101
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Momin A, Wood JN. Sensory neuron voltage-gated sodium channels as analgesic drug targets. Curr Opin Neurobiol 2008; 18:383-8. [PMID: 18824099 DOI: 10.1016/j.conb.2008.08.017] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2008] [Revised: 08/28/2008] [Accepted: 08/28/2008] [Indexed: 11/19/2022]
Abstract
Voltage-gated sodium channels are crucial determinants of neuronal excitability and signalling; some specific channel subtypes have been implicated in a number of chronic pain conditions. Human genetic studies show gain-of-function or loss-of-function mutations in Na(V)1.7 lead to an enhancement or lack of pain, respectively, whilst transgenic mouse and knockdown studies have implicated Na(V)1.3, Na(V)1.8 and Na(V)1.9 in peripheral pain pathways. The development of subtype-specific sodium channel blockers, though clearly desirable, has been technically challenging. Recent advances exploiting both natural products and small molecule selective channel blockers have demonstrated that this approach to pain control is feasible. These observations provide a rationale for the development of new analgesics without the side effect profile of broad spectrum sodium channel blockers.
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Affiliation(s)
- Aliakmal Momin
- Molecular Nociception, Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, United Kingdom.
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102
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Fukuoka T, Kobayashi K, Yamanaka H, Obata K, Dai Y, Noguchi K. Comparative study of the distribution of the alpha-subunits of voltage-gated sodium channels in normal and axotomized rat dorsal root ganglion neurons. J Comp Neurol 2008; 510:188-206. [PMID: 18615542 DOI: 10.1002/cne.21786] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
We compared the distribution of the alpha-subunit mRNAs of voltage-gated sodium channels Nav1.1-1.3 and Nav1.6-1.9 and a related channel, Nax, in histochemically identified neuronal subpopulations of the rat dorsal root ganglia (DRG). In the naïve DRG, the expression of Nav1.1 and Nav1.6 was restricted to A-fiber neurons, and they were preferentially expressed by TrkC neurons, suggesting that proprioceptive neurons possess these channels. Nav1.7, -1.8, and -1.9 mRNAs were more abundant in C-fiber neurons compared with A-fiber ones. Nax was evenly expressed in both populations. Although Nav1.8 and -1.9 were preferentially expressed by TrkA neurons, other alpha-subunits were expressed independently of TrkA expression. Actually, all IB4(+) neurons expressed both Nav1.8 and -1.9, and relatively limited subpopulations of IB4(+) neurons (3% and 12%, respectively) expressed Nav1.1 and/or Nav1.6. These findings provide useful information in interpreting the electrophysiological characteristics of some neuronal subpopulations of naïve DRG. After L5 spinal nerve ligation, Nav1.3 mRNA was up-regulated mainly in A-fiber neurons in the ipsilateral L5 DRG. Although previous studies demonstrated that nerve growth factor (NGF) and glial cell-derived neurotrophic factor (GDNF) reversed this up-regulation, the Nav1.3 induction was independent of either TrkA or GFRalpha1 expression, suggesting that the induction of Nav1.3 may be one of the common responses of axotomized DRG neurons without a direct relationship to NGF/GDNF supply.
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Affiliation(s)
- Tetsuo Fukuoka
- Department of Anatomy and Neuroscience, Hyogo College of Medicine, Nishinomiya, Hyogo 663-8501, Japan.
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103
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Governing role of primary afferent drive in increased excitation of spinal nociceptive neurons in a model of sciatic neuropathy. Exp Neurol 2008; 214:219-28. [PMID: 18773893 DOI: 10.1016/j.expneurol.2008.08.003] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2008] [Revised: 07/31/2008] [Accepted: 08/10/2008] [Indexed: 01/07/2023]
Abstract
Previously we reported that the cuff model of peripheral neuropathy, in which a 2 mm polyethylene tube is implanted around the sciatic nerve, exhibits aspects of neuropathic pain behavior in rats similar to those in humans and causes robust hyperexcitation of spinal nociceptive dorsal horn neurons. The mechanisms mediating this increased excitation are not known and remain a key unresolved question in models of peripheral neuropathy. In anesthetized adult male Sprague-Dawley rats 2-6 weeks after cuff implantation we found that elevated discharge rate of single lumbar (L(3-4)) wide dynamic range (WDR) neurons persists despite acute spinal transection (T9) but is reversed by local conduction block of the cuff-implanted sciatic nerve; lidocaine applied distal to the cuff (i.e. between the cuff and the cutaneous receptive field) decreased spontaneous baseline discharge of WDR dorsal horn neurons approximately 40% (n=18) and when applied subsequently proximal to the cuff, i.e. between the cuff and the spinal cord, it further reduced spontaneous discharge by approximately 60% (n=19; P<0.05 proximal vs. distal) to a level that was not significantly different from that of naive rats. Furthermore, in cuff-implanted rats WDR neurons (n=5) responded to mechanical cutaneous stimulation with an exaggerated afterdischarge which was reversed entirely by proximal nerve conduction block. These results demonstrate that the hyperexcited state of spinal dorsal horn neurons observed in this model of peripheral neuropathy is not maintained by tonic descending facilitatory mechanisms. Rather, on-going afferent discharges originating from the sciatic nerve distal to, at, and proximal to the cuff maintain the synaptically-mediated gain in discharge of spinal dorsal horn WDR neurons and hyperresponsiveness of these neurons to cutaneous stimulation. Our findings reveal that ectopic afferent activity from multiple regions along peripheral nerves may drive CNS changes and the symptoms of pain associated with peripheral neuropathy.
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104
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Huang HL, Cendan CM, Roza C, Okuse K, Cramer R, Timms JF, Wood JN. Proteomic profiling of neuromas reveals alterations in protein composition and local protein synthesis in hyper-excitable nerves. Mol Pain 2008; 4:33. [PMID: 18700027 PMCID: PMC2525634 DOI: 10.1186/1744-8069-4-33] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2008] [Accepted: 08/12/2008] [Indexed: 12/22/2022] Open
Abstract
Neuropathic pain may arise following peripheral nerve injury though the molecular mechanisms associated with this are unclear. We used proteomic profiling to examine changes in protein expression associated with the formation of hyper-excitable neuromas derived from rodent saphenous nerves. A two-dimensional difference gel electrophoresis (2D-DIGE) profiling strategy was employed to examine protein expression changes between developing neuromas and normal nerves in whole tissue lysates. We found around 200 proteins which displayed a >1.75-fold change in expression between neuroma and normal nerve and identified 55 of these proteins using mass spectrometry. We also used immunoblotting to examine the expression of low-abundance ion channels Nav1.3, Nav1.8 and calcium channel alpha2delta-1 subunit in this model, since they have previously been implicated in neuronal hyperexcitability associated with neuropathic pain. Finally, S35methionine in vitro labelling of neuroma and control samples was used to demonstrate local protein synthesis of neuron-specific genes. A number of cytoskeletal proteins, enzymes and proteins associated with oxidative stress were up-regulated in neuromas, whilst overall levels of voltage-gated ion channel proteins were unaffected. We conclude that altered mRNA levels reported in the somata of damaged DRG neurons do not necessarily reflect levels of altered proteins in hyper-excitable damaged nerve endings. An altered repertoire of protein expression, local protein synthesis and topological re-arrangements of ion channels may all play important roles in neuroma hyper-excitability.
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Affiliation(s)
- Hong-Lei Huang
- Molecular Nociception Group, NPP Department, UCL, Gower Street, London WC1E6BT, UK.
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105
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Tetrodotoxin inhibits the development and expression of neuropathic pain induced by paclitaxel in mice. Pain 2008; 137:520-531. [DOI: 10.1016/j.pain.2007.10.012] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2007] [Revised: 09/28/2007] [Accepted: 10/08/2007] [Indexed: 11/18/2022]
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106
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Wilson-Gerwing TD, Stucky CL, McComb GW, Verge VMK. Neurotrophin-3 significantly reduces sodium channel expression linked to neuropathic pain states. Exp Neurol 2008; 213:303-14. [PMID: 18601922 DOI: 10.1016/j.expneurol.2008.06.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2007] [Revised: 04/29/2008] [Accepted: 06/06/2008] [Indexed: 10/21/2022]
Abstract
Neuropathic pain resulting from chronic constriction injury (CCI) is critically linked to sensitization of peripheral nociceptors. Voltage gated sodium channels are major contributors to this state and their expression can be upregulated by nerve growth factor (NGF). We have previously demonstrated that neurotrophin-3 (NT-3) acts antagonistically to NGF in modulation of aspects of CCI-induced changes in trkA-associated nociceptor phenotype and thermal hyperalgesia. Thus, we hypothesized that exposure of neurons to increased levels of NT-3 would reduce expression of Na(v)1.8 and Na(v)1.9 in DRG neurons subject to CCI. In adult male rats, Na(v)1.8 and Na(v)1.9 mRNAs are expressed at high levels in predominantly small to medium size neurons. One week following CCI, there is reduced incidence of neurons expressing detectable Na(v)1.8 and Na(v)1.9 mRNA, but without a significant decline in mean level of neuronal expression, and similar findings observed immunohistochemically. There is also increased accumulation/redistribution of channel protein in the nerve most apparent proximal to the first constriction site. Intrathecal infusion of NT-3 significantly attenuates neuronal expression of Na(v)1.8 and Na(v)1.9 mRNA contralateral and most notably, ipsilateral to CCI, with a similar impact on relative protein expression at the level of the neuron and constricted nerve. We also observe reduced expression of the common neurotrophin receptor p75 in response to CCI that is not reversed by NT-3 in small to medium sized neurons and may confer an enhanced ability of NT-3 to signal via trkA, as has been previously shown in other cell types. These findings are consistent with an analgesic role for NT-3.
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Affiliation(s)
- Tracy D Wilson-Gerwing
- Department of Anatomy and Cell Biology, Cameco MS Neuroscience Research Center University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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107
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Huang ZJ, Song XJ. Differing alterations of sodium currents in small dorsal root ganglion neurons after ganglion compression and peripheral nerve injury. Mol Pain 2008; 4:20. [PMID: 18513405 PMCID: PMC2427019 DOI: 10.1186/1744-8069-4-20] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2008] [Accepted: 05/30/2008] [Indexed: 12/17/2022] Open
Abstract
Voltage-gated sodium channels play important roles in modulating dorsal root ganglion (DRG) neuron hyperexcitability and hyperalgesia after peripheral nerve injury or inflammation. We report that chronic compression of DRG (CCD) produces profound effect on tetrodotoxin-resistant (TTX-R) and tetrodotoxin-sensitive (TTX-S) sodium currents, which are different from that by chronic constriction injury (CCI) of the sciatic nerve in small DRG neurons. Whole cell patch-clamp recordings were obtained in vitro from L4 and/or L5 dissociated, small DRG neurons following in vivo DRG compression or nerve injury. The small DRG neurons were classified into slow and fast subtype neurons based on expression of the slow-inactivating TTX-R and fast-inactivating TTX-S Na+ currents. CCD treatment significantly reduced TTX-R and TTX-S current densities in the slow and fast neurons, but CCI selectively reduced the TTX-R and TTX-S current densities in the slow neurons. Changes in half-maximal potential (V1/2) and curve slope (k) of steady-state inactivation of Na+ currents were different in the slow and fast neurons after CCD and CCI treatment. The window current of TTX-R and TTX-S currents in fast neurons were enlarged by CCD and CCI, while only that of TTX-S currents in slow neurons was increased by CCI. The decay rate of TTX-S and both TTX-R and TTX-S currents in fast neurons were reduced by CCD and CCI, respectively. These findings provide a possible sodium channel mechanism underlying CCD-induced DRG neuron hyperexcitability and hyperalgesia and demonstrate a differential effect in the Na+ currents of small DRG neurons after somata compression and peripheral nerve injury. This study also points to a complexity of hyperexcitability mechanisms contributing to CCD and CCI hyperexcitability in small DRG neurons.
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Affiliation(s)
- Zhi-Jiang Huang
- Department of Neurobiology, Parker University Research Institute, Dallas, TX 75229, USA.
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108
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Drizin I, Gregg RJ, Scanio MJC, Shi L, Gross MF, Atkinson RN, Thomas JB, Johnson MS, Carroll WA, Marron BE, Chapman ML, Liu D, Krambis MJ, Shieh CC, Zhang X, Hernandez G, Gauvin DM, Mikusa JP, Zhu CZ, Joshi S, Honore P, Marsh KC, Roeloffs R, Werness S, Krafte DS, Jarvis MF, Faltynek CR, Kort ME. Discovery of potent furan piperazine sodium channel blockers for treatment of neuropathic pain. Bioorg Med Chem 2008; 16:6379-86. [PMID: 18501613 DOI: 10.1016/j.bmc.2008.05.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2008] [Revised: 04/30/2008] [Accepted: 05/02/2008] [Indexed: 11/18/2022]
Abstract
The synthesis and pharmacological characterization of a novel furan-based class of voltage-gated sodium channel blockers is reported. Compounds were evaluated for their ability to block the tetrodotoxin-resistant sodium channel Na(v)1.8 (PN3) as well as the Na(v)1.2 and Na(v)1.5 subtypes. Benchmark compounds from this series possessed enhanced potency, oral bioavailability, and robust efficacy in a rodent model of neuropathic pain, together with improved CNS and cardiovascular safety profiles compared to the clinically used sodium channel blockers mexiletine and lamotrigine.
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Affiliation(s)
- Irene Drizin
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, IL 60064, USA.
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109
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Gold MS. Na(+) channel blockers for the treatment of pain: context is everything, almost. Exp Neurol 2008; 210:1-6. [PMID: 18234194 PMCID: PMC2312090 DOI: 10.1016/j.expneurol.2007.12.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2007] [Revised: 11/30/2007] [Accepted: 12/03/2007] [Indexed: 12/17/2022]
Affiliation(s)
- Michael S Gold
- Department of Medicine, Division of Gastroenterology, Hepatology and Nutrition, University of Pittsburgh, Pittsburgh, PA 15213, USA.
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110
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Transcriptional and functional profiles of voltage-gated Na+ channels in injured and non-injured DRG neurons in the SNI model of neuropathic pain. Mol Cell Neurosci 2008; 37:196-208. [DOI: 10.1016/j.mcn.2007.09.007] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2007] [Revised: 09/12/2007] [Accepted: 09/17/2007] [Indexed: 11/20/2022] Open
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111
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Termin A, Martinborough E, Wilson D. Recent Advances in Voltage-Gated Sodium Channel Blockers: Therapeutic Potential as Drug Targets in the CNS. ANNUAL REPORTS IN MEDICINAL CHEMISTRY 2008. [DOI: 10.1016/s0065-7743(08)00003-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/12/2023]
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112
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Takeda Y, Ishida T, Tsutsui R, Toide K, Tanimoto-Mori S, Watanabe S, Kanai Y, Kamei C. Studies on Somnolence in the Daytime Caused by Drugs Used for Neuropathic Pain. J Pharmacol Sci 2008; 107:246-50. [DOI: 10.1254/jphs.08059fp] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
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113
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114
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Bermejo Velasco PE, Velasco Calvo R. Nuevos fármacos antiepilépticos y dolor neuropático. De la medicina molecular a la clínica. Med Clin (Barc) 2007; 129:542-50. [DOI: 10.1157/13111432] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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115
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Cummins TR, Sheets PL, Waxman SG. The roles of sodium channels in nociception: Implications for mechanisms of pain. Pain 2007; 131:243-257. [PMID: 17766042 PMCID: PMC2055547 DOI: 10.1016/j.pain.2007.07.026] [Citation(s) in RCA: 349] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2007] [Revised: 07/20/2007] [Accepted: 07/27/2007] [Indexed: 11/17/2022]
Abstract
Understanding the role of voltage-gated sodium channels in nociception may provide important insights into pain mechanisms. Voltage-gated sodium channels are critically important for electrogenesis and nerve impulse conduction, and a target for important clinically relevant analgesics such as lidocaine. Furthermore, within the last decade studies have shown that certain sodium channel isoforms are predominantly expressed in peripheral sensory neurons associated with pain sensation, and that the expression and functional properties of voltage-gated sodium channels in peripheral sensory neurons can be dynamically regulated following axonal injury or peripheral inflammation. These data suggest that specific voltage-gated sodium channels may play crucial roles in nociception. Experiments with transgenic mice lines have clearly implicated Na(v)1.7, Na(v)1.8 and Na(v)1.9 in inflammatory, and possibly neuropathic, pain. However the most convincing and perhaps most exciting results regarding the role of voltage-gated sodium channels have come out recently from studies on human inherited disorders of nociception. Point mutations in Na(v)1.7 have been identified in patients with two distinct autosomal dominant severe chronic pain syndromes. Electrophysiological experiments indicate that these pain-associated mutations cause small yet significant changes in the gating properties of voltage-gated sodium channels that are likely to contribute substantially to the development of chronic pain. Equally exciting, recent studies indicate that recessive mutations in Na(v)1.7 that eliminate functional current can result in an apparent complete, and possibly specific, indifference to pain in humans, suggesting that isoform specific blockers could be very effective in treating pain. In this review we will examine what is known about the roles of voltage-gated sodium channels in nociception.
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Affiliation(s)
- Theodore R Cummins
- Department of Pharmacology and Toxicology, Stark Neurosciences Research Institute, Indiana University School of Medicine, 950 West Walnut Street, R2 468, Indianapolis, IN 46202, United States Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, United States Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510, United States Rehabilitation Research Center, Veterans Administration Connecticut Healthcare System, West Haven, CT 06516, United States
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116
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Affiliation(s)
- Donald J Kyle
- Discovery Research, Purdue Pharma L.P., 6 Cedar Brook Drive, Cranbury, New Jersey 08512, USA.
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117
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Kennedy JD. Neuropathic Pain: Molecular Complexity Underlies Continuing Unmet Medical Need. J Med Chem 2007; 50:2547-56. [PMID: 17489577 DOI: 10.1021/jm061023c] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jeffrey D Kennedy
- Neuroscience Discovery, Wyeth Research, CN 8000, Princeton, New Jersey 08543-8000, USA.
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118
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Abstract
Neuropathic pain occurs as a result of some form of injury to the nervous system. Although the basis of the disease remains to be fully elucidated, numerous studies have suggested a major role for ion channels in the pathogenesis of neuropathic pain. As Na+ channels play a fundamental role in not only the generation but also in the conduction of an action potential, they have received considerable attention in the aetiology of pain sensation and have become important pharmacological targets. In this review, the authors discuss the importance of specific Na+ channel isoforms in the pathophysiology of neuropathic pain and the present use of Na+ channel antagonists in the treatment of neuropathic pain.
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Affiliation(s)
- Nicholas James Hargus
- University of Virginia Health System, Department of Anesthesiology, Neuroscience Graduate Program, 1 Hospital Drive, Old Medical School, Charlottesville, VA 22908, USA
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119
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Modulatory effect of auxiliary β1 subunit on Nav1.3 voltage-gated sodium channel expressed in Xenopus oocyte. Chin Med J (Engl) 2007. [DOI: 10.1097/00029330-200704020-00021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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120
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Abstract
In this article, we review the key basic mechanisms associated with this phenomena and more recently identified mechanisms that are current areas of interest. Although many of these pain mechanisms apply throughout the body, we attempt to describe these mechanisms in the context of trigeminal pain.
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Affiliation(s)
- Michael A Henry
- Department of Endodontics, University of Texas Health Science Center at San Antonio School of Dentistry, Mail Code 7892, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA.
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121
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Abstract
Neuropathic pain remains a large unmet medical need. A number of therapeutic options exist, but efficacy and tolerability are less than satisfactory. Based on animal models and limited data from human patients, the pain and hypersensitivity that characterize neuropathic pain are associated with spontaneous discharges of normally quiescent nociceptors. Sodium channel blockers inhibit this spontaneous activity, reverse nerve injury-induced pain behavior in animals and alleviate neuropathic pain in humans. Several sodium channel subtypes are expressed primarily in sensory neurons and may contribute to the efficacy of sodium channel blockers. In this report, the authors review the current understanding of the role of sodium channels and of specific sodium channel subtypes in neuropathic pain signaling.
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Affiliation(s)
- Birgit T Priest
- Merck Research Laboratories, Department of Ion Channels, Rahway, NJ 07065, USA.
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122
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Affiliation(s)
- Wenrui Xie
- University of Cincinnati, Cincinnati, Ohio, USA.
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123
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Bibliography. Current world literature. Vasculitis syndromes. Curr Opin Rheumatol 2006; 19:81-5. [PMID: 17143101 DOI: 10.1097/bor.0b013e32801437a8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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124
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Crevits L. Brachioradial pruritus—A peculiar neuropathic disorder. Clin Neurol Neurosurg 2006; 108:803-5. [PMID: 16423451 DOI: 10.1016/j.clineuro.2005.12.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2005] [Revised: 10/18/2005] [Accepted: 12/01/2005] [Indexed: 11/30/2022]
Abstract
The case is presented of a middle-aged woman who suffered from lancinating itch on the dorsolateral aspect of the upper arm after a loco-regional injury, first on the right and later on the left side. Brachioradial pruritus (BRP) was diagnosed. Neurophysiologic examination was compatible with a neuropathy at the C5-C6 level, while a negative nerve root block supported an additional central impact. The presumed pathophysiology of BRP is discussed in terms of a neuropathic disorder. We suggest that damage from whatever cause from either the cutaneous nerves or from the more proximal sensory pathways may be the causative physiopathologic basis for this enigmatic disorder. BRP was refractory to different therapeutic approaches, except to lamotrigine. As BRP presents a therapeutic challenge, it seems important to report lamotrigine as a potential new therapy.
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Affiliation(s)
- L Crevits
- Department of Neurology, Ghent University Hospital, De Pintelaan 185, B-9000 Ghent, Belgium.
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125
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Nassar MA, Baker MD, Levato A, Ingram R, Mallucci G, McMahon SB, Wood JN. Nerve injury induces robust allodynia and ectopic discharges in Nav1.3 null mutant mice. Mol Pain 2006; 2:33. [PMID: 17052333 PMCID: PMC1630424 DOI: 10.1186/1744-8069-2-33] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2006] [Accepted: 10/19/2006] [Indexed: 01/21/2023] Open
Abstract
Changes in sodium channel activity and neuronal hyperexcitability contribute to neuropathic pain, a major clinical problem. There is strong evidence that the re-expression of the embryonic voltage-gated sodium channel subunit Nav1.3 underlies neuronal hyperexcitability and neuropathic pain. Here we show that acute and inflammatory pain behaviour is unchanged in global Nav1.3 mutant mice. Surprisingly, neuropathic pain also developed normally in the Nav1.3 mutant mouse. To rule out any genetic compensation mechanisms that may have masked the phenotype, we investigated neuropathic pain in two conditional Nav1.3 mutant mouse lines. We used Nav1.8-Cre mice to delete Nav1.3 in nociceptors at E14 and NFH-Cre mice to delete Nav1.3 throughout the nervous system postnatally. Again normal levels of neuropathic pain developed after nerve injury in both lines. Furthermore, ectopic discharges from damaged nerves were unaffected by the absence of Nav1.3 in global knock-out mice. Our data demonstrate that Nav1.3 is neither necessary nor sufficient for the development of nerve-injury related pain.
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Affiliation(s)
- Mohammed A Nassar
- Molecular Nociception Group, Department of Biology, University College London WC1E 6BT, UK
| | - Mark D Baker
- Molecular Nociception Group, Department of Biology, University College London WC1E 6BT, UK
| | - Alessandra Levato
- Molecular Nociception Group, Department of Biology, University College London WC1E 6BT, UK
| | - Rachel Ingram
- Centre for Neuroscience Research, Kings College London, London SE1 7EH, UK
| | - Giovanna Mallucci
- MRC Prion Unit and Department of Neurodegeneration. Institute of Neurology, Queen Square, London WC1N 3BG, UK
| | - Stephen B McMahon
- Centre for Neuroscience Research, Kings College London, London SE1 7EH, UK
| | - John N Wood
- Molecular Nociception Group, Department of Biology, University College London WC1E 6BT, UK
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126
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Abstract
Our knowledge of the ion channels, receptors and signalling mechanisms involved in pain pathophysiology, and which specific channels play a role in subtypes of pain such as neuropathic and inflammatory pain, has expanded considerably in recent years. It is now clear that in the neuropathic state the expression of certain channels is modified, and that these changes underlie the plasticity of responses that occur to generate inappropriate pain signals from normally trivial inputs. Pain is modulated by a subset of the voltage-gated sodium channels, including Nav1.3, Nav1.7, Nav1.8 and Nav1.9. These isoforms display unique expression patterns within specific tissues, and are either up- or down-regulated upon injury to the nervous system. Here we describe our current understanding of the roles of sodium channels in pain and nociceptive information processing, with a particular emphasis on neuropathic pain and drugs useful for the treatment of neuropathic pain that act through mechanisms involving block of sodium channels. One of the future challenges in the development of novel sodium channel blockers is to design and synthesise isoform-selective channel inhibitors. This should provide substantial benefits over existing pain treatments.
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Affiliation(s)
- Marc Rogers
- Xention Ltd., Iconix Park, Pampisford, Cambridge CB2 4EF, United Kingdom
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Matsutomi T, Nakamoto C, Zheng T, Kakimura JI, Ogata N. Multiple types of Na+ currents mediate action potential electrogenesis in small neurons of mouse dorsal root ganglia. Pflugers Arch 2006; 453:83-96. [PMID: 16838161 DOI: 10.1007/s00424-006-0104-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2005] [Revised: 04/12/2006] [Accepted: 05/02/2006] [Indexed: 10/24/2022]
Abstract
Small (<25 microm in diameter) neurons of the dorsal root ganglion (DRG) express multiple voltage-gated Na(+) channel subtypes, two of which being resistant to tetrodotoxin (TTX). Each subtype mediates Na(+) current with distinct kinetic property. However, it is not known how each type of Na(+) channel contributes to the generation of action potentials in small DRG neurons. Therefore, we investigated the correlation between Na(+) currents in voltage-clamp recordings and corresponding action potentials in current-clamp recordings, using wild-type (WT) and Na(V)1.8 knock-out (KO) mice, to clarify the action potential electrogenesis in small DRG neurons. We classified Na(+) currents in small DRG neurons into three categories on the basis of TTX sensitivity and kinetic properties, i.e., TTX-sensitive (TTX-S)/fast Na(+) current, TTX-resistant (TTX-R)/slow Na(+) current, and TTX-R/persistent Na(+) current. Our concurrent voltage- and current-clamp recordings from the same neuron revealed that the action potentials in WT small DRG neurons were mainly dependent on TTX-R/slow Na(+) current mediated by Na(V)1.8. It was surprising that a large portion of TTX-S/fast Na(+) current was switched off in WT small DRG neurons due to a hyperpolarizing shift of the steady-state inactivation (h (infinity)), whereas in KO small DRG neurons which are devoid of TTX-R/slow Na(+) current, the action potentials were generated by TTX-S/fast Na(+) current possibly through a compensatory shift of h (infinity) in the positive direction. We also confirmed that TTX-R/persistent Na(+) current mediated by Na(V)1.9 actually regulates subthreshold excitability in small DRG neurons. In addition, we demon strated that TTX-R/persistent Na(+) current can carry an action potential when the amplitude of this current was abnormally increased. Thus, our results indicate that the action potentials in small DRG neurons are generated and regulated with a combination of multiple mechanisms that may give rise to unique functional properties of small DRG neurons.
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Affiliation(s)
- Tomoya Matsutomi
- Department of Neurophysiology, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima 734-8551, Japan
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128
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Hains BC, Saab CY, Waxman SG. Alterations in Burst Firing of Thalamic VPL Neurons and Reversal by Nav1.3 Antisense After Spinal Cord Injury. J Neurophysiol 2006; 95:3343-52. [PMID: 16481457 DOI: 10.1152/jn.01009.2005] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We recently showed that spinal cord contusion injury (SCI) at the thoracic level induces pain-related behaviors and increased spontaneous discharges, hyperresponsiveness to innocuous and noxious peripheral stimuli, and enlarged receptive fields in neurons in the ventral posterolateral (VPL) nucleus of the thalamus. These changes are linked to the abnormal expression of Nav1.3, a rapidly repriming voltage-gated sodium channel. In this study, we examined the burst firing properties of VPL neurons after SCI. Adult male Sprague–Dawley rats underwent contusion SCI at the T9 level. Four weeks later, when Nav1.3 protein was upregulated within VPL neurons, extracellular unit recordings were made from VPL neurons in intact animals, those with SCI, and in SCI animals after receiving lumbar intrathecal injections of Nav1.3 antisense or mismatch oligodeoxynucleotides for 4 days. After SCI, VPL neurons with identifiable peripheral receptive fields showed rhythmic oscillatory burst firing with changes in discrete burst properties, and alternated among single-spike, burst, silent, and spindle wave firing modes. Nav1.3 antisense, but not mismatch, partially reversed alterations in burst firing after SCI. These results demonstrate several newly characterized changes in spontaneous burst firing properties of VPL neurons after SCI and suggest that abnormal expression of Nav1.3 contributes to these phenomena.
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Affiliation(s)
- Bryan C Hains
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut 06510, USA
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129
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Ilyin VI, Pomonis JD, Whiteside GT, Harrison JE, Pearson MS, Mark L, Turchin PI, Gottshall S, Carter RB, Nguyen P, Hogenkamp DJ, Olanrewaju S, Benjamin E, Woodward RM. Pharmacology of 2-[4-(4-Chloro-2-fluorophenoxy)phenyl]-pyrimidine-4-carboxamide: A Potent, Broad-Spectrum State-Dependent Sodium Channel Blocker for Treating Pain States. J Pharmacol Exp Ther 2006; 318:1083-93. [PMID: 16728593 DOI: 10.1124/jpet.106.104737] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Voltage-gated Na(+) channels may play important roles in establishing pathological neuronal hyperexcitability associated with chronic pain in humans. Na(+) channel blockers, such as carbamazepine (CBZ) and lamotrigine (LTG), are efficacious in treating neuropathic pain; however, their therapeutic utility is compromised by central nervous system side effects. We reasoned that it may be possible to gain superior control over pain states and, in particular, a better therapeutic index, by designing broad-spectrum Na(+) channel blockers with higher potency, faster onset kinetics, and greater levels of state dependence than existing drugs. 2-[4-(4-Chloro-2-fluorophenoxy)phenyl]-pyrimidine-4-carboxamide (PPPA) is a novel structural analog of the state-dependent Na(+) channel blocker V102862 [4-(4-fluorophenoxy)benzaldehyde semicarbazone]. Tested on recombinant rat Na(v)1.2 channels and native Na(+) currents in cultured rat dorsal root ganglion neurons, PPPA was approximately 1000 times more potent, had 2000-fold faster binding kinetics, and > or =10-fold higher levels of state dependence than CBZ and LTG. Tested in rat pain models against mechanical endpoints, PPPA had minimal effective doses of 1 to 3 mg/kg p.o. in partial sciatic nerve ligation, Freund's complete adjuvant, and postincisional pain. In all cases, efficacy was similar to clinically relevant comparators. Importantly, PPPA did not produce motor deficits in the accelerating Rotarod assay of ataxia at doses up to 30 mg/kg p.o., indicating a therapeutic index >10, which was superior to CBZ and LTG. Our experiments suggest that high-potency, broad-spectrum, state-dependent Na(+) channel blockers will have clinical utility for treating neuropathic, inflammatory, and postsurgical pain. Optimizing the biophysical parameters of broad-spectrum voltage-gated Na(+) channel blockers may lead to improved pain therapeutics.
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Affiliation(s)
- Victor I Ilyin
- Discovery Research, Purdue Pharma LP, Cranbury, NJ 08512, USA.
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130
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Amir R, Argoff CE, Bennett GJ, Cummins TR, Durieux ME, Gerner P, Gold MS, Porreca F, Strichartz GR. The Role of Sodium Channels in Chronic Inflammatory and Neuropathic Pain. THE JOURNAL OF PAIN 2006; 7:S1-29. [PMID: 16632328 DOI: 10.1016/j.jpain.2006.01.444] [Citation(s) in RCA: 243] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2005] [Revised: 01/13/2006] [Accepted: 01/20/2006] [Indexed: 11/25/2022]
Abstract
UNLABELLED Clinical and experimental data indicate that changes in the expression of voltage-gated sodium channels play a key role in the pathogenesis of neuropathic pain and that drugs that block these channels are potentially therapeutic. Clinical and experimental data also suggest that changes in voltage-gated sodium channels may play a role in inflammatory pain, and here too sodium-channel blockers may have therapeutic potential. The sodium-channel blockers of interest include local anesthetics, used at doses far below those that block nerve impulse propagation, and tricyclic antidepressants, whose analgesic effects may at least partly be due to blockade of sodium channels. Recent data show that local anesthetics may have pain-relieving actions via targets other than sodium channels, including neuronal G protein-coupled receptors and binding sites on immune cells. Some of these actions occur with nanomolar drug concentrations, and some are detected only with relatively long-term drug exposure. There are 9 isoforms of the voltage-gated sodium channel alpha-subunit, and several of the isoforms that are implicated in neuropathic and inflammatory pain states are expressed by somatosensory primary afferent neurons but not by skeletal or cardiovascular muscle. This restricted expression raises the possibility that isoform-specific drugs might be analgesic and lacking the cardiotoxicity and neurotoxicity that limit the use of current sodium-channel blockers. PERSPECTIVE Changes in the expression of neuronal voltage-gated sodium channels may play a key role in the pathogenesis of both chronic neuropathic and chronic inflammatory pain conditions. Drugs that block these channels may have therapeutic efficacy with doses that are far below those that impair nerve impulse propagation or cardiovascular function.
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Affiliation(s)
- Ron Amir
- Department of Cell and Animal Biology, Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
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131
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Akada Y, Ogawa S, Amano KI, Fukudome Y, Yamasaki F, Itoh M, Yamamoto I. Potent analgesic effects of a putative sodium channel blocker M58373 on formalin-induced and neuropathic pain in rats. Eur J Pharmacol 2006; 536:248-55. [PMID: 16603152 DOI: 10.1016/j.ejphar.2006.03.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2005] [Revised: 02/25/2006] [Accepted: 03/06/2006] [Indexed: 12/01/2022]
Abstract
M58373, 4-[2-(4-hydroxy-4-{[N-(4-isopropoxyphenyl)-N-methylamino]methyl}piperidin-1-yl)ethyl]benzonitrile monohydrochloride, is a novel compound, which has an inhibitory activity on neurotoxin binding to the site 2 of voltage-gated sodium channels. In this study, we investigated the effects of M58373 on substance P release from sensory neurons in vitro and pain behaviors/responses in rats, compared with mexiletine. M58373 (1-10 microM) inhibited veratridine-induced release of substance P from dorsal root ganglion cells. In the formalin test, oral M58373 (0.3-10 mg/kg) reduced the time spent in nociceptive behaviors only in the late phase. In the neuropathic pain model, oral M58373 (1-10 mg/kg) attenuated mechanical allodynia and heat hyperalgesia in the nerve-injured paw without affecting normal responses in the uninjured paw. In contrast, oral mexiletine (10-100 mg/kg) had a narrow therapeutic dose range in both models because of the adverse effects on the central nervous system. These results suggest that M58373 is a favorable prototype for novel anti-neuropathic pain agents.
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Affiliation(s)
- Yasushige Akada
- Pharmaceutical Research Center, Mochida Pharmaceutical Co., Ltd., 722 Jimba-aza-Uenohara, Gotemba, Shizuoka 412-8524, Japan.
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132
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Novel Sodium Channel Blockers for the Treatment of Neuropathic Pain. ANNUAL REPORTS IN MEDICINAL CHEMISTRY 2006. [DOI: 10.1016/s0065-7743(06)41004-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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