and the resulting recruitment and cycling of cross-bridges. This review uses fiber type classification as an organizing and simplifying principle to explore the complex interactions between the major proteins involved in muscle force generation and contraction.
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Affiliation(s)
- Sarah M Greising
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
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18
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Abstract
Muscle plasticity is defined as the ability of a given muscle to alter its structural and functional properties in accordance with the environmental conditions imposed on it. As such, respiratory muscle is in a constant state of remodeling, and the basis of muscle's plasticity is its ability to change protein expression and resultant protein balance in response to varying environmental conditions. Here, we will describe the changes of respiratory muscle imposed by extrinsic changes in mechanical load, activity, and innervation. Although there is a large body of literature on the structural and functional plasticity of respiratory muscles, we are only beginning to understand the molecular-scale protein changes that contribute to protein balance. We will give an overview of key mechanisms regulating protein synthesis and protein degradation, as well as the complex interactions between them. We suggest future application of a systems biology approach that would develop a mathematical model of protein balance and greatly improve treatments in a variety of clinical settings related to maintaining both muscle mass and optimal contractile function of respiratory muscles.
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Affiliation(s)
- Heather M Gransee
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
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19
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Kulakowski SA, Parker SD, Personius KE. Reduced TrkB expression results in precocious age-like changes in neuromuscular structure, neurotransmission, and muscle function. J Appl Physiol (1985) 2011; 111:844-52. [PMID: 21737823 DOI: 10.1152/japplphysiol.00070.2011] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Acute blockade of signaling through the tyrosine kinase receptor B (TrkB) attenuates neuromuscular transmission and fragments postsynaptic acetylcholine receptors (AChRs) in adult mice, suggesting that TrkB signaling is a key regulator of neuromuscular function. Using immunohistochemical, histological, and in vitro muscle contractile techniques, we tested the hypothesis that constitutively reduced TrkB expression would disrupt neuromuscular pre- and postsynaptic structure, neurotransmission, muscle fiber size, and muscle function in the soleus muscle of 6- to 8-mo-old TrkB⁺/⁻ mice compared with age-matched littermates. Age-like expansion of postsynaptic AChR area, AChR fragmentation, and denervation was observed in TrkB⁺/⁻ mice similar to that found in 24-mo-old wild-type mice. Neurotransmission failure was increased in TrkB⁺/⁻ mice, suggesting that these morphologic changes were sufficient to alter synaptic function. Reduced TrkB expression resulted in decreased muscle strength and fiber cross-sectional area. Immunohistochemical and muscle retrograde labeling experiments show that motor neuron number and size are unaffected in TrkB⁺/⁻ mice. These results suggest that TrkB- signaling at the neuromuscular junction plays a role in synaptic stabilization, neurotransmission, and muscle function and may impact the aging process of sarcopenia.
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Affiliation(s)
- Scott A Kulakowski
- Program in Neuroscience, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York, USA
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20
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Abstract
The neuregulin (NRG) family of trophic factors is present in the central and peripheral nervous systems and participates in the survival, proliferation, and differentiation of many different cell types, including motoneurons. NRG1 was first characterized by its role in the formation of the neuromuscular junction, and recently it was shown to play a crucial role in modulating glutamatergic and cholinergic transmission in the central nervous system of adult rats. However, little is known about NRG1's role in adult motor systems. Motoneurons receive dense glutamatergic and cholinergic input. We hypothesized that NRG1 is present at synapses on phrenic motoneurons. Confocal microscopy and 3D reconstruction techniques were used to determine the distribution of NRG1 and its colocalization with these different neurotransmitter systems. We found that NRG1 puncta are present around retrogradely labeled motoneurons and are distributed predominantly at motoneuron somata and primary dendrites. NRG1 is present exclusively at synaptic sites (identified using the presynaptic marker synaptophysin), making up ∼30% of all synapses at phrenic motoneurons. Overall, NRG1 immunoreactivity is found predominantly at cholinergic synapses (75% ± 14% colocalize with the vesicular acetylcholine transporter; VAChT). Nearly all (99% ± 1%) VAChT-immunoreactive synapses expressed NRG1. NRG1 also is present at a subset of glutamatergic synapses expressing the vesicular glutamate transporter (VGLUT) type 2 (∼6%) but not those expressing VGLUT type 1. Overall, 26% ± 6% of NRG1 synapses are VGLUT2 immunoreactive. These findings provide the first evidence suggesting that NRG1 may modulate synaptic activity in adult motor systems.
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Affiliation(s)
- Amine N Issa
- Department of Physiology and Biomedical Engineering, College of Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA
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21
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Mantilla CB, Sieck GC. Neuromuscular adaptations to respiratory muscle inactivity. Respir Physiol Neurobiol 2009; 169:133-40. [PMID: 19744580 DOI: 10.1016/j.resp.2009.09.002] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2009] [Revised: 08/30/2009] [Accepted: 09/01/2009] [Indexed: 01/13/2023]
Abstract
Cervical spinal cord injury results in significant functional impairment. It is important to understand the neuroplasticity in response to inactivity of respiratory muscles in order to prevent any associated effects that limit functional recovery. Recent studies have examined the mechanisms involved in inactivity-induced neuroplasticity of diaphragm motor units. Both spinal hemisection at C2 (C2HS) and tetrodotoxin (TTX)-induced phrenic nerve blockade result in diaphragm paralysis and inactivity of axon terminals. However, phrenic motoneurons are inactive with C2HS but remain active after TTX. Diaphragm muscle fibers ipsilateral to C2HS display minimal changes post-injury. Neuromuscular transmission is enhanced following C2HS but impaired following TTX. Synaptic vesicle pool size at diaphragm neuromuscular junctions increases after C2HS, but decreases after TTX. Thus, inactivity-induced neuromuscular plasticity reflects specific adaptations that depend on inactivity at the motoneuron rather than at axon terminals or muscle fibers. These results indicate that neuromuscular transmission and functional properties of diaphragm fibers can be maintained after spinal cord injury, providing a substrate for functional recovery and/or specific therapeutic approaches such as phrenic pacing.
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Affiliation(s)
- Carlos B Mantilla
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, United States.
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22
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Sieck GC, Mantilla CB. Role of neurotrophins in recovery of phrenic motor function following spinal cord injury. Respir Physiol Neurobiol 2009; 169:218-25. [PMID: 19703592 DOI: 10.1016/j.resp.2009.08.008] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2009] [Revised: 08/07/2009] [Accepted: 08/17/2009] [Indexed: 01/09/2023]
Abstract
Many individuals who sustain a cervical spinal cord injury are unable to maintain adequate ventilation due to diaphragm muscle paralysis. These patients become dependent on mechanical ventilators and this situation is associated with ongoing problems with pulmonary clearance, infections, and lung injury leading to significant morbidity and reduced life expectancy. Therefore, functional recovery of rhythmic phrenic activity and the ability to generate expulsive forces would dramatically affect the quality of life of patients with cervical spinal cord injury. Neurotrophins are very promising in that they have been shown to play an important role in modulating functional neuroplasticity. Specifically, brain-derived neurotrophic factor (BDNF) acting via the tropomyosin-related kinase receptor type B (TrkB) has been implicated in neuroplasticity following spinal cord injury. Our central hypothesis is that functional recovery of rhythmic phrenic activity after cervical spinal cord injury is enhanced by an increase in BDNF/TrkB signaling in phrenic motoneurons, providing a novel therapeutic target for patients.
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Affiliation(s)
- Gary C Sieck
- Departments of Physiology & Biomedical Engineering and Anesthesiology, Mayo Clinic, Rochester, MN 55905, United States.
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McCrimmon DR, Mitchell GS, Alheid GF. Overview: the neurochemistry of respiratory control. Respir Physiol Neurobiol 2008; 164:1-2. [PMID: 18721910 PMCID: PMC2642897 DOI: 10.1016/j.resp.2008.07.021] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2008] [Accepted: 07/23/2008] [Indexed: 01/25/2023]
Abstract
This special issue of Respiratory Physiology and Neurobiology surveys a broad range of topics focused on the neurochemical control of breathing. A variety of approaches have integrated the neurochemistry of breathing with the physiology of individual neurons, with the neuroanatomy of brainstem and forebrain respiratory circuits, and with the clinical pathology of respiratory disorders all of which has been fueled by the ongoing explosion of information in the molecular biology of the nervous system. Accordingly, substantial progress has identified neurotransmitters, neuromodulators, receptors, signaling cascades, trophic factors, hormones, and genes mediating normal and pathological breathing. Dynamic changes in the neurochemistry of breathing are addressed with respect to brainstem development, environmental challenges such as intermittent or chronic hypoxia, and as a function of the sleep-wake cycle. Respiratory disruption has also been identified in an increasing variety of genetic-based disorders and remarkable progress has been made in determining the affected genes and their mutations that negatively impact respiration.
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Affiliation(s)
- Donald R. McCrimmon
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA 60611−3088
| | - Gordon S. Mitchell
- Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI, USA, 53706
| | - George F. Alheid
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA 60611−3088
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