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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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Abstract
Aim of review Many chronic pain conditions remain difficult to treat, presenting a high burden to society. Conditions such as complex regional pain syndrome may be maintained or exacerbated by sympathetic activity. Understanding the interactions between sympathetic nervous system and sensory system will help to improve the effective management of pathological pain including intractable neuropathic pain and persistent inflammatory pain. Method We first described the discovery of abnormal connections between sympathetic and sensory neurons. Subsequently, the functional roles of sympathetic sprouting in altered neuronal excitability and increased pain sensitivity were discussed. The mechanisms of the sympathetic sprouting were focusing on its relationship with neurotrophins, local inflammation, and abnormal spontaneous activity. Finally, we discussed clinical implications and conflicting findings in the laboratory and clinical research with respect to the interaction between sympathetic system and sensory system. Recent findings The findings that sprouting of sympathetic fibers into the sensory ganglia (dorsal root ganglion) after peripheral nerve injury, offers a possible explanation of the sympathetic involvement in pain. It is also suggested that releases of adenosine triphosphate (ATP), in addition to norepinephrine, from sympathetic nerve endings play important roles in sympathetic-mediated pain. New evidence indicates the importance of sympathetic innervation in local inflammatory responses. Summary Hopefully, this review will reinvigorate the study of sympathetic-sensory interactions in chronic pain conditions, and help to better understand how sympathetic system contributes to this serious clinical problem.
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Affiliation(s)
- Si-Si Chen
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, USA
| | - Jun-Ming Zhang
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, USA
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Does norepinephrine influence pain behavior mediated by dorsal root ganglia?: a pilot study. Clin Orthop Relat Res 2011; 469:2568-76. [PMID: 21312078 PMCID: PMC3148377 DOI: 10.1007/s11999-011-1798-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2010] [Accepted: 01/20/2011] [Indexed: 01/31/2023]
Abstract
BACKGROUND Postganglionic neurons in the sympathetic nervous system reportedly are involved in lumbar radicular pain and release norepinephrine (NE), a neurotransmitter. Increased numbers of sympathetic nerve fibers have been found in dorsal root ganglion (DRG) neurons in a root constriction model. Whether this is a reasonable model for pain, however, is unclear QUESTIONS/PURPOSES We asked whether: (1) painful behaviors occurred in the root constriction model; (2) NE enhanced the excitability of DRG neurons in the root constriction model; and (3) which adrenoceptors were related to the mediation of the NE effects. METHODS The L5 root was sutured proximal to the DRG as the root constriction model. Behavioral tests were performed until 28 days after surgery. At 10 to 14 days after the root constriction, DRG neurons were quickly excised and digested with collagenase for electrophysiologic studies. Action potentials were recorded from single DRG neurons using a whole-cell patch clamp technique. NE (10 μmol/L) was directly applied to the DRG neurons. The adrenergic sensitivity was examined in combination with antagonists. RESULTS The rats with root constriction exhibited painful behavior. NE increased the excitability of DRG neurons in the root constriction model. The effects of NE were inhibited by pretreatment with an α-antagonist and α(2)-antagonist but not an α(1)-antagonist. CONCLUSIONS Our observations suggest NE plays an important role in generating lumbar radicular pain mainly via α(2)-adrenoceptors. CLINICAL RELEVANCE An α(2)-antagonist may be an appropriate agent for trials to treat lumbar radicular pain.
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Sympathectomy reduces mechanical allodynia, tumor necrosis factor-alpha expression, and dorsal root ganglion apoptosis following nerve root crush injury. Spine (Phila Pa 1976) 2008; 33:1163-9. [PMID: 18469688 DOI: 10.1097/brs.0b013e31817144fc] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN An analysis of pain behavior and neuronal apoptosis in the dorsal root ganglion (DRG) following crush injury to the L5 nerve root, with or without surgical sympathectomy. OBJECTIVES To determine whether sympathectomy prevents pain behavior and to compare pain behavior with expression of tumor necrosis factor (TNF)-alpha and apoptosis in the DRG. SUMMARY OF BACKGROUND DATA Sympathetic block is used to relieve symptoms in radiculopathy patients. One effect of the block is improvement of blood flow to the nerve. However, this beneficial effect continues longer than the expected duration of local anesthesia, suggesting an unknown neuroprotective effect involving interference with sympathetic activity. METHODS Sprague-Dawley rats (n = 102) were used and divided into 4 experimental groups. In the crush group, animals received a crush injury to the L5 nerve root. In the sympathectomy group, animals received sympathectomy (Syx) on the left side. In the Syx + crush group, both sympathectomy and crush injury were performed. In the sham group, the surgical procedure was the same, but neither sympathectomy nor crush injury took place. Mechanical allodynia was determined in 4 groups. Expression of TNF-alpha was compared in rats with crush injury, with and without sympathectomy. Using immunostaining for caspase 3, NeuN, and GFAP, localization of apoptotic cells was observed. In addition, we compared the percentage of neurons undergoing apoptosis in the DRG. RESULTS Sympathectomy prevented mechanical allodynia throughout the 14-day experimental period. TNF-alpha expression was increased in the DRG following crush-only injury, whereas it was decreased in animals undergoing sympathectomy after the crush injury. DRG apoptosis in the crush group was significantly higher than in the sympathectomy group at day 7 (P < 0.05). CONCLUSION Surgical sympathectomy reduced mechanical allodynia for 14 days after nerve root crush injury, and that DRG apoptosis was decreased in injured animals that underwent sympathectomy. Sympathetic block may not only cause an increase in nerve blood flow, but may also prevent the development of significant TNF-alpha elevation, DRG apoptosis, and neuropathic pain.
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Zhao C, Chen L, Tao YX, Tall JM, Borzan J, Ringkamp M, Meyer RA, Raja SN. Lumbar sympathectomy attenuates cold allodynia but not mechanical allodynia and hyperalgesia in rats with spared nerve injury. THE JOURNAL OF PAIN 2007; 8:931-7. [PMID: 17693138 DOI: 10.1016/j.jpain.2007.06.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2006] [Revised: 05/30/2007] [Accepted: 06/17/2007] [Indexed: 11/24/2022]
Abstract
UNLABELLED In certain patients with neuropathic pain, the pain is dependent on activity in the sympathetic nervous system. To investigate whether the spared nerve injury model (SNI) produced by injury to the tibial and common peroneal nerves and leaving the sural nerve intact is a model for sympathetically maintained pain, we measured the effects of surgical sympathectomy on the resulting mechanical allodynia, mechanical hyperalgesia, and cold allodynia. Decreases of paw withdrawal thresholds to von Frey filament stimuli and increases in duration of paw withdrawal to pinprick or acetone stimuli were observed in the ipsilateral paw after SNI, compared with their pre-SNI baselines. Compared with sham surgery, surgical lumbar sympathectomy had no effect on the mechanical allodynia and mechanical hyperalgesia induced by SNI. However, the sympathectomy significantly attenuated the cold allodynia induced by SNI. These results suggest that the allodynia and hyperalgesia to mechanical stimuli in the SNI model is not sympathetically maintained. However, the sympathetic nervous system may be involved, in part, in the mechanisms of cold allodynia in the SNI model. PERSPECTIVE The results of our study suggest that the SNI model is not an appropriate model of sympathetically maintained mechanical allodynia and hyperalgesia but may be useful to study the mechanisms of cold allodynia associated with sympathetically maintained pain states.
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Affiliation(s)
- Chengshui Zhao
- Department of Anesthesiology and Critical Care Medicine, Baltimore, Maryland, USA
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Pertin M, Allchorne AJ, Beggah AT, Woolf CJ, Decosterd I. Delayed sympathetic dependence in the spared nerve injury (SNI) model of neuropathic pain. Mol Pain 2007; 3:21. [PMID: 17672895 PMCID: PMC1950869 DOI: 10.1186/1744-8069-3-21] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2007] [Accepted: 07/31/2007] [Indexed: 11/23/2022] Open
Abstract
Background Clinical and experimental studies of neuropathic pain support the hypothesis that a functional coupling between postganglionic sympathetic efferent and sensory afferent fibers contributes to the pain. We investigated whether neuropathic pain-related behavior in the spared nerve injury (SNI) rat model is dependent on the sympathetic nervous system. Results Permanent chemical sympathectomy was achieved by daily injection of guanethidine (50 mg/kg s.c.) from age P8 to P21. SNI was performed at adulthood followed by 11 weeks of mechanical and thermal hypersensitivity testing. A significant but limited effect of the sympathectomy on SNI-induced pain sensitivity was observed. The effect was delayed and restricted to cold allodynia-like behavior: SNI-related cold scores were lower in the sympathectomized group compared to the control group at 8 and 11 weeks after the nerve injury but not before. Mechanical hypersensitivity tests (pinprick and von Frey hair threshold tests) showed no difference between groups during the study period. Concomitantly, pericellular tyrosine-hydroxylase immunoreactive basket structures were observed around dorsal root ganglia (DRG) neurons 8 weeks after SNI, but were absent at earlier time points after SNI and in sham operated controls. Conclusion These results suggest that the early establishment of neuropathic pain-related behavior after distal nerve injury such as in the SNI model is mechanistically independent of the sympathetic system, whereas the system contributes to the maintenance, albeit after a delay of many weeks, of response to cold-related stimuli.
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Affiliation(s)
- Marie Pertin
- Anesthesiology Pain Research Unit, Department of Anesthesiology, University Hospital Center and University of Lausanne, BH 10-CHUV, CH-1011 Lausanne, Switzerland
- Department of Cell Biology and Morphology, Faculty of Biology and Medicine, University of Lausanne, Bugnon 9, CH-1005 Lausanne, Switzerland
| | - Andrew J Allchorne
- Neural Plasticity Research Group, Department of Anesthesia and Critical Care, Massachusetts General Hospital and Harvard Medical School, Charlestown MA 02921, USA
- Centre for Neuroscience Research, Division of Veterinary Biomedical Sciences Royal (Dick) School of Veterinary Studies University of Edinburgh Summerhall, Edinburgh EH9 1QH, UK
| | - Ahmed T Beggah
- Anesthesiology Pain Research Unit, Department of Anesthesiology, University Hospital Center and University of Lausanne, BH 10-CHUV, CH-1011 Lausanne, Switzerland
- Department of Cell Biology and Morphology, Faculty of Biology and Medicine, University of Lausanne, Bugnon 9, CH-1005 Lausanne, Switzerland
| | - Clifford J Woolf
- Neural Plasticity Research Group, Department of Anesthesia and Critical Care, Massachusetts General Hospital and Harvard Medical School, Charlestown MA 02921, USA
| | - Isabelle Decosterd
- Anesthesiology Pain Research Unit, Department of Anesthesiology, University Hospital Center and University of Lausanne, BH 10-CHUV, CH-1011 Lausanne, Switzerland
- Department of Cell Biology and Morphology, Faculty of Biology and Medicine, University of Lausanne, Bugnon 9, CH-1005 Lausanne, Switzerland
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Han DW, Kweon TD, Kim KJ, Lee JS, Chang CH, Lee YW. Does the tibial and sural nerve transection model represent sympathetically independent pain? Yonsei Med J 2006; 47:847-51. [PMID: 17191315 PMCID: PMC2687826 DOI: 10.3349/ymj.2006.47.6.847] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Neuropathic pain can be divided into sympathetically maintained pain (SMP) and sympathetically independent pain (SIP). Rats with tibial and sural nerve transection (TST) produce neuropathic pain behaviors, including spontaneous pain, tactile allodynia, and cold allodynia. The present study was undertaken to examine whether rats with TST would represent SMP- or SIP-dominant neuropathic pain by lumbar surgical sympathectomy. The TST model was generated by transecting the tibial and sural nerves, leaving the common peroneal nerve intact. Animals were divided into the sympathectomy group and the sham group. For the sympathectomy group, the sympathetic chain was removed bilaterally from L2 to L6 one week after nerve transection. The success of the sympathectomy was verified by measuring skin temperature on the hind paw and by infra red thermography. Tactile allodynia was assessed using von Frey filaments, and cold allodynia was assessed using acetone drops. A majority of the rats exhibited withdrawal behaviors in response to tactile and cold stimulations after nerve stimulation. Neither tactile allodynia nor cold allodynia improved after successful sympathectomy, and there were no differences in the threshold of tactile and cold allodynia between the sympathectomy and sham groups. Tactile allodynia and cold allodynia in the neuropathic pain model of TST are not dependent on the sympathetic nervous system, and this model can be used to investigate SIP syndromes.
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Affiliation(s)
- Dong Woo Han
- Department of Anesthesiology and Pain Medicine and Anesthesia and Pain Research Institute, Yonsei University College of Medicine, Seoul, Korea
| | - Tae Dong Kweon
- Department of Anesthesiology and Pain Medicine and Anesthesia and Pain Research Institute, Yonsei University College of Medicine, Seoul, Korea
| | - Ki Jun Kim
- Department of Anesthesiology and Pain Medicine and Anesthesia and Pain Research Institute, Yonsei University College of Medicine, Seoul, Korea
| | - Jong Seok Lee
- Department of Anesthesiology and Pain Medicine and Anesthesia and Pain Research Institute, Yonsei University College of Medicine, Seoul, Korea
| | - Chul Ho Chang
- Department of Anesthesiology and Pain Medicine and Anesthesia and Pain Research Institute, Yonsei University College of Medicine, Seoul, Korea
| | - Youn-Woo Lee
- Department of Anesthesiology and Pain Medicine and Anesthesia and Pain Research Institute, Yonsei University College of Medicine, Seoul, Korea
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Abstract
A number of good animal models have been developed in recent years that provide insights into the mechanisms of neuropathic pain. It now becomes evident that there are two separate peripheral components influencing neuropathic pain: one dependent on the hyperexcitability of axotomized dorsal root ganglion (DRG) neurons and the other independent of this hyperexcitability. The purpose of this review is to consider one of these components, the hyperexcitability of axotomized DRG neurons, as one of the important mechanisms underlying neuropathic pain. Several hours after nerve lesions, some axotomized DRG neurons become hyperexcitable and begin to show ongoing discharges that last many days or weeks. These ectopic discharges then enter the spinal cord and induce central sensitization, the underlying central mechanism for the generation of pain and allodynia. Although the exact causes of the development of hyperexcitability and ectopic discharges are not clear, various ion channels seem to play important roles, particularly sodium channels. In addition, important modulatory factors for ectopic discharges are purinergic and adrenergic components of the sympathetic nervous system. These findings suggest that manipulating sodium channels and/or adrenergic and purinergic receptors on axotomized DRG cells may give neuropathic pain sufferers some relief that is not available from present treatment regimens.
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Affiliation(s)
- Jin Mo Chung
- Marine Biomedical Institute and Department of Anatomy & Neurosciences, University of Texas Medical Branch, Galveston, Texas 77555-1069, USA
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Yen LD, Bennett GJ, Ribeiro-da-Silva A. Sympathetic sprouting and changes in nociceptive sensory innervation in the glabrous skin of the rat hind paw following partial peripheral nerve injury. J Comp Neurol 2006; 495:679-90. [PMID: 16506190 DOI: 10.1002/cne.20899] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Previous studies have suggested that sympathetic sprouting in the periphery may contribute to the development and persistence of sympathetically maintained pain in animal models of neuropathic pain. In the present study, we examined changes in the cutaneous innervation in rats with a chronic constriction injury to the sciatic nerve. At several periods postinjury, hind paw skin was harvested and processed by using a monoclonal antibody against dopamine-beta-hydroxylase to detect sympathetic fibers and a polyclonal antibody against calcitonin gene-related peptide to identify peptidergic sensory fibers. We observed migration and branching of sympathetic fibers into the upper dermis of the hind paw skin, where they were normally absent. This migration was first detected at 2 weeks, peaked at 4-6 weeks, and lasted for at least 20 weeks postlesion. At 8 weeks postlesion, there was a dramatic increase in the density of peptidergic fibers in the upper dermis. Quantification revealed that densities of peptidergic fibers 8 weeks postlesion were significantly above levels in sham animals. The ectopic sympathetic fibers did not innervate blood vessels but formed a novel association and wrapped around sprouted peptidergic nociceptive fibers. Our data show a long-term sympathetic and sensory innervation change in the rat hind paw skin after the chronic constriction injury. This novel fiber arrangement after nerve lesion may play an important role in the development and persistence of sympathetically maintained neuropathic pain after partial nerve lesions.
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Affiliation(s)
- Laurene D Yen
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec H3G 1Y6, Canada
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Grelik C, Bennett GJ, Ribeiro-da-Silva A. Autonomic fibre sprouting and changes in nociceptive sensory innervation in the rat lower lip skin following chronic constriction injury. Eur J Neurosci 2005; 21:2475-87. [PMID: 15932605 DOI: 10.1111/j.1460-9568.2005.04089.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In this study we used immunocytochemistry to investigate whether autonomic fibres sprouted in the skin of the lower lip in a rat model of neuropathic pain. We used a bilateral chronic constriction injury (CCI) of the mental nerve (MN), a branch of the trigeminal nerve. In this model, we also studied the accompanying changes in peptidergic [calcitonin gene-related peptide (CGRP)-immunoreactive] sensory fibres, as well as in trkA receptor immunoreactivity in the sensory nerves. Autonomic (sympathetic and parasympathetic) fibre sprouting was first observed 1 week post-injury with a peak in the number of sprouted fibres occurring at 4 and 6 weeks post-CCI. CGRP-IR fibres almost disappeared at 2 weeks post-CCI, but quickly sprouted, leading to a significant peak above sham levels 4 weeks post-injury. trkA receptor expression was found to be up-regulated in small cutaneous nerves 4 weeks post-CCI, returning to sham levels by 8 weeks post-CCI. There was no sympathetic fibre sprouting in the trigeminal ganglion following CCI. At 4 weeks post-CCI, rats displayed spontaneous, directed grooming to the area innervated by the MN that was not seen in sham animals, which we interpreted as a sign of spontaneous pain or dysesthesiae. Collectively, our findings indicate that as a result of autonomic sprouting due to CCI of the MN, remaining intact nociceptive fibres may potentially develop sensitivity to sympathetic and parasympathetic stimulation, which may have a role in the generation of abnormal pain following nerve injury.
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Affiliation(s)
- C Grelik
- Department of Pharmacology & Therapeutics, McGill University, 3655 Prom. Sir-William-Osler, Montreal, Quebec, Canada H3G 1Y6
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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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Lee DH, Iyengar S, Lodge D. The role of uninjured nerve in spinal nerve ligated rats points to an improved animal model of neuropathic pain. Eur J Pain 2003; 7:473-9. [PMID: 12935800 DOI: 10.1016/s1090-3801(03)00019-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
L5 and L6 spinal nerve ligation (SNL) in rats leads to behavioral signs of neuropathic pain including mechanical allodynia. The purposes of this study were to investigate the role of the intact L4 spinal nerve in the development of mechanical allodynia following L5 and L6 SNL and, as a result, to develop a modified model of neuropathic pain. As a first set of experiments, in addition to tight ligation of the left L5 and L6 spinal nerves, the intact L4 spinal nerve was manipulated either (1) by gentle repeated stretching of the L4 spinal nerve immediately after L5 and L6 SNL or (2) by intermittent mechanical stimulation to the ipsilateral paw during the first week after SNL. Tactile sensitivity was measured by determining the foot withdrawal threshold before and after SNL. Mild irritation of L4 spinal nerve and application of mechanical stimuli to the ipsilateral paw significantly increased the development of mechanical allodynia after SNL. In a second set of experiments, SNL was produced by tightly ligating only the left L5 spinal nerve with or without a loop of 5-0 chromic gut placed loosely around the L4 spinal nerve. This additional L4 loop significantly increased long-lasting tactile sensitivity compared to L5 SNL alone. These results suggest that afferent activity of the intact L4 spinal nerve aids in the development of mechanical allodynia in the SNL model of neuropathic pain. The addition of a chromic gut loop around the intact L4 spinal nerve can augment the development of mechanical allodynia following SNL of L5. We propose this latter as a useful and practical animal model of neuropathic pain.
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Affiliation(s)
- Doo H Lee
- Lilly Research Laboratories, Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN 46285, USA.
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Xie J, Park SK, Chung K, Chung JM. The effect of lumbar sympathectomy in the spinal nerve ligation model of neuropathic pain. THE JOURNAL OF PAIN 2001; 2:270-8. [PMID: 14622806 DOI: 10.1054/jpai.2001.24559] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
To evaluate the sympathetic dependency of pain behaviors in an animal model of neuropathic pain, the effect of surgical sympathectomy on the mechanical sensitivity of the hindpaw was examined in rats with L5 spinal nerve ligation. Mechanical sensitivity was determined by measuring foot withdrawal thresholds to mechanical stimulation with von Frey filaments applied to the base of the third or fourth toe. Tight ligation of the segmental L5 spinal nerve led to the development of mechanical hypersensitivity in the hindpaw. The effects of 2 different procedures of surgical lumbar sympathectomy on mechanical hypersensitivity were compared, limited (resection of sympathetic chain/ganglia L2 to L4 segments) and extensive (resection of L2 to L6 segments) sympathectomies. Mechanical hypersensitivity produced by L5 spinal nerve ligation was partially but significantly reduced by both sympathectomy procedures. In a separate group of rats, the L5 spinal nerve was ligated while irritating the neighboring L4 spinal nerve. This procedure produced a lesser degree of mechanical hypersensitivity, and subsequent sympathectomy had no effect on these animals. These data suggest that sympathectomy is effective in this model only when the animals show severe mechanical hypersensitivity.
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Affiliation(s)
- J Xie
- Marine Biomedical Institute, The University of Texas Medical Branch, Galveston, 77555, USA
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