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Sun C, Deng J, Ma Y, Meng F, Cui X, Li M, Li J, Li J, Yin P, Kong L, Zhang L, Tang P. The dual role of microglia in neuropathic pain after spinal cord injury: Detrimental and protective effects. Exp Neurol 2023; 370:114570. [PMID: 37852469 DOI: 10.1016/j.expneurol.2023.114570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Revised: 09/21/2023] [Accepted: 10/11/2023] [Indexed: 10/20/2023]
Abstract
Spinal cord injury (SCI) is a debilitating condition that is frequently accompanied by neuropathic pain, resulting in significant physical and psychological harm to a vast number of individuals globally. Despite the high prevalence of neuropathic pain following SCI, the precise underlying mechanism remains incompletely understood. Microglia are a type of innate immune cell that are present in the central nervous system (CNS). They have been observed to have a significant impact on neuropathic pain following SCI. This article presents a comprehensive overview of recent advances in understanding the role of microglia in the development of neuropathic pain following SCI. Specifically, the article delves into the detrimental and protective effects of microglia on neuropathic pain following SCI, as well as the mechanisms underlying their interconversion. Furthermore, the article provides a thorough overview of potential avenues for future research in this area.
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Affiliation(s)
- Chang Sun
- Department of Orthopedics, The Fourth Medical Center of Chinese PLA General Hospital, Beijing, China; National Clinical Research Center for Orthopedics, Sports Medicine and Rehabilitation, Beijing, China; Department of Orthopedics, Air Force Medical Center, PLA, Beijing, China
| | - Junhao Deng
- Department of Orthopedics, The Fourth Medical Center of Chinese PLA General Hospital, Beijing, China; National Clinical Research Center for Orthopedics, Sports Medicine and Rehabilitation, Beijing, China; School of Life Sciences, Tsinghua University, Beijing, China; State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instruments, Tsinghua University, Beijing, China; IDG/McGovern Institute for Brain Research, Tsinghua University, Beijing, China
| | - Yifei Ma
- School of Medicine, Nankai University, Tianjin, China
| | - Fanqi Meng
- Department of Anesthesiology, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Xiang Cui
- Department of Orthopedics, The Fourth Medical Center of Chinese PLA General Hospital, Beijing, China; National Clinical Research Center for Orthopedics, Sports Medicine and Rehabilitation, Beijing, China
| | - Ming Li
- Department of Orthopedics, The Fourth Medical Center of Chinese PLA General Hospital, Beijing, China; National Clinical Research Center for Orthopedics, Sports Medicine and Rehabilitation, Beijing, China
| | - Jiantao Li
- Department of Orthopedics, The Fourth Medical Center of Chinese PLA General Hospital, Beijing, China; National Clinical Research Center for Orthopedics, Sports Medicine and Rehabilitation, Beijing, China
| | - Jia Li
- Department of Orthopedics, The Fourth Medical Center of Chinese PLA General Hospital, Beijing, China; National Clinical Research Center for Orthopedics, Sports Medicine and Rehabilitation, Beijing, China
| | - Pengbin Yin
- Department of Orthopedics, The Fourth Medical Center of Chinese PLA General Hospital, Beijing, China; National Clinical Research Center for Orthopedics, Sports Medicine and Rehabilitation, Beijing, China
| | - Lingjie Kong
- State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instruments, Tsinghua University, Beijing, China; IDG/McGovern Institute for Brain Research, Tsinghua University, Beijing, China.
| | - Licheng Zhang
- Department of Orthopedics, The Fourth Medical Center of Chinese PLA General Hospital, Beijing, China; National Clinical Research Center for Orthopedics, Sports Medicine and Rehabilitation, Beijing, China.
| | - Peifu Tang
- Department of Orthopedics, The Fourth Medical Center of Chinese PLA General Hospital, Beijing, China; National Clinical Research Center for Orthopedics, Sports Medicine and Rehabilitation, Beijing, China.
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Omondi C, Chou A, Fond KA, Morioka K, Joseph NR, Sacramento JA, Iorio E, Torres-Espin A, Radabaugh HL, Davis JA, Gumbel JH, Russell Huie J, Ferguson AR. Improving rigor and reproducibility in western blot experiments with the blotRig analysis software. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.02.551674. [PMID: 37577570 PMCID: PMC10418285 DOI: 10.1101/2023.08.02.551674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
Western blot is a popular biomolecular analysis method for measuring the relative quantities of independent proteins in complex biological samples. However, variability in quantitative western blot data analysis poses a challenge in designing reproducible experiments. The lack of rigorous quantitative approaches in current western blot statistical methodology may result in irreproducible inferences. Here we describe best practices for the design and analysis of western blot experiments, with examples and demonstrations of how different analytical approaches can lead to widely varying outcomes. To facilitate best practices, we have developed the blotRig tool for designing and analyzing western blot experiments to improve their rigor and reproducibility. The blotRig application includes functions for counterbalancing experimental design by lane position, batch management across gels, and analytics with covariates and random effects.
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Affiliation(s)
- Cleopa Omondi
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA USA
| | - Austin Chou
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA USA
| | - Kenneth A. Fond
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA USA
| | - Kazuhito Morioka
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA USA
| | - Nadine R. Joseph
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA USA
| | - Jeffrey A. Sacramento
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA USA
| | - Emma Iorio
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA USA
| | - Abel Torres-Espin
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA USA
- School of Public Health Sciences, Faculty of Health Sciences, University of Waterloo, ON, Canada
- Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta, AB, Canada
| | - Hannah L. Radabaugh
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA USA
| | - Jacob A. Davis
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA USA
| | - Jason H. Gumbel
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA USA
| | - J. Russell Huie
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA USA
- San Francisco Veterans Affairs Medical Center, San Francisco, San Francisco, CA USA
| | - Adam R. Ferguson
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA USA
- San Francisco Veterans Affairs Medical Center, San Francisco, San Francisco, CA USA
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Kumari R, Gibson H, Jarjees M, Turner C, Purcell M, Vučković A. The predictive value of cortical activity during motor imagery for subacute spinal cord injury-induced neuropathic pain. Clin Neurophysiol 2023; 148:32-43. [PMID: 36796284 DOI: 10.1016/j.clinph.2023.01.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Revised: 12/06/2022] [Accepted: 01/04/2023] [Indexed: 01/26/2023]
Abstract
OBJECTIVE The aim of this study is to explore whether cortical activation and its lateralization during motor imagery (MI) in subacute spinal cord injury (SCI) are indicative of existing or upcoming central neuropathic pain (CNP). METHODS Multichannel electroencephalogram was recorded during MI of both hands in four groups of participants: able-bodied (N = 10), SCI and CNP (N = 11), SCI who developed CNP within 6 months of EEG recording (N = 10), and SCI who remained CNP-free (N = 10). Source activations and its lateralization were derived in four frequency bands in 20 regions spanning sensorimotor cortex and pain matrix. RESULTS Statistically significant differences in lateralization were found in the theta band in premotor cortex (upcoming vs existing CNP, p = 0.036), in the alpha band at the insula (healthy vs upcoming CNP, p = 0.012), and in the higher beta band at the somatosensory association cortex (no CNP vs upcoming CNP, p = 0.042). People with upcoming CNP had stronger activation compared to those with no CNP in the higher beta band for MI of both hands. CONCLUSIONS Activation intensity and lateralization during MI in pain-related areas might hold a predictive value for CNP. SIGNIFICANCE The study increases understanding of the mechanisms underlying transition from asymptomatic to symptomatic early CNP in SCI.
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Affiliation(s)
- Radha Kumari
- Biomedical Engineering Research Division, University of Glasgow, Glasgow G12 8QQ, UK
| | - Hannah Gibson
- Biomedical Engineering Research Division, University of Glasgow, Glasgow G12 8QQ, UK
| | - Mohammed Jarjees
- Biomedical Engineering Research Division, University of Glasgow, Glasgow G12 8QQ, UK; Medical Instrumentation Techniques Engineering Department, Northern Technical University, Mosul 41002, Iraq
| | - Christopher Turner
- Biomedical Engineering Research Division, University of Glasgow, Glasgow G12 8QQ, UK
| | - Mariel Purcell
- Queen Elizabeth National Spinal Injuries Unit, Queen Elizabeth University Hospital, Glasgow G51 4TF, UK
| | - Aleksandra Vučković
- Biomedical Engineering Research Division, University of Glasgow, Glasgow G12 8QQ, UK.
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Grau JW, Hudson KE, Tarbet MM, Strain MM. Behavioral studies of spinal conditioning: The spinal cord is smarter than you think it is. JOURNAL OF EXPERIMENTAL PSYCHOLOGY. ANIMAL LEARNING AND COGNITION 2022; 48:435-457. [PMID: 35901417 PMCID: PMC10391333 DOI: 10.1037/xan0000332] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In 1988 Robert Rescorla published an article in the Annual Review of Neuroscience that addressed the circumstances under which learning occurs, some key methodological issues, and what constitutes an example of learning. The article has inspired a generation of neuroscientists, opening the door to a wider range of learning phenomena. After reviewing the historical context for his article, its key points are briefly reviewed. The perspective outlined enabled the study of learning in simpler preparations, such as the spinal cord. The period after 1988 revealed that pain (nociceptive) stimuli can induce a lasting sensitization of spinal cord circuits, laying down a kind of memory mediated by signal pathways analogous to those implicated in brain dependent learning and memory. Evidence suggests that the spinal cord is sensitive to instrumental response-outcome (R-O) relations, that learning can induce a peripheral modification (muscle memory) that helps maintain the learned response, and that learning can promote adaptive plasticity (a form of metaplasticity). Conversely, exposure to uncontrollable stimulation disables the capacity to learn. Spinal cord neurons can also abstract that stimuli occur in a regular (predictable) manner, a capacity that appears linked to a neural oscillator (central pattern generator). Disrupting communication with the brain has been shown to transform how GABA affects neuronal function (an example of ionic plasticity), releasing a brake that enables plasticity. We conclude by presenting a framework for understanding these findings and the implications for the broader study of learning. (PsycInfo Database Record (c) 2022 APA, all rights reserved).
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Affiliation(s)
- James W. Grau
- Cellular and Behavioral Neuroscience, Department of Psychology, Texas A&M University, College Station, TX, 77843 USA
| | - Kelsey E. Hudson
- Cellular and Behavioral Neuroscience, Department of Psychology, Texas A&M University, College Station, TX, 77843 USA
| | - Megan M. Tarbet
- McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX
| | - Misty M. Strain
- Department of Cellular and Integrative Physiology, University of Texas Health San Antonio, San Antonio, TX 78229
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Hudson KE, Grau JW. Ionic Plasticity: Common Mechanistic Underpinnings of Pathology in Spinal Cord Injury and the Brain. Cells 2022; 11:cells11182910. [PMID: 36139484 PMCID: PMC9496934 DOI: 10.3390/cells11182910] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 09/12/2022] [Accepted: 09/14/2022] [Indexed: 11/16/2022] Open
Abstract
The neurotransmitter GABA is normally characterized as having an inhibitory effect on neural activity in the adult central nervous system (CNS), which quells over-excitation and limits neural plasticity. Spinal cord injury (SCI) can bring about a modification that weakens the inhibitory effect of GABA in the central gray caudal to injury. This change is linked to the downregulation of the potassium/chloride cotransporter (KCC2) and the consequent rise in intracellular Cl- in the postsynaptic neuron. As the intracellular concentration increases, the inward flow of Cl- through an ionotropic GABA-A receptor is reduced, which decreases its hyperpolarizing (inhibitory) effect, a modulatory effect known as ionic plasticity. The loss of GABA-dependent inhibition enables a state of over-excitation within the spinal cord that fosters aberrant motor activity (spasticity) and chronic pain. A downregulation of KCC2 also contributes to the development of a number of brain-dependent pathologies linked to states of neural over-excitation, including epilepsy, addiction, and developmental disorders, along with other diseases such as hypertension, asthma, and irritable bowel syndrome. Pharmacological treatments that target ionic plasticity have been shown to bring therapeutic benefits.
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Affiliation(s)
- Kelsey E. Hudson
- Neuroscience, Texas A&M University, College Station, TX 77843, USA
- Correspondence:
| | - James W. Grau
- Psychological & Brain Sciences, Texas A&M University, College Station, TX 77843, USA
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Fauss GNK, Hudson KE, Grau JW. Role of Descending Serotonergic Fibers in the Development of Pathophysiology after Spinal Cord Injury (SCI): Contribution to Chronic Pain, Spasticity, and Autonomic Dysreflexia. BIOLOGY 2022; 11:234. [PMID: 35205100 PMCID: PMC8869318 DOI: 10.3390/biology11020234] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 01/27/2022] [Accepted: 01/29/2022] [Indexed: 12/12/2022]
Abstract
As the nervous system develops, nerve fibers from the brain form descending tracts that regulate the execution of motor behavior within the spinal cord, incoming sensory signals, and capacity to change (plasticity). How these fibers affect function depends upon the transmitter released, the receptor system engaged, and the pattern of neural innervation. The current review focuses upon the neurotransmitter serotonin (5-HT) and its capacity to dampen (inhibit) neural excitation. A brief review of key anatomical details, receptor types, and pharmacology is provided. The paper then considers how damage to descending serotonergic fibers contributes to pathophysiology after spinal cord injury (SCI). The loss of serotonergic fibers removes an inhibitory brake that enables plasticity and neural excitation. In this state, noxious stimulation can induce a form of over-excitation that sensitizes pain (nociceptive) circuits, a modification that can contribute to the development of chronic pain. Over time, the loss of serotonergic fibers allows prolonged motor drive (spasticity) to develop and removes a regulatory brake on autonomic function, which enables bouts of unregulated sympathetic activity (autonomic dysreflexia). Recent research has shown that the loss of descending serotonergic activity is accompanied by a shift in how the neurotransmitter GABA affects neural activity, reducing its inhibitory effect. Treatments that target the loss of inhibition could have therapeutic benefit.
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Affiliation(s)
| | | | - James W. Grau
- Department of Psychological and Brain Sciences, Texas A&M University, College Station, TX 77843, USA; (G.N.K.F.); (K.E.H.)
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Hoy KC, Strain MM, Turtle JD, Lee KH, Huie JR, Hartman JJ, Tarbet MM, Harlow ML, Magnuson DSK, Grau JW. Evidence That the Central Nervous System Can Induce a Modification at the Neuromuscular Junction That Contributes to the Maintenance of a Behavioral Response. J Neurosci 2020; 40:9186-9209. [PMID: 33097637 PMCID: PMC7687054 DOI: 10.1523/jneurosci.2683-19.2020] [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: 11/12/2019] [Revised: 10/13/2020] [Accepted: 10/14/2020] [Indexed: 11/21/2022] Open
Abstract
Neurons within the spinal cord are sensitive to environmental relations and can bring about a behavioral modification without input from the brain. For example, rats that have undergone a thoracic (T2) transection can learn to maintain a hind leg in a flexed position to minimize exposure to a noxious electrical stimulation (shock). Inactivating neurons within the spinal cord with lidocaine, or cutting communication between the spinal cord and the periphery (sciatic transection), eliminates the capacity to learn, which implies that it depends on spinal neurons. Here we show that these manipulations have no effect on the maintenance of the learned response, which implicates a peripheral process. EMG showed that learning augments the muscular response evoked by motoneuron output and that this effect survives a sciatic transection. Quantitative fluorescent imaging revealed that training brings about an increase in the area and intensity of ACh receptor labeling at the neuromuscular junction (NMJ). It is hypothesized that efferent motoneuron output, in conjunction with electrical stimulation of the tibialis anterior muscle, strengthens the connection at the NMJ in a Hebbian manner. Supporting this, paired stimulation of the efferent nerve and tibialis anterior generated an increase in flexion duration and augmented the evoked electrical response without input from the spinal cord. Evidence is presented that glutamatergic signaling contributes to plasticity at the NMJ. Labeling for vesicular glutamate transporter is evident at the motor endplate. Intramuscular application of an NMDAR antagonist blocked the acquisition/maintenance of the learned response and the strengthening of the evoked electrical response.SIGNIFICANCE STATEMENT The neuromuscular junction (NMJ) is designed to faithfully elicit a muscular contraction in response to neural input. From this perspective, encoding environmental relations (learning) and the maintenance of a behavioral modification over time (memory) are assumed to reflect only modifications upstream from the NMJ, within the CNS. The current results challenge this view. Rats were trained to maintain a hind leg in a flexed position to avoid noxious stimulation. As expected, treatments that inhibit activity within the CNS, or disrupt peripheral communication, prevented learning. These manipulations did not affect the maintenance of the acquired response. The results imply that a peripheral modification at the NMJ contributes to the maintenance of the learned response.
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Affiliation(s)
- Kevin C Hoy
- Case Comprehensive Cancer Center/Case Western Reserve School of Medicine, Cleveland, Ohio 44106
| | - Misty M Strain
- U.S. Army Institute of Surgical Research, JBSA Fort Sam Houston, Houston, Texas 78234
| | - Joel D Turtle
- Department of Psychological and Brain Sciences, Texas A&M University, College Station, Texas 77843
| | - Kuan H Lee
- Department of Psychological and Brain Sciences, Texas A&M University, College Station, Texas 77843
| | - J Russell Huie
- Department of Neuroscience, University of California San Francisco, San Francisco, California 94110
| | - John J Hartman
- Department of Psychological and Brain Sciences, Texas A&M University, College Station, Texas 77843
| | - Megan M Tarbet
- Department of Psychological and Brain Sciences, Texas A&M University, College Station, Texas 77843
| | - Mark L Harlow
- Department of Biology, Texas A&M University, College Station, Texas 77843
| | - David S K Magnuson
- Department of Neurological Surgery, University of Louisville, Louisville, Kentucky 40202
| | - James W Grau
- Department of Psychological and Brain Sciences, Texas A&M University, College Station, Texas 77843
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Brumley MR, Strain MM, Devine N, Bozeman AL. The Spinal Cord, Not to Be Forgotten: the Final Common Path for Development, Training and Recovery of Motor Function. Perspect Behav Sci 2018; 41:369-393. [PMID: 31976401 DOI: 10.1007/s40614-018-00177-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Research on learning, memory, and neural plasticity has long focused on the brain. However, the spinal cord also exhibits these phenomena to a remarkable degree. Following a spinal cord injury, the isolated spinal cord in vivo can adapt to the environment and benefit from training. The amount of plasticity or recovery of function following a spinal injury often depends on the age at which the injury occurs. In this overview, we discuss learning in the spinal cord, including associative conditioning, neural mechanisms, development, and applications to clinical populations. We take an integrated approach to the spinal cord, one that combines basic and experimental information about experience-dependent learning in animal models to clinical treatment of spinal cord injuries in humans. From such an approach, an important goal is to better inform therapeutic treatments for individuals with spinal cord injuries, as well as develop a more accurate and complete account of spinal cord and behavioral functioning.
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Affiliation(s)
- Michele R Brumley
- 1Department of Psychology, Idaho State University, 921 South 8th Avenue, Stop 8112, Pocatello, ID 83209-8112 USA
| | - Misty M Strain
- 2United States Army Institute of Surgical Research, JBSA-Fort Sam Houston, San Antonio, TX USA
| | - Nancy Devine
- 3Department of Physical and Occupational Therapy, Idaho State University, Pocatello, ID USA
| | - Aimee L Bozeman
- 1Department of Psychology, Idaho State University, 921 South 8th Avenue, Stop 8112, Pocatello, ID 83209-8112 USA
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Grau JW, Huang YJ. Metaplasticity within the spinal cord: Evidence brain-derived neurotrophic factor (BDNF), tumor necrosis factor (TNF), and alterations in GABA function (ionic plasticity) modulate pain and the capacity to learn. Neurobiol Learn Mem 2018; 154:121-135. [PMID: 29635030 DOI: 10.1016/j.nlm.2018.04.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Revised: 03/01/2018] [Accepted: 04/06/2018] [Indexed: 12/15/2022]
Abstract
Evidence is reviewed that behavioral training and neural injury can engage metaplastic processes that regulate adaptive potential. This issue is explored within a model system that examines how training affects the capacity to learn within the lower (lumbosacral) spinal cord. Response-contingent (controllable) stimulation applied caudal to a spinal transection induces a behavioral modification indicative of learning. This behavioral change is not observed in animals that receive stimulation in an uncontrollable manner. Exposure to uncontrollable stimulation also engages a process that disables spinal learning for 24-48 h. Controllable stimulation has the opposite effect; it engages a process that enables learning and prevents/reverses the learning deficit induced by uncontrollable stimulation. These observations suggest that a learning episode can impact the capacity to learn in future situations, providing an example of behavioral metaplasticity. The protective/restorative effect of controllable stimulation has been linked to an up-regulation of brain-derived neurotrophic factor (BDNF). The disruption of learning has been linked to the sensitization of pain (nociceptive) circuits, which is enabled by a reduction in GABA-dependent inhibition. After spinal cord injury (SCI), the co-transporter (KCC2) that regulates the outward flow of Cl- is down-regulated. This causes the intracellular concentration of Cl- to increase, reducing (and potentially reversing) the inward flow of Cl- through the GABA-A receptor. The shift in GABA function (ionic plasticity) increases neural excitability caudal to injury and sets the stage for nociceptive sensitization. The injury-induced shift in KCC2 is related to the loss of descending serotonergic (5HT) fibers that regulate plasticity within the spinal cord dorsal horn through the 5HT-1A receptor. Evidence is presented that these alterations in spinal plasticity impact pain in a brain-dependent task (place conditioning). The findings suggest that ionic plasticity can affect learning potential, shifting a neural circuit from dampened/hard-wired to excitable/plastic.
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Affiliation(s)
- James W Grau
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843-4235, USA.
| | - Yung-Jen Huang
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843-4235, USA
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10
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Grau JW, Huang YJ, Turtle JD, Strain MM, Miranda RC, Garraway SM, Hook MA. When Pain Hurts: Nociceptive Stimulation Induces a State of Maladaptive Plasticity and Impairs Recovery after Spinal Cord Injury. J Neurotrauma 2017; 34:1873-1890. [PMID: 27788626 PMCID: PMC5444485 DOI: 10.1089/neu.2016.4626] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Spinal cord injury (SCI) is often accompanied by other tissue damage (polytrauma) that provides a source of pain (nociceptive) input. Recent findings are reviewed that show SCI places the caudal tissue in a vulnerable state that exaggerates the effects nociceptive stimuli and promotes the development of nociceptive sensitization. Stimulation that is both unpredictable and uncontrollable induces a form of maladaptive plasticity that enhances nociceptive sensitization and impairs spinally mediated learning. In contrast, relational learning induces a form of adaptive plasticity that counters these adverse effects. SCI sets the stage for nociceptive sensitization by disrupting serotonergic (5HT) fibers that quell overexcitation. The loss of 5HT can enhance neural excitability by reducing membrane-bound K+-Cl- cotransporter 2, a cotransporter that regulates the outward flow of Cl-. This increases the intracellular concentration of Cl-, which reduces the hyperpolarizing (inhibitory) effect of gamma-aminobutyric acid. Uncontrollable noxious stimulation also undermines the recovery of locomotor function, and increases behavioral signs of chronic pain, after a contusion injury. Nociceptive stimulation has a greater effect if experienced soon after SCI. This adverse effect has been linked to a downregulation in brain-derived neurotrophic factor and an upregulation in the cytokine, tumor necrosis factor. Noxious input enhances tissue loss at the site of injury by increasing the extent of hemorrhage and apoptotic/pyroptotic cell death. Intrathecal lidocaine blocks nociception-induced hemorrhage, cellular indices of cell death, and its adverse effect on behavioral recovery. Clinical implications are discussed.
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Affiliation(s)
- James W. Grau
- Cellular and Behavioral Neuroscience, Department of Psychology, Texas A&M University, College Station, Texas
| | - Yung-Jen Huang
- Cellular and Behavioral Neuroscience, Department of Psychology, Texas A&M University, College Station, Texas
| | - Joel D. Turtle
- Cellular and Behavioral Neuroscience, Department of Psychology, Texas A&M University, College Station, Texas
| | - Misty M. Strain
- Cellular and Behavioral Neuroscience, Department of Psychology, Texas A&M University, College Station, Texas
| | - Rajesh C. Miranda
- Department of Neuroscience and Experimental Therapeutics, Texas A&M Health Science Center, Bryan, Texas
| | - Sandra M. Garraway
- Department of Physiology, Emory University School of Medicine, Atlanta, Georgia
| | - Michelle A. Hook
- Department of Neuroscience and Experimental Therapeutics, Texas A&M Health Science Center, Bryan, Texas
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Huang YJ, Lee KH, Grau JW. Complete spinal cord injury (SCI) transforms how brain derived neurotrophic factor (BDNF) affects nociceptive sensitization. Exp Neurol 2017; 288:38-50. [PMID: 27818188 DOI: 10.1016/j.expneurol.2016.11.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Revised: 10/25/2016] [Accepted: 11/01/2016] [Indexed: 11/17/2022]
Abstract
Noxious stimulation can induce a lasting increase in neural excitability within the spinal cord (central sensitization) that can promote pain and disrupt adaptive function (maladaptive plasticity). Brain-derived neurotrophic factor (BDNF) is known to regulate the development of plasticity and has been shown to impact the development of spinally-mediated central sensitization. The latter effect has been linked to an alteration in GABA-dependent inhibition. Prior studies have shown that, in spinally transected rats, exposure to regular (fixed spaced) stimulation can counter the development of maladaptive plasticity and have linked this effect to an up-regulation of BDNF. Here it is shown that application of the irritant capsaicin to one hind paw induces enhanced mechanical reactivity (EMR) after spinal cord injury (SCI) and that the induction of this effect is blocked by pretreatment with fixed spaced shock. This protective effect was eliminated if rats were pretreated with the BDNF sequestering antibody TrkB-IgG. Intrathecal (i.t.) application of BDNF prevented, but did not reverse, capsaicin-induced EMR. BDNF also attenuated cellular indices (ERK and pERK expression) of central sensitization after SCI. In uninjured rats, i.t. BDNF enhanced, rather than attenuated, capsaicin-induced EMR and ERK/pERK expression. These opposing effects were related to a transformation in GABA function. In uninjured rats, BDNF reduced membrane-bound KCC2 and the inhibitory effect of the GABAA agonist muscimol. After SCI, BDNF increased KCC2 expression, which would help restore GABAergic inhibition. The results suggest that SCI transforms how BDNF affects GABA function and imply that the clinical usefulness of BDNF will depend upon the extent of fiber sparing.
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Affiliation(s)
- Yung-Jen Huang
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843, USA.
| | - Kuan H Lee
- Center for Pain Research, Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - James W Grau
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843, USA
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Huie JR, Morioka K, Haefeli J, Ferguson AR. What Is Being Trained? How Divergent Forms of Plasticity Compete To Shape Locomotor Recovery after Spinal Cord Injury. J Neurotrauma 2017; 34:1831-1840. [PMID: 27875927 DOI: 10.1089/neu.2016.4562] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Spinal cord injury (SCI) is a devastating syndrome that produces dysfunction in motor and sensory systems, manifesting as chronic paralysis, sensory changes, and pain disorders. The multi-faceted and heterogeneous nature of SCI has made effective rehabilitative strategies challenging. Work over the last 40 years has aimed to overcome these obstacles by harnessing the intrinsic plasticity of the spinal cord to improve functional locomotor recovery. Intensive training after SCI facilitates lower extremity function and has shown promise as a tool for retraining the spinal cord by engaging innate locomotor circuitry in the lumbar cord. As new training paradigms evolve, the importance of appropriate afferent input has emerged as a requirement for adaptive plasticity. The integration of kinematic, sensory, and loading force information must be closely monitored and carefully manipulated to optimize training outcomes. Inappropriate peripheral input may produce lasting maladaptive sensory and motor effects, such as central pain and spasticity. Thus, it is important to closely consider the type of afferent input the injured spinal cord receives. Here we review preclinical and clinical input parameters fostering adaptive plasticity, as well as those producing maladaptive plasticity that may undermine neurorehabilitative efforts. We differentiate between passive (hindlimb unloading [HU], limb immobilization) and active (peripheral nociception) forms of aberrant input. Furthermore, we discuss the timing of initiating exposure to afferent input after SCI for promoting functional locomotor recovery. We conclude by presenting a candidate rapid synaptic mechanism for maladaptive plasticity after SCI, offering a pharmacological target for restoring the capacity for adaptive spinal plasticity in real time.
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Affiliation(s)
- J Russell Huie
- 1 Department of Neurological Surgery, Brain and Spinal Injury Center, University of California , San Francisco, California
| | - Kazuhito Morioka
- 1 Department of Neurological Surgery, Brain and Spinal Injury Center, University of California , San Francisco, California
| | - Jenny Haefeli
- 1 Department of Neurological Surgery, Brain and Spinal Injury Center, University of California , San Francisco, California
| | - Adam R Ferguson
- 1 Department of Neurological Surgery, Brain and Spinal Injury Center, University of California , San Francisco, California.,2 San Francisco Veterans Affairs Medical Center , San Francisco, California
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13
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Mercier C, Roosink M, Bouffard J, Bouyer LJ. Promoting Gait Recovery and Limiting Neuropathic Pain After Spinal Cord Injury. Neurorehabil Neural Repair 2016; 31:315-322. [PMID: 27913797 PMCID: PMC5405804 DOI: 10.1177/1545968316680491] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Most persons living with a spinal cord injury experience neuropathic pain in the months following their lesion, at the moment where they receive intensive gait rehabilitation. Based on studies using animal models, it has been proposed that central sensitization in nociceptive pathways (maladaptive plasticity) and plasticity related to motor learning (adaptive plasticity) share common neural mechanisms and compete with each other. This article aims to address the discrepancy between the growing body of basic science literature supporting this hypothesis and the general belief in rehabilitation research that pain and gait rehabilitation represent two independent problems. First, the main findings from basic research showing interactions between nociception and learning in the spinal cord will be summarized, focusing both on evidence demonstrating the impact of nociception on motor learning and of motor learning on central sensitization. Then, the generalizability of these findings in animal models to humans will be discussed. Finally, the way potential interactions between nociception and motor learning are currently taken into account in clinical research in patients with spinal cord injury will be presented. To conclude, recommendations will be proposed to better integrate findings from basic research into future clinical research in persons with spinal cord injury.
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Affiliation(s)
- Catherine Mercier
- 1 Centre Interdisciplinaire de Recherche en Réadaptation et Intégration Sociale, Quebec City, Quebec, Canada.,2 Laval University, Quebec City, Quebec, Canada
| | - Meyke Roosink
- 1 Centre Interdisciplinaire de Recherche en Réadaptation et Intégration Sociale, Quebec City, Quebec, Canada
| | - Jason Bouffard
- 1 Centre Interdisciplinaire de Recherche en Réadaptation et Intégration Sociale, Quebec City, Quebec, Canada.,2 Laval University, Quebec City, Quebec, Canada
| | - Laurent J Bouyer
- 1 Centre Interdisciplinaire de Recherche en Réadaptation et Intégration Sociale, Quebec City, Quebec, Canada.,2 Laval University, Quebec City, Quebec, Canada
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Huang YJ, Lee KH, Murphy L, Garraway SM, Grau JW. Acute spinal cord injury (SCI) transforms how GABA affects nociceptive sensitization. Exp Neurol 2016; 285:82-95. [PMID: 27639636 PMCID: PMC5926208 DOI: 10.1016/j.expneurol.2016.09.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Revised: 09/09/2016] [Accepted: 09/12/2016] [Indexed: 10/21/2022]
Abstract
Noxious input can sensitize pain (nociceptive) circuits within the spinal cord, inducing a lasting increase in spinal cord neural excitability (central sensitization) that is thought to contribute to chronic pain. The development of spinally-mediated central sensitization is regulated by descending fibers and GABAergic interneurons. The current study provides evidence that spinal cord injury (SCI) transforms how GABA affects nociceptive transmission within the spinal cord, recapitulating an earlier developmental state wherein GABA has an excitatory effect. In spinally transected rats, noxious electrical stimulation and inflammation induce enhanced mechanical reactivity (EMR), a behavioral index of nociceptive sensitization. Pretreatment with the GABAA receptor antagonist bicuculline blocked these effects. Peripheral application of an irritant (capsaicin) also induced EMR. Both the induction and maintenance of this effect were blocked by bicuculline. Cellular indices of central sensitization [c-fos expression and ERK phosphorylation (pERK)] were also attenuated. In intact (sham operated) rats, bicuculline had the opposite effect. Pretreatment with a GABA agonist (muscimol) attenuated nociceptive sensitization in intact, but not spinally injured, rats. The effect of SCI on GABA function was linked to a reduction in the Cl- transporter, KCC2, leading to a reduction in intracellular Cl- that would attenuate GABA-mediated inhibition. Pharmacologically blocking the KCC2 channel (with i.t. DIOA) in intact rats mimicked the effect of SCI. Conversely, a pharmacological treatment (bumetanide) that should increase intracellular Cl- levels blocked the effect of SCI. The results suggest that GABAergic neurons drive, rather than inhibit, the development of nociceptive sensitization after spinal injury.
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Affiliation(s)
- Yung-Jen Huang
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843, USA.
| | - Kuan H Lee
- Center for Pain Research, Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - Lauren Murphy
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843, USA
| | - Sandra M Garraway
- Department of Physiology, Emory University School of Medicine, Atlanta, GA 30307, USA
| | - James W Grau
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843, USA
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Mavromatis N, Gagné M, Voisin JIAV, Reilly KT, Mercier C. Experimental tonic hand pain modulates the corticospinal plasticity induced by a subsequent hand deafferentation. Neuroscience 2016; 330:403-9. [PMID: 27291642 DOI: 10.1016/j.neuroscience.2016.06.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2016] [Revised: 05/30/2016] [Accepted: 06/04/2016] [Indexed: 02/06/2023]
Abstract
Sensorimotor reorganization is believed to play an important role in the development and maintenance of phantom limb pain, but pain itself might modulate sensorimotor plasticity induced by deafferentation. Clinical and basic research support this idea, as pain prior to amputation increases the risk of developing post-amputation pain. The aim of this study was to examine the influence of experimental tonic cutaneous hand pain on the plasticity induced by temporary ischemic hand deafferentation. Sixteen healthy subjects participated in two experimental sessions (Pain, No Pain) in which transcranial magnetic stimulation was used to assess corticospinal excitability in two forearm muscles (flexor carpi radialis and flexor digitorum superficialis) before (T0, T10, T20, and T40) and after (T60 and T75) inflation of a cuff around the wrist. The cuff was inflated at T45 in both sessions and in the Pain session capsaicin cream was applied on the dorsum of the hand at T5. Corticospinal excitability was significantly greater during the Post-inflation phase (p=0.002) and increased similarly in both muscles (p=0.861). Importantly, the excitability increase in the Post-inflation phase was greater for the Pain than the No-Pain condition (p=0.006). Post-hoc analyses revealed a significant difference between the two conditions during the Post-inflation phase (p=0.030) but no difference during the Pre-inflation phase (p=0.601). In other words, the corticospinal facilitation was greater when pain was present prior to cuff inflation. These results indicate that pain can modulate the plasticity induced by another event, and could partially explain the sensorimotor reorganization often reported in chronic pain populations.
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Affiliation(s)
- N Mavromatis
- Center for Interdisciplinary Research in Rehabilitation and Social Integration, Québec, Canada; Department of Rehabilitation, Laval University, Québec, Canada
| | - M Gagné
- Center for Interdisciplinary Research in Rehabilitation and Social Integration, Québec, Canada
| | - J I A V Voisin
- Center for Interdisciplinary Research in Rehabilitation and Social Integration, Québec, Canada; Department of Rehabilitation, Laval University, Québec, Canada
| | - K T Reilly
- INSERM U1028, CNRS UMR5292, Lyon Neuroscience Research Center, ImpAct Team, Lyon, France; University Claude Bernard Lyon I, Lyon, France
| | - C Mercier
- Center for Interdisciplinary Research in Rehabilitation and Social Integration, Québec, Canada; Department of Rehabilitation, Laval University, Québec, Canada.
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AMPA Receptor Phosphorylation and Synaptic Colocalization on Motor Neurons Drive Maladaptive Plasticity below Complete Spinal Cord Injury. eNeuro 2015; 2:eN-NWR-0091-15. [PMID: 26668821 PMCID: PMC4677690 DOI: 10.1523/eneuro.0091-15.2015] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 10/05/2015] [Accepted: 10/05/2015] [Indexed: 12/22/2022] Open
Abstract
Clinical spinal cord injury (SCI) is accompanied by comorbid peripheral injury in 47% of patients. Human and animal modeling data have shown that painful peripheral injuries undermine long-term recovery of locomotion through unknown mechanisms. Peripheral nociceptive stimuli induce maladaptive synaptic plasticity in dorsal horn sensory systems through AMPA receptor (AMPAR) phosphorylation and trafficking to synapses. Here we test whether ventral horn motor neurons in rats demonstrate similar experience-dependent maladaptive plasticity below a complete SCI in vivo. Quantitative biochemistry demonstrated that intermittent nociceptive stimulation (INS) rapidly and selectively increases AMPAR subunit GluA1 serine 831 phosphorylation and localization to synapses in the injured spinal cord, while reducing synaptic GluA2. These changes predict motor dysfunction in the absence of cell death signaling, suggesting an opportunity for therapeutic reversal. Automated confocal time-course analysis of lumbar ventral horn motor neurons confirmed a time-dependent increase in synaptic GluA1 with concurrent decrease in synaptic GluA2. Optical fractionation of neuronal plasma membranes revealed GluA2 removal from extrasynaptic sites on motor neurons early after INS followed by removal from synapses 2 h later. As GluA2-lacking AMPARs are canonical calcium-permeable AMPARs (CP-AMPARs), their stimulus- and time-dependent insertion provides a therapeutic target for limiting calcium-dependent dynamic maladaptive plasticity after SCI. Confirming this, a selective CP-AMPAR antagonist protected against INS-induced maladaptive spinal plasticity, restoring adaptive motor responses on a sensorimotor spinal training task. These findings highlight the critical involvement of AMPARs in experience-dependent spinal cord plasticity after injury and provide a pharmacologically targetable synaptic mechanism by which early postinjury experience shapes motor plasticity.
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Nielson JL, Haefeli J, Salegio EA, Liu AW, Guandique CF, Stück ED, Hawbecker S, Moseanko R, Strand SC, Zdunowski S, Brock JH, Roy RR, Rosenzweig ES, Nout-Lomas YS, Courtine G, Havton LA, Steward O, Reggie Edgerton V, Tuszynski MH, Beattie MS, Bresnahan JC, Ferguson AR. Leveraging biomedical informatics for assessing plasticity and repair in primate spinal cord injury. Brain Res 2014; 1619:124-38. [PMID: 25451131 DOI: 10.1016/j.brainres.2014.10.048] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Revised: 10/22/2014] [Accepted: 10/23/2014] [Indexed: 11/18/2022]
Abstract
Recent preclinical advances highlight the therapeutic potential of treatments aimed at boosting regeneration and plasticity of spinal circuitry damaged by spinal cord injury (SCI). With several promising candidates being considered for translation into clinical trials, the SCI community has called for a non-human primate model as a crucial validation step to test efficacy and validity of these therapies prior to human testing. The present paper reviews the previous and ongoing efforts of the California Spinal Cord Consortium (CSCC), a multidisciplinary team of experts from 5 University of California medical and research centers, to develop this crucial translational SCI model. We focus on the growing volumes of high resolution data collected by the CSCC, and our efforts to develop a biomedical informatics framework aimed at leveraging multidimensional data to monitor plasticity and repair targeting recovery of hand and arm function. Although the main focus of many researchers is the restoration of voluntary motor control, we also describe our ongoing efforts to add assessments of sensory function, including pain, vital signs during surgery, and recovery of bladder and bowel function. By pooling our multidimensional data resources and building a unified database infrastructure for this clinically relevant translational model of SCI, we are now in a unique position to test promising therapeutic strategies' efficacy on the entire syndrome of SCI. We review analyses highlighting the intersection between motor, sensory, autonomic and pathological contributions to the overall restoration of function. This article is part of a Special Issue entitled SI: Spinal cord injury.
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Affiliation(s)
- Jessica L Nielson
- Brain and Spinal Injury Center (BASIC), Department of Neurological Surgery, University of California, San Francisco, CA (UCSF), United States
| | - Jenny Haefeli
- Brain and Spinal Injury Center (BASIC), Department of Neurological Surgery, University of California, San Francisco, CA (UCSF), United States
| | - Ernesto A Salegio
- Brain and Spinal Injury Center (BASIC), Department of Neurological Surgery, University of California, San Francisco, CA (UCSF), United States
| | - Aiwen W Liu
- Brain and Spinal Injury Center (BASIC), Department of Neurological Surgery, University of California, San Francisco, CA (UCSF), United States
| | - Cristian F Guandique
- Brain and Spinal Injury Center (BASIC), Department of Neurological Surgery, University of California, San Francisco, CA (UCSF), United States
| | - Ellen D Stück
- Brain and Spinal Injury Center (BASIC), Department of Neurological Surgery, University of California, San Francisco, CA (UCSF), United States
| | - Stephanie Hawbecker
- California National Primate Research Center (CNPRC), University of California, Davis, CA (UCD), United States
| | - Rod Moseanko
- California National Primate Research Center (CNPRC), University of California, Davis, CA (UCD), United States
| | - Sarah C Strand
- California National Primate Research Center (CNPRC), University of California, Davis, CA (UCD), United States
| | - Sharon Zdunowski
- Department of Integrative Biology and Physiology, University of California, Los Angeles, CA (UCLA), United States
| | - John H Brock
- Center for Neural Repair, Department of Neurosciences, University of California, San Diego, La Jolla, CA (UCSD), United States
| | - Roland R Roy
- Department of Integrative Biology and Physiology, University of California, Los Angeles, CA (UCLA), United States
| | - Ephron S Rosenzweig
- Center for Neural Repair, Department of Neurosciences, University of California, San Diego, La Jolla, CA (UCSD), United States
| | - Yvette S Nout-Lomas
- Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, United States
| | - Gregoire Courtine
- Center for Neuroprosthetics and Brain Mind Institute, Swiss Federal Institute of Technology (EPFL), United States
| | - Leif A Havton
- Reeve-Irvine Research Center (RIRC), University of California, Irvine, CA (UCI), United States; Departments of Anesthesiology & Perioperative Care, Neurology, and Anatomy & Neurobiology, University of California, Irvine, CA, United States
| | - Oswald Steward
- Reeve-Irvine Research Center (RIRC), University of California, Irvine, CA (UCI), United States; Departments of Anatomy & Neurobiology, Neurobiology & Behavior, and Neurosurgery, University of California, Irvine, CA, United States
| | - V Reggie Edgerton
- Department of Integrative Biology and Physiology, University of California, Los Angeles, CA (UCLA), United States
| | - Mark H Tuszynski
- Departments of Anesthesiology & Perioperative Care, Neurology, and Anatomy & Neurobiology, University of California, Irvine, CA, United States; Veterans Administration Medical Center, La Jolla, CA, United States
| | - Michael S Beattie
- Brain and Spinal Injury Center (BASIC), Department of Neurological Surgery, University of California, San Francisco, CA (UCSF), United States
| | - Jacqueline C Bresnahan
- Brain and Spinal Injury Center (BASIC), Department of Neurological Surgery, University of California, San Francisco, CA (UCSF), United States
| | - Adam R Ferguson
- Brain and Spinal Injury Center (BASIC), Department of Neurological Surgery, University of California, San Francisco, CA (UCSF), United States.
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18
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Tonic pain experienced during locomotor training impairs retention despite normal performance during acquisition. J Neurosci 2014; 34:9190-5. [PMID: 25009252 DOI: 10.1523/jneurosci.5303-13.2014] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Many patients are in pain when they receive gait training during rehabilitation. Based on animal studies, it has been proposed that central sensitization associated to nociception (maladaptive plasticity) and plasticity related to the sensorimotor learning (adaptive plasticity) share similar neural mechanisms and compete with each other. The aim of this study was to evaluate whether experimental tonic pain influences motor learning (acquisition and next-day retention) of a new locomotor task. Thirty healthy human subjects performed a locomotor adaptation task (perturbing force field applied to the ankle during swing using a robotized orthosis) on 2 consecutive days. Learning was assessed using kinematic measures (peak and mean absolute plantarflexion errors) and electromyographic (EMG) activity. Half of the participants performed the locomotor adaptation task with pain on Day 1 (capsaicin cream around the ankle), while the task was performed pain-free for all subjects on Day 2 to assess retention. Pain had no significant effect on baseline gait parameters nor on performance during the locomotor adaptation task (for either kinematic or EMG measures) on Day 1. Despite this apparently normal motor acquisition, pain-free Day 2 performance was markedly and significantly impaired in the Pain group, indicating that pain during training had an impact on the retention of motor memories (interfering with consolidation and/or retrieval). These results suggest that the same motor rehabilitation intervention could be less effective if administered in the presence of pain.
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19
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Grau JW, Huie JR, Lee KH, Hoy KC, Huang YJ, Turtle JD, Strain MM, Baumbauer KM, Miranda RM, Hook MA, Ferguson AR, Garraway SM. Metaplasticity and behavior: how training and inflammation affect plastic potential within the spinal cord and recovery after injury. Front Neural Circuits 2014; 8:100. [PMID: 25249941 PMCID: PMC4157609 DOI: 10.3389/fncir.2014.00100] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Accepted: 07/31/2014] [Indexed: 12/30/2022] Open
Abstract
Research has shown that spinal circuits have the capacity to adapt in response to training, nociceptive stimulation and peripheral inflammation. These changes in neural function are mediated by physiological and neurochemical systems analogous to those that support plasticity within the hippocampus (e.g., long-term potentiation and the NMDA receptor). As observed in the hippocampus, engaging spinal circuits can have a lasting impact on plastic potential, enabling or inhibiting the capacity to learn. These effects are related to the concept of metaplasticity. Behavioral paradigms are described that induce metaplastic effects within the spinal cord. Uncontrollable/unpredictable stimulation, and peripheral inflammation, induce a form of maladaptive plasticity that inhibits spinal learning. Conversely, exposure to controllable or predictable stimulation engages a form of adaptive plasticity that counters these maladaptive effects and enables learning. Adaptive plasticity is tied to an up-regulation of brain derived neurotrophic factor (BDNF). Maladaptive plasticity is linked to processes that involve kappa opioids, the metabotropic glutamate (mGlu) receptor, glia, and the cytokine tumor necrosis factor (TNF). Uncontrollable nociceptive stimulation also impairs recovery after a spinal contusion injury and fosters the development of pain (allodynia). These adverse effects are related to an up-regulation of TNF and a down-regulation of BDNF and its receptor (TrkB). In the absence of injury, brain systems quell the sensitization of spinal circuits through descending serotonergic fibers and the serotonin 1A (5HT 1A) receptor. This protective effect is blocked by surgical anesthesia. Disconnected from the brain, intracellular Cl- concentrations increase (due to a down-regulation of the cotransporter KCC2), which causes GABA to have an excitatory effect. It is suggested that BDNF has a restorative effect because it up-regulates KCC2 and re-establishes GABA-mediated inhibition.
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Affiliation(s)
- James W Grau
- Cellular and Behavioral Neuroscience, Department of Psychology, Texas A&M University, College Station TX, USA
| | - J Russell Huie
- Department of Neurological Surgery, Brain and Spinal Injury Center, University of California San Francisco San Francisco, CA, USA
| | - Kuan H Lee
- Cellular and Behavioral Neuroscience, Department of Psychology, Texas A&M University, College Station TX, USA
| | - Kevin C Hoy
- Department of Neurosciences, MetroHealth Medical Center and Case Western Reserve University Cleveland, OH, USA
| | - Yung-Jen Huang
- Cellular and Behavioral Neuroscience, Department of Psychology, Texas A&M University, College Station TX, USA
| | - Joel D Turtle
- Cellular and Behavioral Neuroscience, Department of Psychology, Texas A&M University, College Station TX, USA
| | - Misty M Strain
- Cellular and Behavioral Neuroscience, Department of Psychology, Texas A&M University, College Station TX, USA
| | | | - Rajesh M Miranda
- Department of Neuroscience and Experimental Therapeutics, Texas A&M Health Science Center Bryan, TX, USA
| | - Michelle A Hook
- Department of Neuroscience and Experimental Therapeutics, Texas A&M Health Science Center Bryan, TX, USA
| | - Adam R Ferguson
- Department of Neurological Surgery, Brain and Spinal Injury Center, University of California San Francisco San Francisco, CA, USA
| | - Sandra M Garraway
- Department of Physiology, Emory University School of Medicine Atlanta, GA, USA
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Petruska JC, Hubscher CH, Rabchevsky AG. Challenges and opportunities of sensory plasticity after SCI. Front Physiol 2013; 4:231. [PMID: 23986722 PMCID: PMC3753431 DOI: 10.3389/fphys.2013.00231] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 08/07/2013] [Indexed: 12/30/2022] Open
Affiliation(s)
- Jeffrey C Petruska
- Department of Anatomical Sciences and Neurobiology, Kentucky Spinal Cord Injury Research Center, University of Louisville Louisville, KY, USA
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21
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Learning from the spinal cord: how the study of spinal cord plasticity informs our view of learning. Neurobiol Learn Mem 2013; 108:155-71. [PMID: 23973905 DOI: 10.1016/j.nlm.2013.08.003] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Revised: 08/01/2013] [Accepted: 08/07/2013] [Indexed: 01/10/2023]
Abstract
The paper reviews research examining whether and how training can induce a lasting change in spinal cord function. A framework for the study of learning, and some essential issues in experimental design, are discussed. A core element involves delayed assessment under common conditions. Research has shown that brain systems can induce a lasting (memory-like) alteration in spinal function. Neurons within the lower (lumbosacral) spinal cord can also adapt when isolated from the brain by means of a thoracic transection. Using traditional learning paradigms, evidence suggests that spinal neurons support habituation and sensitization as well as Pavlovian and instrumental conditioning. At a neurobiological level, spinal systems support phenomena (e.g., long-term potentiation), and involve mechanisms (e.g., NMDA mediated plasticity, protein synthesis) implicated in brain-dependent learning and memory. Spinal learning also induces modulatory effects that alter the capacity for learning. Uncontrollable/unpredictable stimulation disables the capacity for instrumental learning and this effect has been linked to the cytokine tumor necrosis factor (TNF). Predictable/controllable stimulation enables learning and counters the adverse effects of uncontrollable stimulation through a process that depends upon brain-derived neurotrophic factor (BDNF). Finally, uncontrollable, but not controllable, nociceptive stimulation impairs recovery after a contusion injury. A process-oriented approach (neurofunctionalism) is outlined that encourages a broader view of learning phenomena.
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22
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Hillen BK, Abbas JJ, Jung R. Accelerating locomotor recovery after incomplete spinal injury. Ann N Y Acad Sci 2013; 1279:164-74. [PMID: 23531014 DOI: 10.1111/nyas.12061] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A traumatic spinal injury can destroy cells, irreparably damage axons, and trigger a cascade of biochemical responses that increase the extent of injury. Although damaged central nervous system axons do not regrow well naturally, the distributed nature of the nervous system and its capacity to adapt provide opportunities for recovery of function. It is apparent that activity-dependent plasticity plays a role in this recovery and that the endogenous response to injury heightens the capacity for recovery for at least several weeks postinjury. To restore locomotor function, researchers have investigated the use of treadmill-based training, robots, and electrical stimulation to tap into adaptive activity-dependent processes. The current challenge is to maximize the degree of functional recovery. This manuscript reviews the endogenous neural system response to injury, and reviews data and presents novel analyses of these from a rat model of contusion injury that demonstrates how a targeted intervention can accelerate recovery, presumably by engaging processes that underlie activity-dependent plasticity.
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Affiliation(s)
- Brian K Hillen
- Department of Biomedical Engineering, Florida International University, Miami, FL 33174, USA
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23
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Hougland MT, Harrison BJ, Magnuson DSK, Rouchka EC, Petruska JC. The Transcriptional Response of Neurotrophins and Their Tyrosine Kinase Receptors in Lumbar Sensorimotor Circuits to Spinal Cord Contusion is Affected by Injury Severity and Survival Time. Front Physiol 2013; 3:478. [PMID: 23316162 PMCID: PMC3540763 DOI: 10.3389/fphys.2012.00478] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Accepted: 12/07/2012] [Indexed: 01/19/2023] Open
Abstract
Traumatic spinal cord injury (SCI) results in changes to the anatomical, neurochemical, and physiological properties of cells in the central and peripheral nervous system. Neurotrophins, acting by binding to their cognate Trk receptors on target cell membranes, contribute to modulation of anatomical, neurochemical, and physiological properties of neurons in sensorimotor circuits in both the intact and injured spinal cord. Neurotrophin signaling is associated with many post-SCI changes including maladaptive plasticity leading to pain and autonomic dysreflexia, but also therapeutic approaches such as training-induced locomotor improvement. Here we characterize expression of mRNA for neurotrophins and Trk receptors in lumbar dorsal root ganglia (DRG) and spinal cord after two different severities of mid-thoracic injury and at 6 and 12 weeks post-SCI. There was complex regulation that differed with tissue, injury severity, and survival time, including reversals of regulation between 6 and 12 weeks, and the data suggest that natural regulation of neurotrophins in the spinal cord may continue for months after birth. Our assessments determined that a coordination of gene expression emerged at the 12-week post-SCI time point and bioinformatic analyses address possible mechanisms. These data can inform studies meant to determine the role of the neurotrophin signaling system in post-SCI function and plasticity, and studies using this signaling system as a therapeutic approach.
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Affiliation(s)
- M Tyler Hougland
- Department of Anatomical Sciences and Neurobiology, University of Louisville Louisville, KY, USA ; Laboratory of Neural Physiology and Plasticity, Kentucky Spinal Cord Injury Research Center, Department of Neurological Surgery Louisville, KY, USA
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Ferguson AR, Huie JR, Crown ED, Baumbauer KM, Hook MA, Garraway SM, Lee KH, Hoy KC, Grau JW. Maladaptive spinal plasticity opposes spinal learning and recovery in spinal cord injury. Front Physiol 2012; 3:399. [PMID: 23087647 PMCID: PMC3468083 DOI: 10.3389/fphys.2012.00399] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Accepted: 09/20/2012] [Indexed: 01/23/2023] Open
Abstract
Synaptic plasticity within the spinal cord has great potential to facilitate recovery of function after spinal cord injury (SCI). Spinal plasticity can be induced in an activity-dependent manner even without input from the brain after complete SCI. A mechanistic basis for these effects is provided by research demonstrating that spinal synapses have many of the same plasticity mechanisms that are known to underlie learning and memory in the brain. In addition, the lumbar spinal cord can sustain several forms of learning and memory, including limb-position training. However, not all spinal plasticity promotes recovery of function. Central sensitization of nociceptive (pain) pathways in the spinal cord may emerge in response to various noxious inputs, demonstrating that plasticity within the spinal cord may contribute to maladaptive pain states. In this review we discuss interactions between adaptive and maladaptive forms of activity-dependent plasticity in the spinal cord below the level of SCI. The literature demonstrates that activity-dependent plasticity within the spinal cord must be carefully tuned to promote adaptive spinal training. Prior work from our group has shown that stimulation that is delivered in a limb position-dependent manner or on a fixed interval can induce adaptive plasticity that promotes future spinal cord learning and reduces nociceptive hyper-reactivity. On the other hand, stimulation that is delivered in an unsynchronized fashion, such as randomized electrical stimulation or peripheral skin injuries, can generate maladaptive spinal plasticity that undermines future spinal cord learning, reduces recovery of locomotor function, and promotes nociceptive hyper-reactivity after SCI. We review these basic phenomena, how these findings relate to the broader spinal plasticity literature, discuss the cellular and molecular mechanisms, and finally discuss implications of these and other findings for improved rehabilitative therapies after SCI.
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Affiliation(s)
- Adam R Ferguson
- Department of Neurological Surgery, Brain and Spinal Injury Center, University of California San Francisco San Francisco, CA, USA
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