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Idlett-Ali S, Kloefkorn H, Goolsby W, Hochman S. Relating Spinal Injury-Induced Neuropathic Pain and Spontaneous Afferent Activity to Sleep and Respiratory Dysfunction. J Neurotrauma 2023; 40:2654-2666. [PMID: 37212274 PMCID: PMC11093096 DOI: 10.1089/neu.2022.0305] [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] [Indexed: 05/23/2023] Open
Abstract
Abstract Spinal cord injury (SCI) can induce dysfunction in a multitude of neural circuits including those that lead to impaired sleep, respiratory dysfunction, and neuropathic pain. We used a lower thoracic rodent contusion SCI model of neuropathic pain that has been shown to associate with increased spontaneous activity in primary afferents and hindlimb mechanosensory stimulus hypersensitivity. Here we paired capture of these variables with chronic capture of three state sleep and respiration to more broadly understand SCI-induced physiological dysfunction and to assess possible interrelations. Noncontact electric field sensors were embedded into home cages to non-invasively capture the temporal evolution of sleep and respiration changes for six weeks after SCI in naturally behaving mice. Hindlimb mechanosensitivity was assessed weekly, and terminal experiments measured primary afferent spontaneous activity in situ from intact lumbar dorsal root ganglia (DRG). We observed that SCI led to increased spontaneous primary afferent activity (both firing rate and the number of spontaneously active DRGs) that correlated with increased respiratory rate variability and measures of sleep fragmentation. This is the first study to measure and link sleep dysfunction and variability in respiratory rate in a SCI model of neuropathic pain, and thereby provide broader insight into the magnitude of overall stress burden initiated by neural circuit dysfunction after SCI.
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Affiliation(s)
- Shaquia Idlett-Ali
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
- Department of Physiology, School of Medicine, Emory University, Atlanta, Georgia, USA
| | - Heidi Kloefkorn
- Department of Chemical, Biological, and Environmental Engineering, Oregon State University, Corvallis, Oregon, USA
| | - William Goolsby
- Department of Physiology, School of Medicine, Emory University, Atlanta, Georgia, USA
| | - Shawn Hochman
- Department of Physiology, School of Medicine, Emory University, Atlanta, Georgia, USA
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Li L, Liu Y, Hu W, Yang J, Ma S, Tian Z, Cao Z, Pan K, Jiang M, Liu X, Wu S, Luo C, Xie RG. Peripheral CCL2 induces inflammatory pain via regulation of Ih currents in small diameter DRG neurons. Front Mol Neurosci 2023; 16:1144614. [PMID: 37860084 PMCID: PMC10582564 DOI: 10.3389/fnmol.2023.1144614] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2023] [Accepted: 09/14/2023] [Indexed: 10/21/2023] Open
Abstract
The C-C motif chemokine ligand 2 (CCL2) has been implicated in chronic pain, but its exact mechanism of peripheral sensitization is unknown. In this study, we aimed to clarify the mechanism of CCL2 regulation of ion channels. Our behavioral experiments revealed that ZD7288, a blocker of Ih current, can inhibit CFA and CCL2-mediated mechanical and thermal nociceptive sensitization. Furthermore, patch clamp studies demonstrated that CFA-induced peripheral sensitization primarily affects the excitability of small-diameter DRG neurons. Further studies revealed that inflammatory pain caused by CFA or incubation of DRG with CCL2 mainly affected Ih currents in small-diameter DRG neurons, which were blocked by co-incubation CCR2 antagonist INCB3344 or adenylate cyclase inhibitor SQ22536. Immunohistochemical staining showed that both intraplantar injection of CFA as well as DRG injection of CCL2 resulted in significant upregulation of CCR2+/HCN2+ expression. In conclusion, we suggest in the inflammatory pain state, CCL2 can act on small-diameter DRG neurons, leading to upregulation of HCN2 expression and consequently Ih, which in turn leads to neuronal hyperexcitability.
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Affiliation(s)
- Lamei Li
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
- School of Life Sciences & Research Center for Resource Peptide Drugs, Shaanxi Engineering & Technological Research Center for Conversation & Utilization of Regional Biological Resources, Yan’an University, Yan’an, China
| | - Yuanying Liu
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
- School of Life Sciences & Research Center for Resource Peptide Drugs, Shaanxi Engineering & Technological Research Center for Conversation & Utilization of Regional Biological Resources, Yan’an University, Yan’an, China
| | - Wenchao Hu
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
| | - Jing Yang
- Heart Hospital, Xi’an International Medical Center Hospital, Xi’an, China
| | - Suibin Ma
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
| | - Zhicheng Tian
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
| | - Zixuan Cao
- No.6 Cadet Regiment, School of Basic Medical Sciences, Fourth Military Medical University, Xi’an, China
| | - Kunqing Pan
- No.19 Cadet Regiment, School of Basic Medical Sciences, Fourth Military Medical University, Xi’an, China
| | - Ming Jiang
- School of Life Sciences & Research Center for Resource Peptide Drugs, Shaanxi Engineering & Technological Research Center for Conversation & Utilization of Regional Biological Resources, Yan’an University, Yan’an, China
| | - Xia Liu
- School of Life Sciences & Research Center for Resource Peptide Drugs, Shaanxi Engineering & Technological Research Center for Conversation & Utilization of Regional Biological Resources, Yan’an University, Yan’an, China
| | - Shengxi Wu
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
| | - Ceng Luo
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
| | - Rou-Gang Xie
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
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3
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Körner J, Lampert A. Functional subgroups of rat and human sensory neurons: a systematic review of electrophysiological properties. Pflugers Arch 2022; 474:367-385. [PMID: 35031856 PMCID: PMC8924089 DOI: 10.1007/s00424-021-02656-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Revised: 11/23/2021] [Accepted: 12/14/2021] [Indexed: 11/15/2022]
Abstract
Sensory neurons are responsible for the generation and transmission of nociceptive signals from the periphery to the central nervous system. They encompass a broadly heterogeneous population of highly specialized neurons. The understanding of the molecular choreography of individual subpopulations is essential to understand physiological and pathological pain states. Recently, it became evident that species differences limit transferability of research findings between human and rodents in pain research. Thus, it is necessary to systematically compare and categorize the electrophysiological data gained from human and rodent dorsal root ganglia neurons (DRGs). In this systematic review, we condense the available electrophysiological data defining subidentities in human and rat DRGs. A systematic search on PUBMED yielded 30 studies on rat and 3 studies on human sensory neurons. Defined outcome parameters included current clamp, voltage clamp, cell morphology, pharmacological readouts, and immune reactivity parameters. We compare evidence gathered for outcome markers to define subgroups, offer electrophysiological parameters for the definition of neuronal subtypes, and give a framework for the transferability of electrophysiological findings between species. A semiquantitative analysis revealed that for rat DRGs, there is an overarching consensus between studies that C-fiber linked sensory neurons display a lower action potential threshold, higher input resistance, a larger action potential overshoot, and a longer afterhyperpolarization duration compared to other sensory neurons. They are also more likely to display an infliction point in the falling phase of the action potential. This systematic review points out the need of more electrophysiological studies on human sensory neurons.
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Affiliation(s)
- Jannis Körner
- Institute of Physiology, Uniklinik RWTH Aachen, Pauwelsstrasse 30, 52074, Aachen, Germany.,Clinic of Anesthesiology, Uniklinik RWTH Aachen, Pauwelsstrasse 30, 52074, Aachen, Germany
| | - Angelika Lampert
- Institute of Physiology, Uniklinik RWTH Aachen, Pauwelsstrasse 30, 52074, Aachen, Germany.
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Kudo M, Wupuer S, Fujiwara M, Saito Y, Kubota S, Inoue KI, Takada M, Seki K. Specific gene expression in unmyelinated dorsal root ganglion neurons in nonhuman primates by intra-nerve injection of AAV 6 vector. MOLECULAR THERAPY-METHODS & CLINICAL DEVELOPMENT 2021; 23:11-22. [PMID: 34552999 PMCID: PMC8426475 DOI: 10.1016/j.omtm.2021.07.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Accepted: 07/27/2021] [Indexed: 01/14/2023]
Abstract
Adeno-associated virus 6 (AAV6) has been proposed as a potential vector candidate for specific gene expression in pain-related dorsal root ganglion (DRG) neurons, but this has not been confirmed in nonhuman primates. The aim of our study was to analyze the transduction efficiency and target specificity of this viral vector in the common marmoset by comparing it with those in the rat. When green fluorescent protein-expressing serotype-6 vector was injected into the sciatic nerve, the efficiency of gene expression in DRG neurons was comparable in both species. We found that the serotype-6 vector was largely specific to the pain-related ganglion neurons in the marmoset, as well as in the rat, whereas the serotype-9 vector resulted in contrasting effects in the two species. Neither AAV6 nor AAV9 resulted in DRG toxicity when administered via the sciatic nerve, suggesting this as a safer route of sensory nerve transduction than the currently used intrathecal or intravenous administrative routes. Furthermore, the AAV6 vector could be an optimal serotype for gene therapy for human chronic pain that has a minimal effect on other somatosensory functions of DRG neurons.
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Affiliation(s)
- Moeko Kudo
- Department of Neurophysiology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo, Japan
| | - Sidikejiang Wupuer
- Department of Neurophysiology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo, Japan
| | - Maki Fujiwara
- Systems Neuroscience Section, Department of Neuroscience, Primate Research Institute, Kyoto University, Inuyama, Aichi, Japan
| | - Yuko Saito
- Department of Neuropathology, Tokyo Metropolitan Institute of Gerontology, Itabashi, Tokyo, Japan
| | - Shinji Kubota
- Department of Neurophysiology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo, Japan
| | - Ken-Ichi Inoue
- Systems Neuroscience Section, Department of Neuroscience, Primate Research Institute, Kyoto University, Inuyama, Aichi, Japan
| | - Masahiko Takada
- Systems Neuroscience Section, Department of Neuroscience, Primate Research Institute, Kyoto University, Inuyama, Aichi, Japan
| | - Kazuhiko Seki
- Department of Neurophysiology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo, Japan
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Lin JH, Yu YW, Chuang YC, Lee CH, Chen CC. ATF3-Expressing Large-Diameter Sensory Afferents at Acute Stage as Bio-Signatures of Persistent Pain Associated with Lumbar Radiculopathy. Cells 2021; 10:cells10050992. [PMID: 33922541 PMCID: PMC8145235 DOI: 10.3390/cells10050992] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 04/09/2021] [Accepted: 04/21/2021] [Indexed: 11/16/2022] Open
Abstract
The mechanism of pain chronicity is largely unknown in lumbar radiculopathy (LR). The anatomical location of nerve injury is one of the important factors associated with pain chronicity of LR. Accumulating evidence has shown constriction distal to the dorsal root ganglion (DRG) caused more severe radiculopathy than constriction proximal to the DRG; thereby, the mechanism of pain chronicity in LR could be revealed by comparing the differences in pathological changes of DRGs between nerve constriction distal and proximal to the DRG. Here, we used 2 rat models of LR with nerve constriction distal or proximal to the DRG to probe how the different nerve injury sites could differentially affect pain chronicity and the pathological changes of DRG neuron subpopulations. As expected, rats with nerve constriction distal to the DRG showed more persistent pain behaviors than those with nerve constriction proximal to the DRG in 50% paw withdraw threshold, weight-bearing test, and acetone test. One day after the operation, distal and proximal nerve constriction showed differential pathological changes of DRG. The ratios of activating transcription factor3 (ATF3)-positive DRG neurons were significantly higher in rats with nerve constriction distal to DRG than those with nerve constriction proximal to DRG. In subpopulation analysis, the ratios of ATF3-immunoreactivity (IR) in neurofilament heavy chain (NFH)-positive DRG neurons significantly increased in distal nerve constriction compared to proximal nerve constriction; although, both distal and proximal nerve constriction presented increased ratios of ATF3-IR in calcitonin gene-related peptide (CGRP)-positive DRG neurons. Moreover, the nerve constriction proximal to DRG caused more hypoxia than did that distal to DRG. Together, ATF3 expression in NHF-positive DRG neurons at the acute stage is a potential bio-signature of persistent pain in rat models of LR.
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Affiliation(s)
- Jiann-Her Lin
- Department of Neurosurgery, Taipei Medical University Hospital, Taipei 110301, Taiwan;
- Department of Surgery, Division of Neurosurgery, School of Medicine, College of Medicine, Taipei Medical University, Taipei 110301, Taiwan;
- Taipei Neuroscience Institute, Taipei Medical University, Taipei 110301, Taiwan
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115201, Taiwan; (Y.-C.C.); (C.-H.L.)
| | - Yu-Wen Yu
- Department of Surgery, Division of Neurosurgery, School of Medicine, College of Medicine, Taipei Medical University, Taipei 110301, Taiwan;
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115201, Taiwan; (Y.-C.C.); (C.-H.L.)
| | - Yu-Chia Chuang
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115201, Taiwan; (Y.-C.C.); (C.-H.L.)
| | - Cheng-Han Lee
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115201, Taiwan; (Y.-C.C.); (C.-H.L.)
| | - Chih-Cheng Chen
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115201, Taiwan; (Y.-C.C.); (C.-H.L.)
- Neuroscience Program of Academia Sinica, Academia Sinica, Taipei 115201, Taiwan
- Taiwan Mouse Clinic, Biomedical Translation Research Center, Academia Sinica, Taipei 115202, Taiwan
- Correspondence:
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Ma SB, Xian H, Wu WB, Ma SY, Liu YK, Liang YT, Guo H, Kang JJ, Liu YY, Zhang H, Wu SX, Luo C, Xie RG. CCL2 facilitates spinal synaptic transmission and pain via interaction with presynaptic CCR2 in spinal nociceptor terminals. Mol Brain 2020; 13:161. [PMID: 33228784 PMCID: PMC7685578 DOI: 10.1186/s13041-020-00701-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Accepted: 11/17/2020] [Indexed: 12/19/2022] Open
Abstract
Previous studies have shown that CCL2 may cause chronic pain, but the exact mechanism of central sensitization is unclear. In this article, we further explore the presynaptic role of CCL2. Behavioral experiments show that intervertebral foramen injection CCR2 antagonists into dorsal root ganglion (DRG) can inhibit the inflammatory pain caused by CCL2 in spinal cord. We raised the question of the role of presynaptic CCR2 in the spinal dorsal horn. Subsequent electron microscopy experiments showed that CCR2 was expressed in the presynaptic CGRP terminal in the spinal dorsal horn. CCL2 can enhance presynaptic calcium signal. Whole-cell patch-clamp recordings showed that CCL2 can enhance NMDAR-eEPSCs through presynaptic effects, and further application of glutamate sensor method proved that CCL2 can act on presynaptic CCR2 to increase the release of presynaptic glutamate. In conclusion, we suggest that CCL2 can directly act on the CCR2 on presynaptic terminals of sensory neurons in the spinal dorsal horn, leading to an increase in the release of presynaptic glutamate and participate in the formation of central sensitization.
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Affiliation(s)
- Sui-Bin Ma
- Department of Neurobiology, Fourth Military Medical University, Xi'an, 710032, China
| | - Hang Xian
- Department of Neurobiology, Fourth Military Medical University, Xi'an, 710032, China.,Department of Orthopedics, Xijing Hospital, Fourth Military Medical University, Xi'an, 710032, China
| | - Wen-Bin Wu
- The Fourth Regiment, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032, China
| | - Shuo-Yao Ma
- The Sixth Regiment, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032, China
| | - Yu-Ke Liu
- The Second Regiment, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032, China
| | - Yu-Tong Liang
- The Second Regiment, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032, China
| | - Huan Guo
- Department of Neurobiology, Fourth Military Medical University, Xi'an, 710032, China.,Pain and Related Diseases Research Laboratory, Medical College of Shantou University, Shantou, 515041, China
| | - Jun-Jun Kang
- Department of Neurobiology, Fourth Military Medical University, Xi'an, 710032, China
| | - Ying-Ying Liu
- Department of Neurobiology, Fourth Military Medical University, Xi'an, 710032, China
| | - Hui Zhang
- Department of Neurobiology, Fourth Military Medical University, Xi'an, 710032, China.,Department of Health Statistics, Fourth Military Medical University, Xi'an, 710032, China
| | - Sheng-Xi Wu
- Department of Neurobiology, Fourth Military Medical University, Xi'an, 710032, China
| | - Ceng Luo
- Department of Neurobiology, Fourth Military Medical University, Xi'an, 710032, China.
| | - Rou-Gang Xie
- Department of Neurobiology, Fourth Military Medical University, Xi'an, 710032, China.
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Modulation of Voltage-Gated Sodium Channel Activity in Human Dorsal Root Ganglion Neurons by Herpesvirus Quiescent Infection. J Virol 2020; 94:JVI.01823-19. [PMID: 31694955 DOI: 10.1128/jvi.01823-19] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Accepted: 10/25/2019] [Indexed: 12/15/2022] Open
Abstract
The molecular mechanisms of pain associated with alphaherpesvirus latency are not clear. We hypothesize that the voltage-gated sodium channels (VGSC) on the dorsal root ganglion (DRG) neurons controlling electrical impulses may have abnormal activity during latent viral infection and reactivation. We used herpes simplex virus 1 (HSV-1) to infect the human DRG-derived neuronal cell line HD10.6 in order to study the establishment and maintenance of viral latency, viral reactivation, and changes in the functional expression of VGSCs. Differentiated cells exhibited robust tetrodotoxin (TTX)-sensitive sodium currents, and acute infection significantly reduced the functional expression of VGSCs within 24 h and completely abolished VGSC activity within 3 days. A quiescent state of infection mimicking latency can be achieved in the presence of acyclovir (ACV) for 7 days followed by 5 days of ACV washout, and then the viruses can remain dormant for another 3 weeks. It was noted that during the establishment of HSV-1 latency, the loss of VGSC activity caused by HSV-1 infection could not be blocked by ACV treatment. However, neurons with continued ACV treatment for another 4 days showed a gradual recovery of VGSC functional expression. Furthermore, the latently infected neurons exhibited higher VGSC activity than controls. The overall regulation of VGSCs by HSV-1 during quiescent infection was proved by increased transcription and possible translation of Nav1.7. Together, these observations demonstrated a very complex pattern of electrophysiological changes during HSV infection of DRG neurons, which may have implications for understanding of the mechanisms of virus-mediated pain linked to latency and reactivation.IMPORTANCE The reactivation of herpesviruses, most commonly varicella-zoster virus (VZV) and pseudorabies virus (PRV), may cause cranial nerve disorder and unbearable pain. Clinical studies have also reported that HSV-1 causes postherpetic neuralgia and chronic occipital neuralgia in humans. The current work meticulously studies the functional expression profile changes of VGSCs during the processes of HSV-1 latency establishment and reactivation using human dorsal root ganglion-derived neuronal HD10.6 cells as an in vitro model. Our results indicated that VGSC activity was eliminated upon infection but steadily recovered during latency establishment and that latent neurons exhibited even higher VGSC activity. This finding advances our knowledge of how ganglion neurons generate uncharacteristic electrical impulses due to abnormal VGSC functional expression influenced by the latent virus.
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Kubota S, Sidikejiang W, Kudo M, Inoue KI, Umeda T, Takada M, Seki K. Optogenetic recruitment of spinal reflex pathways from large-diameter primary afferents in non-transgenic rats transduced with AAV9/Channelrhodopsin 2. J Physiol 2019; 597:5025-5040. [PMID: 31397900 PMCID: PMC6851594 DOI: 10.1113/jp278292] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Accepted: 08/07/2019] [Indexed: 01/02/2023] Open
Abstract
Key points We demonstrated optical activation of primary somatosensory afferents with high selectivity to fast‐conducting fibres by means of adeno‐associated virus 9 (AAV9)‐mediated gene transduction in dorsal root ganglion (DRG) neurons. AVV9 expressing green fluorescent protein showed high selectivity and transduction efficiency for fast‐conducting, large‐sized DRG neurons. Compared with conventional electrical stimulation, optically elicited volleys in primary afferents had higher sensitivity with stimulus amplitude, but lower sensitivity with stimulus frequency. Optically elicited dorsal root volleys activated postsynaptic neurons in the segmental spinal pathway. This proposed technique will help establish the causal relationships between somatosensory afferent inputs and neural responses in the CNS as well as behavioural outcomes in higher mammals where transgenic animals are not available.
Abstract Previously, fundamental structures and their mode of action in the spinal reflex circuit were determined by confirming their input–output relationship using electrophysiological techniques. In those experiments, the electrical stimulation of afferent fibres was used as a core element to identify different types of reflex pathways; however, a major disadvantage of this technique is its non‐selectivity. In this study, we investigated the selective activation of large‐diameter afferents by optogenetics combined with a virus vector transduction technique (injection via the sciatic nerve) in non‐transgenic male Jcl:Wistar rats. We found that green fluorescent protein gene transduction of rat dorsal root ganglion (DRG) neurons with a preference for medium‐to‐large‐sized cells was achieved using the adeno‐associated virus 9 (AAV9) vector compared with the AAV6 vector (P = 0.021). Furthermore, the optical stimulation of Channelrhodopsin 2 (ChR2)‐expressing DRG neurons (transduced by AAV9) produced compound action potentials in afferent nerves originating from fast‐conducting nerve fibres. We also confirmed that physiological responses to different stimulus amplitudes were comparable between optogenetic and electrophysiological activation. However, compared with electrically elicited responses, the optically elicited responses had lower sensitivity with stimulus frequency. Finally, we showed that afferent volleys evoked by optical stimulation were sufficient to activate postsynaptic neurons in the spinal reflex arc. These results provide new ways for understanding the role of sensory afferent input to the central nervous system regarding behavioural control, especially when genetically manipulated animals are not available, such as higher mammals including non‐human primates. We demonstrated optical activation of primary somatosensory afferents with high selectivity to fast‐conducting fibres by means of adeno‐associated virus 9 (AAV9)‐mediated gene transduction in dorsal root ganglion (DRG) neurons. AVV9 expressing green fluorescent protein showed high selectivity and transduction efficiency for fast‐conducting, large‐sized DRG neurons. Compared with conventional electrical stimulation, optically elicited volleys in primary afferents had higher sensitivity with stimulus amplitude, but lower sensitivity with stimulus frequency. Optically elicited dorsal root volleys activated postsynaptic neurons in the segmental spinal pathway. This proposed technique will help establish the causal relationships between somatosensory afferent inputs and neural responses in the CNS as well as behavioural outcomes in higher mammals where transgenic animals are not available.
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Affiliation(s)
- Shinji Kubota
- Department of Neurophysiology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo, Japan.,Research Fellow of the Japan Society for the Promotion of Science, Chiyoda-ku, Tokyo, Japan
| | - Wupuer Sidikejiang
- Department of Neurophysiology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo, Japan
| | - Moeko Kudo
- Department of Neurophysiology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo, Japan
| | - Ken-Ichi Inoue
- Systems Neuroscience Section, Department of Neuroscience, Primate Research Institute, Kyoto University, Inuyama, Aichi, Japan.,PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama, Japan
| | - Tatsuya Umeda
- Department of Neurophysiology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo, Japan
| | - Masahiko Takada
- Systems Neuroscience Section, Department of Neuroscience, Primate Research Institute, Kyoto University, Inuyama, Aichi, Japan
| | - Kazuhiko Seki
- Department of Neurophysiology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo, Japan
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9
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Pardo ID, Weber K, Cramer S, Krinke GJ, Butt MT, Sharma AK, Bolon B. Atlas of Normal Microanatomy, Procedural and Processing Artifacts, Common Background Findings, and Neurotoxic Lesions in the Peripheral Nervous System of Laboratory Animals. Toxicol Pathol 2019; 48:105-131. [DOI: 10.1177/0192623319867322] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The ability to differentiate among normal structures, procedural and processing artifacts, spontaneous background changes, and test article–related effects in the peripheral nervous system (PNS) is essential for interpreting microscopic features of ganglia and nerves evaluated in animal species commonly used in toxicity studies evaluating regulated products and chemicals. This atlas provides images of findings that may be encountered in ganglia and nerves of animal species commonly used in product discovery and development. Most atlas images are of tissues from control animals that were processed using routine methods (ie, immersion fixation in neutral-buffered 10% formalin, embedding in paraffin, sectioning at 5 µm, and staining with hematoxylin and eosin) since these preparations are traditionally applied to study materials produced during most animal toxicity studies. A few images are of tissues processed using special procedures (ie, immersion or perfusion fixation using methanol-free 4% formaldehyde, postfixation in glutaraldehyde and osmium, embedding in hard plastic resin, sectioning at 1 µm, and staining with toluidine blue), since these preparations promote better stabilization of lipids and thus optimal resolution of myelin sheaths. Together, this compilation provides a useful resource for discriminating among normal structures, procedure- and processing-related artifacts, incidental background changes, and treatment-induced findings that may be seen in PNS tissues of laboratory animals.
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Affiliation(s)
| | | | - Sarah Cramer
- Tox Path Specialists, LLC (A StageBio Company), Frederick, MD, USA
| | | | - Mark T. Butt
- Tox Path Specialists, LLC (A StageBio Company), Frederick, MD, USA
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He JT, Li XY, Zhao X, Liu X. Hyperpolarization-activated and cyclic nucleotide-gated channel proteins as emerging new targets in neuropathic pain. Rev Neurosci 2019; 30:639-649. [PMID: 30768426 DOI: 10.1515/revneuro-2018-0094] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Accepted: 10/26/2018] [Indexed: 01/14/2023]
Abstract
Abstract
Hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels are activated during hyperpolarization, and there is an inward flow of current, which is termed as hyperpolarization-activated current, Ih. Initially, these channels were identified on the pacemaker cells of the heart. Nowadays, these are identified on different regions of the nervous system, including peripheral nerves, dorsal root ganglia, dorsal horns, and different parts of the brain. There are four different types of HCN channels (HCN1–HCN4); however, HCN1 and HCN2 are more prominent. A large number of studies have shown that peripheral nerve injury increases the amplitude of Ih current in the neurons of the spinal cord and the brain. Moreover, there is an increase in the expression of HCN1 and HCN2 protein channels in peripheral axons and the spinal cord and brain regions in experimental models of nerve injury. Studies have also documented the pain-attenuating actions of selective HCN inhibitors, such as ivabradine and ZD7288. Moreover, certain drugs with additional HCN-blocking activities have also shown pain-attenuating actions in different pain models. There have been few studies documenting the relationship of HCN channels with other mediators of pain. Nevertheless, it may be proposed that the HCN channel activity is modulated by endogenous opioids and cyclo-oxygenase-2, whereas the activation of these channels may modulate the actions of substance P and the expression of spinal N-methyl-D-aspartate receptor subunit 2B to modulate pain. The present review describes the role and mechanisms of HCN ion channels in the development of neuropathic pain.
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Affiliation(s)
- Jin-Ting He
- Department of Neurology , China-Japan Union Hospital, Jilin University , Changchun 130033, Jilin Province , China
| | - Xiao-Yan Li
- Department of Neurology , China-Japan Union Hospital, Jilin University , Changchun 130033, Jilin Province , China
| | - Xin Zhao
- Department of Paediatrics , The First Hospital of Jilin University , Changchun 130021, Jilin Province , China
| | - Xiaoliang Liu
- Cancer Center, The First Hospital of Jilin University , 126 Xiantai Street , Changchun 130033, Jilin Province , China
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