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Haberberger RV, Kuramatilake J, Barry CM, Matusica D. Ultrastructure of dorsal root ganglia. Cell Tissue Res 2023:10.1007/s00441-023-03770-w. [PMID: 37079097 PMCID: PMC10115609 DOI: 10.1007/s00441-023-03770-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Accepted: 03/28/2023] [Indexed: 04/21/2023]
Abstract
Dorsal root ganglia (DRG) contains thousands of sensory neurons that transmit information about our external and internal environment to the central nervous system. This includes signals related to proprioception, temperature, and nociception. Our understanding of DRG has increased tremendously over the last 50 years and has established the DRG as an active participant in peripheral processes. This includes interactions between neurons and non-neuronal cells such as satellite glia cells and macrophages that contribute to an increasingly complex cellular environment that modulates neuronal function. Early ultrastructural investigations of the DRG have described subtypes of sensory neurons based on differences in the arrangement of organelles such as the Golgi apparatus and the endoplasmic reticulum. The neuron-satellite cell complex and the composition of the axon hillock in DRG have also been investigated, but, apart from basic descriptions of Schwann cells, ultrastructural investigations of other cell types in DRG are limited. Furthermore, detailed descriptions of key components of DRG, such as blood vessels and the capsule that sits at the intersection of the meninges and the connective tissue covering the peripheral nervous system, are lacking to date. With rising interest in DRG as potential therapeutic targets for aberrant signalling associated with chronic pain conditions, gaining further insights into DRG ultrastructure will be fundamental to understanding cell-cell interactions that modulate DRG function. In this review, we aim to provide a synopsis of the current state of knowledge on the ultrastructure of the DRG and its components, as well as to identify areas of interest for future studies.
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Affiliation(s)
- Rainer Viktor Haberberger
- Division of Anatomy and Pathology, School of Biomedicine, The University of Adelaide, Adelaide, Australia.
| | - Jaliya Kuramatilake
- Division of Anatomy and Pathology, School of Biomedicine, The University of Adelaide, Adelaide, Australia
| | - Christine M Barry
- Anatomy, Histology & Pathology, College of Medicine and Public Health, Flinders University, Adelaide, Australia
| | - Dusan Matusica
- Anatomy, Histology & Pathology, College of Medicine and Public Health, Flinders University, Adelaide, Australia
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Li H, Shang M, Liu L, Lin X, Hu J, Han Q, Xing J. Protein kinase G signaling pathway is involved in sympathetically maintained pain by modulating ATP-sensitive potassium channels. Reg Anesth Pain Med 2021; 46:1006-1011. [PMID: 34493624 DOI: 10.1136/rapm-2021-102539] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Accepted: 08/18/2021] [Indexed: 12/25/2022]
Abstract
BACKGROUND Sympathetically maintained pain (SMP) involves an increased excitability of dorsal root ganglion (DRG) neurons to sympathetic nerve stimulation and circulating norepinephrine. The current treatment of SMP has limited efficacy, and hence more mechanistic insights into this intractable pain condition are urgently needed. METHODS A caudal trunk transection (CTT) model of neuropathic pain was established in mice.Immunofluorescence staining, small interfering RNA, pharmacological and electrophysiological studies were conducted to test the hypothesis that norepinephrine increases the excitability of small-diameter DRG neurons from CTT mice through the activation of cyclic guanosine monophosphate-protein kinase G (cGMP-PKG) signaling pathway. RESULTS Behavior study showed that CTT mice developed mechanical and heat hypersensitivities, which were attenuated by intraperitoneal injection of guanethidine. CTT mice also showed an abnormal sprouting of tyrosine hydroxylase-positive nerve fibers in DRG, and an increased excitability of small-diameter DRG neurons to norepinephrine, suggesting that CTT is a useful model to study SMP. Importantly, inhibiting cGMP-PKG pathway with small interfering RNA and KT5823 attenuated the increased sympathetic sensitivity in CTT mice. In contrast, cGMP activators (Sp-cGMP, 8-Br-cGMP) further increased sympathetic sensitivity. Furthermore, phosphorylation of ATP-sensitive potassium channel, which is a downstream target of PKG, may contribute to the adrenergic modulation of DRG neuron excitability. CONCLUSIONS Our findings suggest an important role of cGMP-PKG signaling pathway in the increased excitability of small-diameter DRG neurons to norepinephrine after CTT, which involves an inhibition of the ATP-sensitive potassium currents through PKG-induced phosphorylation. Accordingly, drugs targeting this pathway may help to treat SMP.
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Affiliation(s)
- Huiming Li
- Department of Anesthesiology and Perioperative Medicine, Fourth Military Medical University, Xi'an, China
| | - Mengjuan Shang
- Department of Radiation Biology, Fourth Military Medical University, Xi'an, China
| | - Ling Liu
- Department of Neurobiology, Fourth Military Medical University, Xi'an, China
| | - Xiaoyu Lin
- Department of Urology, General Hospital of Southern Theater Command, Guangzhou, China
| | - Junfeng Hu
- Department of Radiation Biology, Fourth Military Medical University, Xi'an, China
| | - Qian Han
- Department of Radiation Biology, Fourth Military Medical University, Xi'an, China
| | - Junling Xing
- Department of Radiation Biology, Fourth Military Medical University, Xi'an, China .,Ministry of Education Key Lab of Hazard Assessment and Control in Special Operational Environment, Fourth Military Medical University, Xi'an, China
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Sympathectomy and Sympathetic Blockade Reduce Pain Behavior Via Alpha-2 Adrenoceptor of the Dorsal Root Ganglion Neurons in a Lumbar Radiculopathy Model. Spine (Phila Pa 1976) 2015; 40:E1269-75. [PMID: 26165214 DOI: 10.1097/brs.0000000000001050] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN Animal experimental study with intervention. OBJECTIVE We investigated whether sympathectomy and pharmacological sympathetic blockade reduced pain behavior and reversed adrenoceptor mRNA expression of the dorsal root ganglion (DRG) in a lumbar radiculopathy model. SUMMARY OF BACKGROUND DATA The abnormal sympathetic-somatosensory interaction may underlie some forms of neuropathic pain. There are several reports that sympathectomy and pharmacological sympathetic blockades are often effective to treat neuropathic pain. However, its pathophysiological mechanisms remain obscure. METHODS We used 91 male Sprague-Dawley rats. Just after root constriction (RC), the rats underwent sympathectomy or received 3 local injections of subtype-specific α-adrenergic receptor antagonists around the DRG. We evaluated the analgesic effects of sympathectomy and sympathetic blockade using behaviors indicative mechanical allodynia and thermal hyperalgesia. We estimated the mRNA expression levels of the DRG adrenoceptor subtypes using real time reverse transcription polymerase chain reaction. RESULTS Sympathectomy and α2-antagonist significantly reduced the mechanical allodynia and thermal hyperalgesia after RC. Real time reverse transcription polymerase chain reaction analysis indicated that sympathectomy possibly reversed α2A- and α2B-adrenoceptors mRNA overexpression in the DRG after RC. CONCLUSION We considered that pain behaviors of neuropathic pain are due, at least in part, to enhanced sympathetic noradrenergic transmission within the DRG. Suppression of sympathetic activity by reducing adrenergic release, α2-adrenoceptor stimulation, and/or α2-adrenoceptor upregulation in the DRG may relieve neuropathic pain. LEVEL OF EVIDENCE 3.
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Ogon I, Takebayashi T, Miyakawa T, Iwase T, Tanimoto K, Terashima Y, Jimbo S, Kobayashi T, Tohse N, Yamashita T. Attenuation of pain behaviour by local administration of alpha-2 adrenoceptor antagonists to dorsal root ganglia in a rat radiculopathy model. Eur J Pain 2015; 20:790-9. [DOI: 10.1002/ejp.804] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/30/2015] [Indexed: 11/10/2022]
Affiliation(s)
- I. Ogon
- Department of Orthopaedic Surgery; Sapporo Medical University School of Medicine; Japan
| | - T. Takebayashi
- Department of Orthopaedic Surgery; Sapporo Medical University School of Medicine; Japan
| | - T. Miyakawa
- Department of Orthopaedic Surgery; Sapporo Medical University School of Medicine; Japan
| | - T. Iwase
- Department of Orthopaedic Surgery; Sapporo Medical University School of Medicine; Japan
| | - K. Tanimoto
- Department of Orthopaedic Surgery; Sapporo Medical University School of Medicine; Japan
| | - Y. Terashima
- Department of Orthopaedic Surgery; Sapporo Medical University School of Medicine; Japan
| | - S. Jimbo
- Department of Orthopaedic Surgery; Sapporo Medical University School of Medicine; Japan
| | - T. Kobayashi
- Department of Cellular Physiology and Signal Transduction; Sapporo Medical University School of Medicine; Japan
| | - N. Tohse
- Department of Cellular Physiology and Signal Transduction; Sapporo Medical University School of Medicine; Japan
| | - T. Yamashita
- Department of Orthopaedic Surgery; Sapporo Medical University School of Medicine; Japan
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Iwase T, Takebayashi T, Tanimoto K, Terashima Y, Miyakawa T, Kobayashi T, Tohse N, Yamashita T. Sympathectomy attenuates excitability of dorsal root ganglion neurons and pain behaviour in a lumbar radiculopathy model. Bone Joint Res 2012; 1:198-204. [PMID: 23610691 PMCID: PMC3626214 DOI: 10.1302/2046-3758.19.2000073] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Accepted: 07/03/2012] [Indexed: 01/19/2023] Open
Abstract
Objectives In order to elucidate the influence of sympathetic nerves on
lumbar radiculopathy, we investigated whether sympathectomy attenuated
pain behaviour and altered the electrical properties of the dorsal
root ganglion (DRG) neurons in a rat model of lumbar root constriction. Methods Sprague-Dawley rats were divided into three experimental groups.
In the root constriction group, the left L5 spinal nerve root was
ligated proximal to the DRG as a lumbar radiculopathy model. In
the root constriction + sympathectomy group, sympathectomy was performed
after the root constriction procedure. In the control group, no
procedures were performed. In order to evaluate the pain relief
effect of sympathectomy, behavioural analysis using mechanical and
thermal stimulation was performed. In order to evaluate the excitability
of the DRG neurons, we recorded action potentials of the isolated
single DRG neuron by the whole-cell patch-clamp method. Results In behavioural analysis, sympathectomy attenuated the mechanical
allodynia and thermal hyperalgesia caused by lumbar root constriction.
In electrophysiological analysis, single isolated DRG neurons with
root constriction exhibited lower threshold current, more depolarised
resting membrane potential, prolonged action potential duration,
and more depolarisation frequency. These hyperexcitable alterations
caused by root constriction were significantly attenuated in rats
treated with surgical sympathectomy. Conclusion The present results suggest that sympathectomy attenuates lumbar
radicular pain resulting from root constriction by altering the
electrical property of the DRG neuron itself. Thus, the sympathetic
nervous system was closely associated with lumbar radicular pain,
and suppressing the activity of the sympathetic nervous system may therefore
lead to pain relief.
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Affiliation(s)
- T Iwase
- Sapporo Medical University School of Medicine, Department of Orthopaedic Surgery, South 1, West 16, Chuo-ku, Sapporo 060-8543, Japan
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Kanno T, Nishizaki T. CFTR mediates noradrenaline-induced ATP efflux from DRG neurons. Mol Pain 2011; 7:72. [PMID: 21943397 PMCID: PMC3192679 DOI: 10.1186/1744-8069-7-72] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Accepted: 09/24/2011] [Indexed: 11/15/2022] Open
Abstract
In our earlier study, noradrenaline (NA) stimulated ATP release from dorsal root ganglion (DRG) neurons as mediated via β3 adrenoceptors linked to Gs protein involving protein kinase A (PKA) activation, to cause allodynia. The present study was conducted to understand how ATP is released from DRG neurons. In an outside-out patch-clamp configuration from acutely dissociated rat DRG neurons, single-channel currents, sensitive to the P2X receptor inhibitor PPADS, were evoked by approaching the patch-electrode tip close to a neuron, indicating that ATP is released from DRG neurons, to activate P2X receptor. NA increased the frequency of the single-channel events, but such NA effect was not found for DRG neurons transfected with the siRNA to silence the cystic fibrosis transmembrane conductance regulator (CFTR) gene. In the immunocytochemical study using acutely dissociated rat DRG cells, CFTR was expressed in neurons alone, but not satellite cells, fibroblasts, or Schwann cells. It is concluded from these results that CFTR mediates NA-induced ATP efflux from DRG neurons as an ATP channel.
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Affiliation(s)
- Takeshi Kanno
- Division of Bioinformation, Department of Physiology, Hyogo College of Medicine 1-1 Mukogawa-cho, Nishinomiya, 663-8501, Japan
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XIA CM, COLOMB DG, AKBARALI HI, QIAO LY. Prolonged sympathetic innervation of sensory neurons in rat thoracolumbar dorsal root ganglia during chronic colitis. Neurogastroenterol Motil 2011; 23:801-e339. [PMID: 21605284 PMCID: PMC3282529 DOI: 10.1111/j.1365-2982.2011.01728.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
BACKGROUND Peripheral irritation-induced sensory plasticity may involve catecholaminergic innervation of sensory neurons in the dorsal root ganglia (DRG). METHODS Catecholaminergic fiber outgrowth in the thoracolumbar DRG (T13-L2) was examined by tyrosine hydroxylase (TH) immunostaining, or by sucrose-potassium phosphate-glyoxylic acid histofluorescence method. TH level was examined by Western blot. Colonic afferent neurons were labeled by retrograde neuronal tracing. Colitis was induced by intracolonic instillation of tri-nitrobenzene sulfonic acid (TNBS). KEY RESULTS The catecholaminergic fibers formed 'basket-like' structures around the DRG cells. At 7 days following TNBS treatment, the number of DRG neurons surrounded by TH-immunoreactive fibers and the protein levels of TH were significantly increased in T13, L1, and L2 DRGs (two- to threefold, P < 0.05). The DRG neurons that were surrounded by TH immunoreactivity were 200 kDa neurofilament-positive, but not isolectin IB4-positive or calcitonin gene-related peptide-positive. The TH-immunoreactive fibers did not surround but adjoin the specifically labeled colonic afferent neurons, and was co-localized with glial marker S-100. Comparison of the level of TH and the severity of colonic inflammation showed that following TNBS treatment, the degree of colonic inflammation was most severe at day 3, subsided at day 7, and significantly recovered by day 21. However, the levels of TH in T13-L2 DRGs were increased at both 3 days and 7 days post TNBS treatment and persisted up to 21 days (two- to fivefold increase, P < 0.05) as examined. CONCLUSIONS & INFERENCES Colonic inflammation induced prolonged catecholaminergic innervation of sensory neurons, which may have relevance to colitis-induced chronic visceral hypersensitivity and/or referred pain.
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Affiliation(s)
- C.-M. XIA
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, VA, USA
| | - D. G. COLOMB
- Department of Pharmacology and Toxicology, Virginia Commonwealth University School of Medicine, Richmond, VA, USA
| | - H. I. AKBARALI
- Department of Pharmacology and Toxicology, Virginia Commonwealth University School of Medicine, Richmond, VA, USA
| | - L.-Y. QIAO
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, VA, USA
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Yoo HS, Nahm FS, Lee PB, Lee CJ. Early thoracic sympathetic block improves the treatment effect for upper extremity neuropathic pain. Anesth Analg 2011; 113:605-9. [PMID: 21778335 DOI: 10.1213/ane.0b013e3182274803] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND The sympathetic nervous system has important roles in mediating many neuropathic pain conditions. A thoracic sympathetic block (TSB) is a useful therapeutic procedure for neuropathic pain in the upper extremities and thorax. However, no studies have examined the factors related to an improved therapeutic effect of TSB. In this study, we evaluated the influence of potential prognostic factors for a better TSB effect and identified clinically important prognostic factors. METHODS Percutaneous TSB was performed in 51 patients, under fluoroscopic guidance. Data collected for each patient included age, gender, body mass index, diagnosis, pain intensity, and symptom duration. The adjusted odds ratios and 95% confidence intervals for each variable were calculated by logistic regression. RESULTS TSB was more effective in patients with symptom durations of ≤1 year compared with >1 year (P = 0.006; odds ratio, 8.037; 95% confidence interval, 1.808-35.729). Patient age, gender, body mass index, diagnosis, and intensity of pre-TSB pain were not associated with TSB effectiveness. CONCLUSION The results showed that an earlier TSB produced a better outcome for patients with chronic pain syndrome. Thus, early TSB should be performed in patients with chronic pain in the upper extremities.
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Affiliation(s)
- Hyung Seok Yoo
- Department of Anesthesiology and Pain Medicine, School of Medicine, Kyung Hee University, Seoul, Korea.
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Kanno T, Yaguchi T, Nishizaki T. Noradrenaline stimulates ATP release from DRG neurons by targeting beta(3) adrenoceptors as a factor of neuropathic pain. J Cell Physiol 2010; 224:345-51. [PMID: 20432431 DOI: 10.1002/jcp.22114] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Noradrenaline (NA), released in association with sympathetic nerve sprouting into the dorsal root ganglion (DRG) after peripheral nerve injury, may enhance neuropathic pain. ATP serves as a pain mediator; however, NA-regulated ATP mobilizations in the DRG is far from understanding. In the present study, we analyzed ATP mobilizations in acutely dissociated rat DRG neurons by recording single-channel currents through P2X receptor channels as an ATP biosensor in an outside-out patch-clamp configuration and by monitoring real-time enzymatic NADPH fluorescent imaging, and examined the role for beta(3) adrenoceptors in allodynia using an in vivo rat model. We show here that NA stimulates ATP release from DRG neurons as mediated via beta(3) adrenoceptors linked to G(s) protein involving PKA activation, to cause allodynia. This represents a fresh regulatory pathway for neuropathic pain relevant to noradrenergic transmission in the DRG.
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Affiliation(s)
- Takeshi Kanno
- Division of Bioinformation, Department of Physiology, Hyogo College of Medicine, Mukogawa-cho, Nishinomiya, Japan
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Yamamoto S, Kanno T, Yamada K, Yasuda Y, Nishizaki T. Dual regulation of heat-activated K+ channel in rat DRG neurons via α1 and β adrenergic receptors. Life Sci 2009; 85:167-71. [DOI: 10.1016/j.lfs.2009.05.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2009] [Revised: 05/07/2009] [Accepted: 05/14/2009] [Indexed: 11/15/2022]
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rTMS for suppressing neuropathic pain: a meta-analysis. THE JOURNAL OF PAIN 2009; 10:1205-16. [PMID: 19464959 DOI: 10.1016/j.jpain.2009.03.010] [Citation(s) in RCA: 150] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2008] [Revised: 01/21/2009] [Indexed: 12/31/2022]
Abstract
UNLABELLED This pooled individual data (PID)-based meta-analysis collectively assessed the analgesic effect of repetitive transcranial magnetic stimulation (rTMS) on various neuropathic pain states based on their neuroanatomical hierarchy. Available randomized controlled trials (RCTs) were screened. PID was coded for age, gender, pain neuroanatomical origins, pain duration, and treatment parameters analyses. Coded pain neuroanatomical origins consist of peripheral nerve (PN); nerve root (NR); spinal cord (SC); trigeminal nerve or ganglion (TGN); and post-stroke supraspinal related pain (PSP). Raw data of 149 patients were extracted from 5 (1 parallel, 4 cross-over) selected (from 235 articles) RCTs. A significant (P < .001) overall analgesic effect (mean percent difference in pain visual analog scale (VAS) score reduction with 95% confidence interval) was detected with greater reduction in VAS with rTMS in comparison to sham. Including the parallel study (Khedr et al), the TGN subgroup was found to have the greatest analgesic effect (28.8%), followed by PSP (16.7%), SC (14.7%), NR (10.0%), and PN (1.5%). The results were similar when we excluded the parallel study with the greatest analgesic effect observed in TGN (33.0%), followed by SC (14.7%), PSP (10.5%), NR (10.0%), and PN (1.5%). In addition, multiple (vs single, P = .003) sessions and lower (>1 and < or =10 Hz) treatment frequency range (vs >10 Hz) appears to generate better analgesic outcome. In short, rTMS appears to be more effective in suppressing centrally than peripherally originated neuropathic pain states. PERSPECTIVE This is the first PID-based meta-analysis to assess the differential analgesic effect of rTMS on neuropathic pain based on the neuroanatomical origins of the pain pathophysiology and treatment parameters. The derived information serves as a useful resource in regards to treatment parameters and patient population selection for future rTMS-pain studies.
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Gibbs GF, Drummond PD, Finch PM, Phillips JK. Unravelling the pathophysiology of complex regional pain syndrome: focus on sympathetically maintained pain. Clin Exp Pharmacol Physiol 2008; 35:717-24. [PMID: 18215185 DOI: 10.1111/j.1440-1681.2007.04862.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
1. In diseases such as complex regional pain syndrome (CRPS), where neuropathic pain is the primary concern, traditional pain classifications and lesion descriptors are of limited value. To obtain better treatment outcomes for patients, the underlying pathophysiological mechanisms of neuropathic pain need to be elucidated and analysed so that therapeutic targets can be identified and specific treatments developed. 2. In the present review, we examine the current literature on sympathetically maintained pain (SMP), a subset of neuropathic pain, within the context of CRPS. Evidence from both human and animal studies is presented and discussed in terms of its support for the existence of SMP and the mechanistic information it provides. 3. We discuss three current hypotheses that propose both a site and method for sympathetic-sensory coupling: (i) direct coupling between sympathetic and sensory neurons in the dorsal root ganglion; (ii) chemical coupling between sympathetic and nociceptive neuron terminals in skin; and (iii) the development of a-adrenoceptor-mediated supersensitivity in nociceptive fibres in skin in association with the release of inflammatory mediators. 4. Finally, we propose a new hypothesis that integrates the mechanisms of chemical coupling and a-adrenoceptor-mediated supersensitivity. This hypothesis is based on previously unpublished data from our laboratory showing that a histological substrate suitable for sympathetic-sensory coupling exists in normal subjects. In the diseased state, the nociceptive fibres implicated in this substrate may be activated by both endogenous and exogenous noradrenaline. The mediating a-adrenoceptors may be expressed on the nociceptive fibres or on closely associated support cells.
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Affiliation(s)
- Gael F Gibbs
- Division of Health Sciences, Murdoch University, Murdoch, WA, Australia
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Maruo K, Yamamoto H, Yamamoto S, Nagata T, Fujikawa H, Kanno T, Yaguchi T, Maruo S, Yoshiya S, Nishizaki T. Modulation of P2X receptors via adrenergic pathways in rat dorsal root ganglion neurons after sciatic nerve injury. Pain 2006; 120:106-112. [PMID: 16360272 DOI: 10.1016/j.pain.2005.10.016] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2005] [Revised: 10/05/2005] [Accepted: 10/19/2005] [Indexed: 01/27/2023]
Abstract
The present study examined noradrenaline-induced modulation of ATP-evoked currents in dorsal root ganglion (DRG) neurons after sciatic nerve injury (transection). ATP (10 microM) generated fast/mixed type of whole-cell membrane currents, possibly as mediated via P2X(3)/P2X(3)-like receptors, and slow type of the currents, possibly as mediated via P2X(2/3) receptors, in acutely dissociated L4/5 DRG neurons, without significant difference between sham and injury group. For sham group, noradrenaline (10 microM) enhanced fast/mixed type of ATP-evoked currents in ipsilateral DRG neurons, that is not inhibited by H-7, a broad inhibitor of protein kinases, but otherwise it had no effect on slow type of the currents. For injury group, noradrenaline (10 microM) significantly potentiated slow type of ATP-evoked currents in ipsilateral DRG neurons, that is abolished by H-7 or GF109203X, a selective inhibitor of protein kinase C (PKC), while it depressed fast/mixed type of the currents. In the analysis of real-time reverse transcription-polymerase chain reaction, an increase in the mRNAs for alpha(1b), alpha(2a), alpha(2d), and beta(2) adrenergic receptors was found with the ipsilateral DRGs after sciatic nerve injury. Collectively, the results of the present study suggest that noradrenaline potentiates P2X(2/3) receptor currents by activating PKC via alpha(1) adrenergic receptors linked to G(q) protein, perhaps dominantly alpha(1b) adrenergic receptors, in DRG neurons after sciatic nerve injury. This may account for a nociceptive pathway in response to noradrenergic sprouting after peripheral nerve injury.
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Affiliation(s)
- Keishi Maruo
- Department of Physiology, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya 663-8501, Japan Department of Orthopedics, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya 663-8501, Japan
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Kim JH, Min BI, Na HS, Park DS. Relieving effects of electroacupuncture on mechanical allodynia in neuropathic pain model of inferior caudal trunk injury in rat: mediation by spinal opioid receptors. Brain Res 2004; 998:230-6. [PMID: 14751594 DOI: 10.1016/j.brainres.2003.11.045] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The relieving effects of electroacupuncture (EA) on mechanical allodynia and its mechanism related to the spinal opioid system were investigated in a rat model of neuropathic pain. To produce neuropathic pain in the tail, the right superior caudal trunk was resected between the S1 and S2 spinal nerves. Two weeks after the surgery, EA stimulation (2 or 100 Hz, 0.3 ms, 0.2-0.3 mA) was delivered to Zusanli (ST36) for 30 min. The degree of mechanical allodynia was evaluated quantitatively by touching the tail with von Frey hair (2.0 g) at 10 min intervals. These rats were then subjected to an i.t. injection with one of the three specific opioid agonists in successive ways: the mu agonist (DAMGO 25, 50 and 100 pmol), the delta agonist (DADELT II 0.5, 1 and 2 nmol), and the kappa agonist (U50488H 5, 10 and 20 nmol) separated by 10 min in cumulative doses. During 30 min of EA stimulation, specific opioid antagonists were subjected to i.t. injection: the mu antagonist (beta-FNA 5, 10 and 20 nmol), the delta antagonist (naltrindole 5, 10 and 20 nmol), and the kappa antagonist (nor-BNI 3, 6 and 12 nmol) separated by 10 min in cumulative doses. As a result, EA reduced the behavioral signs of mechanical allodynia. Two Hz EA induced a robust and longer lasting effect than 100 Hz. All three opioid agonists also showed relieving effects on mechanical allodynia. However, nor-BNI could not block the EA effects on mechanical allodynia, whereas beta-FNA or naltrindole significantly blocked EA effects. These results suggest that the mu and delta, but not kappa, opioid receptors in the spinal cord of the rat, play important roles in mediating relieving effects on mechanical allodynia induced by 2 Hz EA.
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Affiliation(s)
- Ji Hoon Kim
- Department of East-West Medicine, Graduate School, Kyung Hee University, Seoul, South Korea
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Ko J, Na DS, Lee YH, Shin SY, Kim JH, Hwang BG, Min BI, Park DS. cDNA Microarray Analysis of the Differential Gene Expression in the Neuropathic Pain and Electroacupuncture Treatment Models. BMB Rep 2002; 35:420-7. [PMID: 12297003 DOI: 10.5483/bmbrep.2002.35.4.420] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Partial nerve injury is the main cause of neuropathic pain disorders in humans. Acupuncture has long been used to relieve pain. It is known to relieve pain by controlling the activities of the autonomic nervous system. Although the mechanism of neuropathic pain and analgesic effects of electroacupuncture (EA) have been studied in a rat model system, its detailed mechanism at the molecular level remains unclear. To identify genes that might serve as either markers or explain these distinct biological functions, a cDNA microarray analysis was used to compare the expression of 8,400 genes among three sample groups. Messenger RNAs that were pooled from the spinal nerves of 7 normal, 7 neuropathic pain, and 7 EA treatment rat models were compared. Sixty-eight genes were differentially expressed more than 2-fold in the neuropathic rat model when compared to the normal, and restored to the normal expression level after the EA treatment. These genes are involved in a number of biological processes, including the signal transduction, gene expression, and nociceptive pathways. Confirmation of the differential gene expression was performed by a dotblot analysis. Dot-blotting results showed that the opioid receptor sigma was among those genes. This indicates that opioid-signaling events are involved in neuropathic pain and the analgesic effects of EA. The potential application of these data include the identification and characterization of signaling pathways that are involved in the EA treatment, studies on the role of the opioid receptor in neuropathic pain, and further exploration on the role of selected identified genes in animal models.
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Affiliation(s)
- Jesang Ko
- Asan Institute for Life Sciences, University of Ulsan College of Medicine 138-736, Korea.
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