• Korean Journal of Medicinal Crop Science
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• v.16 no.3
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• pp.183-187
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• 2008

Nerve injury can lead to neuropathic pain, which is often resistant to current analgesics and interventional therapeutic methods. Extracellular signal-regulated kinase (ERK) plays important role in the induction of neuropathic pain. We explored the antinociceptive effect of curcumin and its effect on ERK in the spinal cord in the neuropathic pain model of rats induced by chronic constriction injury (CCI) of the sciatic nerve. In injured rats, mechanical allodynia, which is one of characteristics of neuropathic pain developed and the activation of ERK in spinal cord significantly increased compared with control group. However, administration of curcumin (50 mg/kg/day p.o) for 7 days started from one day before the injury prevented the development of mechanical allodynia and increase of ERK phosphorylation. These results indicate that curcumin can be a new therapeutic agent in the treatment of neuropathic pain.

• The Korean Journal of Pain
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• v.22 no.1
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• pp.16-20
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• 2009

Background: Zaprinast is an inhibitor of phosphodiesterase 5, 6 and 9. Phosphodiesterase inhibitors could produce anti-nociceptive effects by promoting the accumulation of cGMP. We hypothesized that intrathecal zaprinast could attenuate the allodynia induced by chronic constriction injury of the sciatic nerve in rat. Methods: Sprague-Dawley rats were prepared with four loose ligations of the left sciatic nerve just proximal to the trifurcation into the sural, peroneal and tibial nerve branches. Tactile allodynia was measured by applying von Frey filaments to the lesioned hindpaw. The thresholds for the withdrawal responses were assessed. Zaprinast ($3-100{\mu}g$) was administered intrathecally by the direct lumbar puncture method to obtain the dose-response curve and the 50% effective dose ($ED_{50}$). Measurements were taken before and 15, 30, 45, 60, 90, 120, and 180 min after the intrathecal doses of zaprinast. The side effects were also observed. Results: Intrathecal zaprinast resulted in a dose-dependent antiallodynic effect. The maximal effects occurred within 15-30 min and then they gradually decreased down to the baseline level over time in all the groups. There was a dose dependent increase in the magnitude and duration of the effect. The $ED_{50}$ value was $17.4{\mu}g$ (95% confidence intervals; $14.7-20.5{\mu}g$). No severe motor weakness or sedation was observed in any of the rats. Conclusions: Intrathecally administered zaprinast produced a dose-dependent antiallodynic effect in the chronic constriction injury neuropathic pain model. These findings suggest that spinal phosphodiesterase 5, 6 and 9 may play an important role in the modulation of neuropathic pain.

• The Korean Journal of Pain
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• v.35 no.4
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• pp.383-390
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• 2022

Background: The treatment of trigeminal neuralgia remains a challenging issue. Stem cells from human exfoliated deciduous teeth (SHED) provide optimized therapy for chronic pain. This study aimed to investigate the mechanisms underlying the attenuation of trigeminal neuralgia by SHED. Methods: Trigeminal neuralgia was induced by chronic constriction injury of the infraorbital nerve. The mechanical threshold was assessed after model establishment and local SHED transplantation. Endoplasmic reticulum (ER) morphology and Caspase12 expression in trigeminal ganglion (TG) was evaluated as well. BiP expression was observed in PC12 cells induced by tunicamycin. Results: The local transplantation of SHED could relieve trigeminal neuralgia in rats. Further, transmission electron microscopy revealed swelling of the ER in rats with trigeminal neuralgia. Moreover, SHED inhibited the tunicamycin-induced up-regulated expression of BiP mRNA and protein in vitro. Additionally, SHED decreased the up-regulated expression of Caspase12 mRNA and protein in the TG of rats caused by trigeminal neuralgia after chronic constriction injury of the infraorbital nerve mode. Conclusions: This findings demonstrated that SHED could alleviate pain by relieving ER stress which provide potential basic evidence for clinical pain treatment.

• The Korean Journal of Physiology and Pharmacology
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• v.16 no.6
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• pp.387-392
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• 2012

In this study, we examined the antinociceptive effect of Cyperi rhizoma (CR) and Corydalis tuber (CT) extracts using a chronic constriction injury-induced neuropathic pain rat model. After the ligation of sciatic nerve, neuropathic pain behavior such as mechanical allodynia and thermal hyperalgesia were rapidly induced and maintained for 1 month. Repeated treatment of CR or CT (per oral, 10 or 30 mg/kg, twice a day) was performed either in induction (day 0~5) or maintenance (day 14~19) period of neuropathic pain state. Treatment of CR or CT at doses of 30 mg/kg in the induction and maintenance periods significantly decreased the nerve injury-induced mechanical allodynia. In addition, CR and CT at doses of 10 or 30 mg/kg alleviated thermal heat hyperalgesia when they were treated in the maintenance period. Finally, CR or CT (30 mg/kg) treated during the induction period remarkably reduced the nerve injury-induced phosphorylation of NMDA receptor NR1 subunit (pNR1) in the spinal dorsal horn. Results of this study suggest that extracts from CR and CT may be useful to alleviate neuropathic pain.

• The Korean Journal of Pain
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• v.35 no.4
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• pp.391-402
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• 2022

Background: The mechanism of peripheral axon transport in neuropathic pain is still unclear. Chemokine ligand 13 (CXCL13) and its receptor (C-X-C chemokine receptor type 5, CXCR5) as well as GABA transporter 1 (GAT-1) play an important role in the development of pain. The aim of this study was to explore the axonal transport of CXCL13/CXCR5 and GAT-1 with the aid of the analgesic effect of botulinum toxin type A (BTX-A) in rats. Methods: Chronic constriction injury (CCI) rat models were established. BTX-A was administered to rats through subcutaneous injection in the hind paw. The pain behaviors in CCI rats were measured by paw withdrawal threshold and paw withdrawal latencies. The levels of CXCL13/CXCR5 and GAT-1 were measured by western blots. Results: The subcutaneous injection of BTX-A relieved the mechanical allodynia and heat hyperalgesia induced by CCI surgery and reversed the overexpression of CXCL13/CXCR5 and GAT-1 in the spinal cord, dorsal root ganglia (DRG), sciatic nerve, and plantar skin in CCI rats. After 10 mmol/L colchicine blocked the axon transport of sciatic nerve, the inhibitory effect of BTX-A disappeared, and the levels of CXCL13/CXCR5 and GAT-1 in the spinal cord and DRG were reduced in CCI rats. Conclusions: BTX-A regulated the levels of CXCL13/CXCR5 and GAT-1 in the spine and DRG through axonal transport. Chemokines (such as CXCL13) may be transported from the injury site to the spine or DRG through axonal transport. Axon molecular transport may be a target to enhance pain management in neuropathic pain.

• Biomolecules & Therapeutics
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• v.24 no.3
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• pp.252-259
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• 2016

Neuropathic pain is a complex state showing increased pain response with dysfunctional inhibitory neurotransmission. The TREK family, one of the two pore domain $K^+$ (K2P) channel subgroups were focused among various mechanisms of neuropathic pain. These channels influence neuronal excitability and are thought to be related in mechano/thermosensation. However, only a little is known about the expression and role of TREK-1 and TREK-2, in neuropathic pain. It is performed to know whether TREK-1 and/or 2 are positively related in dorsal root ganglion (DRG) of a mouse neuropathic pain model, the chronic constriction injury (CCI) model. Following this purpose, Reverse Transcription Polymerase Chain Reaction (RT-PCR) and western blot analyses were performed using mouse DRG of CCI model and compared to the sham surgery group. Immunofluorescence staining of isolectin-B4 (IB4) and TREK were performed. Electrophysiological recordings of single channel currents were analyzed to obtain the information about the channel. Interactions with known TREK activators were tested to confirm the expression. While both TREK-1 and TREK-2 mRNA were significantly overexpressed in DRG of CCI mice, only TREK-1 showed significant increase (~9 fold) in western blot analysis. The TREK-1-like channel recorded in DRG neurons of the CCI mouse showed similar current-voltage relationship and conductance to TREK-1. It was easily activated by low pH solution (pH 6.3), negative pressure, and riluzole. Immunofluorescence images showed the expression of TREK-1 was stronger compared to TREK-2 on IB4 positive neurons. These results suggest that modulation of the TREK-1 channel may have beneficial analgesic effects in neuropathic pain patients.

• The Korean Journal of Pain
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• v.33 no.3
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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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• v.35 no.3
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• pp.271-279
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• 2022

Background: Inflammation is known to underlie the pathogenesis in neuropathic pain. This study investigated the anti-inflammatory and neuroprotective mechanisms involved in antinociceptive effects of co-administration of acetaminophen and L-carnosine in chronic constriction injury (CCI)-induced peripheral neuropathy in male Wistar rats. Methods: Fifty-six male Wistar rats were randomly divided into seven experimental groups (n = 8) treated with normal saline/acetaminophen/acetaminophen + L-carnosine. CCI was used to induce neuropathic pain in rats. Hyperalgesia and allodynia were assessed using hotplate and von Frey tests, respectively. Investigation of spinal proinflammatory cytokines and antioxidant system were carried out after twenty-one days of treatment. Results: The results showed that the co-administration of acetaminophen and L-carnosine significantly (P < 0.001) increased the paw withdrawal threshold to thermal and mechanical stimuli in ligated rats compared to the ligated naïve group. There was a significant (P < 0.001) decrease in the levels of nuclear factor kappa light chain enhancer B cell inhibitor, calcium ion, interleukin-1-beta, and tumour necrotic factor-alpha in the spinal cord of the group coadministered with acetaminophen and L-carnosine compared to the ligated control group. Co-administration with acetaminophen and L-carnosine increased the antioxidant enzymatic activities and reduced the lipid peroxidation in the spinal cord. Conclusions: Co-administration of acetaminophen and L-carnosine has anti-inflammatory effects as a mechanism that mediate its antinociceptive effects in CCI-induced peripheral neuropathy in Wistar rat.

• The Korean Journal of Pain
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• v.27 no.3
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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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• v.33 no.1
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• pp.13-22
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• 2020

Background: The continuous search for a novel neuropathic pain drug with few or no side effects has been a main focus of researchers for decades. This study investigated the antinociceptive and neuroprotective effects of bromelain in sciatic nerve ligation-induced neuropathic pain in Wistar rats. Methods: Forty-eight Wistar rats randomly divided into eight groups comprised of six animals each were used for this study. Peripheral neuropathy was induced via chronic constriction of the common sciatic nerve. Thermal hyperalgesic and mechanical allodynia were assessed using a hotplate and von Frey filaments, respectively. The functional recovery and structural architecture of the ligated sciatic nerve were evaluated using the sciatic functional index test and a histological examination of the transverse section of the sciatic nerve. The neuroprotective effects of bromelain were investigated in the proximal sciatic nerve tissue after 21 days of treatment. Results: Bromelain significantly (P < 0.05) attenuated both the thermal hyperalgesia and mechanical allodynic indices of neuropathic pain. There were improvements in sciatic function and structural integrity in rats treated with bromelain. These rats showed significant (P < 0.05) increases in sciatic nerve nuclear transcription factors (nuclear factor erythroid-derived-2-related factors-1 [NrF-1] and NrF-2), antioxidant enzymes (superoxide dismutase and glutathione), and reduced membranelipid peroxidation compared with the ligated control group. Conclusions: This study suggest that bromelain mitigated neuropathic pain by enhancing the activities of nuclear transcription factors (NrF-1 and NrF-2) which increases the antioxidant defense system that abolish neuronal stress and structural disorganization.