Intrathecal Clonidine Alleviates Allodynia in Neuropathic Rats

Background Intrathecally administered clonidine increases release of spinal acetylcholine, which may be related to its analgesic action in neuropathic pain. The current study determined the role of spinal muscarinic and nicotinic receptors in the antiallodynic effect of intrathecally administered clonidine in spinal nerve-ligated rats. Methods Allodynia was produced in rats by ligation of the left L5-L6 spinal nerves. Mechanical allodynia was determined by application of von Frey filaments to the left hindpaw. The effect of intrathecal injection of saline, two muscarinic receptor antagonists (atropine and scopolamine), and two nicotinic receptor antagonists (mecamylamine and hexamethonium) on the antiallodynic action produced by intrathecal administration of 20 microg clonidine was assessed in six groups of animals. Each group consisted of six to eight rats. Results Intrathecal injection of saline or muscarinic or nicotinic receptor antagonists did not alter the withdrawal thresholds. The antiallodynic effect produced by intrathecally administered clonidine was attenuated in a dose-dependent manner by intrathecal treatment with muscarinic and nicotinic antagonists. Although nicotinic receptor antagonists only partially attenuated the effect of clonidine, blockade of spinal muscarinic receptors almost abolished the antiallodynic effect of clonidine. Conclusions These results demonstrate that the analgesic effect of intrathecally administered clonidine on neuropathic pain is mediated by spinal muscarinic and nicotinic receptors. Therefore, this study provides functional evidence that spinally released acetylcholine plays a role in the antiallodynic effect of intrathecally administered clonidine in neuropathic pain.

Download Full-text

Synergistic Effect between Intrathecal Non-NMDA Antagonist and Gabapentin on Allodynia Induced by Spinal Nerve Ligation in Rats

Anesthesiology ◽

10.1097/00000542-200002000-00033 ◽

2000 ◽

Vol 92 (2) ◽

pp. 500-500 ◽

Cited By ~ 53

Author(s):

Shao-Rui Chen ◽

James C. Eisenach ◽

Patrick P. McCaslin ◽

Hui-Lin Pan

Keyword(s):

Spinal Cord ◽

Neuropathic Pain ◽

Synergistic Effect ◽

Rat Model ◽

Intrathecal Injection ◽

Spinal Nerve ◽

Water Soluble ◽

Dose Ratio ◽

Intrathecal Catheter ◽

Antiallodynic Effect

Background Glutamate and non-N-methyl-D-aspartate (NMDA) receptors have been implicated in the development of neuroplasticity in the spinal cord in neuropathic pain. The spinal cord has been identified as one of the sites of the analgesic action of gabapentin. In the current study, the authors determined the antiallodynic effect of intrathecal 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) in a rat model of neuropathic pain. Also tested was a hypothesis that intrathecal injection of CNQX and gabapentin produces a synergistic effect on allodynia in neuropathic rats. Methods Allodynia was produced in rats by ligation of the left L5 and L6 spinal nerves. Allodynia was determined by application of von Frey filaments to the left hind paw. Through an implanted intrathecal catheter, 10-100 microg gabapentin or 0.5-8 microg CNQX disodium (a water-soluble formulation of CNQX) was injected in conscious rats. Isobolographic analysis was performed comparing the interaction of intrathecal gabapentin and CNQX using the ED50 dose ratio of 15:1. Results Intrathecal treatment with gabapentin or CNQX produced a dose-dependent increase in the withdrawal threshold to mechanical stimulation. The ED50 for gabapentin and CNQX was 45.9+/-4.65 and 3.4+/-0.22 microg, respectively. Intrathecal injection of a combination of CNQX and gabapentin produced a strong synergistic antiallodynic effect in neuropathic rats. Conclusions This study shows that intrathecal administration of CNQX exhibits an antiallodynic effect in this rat model of neuropathic pain. Furthermore, CNQX and gabapentin, when combined intrathecally, produce a potent synergistic antiallodynic effect on neuropathic pain in spinal nerve-ligated rats.

Download Full-text

GPR55 and GPR119 Receptors Contribute to the Processing of Neuropathic Pain in Rats

Pharmaceuticals ◽

10.3390/ph15010067 ◽

2022 ◽

Vol 15 (1) ◽

pp. 67

Author(s):

Ángel Zúñiga-Romero ◽

Quetzali Rivera-Plata ◽

Jesús Arrieta ◽

Francisco Javier Flores-Murrieta ◽

Juan Rodríguez-Silverio ◽

...

Keyword(s):

Neuropathic Pain ◽

G Protein ◽

Protein Localization ◽

Intrathecal Administration ◽

Spinal Nerve ◽

Spinal Cord Dorsal ◽

Gpr119 Agonist ◽

G Protein Coupled ◽

Dose Dependent ◽

Antiallodynic Effect

Orphan G-protein-coupled receptors (GPCR) comprise a large number of receptors which are widely distributed in the nervous system and represent an opportunity to identify new molecular targets in pain medicine. GPR55 and GPR119 are two orphan GPCR receptors whose physiological function is unclear. The aim was to explore the participation of spinal GPR55 and GPR119 in the processing of neuropathic pain in rats. Mechanical allodynia was evaluated using von Frey filaments. Protein localization and modulation were measured by immunohistochemistry and western blotting, respectively. Intrathecal administration of CID16020046 (selective GPR55 antagonist) or AS1269574 (selective GPR119 agonist) produced a dose-dependent antiallodynic effect, whereas O1062 (GPR55 agonist) and G-protein antagonist peptide dose-dependently prevented the antiallodynic effect of CID16020046 and AS1269574, respectively. Both GPR55 and GPR119 receptors were expressed in spinal cord, dorsal root ganglia and sciatic nerve, but only GPR119 was downregulated after 14 days of spinal nerve ligation. Data suggest that GPR55 and GPR119 participate in the processing of neuropathic pain and could be useful targets to manage neuropathic pain disorders.

Download Full-text

Oral Gabapentin Activates Spinal Cholinergic Circuits to Reduce Hypersensitivity after Peripheral Nerve Injury and Interacts Synergistically with Oral Donepezil

Anesthesiology ◽

10.1097/01.anes.0000267605.40258.98 ◽

2007 ◽

Vol 106 (6) ◽

pp. 1213-1219 ◽

Cited By ~ 45

Author(s):

Ken-ichiro Hayashida ◽

Renée Parker ◽

James C. Eisenach

Keyword(s):

Neuropathic Pain ◽

Nerve Injury ◽

Intrathecal Injection ◽

Spinal Nerve ◽

Male Rats ◽

Additive Interaction ◽

Alzheimer Dementia ◽

Routes Of Administration ◽

Withdrawal Threshold ◽

The Brain

Background Gabapentin administration into the brain of mice reduces nerve injury-induced hypersensitivity and is blocked by intrathecal atropine and enhanced by intrathecal neostigmine. The authors tested the relevance of these findings to oral therapy by examining the efficacy of oral gabapentin to reduce hypersensitivity after nerve injury in rats and its interaction with the clinically used cholinesterase inhibitor, donepezil. Methods Male rats with hypersensitivity after spinal nerve ligation received gabapentin orally, intrathecally, and intracerebroventricularly with or without intrathecal atropine, and withdrawal threshold to paw pressure was determined. The effects of oral gabapentin and donepezil alone and in combination on withdrawal threshold were determined in an isobolographic design. Results Gabapentin reduced hypersensitivity to paw pressure by all routes of administration, and was more potent and with a quicker onset after intracerebroventricular than intrathecal injection. Intrathecal atropine reversed the effect of intracerebroventricular and oral gabapentin. Oral gabapentin and donepezil interacted in a strongly synergistic manner, with an observed efficacy at one tenth the predicted dose of an additive interaction. The gabapentin-donepezil combination was reversed by intrathecal atropine. Conclusions Although gabapentin may relieve neuropathic pain by actions at many sites, these results suggest that its actions in the brain to cause spinal cholinergic activation predominate after oral administration. Side effects, particularly nausea, cannot be accurately determined on rats. Nevertheless, oral donepezil is well tolerated by patients in the treatment of Alzheimer dementia, and the current study provides the rationale for clinical study of combination of gabapentin and donepezil to treat neuropathic pain.

Download Full-text

Locating the Site of Neuropathic Pain In Vivo Using MMP-12-Targeted Magnetic Nanoparticles

Pain Research and Management ◽

10.1155/2019/9394715 ◽

2019 ◽

Vol 2019 ◽

pp. 1-11 ◽

Cited By ~ 3

Author(s):

Syeda Fabeha Husain ◽

Raymond W. M. Lam ◽

Tao Hu ◽

Michael W. F. Ng ◽

Z. Q. G. Liau ◽

...

Keyword(s):

Neuropathic Pain ◽

Magnetic Resonance ◽

Intrathecal Injection ◽

Thermal Hyperalgesia ◽

Spinal Nerve ◽

Iron Oxide Nanoparticle ◽

Anatomical Location ◽

Spinal Nerves ◽

Potential Biomarker

Neuropathic pain remains underrecognised and ineffectively treated in chronic pain sufferers. Consequently, their quality of life is considerably reduced, and substantial healthcare costs are incurred. The anatomical location of pain must be identified for definitive diagnosis, but current neuropsychological tools cannot do so. Matrix metalloproteinases (MMP) are thought to maintain peripheral neuroinflammation, and MMP-12 is elevated particularly in such pathological conditions. Magnetic resonance imaging (MRI) of the peripheral nervous system has made headway, owing to its high-contrast resolution and multiplanar features. We sought to improve MRI specificity of neural lesions, by constructing an MMP-12-targeted magnetic iron oxide nanoparticle (IONP). Its in vivo efficiency was evaluated in a rodent model of neuropathic pain, where the left lumbar 5 (L5) spinal nerve was tightly ligated. Spinal nerve ligation (SNL) successfully induced mechanical allodynia, and thermal hyperalgesia, in the left hind paw throughout the study duration. These neuropathy characteristics were absent in animals that underwent sham surgery. MMP-12 upregulation with concomitant macrophage infiltration, demyelination, and elastin fibre loss was observed at the site of ligation. This was not observed in spinal nerves contralateral and ipsilateral to the ligated spinal nerve or uninjured left L5 spinal nerves. The synthesised MMP-12-targeted magnetic IONP was stable and nontoxic in vitro. It was administered onto the left L5 spinal nerve by intrathecal injection, and decreased magnetic resonance (MR) signal was observed at the site of ligation. Histology analysis confirmed the presence of iron in ligated spinal nerves, whereas iron was not detected in uninjured left L5 spinal nerves. Therefore, MMP-12 is a potential biomarker of neuropathic pain. Its detection in vivo, using IONP-enhanced MRI, may be further developed as a tool for neuropathic pain diagnosis and management.

Download Full-text

Effect of PKC/NF-κB on the Regulation of P2X3 Receptor in Dorsal Root Ganglion in Rats with Sciatic Nerve Injury

Pain Research and Management ◽

10.1155/2020/7104392 ◽

2020 ◽

Vol 2020 ◽

pp. 1-8

Author(s):

Xue Li ◽

Jie Yuan ◽

Xuan Yu ◽

Qin Zhang ◽

Bangyong Qin

Keyword(s):

Neuropathic Pain ◽

Dorsal Root ◽

Regulatory Mechanism ◽

Intrathecal Injection ◽

Intrathecal Administration ◽

Pyrrolidine Dithiocarbamate ◽

Withdrawal Threshold ◽

Protein Levels ◽

Kinase C ◽

Mutual Regulation

Background. Protein kinase C (PKC), nuclear factor-kappa B p65 (NF-κB p65), and P2X3 receptor (P2X3R) play significant roles in the sensitization and transduction of nociceptive signals, which are considered as potential targets for the treatment of neuropathic pain. However, the mechanisms and relationships among them have not been clearly clarified. Methods. 80 rats were randomized and divided into 10 groups (n = 8). Sciatic chronic constriction injury (CCI) rats were intrathecally administered with bisindolylmaleimide I (GF109203X), a PKC-selective antagonist once a day, or pyrrolidine dithiocarbamate (PDTC), an NF-κB inhibitor twice a day. Sham-operated rats were intrathecally administered with saline. Thermal withdrawal latency (TWL) and mechanical withdrawal threshold (MWT) were evaluated in all the groups before CCI operation (baseline) and on the 1st, 3rd, 7th, 10th, and 14th day after CCI operation. Protein levels of p-PKCα, p-NF-κB p65, and P2X3R were analyzed in the CCI ipsilateral L4–6 dorsal root ganglions (DRGs). Results. Intrathecal injection of GF109203X or PDTC alleviated the TWL and MWT in the following 2 weeks after CCI surgery. The protein levels of p-PKCα, p-NF-κB p65, and P2X3R in the ipsilateral DRGs significantly increased after CCI operation, which could be partly reversed by intrathecal administration of GF109203X or PDTC. Conclusion. The upregulation of p-PKCα, p-NF-κB p65, and P2X3R expression in the DRGs of CCI rats was involved in the occurrence and development of neuropathic pain. Phosphorylated PKCα and phosphorylated NF-κB p65 regulated with each other. Phosphorylated NF-κB p65 and PKCα have a mutual regulation relationship with P2X3R, respectively, while the specific regulatory mechanism needs further research.

Download Full-text

Intraspinal Adenosine Induces Spinal Cord Norepinephrine Release in Spinal Nerve-ligated Rats but not in Normal or Sham Controls

Anesthesiology ◽

10.1097/00000542-200306000-00024 ◽

2003 ◽

Vol 98 (6) ◽

pp. 1461-1466 ◽

Cited By ~ 12

Author(s):

Carsten Bantel ◽

Xinhui Li ◽

James C. Eisenach

Keyword(s):

Spinal Cord ◽

Spinal Nerve ◽

Spinal Nerve Ligation ◽

Spinal Cord Dorsal Horn ◽

Sham Operation ◽

Dependent Manner ◽

Norepinephrine Release ◽

Receptor Antagonists ◽

Antinociceptive Effects ◽

Spinal Cord Dorsal

Background Intrathecal adenosine is antinociceptive under conditions of central sensitization, but not in response to acute stimuli in normals. The reasons for this selective circumstance of action remain unclear, but some evidence links adenosine's antinociceptive effects to release of norepinephrine by terminals in the spinal cord. The purpose of this study was to test whether spinal adenosine induces norepinephrine release selectively in settings of hypersensitivity. Methods Rats randomly assigned to spinal nerve ligation, sham operation, or no operation were anesthetized. A microdialysis fiber was implanted in the spinal cord dorsal horn at the L5-L6 level and perfused with artificial cerebrospinal fluid. After washout and a baseline sample period, adenosine at various concentrations was infused through the fiber for 150 min, and samples were collected every 15 min. Results In ligated, but not in sham or normal animals, adenosine perfusion increased norepinephrine in spinal cord microdialysates in a concentration-dependent manner. The effects of adenosine plateaued after 75 min and remained stable until the end of the experiment. Intravenous injection of selective adenosine A1 and A2 receptor antagonists revealed that adenosine's effect on spinal norepinephrine release was A1 receptor mediated. Conclusions This is the first study to provide direct evidence that adenosine is able to release norepinephrine in spinal cord dorsal horns in living animals. However, this effect was only seen in animals after spinal nerve ligation. These data are consistent with behavioral studies demonstrating that adenosine's antinociceptive effects in rats after spinal nerve ligation is totally dependent on intact spinal noradrenergic terminals and can be blocked by spinal alpha 2-adrenergic receptor antagonists.

Download Full-text

Isotalatizidine, a C19-diterpenoid alkaloid, attenuates chronic neuropathic pain through stimulating ERK/CREB signaling pathway-mediated microglial dynorphin A expression

Journal of Neuroinflammation ◽

10.1186/s12974-019-1696-9 ◽

2020 ◽

Vol 17 (1) ◽

Cited By ~ 6

Author(s):

Shuai Shao ◽

Huan Xia ◽

Min Hu ◽

Chengjuan Chen ◽

Junmin Fu ◽

...

Keyword(s):

Neuropathic Pain ◽

Lateral Roots ◽

Intrathecal Injection ◽

Dependent Manner ◽

Dynorphin A ◽

Diterpenoid Alkaloid ◽

P38 Inhibitor ◽

In Vivo Experiments ◽

Underlying Mechanisms

Abstract Background Isotalatizidine is a representative C19-diterpenoid alkaloid extracted from the lateral roots of Aconitum carmichaelii, which has been widely used to treat various diseases on account of its analgesic, anti-inflammatory, anti-rheumatic, and immunosuppressive properties. The aim of this study was to evaluate the analgesic effect of isotalatizidine and its underlying mechanisms against neuropathic pain. Methods A chronic constrictive injury (CCI)-induced model of neuropathic pain was established in mice, and the limb withdrawal was evaluated by the Von Frey filament test following isotalatizidine or placebo administration. The signaling pathways in primary or immortalized microglia cells treated with isotalatizidine were analyzed by Western blotting and immunofluorescence. Results Intrathecal injection of isotalatizidine attenuated the CCI-induced mechanical allodynia in a dose-dependent manner. At the molecular level, isotalatizidine selectively increased the phosphorylation of p38 and ERK1/2, in addition to activating the transcription factor CREB and increasing dynorphin A production in cultured primary microglia. However, the downstream effects of isotalatizidine were abrogated by the selective ERK1/2 inhibitor U0126-EtOH or CREB inhibitor of KG-501, but not by the p38 inhibitor SB203580. The results also were confirmed in in vivo experiments. Conclusion Taken together, isotalatizidine specifically activates the ERK1/2 pathway and subsequently CREB, which triggers dynorphin A release in the microglia, eventually leading to its anti-nociceptive action.

Download Full-text

Role of Spinal NO in Antiallodynic Effect of Intrathecal Clonidine in Neuropathic Rats

Anesthesiology ◽

10.1097/00000542-199812000-00031 ◽

1998 ◽

Vol 89 (6) ◽

pp. 1518-1523 ◽

Cited By ~ 49

Author(s):

Hui-Lin Pan ◽

Shao-Rui Chen ◽

James C. Eisenach

Keyword(s):

Neuropathic Pain ◽

Intrathecal Injection ◽

No Donor ◽

Before And After ◽

Neuropathic Pain Model ◽

Series Of Experiments ◽

Intrathecal Clonidine ◽

Intrathecal Space ◽

Antiallodynic Effect

Background The role of spinal nitric oxide (NO) in neuropathic pain remains uncertain. Although intrathecal clonidine causes NO release in the spinal cord, the functional role of spinal NO in clonidine-produced analgesia has not been examined. The objectives of this study were to assess the role of spinal NO in maintenance of allodynia and to determine the role of spinal NO in the antiallodynic effect of intrathecal clonidine. Methods Allodynia was produced in rats by tight ligation of the left L5-L6 spinal nerves. Intrathecal catheters were inserted with tips in the lumbar intrathecal space. Mechanical allodynia was determined by application of von Frey filaments to the left hindpaw. In the first series of experiments, allodynia was assessed before and after intrathecal injection of saline, L-arginine, an NO donor (SNAP), two NO synthase inhibitors (TRIM and NMMA), or an NO scavenger (PTIO). In the second series of experiments, 20 microg of clonidine was injected intrathecally 15 min after intrathecal injection of saline, TRIM, NMMA, or PTIO. Results Allodynia was not affected significantly by intrathecal injection of L-arginine, SNAP, TRIM, NMMA, or PTIO. The antiallodynic effect produced by intrathecal injection of clonidine was attenuated significantly by pretreatment with TRIM, NMMA, or PTIO. Conclusions These results demonstrate that spinal NO neither contributes significantly to maintenance of allodynia nor produces detectable antiallodynic effect in this neuropathic pain model. Furthermore, this study provides functional evidence that spinal NO plays an important role in the antiallodynic effect of intrathecal clonidine in neuropathic pain.

Download Full-text

Peripheral Nerve Injury Sensitizes the Response to Visceral Distension but Not Its Inhibition by the Antidepressant Milnacipran

Anesthesiology ◽

10.1097/00000542-200403000-00030 ◽

2004 ◽

Vol 100 (3) ◽

pp. 671-675 ◽

Cited By ~ 21

Author(s):

Sang-Wook Shin ◽

James C. Eisenach

Keyword(s):

Neuropathic Pain ◽

Nerve Injury ◽

Visceral Pain ◽

Spinal Nerve ◽

Reflex Response ◽

Dependent Manner ◽

Sprague Dawley ◽

Withdrawal Threshold ◽

Sprague Dawley Rats ◽

Lumbar Spinal

Background Manipulations that cause hypersensitivity to visceral stimuli have been shown to also result in hypersensitivity to somatic stimuli coming from convergent dermatomes, but the converse has not been examined. The authors tested whether lumbar spinal nerve ligation in rats, a common model of neuropathic pain that results in hypersensitivity to somatic stimuli, also leads to hypersensitivity to visceral stimuli coming from convergent dermatomes and whether pharmacology of inhibition differed between these two sensory modalities. Methods Female Sprague-Dawley rats were anesthetized, and the left L5 and L6 spinal nerves were ligated. Animals received either intrathecal saline or milnacipran (0.1-3 microg), and withdrawal thresholds to mechanical testing in the left hind paw, using von Frey filaments, and visceral testing, using balloon colorectal distension, were determined. Results Nerve ligation resulted in decreases in threshold to withdrawal to somatic mechanical stimulation (from 13 +/- 1.8 g to 2.7 +/- 0.7 g) and also in decreases in threshold to reflex response to visceral stimulation (from 60 mmHg to 40 mmHg). Intrathecal milnacipran increased withdrawal threshold to somatic stimulation in a dose-dependent manner but failed to alter the response to noxious visceral stimulation. Conclusions Injury of nerves innervating somatic structures enhances nociception from stimulation of viscera with convergent input from nearby dermatomes, suggesting that somatic neuropathic pain could be accompanied by an increased likelihood of visceral pain. Lack of efficacy of the antidepressant milnacipran against visceral stimuli suggests that visceral hypersensitivity may not share the same pharmacology of inhibition as somatic hypersensitivity after nerve injury.

Download Full-text

Spinal Cord is the Primary Site of Action of the Cannabinoid CB2 Receptor Agonist JWH133 that Suppresses Neuropathic Pain: Possible Involvement of Microglia

The Open Pain Journal ◽

10.2174/1876386301407010001 ◽

2014 ◽

Vol 7 (1) ◽

pp. 1-8

Author(s):

Hiroshi Shimoyama ◽

Makoto Tsuda ◽

Takahiro Masuda ◽

Ryohei Yoshinaga ◽

Keiko Tsukamoto ◽

...

Keyword(s):

Spinal Cord ◽

Neuropathic Pain ◽

Nerve Injury ◽

Intrathecal Administration ◽

Tactile Allodynia ◽

Cb2 Receptor ◽

Analgesic Agents ◽

Inflammatory Drugs ◽

Antiallodynic Effect

Neuropathic pain, a highly debilitating condition that commonly occurs after damage to the nervous system, is often resistant to commonly used analgesic agents such as non-steroidal anti-inflammatory drugs and even opioids.Several studies using rodent models reported that cannabinoid CB2 receptor (CB2R) agonists are effective for treating chronic pain. However, the analgesic mechanism of CB2R agonists in neuropathic pain states is not fully understood. In this study, we investigated the role of CB2Rs in the development and maintenance phases of neuropathic pain, and the mechanism of the CB2R-mediated analgesic effect on neuropathic pain. In a rat model of neuropathic pain, systemic administration of JWH133, a CB2R agonist, markedly improved tactile allodynia, and this effect was prevented by intrathecal pretreatment with AM630, a CB2R antagonist. The antiallodynic effect of intrathecally administered JWH133 was inhibited by intrathecal pretreatment with pertussis toxin or forskolin. In the spinal cord, CB2R expression was significantly increased on post-operative day 3, and persisted for 2 weeks. Furthermore, repeated intrathecal administration of JWH133 notably attenuated the development of tactile allodynia after peripheral nerve injury. In a culture of microglia activated by overexpressing interferon regulatory factor 8, a transcription factor crucial for neuropathic pain, JWH133 treatment suppressed the increased expression of interleukin-1β. Our findings suggest that activation of CB2Rs upregulated in the spinal cord after nerve injury alleviates existing tactile allodynia through the Gi/oadenylate cyclase signaling pathway and suppresses the development of allodynia. This process may reduce the inflammatory response of microglia. Therefore, spinal CB2Rs may be a therapeutic target for the treatment of neuropathic pain.

Download Full-text