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Obergrussberger A, Haarmann C, Rinke I, Becker N, Guinot D, Brueggemann A, Stoelzle‐Feix S, George M, Fertig N. Automated Patch Clamp Analysis of nAChα7 and Na
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1.7 Channels. ACTA ACUST UNITED AC 2014; 65:11.13.1-48. [DOI: 10.1002/0471141755.ph1113s65] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Estacion M, O'Brien JE, Conravey A, Hammer MF, Waxman SG, Dib-Hajj SD, Meisler MH. A novel de novo mutation of SCN8A (Nav1.6) with enhanced channel activation in a child with epileptic encephalopathy. Neurobiol Dis 2014; 69:117-23. [PMID: 24874546 DOI: 10.1016/j.nbd.2014.05.017] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Revised: 04/21/2014] [Accepted: 05/17/2014] [Indexed: 10/25/2022] Open
Abstract
Rare de novo mutations of sodium channels are thought to be an important cause of sporadic epilepsy. The well established role of de novo mutations of sodium channel SCN1A in Dravet Syndrome supports this view, but the etiology of many cases of epileptic encephalopathy remains unknown. We sought to identify the genetic cause in a patient with early onset epileptic encephalopathy by whole exome sequencing of genomic DNA. The heterozygous mutation c. 2003C>T in SCN8A, the gene encoding sodium channel Nav1.6, was detected in the patient but was not present in either parent. The resulting missense substitution, p.Thr767Ile, alters an evolutionarily conserved residue in the first transmembrane segment of channel domain II. The electrophysiological effects of this mutation were assessed in neuronal cells transfected with mutant or wildtype cDNA. The mutation causes enhanced channel activation, with a 10mV depolarizing shift in voltage dependence of activation as well as increased ramp current. In addition, pyramidal hippocampal neurons expressing the mutant channel exhibit increased spontaneous firing with PDS-like complexes as well as increased frequency of evoked action potentials. The identification of this new gain-of-function mutation of Nav1.6 supports the inclusion of SCN8A as a causative gene in infantile epilepsy, demonstrates a novel mechanism for hyperactivity of Nav1.6, and further expands the role of de novo mutations in severe epilepsy.
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Affiliation(s)
- Mark Estacion
- The Center for Neuroscience & Regeneration Research, Yale School of Medicine, New Haven, CT 06520, USA; The Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Janelle E O'Brien
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-5618, USA
| | | | - Michael F Hammer
- ARL Division of Biotechnology, University of Arizona, Tucson, AZ 85721, USA
| | - Stephen G Waxman
- The Center for Neuroscience & Regeneration Research, Yale School of Medicine, New Haven, CT 06520, USA; The Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Sulayman D Dib-Hajj
- The Center for Neuroscience & Regeneration Research, Yale School of Medicine, New Haven, CT 06520, USA; The Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT 06516, USA.
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-5618, USA.
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Abstract
The paralytic agent (+)-saxitoxin (STX), most commonly associated with oceanic red tides and shellfish poisoning, is a potent inhibitor of electrical conduction in cells. Its nefarious effects result from inhibition of voltage-gated sodium channels (Na(V)s), the obligatory proteins responsible for the initiation and propagation of action potentials. In the annals of ion channel research, the identification and characterization of Na(V)s trace to the availability of STX and an allied guanidinium derivative, tetrodotoxin. The mystique of STX is expressed in both its function and form, as this uniquely compact dication boasts more heteroatoms than carbon centers. This Review highlights both the chemistry and chemical biology of this fascinating natural product, and offers a perspective as to how molecular design and synthesis may be used to explore Na(V) structure and function.
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Affiliation(s)
- Arun P Thottumkara
- Department of Chemistry, Stanford University, Stanford, CA 94305-5080 (USA)
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Abstract
The pseudounipolar sensory neurons of the dorsal root ganglia (DRG) give rise to peripheral branches that convert thermal, mechanical, and chemical stimuli into electrical signals that are transmitted via central branches to the spinal cord. These neurons express unique combinations of tetrodotoxin-sensitive (TTX-S) and tetrodotoxin-resistant (TTX-R) Na(+) channels that contribute to the resting membrane potential, action potential threshold, and regulate neuronal firing frequency. The small-diameter neurons (<25 μm) isolated from the DRG represent the cell bodies of C-fiber nociceptors that express both TTX-S and TTX-R Na(+) currents. The large-diameter neurons (>35 μm) are typically low-threshold A-fibers that predominately express TTX-S Na(+) currents. Peripheral nerve damage, inflammation, and metabolic diseases alter the expression and function of these Na(+) channels leading to increases in neuronal excitability and pain. The Na(+) channels expressed in these neurons are the target of intracellular signaling cascades that regulate the trafficking, cell surface expression, and gating properties of these channels. Post-translational regulation of Na(+) channels by protein kinases (PKA, PKC, MAPK) alter the expression and function of the channels. Injury-induced changes in these signaling pathways have been linked to sensory neuron hyperexcitability and pain. This review examines the signaling pathways and regulatory mechanisms that modulate the voltage-gated Na(+) channels of sensory neurons.
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Affiliation(s)
- Mohamed Chahine
- Centre de recherche, Institut en santé mentale de Québec, Local F-6539, 2601, chemin de la Canardière, QC City, QC, Canada, G1J 2G3,
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Bird EV, Christmas CR, Loescher AR, Smith KG, Robinson PP, Black JA, Waxman SG, Boissonade FM. Correlation of Nav1.8 and Nav1.9 sodium channel expression with neuropathic pain in human subjects with lingual nerve neuromas. Mol Pain 2013; 9:52. [PMID: 24144460 PMCID: PMC4016210 DOI: 10.1186/1744-8069-9-52] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Accepted: 10/07/2013] [Indexed: 12/22/2022] Open
Abstract
Background Voltage-gated sodium channels Nav1.8 and Nav1.9 are expressed preferentially in small diameter sensory neurons, and are thought to play a role in the generation of ectopic activity in neuronal cell bodies and/or their axons following peripheral nerve injury. The expression of Nav1.8 and Nav1.9 has been quantified in human lingual nerves that have been previously injured inadvertently during lower third molar removal, and any correlation between the expression of these ion channels and the presence or absence of dysaesthesia investigated. Results Immunohistochemical processing and quantitative image analysis revealed that Nav1.8 and Nav1.9 were expressed in human lingual nerve neuromas from patients with or without symptoms of dysaesthesia. The level of Nav1.8 expression was significantly higher in patients reporting pain compared with no pain, and a significant positive correlation was observed between levels of Nav1.8 expression and VAS scores for the symptom of tingling. No significant differences were recorded in the level of expression of Nav1.9 between patients with or without pain. Conclusions These results demonstrate that Nav1.8 and Nav1.9 are present in human lingual nerve neuromas, with significant correlations between the level of expression of Nav1.8 and symptoms of pain. These data provide further evidence that changes in expression of Nav1.8 are important in the development and/or maintenance of nerve injury-induced pain, and suggest that Nav1.8 may be a potential therapeutic target.
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Affiliation(s)
- Emma V Bird
- Academic Unit of Oral and Maxillofacial Medicine and Surgery, School of Clinical Dentistry, University of Sheffield, Claremont Crescent, Sheffield S10 2TA, UK.
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Ahn HS, Vasylyev DV, Estacion M, Macala LJ, Shah P, Faber CG, Merkies IS, Dib-Hajj SD, Waxman SG. Differential effect of D623N variant and wild-type Nav1.7 sodium channels on resting potential and interspike membrane potential of dorsal root ganglion neurons. Brain Res 2013; 1529:165-77. [DOI: 10.1016/j.brainres.2013.07.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Revised: 07/02/2013] [Accepted: 07/03/2013] [Indexed: 12/15/2022]
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Laedermann CJ, Syam N, Pertin M, Decosterd I, Abriel H. β1- and β3- voltage-gated sodium channel subunits modulate cell surface expression and glycosylation of Nav1.7 in HEK293 cells. Front Cell Neurosci 2013; 7:137. [PMID: 24009557 PMCID: PMC3757325 DOI: 10.3389/fncel.2013.00137] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Accepted: 08/07/2013] [Indexed: 11/13/2022] Open
Abstract
Voltage-gated sodium channels (Navs) are glycoproteins composed of a pore-forming α-subunit and associated β-subunits that regulate Nav α-subunit plasma membrane density and biophysical properties. Glycosylation of the Nav α-subunit also directly affects Navs gating. β-subunits and glycosylation thus comodulate Nav α-subunit gating. We hypothesized that β-subunits could directly influence α-subunit glycosylation. Whole-cell patch clamp of HEK293 cells revealed that both β1- and β3-subunits coexpression shifted V ½ of steady-state activation and inactivation and increased Nav1.7-mediated I Na density. Biotinylation of cell surface proteins, combined with the use of deglycosydases, confirmed that Nav1.7 α-subunits exist in multiple glycosylated states. The α-subunit intracellular fraction was found in a core-glycosylated state, migrating at ~250 kDa. At the plasma membrane, in addition to the core-glycosylated form, a fully glycosylated form of Nav1.7 (~280 kDa) was observed. This higher band shifted to an intermediate band (~260 kDa) when β1-subunits were coexpressed, suggesting that the β1-subunit promotes an alternative glycosylated form of Nav1.7. Furthermore, the β1-subunit increased the expression of this alternative glycosylated form and the β3-subunit increased the expression of the core-glycosylated form of Nav1.7. This study describes a novel role for β1- and β3-subunits in the modulation of Nav1.7 α-subunit glycosylation and cell surface expression.
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Affiliation(s)
- Cédric J Laedermann
- Pain Center, Department of Anesthesiology, University Hospital Center and University of Lausanne Lausanne, Switzerland ; Department of Clinical Research, University of Bern Bern, Switzerland
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Abbas N, Gaudioso-Tyzra C, Bonnet C, Gabriac M, Amsalem M, Lonigro A, Padilla F, Crest M, Martin-Eauclaire MF, Delmas P. The scorpion toxin Amm VIII induces pain hypersensitivity through gain-of-function of TTX-sensitive Na+ channels. Pain 2013; 154:1204-15. [DOI: 10.1016/j.pain.2013.03.037] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Revised: 02/27/2013] [Accepted: 03/25/2013] [Indexed: 10/27/2022]
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Zheng S, Black DL. Alternative pre-mRNA splicing in neurons: growing up and extending its reach. Trends Genet 2013; 29:442-8. [PMID: 23648015 PMCID: PMC3959871 DOI: 10.1016/j.tig.2013.04.003] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Revised: 03/20/2013] [Accepted: 04/04/2013] [Indexed: 11/18/2022]
Abstract
Alternative pre-mRNA splicing determines the protein output of most neuronally expressed genes. Many examples have been described of protein function being modulated by coding changes in different mRNA isoforms. Several recent studies demonstrate that, through the coupling of splicing to other processes of mRNA metabolism, alternative splicing can also act as an on/off switch for gene expression. Other regulated splicing events may determine how an mRNA is utilized in its later cytoplasmic life by changing its localization or translation. These studies make clear that the multiple steps of post-transcriptional gene regulation are strongly linked. Together, these regulatory process play key roles in all aspects of the cell biology of neurons, from their initial differentiation, to their choice of connections, and finally to their function with mature circuits.
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Affiliation(s)
- Sika Zheng
- Department of Microbiology, Immunology, and Molecular Genetics, Howard Hughes Medical Institute, UCLA, David Geffen School of Medicine, UCLA, 6780 MRL Bldg, 675 Charles Young Dr. S. Los Angeles, CA 90095-1662, (310) 794-7644
| | - Douglas L. Black
- Department of Microbiology, Immunology, and Molecular Genetics, Howard Hughes Medical Institute, UCLA, David Geffen School of Medicine, UCLA, 6780 MRL Bldg, 675 Charles Young Dr. S. Los Angeles, CA 90095-1662, (310) 794-7644
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Heimann D, Lötsch J, Hummel T, Doehring A, Oertel BG. Linkage between increased nociception and olfaction via a SCN9A haplotype. PLoS One 2013; 8:e68654. [PMID: 23874707 PMCID: PMC3707874 DOI: 10.1371/journal.pone.0068654] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Accepted: 05/30/2013] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND AND AIMS Mutations reducing the function of Nav1.7 sodium channels entail diminished pain perception and olfactory acuity, suggesting a link between nociception and olfaction at ion channel level. We hypothesized that if such link exists, it should work in both directions and gain-of-function Nav1.7 mutations known to be associated with increased pain perception should also increase olfactory acuity. METHODS SCN9A variants were assessed known to enhance pain perception and found more frequently in the average population. Specifically, carriers of SCN9A variants rs41268673C>A (P610T; n = 14) or rs6746030C>T (R1150W; n = 21) were compared with non-carriers (n = 40). Olfactory function was quantified by assessing odor threshold, odor discrimination and odor identification using an established olfactory test. Nociception was assessed by measuring pain thresholds to experimental nociceptive stimuli (punctate and blunt mechanical pressure, heat and electrical stimuli). RESULTS The number of carried alleles of the non-mutated SCN9A haplotype rs41268673C/rs6746030C was significantly associated with the comparatively highest olfactory threshold (0 alleles: threshold at phenylethylethanol dilution step 12 of 16 (n = 1), 1 allele: 10.6±2.6 (n = 34), 2 alleles: 9.5±2.1 (n = 40)). The same SCN9A haplotype determined the pain threshold to blunt pressure stimuli (0 alleles: 21.1 N/m(2), 1 allele: 29.8±10.4 N/m(2), 2 alleles: 33.5±10.2 N/m(2)). CONCLUSIONS The findings established a working link between nociception and olfaction via Nav1.7 in the gain-of-function direction. Hence, together with the known reduced olfaction and pain in loss-of-function mutations, a bidirectional genetic functional association between nociception and olfaction exists at Nav1.7 level.
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Affiliation(s)
- Dirk Heimann
- Institute of Clinical Pharmacology, Goethe - University, Frankfurt am Main, Germany
| | - Jörn Lötsch
- Institute of Clinical Pharmacology, Goethe - University, Frankfurt am Main, Germany
- Fraunhofer Institute of Molecular Biology and Applied Ecology - Project Group Translational Medicine and Pharmacology (IME-TMP), Frankfurt am Main, Germany
| | - Thomas Hummel
- Smell and Taste Clinic, Department of Otorhinolaryngology, University of Dresden Medical School, Dresden, Germany
| | - Alexandra Doehring
- Institute of Clinical Pharmacology, Goethe - University, Frankfurt am Main, Germany
| | - Bruno G. Oertel
- Institute of Clinical Pharmacology, Goethe - University, Frankfurt am Main, Germany
- Fraunhofer Institute of Molecular Biology and Applied Ecology - Project Group Translational Medicine and Pharmacology (IME-TMP), Frankfurt am Main, Germany
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Petho G, Reeh PW. Sensory and signaling mechanisms of bradykinin, eicosanoids, platelet-activating factor, and nitric oxide in peripheral nociceptors. Physiol Rev 2013; 92:1699-775. [PMID: 23073630 DOI: 10.1152/physrev.00048.2010] [Citation(s) in RCA: 191] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Peripheral mediators can contribute to the development and maintenance of inflammatory and neuropathic pain and its concomitants (hyperalgesia and allodynia) via two mechanisms. Activation or excitation by these substances of nociceptive nerve endings or fibers implicates generation of action potentials which then travel to the central nervous system and may induce pain sensation. Sensitization of nociceptors refers to their increased responsiveness to either thermal, mechanical, or chemical stimuli that may be translated to corresponding hyperalgesias. This review aims to give an account of the excitatory and sensitizing actions of inflammatory mediators including bradykinin, prostaglandins, thromboxanes, leukotrienes, platelet-activating factor, and nitric oxide on nociceptive primary afferent neurons. Manifestations, receptor molecules, and intracellular signaling mechanisms of the effects of these mediators are discussed in detail. With regard to signaling, most data reported have been obtained from transfected nonneuronal cells and somata of cultured sensory neurons as these structures are more accessible to direct study of sensory and signal transduction. The peripheral processes of sensory neurons, where painful stimuli actually affect the nociceptors in vivo, show marked differences with respect to biophysics, ultrastructure, and equipment with receptors and ion channels compared with cellular models. Therefore, an effort was made to highlight signaling mechanisms for which supporting data from molecular, cellular, and behavioral models are consistent with findings that reflect properties of peripheral nociceptive nerve endings. Identified molecular elements of these signaling pathways may serve as validated targets for development of novel types of analgesic drugs.
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Affiliation(s)
- Gábor Petho
- Pharmacodynamics Unit, Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Pécs, Pécs, Hungary
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Cregg R, Laguda B, Werdehausen R, Cox JJ, Linley JE, Ramirez JD, Bodi I, Markiewicz M, Howell KJ, Chen YC, Agnew K, Houlden H, Lunn MP, Bennett DLH, Wood JN, Kinali M. Novel mutations mapping to the fourth sodium channel domain of Nav1.7 result in variable clinical manifestations of primary erythromelalgia. Neuromolecular Med 2013; 15:265-78. [PMID: 23292638 PMCID: PMC3650253 DOI: 10.1007/s12017-012-8216-8] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2012] [Accepted: 12/14/2012] [Indexed: 01/01/2023]
Abstract
We identified and clinically investigated two patients with primary erythromelalgia mutations (PEM), which are the first reported to map to the fourth domain of Nav1.7 (DIV). The identified mutations (A1746G and W1538R) were cloned and transfected to cell cultures followed by electrophysiological analysis in whole-cell configuration. The investigated patients presented with PEM, while age of onset was very different (3 vs. 61 years of age). Electrophysiological characterization revealed that the early onset A1746G mutation leads to a marked hyperpolarizing shift in voltage dependence of steady-state activation, larger window currents, faster activation kinetics (time-to-peak current) and recovery from steady-state inactivation compared to wild-type Nav1.7, indicating a pronounced gain-of-function. Furthermore, we found a hyperpolarizing shift in voltage dependence of slow inactivation, which is another feature commonly found in Nav1.7 mutations associated with PEM. In silico neuron simulation revealed reduced firing thresholds and increased repetitive firing, both indicating hyperexcitability. The late-onset W1538R mutation also revealed gain-of-function properties, although to a lesser extent. Our findings demonstrate that mutations encoding for DIV of Nav1.7 can not only be linked to congenital insensitivity to pain or paroxysmal extreme pain disorder but can also be causative of PEM, if voltage dependency of channel activation is affected. This supports the view that the degree of biophysical property changes caused by a mutation may have an impact on age of clinical manifestation of PEM. In summary, these findings extent the genotype-phenotype correlation profile for SCN9A and highlight a new region of Nav1.7 that is implicated in PEM.
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Affiliation(s)
- Roman Cregg
- Molecular Nociception Group, Wolfson Institute for Biomedical Research, UCL, Gower Street, London, WC1E 6BT UK
- UCL Centre for Anaesthesia, Critical Care and Pain Medicine, London, UK
| | - Bisola Laguda
- Department of Paediatric Dermatology, Chelsea and Westminster Hospital, London, UK
| | - Robert Werdehausen
- Molecular Nociception Group, Wolfson Institute for Biomedical Research, UCL, Gower Street, London, WC1E 6BT UK
- Department of Anesthesiology, Heinrich-Heine-University, Düsseldorf, Germany
| | - James J. Cox
- Molecular Nociception Group, Wolfson Institute for Biomedical Research, UCL, Gower Street, London, WC1E 6BT UK
| | - John E. Linley
- Molecular Nociception Group, Wolfson Institute for Biomedical Research, UCL, Gower Street, London, WC1E 6BT UK
| | - Juan D. Ramirez
- Neurorestoration Group, CARD, King’s College London, Guy’s Campus, London, UK
- The Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, UK
| | - Istvan Bodi
- Department of Clinical Neuropathology, King’s College Hospital, London, UK
| | | | - Kevin J. Howell
- Centre for Rheumatology and Connective Tissue Disease, UCL Division of Medicine, Royal Free Campus, London, UK
| | - Ya-Chun Chen
- Division of Cell and Molecular Biology, Faculty of Natural Sciences, Imperial College London, London, UK
| | - Karen Agnew
- Department of Paediatric Dermatology, Chelsea and Westminster Hospital, London, UK
| | - Henry Houlden
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology and The National Hospital for Neurology and Neurosurgery, Queen Square, London, UK
| | - Michael P. Lunn
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology and The National Hospital for Neurology and Neurosurgery, Queen Square, London, UK
| | - David L. H. Bennett
- The Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, UK
| | - John N. Wood
- Molecular Nociception Group, Wolfson Institute for Biomedical Research, UCL, Gower Street, London, WC1E 6BT UK
| | - Maria Kinali
- Department of Paediatric Neurology, Chelsea and Westminster Hospital, London, UK
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Akimoto T, Masuda A, Yotsu-Yamashita M, Hirokawa T, Nagasawa K. Synthesis of saxitoxin derivatives bearing guanidine and urea groups at C13 and evaluation of their inhibitory activity on voltage-gated sodium channels. Org Biomol Chem 2013; 11:6642-9. [DOI: 10.1039/c3ob41398e] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Ossipov MH. The perception and endogenous modulation of pain. SCIENTIFICA 2012; 2012:561761. [PMID: 24278716 PMCID: PMC3820628 DOI: 10.6064/2012/561761] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Accepted: 11/19/2012] [Indexed: 06/02/2023]
Abstract
Pain is often perceived an unpleasant experience that includes sensory and emotional/motivational responses. Accordingly, pain serves as a powerful teaching signal enabling an organism to avoid injury, and is critical to survival. However, maladaptive pain, such as neuropathic or idiopathic pain, serves no survival function. Genomic studies of individuals with congenital insensitivity to pain or paroxysmal pain syndromes considerable increased our understanding of the function of peripheral nociceptors, and especially of the roles of voltage-gated sodium channels and of nerve growth factor (NGF)/TrkA receptors in nociceptive transduction and transmission. Brain imaging studies revealed a "pain matrix," consisting of cortical and subcortical regions that respond to noxious inputs and can positively or negatively modulate pain through activation of descending pain modulatory systems. Projections from the periaqueductal grey (PAG) and the rostroventromedial medulla (RVM) to the trigeminal and spinal dorsal horns can inhibit or promote further nociceptive inputs. The "pain matrix" can explain such varied phenomena as stress-induced analgesia, placebo effect and the role of expectation on pain perception. Disruptions in these systems may account for the existence idiopathic pan states such as fibromyalgia. Increased understanding of pain modulatory systems will lead to development of more effective therapeutics for chronic pain.
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Affiliation(s)
- Michael H. Ossipov
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, AZ 85724, USA
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Knapp O, Nevin ST, Yasuda T, Lawrence N, Lewis RJ, Adams DJ. Biophysical properties of Na(v) 1.8/Na(v) 1.2 chimeras and inhibition by µO-conotoxin MrVIB. Br J Pharmacol 2012; 166:2148-60. [PMID: 22452751 DOI: 10.1111/j.1476-5381.2012.01955.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND AND PURPOSE Voltage-gated sodium channels are expressed primarily in excitable cells and play a pivotal role in the initiation and propagation of action potentials. Nine subtypes of the pore-forming α-subunit have been identified, each with a distinct tissue distribution, biophysical properties and sensitivity to tetrodotoxin (TTX). Na(v) 1.8, a TTX-resistant (TTX-R) subtype, is selectively expressed in sensory neurons and plays a pathophysiological role in neuropathic pain. In comparison with TTX-sensitive (TTX-S) Na(v) α-subtypes in neurons, Na(v) 1.8 is most strongly inhibited by the µO-conotoxin MrVIB from Conus marmoreus. To determine which domain confers Na(v) 1.8 α-subunit its biophysical properties and MrVIB binding, we constructed various chimeric channels incorporating sequence from Na(v) 1.8 and the TTX-S Na(v) 1.2 using a domain exchange strategy. EXPERIMENTAL APPROACH Wild-type and chimeric Na(v) channels were expressed in Xenopus oocytes, and depolarization-activated Na⁺ currents were recorded using the two-electrode voltage clamp technique. KEY RESULTS MrVIB (1 µM) reduced Na(v) 1.2 current amplitude to 69 ± 12%, whereas Na(v) 1.8 current was reduced to 31 ± 3%, confirming that MrVIB has a binding preference for Na(v) 1.8. A similar reduction in Na⁺ current amplitude was observed when MrVIB was applied to chimeras containing the region extending from S6 segment of domain I through the S5-S6 linker of domain II of Na(v) 1.8. In contrast, MrVIB had only a small effect on Na⁺ current for chimeras containing the corresponding region of Na(v) 1.2. CONCLUSIONS AND IMPLICATIONS Taken together, these results suggest that domain II of Na(v) 1.8 is an important determinant of MrVIB affinity, highlighting a region of the α-subunit that may allow further nociceptor-specific ligand targeting.
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Affiliation(s)
- O Knapp
- Health Innovations Research Institute, RMIT University, Melbourne, Vic, Australia
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Knapp O, McArthur JR, Adams DJ. Conotoxins targeting neuronal voltage-gated sodium channel subtypes: potential analgesics? Toxins (Basel) 2012. [PMID: 23202314 PMCID: PMC3509706 DOI: 10.3390/toxins4111236] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Voltage-gated sodium channels (VGSC) are the primary mediators of electrical signal amplification and propagation in excitable cells. VGSC subtypes are diverse, with different biophysical and pharmacological properties, and varied tissue distribution. Altered VGSC expression and/or increased VGSC activity in sensory neurons is characteristic of inflammatory and neuropathic pain states. Therefore, VGSC modulators could be used in prospective analgesic compounds. VGSCs have specific binding sites for four conotoxin families: μ-, μO-, δ- and ί-conotoxins. Various studies have identified that the binding site of these peptide toxins is restricted to well-defined areas or domains. To date, only the μ- and μO-family exhibit analgesic properties in animal pain models. This review will focus on conotoxins from the μ- and μO-families that act on neuronal VGSCs. Examples of how these conotoxins target various pharmacologically important neuronal ion channels, as well as potential problems with the development of drugs from conotoxins, will be discussed.
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Affiliation(s)
- Oliver Knapp
- Health Innovations Research Institute, RMIT University, Melbourne, Victoria 3083, Australia.
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Eckrich T, Varakina K, Johnson SL, Franz C, Singer W, Kuhn S, Knipper M, Holley MC, Marcotti W. Development and function of the voltage-gated sodium current in immature mammalian cochlear inner hair cells. PLoS One 2012; 7:e45732. [PMID: 23029208 PMCID: PMC3446918 DOI: 10.1371/journal.pone.0045732] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Accepted: 08/14/2012] [Indexed: 12/19/2022] Open
Abstract
Inner hair cells (IHCs), the primary sensory receptors of the mammalian cochlea, fire spontaneous Ca2+ action potentials before the onset of hearing. Although this firing activity is mainly sustained by a depolarizing L-type (CaV1.3) Ca2+ current (ICa), IHCs also transiently express a large Na+ current (INa). We aimed to investigate the specific contribution of INa to the action potentials, the nature of the channels carrying the current and whether the biophysical properties of INa differ between low- and high-frequency IHCs. We show that INa is highly temperature-dependent and activates at around −60 mV, close to the action potential threshold. Its size was larger in apical than in basal IHCs and between 5% and 20% should be available at around the resting membrane potential (−55 mV/−60 mV). However, in vivo the availability of INa could potentially increase to >60% during inhibitory postsynaptic potential activity, which transiently hyperpolarize IHCs down to as far as −70 mV. When IHCs were held at −60 mV and INa elicited using a simulated action potential as a voltage command, we found that INa contributed to the subthreshold depolarization and upstroke of an action potential. We also found that INa is likely to be carried by the TTX-sensitive channel subunits NaV1.1 and NaV1.6 in both apical and basal IHCs. The results provide insight into how the biophysical properties of INa in mammalian cochlear IHCs could contribute to the spontaneous physiological activity during cochlear maturation in vivo.
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Affiliation(s)
- Tobias Eckrich
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Ksenya Varakina
- Department of Otolaryngology, Tübingen Hearing Research Center, Molecular Physiology of Hearing, University of Tübingen, Tübingen, Germany
| | - Stuart L. Johnson
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Christoph Franz
- Department of Otolaryngology, Tübingen Hearing Research Center, Molecular Physiology of Hearing, University of Tübingen, Tübingen, Germany
| | - Wibke Singer
- Department of Otolaryngology, Tübingen Hearing Research Center, Molecular Physiology of Hearing, University of Tübingen, Tübingen, Germany
| | - Stephanie Kuhn
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Marlies Knipper
- Department of Otolaryngology, Tübingen Hearing Research Center, Molecular Physiology of Hearing, University of Tübingen, Tübingen, Germany
| | - Matthew C. Holley
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
- * E-mail: (MH); (WM)
| | - Walter Marcotti
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
- * E-mail: (MH); (WM)
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69
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Obreja O, Hirth M, Turnquist B, Rukwied R, Ringkamp M, Schmelz M. The Differential Effects of Two Sodium Channel Modulators on the Conductive Properties of C-Fibers in Pig Skin In Vivo. Anesth Analg 2012; 115:560-71. [DOI: 10.1213/ane.0b013e3182542843] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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70
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Chowdhury S, Liu S, Cadieux JA, Hsieh T, Chafeev M, Sun S, Jia Q, Sun J, Wood M, Langille J, Sviridov S, Fu J, Zhang Z, Chui R, Wang A, Cheng X, Zhong J, Hossain S, Khakh K, Rajlic I, Verschoof H, Kwan R, Young W. Tetracyclic spirooxindole blockers of hNaV1.7: activity in vitro and in CFA-induced inflammatory pain model. Med Chem Res 2012. [DOI: 10.1007/s00044-012-0180-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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71
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Hoeijmakers JGJ, Merkies ISJ, Gerrits MM, Waxman SG, Faber CG. Genetic aspects of sodium channelopathy in small fiber neuropathy. Clin Genet 2012; 82:351-8. [PMID: 22803682 DOI: 10.1111/j.1399-0004.2012.01937.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Revised: 07/11/2012] [Accepted: 07/11/2012] [Indexed: 12/12/2022]
Abstract
Small fiber neuropathy (SFN) is a disorder typically dominated by neuropathic pain and autonomic dysfunction, in which the thinly myelinated Aδ-fibers and unmyelinated C-fibers are selectively injured. The diagnosis SFN is based on a reduced intraepidermal nerve fiber density and/or abnormal thermal thresholds in quantitative sensory testing. The etiologies of SFN are diverse, although no apparent cause is frequently seen. Recently, SCN9A-gene variants (single amino acid substitutions) have been found in ∼30% of a cohort of idiopathic SFN patients, producing gain-of-function changes in sodium channel Na(V)1.7, which is preferentially expressed in small diameter peripheral axons. Functional testing showed that these variants altered fast inactivation, slow inactivation or resurgent current and rendered dorsal root ganglion neurons hyperexcitable. In this review, we discuss the role of Na(V)1.7 in pain and highlight the molecular genetics and pathophysiology of SCN9A-gene variants in SFN. With increasing knowledge regarding the underlying pathophysiology in SFN, the development of specific treatment in these patients seems a logical target for future studies.
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Affiliation(s)
- J G J Hoeijmakers
- Department of Neurology, Maastricht University Medical Center, Maastricht, The Netherlands
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72
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Sheets PL, Jarecki BW, Cummins TR. Lidocaine reduces the transition to slow inactivation in Na(v)1.7 voltage-gated sodium channels. Br J Pharmacol 2012; 164:719-30. [PMID: 21232038 DOI: 10.1111/j.1476-5381.2011.01209.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND AND PURPOSE The primary use of local anaesthetics is to prevent or relieve pain by reversibly preventing action potential propagation through the inhibition of voltage-gated sodium channels. The tetrodotoxin-sensitive voltage-gated sodium channel subtype Na(v)1.7, abundantly expressed in pain-sensing neurons, plays a crucial role in perception and transmission of painful stimuli and in inherited chronic pain syndromes. Understanding the interaction of lidocaine with Na(v)1.7 channels could provide valuable insight into the drug's action in alleviating pain in distinct patient populations. The aim of this study was to determine how lidocaine interacts with multiple inactivated conformations of Na(v)1.7 channels. EXPERIMENTAL APPROACH We investigated the interactions of lidocaine with wild-type Na(v)1.7 channels and a paroxysmal extreme pain disorder mutation (I1461T) that destabilizes fast inactivation. Whole cell patch clamp recordings were used to examine the activity of channels expressed in human embryonic kidney 293 cells. KEY RESULTS Depolarizing pulses that increased slow inactivation of Na(v)1.7 channels also reduced lidocaine inhibition. Lidocaine enhanced recovery of Na(v)1.7 channels from prolonged depolarizing pulses by decreasing slow inactivation. A paroxysmal extreme pain disorder mutation that destabilizes fast inactivation of Na(v)1.7 channels decreased lidocaine inhibition. CONCLUSIONS AND IMPLICATIONS Lidocaine decreased the transition of Na(v)1.7 channels to the slow inactivated state. The fast inactivation gate (domain III-IV linker) is important for potentiating the interaction of lidocaine with the Na(v)1.7 channel.
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Affiliation(s)
- Patrick L Sheets
- Department of Pharmacology and Toxicology, Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, USA
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73
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Ho C, Zhao J, Malinowski S, Chahine M, O'Leary ME. Differential expression of sodium channel β subunits in dorsal root ganglion sensory neurons. J Biol Chem 2012; 287:15044-53. [PMID: 22408255 DOI: 10.1074/jbc.m111.333740] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The small-diameter (<25 μm) and large-diameter (>30 μm) sensory neurons of the dorsal root ganglion (DRG) express distinct combinations of tetrodotoxin sensitive and tetrodotoxin-resistant Na(+) channels that underlie the unique electrical properties of these neurons. In vivo, these Na(+) channels are formed as complexes of pore-forming α and auxiliary β subunits. The goal of this study was to investigate the expression of β subunits in DRG sensory neurons. Quantitative single-cell RT-PCR revealed that β subunit mRNA is differentially expressed in small (β(2) and β(3)) and large (β(1) and β(2)) DRG neurons. This raises the possibility that β subunit availability and Na(+) channel composition and functional regulation may differ in these subpopulations of sensory neurons. To further explore these possibilities, we quantitatively compared the mRNA expression of the β subunit with that of Na(v)1.7, a TTX-sensitive Na(+) channel widely expressed in both small and large DRG neurons. Na(v)1.7 and β subunit mRNAs were significantly correlated in small (β(2) and β(3)) and large (β(1) and β(2)) DRG neurons, indicating that these subunits are coexpressed in the same populations. Co-immunoprecipitation and immunocytochemistry indicated that Na(v)1.7 formed stable complexes with the β(1)-β(3) subunits in vivo and that Na(v)1.7 and β(3) co-localized within the plasma membranes of small DRG neurons. Heterologous expression studies showed that β(3) induced a hyperpolarizing shift in Na(v)1.7 activation, whereas β(1) produced a depolarizing shift in inactivation and faster recovery. The data indicate that β(3) and β(1) subunits are preferentially expressed in small and large DRG neurons, respectively, and that these auxiliary subunits differentially regulate the gating properties of Na(v)1.7 channels.
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Affiliation(s)
- Cojen Ho
- Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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74
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Prolonged cutaneous analgesia with transdermal application of amitriptyline and capsaicin. Reg Anesth Pain Med 2012; 36:236-40. [PMID: 21364497 DOI: 10.1097/aap.0b013e31820c2c30] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
BACKGROUND AND OBJECTIVES Capsaicin selectively binds to TRPV1, the vanilloid subtype 1 of the superfamily of transient receptor potential ion channels, which is highly expressed in pain-transmitting C fibers. Recent reports have demonstrated that the coadministration of capsaicin with a local anesthetic (LA) at the rat sciatic nerve elicits a prolonged nociceptive-selective nerve block, suggesting that activation of the TRPV1 receptor may allow LAs to enter the nerve through the TRPV1 pore. In previous studies, we demonstrated that transdermal amitriptyline achieves clinical analgesic effects and is more potent than lidocaine. Here we examine whether the combined application of amitriptyline and capsaicin as a transdermal patch will produce prolonged cutaneous analgesia compared with amitriptyline alone. METHODS Male Sprague-Dawley rats (weights 250-300 g) were assigned to five treatment groups (n = 6-8 per group). Transdermal patches containing amitriptyline with different concentrations of capsaicin were applied for 3 hrs to rats' shaved backs: 2.5% amitriptyline alone (control group) and in combination with 0.05%, 0.15%, 1%, and 8% capsaicin. Behavioral testing for cutaneous nociception was conducted before drug application and after patch removal using the cutaneous trunci muscle reflex. In addition, skin appearance was assessed to determine irritation by these formulations. RESULTS The cutaneous analgesic effect is significantly prolonged when amitriptyline is applied in combination with 8% capsaicin. Amitriptyline alone provided a complete block to pinprick for 4.5 hrs, and the time to full recovery was 96 hrs. Amitriptyline with 8% capsaicin produced a complete block to pinprick for 6 to 9 hrs, and the time to full recovery was 216 hrs (P = 0.002). Amitriptyline alone causes toxic effects in skin, whereas the higher the concentration of capsaicin, the less skin irritation was noted, and the combination of amitriptyline 2.5% with capsaicin 8% caused no adverse skin reactions. CONCLUSIONS This study demonstrates that the combined application of amitriptyline and capsaicin results in prolonged cutaneous analgesia compared with amitriptyline alone, suggesting that the activation of the TRPV1 channel by capsaicin facilitates the passage of amitriptyline into nociceptors. This transdermal patch achieves far longer cutaneous analgesia than currently available patch applications such as EMLA cream. The mechanism that underlies the lesser skin irritation noted when amitriptyline is combined with higher doses of capsaicin compared with amitriptyline alone is unclear and may be related to a counteraction of amitriptyline-induced vasoconstriction.
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75
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Affiliation(s)
- Henry Houlden
- UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK.
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76
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Tetrodotoxin (TTX) as a therapeutic agent for pain. Mar Drugs 2012; 10:281-305. [PMID: 22412801 PMCID: PMC3296997 DOI: 10.3390/md10020281] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2011] [Revised: 01/19/2012] [Accepted: 01/19/2012] [Indexed: 12/19/2022] Open
Abstract
Tetrodotoxin (TTX) is a potent neurotoxin that blocks voltage-gated sodium channels (VGSCs). VGSCs play a critical role in neuronal function under both physiological and pathological conditions. TTX has been extensively used to functionally characterize VGSCs, which can be classified as TTX-sensitive or TTX-resistant channels according to their sensitivity to this toxin. Alterations in the expression and/or function of some specific TTX-sensitive VGSCs have been implicated in a number of chronic pain conditions. The administration of TTX at doses below those that interfere with the generation and conduction of action potentials in normal (non-injured) nerves has been used in humans and experimental animals under different pain conditions. These data indicate a role for TTX as a potential therapeutic agent for pain. This review focuses on the preclinical and clinical evidence supporting a potential analgesic role for TTX. In addition, the contribution of specific TTX-sensitive VGSCs to pain is reviewed.
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77
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Ahn HS, Dib-Hajj SD, Cox JJ, Tyrrell L, Elmslie FV, Clarke AA, Drenth JP, Woods CG, Waxman SG. A new Nav1.7 sodium channel mutation I234T in a child with severe pain. Eur J Pain 2012; 14:944-50. [DOI: 10.1016/j.ejpain.2010.03.007] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2010] [Revised: 03/08/2010] [Accepted: 03/16/2010] [Indexed: 12/21/2022]
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Vickery RG, Amagasu SM, Chang R, Mai N, Kaufman E, Martin J, Hembrador J, O'Keefe MD, Gee C, Marquess D, Smith JAM. Comparison of the Pharmacological Properties of Rat NaV1.8 with Rat NaV1.2a and Human NaV1.5 Voltage-Gated Sodium Channel Subtypes Using a Membrane Potential Sensitive Dye and FLIPRR. ACTA ACUST UNITED AC 2011. [DOI: 10.3109/10606820490270410] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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79
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Akiba I, Seki T, Mori M, Iizuka M, Nishimura S, Sasaki S, Imoto K, Barsoumian EL. Stable Expression and Characterization of Human PN1 and PN3 Sodium Channels. ACTA ACUST UNITED AC 2011; 9:291-9. [PMID: 14527872 DOI: 10.3109/713745174] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Nociceptive transduction in inflammatory and neuropathic pain involves peripherally expressed voltage-gated sodium channels, such as tetrodotoxin (TTX)-sensitive PN1 and TTX-resistant PN3. We generated recombinant cell lines stably expressing the human PN1 and PN3 sodium channels in Chinese hamster ovary (CHO) cells using inducible expression vectors. The PN1 and PN3 cDNAs were isolated from human adrenal gland and heart poly(A)+ RNAs, respectively. The recombinant human PN1 currents exhibited rapid activation and inactivation kinetics and were blocked by TTX with a half-maximal inhibitory concentration (IC50) of 32.6 nM. The human PN3 channel expressed in stable transfectants showed TTX-resistant inward currents with slow inactivation kinetics. The IC50 value for TTX was 73.3 microM. The voltage-dependence of activation of the PN3 channel was shifted to the depolarizing direction, compared to that of the PN1 channel. Lidocaine and mexiletine exhibited tonic and use-dependent block of PN1 and PN3 channels. The PN1 channel was more susceptible to inhibition by mexiletine than PN3. These results suggest that stable transfectants expressing the human PN1 and PN3 sodium channels will be useful tools to define subtype selectivity for sodium channel blockers.
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Affiliation(s)
- Isamu Akiba
- Department of Molecular and Cellular Biology, Nippon Boehringer Ingelheim Co., Ltd., Kawanishi Pharma Research Institute, Yato, Kawanishi, Japan
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80
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Estacion M, Han C, Choi JS, Hoeijmakers JGJ, Lauria G, Drenth JPH, Gerrits MM, Dib-Hajj SD, Faber CG, Merkies ISJ, Waxman SG. Intra- and interfamily phenotypic diversity in pain syndromes associated with a gain-of-function variant of NaV1.7. Mol Pain 2011; 7:92. [PMID: 22136189 PMCID: PMC3248882 DOI: 10.1186/1744-8069-7-92] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2011] [Accepted: 12/02/2011] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Sodium channel NaV1.7 is preferentially expressed within dorsal root ganglia (DRG), trigeminal ganglia and sympathetic ganglion neurons and their fine-diamter axons, where it acts as a threshold channel, amplifying stimuli such as generator potentials in nociceptors. Gain-of-function mutations and variants (single amino acid substitutions) of NaV1.7 have been linked to three pain syndromes: Inherited Erythromelalgia (IEM), Paroxysmal Extreme Pain Disorder (PEPD), and Small Fiber Neuropathy (SFN). IEM is characterized clinically by burning pain and redness that is usually focused on the distal extremities, precipitated by mild warmth and relieved by cooling, and is caused by mutations that hyperpolarize activation, slow deactivation, and enhance the channel ramp response. PEPD is characterized by perirectal, periocular or perimandibular pain, often triggered by defecation or lower body stimulation, and is caused by mutations that severely impair fast-inactivation. SFN presents a clinical picture dominated by neuropathic pain and autonomic symptoms; gain-of-function variants have been reported to be present in approximately 30% of patients with biopsy-confirmed idiopathic SFN, and functional testing has shown altered fast-inactivation, slow-inactivation or resurgent current. In this paper we describe three patients who house the NaV1.7/I228M variant. METHODS We have used clinical assessment of patients, quantitative sensory testing and skin biopsy to study these patients, including two siblings in one family, in whom genomic screening demonstrated the I228M NaV1.7 variant. Electrophysiology (voltage-clamp and current-clamp) was used to test functional effects of the variant channel. RESULTS We report three different clinical presentations of the I228M NaV1.7 variant: presentation with severe facial pain, presentation with distal (feet, hands) pain, and presentation with scalp discomfort in three patients housing this NaV1.7 variant, two of which are from a single family. We also demonstrate that the NaV1.7/I228M variant impairs slow-inactivation, and produces hyperexcitability in both trigeminal ganglion and DRG neurons. CONCLUSION Our results demonstrate intra- and interfamily phenotypic diversity in pain syndromes produced by a gain-of-function variant of NaV1.7.
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Affiliation(s)
- Mark Estacion
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT 06516, USA
| | - Chongyang Han
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT 06516, USA
| | - Jin-Sung Choi
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT 06516, USA
- College of Pharmacy, Catholic University of Korea, Bucheon, South Korea
| | - Janneke GJ Hoeijmakers
- Department of Neurology, University Medical Center Maastricht, Maastricht, the Netherlands
| | - Giuseppe Lauria
- Neuromuscular Diseases Unit, IRCCS Foundation, "Carlo Besta", Milan, Italy
| | - Joost PH Drenth
- Department of Gastroenterology and Hepatology, Radboud University Nijmegen Medical Center, Nijmegen, the Netherlands
| | - Monique M Gerrits
- Department of Clinical Genetics, University Medical Center Maastricht, Maastricht, the Netherlands
| | - Sulayman D Dib-Hajj
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT 06516, USA
| | - Catharina G Faber
- Department of Neurology, University Medical Center Maastricht, Maastricht, the Netherlands
| | - Ingemar SJ Merkies
- Department of Neurology, University Medical Center Maastricht, Maastricht, the Netherlands
- Department of Neurology, Spaarne Hospital, Hoofddorp, the Netherlands
| | - Stephen G Waxman
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT 06516, USA
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Skeik N, Rooke TW, Davis MDP, Davis DMR, Kalsi H, Kurth I, Richardson RC. Severe case and literature review of primary erythromelalgia: novel SCN9A gene mutation. Vasc Med 2011; 17:44-9. [PMID: 22033523 DOI: 10.1177/1358863x11422584] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Erythromelalgia is a rare clinical syndrome characterized by intermittent heat, redness, swelling and pain more commonly affecting the lower extremities. Symptoms are mostly aggravated by warmth and are eased by a cold temperature. In some cases, symptoms can be very severe and disabling. Erythromelalgia can be classified as either familial or sporadic, with the familial form inherited in an autosomal dominant manner. Recently, there has been a lot of progress in studying Na(v)1.7 sodium channels (expressed mostly in the sympathetic and nociceptive small-diameter sensory neurons of the dorsal root ganglion) and different mutations affecting the encoding SCN9A gene that leads to channelopathies responsible for some disorders, including primary erythromelalgia. We present a severe case of progressive primary erythromelalgia caused by a new de novo heterozygous missense mutation (c.2623C>G) of the SCN9A gene which substitutes glutamine 875 by glutamic acid (p.Q875E). To our knowledge, this mutation has not been previously reported in the literature. We also provided a short literature review about erythromelalgia and Na(v) sodium channelopathies.
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Affiliation(s)
- Nedaa Skeik
- Vascular Medicine, Mayo Clinic, Rochester, MN, USA.
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82
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Theile JW, Cummins TR. Recent developments regarding voltage-gated sodium channel blockers for the treatment of inherited and acquired neuropathic pain syndromes. Front Pharmacol 2011; 2:54. [PMID: 22007172 PMCID: PMC3185237 DOI: 10.3389/fphar.2011.00054] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2011] [Accepted: 09/12/2011] [Indexed: 12/19/2022] Open
Abstract
Chronic and neuropathic pain constitute significant health problems affecting millions of individuals each year. Pain sensations typically originate in sensory neurons of the peripheral nervous system which relay information to the central nervous system (CNS). Pathological pain sensations can arise as result of changes in excitability of these peripheral sensory neurons. Voltage-gated sodium channels are key determinants regulating action potential generation and propagation; thus, changes in sodium channel function can have profound effects on neuronal excitability and pain signaling. At present, most of the clinically available sodium channel blockers used to treat pain are non-selective across sodium channel isoforms and can contribute to cardio-toxicity, motor impairments, and CNS side effects. Numerous strides have been made over the last decade in an effort to develop more selective and efficacious sodium channel blockers to treat pain. The purpose of this review is to highlight some of the more recent developments put forth by research universities and pharmaceutical companies alike in the pursuit of developing more targeted sodium channel therapies for the treatment of a variety of neuropathic pain conditions.
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Affiliation(s)
- Jonathan W Theile
- Department of Pharmacology and Toxicology, Stark Neurosciences Research Institute, Indiana University School of Medicine Indianapolis, IN, USA
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83
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Shinohara R, Akimoto T, Iwamoto O, Hirokawa T, Yotsu-Yamashita M, Yamaoka K, Nagasawa K. Synthesis of skeletal analogues of saxitoxin derivatives and evaluation of their inhibitory activity on sodium ion channels Na(V)1.4 and Na(V)1.5. Chemistry 2011; 17:12144-52. [PMID: 21922571 DOI: 10.1002/chem.201101058] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2011] [Revised: 07/20/2011] [Indexed: 12/19/2022]
Abstract
Skeletal analogues of saxitoxin (STX) that possess a fused-type tricyclic ring system, designated FD-STX, were synthesized as candidate sodium ion channel modulators. Three kinds of FD-STX derivatives 4a-c with different substitution at C13 were synthesized, and their inhibitory activity on sodium ion channels was examined by means of cell-based assay. (-)-FD-STX (4a) and (-)-FD-dcSTX (4b), which showed moderate inhibitory activity, were further evaluated by the use of the patch-clamp method in cells that expressed Na(V)1.4 (a tetrodotoxin-sensitive sodium channel subtype) and Na(V)1.5 (a tetrodotoxin-resistant sodium channel subtype). These compounds showed moderate inhibitory activity towards Na(V)1.4, and weaker inhibitory activity towards Na(V)1.5. Uniquely, however, the inhibition of Na(V)1.5 by (-)-FD-dcSTX (4b) was "irreversible".
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Affiliation(s)
- Ryoko Shinohara
- Tokyo University of Agriculture and Technology, Department of Biotechnology and Life Science, Koganei, Tokyo 184-8588, Japan
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Tan J, Soderlund DM. Actions of Tefluthrin on Rat Na(v)1.7 Voltage-Gated Sodium Channels Expressed in Xenopus Oocytes. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2011; 101:21-26. [PMID: 21966053 PMCID: PMC3181098 DOI: 10.1016/j.pestbp.2011.06.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
In rats expression of the Na(v)1.7 voltage-gated sodium channel isoform is restricted to the peripheral nervous system and is abundant in the sensory neurons of the dorsal root ganglion. We expressed the rat Na(v)1.7 sodium channel α subunit together with the rat auxiliary β1 and β2 subunits in Xenopus laevis oocytes and assessed the effects of the pyrethroid insecticide tefluthrin on the expressed currents using the two-electrode voltage clamp method. Tefluthrin at 100 µM modified of Na(v)1.7 channels to prolong inactivation of the peak current during a depolarizing pulse, resulting in a marked "late current" at the end of a 40-ms depolarization, and induced a sodium tail current following repolarization. Tefluthrin modification was enhanced up to two-fold by the application of a train of up to 100 5-ms depolarizing prepulses. These effects of tefluthrin on Na(v)1.7 channels were qualitatively similar to its effects on rat Na(v)1.2, Na(v)1.3 and Na(v)1.6 channels assayed previously under identical conditions. However, Na(v)1.7 sodium channels were distinguished by their low sensitivity to modification by tefluthrin, especially compared to Na(v)1.3 and Na(v)1.6 channels. It is likely that Na(v)1.7 channels contribute significantly to the tetrodotoxin-sensitive, pyrethroid-resistant current found in cultured dorsal root ganglion neurons. We aligned the complete amino acid sequences of four pyrethroid-sensitive isoforms (house fly Vssc1; rat Na(v)1.3, Na(v)1.6 and Na(v)1.8) and two pyrethroid-resistant isoforms (rat Na(v)1.2 and Na(v)1.7) and found only a single site, located in transmembrane segment 6 of homology domain I, at which the amino acid sequence was conserved among all four sensitive isoform sequences but differed in the two resistant isoform sequences. This position, corresponding to Val410 of the house fly Vssc1 sequence, also aligns with sites of multiple amino acid substitutions identified in the sodium channel sequences of pyrethroid-resistant insect populations. These results implicate this single amino acid polymorphism in transmembrane segment 6 of sodium channel homology domain I as a determinant of the differential pyrethroid sensitivity of rat sodium channel isoforms.
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Affiliation(s)
- Jianguo Tan
- Insecticide Toxicology Laboratory, Department of Entomology, New York State Agricultural Experiment Station, Cornell University, Geneva, New York 14456, USA
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85
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Kis-Toth K, Hajdu P, Bacskai I, Szilagyi O, Papp F, Szanto A, Posta E, Gogolak P, Panyi G, Rajnavolgyi E. Voltage-Gated Sodium Channel Nav1.7 Maintains the Membrane Potential and Regulates the Activation and Chemokine-Induced Migration of a Monocyte-Derived Dendritic Cell Subset. THE JOURNAL OF IMMUNOLOGY 2011; 187:1273-80. [DOI: 10.4049/jimmunol.1003345] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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86
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Ahn HS, Black JA, Zhao P, Tyrrell L, Waxman SG, Dib-Hajj SD. Nav1.7 is the predominant sodium channel in rodent olfactory sensory neurons. Mol Pain 2011; 7:32. [PMID: 21569247 PMCID: PMC3101130 DOI: 10.1186/1744-8069-7-32] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Accepted: 05/10/2011] [Indexed: 12/19/2022] Open
Abstract
Background Voltage-gated sodium channel Nav1.7 is preferentially expressed in dorsal root ganglion (DRG) and sympathetic neurons within the peripheral nervous system. Homozygous or compound heterozygous loss-of-function mutations in SCN9A, the gene which encodes Nav1.7, cause congenital insensitivity to pain (CIP) accompanied by anosmia. Global knock-out of Nav1.7 in mice is neonatal lethal reportedly from starvation, suggesting anosmia. These findings led us to hypothesize that Nav1.7 is the main sodium channel in the peripheral olfactory sensory neurons (OSN, also known as olfactory receptor neurons). Methods We used multiplex PCR-restriction enzyme polymorphism, in situ hybridization and immunohistochemistry to determine the identity of sodium channels in rodent OSNs. Results We show here that Nav1.7 is the predominant sodium channel transcript, with low abundance of other sodium channel transcripts, in olfactory epithelium from rat and mouse. Our in situ hybridization data show that Nav1.7 transcripts are present in rat OSNs. Immunostaining of Nav1.7 and Nav1.6 channels in rat shows a complementary accumulation pattern with Nav1.7 in peripheral presynaptic OSN axons, and Nav1.6 primarily in postsynaptic cells and their dendrites in the glomeruli of the olfactory bulb within the central nervous system. Conclusions Our data show that Nav1.7 is the dominant sodium channel in rat and mouse OSN, and may explain anosmia in Nav1.7 null mouse and patients with Nav1.7-related CIP.
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Affiliation(s)
- Hye-Sook Ahn
- Department of Neurology, Yale University School of Medicine, New Haven, 06520, USA
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87
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Lopez-Santiago LF, Brackenbury WJ, Chen C, Isom LL. Na+ channel Scn1b gene regulates dorsal root ganglion nociceptor excitability in vivo. J Biol Chem 2011; 286:22913-23. [PMID: 21555511 DOI: 10.1074/jbc.m111.242370] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nociceptive dorsal root ganglion (DRG) neurons express tetrodotoxin-sensitive (TTX-S) and -resistant (TTX-R) Na(+) current (I(Na)) mediated by voltage-gated Na(+) channels (VGSCs). In nociceptive DRG neurons, VGSC β2 subunits, encoded by Scn2b, selectively regulate TTX-S α subunit mRNA and protein expression, ultimately resulting in changes in pain sensitivity. We hypothesized that VGSCs in nociceptive DRG neurons may also be regulated by β1 subunits, encoded by Scn1b. Scn1b null mice are models of Dravet Syndrome, a severe pediatric encephalopathy. Many physiological effects of Scn1b deletion on CNS neurons have been described. In contrast, little is known about the role of Scn1b in peripheral neurons in vivo. Here we demonstrate that Scn1b null DRG neurons exhibit a depolarizing shift in the voltage dependence of TTX-S I(Na) inactivation, reduced persistent TTX-R I(Na), a prolonged rate of recovery of TTX-R I(Na) from inactivation, and reduced cell surface expression of Na(v)1.9 compared with their WT littermates. Investigation of action potential firing shows that Scn1b null DRG neurons are hyperexcitable compared with WT. Consistent with this, transient outward K(+) current (I(to)) is significantly reduced in null DRG neurons. We conclude that Scn1b regulates the electrical excitability of nociceptive DRG neurons in vivo by modulating both I(Na) and I(K).
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Affiliation(s)
- Luis F Lopez-Santiago
- Department of Pharmacology, University of Michigan, Ann Arbor, Michigan 48109-0632, USA
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88
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Blockade of persistent sodium currents contributes to the riluzole-induced inhibition of spontaneous activity and oscillations in injured DRG neurons. PLoS One 2011; 6:e18681. [PMID: 21541342 PMCID: PMC3081829 DOI: 10.1371/journal.pone.0018681] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2010] [Accepted: 03/11/2011] [Indexed: 11/19/2022] Open
Abstract
In addition to a fast activating and immediately inactivating inward sodium current, many types of excitable cells possess a noninactivating or slowly inactivating component: the persistent sodium current (INaP). The INaP is found in normal primary sensory neurons where it is mediated by tetrodotoxin-sensitive sodium channels. The dorsal root ganglion (DRG) is the gateway for ectopic impulses that originate in pathological pain signals from the periphery. However, the role of INaP in DRG neurons remains unclear, particularly in neuropathic pain states. Using in vivo recordings from single medium- and large-diameter fibers isolated from the compressed DRG in Sprague-Dawley rats, we show that local application of riluzole, which blocks the INaP, also inhibits the spontaneous activity of A-type DRG neurons in a dose-dependent manner. Significantly, riluzole also abolished subthreshold membrane potential oscillations (SMPOs), although DRG neurons still responded to intracellular current injection with a single full-sized spike. In addition, the INaP was enhanced in medium- and large-sized neurons of the compressed DRG, while bath-applied riluzole significantly inhibited the INaP without affecting the transient sodium current (INaT). Taken together, these results demonstrate for the first time that the INaP blocker riluzole selectively inhibits INaP and thereby blocks SMPOs and the ectopic spontaneous activity of injured A-type DRG neurons. This suggests that the INaP of DRG neurons is a potential target for treating neuropathic pain at the peripheral level.
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89
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Ho C, O'Leary ME. Single-cell analysis of sodium channel expression in dorsal root ganglion neurons. Mol Cell Neurosci 2011; 46:159-66. [PMID: 20816971 PMCID: PMC3005531 DOI: 10.1016/j.mcn.2010.08.017] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 08/19/2010] [Accepted: 08/26/2010] [Indexed: 01/08/2023] Open
Abstract
Sensory neurons of the dorsal root ganglia (DRG) express multiple voltage-gated sodium (Na) channels that substantially differ in gating kinetics and pharmacology. Small-diameter (<25 μm) neurons isolated from the rat DRG express a combination of fast tetrodotoxin-sensitive (TTX-S) and slow TTX-resistant (TTX-R) Na currents while large-diameter neurons (>30 μm) predominately express fast TTX-S Na current. Na channel expression was further investigated using single-cell RT-PCR to measure the transcripts present in individually harvested DRG neurons. Consistent with cellular electrophysiology, the small neurons expressed transcripts encoding for both TTX-S (Nav1.1, Nav1.2, Nav1.6, and Nav1.7) and TTX-R (Nav1.8 and Nav1.9) Na channels. Nav1.7, Nav1.8 and Nav1.9 were the predominant Na channels expressed in the small neurons. The large neurons highly expressed TTX-S isoforms (Nav1.1, Nav1.6, and Nav1.7) while TTX-R channels were present at comparatively low levels. A unique subpopulation of the large neurons was identified that expressed TTX-R Na current and high levels of Nav1.8 transcript. DRG neurons also displayed substantial differences in the expression of neurofilaments (NF200, peripherin) and Necl-1, a neuronal adhesion molecule involved in myelination. The preferential expression of NF200 and Necl-1 suggests that large-diameter neurons give rise to thick myelinated axons. Small-diameter neurons expressed peripherin, but reduced levels of NF200 and Necl-1, a pattern more consistent with thin unmyelinated axons. Single-cell analysis of Na channel transcripts indicates that TTX-S and TTX-R Na channels are differentially expressed in large myelinated (Nav1.1, Nav1.6, and Nav1.7) and small unmyelinated (Nav1.7, Nav1.8, and Nav1.9) sensory neurons.
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Affiliation(s)
- Cojen Ho
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, 1020 Locust Street, JAH 265, Philadelphia, PA 19107, USA
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90
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Dabby R, Sadeh M, Gilad R, Lampl Y, Cohen S, Inbar S, Leshinsky-Silver E. Chronic non-paroxysmal neuropathic pain - Novel phenotype of mutation in the sodium channel SCN9A gene. J Neurol Sci 2010; 301:90-2. [PMID: 21094958 DOI: 10.1016/j.jns.2010.10.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2010] [Revised: 09/29/2010] [Accepted: 10/04/2010] [Indexed: 12/19/2022]
Abstract
BACKGROUND Gain-of-function mutations in the SCN9A gene (encoding to NaV1.7 voltage-gated sodium channel) cause two rare paroxysmal pain disorders: inherited erythromelalgia (IEM) and paroxysmal extreme pain disorder (PEDP). These phenotypes are characterized by episodic extreme localized pain with cutaneous autonomic signs. So far, no other phenotypes have been associated with mutation in the SCN9A gene. OBJECTIVE To investigate mutations in the SCN9A gene in patients with chronic non-paroxysmal neuropathic pain. PATIENTS 9 patients with chronic severe unexplained neuropathic pain. RESULTS Of the nine patients one had predicted pathologic mutations in the SCN9A gene. This patient had a heterozygous change of n.4648 T-C in exon 27 resulting in a substitution of W1550R, a highly conserved amino acid, predicting damage in the transmembrane S2 region, repeat IV. This mutation was not found in 50 controls. CONCLUSIONS SCN9A mutations cause pain syndromes other than IEM and PEPD. These mutations should be considered in patients with resistant unexplained chronic neuropathic pain.
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Affiliation(s)
- Ron Dabby
- Department of Neurology, Wolfson Medical Center, Holon, Israel; Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel.
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91
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Staud R, Price DD, Janicke D, Andrade E, Hadjipanayis AG, Eaton WT, Kaplan L, Wallace MR. Two novel mutations of SCN9A (Nav1.7) are associated with partial congenital insensitivity to pain. Eur J Pain 2010; 15:223-30. [PMID: 20692858 DOI: 10.1016/j.ejpain.2010.07.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2010] [Revised: 06/13/2010] [Accepted: 07/03/2010] [Indexed: 10/19/2022]
Abstract
Insensitivity to pain is a rare disorder that is commonly associated with Hereditary Sensory and Autonomic Neuropathies (HSAN I-V) resulting often in autonomic dysfunction and premature death. Very few individuals have been reported with pain insensitivity lacking such autonomic neuropathies. We performed genetic, neurologic, psychological, and psychophysical evaluations in such an individual (OMIM 243000) and her first degree relatives. Sequence analysis of genomic DNA revealed two novel SCN9A mutations in this index case (IC). One was a non-conservative missense mutation (C1719R) in exon 26 present only in the IC and one parent. Further sequence analysis of the child's DNA revealed a 1-bp splice donor deletion in intron 17 which was also present in the other parent and one sibling. Detailed psychophysical testing was used to phenotypically characterize the IC, her family members, and 10 matched normal controls. Similar to family members and controls the IC showed normal somatosensory functioning for non-nociceptive mechanoreception and warmth. However, she demonstrated diminished ability to detect cool temperatures combined with profound deficits in heat and mechanical nociception. Congenital insensitivity to pain in our IC was associated with two novel SCN9A mutations which most likely resulted in a Nav1.7 channelopathy. However, in contrast to individuals with other SCN9A mutations, the observed pain insensitivity was relative and not absolute, which may be consistent with hypomorphic effects of one or both mutations. The ability to sense at least some danger signals may be advantageous and ameliorate the otherwise increased morbidity and mortality of some individuals with congenital insensitivity to pain.
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Affiliation(s)
- Roland Staud
- Department of Medicine, University of Florida, Gainesville, FL 32610, United States.
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92
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Kurban M, Wajid M, Shimomura Y, Christiano AM. A nonsense mutation in the SCN9A gene in congenital insensitivity to pain. Dermatology 2010; 221:179-83. [PMID: 20628234 DOI: 10.1159/000314692] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2010] [Accepted: 04/29/2010] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Congenital insensitivity to pain (CIP) (OMIM 243000) is a rare autosomal-recessive disorder. Clinically, CIP is characterized by insensitivity to all modalities of pain except neuropathic pain, and recurrent injuries frequently go unnoticed. CIP is caused by mutations in the SCN9A gene encoding for the Na1.7 channel. METHODS We analyzed the DNA from members of a consanguineous Pakistani family for mutations in the SCN9A gene through direct sequencing after performing linkage studies. RESULTS We identified a novel missense mutation designated R523X in all affected individuals. A screening assay ruled out the possibility of polymorphism. CONCLUSION We identified a novel mutation in the Na1.7 channel leading to CIP, extending the spectrum of mutations in the Na1.7 channel, and enhancing our understanding of the physiology of pain.
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Affiliation(s)
- Mazen Kurban
- Department of Dermatology, Columbia University, New York, NY, USA
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93
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Choi JS, Cheng X, Foster E, Leffler A, Tyrrell L, te Morsche RHM, Eastman EM, Jansen HJ, Huehne K, Nau C, Dib-Hajj SD, Drenth JPH, Waxman SG. Alternative splicing may contribute to time-dependent manifestation of inherited erythromelalgia. Brain 2010; 133:1823-35. [DOI: 10.1093/brain/awq114] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Stürzebecher AS, Hu J, Smith ESJ, Frahm S, Santos-Torres J, Kampfrath B, Auer S, Lewin GR, Ibañez-Tallon I. An in vivo tethered toxin approach for the cell-autonomous inactivation of voltage-gated sodium channel currents in nociceptors. J Physiol 2010; 588:1695-707. [PMID: 20308253 PMCID: PMC2887988 DOI: 10.1113/jphysiol.2010.187112] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2010] [Accepted: 03/16/2010] [Indexed: 11/08/2022] Open
Abstract
Understanding information flow in sensory pathways requires cell-selective approaches to manipulate the activity of defined neurones. Primary afferent nociceptors, which detect painful stimuli, are enriched in specific voltage-gated sodium channel (VGSC) subtypes. Toxins derived from venomous animals can be used to dissect the contributions of particular ion currents to cell physiology. Here we have used a transgenic approach to target a membrane-tethered isoform of the conotoxin MrVIa (t-MrVIa) only to nociceptive neurones in mice. T-MrVIa transgenic mice show a 44 +/- 7% reduction of tetrodotoxin-resistant (TTX-R) VGSC current densities. This inhibition is permanent, reversible and does not result in functional upregulation of TTX-sensitive (TTX-S) VGSCs, voltage-gated calcium channels (VGCCs) or transient receptor potential (TRP) channels present in nociceptive neurones. As a consequence of the reduction of TTX-R VGSC currents, t-MrVIa transgenic mice display decreased inflammatory mechanical hypersensitivity, cold pain insensitivity and reduced firing of cutaneous C-fibres sensitive to noxious cold temperatures. These data validate the use of genetically encoded t-toxins as a powerful tool to manipulate VGSCs in specific cell types within the mammalian nervous system. This novel genetic methodology can be used for circuit mapping and has the key advantage that it enables the dissection of the contribution of specific ionic currents to neuronal function and to behaviour.
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Affiliation(s)
- Annika S Stürzebecher
- Molecular Neurobiology group, Department of Neuroscience, Max-Delbrück Center for Molecular Medicine, Robert-Rössle Strasse 10, 13125 Berlin, Germany
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95
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Cheng X, Dib-Hajj SD, Tyrrell L, Wright DA, Fischer TZ, Waxman SG. Mutations at opposite ends of the DIII/S4-S5 linker of sodium channel Na V 1.7 produce distinct pain disorders. Mol Pain 2010; 6:24. [PMID: 20429905 PMCID: PMC2876140 DOI: 10.1186/1744-8069-6-24] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2010] [Accepted: 04/29/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Two groups of gain-of-function mutations in sodium channel NaV1.7, which are expressed in dorsal root ganglion (DRG) neurons, produce two clinically-distinct pain syndromes - inherited erythromelalgia (IEM) and paroxysmal extreme pain disorder (PEPD). IEM is characterized by intermittent burning pain and skin redness in the feet or hands, triggered by warmth or mild exercise, while PEPD is characterized by episodes of rectal, ocular and mandibular pain accompanied with skin flushing, triggered by bowel movement and perianal stimulation. Most of the IEM mutations are located within channel domains I and II, while most of the PEPD mutations are located within domains III and IV. The structural dichotomy parallels the biophysical effects of the two types of mutations, with IEM mutations shifting voltage-dependence of NaV1.7 activation in a hyperpolarized direction, and PEPD mutations shifting fast-inactivation of NaV1.7 in a depolarized direction. While four IEM and four PEPD mutations are located within cytoplasmic linkers joining segments 4 and 5 (S4-S5 linkers) in the different domains (IEM: domains I and II; PEPD: domains III and IV), no S4-S5 linker has been reported to house both IEM and PEPD mutations thus far. RESULTS We have identified a new IEM mutation P1308L within the C-terminus of the DIII/S4-S5 linker of NaV1.7, ten amino acids from a known PEPD mutation V1298F which is located within the N-terminus of this linker. We used voltage-clamp to compare the biophysical properties of the two mutant channels and current-clamp to study their effects on DRG neuron excitability. We confirm that P1308L and V1298F behave as prototypical IEM and PEPD mutations, respectively. We also show that DRG neurons expressing either P1308L or V1298F become hyperexcitable, compared to DRG neurons expressing wild-type channels. CONCLUSIONS Our results provide evidence for differential roles of the DIII/S4-S5 linker N- and C-termini in channel inactivation and activation, and demonstrate the cellular basis for pain in patients carrying these mutations.
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Affiliation(s)
- Xiaoyang Cheng
- Department of Neurology and Center for Neuroscience & Regeneration Research, Yale University School of Medicine, New Haven, CT, USA
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96
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Abstract
Nociception is essential for survival whereas pathological pain is maladaptive and often unresponsive to pharmacotherapy. Voltage-gated sodium channels, Na(v)1.1-Na(v)1.9, are essential for generation and conduction of electrical impulses in excitable cells. Human and animal studies have identified several channels as pivotal for signal transmission along the pain axis, including Na(v)1.3, Na(v)1.7, Na(v)1.8, and Na(v)1.9, with the latter three preferentially expressed in peripheral sensory neurons and Na(v)1.3 being upregulated along pain-signaling pathways after nervous system injuries. Na(v)1.7 is of special interest because it has been linked to a spectrum of inherited human pain disorders. Here we review the contribution of these sodium channel isoforms to pain.
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Affiliation(s)
- Sulayman D Dib-Hajj
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06510, USA
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97
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Dai A, Temporal S, Schulz DJ. Cell-specific patterns of alternative splicing of voltage-gated ion channels in single identified neurons. Neuroscience 2010; 168:118-29. [PMID: 20211705 DOI: 10.1016/j.neuroscience.2010.03.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2009] [Revised: 02/25/2010] [Accepted: 03/02/2010] [Indexed: 11/28/2022]
Abstract
CbNa(v) and CbIH encode channels that carry voltage-gated sodium and hyperpolarization activated cation currents respectively in the crab, Cancer borealis. We cloned and sequenced full length cDNAs for both CbNa(v) and CbIH and found nine different regions of alternative splicing for the CbNa(v) gene and four regions of alternative splicing for CbIH. We used RT-PCR to determine tissue-specific differences in splicing of both channel genes among cardiac muscle, skeletal muscle, brain, and stomatogastric ganglion (STG) tissue. We then examined the splice variant isoforms present in single, unambiguously identified neurons of the STG. We found cell-type specific patterns of alternative splicing for CbNa(v), indicating unique cell-specific pattern of post-transcriptional modification. Furthermore, we detected possible differences in cellular localization of alternatively spliced CbNa(v) transcripts; distinct mRNA isoforms are present between the cell somata and the axons of the neurons. In contrast, we found no qualitative differences among different cell types for CbIH variants present, although this analysis did not represent the full spectrum of all possible CbIH variants. CbIH mRNA was not detected in axon samples. Finally, although cell-type specific patterns of splicing were detected for CbNa(v), the same cell type within and between animals also displayed variability in which splice forms were detected. These results indicate that channel splicing is differentially regulated at the level of single neurons of the same neural network, providing yet another mechanism by which cell-specific neuronal output can be achieved.
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Affiliation(s)
- A Dai
- Department of Biological Sciences, University of Missouri, Columbia, MO, USA
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98
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Estacion M, Choi JS, Eastman EM, Lin Z, Li Y, Tyrrell L, Yang Y, Dib-Hajj SD, Waxman SG. Can robots patch-clamp as well as humans? Characterization of a novel sodium channel mutation. J Physiol 2010; 588:1915-27. [PMID: 20123784 DOI: 10.1113/jphysiol.2009.186114] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Ion channel missense mutations cause disorders of excitability by changing channel biophysical properties. As an increasing number of new naturally occurring mutations have been identified, and the number of other mutations produced by molecular approaches such as in situ mutagenesis has increased, the need for functional analysis by patch-clamp has become rate limiting. Here we compare a patch-clamp robot using planar-chip technology with human patch-clamp in a functional assessment of a previously undescribed Nav1.7 sodium channel mutation, S211P, which causes erythromelalgia. This robotic patch-clamp device can increase throughput (the number of cells analysed per day) by 3- to 10-fold. Both modes of analysis show that the mutation hyperpolarizes activation voltage dependence (8 mV by manual profiling, 11 mV by robotic profiling), alters steady-state fast inactivation so that it requires an additional Boltzmann function for a second fraction of total current (approximately 20% manual, approximately 40% robotic), and enhances slow inactivation (hyperpolarizing shift--15 mV by human,--13 mV robotic). Manual patch-clamping demonstrated slower deactivation and enhanced (approximately 2-fold) ramp response for the mutant channel while robotic recording did not, possibly due to increased temperature and reduced signal-to-noise ratio on the robotic platform. If robotic profiling is used to screen ion channel mutations, we recommend that each measurement or protocol be validated by initial comparison to manual recording. With this caveat, we suggest that, if results are interpreted cautiously, robotic patch-clamp can be used with supervision and subsequent confirmation from human physiologists to facilitate the initial profiling of a variety of electrophysiological parameters of ion channel mutations.
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Affiliation(s)
- M Estacion
- Department of Neurology, Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510, USA
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99
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Absence of pain with hyperhidrosis: A new syndrome where vascular afferents may mediate cutaneous sensation. Pain 2009; 147:287-98. [DOI: 10.1016/j.pain.2009.09.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2009] [Revised: 09/01/2009] [Accepted: 09/09/2009] [Indexed: 12/22/2022]
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100
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Fischer TZ, Waxman SG. Familial pain syndromes from mutations of the Nav1.7 sodium channel. Ann N Y Acad Sci 2009; 1184:196-207. [DOI: 10.1111/j.1749-6632.2009.05110.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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