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Wang X, Zhang Y, Guo T, Wu S, Zhong J, Cheng C, Sui X. Selective intrafascicular stimulation of myelinated and unmyelinated nerve fibers through a longitudinal electrode: A computational study. Comput Biol Med 2024; 176:108556. [PMID: 38733726 DOI: 10.1016/j.compbiomed.2024.108556] [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: 04/05/2024] [Accepted: 05/05/2024] [Indexed: 05/13/2024]
Abstract
Carbon nanotube (CNT) fiber electrodes have demonstrated exceptional spatial selectivity and sustained reliability in the context of intrafascicular electrical stimulation, as evidenced through rigorous animal experimentation. A significant presence of unmyelinated C fibers, known to induce uncomfortable somatosensory experiences, exists within peripheral nerves. This presence poses a considerable challenge to the excitation of myelinated Aβ fibers, which are crucial for tactile sensation. To achieve nuanced tactile sensory feedback utilizing CNT fiber electrodes, the selective stimulation of Aβ sensory afferents emerges as a critical factor. In confronting this challenge, the present investigation sought to refine and apply a rat sciatic-nerve model leveraging the capabilities of the COMSOL-NEURON framework. This approach enables a systematic evaluation of the influence exerted by stimulation parameters and electrode geometry on the activation dynamics of both myelinated Aβ and unmyelinated C fibers. The findings advocate for the utilization of current pulses featuring a pulse width of 600 μs, alongside the deployment of CNT fibers characterized by a diminutive diameter of 10 μm, with an exclusively exposed cross-sectional area, to facilitate reduced activation current thresholds. Comparative analysis under monopolar and bipolar electrical stimulation conditions revealed proximate activation thresholds, albeit with bipolar stimulation exhibiting superior fiber selectivity relative to its monopolar counterpart. Concerning pulse waveform characteristics, the adoption of an anodic-first biphasic stimulation modality is favored, taking into account the dual criteria of activation threshold and fiber selectivity optimization. Consequently, this investigation furnishes an efficacious stimulation paradigm for the selective activation of touch-related nerve fibers, alongside provisioning a comprehensive theoretical foundation for the realization of natural tactile feedback within the domain of prosthetic hand applications.
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Affiliation(s)
- Xintong Wang
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Yapeng Zhang
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Tianruo Guo
- Graduate School of Biomedical Engineering, The University of New South Wales, Sydney, NSW, 2052, Australia
| | - Shuhui Wu
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Junwen Zhong
- Department of Electromechanical Engineering, University of Macau, Macau SAR, 999078, China
| | - Chengkung Cheng
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China; Med-X Research Institute, Shanghai Jiao Tong University, Engineering Research Center of Digital Medicine, Ministry of Education, Shanghai, China
| | - Xiaohong Sui
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China.
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2
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Carozzi VA, Salio C, Rodriguez-Menendez V, Ciglieri E, Ferrini F. 2D <em>vs</em> 3D morphological analysis of dorsal root ganglia in health and painful neuropathy. Eur J Histochem 2021; 65. [PMID: 34664808 PMCID: PMC8547168 DOI: 10.4081/ejh.2021.3276] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 08/16/2021] [Indexed: 11/23/2022] Open
Abstract
Dorsal root ganglia (DRGs) are clusters of sensory neurons that transmit the sensory information from the periphery to the central nervous system, and satellite glial cells (SGCs), their supporting trophic cells. Sensory neurons are pseudounipolar neurons with a heterogeneous neurochemistry reflecting their functional features. DRGs, not protected by the blood brain barrier, are vulnerable to stress and damage of different origin (i.e., toxic, mechanical, metabolic, genetic) that can involve sensory neurons, SGCs or, considering their intimate intercommunication, both cell populations. DRG damage, primary or secondary to nerve damage, produces a sensory peripheral neuropathy, characterized by neurophysiological abnormalities, numbness, paraesthesia and dysesthesia, tingling and burning sensations and neuropathic pain. DRG stress can be morphologically detected by light and electron microscope analysis with alterations in cell size (swelling/atrophy) and in different subcellular compartments (i.e., mitochondria, endoplasmic reticulum, and nucleus) of neurons and/or SGCs. In addition, neurochemical changes can be used to portray abnormalities of neurons and SGC. Conventional immunostaining, i.e., immunohistochemical detection of specific molecules in tissue slices, can be employed to detect, localize and quantify particular markers of damage in neurons (i.e., nuclear expression of ATF3) or SGCs (i.e., increased expression of GFAP), markers of apoptosis (i.e., caspases), markers of mitochondrial suffering and oxidative stress (i.e., 8-OHdG), markers of tissue inflammation (i.e., CD68 for macrophage infiltration) etc. However classical (2D) methods of immunostaining disrupt the overall organization of the DRG, thus resulting in the loss of some crucial information. Whole-mount (3D) methods have been recently developed to investigate DRG morphology and neurochemistry without tissue slicing, giving the opportunity to study the intimate relationship between SGCs and sensory neurons in health and disease. Here, we aim to compare classical (2D) vs whole-mount (3D) approaches to highlight “pros” and “cons” of the two methodologies when analysing neuropathy-induced alterations in DRGs.
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Affiliation(s)
- Valentina Alda Carozzi
- Experimental Neurology Unit, School of Medicine and Surgery, University of Milano-Bicocca, Monza (MB).
| | - Chiara Salio
- Department of Veterinary Sciences, University of Turin, Grugliasco (TO).
| | | | | | - Francesco Ferrini
- Department of Veterinary Sciences, University of Turin, Grugliasco (TO).
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3
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Graham RD, Bruns TM, Duan B, Lempka SF. Dorsal root ganglion stimulation for chronic pain modulates Aβ-fiber activity but not C-fiber activity: A computational modeling study. Clin Neurophysiol 2019; 130:941-951. [PMID: 30981900 DOI: 10.1016/j.clinph.2019.02.016] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Revised: 01/23/2019] [Accepted: 02/16/2019] [Indexed: 02/07/2023]
Abstract
OBJECTIVE The goal of this project was to use computational models to investigate which types of primary sensory neurons are modulated by dorsal root ganglion stimulation (DRGS) to provide pain relief. METHODS We modeled DRGS by coupling an anatomical finite element model of a human L5 dorsal root ganglion to biophysical models of primary sensory neurons. We calculated the stimulation amplitude needed to elicit an action potential in each neuron, and examined how DRGS affected sensory neuron activity. RESULTS We showed that within clinical ranges of stimulation parameters, DRGS drives the activity of large myelinated Aβ-fibers but does not directly activate small nonmyelinated C-fibers. We also showed that the position of the active and return electrodes and the polarity of the stimulus pulse influence neural activation. CONCLUSIONS Our results indicate that DRGS may provide pain relief by activating pain-gating mechanisms in the dorsal horn via repeated activation of large myelinated afferents. SIGNIFICANCE Understanding the mechanisms of action of DRGS-induced pain relief may lead to innovations in stimulation technologies that improve patient outcomes.
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Affiliation(s)
- Robert D Graham
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA; Biointerfaces Institute, University of Michigan, Ann Arbor, MI, USA
| | - Tim M Bruns
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA; Biointerfaces Institute, University of Michigan, Ann Arbor, MI, USA
| | - Bo Duan
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
| | - Scott F Lempka
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA; Biointerfaces Institute, University of Michigan, Ann Arbor, MI, USA; Department of Anesthesiology, University of Michigan, Ann Arbor, MI, USA.
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4
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Deer TR, Jain S, Hunter C, Chakravarthy K. Neurostimulation for Intractable Chronic Pain. Brain Sci 2019; 9:E23. [PMID: 30682776 PMCID: PMC6406470 DOI: 10.3390/brainsci9020023] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 01/15/2019] [Accepted: 01/21/2019] [Indexed: 12/20/2022] Open
Abstract
The field of neuromodulation has seen unprecedented growth over the course of the last decade with novel waveforms, hardware advancements, and novel chronic pain indications. We present here an updated review on spinal cord stimulation, dorsal root ganglion stimulation, and peripheral nerve stimulation. We focus on mechanisms of action, clinical indications, and future areas of research. We also present current drawbacks with current stimulation technology and suggest areas of future advancements. Given the current shortage of viable treatment options using a pharmacological based approach and conservative interventional therapies, neuromodulation presents an interesting area of growth and development for the interventional pain field and provides current and future practitioners a fresh outlook with regards to its place in the chronic pain treatment paradigm.
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Affiliation(s)
- Timothy R Deer
- Spine and Nerve Center of the Virginias, Charleston, VA 25301, USA.
| | - Sameer Jain
- Pain Treatment Centers of America, Little Rock, AR 72205, USA.
| | - Corey Hunter
- Ainsworth Institute of Pain Management, New York, NY 10022, USA.
| | - Krishnan Chakravarthy
- Department of Anesthesiology and Pain Medicine, University of California San Diego Health Sciences, San Diego, CA 92037, USA.
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Deer TR, Pope JE, Lamer TJ, Grider JS, Provenzano D, Lubenow TR, FitzGerald JJ, Hunter C, Falowski S, Sayed D, Baranidharan G, Patel NK, Davis T, Green A, Pajuelo A, Epstein LJ, Harned M, Liem L, Christo PJ, Chakravarthy K, Gilmore C, Huygen F, Lee E, Metha P, Nijhuis H, Patterson DG, Petersen E, Pilitsis JG, Rowe JJ, Rupert MP, Skaribas I, Sweet J, Verrills P, Wilson D, Levy RM, Mekhail N. The Neuromodulation Appropriateness Consensus Committee on Best Practices for Dorsal Root Ganglion Stimulation. Neuromodulation 2018; 22:1-35. [PMID: 30246899 DOI: 10.1111/ner.12845] [Citation(s) in RCA: 89] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 05/03/2018] [Accepted: 05/29/2018] [Indexed: 12/21/2022]
Abstract
INTRODUCTION The Neuromodulation Appropriateness Consensus Committee (NACC) is dedicated to improving the safety and efficacy of neuromodulation and thus improving the lives of patients undergoing neuromodulation therapies. With continued innovations in neuromodulation comes the need for evolving reviews of best practices. Dorsal root ganglion (DRG) stimulation has significantly improved the treatment of complex regional pain syndrome (CRPS), among other conditions. Through funding and organizational leadership by the International Neuromodulation Society (INS), the NACC reconvened to develop the best practices consensus document for the selection, implantation and use of DRG stimulation for the treatment of chronic pain syndromes. METHODS The NACC performed a comprehensive literature search of articles about DRG published from 1995 through June, 2017. A total of 2538 article abstracts were then reviewed, and selected articles graded for strength of evidence based on scoring criteria established by the US Preventive Services Task Force. Graded evidence was considered along with clinical experience to create the best practices consensus and recommendations. RESULTS The NACC achieved consensus based on peer-reviewed literature and experience to create consensus points to improve patient selection, guide surgical methods, improve post-operative care, and make recommendations for management of patients treated with DRG stimulation. CONCLUSION The NACC recommendations are intended to improve patient care in the use of this evolving therapy for chronic pain. Clinicians who choose to follow these recommendations may improve outcomes.
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Affiliation(s)
| | | | - Tim J Lamer
- Division of Pain Medicine, Department of Anesthesiology, Mayo Clinic, Rochester, MN, USA
| | - Jay S Grider
- UKHealthCare Pain Services, Department of Anesthesiology, University of Kentucky College of Medicine, Lexington, KY, USA
| | | | | | - James J FitzGerald
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, UK.,Nuffield Department of Surgical Sciences, University of Oxford, John Radcliffe Hospital, Oxford, UK
| | - Corey Hunter
- Ainsworth Institute of Pain Management, New York, NY, USA
| | - Steven Falowski
- Functional Neurosurgery, St. Lukes University Health Network, Bethlehem, PA, USA
| | - Dawood Sayed
- University of Kansas Medical Center, Kansas City, KS, USA
| | | | - Nikunj K Patel
- Institute of Clinical Neurosciences, Department of Neurosurgery, Southmead Hospital, University of Bristol, Bristol, UK
| | | | - Alex Green
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | | | | | - Michael Harned
- Department of Anesthesiology, University of Kentucky, Lexington, KY, USA
| | - Liong Liem
- St. Antonius Hospital, Nieuwegein, The Netherlands
| | | | | | | | - Frank Huygen
- Erasmus University Hospital, Rotterdam, The Netherlands
| | - Eric Lee
- Summit Pain Alliance, Santa Rosa, CA, USA
| | | | | | | | - Erika Petersen
- Department of Neurosurgery, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Julie G Pilitsis
- Neurosurgery and Neuroscience & Experimental Therapeutics, Albany Medical College, Albany, NY, USA
| | | | | | | | - Jennifer Sweet
- Case Western Reserve University, Stereotactic & Functional Neurosurgery, University Hospitals Cleveland Medical Center, Cleveland, OH, USA
| | | | - Derron Wilson
- Goodman Campbell Brain and Spine, Indiana University School of Medicine Department of Neurological Surgery, Indianapolis, IN, USA
| | | | - Nagy Mekhail
- Evidence-Based Pain Management Research and Education, Cleveland Clinic, Cleveland, OH, USA
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6
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Chen Y, Huang LYM. A simple and fast method to image calcium activity of neurons from intact dorsal root ganglia using fluorescent chemical Ca 2+ indicators. Mol Pain 2017; 13:1744806917748051. [PMID: 29212403 PMCID: PMC5731619 DOI: 10.1177/1744806917748051] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Chemical calcium indicators have been commonly used to monitor calcium (Ca2+) activity in cell bodies, i.e., somata, of isolated dorsal root ganglion neurons. Recent studies have shown that dorsal root ganglion somata play an essential role in soma–glia interactions and actively participate in the transmission of nociceptive signals. It is therefore desirable to develop methods to study Ca2+ activity in neurons and glia in intact dorsal root ganglia. In our previous studies, we found that incubation of intact dorsal root ganglia with acetoxymethyl dye resulted in efficient Ca2+ dye loading into glial cells but limited dye loading into neurons. Here, we introduce a useful method to load Ca2+ dyes in intact dorsal root ganglion neurons through electroporation. We found that electroporation greatly facilitated loading of Fluo-4 acetoxymethyl, Oregon green bapta-1-488 acetoxymethyl, and Fluo-4 pentapotassium salt into dorsal root ganglion neurons. In contrast, electroporation did not further facilitate dye loading into glia. Using electroporation followed by incubation of acetoxymethyl form Ca2+ dye, we can load acetoxymethyl Ca2+ dye well in both neurons and glia. With this approach, we found that inflammation induced by complete Freund’s adjuvant significantly increased the incidence of neuron–glia interactions in dorsal root ganglia. We also confirmed the actions of capsaicin and morphine on Ca2+ responses in dorsal root ganglion neurons. Thus, by promoting the loading of Ca2+ dye in neurons and glia through electroporation and incubation, Ca2+ activities in neurons and neuron–glia interactions can be well studied in intact dorsal root ganglia.
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Affiliation(s)
- Yong Chen
- 1 Department of Neuroscience, Cell Biology and Anatomy, 12338 University of Texas Medical Branch, Galveston , TX, USA
| | - Li-Yen M Huang
- 1 Department of Neuroscience, Cell Biology and Anatomy, 12338 University of Texas Medical Branch, Galveston , TX, USA
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7
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Bromodomain-containing Protein 4 Activates Voltage-gated Sodium Channel 1.7 Transcription in Dorsal Root Ganglia Neurons to Mediate Thermal Hyperalgesia in Rats. Anesthesiology 2017; 127:862-877. [DOI: 10.1097/aln.0000000000001809] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Abstract
Background
Bromodomain-containing protein 4 binds acetylated promoter histones and promotes transcription; however, the role of bromodomain-containing protein 4 in inflammatory hyperalgesia remains unclear.
Methods
Male Sprague–Dawley rats received hind paw injections of complete Freund’s adjuvant to induce hyperalgesia. The dorsal root ganglia were examined to detect changes in bromodomain-containing protein 4 expression and the activation of genes involved in the expression of voltage-gated sodium channel 1.7, which is a key pain-related ion channel.
Results
The intraplantar complete Freund’s adjuvant injections resulted in thermal hyperalgesia (4.0 ± 1.5 s; n = 7). The immunohistochemistry and immunoblotting results demonstrated an increase in the bromodomain-containing protein 4–expressing dorsal root ganglia neurons (3.78 ± 0.38 fold; n = 7) and bromodomain-containing protein 4 protein levels (2.62 ± 0.39 fold; n = 6). After the complete Freund’s adjuvant injection, histone H3 protein acetylation was enhanced in the voltage-gated sodium channel 1.7 promoter, and cyclin-dependent kinase 9 and phosphorylation of RNA polymerase II were recruited to this area. Furthermore, the voltage-gated sodium channel 1.7–mediated currents were enhanced in neurons of the complete Freund’s adjuvant rats (55 ± 11 vs. 19 ± 9 pA/pF; n = 4 to 6 neurons). Using bromodomain-containing protein 4–targeted antisense small interfering RNA to the complete Freund’s adjuvant–treated rats, the authors demonstrated a reduction in the expression of bromodomain-containing protein 4 (0.68 ± 0.16 fold; n = 7), a reduction in thermal hyperalgesia (7.5 ± 1.5 s; n = 7), and a reduction in the increased voltage-gated sodium channel 1.7 currents (21 ± 4 pA/pF; n = 4 to 6 neurons).
Conclusions
Complete Freund’s adjuvant triggers enhanced bromodomain-containing protein 4 expression, ultimately leading to the enhanced excitability of nociceptive neurons and thermal hyperalgesia. This effect is likely mediated by the enhanced expression of voltage-gated sodium channel 1.7.
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8
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Li X, Xu Q, He J. Spike propagation in axons under stretch growth conditions in cultured neurons from dorsal root ganglion. J Integr Neurosci 2017; 16:177-187. [PMID: 28891508 DOI: 10.3233/jin-170007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Computational software NEURON was used to simulate the stretch growth neurons in order to investigate the ability of dorsal root ganglion neurons to generate and propagate action potentials after a period of rapid axon stretch growth in vitro, and under what stimulating parameters can evoke action potentials. In the simulation, we found the stretch growth neuron had higher spike amplitude than from the static culture neuron in the soma and all axonal branch. In addition, the conduction velocity was also faster in the stretch growth axon. When the stimulating frequency was less than 15 Hz or the stimulating voltage was lower than 15 mV, no spike was evoked. Increasing stimulating frequency from 15 Hz to 5000 Hz or stimulating voltage from 15 mV to 100 mV had almost no effect on the spike amplitude. Interestingly, the first spike time and absolute refractory period (ARP) in different axonal branches and somas decreased stepwise with incremental increase in the stimulating frequency. It is concluded that the stretch growth neuron had higher amplitude and faster conduction velocity than the static culture neuron. In addition, some stimulating parameters had been analyzed in this study, which provided guidelines for electrophysiological experiments in future.
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Affiliation(s)
- Xiao Li
- Neural Interface and Rehabilitation Technology Research Center, Collaborative Innovation Center for Brain Science, College of Automation, Huazhong University of Science & Technology, Wuhan 430074, China
| | - Qi Xu
- Neural Interface and Rehabilitation Technology Research Center, Collaborative Innovation Center for Brain Science, College of Automation, Huazhong University of Science & Technology, Wuhan 430074, China
| | - Jiping He
- Neural Interface and Rehabilitation Technology Research Center, Collaborative Innovation Center for Brain Science, College of Automation, Huazhong University of Science & Technology, Wuhan 430074, China
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9
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Du X, Hao H, Yang Y, Huang S, Wang C, Gigout S, Ramli R, Li X, Jaworska E, Edwards I, Deuchars J, Yanagawa Y, Qi J, Guan B, Jaffe DB, Zhang H, Gamper N. Local GABAergic signaling within sensory ganglia controls peripheral nociceptive transmission. J Clin Invest 2017; 127:1741-1756. [PMID: 28375159 PMCID: PMC5409786 DOI: 10.1172/jci86812] [Citation(s) in RCA: 110] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 02/02/2017] [Indexed: 01/05/2023] Open
Abstract
The integration of somatosensory information is generally assumed to be a function of the central nervous system (CNS). Here we describe fully functional GABAergic communication within rodent peripheral sensory ganglia and show that it can modulate transmission of pain-related signals from the peripheral sensory nerves to the CNS. We found that sensory neurons express major proteins necessary for GABA synthesis and release and that sensory neurons released GABA in response to depolarization. In vivo focal infusion of GABA or GABA reuptake inhibitor to sensory ganglia dramatically reduced acute peripherally induced nociception and alleviated neuropathic and inflammatory pain. In addition, focal application of GABA receptor antagonists to sensory ganglia triggered or exacerbated peripherally induced nociception. We also demonstrated that chemogenetic or optogenetic depolarization of GABAergic dorsal root ganglion neurons in vivo reduced acute and chronic peripherally induced nociception. Mechanistically, GABA depolarized the majority of sensory neuron somata, yet produced a net inhibitory effect on the nociceptive transmission due to the filtering effect at nociceptive fiber T-junctions. Our findings indicate that peripheral somatosensory ganglia represent a hitherto underappreciated site of somatosensory signal integration and offer a potential target for therapeutic intervention.
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Affiliation(s)
- Xiaona Du
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Shijiazhuang, China
| | - Han Hao
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Shijiazhuang, China
| | - Yuehui Yang
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Shijiazhuang, China
| | - Sha Huang
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Shijiazhuang, China
| | - Caixue Wang
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Shijiazhuang, China
| | - Sylvain Gigout
- Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Rosmaliza Ramli
- Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
- School of Dental Sciences, Universiti Sains Malaysia, Kelantan, Malaysia
| | - Xinmeng Li
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Shijiazhuang, China
| | - Ewa Jaworska
- Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Ian Edwards
- Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Jim Deuchars
- Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Yuchio Yanagawa
- Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine and Japan Science and Technology Agency, CREST, Maebashi, Japan
| | - Jinlong Qi
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Shijiazhuang, China
| | - Bingcai Guan
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Shijiazhuang, China
| | - David B. Jaffe
- Department of Biology, UTSA Neurosciences Institute, University of Texas at San Antonio, San Antonio, Texas, USA
| | - Hailin Zhang
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Shijiazhuang, China
| | - Nikita Gamper
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Shijiazhuang, China
- Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
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10
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Gong K, Ohara PT, Jasmin L. Patch Clamp Recordings on Intact Dorsal Root Ganglia from Adult Rats. J Vis Exp 2016. [PMID: 27768031 DOI: 10.3791/54287] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Patch clamp studies from dorsal root ganglia (DRGs) neurons have increased our understanding of the peripheral nervous system. Currently, the majority of recordings are conducted on dissociated DRG neurons, which is a standard preparation for most laboratories. Neuronal properties, however, can be altered by axonal injury resulting from enzyme digestion used in acquiring dissociated neurons. Further, dissociated neuron preparations cannot fully represent the microenvironment of the DRG since loss of contact with satellite glial cells that surround the primary sensory neurons is an unavoidable consequence of this method. To overcome the limitations in using conventional dissociated DRG neurons for patch clamp recordings, in this report we describe a method to prepare intact DRGs and conduct patch clamp recordings on individual primary sensory neurons ex vivo. This approach permits the fast and straightforward preparation of intact DRGs, mimicking in vivo conditions by keeping DRG neurons associated with their surrounding satellite glial cells and basement membrane. Furthermore, the method avoids axonal injury from manipulation and enzyme digestion such as when dissociating DRGs. This ex vivo preparation can additionally be used to study the interaction between primary sensory neurons and satellite glial cells.
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Affiliation(s)
- Kerui Gong
- Department of Oral and Maxillofacial Surgery, University of California, San Francisco;
| | - Peter T Ohara
- Department of Anatomy, University of California, San Francisco
| | - Luc Jasmin
- Department of Oral and Maxillofacial Surgery, University of California, San Francisco;
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11
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Tanaka Y, Niwa S, Dong M, Farkhondeh A, Wang L, Zhou R, Hirokawa N. The Molecular Motor KIF1A Transports the TrkA Neurotrophin Receptor and Is Essential for Sensory Neuron Survival and Function. Neuron 2016; 90:1215-1229. [DOI: 10.1016/j.neuron.2016.05.002] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Revised: 03/12/2016] [Accepted: 04/28/2016] [Indexed: 01/10/2023]
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12
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Ciglieri E, Ferrini F, Boggio E, Salio C. An improved method for in vitro morphofunctional analysis of mouse dorsal root ganglia. Ann Anat 2016; 207:62-7. [PMID: 27224901 DOI: 10.1016/j.aanat.2016.04.032] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 03/17/2016] [Accepted: 04/21/2016] [Indexed: 12/11/2022]
Abstract
Sensory neurons in dorsal root ganglia (DRGs) are the first-order neurons along the pathway conveying sensory information from the periphery to the central nervous system. The analysis of the morphological and physiological features of these neurons and their alterations in pathology is the necessary prerequisite to understand pain encoding mechanisms. Here, we describe an in vitro procedure for combined morphofunctional analysis of mouse DRGs. Freshly excised DRGs obtained from adult mice were incubated in collagenase to dissolve the ensheathing connective capsule. The degradation of the connective tissue facilitates both access to the neurons by classical recording glass pipettes and the penetration of primary antibodies for immunohistochemical procedures. The entire DRGs were then imaged using a confocal microscope obtaining a fine 3D representation of their cytoarchitecture without requiring tissue sectioning. Thus, our proposed whole-mount preparation represents a flexible in vitro approach for both functional and phenotypic analysis of DRG neurons by at the same time preserving their neuroanatomical relationships.
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Affiliation(s)
- E Ciglieri
- Department of Veterinary Sciences, University of Turin, Largo Braccini 2, 10095 Grugliasco, TO, Italy
| | - F Ferrini
- Department of Veterinary Sciences, University of Turin, Largo Braccini 2, 10095 Grugliasco, TO, Italy
| | - E Boggio
- Department of Veterinary Sciences, University of Turin, Largo Braccini 2, 10095 Grugliasco, TO, Italy
| | - C Salio
- Department of Veterinary Sciences, University of Turin, Largo Braccini 2, 10095 Grugliasco, TO, Italy.
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13
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Sundt D, Gamper N, Jaffe DB. Spike propagation through the dorsal root ganglia in an unmyelinated sensory neuron: a modeling study. J Neurophysiol 2015; 114:3140-53. [PMID: 26334005 PMCID: PMC4686302 DOI: 10.1152/jn.00226.2015] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 08/30/2015] [Indexed: 12/31/2022] Open
Abstract
Unmyelinated C-fibers are a major type of sensory neurons conveying pain information. Action potential conduction is regulated by the bifurcation (T-junction) of sensory neuron axons within the dorsal root ganglia (DRG). Understanding how C-fiber signaling is influenced by the morphology of the T-junction and the local expression of ion channels is important for understanding pain signaling. In this study we used biophysical computer modeling to investigate the influence of axon morphology within the DRG and various membrane conductances on the reliability of spike propagation. As expected, calculated input impedance and the amplitude of propagating action potentials were both lowest at the T-junction. Propagation reliability for single spikes was highly sensitive to the diameter of the stem axon and the density of voltage-gated Na+ channels. A model containing only fast voltage-gated Na+ and delayed-rectifier K+ channels conducted trains of spikes up to frequencies of 110 Hz. The addition of slowly activating KCNQ channels (i.e., KV7 or M-channels) to the model reduced the following frequency to 30 Hz. Hyperpolarization produced by addition of a much slower conductance, such as a Ca2+-dependent K+ current, was needed to reduce the following frequency to 6 Hz. Attenuation of driving force due to ion accumulation or hyperpolarization produced by a Na+-K+ pump had no effect on following frequency but could influence the reliability of spike propagation mutually with the voltage shift generated by a Ca2+-dependent K+ current. These simulations suggest how specific ion channels within the DRG may contribute toward therapeutic treatments for chronic pain.
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Affiliation(s)
- Danielle Sundt
- Department of Biology, UTSA Neurosciences Institute, University of Texas at San Antonio, San Antonio, Texas
| | - Nikita Gamper
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, People's Republic of China; and Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - David B Jaffe
- Department of Biology, UTSA Neurosciences Institute, University of Texas at San Antonio, San Antonio, Texas;
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14
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Du X, Hao H, Gigout S, Huang D, Yang Y, Li L, Wang C, Sundt D, Jaffe DB, Zhang H, Gamper N. Control of somatic membrane potential in nociceptive neurons and its implications for peripheral nociceptive transmission. Pain 2014; 155:2306-22. [PMID: 25168672 PMCID: PMC4247381 DOI: 10.1016/j.pain.2014.08.025] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Revised: 08/02/2014] [Accepted: 08/19/2014] [Indexed: 01/10/2023]
Abstract
Peripheral sensory ganglia contain somata of afferent fibres conveying somatosensory inputs to the central nervous system. Growing evidence suggests that the somatic/perisomatic region of sensory neurons can influence peripheral sensory transmission. Control of resting membrane potential (Erest) is an important mechanism regulating excitability, but surprisingly little is known about how Erest is regulated in sensory neuron somata or how changes in somatic/perisomatic Erest affect peripheral sensory transmission. We first evaluated the influence of several major ion channels on Erest in cultured small-diameter, mostly capsaicin-sensitive (presumed nociceptive) dorsal root ganglion (DRG) neurons. The strongest and most prevalent effect on Erest was achieved by modulating M channels, K2P and 4-aminopiridine-sensitive KV channels, while hyperpolarization-activated cyclic nucleotide-gated, voltage-gated Na+, and T-type Ca2+ channels to a lesser extent also contributed to Erest. Second, we investigated how varying somatic/perisomatic membrane potential, by manipulating ion channels of sensory neurons within the DRG, affected peripheral nociceptive transmission in vivo. Acute focal application of M or KATP channel enhancers or a hyperpolarization-activated cyclic nucleotide-gated channel blocker to L5 DRG in vivo significantly alleviated pain induced by hind paw injection of bradykinin. Finally, we show with computational modelling how somatic/perisomatic hyperpolarization, in concert with the low-pass filtering properties of the t-junction within the DRG, can interfere with action potential propagation. Our study deciphers a complement of ion channels that sets the somatic Erest of nociceptive neurons and provides strong evidence for a robust filtering role of the somatic and perisomatic compartments of peripheral nociceptive neuron.
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Affiliation(s)
- Xiaona Du
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, PR China.
| | - Han Hao
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, PR China
| | - Sylvain Gigout
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, Leeds, UK
| | - Dongyang Huang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, PR China
| | - Yuehui Yang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, PR China
| | - Li Li
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, PR China
| | - Caixue Wang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, PR China
| | - Danielle Sundt
- Department of Biology, University of Texas at San Antonio, San Antonio, TX, USA
| | - David B Jaffe
- Department of Biology, University of Texas at San Antonio, San Antonio, TX, USA
| | - Hailin Zhang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, PR China
| | - Nikita Gamper
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, PR China; Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, Leeds, UK.
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15
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Lu XL, Xu WX, Yan ZY, Qian Z, Xu B, Liu Y, Han LM, Gao RC, Li JN, Yuan M, Zhao CB, Qiao GF, Li BY. Subtype identification in acutely dissociated rat nodose ganglion neurons based on morphologic parameters. Int J Biol Sci 2013; 9:716-27. [PMID: 23904796 PMCID: PMC3729014 DOI: 10.7150/ijbs.7006] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Accepted: 07/01/2013] [Indexed: 01/04/2023] Open
Abstract
Nodose ganglia are composed of A-, Ah- and C-type neurons. Despite their important roles in regulating visceral afferent function, including cardiovascular, pulmonary, and gastrointestinal homeostasis, information about subtype-specific expression, molecular identity, and function of individual ion transporting proteins is scarce. Although experiments utilizing the sliced ganglion preparation have provided valuable insights into the electrophysiological properties of nodose ganglion neuron subtypes, detailed characterization of their electrical phenotypes will require measurements in isolated cells. One major unresolved problem, however, is the difficulty to unambiguously identify the subtype of isolated nodose ganglion neurons without current-clamp recording, because the magnitude of conduction velocity in the corresponding afferent fiber, a reliable marker to discriminate subtypes in situ, can no longer be determined. Here, we present data supporting the notion that application of an algorithm regarding to microscopic structural characteristics, such as neuron shape evaluated by the ratio between shortest and longest axis, neuron surface characteristics, like membrane roughness, and axon attachment, enables specific and sensitive subtype identification of acutely dissociated rat nodose ganglion neurons, by which the accuracy of identification is further validated by electrophysiological markers and overall positive predictive rates is 89.26% (90.04%, 76.47%, and 98.21% for A-, Ah, and C-type, respectively). This approach should aid in gaining insight into the molecular correlates underlying phenotypic heterogeneity of nodose ganglia. Additionally, several critical points that help for neuron identification and afferent conduction calibration are also discussed.
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Affiliation(s)
- Xiao-Long Lu
- Department of Pharmacology, Harbin Medical University, Harbin, China
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16
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Fan N, Donnelly DF, LaMotte RH. Chronic compression of mouse dorsal root ganglion alters voltage-gated sodium and potassium currents in medium-sized dorsal root ganglion neurons. J Neurophysiol 2011; 106:3067-72. [PMID: 21917996 DOI: 10.1152/jn.00752.2011] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Chronic compression (CCD) of the dorsal root ganglion (DRG) is a model of human radicular pain produced by intraforaminal stenosis and other disorders affecting the DRG, spinal nerve, or root. Previously, we examined electrophysiological changes in small-diameter lumbar level 3 (L3) and L4 DRG neurons treated with CCD; the present study extends these observations to medium-sized DRG neurons, which mediate additional sensory modalities, both nociceptive and non-nociceptive. Whole-cell patch-clamp recordings were obtained from medium-sized somata in the intact DRG in vitro. Compared with neurons from unoperated control animals, CCD neurons exhibited a decrease in the current threshold for action potential generation. In the CCD group, current densities of TTX-resistant and TTX-sensitive Na(+) current were increased, whereas the density of delayed rectifier voltage-dependent K(+) current was decreased. No change was observed in the transient or "A" current after CCD. We conclude that CCD in the mouse produces hyperexcitability in medium-sized DRG neurons, and the hyperexcitability is associated with an increased density of Na(+) current and a decreased density of delayed rectifier voltage-dependent K(+) current.
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Affiliation(s)
- Ni Fan
- Department of Anesthesiology, Yale University School of Medicine, 333 Cedar St., P.O. 208051, New Haven, CT 06520, USA
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17
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Donnelly DF. Developmental changes in the magnitude and activation characteristics of Na(+) currents of petrosal neurons projecting to the carotid body. Respir Physiol Neurobiol 2011; 177:284-93. [PMID: 21596159 DOI: 10.1016/j.resp.2011.05.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Revised: 04/11/2011] [Accepted: 05/03/2011] [Indexed: 12/15/2022]
Abstract
Carotid bodies mediate hypoxia sensing for the respiratory system and increase their sensitivity in the post-natal period. The present study examined the characteristics and developmental change of fast Na(+) currents of chemoreceptor afferent neurons. Rat carotid bodies (P2-P19) were harvested intact with the petrosal ganglia and whole-cell recordings obtained from petrosal somas whose axons projected to the carotid body. The magnitude of Na(+) current increased in the post-natal period in parallel with increased conduction velocity and somal size. Voltage-dependence of activation significantly shifted towards negative potentials but no significant change occurred in the voltage dependence of inactivation or the slope factors for activation or inactivation. The leftward shift in activation increased slowly or non-inactivating currents around resting potential which increases afferent neuron excitability, a result confirmed in current clamp recordings. These results suggest that a developmental shift in Na(+) current activation plays a role in chemoreceptor maturation by enhancing excitability of the afferent neuron.
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Affiliation(s)
- David F Donnelly
- Department of Pediatrics, Division of Respiratory Medicine, Yale University School of Medicine, 333 Cedar St., New Haven, CT 06520, USA.
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18
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Fan N, Sikand P, Donnelly DF, Ma C, Lamotte RH. Increased Na+ and K+ currents in small mouse dorsal root ganglion neurons after ganglion compression. J Neurophysiol 2011; 106:211-8. [PMID: 21525373 DOI: 10.1152/jn.00065.2011] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
We investigated the effects of chronic compression (CCD) of the L3 and L4 dorsal root ganglion (DRG) on pain behavior in the mouse and on the electrophysiological properties of the small-diameter neuronal cell bodies in the intact ganglion. CCD is a model of human radicular pain produced by intraforaminal stenosis and other disorders affecting the DRG, spinal nerve, or root. On days 1, 3, 5, and 7 after the onset of compression, there was a significant decrease from preoperative values in the threshold mechanical force required to elicit a withdrawal of the foot ipsilateral to the CCD (tactile allodynia). Whole cell patch-clamp recordings were obtained, in vitro, from small-sized somata and, for the first time, in the intact DRG. Under current clamp, CCD neurons exhibited a significantly lower rheobase compared with controls. A few CCD but no control neurons exhibited spontaneous action potentials. CCD neurons showed an increase in the density of TTX-resistant and TTX-sensitive Na(+) current. CCD neurons also exhibited an enhanced density of voltage-dependent K(+) current, due to an increase in delayed rectifier K(+) current, without a change in the transient or "A" current. We conclude that CCD in the mouse produces a model of radicular pain, as we have previously demonstrated in the rat. While the role of enhanced K(+) current remains to be elucidated, we speculate that it represents a compensatory neuronal response to reduce ectopic or aberrant levels of neuronal activity produced by the injury.
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Affiliation(s)
- Ni Fan
- Department of Anesthesiology, Yale University School of Medicine, New Haven, Connecticut 06510, USA
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19
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Ma C, Donnelly DF, LaMotte RH. In vivo visualization and functional characterization of primary somatic neurons. J Neurosci Methods 2010; 191:60-5. [PMID: 20558205 DOI: 10.1016/j.jneumeth.2010.06.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2010] [Revised: 06/04/2010] [Accepted: 06/04/2010] [Indexed: 11/28/2022]
Abstract
In vivo electrophysiological recordings from cell bodies of primary sensory neurons are used to determine sensory function but are commonly performed blindly and without access to voltage- (patch-clamp) electrophysiology or optical imaging. We present a procedure to visualize and patch-clamp the neuronal cell body in the dorsal root ganglion, in vivo, manipulate its chemical environment, determine its receptive field properties, and remove it either to obtain subsequent molecular analyses or to gain access to deeper lying cells. This method allows the association of the peripheral transduction capacities of a sensory neuron with the biophysical and chemical characteristics of its cell body.
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Affiliation(s)
- Chao Ma
- Department of Anesthesiology, Yale University School of Medicine, 333 Cedar St., New Haven, CT 06510, USA.
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20
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Hayar A, Gu C, Al-Chaer ED. An improved method for patch clamp recording and calcium imaging of neurons in the intact dorsal root ganglion in rats. J Neurosci Methods 2008; 173:74-82. [PMID: 18588915 DOI: 10.1016/j.jneumeth.2008.05.023] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2008] [Revised: 04/30/2008] [Accepted: 05/19/2008] [Indexed: 10/22/2022]
Abstract
The properties of dorsal root ganglion (DRG) neurons have been mostly investigated in culture of dissociated cells, and it is uncertain whether these cells maintain the electrophysiological properties of the intact DRG neurons. Few attempts have been made to record from DRG neurons in the intact ganglion using the patch clamp technique. In this study, rat DRGs were dissected and incubated for at least 1h at 37 degrees C in collagenase (10mg/ml). We used oblique epi-illumination to visualize DRG neurons and perform patch clamp recordings. All DRG neurons exhibited strong delayed rectifier potassium current and a high threshold for spike generation (-15 mV) that rendered the cells very weakly excitable, generating only one action potential upon strong current injection (>300 pA). It is therefore possible that cultured DRG neurons, commonly used in studies of pain processing, may be hyperexcitable because they acquired "neuropathic" properties due to the injury induced by their dissociation. Electrical stimulation of the attached root produced an antidromic spike in the soma that could be blocked by intracellular hyperpolarization or high frequency stimulation. Imaging intracellular calcium concentration with Oregon Green BAPTA-1 indicates that antidromic stimulation caused a long-lasting increase in intracellular calcium concentration mostly near the cell membrane. This study describes a simple approach to examine the electrophysiological and pharmacological properties and intracellular calcium signaling in DRG neurons in the intact ganglion where the effects of somatic spike invasion can be studied as well.
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Affiliation(s)
- Abdallah Hayar
- Center for Translational Neuroscience, Department of Neurobiology and Developmental Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, United States.
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21
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Abstract
Our knowledge of the ion channels, receptors and signalling mechanisms involved in pain pathophysiology, and which specific channels play a role in subtypes of pain such as neuropathic and inflammatory pain, has expanded considerably in recent years. It is now clear that in the neuropathic state the expression of certain channels is modified, and that these changes underlie the plasticity of responses that occur to generate inappropriate pain signals from normally trivial inputs. Pain is modulated by a subset of the voltage-gated sodium channels, including Nav1.3, Nav1.7, Nav1.8 and Nav1.9. These isoforms display unique expression patterns within specific tissues, and are either up- or down-regulated upon injury to the nervous system. Here we describe our current understanding of the roles of sodium channels in pain and nociceptive information processing, with a particular emphasis on neuropathic pain and drugs useful for the treatment of neuropathic pain that act through mechanisms involving block of sodium channels. One of the future challenges in the development of novel sodium channel blockers is to design and synthesise isoform-selective channel inhibitors. This should provide substantial benefits over existing pain treatments.
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Affiliation(s)
- Marc Rogers
- Xention Ltd., Iconix Park, Pampisford, Cambridge CB2 4EF, United Kingdom
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22
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Smith FL, Lindsay RJ. Enhancement of bupivacaine local anesthesia with the potassium channel blocker ibutilide. Eur J Pain 2006; 11:551-6. [PMID: 16919981 DOI: 10.1016/j.ejpain.2006.07.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2005] [Revised: 06/16/2006] [Accepted: 07/10/2006] [Indexed: 11/18/2022]
Abstract
In some clinical settings it is necessary to inject large volumes of local anesthetic--and consequently very high doses--in order to provide an adequate level of block. Subsequent absorption of these high doses, or inadvertent intravenous administration of even small doses, has led to systemic toxicity. Thus, it is desirable to develop adjuvants that are inert alone, but would enhance the potency and/or efficacy of local anesthetics to improve their safety. Adelta/C fibers possess K(+) channels identified as sustained delayed rectifier type K(DR) currents and transient A-type K(A) currents. In the heart, the class III antiarrhythmic drug ibutilide blocks the cardiac component of the rapid delayed rectifying K(+) current (IKr). Experiments were conducted to determine whether co-administration of the K(+) channel blocker ibutilide would enhance the local anesthetic bupivacaine in mice. After injecting bupivacaine mixed with vehicle or ibutilide in the popliteal region of mice, paw withdrawal latencies were determined by applying the plantar aspect of a single hind-paw to the surface a 55 degrees C hot-plate device. 0.5% Bupivacaine+ibutilide (7.8x10(-5) M) elicited significantly longer hot-plate latencies than 0.5% bupivacaine+vehicle. In addition, bupivacaine was 2.6-fold more potent when co-administered with ibutilide rather than vehicle. Epinephrine extends the tissue concentrations of local anesthetics by inducing localized vasoconstriction. Epinephrine augmented the enhancement by ibutilide of bupivacaine's potency by 6.8-fold. In summary, ibutilide may enhance the effects of bupivacaine by blocking K(+) channels on sensory nociceptive nerves.
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Affiliation(s)
- Forrest L Smith
- Department of Pharmacology and Toxicology, Virginia Commonwealth University Medical Center, P.O. Box 980524, Richmond, VA 23298-0524, USA.
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23
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Faustino EVS, Donnelly DF. An important functional role of persistent Na+ current in carotid body hypoxia transduction. J Appl Physiol (1985) 2006; 101:1076-84. [PMID: 16778007 DOI: 10.1152/japplphysiol.00090.2006] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Systemic hypoxia in mammals is sensed and transduced by the carotid body into increased action potential (AP) frequency on the sinus nerve, resulting in increased ventilation. The mechanism of hypoxia transduction is not resolved, but previous work suggested that fast Na(+) channels play an important role in determining the rate and timing of APs (Donnelly, DF, Panisello JM, and Boggs D. J Physiol. 511: 301-311, 1998). We speculated that Na(+) channel activity between APs, termed persistent Na(+) current (I(NaP)), is responsible for AP generation that and riluzole and phenytoin, which inhibit this current, would impair organ function. Using whole cell patch clamp recording of intact petrosal neurons with projections to the carotid body, we demonstrated that I(NaP) is present in chemoreceptor afferent neurons and is inhibited by riluzole. Furthermore, discharge frequencies of single-unit, chemoreceptor activity, in vitro, during normoxia (Po(2) 150 Torr) and during acute hypoxia (Po(2) 90 Torr) were significantly reduced by riluzole concentrations at or above 5 microM, and by phenytoin at 100 microM, without significant affect on nerve conduction time, AP magnitude (inferred from extracellular field), and AP duration. The effect of both drugs appeared solely postsynaptic because hypoxia-induced catecholamine release in the carotid body was not altered by either drug. The respiratory response of unanesthetized, unrestrained 2-wk-old rats to acute hypoxia (12% inspired O(2) fraction), which was measured with whole body plethysmography, was significantly reduced after treatment with riluzole (2 mg/kg ip) and phenytoin (20 mg/kg ip). We conclude that I(NaP) is present in chemoreceptor afferent neurons and serves an important role in peripheral chemoreceptor function and, hence, in the ventilatory response to hypoxia.
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Affiliation(s)
- Edward Vincent S Faustino
- Department of Pediatrics, Section of Critical Care and Applied Physiology, Yale University School of Medicine, 333 Cedar St., PO Box 208064, New Haven, CT 06520-8064, USA.
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24
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Passmore GM. Dorsal root ganglion neurones in culture: a model system for identifying novel analgesic targets? J Pharmacol Toxicol Methods 2005; 51:201-8. [PMID: 15862465 DOI: 10.1016/j.vascn.2004.08.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/25/2004] [Indexed: 02/02/2023]
Abstract
Ion channels represent attractive targets in the development of novel analgesics for the treatment of pain. Dorsal root ganglion (DRG) neurones in culture can share characteristics with nociceptors in vivo and are frequently used to investigate the ion channels that underlie the transduction of noxious stimuli into electrical activity during sensory processing. In this article, I describe the methods used to prepare cultures of DRG neurones including the procedures for the dissection, enzymatic dissociation and plating. The criteria used to identify putative nociceptors in vitro are reviewed and using the M-current as an example I highlight how potential analgesic targets can be identified by combining the use of the voltage clamp technique with the use of selective pharmacological agents.
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Affiliation(s)
- Gayle M Passmore
- Department of Pharmacology, University College London, London, WC1E 6BT, United Kingdom.
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25
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Dalkilic N, Kiziltan E, Pehlivan F, Kose K. Does Collagenase Affect the Electrophysiological Parameters of Nerve Trunk? YAKUGAKU ZASSHI 2003; 123:1031-7. [PMID: 14689866 DOI: 10.1248/yakushi.123.1031] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Collegenase is widely used in the process of teasing a nerve in order to perform single fiber action potential (SFAP) recordings. In this study, the effects of collagenase on nerve conduction parameters were investigated. To accomplish this, normal compound action potentials (nCAPs) were recorded from isolated frog sciatic nerve at various distances using the suction technique. Then, the same nerve was treated with collagenased Ringer's solution (3.5 mg/ml, Sigma Type XI) for 90 minutes and action potentials (cCAPs) were recorded again. Numerical analysis of these records was performed and the results were compared. Using the nCAP and cCAP recordings, the conduction velocity distributions (CVD) of the individual nerve trunks were determined by a method that we have previously described. Statistical results indicated significant differences (p < 0.05) between the nCAP and cCAP CVD data. From these findings it is concluded that, when used for teasing the nerve fibers, collagenase may affect the nerve trunk conduction parameters. Specifically, a significant amount of decrease has been observed in conduction velocities of myelinated fibers having diameters smaller than 8 microns.
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Affiliation(s)
- Nizamettin Dalkilic
- Biophysics Department, Medical Faculty, Selçuk University, 42080, Konya, Turkey.
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26
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Smith FL, Lindsay RJ. Paradoxical enhancement of bupivacaine anesthesia in mice by drugs that open sodium channels. Pharmacology 2003; 67:90-8. [PMID: 12566853 DOI: 10.1159/000067739] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2002] [Accepted: 06/05/2002] [Indexed: 11/19/2022]
Abstract
Sodium channel drugs were used to modulate the anesthetic effects of bupivacaine in mice. Anesthesia was measured following perisciatic injection of bupivacaine with vehicle or neurotoxin in the popliteal region. The site 1 Na(+) channel blocker tetrodotoxin alone was inactive, but increased the anesthetic effects of bupivacaine. We hypothesized that the site 2 and site 3 Na(+) channel openers veratridine and anemone toxin II (ATXII), respectively, would antagonize bupivacaine. Paradoxically, both drugs enhanced bupivacaine. In bupivacaine-treated mice, a significant correlation was observed between limb weakness scores and paw withdrawal latencies. The correlation coefficients were higher when tetrodotoxin, veratridine, or ATXII was coadministered with bupivacaine. In conclusion, veratridine and ATXII may have increased the stimulus-dependent binding of bupivacaine to Na(+) channels, thereby increasing the anesthetic effects of bupivacaine.
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Affiliation(s)
- Forrest L Smith
- Department of Pharmacology and Toxicology, Virginia Commonwealth University School of Medicine, Richmond, Va 23298-0613, USA.
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27
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Abstract
The patch clamp technique is widely utilized for studying the electrophysiological properties of enzymatically isolated sensory neurons. Unfortunately, dissociation of the ganglion severs the afferent fibers. As a result, isolated neurons can only be broadly categorized according to somatic action potential waveforms, ion channel subtypes, chemical sensitivities and cell diameter. Such restricted classifications contrast with the continuum of conduction velocities (CVs), discharge patterns, sensory modalities and functional properties of visceral and spinal afferents. Previous reports of patch clamp recordings using intact ganglion have been limited to young animal preparations. This raises concerns regarding postnatal development and impedes the use of chronic models of disease or injury, which often necessitate the use of a more mature animal preparation. Here, we present a methodology for preparing nodose ganglion from adult rat (250-400 g) for study using the patch clamp technique. Successful whole cell recordings were obtained from approximately 50% of the cells selected for study, the majority of which had intact afferent fibers. Measures of somatic discharge and afferent fiber CV at both room and physiological temperatures were consistent with investigations using sharp microelectrodes. Voltage clamp recordings of whole cell Na(+), Ca(2+) and K(+) ion channel currents were comparable to those obtained using isolated neuron preparations. The ability to classify voltage- and ligand-gated ion channel type with afferent fiber CV in an adult preparation adds a valuable new dimension to cellular investigations of the diverse functional and chemical properties of the peripheral afferent nervous system.
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Affiliation(s)
- B Y Li
- Biomedical Engineering Program, Purdue School of Engineering and Technology, Indiana University, Room SL 174, 723 West Michigan Street, Indianapolis, IN 46202, USA
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28
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Viana F, de la Peña E, Pecson B, Schmidt RF, Belmonte C. Swelling-activated calcium signalling in cultured mouse primary sensory neurons. Eur J Neurosci 2001; 13:722-34. [PMID: 11207807 DOI: 10.1046/j.0953-816x.2000.01441.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The effects of hypo-osmotic membrane stretch on intracellular calcium concentration ([Ca(2+)](i)), cell volume and cellular excitability were investigated in cultured mouse primary sensory trigeminal neurons. Hypotonic solutions (15--45%) led to rapid cell swelling in all neurons. Swelling was accompanied by dose-dependent elevations in [Ca(2+)](i) in a large fraction of neurons. Responses could be classified into three categories. (i) In 57% of the neurons [Ca(2+)](i) responses had a slow rise time and were generally of small amplitude. (ii) In 21% of the neurons, responses had a faster rise and were larger in amplitude. (iii) The remaining cells (22%) did not show [Ca(2+)](i) responses to hypo-osmotic stretch. Slow and fast [Ca(2+)](i) changes were observed in trigeminal neurons of different sizes with variable responses to capsaicin (0.5 microM). The swelling-induced [Ca(2+)](i) responses were not abolished after depletion of intracellular Ca2+ stores with cyclopiazonic acid or preincubation in thapsigargin, but were suppressed in the absence of external Ca(2+). They were strongly attenuated by extracellular nickel and gadolinium. Hypotonic stimulation led to a decrease in input resistance and to membrane potential depolarization. Under voltage-clamp, the [Ca(2+)](i) elevation produced by hypotonic stimulation was accompanied by the development of an inward current and a conductance increase. The time course and amplitude of the [Ca(2+)](i) response to hypo-osmotic stimulation showed a close correlation with electrophysiological properties of the neurons. Fast [Ca(2+)](i) responses were characteristic of trigeminal neurons with short duration action potentials and marked inward rectification. These findings suggest that hypo-osmotic stimulation activates several Ca(2+)-influx pathways, including Gd(3+)-sensitive stretch-activated ion channels, in a large fraction of trigeminal ganglion neurons. Opening of voltage-gated Ca(2+) channels also contributes to the response. The pattern and rate of Ca(2+) influx may be correlated with functional subtypes of sensory neurons.
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Affiliation(s)
- F Viana
- Instituto de Neurociencias, Universidad Miguel Hernández-CSIC, Apartado 18, San Juan de Alicante 03550, Spain.
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