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Lee KZ, Vinit S. Modulatory effect of trans-spinal magnetic intermittent theta burst stimulation on diaphragmatic activity following cervical spinal cord contusion in the rat. Spine J 2024; 24:352-372. [PMID: 37774983 DOI: 10.1016/j.spinee.2023.09.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 09/17/2023] [Accepted: 09/18/2023] [Indexed: 10/01/2023]
Abstract
BACKGROUND CONTEXT Magnetic stimulation can noninvasively modulate the neuronal excitability through different stimulatory patterns. PURPOSE The present study hypothesized that trans-spinal magnetic stimulation with intermittent theta burst stimulatory pattern can modulate respiratory motor outputs in a pre-clinical rat model of cervical spinal cord injury. STUDY DESIGN In vivo animal study. METHODS The effect of trans-spinal magnetic intermittent theta burst stimulation on diaphragmatic activity was assessed in adult rats with unilateral cervical spinal cord contusion at 2 weeks postinjury. RESULTS The results demonstrated that unilateral cervical spinal cord contusion significantly attenuated the inspiratory activity and motor evoked potential of the diaphragm. Trans-spinal magnetic intermittent theta burst stimulation significantly increased the inspiratory activity of the diaphragm in cervical spinal cord contused rats. Inspiratory bursting was also recruited by trans-spinal magnetic intermittent theta burst stimulation in the rats without diaphragmatic activity after cervical spinal cord injury. In addition, trans-spinal magnetic intermittent theta burst stimulation is associated with increases in oxygen consumption and carbon dioxide production. CONCLUSIONS These results suggest that trans-spinal magnetic intermittent theta burst stimulation can induce respiratory neuroplasticity. CLINICAL SIGNIFICANCE We propose that trans-spinal theta burst magnetic stimulation may be considered a potential rehabilitative strategy for improving the respiratory activity after cervical spinal cord injury. This will require future clinical study.
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Affiliation(s)
- Kun-Ze Lee
- Department of Biological Sciences, National Sun Yat-sen University, #70 Lien-Hai Rd, Kaohsiung, 804 Taiwan; Department of Biomedical Science and Environmental Biology, Kaohsiung Medical University, 9F, First Teaching Building, 100, Shih-Chuan 1st Road, Kaohsiung, 807, Taiwan.
| | - Stéphane Vinit
- END-ICAP, UVSQ, Inserm, Université Paris-Saclay, Versailles 78000, France
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Thakre PP, Rana S, Benevides ES, Fuller DD. Targeting drug or gene delivery to the phrenic motoneuron pool. J Neurophysiol 2023; 129:144-158. [PMID: 36416447 PMCID: PMC9829468 DOI: 10.1152/jn.00432.2022] [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: 10/13/2022] [Revised: 11/19/2022] [Accepted: 11/19/2022] [Indexed: 11/24/2022] Open
Abstract
Phrenic motoneurons (PhrMNs) innervate diaphragm myofibers. Located in the ventral gray matter (lamina IX), PhrMNs form a column extending from approximately the third to sixth cervical spinal segment. Phrenic motor output and diaphragm activation are impaired in many neuromuscular diseases, and targeted delivery of drugs and/or genetic material to PhrMNs may have therapeutic application. Studies of phrenic motor control and/or neuroplasticity mechanisms also typically require targeting of PhrMNs with drugs, viral vectors, or tracers. The location of the phrenic motoneuron pool, however, poses a challenge. Selective PhrMN targeting is possible with molecules that move retrogradely upon uptake into phrenic axons subsequent to diaphragm or phrenic nerve delivery. However, nonspecific approaches that use intrathecal or intravenous delivery have considerably advanced the understanding of PhrMN control. New opportunities for targeted PhrMN gene expression may be possible with intersectional genetic methods. This article provides an overview of methods for targeting the phrenic motoneuron pool for studies of PhrMNs in health and disease.
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Affiliation(s)
- Prajwal P Thakre
- Department of Physical Therapy, University of Florida, Gainesville, Florida
- McKnight Brain Institute, University of Florida, Gainesville, Florida
- Breathing Research and Therapeutics Center, Gainesville, Florida
| | - Sabhya Rana
- Department of Physical Therapy, University of Florida, Gainesville, Florida
- McKnight Brain Institute, University of Florida, Gainesville, Florida
- Breathing Research and Therapeutics Center, Gainesville, Florida
| | - Ethan S Benevides
- Department of Physical Therapy, University of Florida, Gainesville, Florida
- McKnight Brain Institute, University of Florida, Gainesville, Florida
- Breathing Research and Therapeutics Center, Gainesville, Florida
| | - David D Fuller
- Department of Physical Therapy, University of Florida, Gainesville, Florida
- McKnight Brain Institute, University of Florida, Gainesville, Florida
- Breathing Research and Therapeutics Center, Gainesville, Florida
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Lee KZ. Neuropathology of distinct diaphragm areas following mid-cervical spinal cord contusion in the rat. Spine J 2022; 22:1726-1741. [PMID: 35680014 DOI: 10.1016/j.spinee.2022.05.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Revised: 05/17/2022] [Accepted: 05/26/2022] [Indexed: 02/03/2023]
Abstract
BACKGROUND The diaphragm is innervated by phrenic motoneurons distributed from the third to fifth cervical spinal cord. The rostral to caudal phrenic motoneuron pool segmentally innervates the ventral, medial, and dorsal diaphragm. PURPOSE The present study was designed to investigate the physiological and transcriptomic mechanism of neuropathology of distinct diaphragm areas following mid-cervical spinal cord injury. STUDY DESIGN In vivo animal study. METHODS Electromyograms and transcriptome of the ventral, medial, and dorsal diaphragm were examined in rats that received cervical laminectomy or mid-cervical spinal cord contusion in the acute (ie, 1-3 days) or subchronic (ie, ∼14 days) injury stages. RESULTS Mid-cervical spinal cord contusion significantly attenuated the inspiratory bursting amplitude of the dorsal diaphragm but not the ventral or medial diaphragm. Moreover, the discharge onset of the dorsal diaphragm was significantly delayed compared with that of the ventral and medial diaphragm in contused rats. Transcriptomic analysis revealed a robust change in gene expression in the ventral diaphragm compared with that in the dorsal diaphragm. Specifically, enrichment analysis of differentially expressed genes demonstrated that the cell cycle and immune response were significantly upregulated, whereas several metabolic pathways were downregulated, in the ventral diaphragm of acutely contused rats. However, no significant Kyoto Encyclopedia of Genes and Genomes pathway was altered in the dorsal diaphragm. CONCLUSIONS These results suggest that mid-cervical spinal cord injury has different impacts on the physiological and transcriptomic responses of distinct diaphragm areas. CLINICAL SIGNIFICANCE Future therapeutic strategies can consider applying different therapies to distinct diaphragm areas following cervical spinal cord injury. Additionally, confirmation of activities across different diaphragm areas may provide a critical reference for the placement of diaphragmatic pacing electrodes.
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Affiliation(s)
- Kun-Ze Lee
- Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan; Department of Biomedical Science and Environmental Biology, Kaohsiung Medical University, Kaohsiung, Taiwan.
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Perim RR, Sunshine MD, Welch JF, Santiago J, Holland A, Ross A, Mitchell GS, Gonzalez-Rothi EJ. Daily acute intermittent hypoxia enhances phrenic motor output and stimulus-evoked phrenic responses in rats. J Neurophysiol 2021; 126:777-790. [PMID: 34260289 DOI: 10.1152/jn.00112.2021] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Plasticity is a hallmark of the respiratory neural control system. Phrenic long-term facilitation (pLTF) is one form of respiratory plasticity characterized by persistent increases in phrenic nerve activity following acute intermittent hypoxia (AIH). Although there is evidence that key steps in the cellular pathway giving rise to pLTF are localized within phrenic motor neurons (PMNs), the impact of AIH on the strength of breathing-related synaptic inputs to PMNs remains unclear. Further, the functional impact of AIH is enhanced by repeated/daily exposure to AIH (dAIH). Here, we explored the effects of AIH vs. 2 weeks of dAIH preconditioning on spontaneous and evoked responses recorded in anesthetized, paralyzed (with pancuronium bromide) and mechanically ventilated rats. Evoked phrenic potentials were elicited by respiratory cycle-triggered lateral funiculus stimulation at C2 delivered prior to- and 60 min post-AIH (or an equivalent time in controls). Charge-balanced biphasic pulses (100 µs/phase) of progressively increasing intensity (100 to 700 µA) were delivered during the inspiratory and expiratory phases of the respiratory cycle. Although robust pLTF (~60% from baseline) was observed after a single exposure to moderate AIH (3 x 5 min; 5 min intervals), there was no effect on evoked phrenic responses, contrary to our initial hypothesis. However, in rats preconditioned with dAIH, baseline phrenic nerve activity and evoked responses were increased, suggesting that repeated exposure to AIH enhances functional synaptic strength when assessed using this technique. The impact of daily AIH preconditioning on synaptic inputs to PMNs raises interesting questions that require further exploration.
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Affiliation(s)
- Raphael Rodrigues Perim
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Michael D Sunshine
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Joseph F Welch
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Juliet Santiago
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Ashley Holland
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Ashley Ross
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Gordon S Mitchell
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Elisa J Gonzalez-Rothi
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL, United States
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Bezdudnaya T, Lane MA, Marchenko V. Pharmacological disinhibition enhances paced breathing following complete spinal cord injury in rats. Respir Physiol Neurobiol 2020; 282:103514. [PMID: 32750492 PMCID: PMC9793860 DOI: 10.1016/j.resp.2020.103514] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 07/12/2020] [Accepted: 07/29/2020] [Indexed: 12/30/2022]
Abstract
Respiratory dysfunction is one of the most devastating and life-threatening deficits that occurs following cervical spinal cord injury (SCI). Assisted breathing with mechanical ventilators is a necessary part of care for many cervical injured individuals, but it is also associated with increased risk of secondary complications such as infection, muscle atrophy and maladaptive plasticity. Pre-clinical studies with epidural stimulation (EDS) have identified it as an alternative/additional method to support adequate lung ventilation without mechanical assistance. The full potential of EDS, however, may be limited by spinal inhibitory mechanisms within the injured spinal cord. The goal of the present work is to assess the potential improvement for EDS in combination with pharmacological disinhibition of spinal circuits following complete high cervical SCI. All experiments were performed in decerebrate, unanesthetized, non-paralyzed (n = 13) and paralyzed (n = 8) adult Sprague-Dawley rats 6 h following a complete C1 transection. The combination of high-frequency EDS (HF-EDS) at the C4 spinal segment with intrathecal delivery of GABA and glycine receptors antagonists (GABAzine and strychnine, respectively) resulted in significantly increased phrenic motor output, tidal volume and amplitude of diaphragm electrical activity compared to HF-EDS alone. Thus, it appears that spinal fast inhibitory mechanisms limit phrenic motor output and present a new neuropharmacological target to improve paced breathing in individuals with cervical SCI.
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Affiliation(s)
- T Bezdudnaya
- Drexel University College of Medicine, Department of Neurobiology & Anatomy, 2900 W Queen Lane, Philadelphia, PA, 19129, United States
| | - M A Lane
- Drexel University College of Medicine, Department of Neurobiology & Anatomy, 2900 W Queen Lane, Philadelphia, PA, 19129, United States
| | - V Marchenko
- Drexel University College of Medicine, Department of Neurobiology & Anatomy, 2900 W Queen Lane, Philadelphia, PA, 19129, United States; Medical College of Wisconsin, Department of Anesthesiology, 8701 W Watertown Plank Rd, Wauwatosa, WI, 53226, United States.
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George Zaki Ghali M. Midbrain control of breathing and blood pressure: The role of periaqueductal gray matter and mesencephalic collicular neuronal microcircuit oscillators. Eur J Neurosci 2020; 52:3879-3902. [PMID: 32227408 DOI: 10.1111/ejn.14727] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2019] [Revised: 02/01/2020] [Accepted: 03/22/2020] [Indexed: 01/12/2023]
Abstract
Neural circuitry residing within the medullary ventral respiratory column nuclei and dorsal respiratory group interact with the Kölliker-Fuse and medial parabrachial nuclei to generate the core breathing rhythm and pattern during resting conditions. Triphasic eupnea consists of inspiratory [I], post-inspiratory [post-I], and late-expiratory [E2] phases. Mesencephalic zones exert modulatory influences upon respiratory rhythm-generating circuitry, sympathetic oscillators, and parasympathetic nuclei. The earliest evidence supporting the existence of midbrain control of breathing derives from studies conducted by Martin and Booker in 1878. These authors demonstrated electrical stimulation of the deep layers of the mesencephalic colliculi in the rabbit augmented ventilation and sequentially elicited chest wall tremors and tetany. Investigations performed during the past several decades would demonstrate stimlation of distributed zones within the midbrain reticular formation elicits starkly disparate effects upon respiratory phase switching. Schmid, Böhmer, and Fallert demonstrated electrical stimulation of the nucleus rubre and emanating axon bundles alternately elicits or inhibits the activity of medullary expiratory- or inspiratory-related units and phrenic nerve discharge with differential latency. A series of studies would later indicate the red nucleus mediates hypoxic ventilatory depression. Periaqueductal gray matter neurons exhibit extensive afferent and efferent interconnectivity with suprabulbar, brainstem, and spinal cord zones aptly positioning these units to modulate breathing, autonomic outflow, nociception locomotion, micturtion, and sexual behavior. Experimental stimulatory activation of the tectal colliculi and periaqueductal gray matter via electrical current or glutamate, D,L-homocysteinic acid, or bicuculline microinjections coordinately modulates neuromotor inspiratory bursting frequency and amplitude and discharge of pre-Bötzinger complex, ventrolateral medullary late-I and post-I, and ventrolateral nucleus tractus solitarius decrementing early-I and augmenting and decrementing late-I neurons, elicits expiratory outflow and vocalization, and blunt the Hering-Breuer reflex in unanesthetzed decerebrate and anesthetized preprations of the cat and rat. Stimulation of the mesencephalic colliuli or dorsal divisions of the PAG potently amplifes renal sympathetic neural efferent activity, dynamic arterial pressure magnitude, and myocardial contraction frequency and elicits various behavioral defense responses. Elicited physiological effects exhibit extensive locoregional heterogeneity and variably enlist requisite contributions from the dorsomedial hypothalamus and/or lateral parabrachial nuclei. Stimulation of the dorsal mesencephalon occasionally elicits dynamic increases of arterial pressure magnitude exhibiting prominent oscillatory variability coherent with phrenic nerve discharge, perhaps by generating intra-neuraxial hysteresis, serving to intermittently deliver blood to organ vascular beds under high pressure in order to prevent organ edema, microcirculatory dysfunction, and downregulation of vascular smooth muscle alpha adrenergic receptors. Chemosensitive mesencephalic caudal raphé units and projections of hypoxia-sensitive units in the caudal hypothalamus to the periaqueductal gray matter may imply the existence of a diencephalo-smesencephalic chemosensitive network modulating breathing and sympathetic discharge.
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Affiliation(s)
- Michael George Zaki Ghali
- Department of Neurological Surgery, Baylor College of Medicine, Houston, Texas.,Department of Neurological Surgery, University of California, San Francisco, California.,Department of Neurological Surgery, Karolinska Institutet, Stockholm, Sweden
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Jensen VN, Alilain WJ, Crone SA. Role of Propriospinal Neurons in Control of Respiratory Muscles and Recovery of Breathing Following Injury. Front Syst Neurosci 2020; 13:84. [PMID: 32009911 PMCID: PMC6978673 DOI: 10.3389/fnsys.2019.00084] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Accepted: 12/16/2019] [Indexed: 12/20/2022] Open
Abstract
Respiratory motor failure is the leading cause of death in spinal cord injury (SCI). Cervical injuries disrupt connections between brainstem neurons that are the primary source of excitatory drive to respiratory motor neurons in the spinal cord and their targets. In addition to direct connections from bulbospinal neurons, respiratory motor neurons also receive excitatory and inhibitory inputs from propriospinal neurons, yet their role in the control of breathing is often overlooked. In this review, we will present evidence that propriospinal neurons play important roles in patterning muscle activity for breathing. These roles likely include shaping the pattern of respiratory motor output, processing and transmitting sensory afferent information, coordinating ventilation with motor activity, and regulating accessory and respiratory muscle activity. In addition, we discuss recent studies that have highlighted the importance of propriospinal neurons for recovery of respiratory muscle function following SCI. We propose that molecular genetic approaches to target specific developmental neuron classes in the spinal cord would help investigators resolve the many roles of propriospinal neurons in the control of breathing. A better understanding of how spinal circuits pattern breathing could lead to new treatments to improve breathing following injury or disease.
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Affiliation(s)
- Victoria N. Jensen
- Neuroscience Graduate Program, University of Cincinnati College of Medicine, Cincinnati, OH, United States
| | - Warren J. Alilain
- Spinal Cord and Brain Injury Research Center, University of Kentucky College of Medicine, Lexington, KY, United States,Department of Neuroscience, University of Kentucky College of Medicine, Lexington, KY, United States
| | - Steven A. Crone
- Division of Neurosurgery, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, United States,Division of Developmental Biology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, United States,Department of Neurosurgery, University of Cincinnati College of Medicine, Cincinnati, OH, United States,*Correspondence: Steven A. Crone
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Abstract
Variability in cardiovascular spectra was first described by Stephan Hales in 1733. Traube and Hering initially noted respirophasic variation of the arterial pressure waveform in 1865 and Sigmund Mayer noted a lower frequency oscillation of the same in anesthetized rabbits in 1876. Very low frequency oscillations were noted by Barcroft and Nisimaru in 1932, likely representing vasogenic autorhythmicity. While the origins of Traube Hering and very low frequency oscillatory variability in cardiovascular spectra are well described, genesis mechanisms and functional significance of Mayer waves remain in controversy. Various theories have posited baroreflex and central supraspinal mechanisms for genesis of Mayer waves. Several studies have demonstrated the persistence of Mayer waves following high cervical transection, indicating a spinal capacity for genesis of these oscillations. We suggest a general tendency for central sympathetic neurons to oscillate at the Mayer wave frequency, the presence of multiple Mayer wave oscillators throughout the brainstem and spinal cord, and possible contemporaneous genesis by baroreflex and vasomotor mechanisms.
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Affiliation(s)
- George Zaki Ghali
- United States Environmental Protection Agency, Arlington, VA; Department of Toxicology, Purdue University, West Lafayette, IN, USA
| | - Michael George Zaki Ghali
- Department of Neurological Surgery, Houston Methodist Hospital, Houston, TX; Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, USA
| | - Emil Zaki Ghali
- Department of Medicine, Inova Alexandria Hospital, Alexandria, VA, USA; Department of Cardiothoracic Surgery, El Gomhoureya General Hospital, Alexandria, Egypt
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Sunshine MD, Ganji CN, Fuller DD, Moritz CT. Respiratory resetting elicited by single pulse spinal stimulation. Respir Physiol Neurobiol 2019; 274:103339. [PMID: 31734416 DOI: 10.1016/j.resp.2019.103339] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 11/04/2019] [Accepted: 11/12/2019] [Indexed: 01/21/2023]
Abstract
Intraspinal microstimulation (ISMS) can effectively activate spinal motor circuits, but the impact on the endogenous respiratory pattern has not been systematically evaluated. Here we delivered ISMS in spontaneously breathing adult rats while simultaneously recording diaphragm and external intercostal electromyography activity. ISMS pulses were delivered from C2-T1 along two rostrocaudal tracts located 0.5 or 1 mm lateral to midline. A tungsten electrode was incrementally advanced from the dorsal spinal surface and 300μs biphasic pulses (10-90 μA) were delivered at depth increments of 600 μm. Dorsal ISMS often produced fractionated inspiratory bursting or caused early termination of the inspiratory effort. Conversely, ventral stimulation had no discernable impact on respiratory resetting. We conclude that ISMS targeting the ventral spinal cord is unlikely to directly alter the respiratory rhythm. Dorsal ISMS, however, may terminate the inspiratory burst through activation of spinobulbar pathways. We suggest that respiratory patterns should be included as an outcome variable in preclinical studies of ISMS.
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Affiliation(s)
- Michael D Sunshine
- Department of Rehabilitation Medicine, University of Washington, United States; Center for Neurotechnology, an NSF ERC, United States; Department of Physical Therapy, University of Florida, United States; McKnight Brain Institute, University of Florida, United States; Rehabilitation Science PhD Program, University of Florida, United States; Center for Respiratory Research and Rehabilitation, University of Florida, United States.
| | - Comron N Ganji
- Department of Rehabilitation Medicine, University of Washington, United States
| | - David D Fuller
- Department of Physical Therapy, University of Florida, United States; McKnight Brain Institute, University of Florida, United States; Center for Respiratory Research and Rehabilitation, University of Florida, United States
| | - Chet T Moritz
- Department of Rehabilitation Medicine, University of Washington, United States; Center for Neurotechnology, an NSF ERC, United States; Center for Respiratory Research and Rehabilitation, University of Florida, United States; Department of Electrical and Computer Engineering, United States; University of Washington, Institute for Neuroengineering (UWIN), University of Washington, United States; Department of Physiology and Biophysics, University of Washington, United States
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Zaki Ghali MG, Britz G, Lee KZ. Pre-phrenic interneurons: Characterization and role in phrenic pattern formation and respiratory recovery following spinal cord injury. Respir Physiol Neurobiol 2019; 265:24-31. [DOI: 10.1016/j.resp.2018.09.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Revised: 08/04/2018] [Accepted: 09/16/2018] [Indexed: 01/12/2023]
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Shevtsova NA, Marchenko V, Bezdudnaya T. Modulation of Respiratory System by Limb Muscle Afferents in Intact and Injured Spinal Cord. Front Neurosci 2019; 13:289. [PMID: 30971888 PMCID: PMC6443963 DOI: 10.3389/fnins.2019.00289] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Accepted: 03/11/2019] [Indexed: 12/20/2022] Open
Abstract
Breathing constantly adapts to environmental, metabolic or behavioral changes by responding to different sensory information, including afferent feedback from muscles. Importantly, not just respiratory muscle feedback influences respiratory activity. Afferent sensory information from rhythmically moving limbs has also been shown to play an essential role in the breathing. The present review will discuss the neuronal mechanisms of respiratory modulation by activation of peripheral muscles that usually occurs during locomotion or exercise. An understanding of these mechanisms and finding the most effective approaches to regulate respiratory motor output by stimulation of limb muscles could be extremely beneficial for people with respiratory dysfunctions. Specific attention in the present review is given to the muscle stimulation to treat respiratory deficits following cervical spinal cord injury.
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Affiliation(s)
- Natalia A Shevtsova
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, United States
| | - Vitaliy Marchenko
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, United States
| | - Tatiana Bezdudnaya
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, United States
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12
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Ghali MG. Microsurgical technique for concurrent cervical corpectomy and ventral phrenic nerve access in the rat. MethodsX 2019; 6:239-245. [PMID: 30766804 PMCID: PMC6360515 DOI: 10.1016/j.mex.2018.08.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 08/04/2018] [Indexed: 11/24/2022] Open
Abstract
The phrenic nerve is useful to record as a motor output in studies investigating neural control of respiration. It may be accessed via dorsal or ventral microsurgical approaches. Since such studies frequently involve concurrent access to the spinal cord, the two approaches may be alternatively used, each with its own set of advantages and disadvantages. The dorsal approach permits easier exposure of the spinal cord via laminectomy, but, compared to the ventral approach, phrenic nerve access proves more challenging, and concurrent surgical access to the full complement of respiratory-related nerves (i.e., glossopharyngeal, vagus, recurrent laryngeal, hypoglossal nerves) and cervical sympathetic nerve in the neck is limited. The ventral approach achieves more direct access to the phrenic and respiratory-related nerves, but ventral access to the spinal cord via corpectomy requires much greater diligence and vigilance. Ventral spinal cord access, however, facilitates neuronal (e.g., phrenic motoneuron and interneuron) recordings in the ventral horn of the spinal cord, given greater proximity to the ventral compared to the dorsal surface of the spinal cord providing more leeway in recording pipette insertion point and trajectory. Additionally, ventral access to the cervical spinal cord proves useful across a broad range of studies investigating normal spinal cord physiology as well as spinal cord injury. We detail the microsurgical technique of concurrent ventral phrenic nerve dissection and cervical corpectomy in adult rats.
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The Neuroplastic and Therapeutic Potential of Spinal Interneurons in the Injured Spinal Cord. Trends Neurosci 2018; 41:625-639. [PMID: 30017476 DOI: 10.1016/j.tins.2018.06.004] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Revised: 06/06/2018] [Accepted: 06/12/2018] [Indexed: 12/25/2022]
Abstract
The central nervous system is not a static, hard-wired organ. Examples of neuroplasticity, whether at the level of the synapse, the cell, or within and between circuits, can be found during development, throughout the progression of disease, or after injury. One essential component of the molecular, anatomical, and functional changes associated with neuroplasticity is the spinal interneuron (SpIN). Here, we draw on recent multidisciplinary studies to identify and interrogate subsets of SpINs and their roles in locomotor and respiratory circuits. We highlight some of the recent progress that elucidates the importance of SpINs in circuits affected by spinal cord injury (SCI), especially those within respiratory networks; we also discuss potential ways that spinal neuroplasticity can be therapeutically harnessed for recovery.
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Ghali MGZ. Phrenic motoneurons: output elements of a highly organized intraspinal network. J Neurophysiol 2018; 119:1057-1070. [DOI: 10.1152/jn.00705.2015] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
pontomedullary respiratory network generates the respiratory pattern and relays it to bulbar and spinal respiratory motor outputs. The phrenic motor system controlling diaphragm contraction receives and processes descending commands to produce orderly, synchronous, and cycle-to-cycle-reproducible spatiotemporal firing. Multiple investigators have studied phrenic motoneurons (PhMNs) in an attempt to shed light on local mechanisms underlying phrenic pattern formation. I and colleagues (Marchenko V, Ghali MG, Rogers RF. Am J Physiol Regul Integr Comp Physiol 308: R916–R926, 2015.) recorded PhMNs in unanesthetized, decerebrate rats and related their activity to simultaneous phrenic nerve (PhN) activity by creating a time-frequency representation of PhMN-PhN power and coherence. On the basis of their temporal firing patterns and relationship to PhN activity, we categorized PhMNs into three classes, each of which emerges as a result of intrinsic biophysical and network properties and organizes the orderly contraction of diaphragm motor fibers. For example, early inspiratory diaphragmatic activation by the early coherent burst generated by high-frequency PhMNs may be necessary to prime it to overcome its initial inertia. We have also demonstrated the existence of a prominent role for local intraspinal inhibitory mechanisms in shaping phrenic pattern formation. The objective of this review is to relate and synthesize recent findings with those of previous studies with the aim of demonstrating that the phrenic nucleus is a region of active local processing, rather than a passive relay of descending inputs.
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Affiliation(s)
- Michael George Zaki Ghali
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania
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Romaus-Sanjurjo D, Valle-Maroto SM, Barreiro-Iglesias A, Fernández-López B, Rodicio MC. Anatomical recovery of the GABAergic system after a complete spinal cord injury in lampreys. Neuropharmacology 2018; 131:389-402. [PMID: 29317225 DOI: 10.1016/j.neuropharm.2018.01.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Revised: 12/26/2017] [Accepted: 01/04/2018] [Indexed: 12/16/2022]
Abstract
Lampreys recover locomotion spontaneously several weeks after a complete spinal cord injury. Dysfunction of the GABAergic system following SCI has been reported in mammalian models. So, it is of great interest to understand how the GABAergic system of lampreys adapts to the post-injury situation and how this relates to spontaneous recovery. The spinal cord of lampreys contains 3 populations of GABAergic neurons and most of the GABAergic innervation of the spinal cord comes from these local cells. GABAB receptors are expressed in the spinal cord of lampreys and they play important roles in the control of locomotion. The aims of the present study were to quantify: 1) the changes in the number of GABAergic neurons and innervation of the spinal cord and 2) the changes in the expression of the gabab receptor subunits b1 and b2 in the spinal cord of the sea lamprey after SCI. We performed complete spinal cord transections at the level of the fifth gill of mature larval lampreys and GABA immunohistochemistry or gabab in situ hybridization experiments. Animals were analysed up to 10 weeks post-lesion (wpl), when behavioural analyses showed that they recovered normal appearing locomotion (stage 6 in the Ayer's scale of locomotor recovery). We observed a significant decrease in the number of GABA-ir cells and fibres 1 h after lesion both rostral and caudal to the lesion site. GABA-ir cell numbers and innervation were recovered to control levels 1 to 2 wpl. At 1, 4 and 10 wpl the expression of gabab1 and gabab2 transcripts was significantly decreased in the spinal cord compared to control un-lesioned animals. This is the first study reporting the quantitative long-term changes in the number of GABAergic cells and fibres and in the expression of gabab receptors in the spinal cord of any vertebrate following a traumatic SCI. Our results show that in lampreys there is a full recovery of the GABAergic neurons and a decrease in the expression of gabab receptors when functional recovery is achieved.
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Affiliation(s)
- D Romaus-Sanjurjo
- Department of Functional Biology, CIBUS, Faculty of Biology, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain
| | - S M Valle-Maroto
- Department of Functional Biology, CIBUS, Faculty of Biology, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain
| | - A Barreiro-Iglesias
- Department of Functional Biology, CIBUS, Faculty of Biology, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain
| | - B Fernández-López
- Department of Functional Biology, CIBUS, Faculty of Biology, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain
| | - M C Rodicio
- Department of Functional Biology, CIBUS, Faculty of Biology, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain.
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Sunshine MD, Ganji CN, Reier PJ, Fuller DD, Moritz CT. Intraspinal microstimulation for respiratory muscle activation. Exp Neurol 2018; 302:93-103. [PMID: 29305050 DOI: 10.1016/j.expneurol.2017.12.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 12/20/2017] [Accepted: 12/26/2017] [Indexed: 11/17/2022]
Abstract
A complex propriospinal network is synaptically coupled to phrenic and intercostal motoneurons, and this makes it difficult to predict how gray matter intraspinal microstimulation (ISMS) will recruit respiratory motor units. We therefore mapped the cervical and high thoracic gray matter at locations which ISMS activates diaphragm (DIA) and external intercostal (EIC) motor units. Respiratory muscle electromyography (EMG) was recorded in anesthetized female spinally intact adult rats while a stimulating electrode was advanced ventrally into the spinal cord in 600μm increments. At each depth, single biphasic stimuli were delivered at 10-90μA during both the inspiratory and expiratory phase independently. Twenty electrode tracks were made from C2-T1 at medial and lateral gray matter locations. During inspiration, ISMS evoked DIA and EIC activity throughout C2-T1 gray matter locations, with mutual activation occurring at 17±9% of sites. During inspiratory phase ISMS the average latency for DIA activation was 4.40±0.70ms. During the expiratory phase, ISMS-induced DIA activation required electrodes to be in close proximity to the phrenic motoneuron pool, and average activation latency was 3.30±0.50ms. We conclude that appropriately targeted ISMS can co-activate DIA and EIC motor units, and endogenous respiratory drive has a powerful impact on ISMS-induced respiratory motor unit activation. The long latency diaphragm motor unit activation suggests the presence of a complex propriospinal network that can modulate phrenic motor output.
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Affiliation(s)
- Michael D Sunshine
- Rehabilitation Medicine, University of Washington, Seattle, WA, United States; Center for Sensorimotor Neural Engineering (CSNE), Seattle, WA, United States; Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL, United States.
| | - Comron N Ganji
- Rehabilitation Medicine, University of Washington, Seattle, WA, United States; Center for Sensorimotor Neural Engineering (CSNE), Seattle, WA, United States
| | - Paul J Reier
- Neuroscience, University of Florida, Gainesville, FL, United States
| | - David D Fuller
- Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL, United States; Center for Respiratory Research and Rehabilitation, University of Florida, Gainesville, FL, United States
| | - Chet T Moritz
- Rehabilitation Medicine, University of Washington, Seattle, WA, United States; Center for Sensorimotor Neural Engineering (CSNE), Seattle, WA, United States; Physiology & Biophysics, University of Washington, Seattle, WA, United States; University of Washington Institute for Neuroengineering (UWIN), University of Washington, Seattle, WA, United States
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17
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Ghali MGZ. Microsurgical technique for tracheostomy in the rat. MethodsX 2017; 5:61-67. [PMID: 29511643 PMCID: PMC5832670 DOI: 10.1016/j.mex.2017.10.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2017] [Accepted: 10/24/2017] [Indexed: 11/30/2022] Open
Abstract
Tracheostomy is used to obtain airway access to allow for mechanical ventilation in experimental animal models. We present a microsurgical atlas of our technique for tracheostomy in the adult rat.
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18
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Ghali MGZ. Microsurgical technique for femoral vascular access in the rat. MethodsX 2017; 4:498-507. [PMID: 29872639 PMCID: PMC5986974 DOI: 10.1016/j.mex.2017.11.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2017] [Accepted: 11/06/2017] [Indexed: 11/25/2022] Open
Abstract
Vascular access is used experimentally for a variety of reasons. In our lab, we achieve arterial access to record arterial pressure and venous access to administer fluids and drugs. We present a microsurgical atlas of our technique for femoral arterial and venous access in the rat.
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Affiliation(s)
- Michael George Zaki Ghali
- Department of Neurobiology & Anatomy, Drexel University College of Medicine, 2900 Queen Lane, Philadelphia, PA, 19129, USA
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19
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Zholudeva LV, Karliner JS, Dougherty KJ, Lane MA. Anatomical Recruitment of Spinal V2a Interneurons into Phrenic Motor Circuitry after High Cervical Spinal Cord Injury. J Neurotrauma 2017; 34:3058-3065. [PMID: 28548606 DOI: 10.1089/neu.2017.5045] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
More than half of all spinal cord injuries (SCIs) occur at the cervical level, often resulting in impaired respiration. Despite this devastating outcome, there is substantial evidence for endogenous neuroplasticity after cervical SCI. Spinal interneurons are widely recognized as being an essential anatomical component of this plasticity by contributing to novel neuronal pathways that can result in functional improvement. The identity of spinal interneurons involved with respiratory plasticity post-SCI, however, has remained largely unknown. Using a transgenic Chx10-eGFP mouse line (Strain 011391-UCD), the present study is the first to demonstrate the recruitment of excitatory interneurons into injured phrenic circuitry after a high cervical SCI. Diaphragm electromyography and anatomical analysis were used to confirm lesion-induced functional deficits and document extent of the lesion, respectively. Transneuronal tracing with pseudorabies virus (PRV) was used to identify interneurons within the phrenic circuitry. There was a robust increase in the number of PRV-labeled V2a interneurons ipsilateral to the C2 hemisection, demonstrating that significant numbers of these excitatory spinal interneurons were anatomically recruited into the phrenic motor pathway two weeks after injury, a time known to correspond with functional phrenic plasticity. Understanding this anatomical spinal plasticity and the neural substrates associated with functional compensation or recovery post-SCI in a controlled, experimental setting may help shed light onto possible cellular therapeutic candidates that can be targeted to enhance spontaneous recovery.
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Affiliation(s)
- Lyandysha V Zholudeva
- 1 Department of Neurobiology and Anatomy, College of Medicine, Drexel University , Philadelphia, Pennsylvania.,2 The Spinal Cord Research Center, College of Medicine, Drexel University , Philadelphia, Pennsylvania
| | - Jordyn S Karliner
- 1 Department of Neurobiology and Anatomy, College of Medicine, Drexel University , Philadelphia, Pennsylvania.,2 The Spinal Cord Research Center, College of Medicine, Drexel University , Philadelphia, Pennsylvania.,3 Department of Neuroscience, Ursinus College , Collegeville, Pennsylvania
| | - Kimberly J Dougherty
- 1 Department of Neurobiology and Anatomy, College of Medicine, Drexel University , Philadelphia, Pennsylvania.,2 The Spinal Cord Research Center, College of Medicine, Drexel University , Philadelphia, Pennsylvania
| | - Michael A Lane
- 1 Department of Neurobiology and Anatomy, College of Medicine, Drexel University , Philadelphia, Pennsylvania.,2 The Spinal Cord Research Center, College of Medicine, Drexel University , Philadelphia, Pennsylvania
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20
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Gonzalez-Rothi EJ, Streeter KA, Hanna MH, Stamas AC, Reier PJ, Baekey DM, Fuller DD. High-frequency epidural stimulation across the respiratory cycle evokes phrenic short-term potentiation after incomplete cervical spinal cord injury. J Neurophysiol 2017; 118:2344-2357. [PMID: 28615341 DOI: 10.1152/jn.00913.2016] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 06/13/2017] [Accepted: 06/14/2017] [Indexed: 01/15/2023] Open
Abstract
C2 spinal hemilesion (C2Hx) paralyzes the ipsilateral diaphragm, but recovery is possible through activation of "crossed spinal" synaptic inputs to ipsilateral phrenic motoneurons. We tested the hypothesis that high-frequency epidural stimulation (HF-ES) would potentiate ipsilateral phrenic output after subacute and chronic C2Hx. HF-ES (300 Hz) was applied to the ventrolateral C4 or T2 spinal cord ipsilateral to C2Hx in anesthetized and mechanically ventilated adult rats. Stimulus duration was 60 s, and currents ranged from 100 to 1,000 µA. Bilateral phrenic nerve activity and ipsilateral hypoglossal (XII) nerve activity were recorded before and after HF-ES. Higher T2 stimulus currents potentiated ipsilateral phasic inspiratory activity at both 2 and 12 wk post-C2Hx, whereas higher stimulus currents delivered at C4 potentiated ipsilateral phasic phrenic activity only at 12 wk (P = 0.028). Meanwhile, tonic output in the ipsilateral phrenic nerve reached 500% of baseline values at the high currents with no difference between 2 and 12 wk. HF-ES did not trigger inspiratory burst-frequency changes. Similar responses occurred following T2 HF-ES. Increases in contralateral phrenic and XII nerve output were induced by C4 and T2 HF-ES at higher currents, but the relative magnitude of these changes was small compared with the ipsilateral phrenic response. We conclude that following incomplete cervical spinal cord injury, HF-ES of the ventrolateral midcervical or thoracic spinal cord can potentiate efferent phrenic motor output with little impact on inspiratory burst frequency. However, the substantial increases in tonic output indicate that the uninterrupted 60-s stimulation paradigm used is unlikely to be useful for respiratory muscle activation after spinal injury.NEW & NOTEWORTHY Previous studies reported that high-frequency epidural stimulation (HF-ES) activates the diaphragm following acute spinal transection. This study examined HF-ES and phrenic motor output following subacute and chronic incomplete cervical spinal cord injury. Short-term potentiation of phrenic bursting following HF-ES illustrates the potential for spinal stimulation to induce respiratory neuroplasticity. Increased tonic phrenic output indicates that alternatives to the continuous stimulation paradigm used in this study will be required for respiratory muscle activation after spinal cord injury.
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Affiliation(s)
- Elisa J Gonzalez-Rothi
- McKnight Brain Institute, Department of Physical Therapy, College of Public Health and Health Professions, University of Florida, Gainesville, Florida;
| | - Kristi A Streeter
- McKnight Brain Institute, Department of Physical Therapy, College of Public Health and Health Professions, University of Florida, Gainesville, Florida
| | - Marie H Hanna
- McKnight Brain Institute, Department of Physical Therapy, College of Public Health and Health Professions, University of Florida, Gainesville, Florida
| | - Anna C Stamas
- McKnight Brain Institute, Department of Physical Therapy, College of Public Health and Health Professions, University of Florida, Gainesville, Florida
| | - Paul J Reier
- Department of Neuroscience, College of Medicine, University of Florida, Gainesville, Florida; and
| | - David M Baekey
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida
| | - David D Fuller
- McKnight Brain Institute, Department of Physical Therapy, College of Public Health and Health Professions, University of Florida, Gainesville, Florida
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Ghali MGZ. The bulbospinal network controlling the phrenic motor system: Laterality and course of descending projections. Neurosci Res 2017; 121:7-17. [PMID: 28389264 DOI: 10.1016/j.neures.2017.03.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Accepted: 03/06/2017] [Indexed: 11/17/2022]
Abstract
The respiratory rhythm is generated by the parafacial respiratory group, Bötzinger complex, and pre-Bötzinger complex and relayed to pre-motor neurons, which in turn project to and control respiratory motor outputs in the brainstem and spinal cord. The phrenic nucleus is one such target, containing phrenic motoneurons (PhMNs), which supply the diaphragm, the primary inspiratory muscle in mammals. While some investigators have demonstrated both ipsi- and contralateral bulbophrenic projections, there exists controversy regarding the relative physiological contribution of each to phasic and tonic drive to PhMNs and at which levels decussations occur. Following C1- or C2 spinal cord hemisection-induced silencing of the ipsilateral phrenic/diaphragm activity, respiratory stressor-induced, as well as spontaneous, recovery of crossed phrenic activity is observed, suggesting an important contribution of pathways crossing below the level of injury in driving phrenic motor output. The precise mechanisms underlying this recovery are debated. In this review, we seek to present a comprehensive discussion of the organization of the bulbospinal network controlling PhMNs, a thorough appreciation of which is necessary for understanding neural respiratory control, accurate interpretation of studies investigating respiratory recovery following spinal cord injury, and targeted development of therapies for respiratory neurorehabilitation in patients sustaining high cervical cord injury.
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Affiliation(s)
- Michael George Zaki Ghali
- Department of Neurobiology & Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, USA.
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22
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Hormigo KM, Zholudeva LV, Spruance VM, Marchenko V, Cote MP, Vinit S, Giszter S, Bezdudnaya T, Lane MA. Enhancing neural activity to drive respiratory plasticity following cervical spinal cord injury. Exp Neurol 2017; 287:276-287. [PMID: 27582085 PMCID: PMC5121051 DOI: 10.1016/j.expneurol.2016.08.018] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 07/20/2016] [Accepted: 08/26/2016] [Indexed: 02/07/2023]
Abstract
Cervical spinal cord injury (SCI) results in permanent life-altering sensorimotor deficits, among which impaired breathing is one of the most devastating and life-threatening. While clinical and experimental research has revealed that some spontaneous respiratory improvement (functional plasticity) can occur post-SCI, the extent of the recovery is limited and significant deficits persist. Thus, increasing effort is being made to develop therapies that harness and enhance this neuroplastic potential to optimize long-term recovery of breathing in injured individuals. One strategy with demonstrated therapeutic potential is the use of treatments that increase neural and muscular activity (e.g. locomotor training, neural and muscular stimulation) and promote plasticity. With a focus on respiratory function post-SCI, this review will discuss advances in the use of neural interfacing strategies and activity-based treatments, and highlights some recent results from our own research.
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Affiliation(s)
- Kristiina M Hormigo
- Spinal Cord Research Center, Department of Neurobiology and Anatomy, College of Medicine, Drexel University, 2900 W Queen Lane, Philadelphia, PA, USA
| | - Lyandysha V Zholudeva
- Spinal Cord Research Center, Department of Neurobiology and Anatomy, College of Medicine, Drexel University, 2900 W Queen Lane, Philadelphia, PA, USA
| | - Victoria M Spruance
- Spinal Cord Research Center, Department of Neurobiology and Anatomy, College of Medicine, Drexel University, 2900 W Queen Lane, Philadelphia, PA, USA
| | - Vitaliy Marchenko
- Spinal Cord Research Center, Department of Neurobiology and Anatomy, College of Medicine, Drexel University, 2900 W Queen Lane, Philadelphia, PA, USA
| | - Marie-Pascale Cote
- Spinal Cord Research Center, Department of Neurobiology and Anatomy, College of Medicine, Drexel University, 2900 W Queen Lane, Philadelphia, PA, USA
| | - Stephane Vinit
- Université de Versailles Saint-Quentin-en-Yvelines, INSERM U1179 End:icap, UFR des Sciences de la Santé - Simone Veil, Montigny-le-Bretonneux, France
| | - Simon Giszter
- Spinal Cord Research Center, Department of Neurobiology and Anatomy, College of Medicine, Drexel University, 2900 W Queen Lane, Philadelphia, PA, USA
| | - Tatiana Bezdudnaya
- Spinal Cord Research Center, Department of Neurobiology and Anatomy, College of Medicine, Drexel University, 2900 W Queen Lane, Philadelphia, PA, USA
| | - Michael A Lane
- Spinal Cord Research Center, Department of Neurobiology and Anatomy, College of Medicine, Drexel University, 2900 W Queen Lane, Philadelphia, PA, USA.
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23
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Respiratory neuroplasticity – Overview, significance and future directions. Exp Neurol 2017; 287:144-152. [DOI: 10.1016/j.expneurol.2016.05.022] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2016] [Accepted: 05/17/2016] [Indexed: 01/10/2023]
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Abstract
The cervical spine is the most common site of traumatic vertebral column injuries. Respiratory insufficiency constitutes a significant proportion of the morbidity burden and is the most common cause of mortality in these patients. In seeking to enhance our capacity to treat specifically the respiratory dysfunction following spinal cord injury, investigators have studied the "crossed phrenic phenomenon", wherein contraction of a hemidiaphragm paralyzed by a complete hemisection of the ipsilateral cervical spinal cord above the phrenic nucleus can be induced by respiratory stressors and recovers spontaneously over time. Strengthening of latent contralateral projections to the phrenic nucleus and sprouting of new descending axons have been proposed as mechanisms contributing to the observed recovery. We have recently demonstrated recovery of spontaneous crossed phrenic activity occurring over minutes to hours in C1-hemisected unanesthetized decerebrate rats. The specific neurochemical and molecular pathways underlying crossed phrenic activity following injury require further clarification. A thorough understanding of these is necessary in order to develop targeted therapies for respiratory neurorehabilitation following spinal trauma. Animal studies provide preliminary evidence for the utility of neuropharmacological manipulation of serotonergic and adenosinergic pathways, nerve grafts, olfactory ensheathing cells, intraspinal microstimulation and a possible role for dorsal rhizotomy in recovering phrenic activity following spinal cord injury.
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Streeter KA, Sunshine MD, Patel SR, Liddell SS, Denholtz LE, Reier PJ, Fuller DD, Baekey DM. Coupling multielectrode array recordings with silver labeling of recording sites to study cervical spinal network connectivity. J Neurophysiol 2016; 117:1014-1029. [PMID: 27974450 DOI: 10.1152/jn.00638.2016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Accepted: 12/12/2016] [Indexed: 01/24/2023] Open
Abstract
Midcervical spinal interneurons form a complex and diffuse network and may be involved in modulating phrenic motor output. The intent of the current work was to enable a better understanding of midcervical "network-level" connectivity by pairing the neurophysiological multielectrode array (MEA) data with histological verification of the recording locations. We first developed a method to deliver 100-nA currents to electroplate silver onto and subsequently deposit silver from electrode tips after obtaining midcervical (C3-C5) recordings using an MEA in anesthetized and ventilated adult rats. Spinal tissue was then fixed, harvested, and histologically processed to "develop" the deposited silver. Histological studies verified that the silver deposition method discretely labeled (50-μm resolution) spinal recording locations between laminae IV and X in cervical segments C3-C5. Using correlative techniques, we next tested the hypothesis that midcervical neuronal discharge patterns are temporally linked. Cross-correlation histograms produced few positive peaks (5.3%) in the range of 0-0.4 ms, but 21.4% of neuronal pairs had correlogram peaks with a lag of ≥0.6 ms. These results are consistent with synchronous discharge involving mono- and polysynaptic connections among midcervical neurons. We conclude that there is a high degree of synaptic connectivity in the midcervical spinal cord and that the silver-labeling method can reliably mark metal electrode recording sites and "map" interneuron populations, thereby providing a low-cost and effective tool for use in MEA experiments. We suggest that this method will be useful for further exploration of midcervical network connectivity.NEW & NOTEWORTHY We describe a method that reliably identifies the locations of multielectrode array (MEA) recording sites while preserving the surrounding tissue for immunohistochemistry. To our knowledge, this is the first cost-effective method to identify the anatomic locations of neuronal ensembles recorded with a MEA during acute preparations without the requirement of specialized array electrodes. In addition, evaluation of activity recorded from silver-labeled sites revealed a previously unappreciated degree of connectivity between midcervical interneurons.
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Affiliation(s)
- K A Streeter
- Department of Physical Therapy, University of Florida, Gainesville, Florida
| | - M D Sunshine
- Department of Physical Therapy, University of Florida, Gainesville, Florida
| | - S R Patel
- Department of Physical Therapy, University of Florida, Gainesville, Florida
| | - S S Liddell
- Department of Neuroscience, University of Florida, Gainesville, Florida; and
| | - L E Denholtz
- Department of Neuroscience, University of Florida, Gainesville, Florida; and
| | - P J Reier
- Department of Neuroscience, University of Florida, Gainesville, Florida; and
| | - D D Fuller
- Department of Physical Therapy, University of Florida, Gainesville, Florida
| | - D M Baekey
- Department of Physiological Sciences, University of Florida, Gainesville, Florida
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Ghali MGZ, Marchenko V. Patterns of Phrenic Nerve Discharge after Complete High Cervical Spinal Cord Injury in the Decerebrate Rat. J Neurotrauma 2016; 33:1115-27. [DOI: 10.1089/neu.2015.4034] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Michael George Zaki Ghali
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania
| | - Vitaliy Marchenko
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania
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