• The Korean Journal of Pain
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• 제24권4호
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• pp.185-190
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• 2011

Background: Spinal nerve ligation (SNL) injury in rats produces a pain syndrome that includes mechanical and thermal allodynia. Previous studies have indicated that proinflammatory cytokines such as tumor necrosis factor-${\alpha}$ (TNF-${\alpha}$) play an important role in peripheral mediation of neuropathic pain, and that altered dorsal root ganglion (DRG) function and degree of DRG neuronal apoptosis are associated with spinal nerve injury. The present study was conducted to evaluate the expression of TNF-${\alpha}$ and the extent of apoptosis in the dorsal root ganglion after SNL in rats. Methods: Sprague-Dawley rats were subjected to SNL of the left L5 and L6 spinal nerves distal to the DRG and proximal to the formation of the sciatic nerve. At postoperative day 8, TNF-${\alpha}$ protein levels in the L5.6 DRG were compared between SNL and naive groups using ELISA. In addition, we compared the percentage of neurons injured in the DRG using immunostaining for apoptosis and localization of activated caspase-3. Results: SNL injury produced significant mechanical and cold allodynia throughout the 7-day experimental period. TNF-${\alpha}$ protein levels were increased in the DRG in rats that had undergone SNL ($12.7{\pm}3.2$ pg/100 ${\mu}g$, P < 0.001) when compared with naive rats ($4.1{\pm}1.4$ pg/100 ${\mu}g$). The percentage of neurons or satellite cells co-localized with activated caspase-3 were also significantly higher in rats with SNL than in naive rats (P < 0.001, P < 0.05, respectively). Conclusions: SNL injury produces mechanical and cold allodynia, as well as TNF-${\alpha}$ elevation and apoptosis in the DRG.

• The Korean Journal of Pain
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• 제22권1호
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• pp.21-27
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• 2009

Background: The neuropathic pain arising from nerve injury is difficult to treat and the therapeutic effects of opioid drugs remain debatable. Agonists acting at the ${\alpha}_2$ adrenergic and opioid receptors have analgesic properties and they act synergistically when co-administered in the spinal cord. The lack of subtype-selective pharmacological agents has previously impeded the synergistic effects that are mediated by the adrenergic receptor subtypes. Methods: We created neuropathic pain model by ligating the L5 spinal nerve in Sprague-Dawley rats (n = 18). We divided the rats into three groups (n = 6 for each group), and we administered intraperitoneal morphine (1 mg/kg, 3 mg/kg, 5 mg/kg) and then we measured the mechanical allodynia with using von-Frey filaments for 8 hours. We then injected morphine (5 mg/kg) intraperitoneally, twice a day for 2 weeks. We measured the tactile and cold allodynia in the morphine group (n = 9) and the saline group (n = 9). After 2 weeks, we decapitated the rats and harvested the spinal cords at the level of lumbar enlargement. We compared the ${\alpha}_2$ subtype mRNA expression with that of control group (n = 6) by performing real time polymerase chain reaction (RTPCR). Results: Intraperitoneal morphine reduced the neuropathic pain behavior in the dose-dependent manner. Chronic morphine administration showed an antiallodynic effect on the neuropathic pain rat model. The rats did not display tolerance or hyperalgesia. The expression of the mRNAs of the ${\alpha}_{2A}$, ${\alpha}_{2B}$, ${\alpha}_{2C}$ subtypes decreased, and morphine attenuated this effect. But we could not get statistically proven results. Conclusions: Systemic administration of morphine can attenuate allodynia during both the short-term and long-term time course. Morphine has an influence on the expression of ${\alpha}_2$ receptor subtype mRNA. Yet we need more research to determine the precise effect of morphine on the ${\alpha}_2$ subtype gene expression.

• The Korean Journal of Pain
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• 제27권3호
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• pp.246-252
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• 2014

Background: Neuropathic pain is generally defined as a chronic pain state resulting from peripheral and/or central nerve injury. There is a lack of effective treatment for neuropathic pain, which may possibly be related to poor understanding of pathological mechanisms at the molecular level. Curcumin, a therapeutic herbal extract, has shown to be effectively capable of reducing chronic pain induced by peripheral administration of inflammatory agents such as formalin. In this study, we aimed to show the effect of curcumin on pain behavior and serum COX-2 level in a Chronic Constriction Injury (CCI) model of neuropathic pain. Methods: Wistar male rats (150-200 g, n = 8) were divided into three groups: CCI vehicle-treated, sham-operated, and CCI drug-treated group. Curcumin (12.5, 25, 50 mg/kg, IP) was injected 24 h before surgery and continued daily for 7 days post-surgery. Behavioral tests were performed once before and following the days 1, 3, 5, 7 after surgery. The serum COX-2 level was measured on day 7 after the surgery. Results: Curcumin (50 mg/kg) decreased mechanical and cold allodynia (P < 0.001) and produced a decline in serum COX-2 level (P < 0.001). Conclusions: A considerable decline in pain behavior and serum COX-2 levels was seen in rat following administration of curcumin in CCI model of neuropathic pain. High concentration of Curcumin was able to reduce the chronic neuropathic pain induced by CCI model and the serum level of COX-2.

• The Korean Journal of Pain
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• 제33권3호
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• pp.216-225
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• 2020

Background: Garlic oil is a rich source of organosulfur compounds including diallyl disulfide and diallyl trisulfide. There have been studies showing the neuroprotective actions of these organosulfur compounds. However, the potential of these organosulfur compounds in neuropathic pain has not been explored. The present study was aimed at investigating the pain attenuating potential of diallyl disulfide and diallyl trisulfide in chronic constriction injury (CCI)-induced neuropathic pain in rats. The study also explored their pain-attenuating mechanisms through modulation of H₂S, brain-derived neurotrophin factor (BDNF) and nuclear factor erythroid 2-related factor 2 (Nrf2). Methods: The rats were subjected to CCI injury by ligating the sciatic nerve in four places. The development of neuropathic pain was measured by assessing mechanical hyperalgesia (Randall-Selittotest), mechanical allodynia (Von Frey test), and cold allodynia (acetone drop test) on 14th day after surgery. Results: Administration of diallyl disulfide (25 and 50 mg/kg) and diallyl trisulfide (20 and 40 mg/kg) for 14 days led to a significant reduction in pain in CCI-subjected rats. Moreover, treatment with these organosulfur compounds led to the restoration of H₂S, BDNF and Nrf2 levels in the sciatic nerve and dorsal root ganglia. Co-administration of ANA-12 (BDNF blocker) abolished pain attenuating actions as well as BDNF and the Nrf2 restorative actions of diallyl disulfide and diallyl trisulfide, without modulating H₂S levels. Conclusions: Diallyl disulfide and diallyl trisulfide have the potential to attenuate neuropathic pain in CCI-subjected rats possibly through activation of H₂S-BDNF-Nrf2 signaling pathway.

• The Korean Journal of Pain
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• 제34권1호
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• pp.35-46
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• 2021

Background: The present investigation explored the therapeutic actions of oleuropein along with the possible signaling pathway involved in attenuating neuropathic pain in chronic constriction injury (CCI) and vincristine-induced neuropathic pain in male rats. Methods: Four loose ligatures were placed around the sciatic nerve to induce CCI, and vincristine (50 ㎍/kg) was injected for 10 days to develop neuropathic pain. The development of cold allodynia, mechanical allodynia, and mechanical hyperalgesia was assessed using different pain-related behavioral tests. The levels of H2S, cystathionine-γ-lyase (CSE), cystathionine-β-synthase (CBS), orexin, and nuclear factor erythroid-2-related factor 2 (Nrf2) were measured in the sciatic nerve. Results: Treatment with oleuropein for 14 days led to significant amelioration of behavioral manifestations of neuropathic pain in two pain models. Moreover, oleuropein restored both CCI and vincristine-induced decreases in H2S, CSE, CBS, orexin, and Nrf2 levels. Co-administration of suvorexant, an orexin receptor antagonist, significantly counteracted the pain-attenuating actions of oleuropein and Nrf2 levels without modulating H2S, CSE and CBS. Conclusions: Oleuropein has therapeutic potential to attenuate the pain manifestations in CCI and vincristine-induced neuropathic pain, possibly by restoring the CSE, CBS, and H2S, which may subsequently increase the expression of orexin and Nrf2 to ameliorate behavioral manifestations of pain.

• The Korean Journal of Pain
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• 제36권4호
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• pp.441-449
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• 2023

Background: Hypertonic saline is used for treating chronic pain; however, clinical studies that aid in optimizing therapeutic protocols are lacking. We aimed to determine the concentration of intrathecally injected hypertonic saline at which the effect reaches its peak as well as the underlying γ-aminobutyric acid (GABA) receptor-related antinociceptive mechanism. Methods: Spinal nerve ligation (SNL; left L5 and L6) was performed to induce neuropathic pain in rats weighing 250-300 g. Experiment 1: one week after implanting the intrathecal catheter, 60 rats were assigned randomly to intrathecal injection with 0.45%, 0.9%, 2.5%, 5%, 10%, and 20% NaCl, followed by behavioral testing at baseline and after 30 minutes, 2 hours, 1 day, and 1 week to determine the minimal concentration which produced maximal analgesia. Experiment 2: after determining the optimal intrathecal hypertonic saline concentration, 60 rats were randomly divided into four groups: Sham, hypertonic saline without pretreatment, and hypertonic saline after pretreatment with one of two GABA receptor antagonists (GABA_A [bicuculline], or GABA_B [phaclofen]). Behavioral tests were performed at weeks 1 and 3 following each treatment. Results: Hypertonic saline at concentrations greater than 5% alleviated SNL-induced mechanical allodynia and had a significant therapeutic effect, while showing a partial time- and dose-dependent antinociceptive effect on thermal and cold hyperalgesia. However, pretreatment with GABA receptor antagonists inhibited the antinociceptive effect of 5% NaCl. Conclusions: This study indicates that the optimal concentration of hypertonic saline for controlling mechanical allodynia in neuropathic pain is 5%, and that its analgesic effect is related to GABA_A and GABA_B receptors.

• The Journal of Korean Physical Therapy
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• 제22권1호
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• pp.67-73
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• 2010

Purpose: We tested whether repetitive transcranial magnetic stimulation (rTMS) improved recovery following spinal cord injury (SCI) in rats with transplantation of adipose tissue-derived stromal cells (ATSCs). Methods: Twenty Sprague-Dawley rats (200-250 g, female) were used. Moderate spinal cord injury was induced at the T9 level by a New York University (NYU) impactor. The rat ATSCs (approximately $5{\times}10^5$ cells) were injected into the perilesional area at 9 days after SCI. Starting four days after transplantation, rTMS (25 Hz, 0.1 Tesla, pulse width=$370{\mu}s$, on/off time=3 sec/3 sec) was applied daily for 7 weeks. Functional recovery was assessed using the Basso, Beattie, and Bresnahan (BBB) locomotor rating scale as well as pain responses for thermal and cold stimuli. Results: Both groups showed similar, gradual improvement of locomotor function. rTMS stimulation decreased thermal and cold hyperalgesia after 7 weeks, but sham stimulation did not. Conclusion: rTMS after transplantation of ATSCs in an SCI model may reduce thermal hyperalgesia and cold allodynia, and may be an adjuvant therapeutic tool for pain control after stem cell therapy in SCI.

• The Journal of Korean Physical Therapy
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• 제22권3호
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• pp.99-105
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• 2010

Purpose: The purpose of this study was to evaluate the development of pain behavior and the expression of CCL2/CCR2 and CX3CL1/CX3CR1 at above and below the level of hemisection of the spinal cord in a rat model. Methods: Spinal cords of adult female Sprague-Dawley rats (n= 16, 200~250 g, 6~8 weeks old) were hemisected at T13 on the right side to develop the spinal hemisection injury model. We compared behavioral responses of the hemisection and of a sham surgery group. Behavioral tests for motor function (by the BBB locomotor scale), and for pain response for mechanical and cold allodynia were assessed postoperatively (PO) for 21 days. Expression of mRNA for chemokines and their receptors (CCL2/CCR2 and CX3CL1/CX3CR1) below and above the level of the spinal cord dissection were examined by RT-PCR. Results: We observed gradual motor improvement and the development of mechanical and cold allodynia on the ipsilateral hindpaw after spinal hemisection injury. We also found upregulation of mRNA expression of CCL2/CCR2 both above and below the level of spinal cord dissection but CX3CL1/CX3CR1 mRNA expression. Conclusion: Upregulation of CCL2/CCR2 is associated with neuropathic pain after spinal hemisection injury. CCL2/CCR2 may play an important role in the development of neuropathic pain after SCI as well as of peripheral neuropathic pain. These findings may improve understanding of the pathophysiological mechanism of neuropathic pain after SCI.

• Journal of Korean Neurosurgical Society
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• 제50권5호
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• pp.420-425
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• 2011

Objective : Excitatory amino acids play important roles in the development of secondary pathology following spinal cord injury (SCI). This study was designed to evaluate morphological changes in the dorsal horn of the spinal cord and assess profiles of pain behaviors following intraspinal injection of N-methyl-D-aspartate (NMDA) or quisqualate (QUIS) in rats. Methods : Forty male Sprague-Dawley rats were randomized into three groups : a sham, and two experimental groups receiving injections of 125 mM NMDA or QUIS into their spinal dorsal horn. Following injection, hypersensitivity to cold and mechanical stimuli, and excessive grooming behaviors were assessed serially for four weeks. At the end of survival periods, morphological changes in the spinal cord were evaluated. Results : Cold allodynia was developed in both the NMDA and QUIS groups, which was significantly higher in the QUIS group than in the NMDA group. The mechanical threshold for the ipsilateral hind paw in both QUIS and NMDA groups was significantly lower than that in the control group. The number of groomers was significantly higher in the NMDA group than in the QUIS group. The size of the neck region of the spinal dorsal horn, but not the superficial layer, was significantly smaller in the NMDA and QUIS groups than in the control group. Conclusion : Intraspinal injection of NMDA or QUIS can be used as an excitotoxic model of SCI for further research on spinal neuropathic pain.

• The Korean Journal of Pain
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• 제19권2호
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• pp.241-243
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• 2006

Central pain is defined as pain associated with lesions of the central nervous system, and is among the most intractable of chronic pain syndromes. A 47 year-old-female, who had right arm and shoulder pain, was diagnosed with syringomyelia of the Arnold Chiari malformation type I and received foramen magnum decompression and a syringo-subarachnoid shunt. After the operation, the evoked pain was improved, but she complained of a continuous burning pain, coupled with cold and tactile allodynia. This symptom failed to fully subside on administration of oral medicine; therefore, brachial plexus block was performed, which relieved her pain transiently. Through repeated trials, a gradual decrease in the pain intensity and frequency was found. However, the way in which brachial plexus block improves spinal central pain is not completely known.