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Ambalavanar R, Dessem D. Emerging peripheral receptor targets for deep-tissue craniofacial pain therapies. J Dent Res 2009; 88:201-11. [PMID: 19329451 DOI: 10.1177/0022034508330176] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
While effective therapies are available for some types of craniofacial pain, treatments for deep-tissue craniofacial pain such as temporomandibular disorders are less efficacious. Several ion channels and receptors which are prominent in craniofacial nociceptive mechanisms have been identified on trigeminal primary afferent neurons. Many of these receptors and channels exhibit unusual distributions compared with extracranial regions. For example, expression of the ATP receptor P2X(3) is strongly implicated in nociception and is more abundant on trigeminal primary afferent neurons than analogous extracranial neurons, making them potentially productive targets specifically for craniofacial pain therapies. The initial part of this review therefore focuses on P2X(3) as a potential therapeutic target to treat deep-tissue craniofacial pain. In the trigeminal ganglion, P2X(3) receptors are often co-expressed with the nociceptive neuropeptides CGRP and SP. Therefore, we discuss the role of CGRP and SP in deep-tissue craniofacial pain and suggest that neuropeptide antagonists, which have shown promise for the treatment of migraine, may have wider therapeutic potential, including the treatment of deep-tissue craniofacial pain. P2X(3), TRPV1, and ASIC3 are often co-expressed in trigeminal neurons, implying the formation of functional complexes that allow craniofacial nociceptive neurons to respond synergistically to altered ATP and pH in pain. Future therapeutics for craniofacial pain thus might be more efficacious if targeted at combinations of P2X(3), CGRP, TRPV1, and ASIC3.
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Affiliation(s)
- R Ambalavanar
- Department of Neural and Pain Sciences and Program in Neuroscience, University of Maryland, Baltimore, MD 21201, USA
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252
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Xie W, Strong JA, Zhang JM. Early blockade of injured primary sensory afferents reduces glial cell activation in two rat neuropathic pain models. Neuroscience 2009; 160:847-57. [PMID: 19303429 DOI: 10.1016/j.neuroscience.2009.03.016] [Citation(s) in RCA: 114] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2008] [Revised: 03/05/2009] [Accepted: 03/09/2009] [Indexed: 12/16/2022]
Abstract
Satellite glial cells in the dorsal root ganglion (DRG), like the better-studied glia cells in the spinal cord, react to peripheral nerve injury or inflammation by activation, proliferation, and release of messengers that contribute importantly to pathological pain. It is not known how information about nerve injury or peripheral inflammation is conveyed to the satellite glial cells. Abnormal spontaneous activity of sensory neurons, observed in the very early phase of many pain models, is one plausible mechanism by which injured sensory neurons could activate neighboring satellite glial cells. We tested effects of locally inhibiting sensory neuron activity with sodium channel blockers on satellite glial cell activation in a rat spinal nerve ligation (SNL) model. SNL caused extensive satellite glial cell activation (as defined by glial fibrillary acidic protein [GFAP] immunoreactivity) which peaked on day 1 and was still observed on day 10. Perfusion of the axotomized DRG with the Na channel blocker tetrodotoxin (TTX) significantly reduced this activation at all time points. Similar findings were made with a more distal injury (spared nerve injury model), using a different sodium channel blocker (bupivacaine depot) at the injury site. Local DRG perfusion with TTX also reduced levels of nerve growth factor (NGF) in the SNL model on day 3 (when activated glia are an important source of NGF), without affecting the initial drop of NGF on day 1 (which has been attributed to loss of transport from target tissues). Local perfusion in the SNL model also significantly reduced microglia activation (OX-42 immunoreactivity) on day 3 and astrocyte activation (GFAP immunoreactivity) on day 10 in the corresponding dorsal spinal cord. The results indicate that early spontaneous activity in injured sensory neurons may play important roles in glia activation and pathological pain.
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Affiliation(s)
- W Xie
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, 231 Albert Sabin Way, Cincinnati, OH 45267-0531, USA
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253
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Cotrina ML, Nedergaard M. Physiological and pathological functions of P2X7 receptor in the spinal cord. Purinergic Signal 2009; 5:223-32. [PMID: 19205927 DOI: 10.1007/s11302-009-9138-2] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2008] [Accepted: 07/15/2008] [Indexed: 12/24/2022] Open
Abstract
ATP-mediated signaling has widespread actions in the nervous system from neurotransmission to regulation of proliferation. In addition, ATP is released during injury and associated to immune and inflammatory responses. Still, the potential of therapeutic intervention of purinergic signaling during pathological states is only now beginning to be explored because of the large number of purinergic receptors subtypes involved, the complex and often overlapping pharmacology and because ATP has effects on every major cell type present in the CNS. In this review, we will focus on a subclass of purinergic-ligand-gated ion channels, the P2X7 receptor, its pattern of expression and its function in the spinal cord where it is abundantly expressed. We will discuss the mechanisms for P2X7R actions and the potential that manipulating the P2X7R signaling pathway may have for therapeutic intervention in pathological events, specifically in the spinal cord.
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Affiliation(s)
- Maria Luisa Cotrina
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, University of Rochester Medical Center, 601 Elmwood Avenue, Rochester, NY, 14642, USA,
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254
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Tanaka Y, Tozuka Y, Takata T, Shimazu N, Matsumura N, Ohta A, Hisatsune T. Excitatory GABAergic activation of cortical dividing glial cells. ACTA ACUST UNITED AC 2009; 19:2181-95. [PMID: 19131437 DOI: 10.1093/cercor/bhn238] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Adult neocortex contains dividing satellite glia population even though their characteristics and functions have still remained unknown. Nestin(+)/NG2(+) cells as major fraction of dividing glial cells express bicuculline-sensitive gamma-aminobutyric acid A (GABA(A)) receptors and receive GABAergic inputs. Due to their high [Cl(-)](i), GABAergic activation depolarized the cells and then induced Ca(2+) influx into them. To assess an effect of this GABAergic excitation, we looked for the expression of neurotrophic factors. Among them, we detected the expression of brain-derived neurotrophic factor (BDNF) on the cells. The level of BDNF expression was elevated after cortical ischemia, and this elevation was blocked by bumetanide, an inhibitor for NKCC1 that blocks the GABAergic depolarization. Furthermore, performing a modified adhesive removal test, we observed that the treatment of bumetanide significantly attenuated the recovery in somatosensory dysfunction. Our results may shed a light on satellite glia population in the cortex and imply their roles in the functional recovery after ischemic injuries.
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Affiliation(s)
- Yuichi Tanaka
- Department of Integrated Biosciences, University of Tokyo, Kashiwa, Chiba 277-8562, Japan
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255
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De Proost I, Pintelon I, Wilkinson WJ, Goethals S, Brouns I, Van Nassauw L, Riccardi D, Timmermans JP, Kemp PJ, Adriaensen D. Purinergic signaling in the pulmonary neuroepithelial body microenvironment unraveled by live cell imaging. FASEB J 2008; 23:1153-60. [PMID: 19050048 DOI: 10.1096/fj.08-109579] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Pulmonary neuroepithelial bodies (NEBs) are densely innervated groups of complex sensory airway receptors involved in the regulation of breathing. Together with their surrounding Clara-like cells, they exhibit stem cell potential through their capacity to regenerate depopulated areas of the epithelium following lung injury. We have employed confocal live cell imaging microscopy and novel electrophysiological techniques in a new ex vivo lung slice model to unravel potential purinergic signaling pathways within the NEB microenvironment. Quinacrine histochemistry indicated high amounts of vesicular ATP in NEB cells. Using a "reporter-patching" method adapted to create a uniquely sensitive and selective biosensor for the direct detection of ATP release from NEBs ex vivo, we demonstrated quantal ATP release from NEBs following their depolarization. Enhancing enzymatic extracellular ATP hydrolysis or inhibiting P2 receptors confirmed the central role of ATP in paracrine interactions between NEB cells and Clara-like cells. Combined calcium imaging, pharmacology, and immunohistochemistry showed that ligand-binding to functional P2Y(2) receptors underpins the activation of Clara-like cells. Hence, NEB cells communicate with their cellular neighbors in the NEB microenvironment by releasing ATP, which rapidly evokes purinergic activation of surrounding Clara-like cells. Besides ATP acting on the P2X(3) receptor expressing vagal sensory nerve terminals between NEB cells, local paracrine purinergic signaling within this potential stem cell niche may be important to both normal airway function, airway epithelial regeneration after injury, and/or the pathogenesis of small cell lung carcinomas.
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Affiliation(s)
- Ian De Proost
- Department of Veterinary Sciences, University of Antwerp, Antwerp, Belgium
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256
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Li M, Kim TJ, Kwon HJ, Suh JW. Effects of extracellular ATP on the physiology of Streptomyces coelicolor A3(2). FEMS Microbiol Lett 2008; 286:24-31. [PMID: 18565122 DOI: 10.1111/j.1574-6968.2008.01248.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Because ATP is an extracellular effector in animal and plant systems and derivatives of ATP, such as S-adenosylmethionine and cAMP, can control antibiotic production and morphological differentiation in Streptomyces, we hypothesized that extracellular ATP (exATP) can also affect physiologies of Streptomyces. We found that the addition of 10 microM exATP to Streptomyces coelicolor A3(2) cultures resulted in enhanced actinorhodin and undecylprodigiosin production and morphological differentiation on solid medium. However, these phenotypes were reduced by the addition of a 10-fold higher concentration of exATP (100 microM). Intracellular ATP concentrations were also modulated in response to changes in exATP. ATP analogs, added at a 100-fold lower concentration, affected Streptomyces similarly to that seen for 10 microM exATP. The enhanced promoter activity of actII-orf4 indicated that 10 microM exATP affect the transcriptional level for actinorhodin production. Results from this study suggest that exATP is an effector for the physiology of S. coelicolor and careful manipulation of exATP may significantly enhance the high-yield production of antibiotics by S. coelicolor.
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Affiliation(s)
- Ming Li
- Division of Bioscience and Bioinformatics, College of Natural Science, Myongji University, Yongin, Gyeonggi-Do, Korea
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257
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Activation of P2X7 receptors in glial satellite cells reduces pain through downregulation of P2X3 receptors in nociceptive neurons. Proc Natl Acad Sci U S A 2008; 105:16773-8. [PMID: 18946042 DOI: 10.1073/pnas.0801793105] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Purinergic ionotropic P2X7 receptors (P2X7Rs) are closely associated with excitotoxicity and nociception. Inhibition of P2X7R activation has been considered as a potentially useful strategy to improve recovery from spinal cord injury and reduce inflammatory damage to trauma. The physiological functions of P2X7Rs, however, are poorly understood, even though such information is essential for making the P2X7R an effective therapeutic target. We show here that P2X7Rs in satellite cells of dorsal root ganglia tonically inhibit the expression of P2X3Rs in neurons. Reducing P2X7R expression using siRNA or blocking P2X7R activity by antagonists elicits P2X3R up-regulation, increases the activity of sensory neurons responding to painful stimuli, and evokes abnormal nociceptive behaviors in rats. Thus, contrary to the notion that P2X7R activation is cytotoxic, P2X7Rs in satellite cells play a crucial role in maintaining proper P2X3R expression in dorsal root ganglia. Studying the mechanism underlying the P2X7R-P2X3R control, we demonstrate that activation of P2X7Rs evokes ATP release from satellite cells. ATP in turn stimulates P2Y1 receptors in neurons. P2Y1 receptor activation appears to be necessary and sufficient for the inhibitory control of P2X3R expression. We further determine the roles of the P2X7R-P2Y1-P2X3R inhibitory control under injurious conditions. Activation of the inhibitory control effectively prevents the development of allodynia and increases the potency of systemically administered P2X7R agonists in inflamed rats. Thus, direct blocking P2X7Rs, as proposed before, may not be the best strategy for reducing pain or lessening neuronal degeneration because it also disrupts the protective function of P2X7Rs.
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258
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Contribution of activated interleukin receptors in trigeminal ganglion neurons to hyperalgesia via satellite glial interleukin-1beta paracrine mechanism. Brain Behav Immun 2008; 22:1016-1023. [PMID: 18440198 DOI: 10.1016/j.bbi.2008.03.004] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2008] [Revised: 03/17/2008] [Accepted: 03/19/2008] [Indexed: 11/19/2022] Open
Abstract
The present study investigated whether under in vivo conditions, inflammation alters the excitability of nociceptive Adelta-trigeminal ganglion (TRG) neurons innervating the facial skin via a cytokine paracrine mechanism. We used extracellular electrophysiological recording with multibarrel-electrodes in this study, and complete Freund's adjuvant (CFA) was injected into the rat facial skin. The threshold for escape from mechanical stimulation applied to the whisker pad area in inflamed rats (2 days after CFA injection) was significantly lower than that in control rats. A total of 45 Adelta-nociceptive-TRG neurons responding to electrical stimulation of the whisker pad were recorded in pentobarbital-anesthetized rats. The number of Adelta-TRG neurons with spontaneous firings and their firing rate in inflamed rats were significantly larger than those in control rats. The firing rates of the Adelta-TRG neuronal spontaneous activity were current-dependently decreased by local iontophoretic application of an interleukin I receptor type I antagonist (IL-1ra) in inflamed rats, but not in controls, and current-dependently increased by iontophoretic application of interleukin 1beta (IL-1beta) in both control and inflamed rats. IL-1ra also inhibited Adelta-TRG neuron activity evoked by mechanical stimulation in the inflamed rats. The mechanical threshold of nociceptive-TRG neurons in inflamed rats was significantly lower than that in control rats, but was not significantly different between control and inflamed rats after application of an IL-1ra. These results suggested that inflammation modulates the excitability of nociceptive Adelta-TRG neurons innervating the facial skin via IL-1beta paracrine action within trigeminal ganglia. Such an IL-1beta release could be important in determining trigeminal inflammatory hyperalgesia.
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259
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cGMP produced by NO-sensitive guanylyl cyclase essentially contributes to inflammatory and neuropathic pain by using targets different from cGMP-dependent protein kinase I. J Neurosci 2008; 28:8568-76. [PMID: 18716216 DOI: 10.1523/jneurosci.2128-08.2008] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
A large body of evidence indicates that the release of nitric oxide (NO) is crucial for the central sensitization of pain pathways during both inflammatory and neuropathic pain. Here, we investigated the distribution of NO-sensitive guanylyl cyclase (NO-GC) in the spinal cord and in dorsal root ganglia, and we characterized the nociceptive behavior of mice deficient in NO-GC (GC-KO mice). We show that NO-GC is distinctly expressed in neurons of the mouse dorsal horn, whereas its distribution in dorsal root ganglia is restricted to non-neuronal cells. GC-KO mice exhibited a considerably reduced nociceptive behavior in models of inflammatory or neuropathic pain, but their responses to acute pain were not impaired. Moreover, GC-KO mice failed to develop pain sensitization induced by intrathecal administration of drugs releasing NO or carbon monoxide. Surprisingly, during spinal nociceptive processing, cGMP produced by NO-GC may activate signaling pathways different from cGMP-dependent protein kinase I (cGKI), whereas cGKI can be activated by natriuretic peptide receptor-B dependent cGMP production. Together, our results provide evidence that NO-GC is crucially involved in the central sensitization of pain pathways during inflammatory and neuropathic pain.
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260
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Zeng Y, Lv XH, Zeng SQ, Tian SL, Li M, Shi J. Sustained depolarization-induced propagation of [Ca2+]i oscillations in cultured DRG neurons: the involvement of extracellular ATP and P2Y receptor activation. Brain Res 2008; 1239:12-23. [PMID: 18804455 DOI: 10.1016/j.brainres.2008.08.085] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2008] [Revised: 07/24/2008] [Accepted: 08/24/2008] [Indexed: 12/26/2022]
Abstract
Recently emerging evidence implicates a number of neuroactive substances and their receptors in mediating complex cell-to-cell communications in the ganglia. In the present study, we characterized the nonsynaptic chemical coupling mediated by extracellular ATP in dorsal root ganglia (DRG) neuron cultures by using the real time imaging of ATP, whole-cell patch clamping, in conjunction with confocal calcium imaging. Sustained depolarization by electrical stimulation evoked intracellular Ca2+ concentrations ([Ca2+]i) oscillations in individual DRG neurons, and subsequent ATP-dependent propagation [Ca2+]i oscillations to surrounding non-stimulated neighbors. [Ca2+]i oscillations were suppressed by inositol-1,4,5-trisphosphate (IP3) receptor antagonist 2-APB, but not ryanodine. The propagation of [Ca2+]i oscillations was prevented by the presence of the ATP-degrading enzyme, apyrase, and completely abolished by the blockase of G protein-coupled purinergic receptors-PLC-IP3 pathway with suramin, U73122 or 2-APB. In parallel, sustained depolarization elicited robust ATP release and diffusion from the stimulation site. Moreover, exogenous application of ATP to DRG cultures in large concentration elicits the [Ca2+]i oscillations in most neurons. Taken together, this data demonstrates that sustained membrane depolarization elicited ATP release, acting through a highly sensitive P2Y receptors/IP3-mediated signaling pathway to mediate the propagation of intercellular Ca2+ signaling, which suggest a novel signaling pathway for neuronal communication in DRG.
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Affiliation(s)
- Yan Zeng
- Department of Neurobiology, Tongji Medical School, Huazhong University of Science and Technology, HUST, 13 Hangkong Road, Wuhan 430030, PR China
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261
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Gao Y, Xu C, Liang S, Zhang A, Mu S, Wang Y, Wan F. Effect of tetramethylpyrazine on primary afferent transmission mediated by P2X3 receptor in neuropathic pain states. Brain Res Bull 2008; 77:27-32. [DOI: 10.1016/j.brainresbull.2008.02.026] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2008] [Accepted: 02/18/2008] [Indexed: 01/26/2023]
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262
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Xiang Z, Xiong Y, Yan N, Li X, Mao Y, Ni X, He C, LaMotte RH, Burnstock G, Sun J. Functional up-regulation of P2X 3 receptors in the chronically compressed dorsal root ganglion. Pain 2008; 140:23-34. [PMID: 18715715 DOI: 10.1016/j.pain.2008.07.006] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2008] [Revised: 06/03/2008] [Accepted: 07/07/2008] [Indexed: 12/20/2022]
Abstract
P2X receptors on dorsal root ganglion (DRG) neurons have been strongly implicated in pathological nociception after peripheral nerve injuries or inflammation. However, nothing is known of a role for purinergic receptors in neuropathic pain produced by a chronic compression of DRG (CCD) - an injury that may accompany an intraforaminal stenosis, a laterally herniated disc or other disorders of the spine leading to radicular pain. In a rat model of DRG compression, hyperexcitable neurons retain functioning axonal connections with their peripheral targets. It is unknown whether such hyperexcitability might enhance chemically mediated nociceptive stimulation of the skin. In this study, CCD facilitated the nocifensive behavior and mechanical hyperalgesia-induced by the P2X 3 agonist, alpha,beta-methylene ATP (alpha,beta-meATP). An injection of alpha,beta-meATP into the hind paw of CCD rats resulted in a significantly greater decrease in the mean threshold to von Frey stimuli and a greater duration of paw lifts than in sham-operated control rats. CCD also increased the levels of P2X 3 receptor protein and the number of P2X 3 immunoreactive, small diameter DRG neurons in the compressed ganglion. P2X 3 receptors were co-labeled with the isolectin IB4, consistent with a role in nociception. In addition, a alpha,beta-meATP induced significantly larger fast-inactivating currents in CCD- than in sham-operated acutely dissociated DRG neurons. These currents were accompanied by the generation of action potentials - but only in the CCD neurons. U0126, a specific inhibitor of the MEK1/2, greatly down-regulated the enhanced current. Taken together, these observations suggest that enhanced purinergic responses after CCD are mediated by P2X 3 receptors.
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Affiliation(s)
- Zhenghua Xiang
- Department of Physiology, Second Military Medical University, 800 Xiangyin Road, Shanghai 200433, PR China Department of Neurobiology, Second Military Medical University, Shanghai 200433, PR China Department of Anesthesiology, Changhai Hospital, Second Military Medical University, Shanghai 200433, PR China Key Laboratory of Molecular Neurobiology, Ministry of Education, Second Military Medical University, Shanghai 200433, PR China Department of Anesthesiology, Yale University School of Medicine, New Haven, CT 06510, USA Autonomic Neuroscience Centre, Royal Free and University College Medical School, Rowland Hill Street, London NW3 2PF, UK
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263
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Naik A, Pathirathna S, Jevtovic-Todorovic V. GABAA receptor modulation in dorsal root ganglia in vivo affects chronic pain after nerve injury. Neuroscience 2008; 154:1539-53. [DOI: 10.1016/j.neuroscience.2008.04.061] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2008] [Revised: 04/18/2008] [Accepted: 04/22/2008] [Indexed: 11/28/2022]
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264
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Xiao C, Zhou C, Li K, Davies DL, Ye JH. Purinergic type 2 receptors at GABAergic synapses on ventral tegmental area dopamine neurons are targets for ethanol action. J Pharmacol Exp Ther 2008; 327:196-205. [PMID: 18583548 DOI: 10.1124/jpet.108.139766] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The current study investigated whether ethanol alters ATP activation of purinergic type 2 receptors (P2Rs) in the ventral tegmental area (VTA). The VTA is a key region of the brain that has been implicated in the development of alcohol addiction. We investigated the effects of ATP and ethanol on spontaneous inhibitory postsynaptic currents (sIPSCs) and the spontaneous firings in the VTA dopaminergic neurons, obtained using an enzyme-free procedure. These neurons preserved some functional GABA-releasing terminals after isolation. We found that ATP (1-200 microM) either increased or decreased the frequency of sIPSCs and the activity of VTA dopaminergic neurons. The effects of ATP on sIPSC frequency inversely correlated with its effects on dopaminergic neuron activity. The ATP-induced changes in sIPSC frequency were blocked by tetrodotoxin (a sodium channel blocker) and by suramin (a nonselective P2R antagonist). Furthermore, alpha,beta-methylene ATP, a selective P2X(1) and P2X(3) receptor agonist, increased sIPSC frequency, whereas adenosine 5'-[beta-thio]diphosphate, a preferential agonist of P2Y receptors, decreased sIPSC frequency. In experiments testing the effects of ethanol (10 and 40 mM) on sIPSCs, we found that ethanol significantly attenuated ATP-induced increase and enhanced ATP-induced decrease in sIPSC frequency. Taken together, the results demonstrate that multiple subtypes of P2Rs exist on GABA-releasing terminals that make synapses on VTA dopaminergic neurons. It seems that ATP increases sIPSC frequency involving P2X(1) and/or P2X(3) receptors, and ATP decreases sIPSC frequency involving P2YRs. These findings are also consistent with the notion that P2Rs at GABA-releasing terminals on VTA dopaminergic neurons are important targets for ethanol action.
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Affiliation(s)
- Cheng Xiao
- Department of Anesthesiology, Pharmacology and Physiology, New Jersey Medical School (UMDNJ), 185 South Orange Avenue, Newark, NJ 07103-2714, USA
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265
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Xiao Y, Richter JA, Hurley JH. Release of glutamate and CGRP from trigeminal ganglion neurons: Role of calcium channels and 5-HT1 receptor signaling. Mol Pain 2008; 4:12. [PMID: 18416824 PMCID: PMC2359740 DOI: 10.1186/1744-8069-4-12] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2007] [Accepted: 04/16/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The aberrant release of the neurotransmitters, glutamate and calcitonin-gene related peptide (CGRP), from trigeminal neurons has been implicated in migraine. The voltage-gated P/Q-type calcium channel has a critical role in controlling neurotransmitter release and has been linked to Familial Hemiplegic Migraine. Therefore, we examined the importance of voltage-dependent calcium channels in controlling release of glutamate and CGRP from trigeminal ganglion neurons isolated from male and female rats and grown in culture. Serotonergic pathways are likely involved in migraine, as triptans, a class of 5-HT1 receptor agonists, are effective in the treatment of migraine and their effectiveness may be due to inhibiting neurotransmitter release from trigeminal neurons. We also studied the effect of serotonin receptor activation on release of glutamate and CGRP from trigeminal neurons grown in culture. RESULTS P/Q-, N- and L-type channels each mediate a significant fraction of potassium-stimulated release of glutamate and CGRP. We determined that 5-HT significantly inhibits potassium-stimulated release of both glutamate and CGRP. Serotonergic inhibition of both CGRP and glutamate release can be blocked by pertussis toxin and NAS-181, a 5-HT1B/1D antagonist. Stimulated release of CGRP is unaffected by Y-25130, a 5-HT3 antagonist and SB 200646, a 5-HT2B/2C antagonist. CONCLUSION These data suggest that release of both glutamate and CGRP from trigeminal neurons is controlled by calcium channels and modulated by 5-HT signaling in a pertussis-toxin dependent manner and probably via 5-HT1 receptor signaling. This is the first characterization of glutamate release from trigeminal neurons grown in culture.
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Affiliation(s)
- Yan Xiao
- Department of Biochemistry and Molecular Biology, Stark Neurosciences Research Institute, Indiana University School of Medicine, 950 West Walnut Street, Indianapolis, Indiana, 46202, USA.
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266
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Inhibition of P2X7 receptors by divalent cations: old action and new insight. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2008; 38:339-46. [DOI: 10.1007/s00249-008-0315-y] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2007] [Revised: 03/11/2008] [Accepted: 03/13/2008] [Indexed: 10/22/2022]
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267
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Wu LJ, Zhuo M. Resting microglial motility is independent of synaptic plasticity in mammalian brain. J Neurophysiol 2008; 99:2026-32. [PMID: 18256162 DOI: 10.1152/jn.01210.2007] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Microglia are well known for their roles in brain injuries and infections. However, there is no function attributes to resting microglia thus far. Here we performed a combination of simultaneous electrophysiology and time-lapse confocal imaging in green fluorescent protein-labeled microglia in acute hippocampal slices. In contrast to CA1 neurons, microglia showed no spontaneous or evoked synaptic currents. Neither glutamate- nor GABA-induced current/chemotaxis of microglia was detected. Strong tetanic stimulation of Schaffer-collateral pathways that induce CA1 long-term potentiation did not affect microglial motilities. Our results suggest that microglia are highly reserved for neuronal protective function but not synaptic plasticity in the brain.
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Affiliation(s)
- Long-Jun Wu
- Department of Physiology, University of Toronto Centre for the Study of Pain, Toronto, Ontario, Canada
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268
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Scholz J, Woolf CJ. The neuropathic pain triad: neurons, immune cells and glia. Nat Neurosci 2008; 10:1361-8. [PMID: 17965656 DOI: 10.1038/nn1992] [Citation(s) in RCA: 1289] [Impact Index Per Article: 80.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Nociceptive pain results from the detection of intense or noxious stimuli by specialized high-threshold sensory neurons (nociceptors), a transfer of action potentials to the spinal cord, and onward transmission of the warning signal to the brain. In contrast, clinical pain such as pain after nerve injury (neuropathic pain) is characterized by pain in the absence of a stimulus and reduced nociceptive thresholds so that normally innocuous stimuli produce pain. The development of neuropathic pain involves not only neuronal pathways, but also Schwann cells, satellite cells in the dorsal root ganglia, components of the peripheral immune system, spinal microglia and astrocytes. As we increasingly appreciate that neuropathic pain has many features of a neuroimmune disorder, immunosuppression and blockade of the reciprocal signaling pathways between neuronal and non-neuronal cells offer new opportunities for disease modification and more successful management of pain.
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Affiliation(s)
- Joachim Scholz
- Neural Plasticity Research Group, Department of Anesthesia and Critical Care, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129, USA.
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269
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Nishikawa S. Styryl Pyridinium Dyes FM1-43 and AM1-43 for Visualization of Sensory Nerve Fibers and Cells in Dental and Craniofacial Tissues of Small Experimental Animals. J Oral Biosci 2008. [DOI: 10.1016/s1349-0079(08)80026-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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270
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Conejero-Goldberg C, Davies P, Ulloa L. Alpha7 nicotinic acetylcholine receptor: a link between inflammation and neurodegeneration. Neurosci Biobehav Rev 2007; 32:693-706. [PMID: 18180036 DOI: 10.1016/j.neubiorev.2007.10.007] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2007] [Revised: 10/23/2007] [Accepted: 10/26/2007] [Indexed: 11/28/2022]
Abstract
Alzheimer's disease (AD) is the leading cause of dementia affecting over 25 million people worldwide. Classical studies focused on the description and characterization of the pathological hallmarks found in AD patients including the neurofibrillary tangles and the amyloid plaques. Current strategies focus on the etiology of these hallmarks and the different mechanisms contributing to neurodegeneration. Among them, recent studies reveal the close interplay between the immunological and the neurodegenerative processes. This article examines the implications of the alpha7 nicotinic acetylcholine receptor (alpha7nAChR) as a critical link between inflammation and neurodegeneration in AD. Alpha7nAChRs are not only expressed in neurons but also in Glia cells where they can modulate the immunological responses contributing to AD. Successful therapeutic strategies against AD should consider the connections between inflammation and neurodegeneration. Among them, alpha7nAChR may represent a pharmacological target to control these two mechanisms during the pathogenesis of neurodegenerative and behavioral disorders.
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Affiliation(s)
- Concepcion Conejero-Goldberg
- The Litwin-Zucker Research Center for the Study of Alzheimer's Disease, The Feinstein Institute for Medical Research, 350 Community Drive, Manhasset, NY 11030, USA.
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271
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Sperlágh B, Heinrich A, Csölle C. P2 receptor-mediated modulation of neurotransmitter release-an update. Purinergic Signal 2007; 3:269-84. [PMID: 18404441 PMCID: PMC2072919 DOI: 10.1007/s11302-007-9080-0] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2007] [Accepted: 08/28/2007] [Indexed: 11/26/2022] Open
Abstract
Presynaptic nerve terminals are equipped with a number of presynaptic auto- and heteroreceptors, including ionotropic P2X and metabotropic P2Y receptors. P2 receptors serve as modulation sites of transmitter release by ATP and other nucleotides released by neuronal activity and pathological signals. A wide variety of P2X and P2Y receptors expressed at pre- and postsynaptic sites as well as in glial cells are involved directly or indirectly in the modulation of neurotransmitter release. Nucleotides are released from synaptic and nonsynaptic sites throughout the nervous system and might reach concentrations high enough to activate these receptors. By providing a fine-tuning mechanism these receptors also offer attractive sites for pharmacotherapy in nervous system diseases. Here we review the rapidly emerging data on the modulation of transmitter release by facilitatory and inhibitory P2 receptors and the receptor subtypes involved in these interactions.
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Affiliation(s)
- Beáta Sperlágh
- Laboratory of Molecular Pharmacology, Institute of Experimental Medicine, Hungarian Academy of Sciences, POB 67, Budapest, 1450, Hungary,
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272
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Inoue K, Tsuda M, Tozaki-Saitoh H. Modification of neuropathic pain sensation through microglial ATP receptors. Purinergic Signal 2007; 3:311-6. [PMID: 18404444 PMCID: PMC2072920 DOI: 10.1007/s11302-007-9071-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2007] [Accepted: 08/02/2007] [Indexed: 03/21/2023] Open
Abstract
Neuropathic pain that typically develops when peripheral nerves are damaged through surgery, bone compression in cancer, diabetes, or infection is a major factor causing impaired quality of life in millions of people worldwide. Recently, there has been a rapidly growing body of evidence indicating that spinal glia play a critical role in the pathogenesis of neuropathic pain. Accumulating findings also indicate that nucleotides play an important role in neuron-glia communication through P2 purinoceptors. Damaged neurons release or leak nucleotides including ATP and UTP to stimulate microglia through P2 purinoceptors expressing on microglia. It was shown in an animal model of neuropathic pain that microglial P2X4 and P2X7 receptors are crucial in pain signaling after peripheral nerve lesion. In this review, we describe the modification of neuropathic pain sensation through microglial P2X4 and P2X7, with the possibility of P2Y6 and P2Y12 involvement.
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Affiliation(s)
- Kazuhide Inoue
- Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi, Fukuoka, 812-8582, Japan,
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