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Casili G, Lanza M, Filippone A, Cucinotta L, Paterniti I, Repici A, Capra AP, Cuzzocrea S, Esposito E, Campolo M. Dimethyl Fumarate (DMF) Alleviated Post-Operative (PO) Pain through the N-Methyl-d-Aspartate (NMDA) Receptors. Antioxidants (Basel) 2022; 11:antiox11091774. [PMID: 36139848 PMCID: PMC9495385 DOI: 10.3390/antiox11091774] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 08/30/2022] [Accepted: 09/06/2022] [Indexed: 11/29/2022] Open
Abstract
The management of post-operative (PO) pain has generally been shown to be inadequate; therefore, acquiring a novel understanding of PO pain mechanisms would increase the therapeutic options available. There is accumulating evidence to implicate N-methyl-d-aspartate (NMDA) receptors in the induction and maintenance of central sensitization during pain states by reinforcing glutamate sensory transmission. It is known that DMF protects from oxidative glutamate toxicity. Therefore, NMDA receptor antagonists have been implicated in peri-operative pain management. Recent advances demonstrated that dimethyl fumarate (DMF), a non-opioid and orally bioavailable drug, is able to resolve neuroinflammation through mechanisms that drive nociceptive hypersensitivity. Therefore, in this study, we evaluated the role of DMF on pain and neuroinflammation in a mouse model of PO pain. An incision of the hind paw was performed, and DMF at two different doses (30 and 100 mg/kg) was administered by oral gavage for five consecutive days. Mechanical allodynia, thermal hyperalgesia and locomotor dysfunction were evaluated daily for five days after surgery. Mice were sacrificed at day 7 following PO pain induction, and hind paw and lumbar spinal cord samples were collected for histological and molecular studies. DMF administration significantly reduced hyperalgesia and allodynia, alleviating motor disfunction. Treatment with DMF significantly reduced histological damage, counteracted mast cell activation and reduced the nuclear factor kappa-light-chain-enhancer of the activated B cell (NF-κB) inflammatory pathway, in addition to downregulating tumor necrosis factor-α (TNF-α), Interleukin-1β (Il-1β) and Il-4 expression. Interestingly, DMF treatment lowered the activation of NMDA receptor subtypes (NR2B and NR1) and the NMDA-receptor-interacting PDZ proteins, including PSD93 and PSD95. Furthermore, DMF interfered with calcium ion release, modulating nociception. Thus, DMF administration modulated PO pain, managing NMDA signaling pathways. The results suggest that DMF positively modulated persistent nociception related to PO pain, through predominantly NMDA-receptor-operated calcium channels.
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Cao J, Zhou MX, Chen X, Sun M, Wei C, Peng Q, Cheng Z, Sun W, Wang H. Sec-O-Glucosylhamaudol Inhibits RANKL-Induced Osteoclastogenesis by Repressing 5-LO and AKT/GSK3β Signaling. Front Immunol 2022; 13:880988. [PMID: 35558084 PMCID: PMC9087042 DOI: 10.3389/fimmu.2022.880988] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Accepted: 03/31/2022] [Indexed: 12/01/2022] Open
Abstract
Sec-O-glucosylhamaudol (SOG), an active flavonoid compound derived from the root of Saposhnikovia divaricata (Turcz. ex Ledeb.) Schischk., exhibits analgesic, anti-inflammatory, and high 5-lipoxygenase (5-LO) inhibitory effects. However, its effect on osteoclastogenesis was unclear. We demonstrated that SOG markedly attenuated RANKL-induced osteoclast formation, F-actin ring formation, and mineral resorption by reducing the induction of key transcription factors NFATc1, c-Fos, and their target genes such as TRAP, CTSK, and DC-STAMP during osteoclastogenesis. Western blotting showed that SOG significantly inhibited the phosphorylation of AKT and GSK3β at the middle–late stage of osteoclastogenesis without altering calcineurin catalytic subunit protein phosphatase-2β-Aα expression. Moreover, GSK3β inhibitor SB415286 partially reversed SOG-induced inhibition of osteoclastogenesis, suggesting that SOG inhibits RANKL-induced osteoclastogenesis by activating GSK3β, at least in part. 5-LO gene silencing by small interfering RNA in mouse bone marrow macrophages markedly reduced RANKL-induced osteoclastogenesis by inhibiting NFATc1. However, it did not affect the phosphorylation of AKT or GSK3β, indicating that SOG exerts its inhibitory effects on osteoclastogenesis by suppressing both the independent 5-LO pathway and AKT-mediated GSK3β inactivation. In support of this, SOG significantly improved bone destruction in a lipopolysaccharide-induced mouse model of bone loss. Taken together, these results suggest a potential therapeutic effect for SOG on osteoclast-related bone lysis disease.
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Affiliation(s)
- Jinjin Cao
- Putuo People's Hospital, School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Ming-Xue Zhou
- Department of Neurology, Ruikang Hospital of Guangxi Traditional Chinese Medicine (TCM) University, Nanning, China
| | - Xinyan Chen
- Putuo People's Hospital, School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Menglu Sun
- Putuo People's Hospital, School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Congmin Wei
- Putuo People's Hospital, School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Qisheng Peng
- Key Laboratory of Zoonoses Research, Ministry of Education, Institute of Zoonosis, Jilin University, Changchun, China
| | - Zhou Cheng
- Putuo People's Hospital, School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Wanchun Sun
- Key Laboratory of Zoonoses Research, Ministry of Education, Institute of Zoonosis, Jilin University, Changchun, China
| | - Hongbing Wang
- Putuo People's Hospital, School of Life Sciences and Technology, Tongji University, Shanghai, China
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Oh SH, Kim SW, Kim DJ, Kim SH, Lim KJ, Lee K, Jung KT. Sec-O-glucosylhamaudol mitigates inflammatory processes and autophagy via p38/JNK MAPK signaling in a rat neuropathic pain model. Korean J Pain 2021; 34:405-416. [PMID: 34593658 PMCID: PMC8494959 DOI: 10.3344/kjp.2021.34.4.405] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 07/20/2021] [Accepted: 07/20/2021] [Indexed: 01/14/2023] Open
Abstract
Background This study investigated the effect of intrathecal Sec-O-glucosylhamaudol (SOG) on the p38/c-Jun N-terminal kinase (JNK) signaling pathways, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB)-related inflammatory responses, and autophagy in a spinal nerve ligation (SNL)-induced neuropathic pain model. Methods The continuous administration of intrathecal SOG via an osmotic pump was performed on male Sprague–Dawley rats (n = 50) with SNL-induced neuropathic pain. Rats were randomized into four groups after the 7th day following SNL and treated for 2 weeks as follows (each n = 10) Group S, sham-operated; Group D, 70% dimethylsulfoxide; Group SOG96, SOG at 96 μg/day; and Group SOG192, SOG at 192 μg/day. The paw withdrawal threshold (PWT) test was performed to assess neuropathic pain. Western blotting of the spinal cord (L5) was performed to measure changes in the expression of signaling pathway components, cytokines, and autophagy. Additional studies with naloxone challenge (n = 10) and cells were carried out to evaluate the potential mechanisms underlying the effects of SOG. Results Continuous intrathecal SOG administration increased the PWT with p38/JNK mitogen-activated protein kinase (MAPK) pathway and NF-κB signaling pathway inhibition, which induced a reduction in proinflammatory cytokines with the concomitant downregulation of autophagy. Conclusions SOG alleviates mechanical allodynia, and its mechanism is thought to be related to the regulation of p38/JNK MAPK and NF-κB signaling pathways, associated with autophagy during neuroinflammatory processes after SNL.
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Affiliation(s)
- Seon Hee Oh
- School of Medicine, Chosun University, Gwangju, Korea
| | - Suk Whee Kim
- Department of Anesthesiology and Pain Medicine, Chosun University Hospital, Gwangju, Korea
| | - Dong Joon Kim
- Department of Anesthesiology and Pain Medicine, Chosun University Hospital, Gwangju, Korea.,Department of Anesthesiology and Pain Medicine, School of Medicine, Chosun University, Gwangju, Korea
| | - Sang Hun Kim
- Department of Anesthesiology and Pain Medicine, Chosun University Hospital, Gwangju, Korea.,Department of Anesthesiology and Pain Medicine, School of Medicine, Chosun University, Gwangju, Korea
| | - Kyung Joon Lim
- Department of Anesthesiology and Pain Medicine, Chosun University Hospital, Gwangju, Korea.,Department of Anesthesiology and Pain Medicine, School of Medicine, Chosun University, Gwangju, Korea
| | - Kichang Lee
- Cardiovascular Reseach Center, Massachusetts General Hospital, Boston, MA, USA
| | - Ki Tae Jung
- Department of Anesthesiology and Pain Medicine, Chosun University Hospital, Gwangju, Korea.,Department of Anesthesiology and Pain Medicine, School of Medicine, Chosun University, Gwangju, Korea
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Li Y, Kim WM, Kim SH, You HE, Kang DH, Lee HG, Choi JI, Yoon MH. Prostaglandin D 2 contributes to cisplatin-induced neuropathic pain in rats via DP2 receptor in the spinal cord. Korean J Pain 2021; 34:27-34. [PMID: 33380565 PMCID: PMC7783857 DOI: 10.3344/kjp.2021.34.1.27] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Revised: 10/24/2020] [Accepted: 10/28/2020] [Indexed: 11/05/2022] Open
Abstract
Background Chemotherapy-induced peripheral neuropathy (CIPN) is a major reason for stopping or changing anticancer therapy. Among the proposed pathomechanisms underlying CIPN, proinflammatory processes have attracted increasing attention. Here we assessed the role of prostaglandin D2 (PGD2) signaling in cisplatin-induced neuropathic pain. Methods CIPN was induced by intraperitoneal administration of cisplatin 2 mg/kg for 4 consecutive days using adult male Sprague-Dawley rats. PGD2 receptor DP1 and/or DP2 antagonists were administered intrathecally and the paw withdrawal thresholds were measured using von Frey filaments. Spinal expression of DP1, DP2, hematopoietic PGD synthase (H-PGDS), and lipocalin PGD synthase (L-PGDS) proteins were analyzed by western blotting. Results The DP1 and DP2 antagonist AMG 853 and the selective DP2 antagonist CAY10471, but not the DP1 antagonist MK0524, significantly increased the paw withdrawal threshold compared to vehicle controls (P = 0.004 and P < 0.001, respectively). Western blotting analyses revealed comparable protein expression levels in DP1 and DP2 in the spinal cord. In the CIPN group the protein expression level of L-PGDS, but not of H-PGDS, was significantly increased compared to the control group (P < 0.001). Conclusions The findings presented here indicate that enhanced PGD2 signaling, via upregulation of L-PGDS in the spinal cord, contributes to mechanical allodynia via DP2 receptors in a cisplatin-induced neuropathic pain model in rats, and that a blockade of DP2 receptor activation may present a novel therapeutic target for managing CIPN.
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Affiliation(s)
- Yaqun Li
- Department of Anesthesiology and Pain Medicine, Chonnam National University Hospital, Chonnam National University Medical School, Gwangju, Korea
| | - Woong Mo Kim
- Department of Anesthesiology and Pain Medicine, Chonnam National University Hospital, Chonnam National University Medical School, Gwangju, Korea.,Department of Anesthesiology and Pain Medicine, Chonnam National University Hwasun Hospital, Hwasun, Korea
| | - Seung Hoon Kim
- Department of Anesthesiology and Pain Medicine, Chonnam National University Hospital, Chonnam National University Medical School, Gwangju, Korea
| | - Hyun Eung You
- Department of Anesthesiology and Pain Medicine, Chonnam National University Hwasun Hospital, Hwasun, Korea
| | - Dong Ho Kang
- Department of Anesthesiology and Pain Medicine, Chonnam National University Hospital, Chonnam National University Medical School, Gwangju, Korea
| | - Hyung Gon Lee
- Department of Anesthesiology and Pain Medicine, Chonnam National University Hospital, Chonnam National University Medical School, Gwangju, Korea.,Center for Creative Biomedical Scientists, Chonnam National University Medical School, Gwangju, Korea
| | - Jeong Il Choi
- Department of Anesthesiology and Pain Medicine, Chonnam National University Hospital, Chonnam National University Medical School, Gwangju, Korea.,Center for Creative Biomedical Scientists, Chonnam National University Medical School, Gwangju, Korea
| | - Myung Ha Yoon
- Department of Anesthesiology and Pain Medicine, Chonnam National University Hospital, Chonnam National University Medical School, Gwangju, Korea.,Center for Creative Biomedical Scientists, Chonnam National University Medical School, Gwangju, Korea
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Li Y, Kang DH, Kim WM, Lee HG, Kim SH, You HE, Choi JI, Yoon MH. Systemically administered neurotensin receptor agonist produces antinociception through activation of spinally projecting serotonergic neurons in the rostral ventromedial medulla. Korean J Pain 2021; 34:58-65. [PMID: 33380568 PMCID: PMC7783846 DOI: 10.3344/kjp.2021.34.1.58] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 12/12/2020] [Accepted: 12/16/2020] [Indexed: 11/05/2022] Open
Abstract
Background Supraspinal delivery of neurotensin (NTS), which may contribute to the effect of a systemically administered agonist, has been reported to be either pronociceptive or antinociceptive. Here, we evaluated the effects of systemically administered NTSR1 agonist in a rat model of neuropathic pain and elucidated the underlying supraspinal mechanism. Methods Neuropathic pain was induced by L5 and L6 spinal nerve ligation in male Sprague-Dawley rats. The effects of intraperitoneally administered NTSR1 agonist PD 149163 was assessed using von Frey filaments. To examine the role of 5-HT neurotransmission, a serotonin (5-HT) receptor antagonist dihydroergocristine was pretreated intrathecally, and spinal microdialysis studies were performed to measure the change in extracellular level of 5-HT in response to PD 149163 administration. To investigate the supraspinal mechanism, NTSR1 antagonist 48692 was microinjected into the rostral ventromedial medulla (RVM) prior to systemic PD 149163. Additionally, the effect of intrathecal DHE on intra-RVM PD 149163 was assessed. Results Intraperitoneally administered PD 149163 exhibited a dose-dependent attenuation of mechanical allodynia. This effect was partially reversed by intrathecal pretreatment with dihydroergocristine and was accompanied by an increased extracellular level of 5-HT in the spinal cord. The PD 149163-produced antinociception was also blocked by intra-RVM SB 48692. Direct injection of PD 149163 into the RVM mimicked the maximum effect of the same drug delivered intraperitoneally, which was reversed by intrathecal dihydroergocristine. Conclusions These observations indicate that systemically administered NTSR1 agonist produces antinociception through the NTSR1 in the RVM, activating descending serotonergic projection to release 5-HT into the spinal dorsal horn.
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Affiliation(s)
- Yaqun Li
- Department of Anesthesiology and Pain Medicine, Chonnam National University Hospital, Chonnam National University Medical School, Gwangju, Korea
| | - Dong Ho Kang
- Department of Anesthesiology and Pain Medicine, Chonnam National University Hospital, Chonnam National University Medical School, Gwangju, Korea
| | - Woong Mo Kim
- Department of Anesthesiology and Pain Medicine, Chonnam National University Hospital, Chonnam National University Medical School, Gwangju, Korea.,Department of Anesthesiology and Pain Medicine, Chonnam National University Hwasun Hospital, Hwasun, Korea
| | - Hyung Gon Lee
- Department of Anesthesiology and Pain Medicine, Chonnam National University Hospital, Chonnam National University Medical School, Gwangju, Korea.,Center for Creative Biomedical Scientists, Chonnam National University Medical School, Gwangju, Korea
| | - Seung Hoon Kim
- Department of Anesthesiology and Pain Medicine, Chonnam National University Hospital, Chonnam National University Medical School, Gwangju, Korea
| | - Hyun Eung You
- Department of Anesthesiology and Pain Medicine, Chonnam National University Hwasun Hospital, Hwasun, Korea
| | - Jeong Il Choi
- Department of Anesthesiology and Pain Medicine, Chonnam National University Hospital, Chonnam National University Medical School, Gwangju, Korea.,Center for Creative Biomedical Scientists, Chonnam National University Medical School, Gwangju, Korea
| | - Myung Ha Yoon
- Department of Anesthesiology and Pain Medicine, Chonnam National University Hospital, Chonnam National University Medical School, Gwangju, Korea.,Center for Creative Biomedical Scientists, Chonnam National University Medical School, Gwangju, Korea
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Lee HY, Ki YJ, Park SY, Cho SY, Seo J, Lim KJ, Jung KT. Antinociceptive effects of intrathecal cimifugin treatment: a preliminary rat study based on formalin test. Anesth Pain Med (Seoul) 2020; 15:478-485. [PMID: 33329852 PMCID: PMC7724115 DOI: 10.17085/apm.20032] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 06/16/2020] [Accepted: 08/05/2020] [Indexed: 01/20/2023] Open
Abstract
Background Cimifugin is one of the components of the root of Saposhnikovia divaricata. The extract derived from S. divaricata is traditionally used as an analgesic. This study was conducted to evaluate the analgesic effect of intrathecal cimifugin in the formalin test. Methods Male Sprague–Dawley rats (n = 20) were randomized into four groups for intrathecal administration of 70% dimethylsulfoxide and various doses of cimifugin (100 μg, 300 μg, and 1,000 μg). The typical flinch response after the injection of 5% formalin into the hind paw was assessed in two distinct phases: phase 1 until 10 min, and phase 2 from 10 min to 60 min. ED50 values were calculated via linear regression. Results Intrathecal cimifugin significantly reduced the flinch response in both phases of the formalin test. Significant antinociceptive effects of cimifugin were found with the dose of 300 μg in phase 1 and the dose of 100 μg in phase 2. The ED50 value (95% confidence intervals) of intrathecal cimifugin was 696.1 (360.8–1,342.8) μg during phase 1 and 1,242.8 (42.0–48,292.5) μg during phase 2. Conclusions Intrathecal cimifugin has an antinociceptive effect against formalin-induced pain. Cimifugin has an anti-inflammatory effect at low concentrations, and non-inflammatory analgesic effect at higher concentrations.
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Affiliation(s)
- Hyun Young Lee
- Department of Anesthesiology and Pain Medicine, School of Medicine, Chosun University, Gwangju, Korea.,Department of Anesthesiology and Pain Medicine, Chosun University Hospital, Gwangju, Korea
| | - Young Joon Ki
- Department of Anesthesiology and Pain Medicine, Chosun University Hospital, Gwangju, Korea.,Department of Medicine, Graduate School, Chosun University, Gwangju, Korea
| | - Su Yeong Park
- Department of Anesthesiology and Pain Medicine, Chosun University Hospital, Gwangju, Korea
| | - Soo Yeon Cho
- Department of Anesthesiology and Pain Medicine, Chosun University Hospital, Gwangju, Korea
| | - Jinyoung Seo
- Department of Anesthesiology and Pain Medicine, Chosun University Hospital, Gwangju, Korea
| | - Kyung Joon Lim
- Department of Anesthesiology and Pain Medicine, School of Medicine, Chosun University, Gwangju, Korea.,Department of Anesthesiology and Pain Medicine, Chosun University Hospital, Gwangju, Korea
| | - Ki Tae Jung
- Department of Anesthesiology and Pain Medicine, School of Medicine, Chosun University, Gwangju, Korea.,Department of Anesthesiology and Pain Medicine, Chosun University Hospital, Gwangju, Korea
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Cheong Y, Kim M, Kim N, Hwang B. Effect of two-week continuous epidural administration of 2% lidocaine on mechanical allodynia induced by spinal nerve ligation in rats. Anesth Pain Med (Seoul) 2020; 15:334-343. [PMID: 33329833 PMCID: PMC7713833 DOI: 10.17085/apm.20033] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 06/30/2020] [Accepted: 06/30/2020] [Indexed: 11/17/2022] Open
Abstract
Background Lidocaine is an effective against certain types of neuropathic pain. This study aimed to investigate whether timing of initiating continuous epidural infusion of lidocaine affected the glial activation and development of neuropathic pain induced by L5/6 spinal nerve ligation (SNL) in rats. Methods Following L5/6 SNL, rats were epidurally infused 2% lidocaine (drug infusion initiated on days 1, and 7 post SNL model establishment) or saline (saline infusion initiated on day 1 post SNL model establishment) continuously for 14 days. Mechanical allodynia of the hind paw to von Frey filament stimuli was determined prior to surgery, postoperative day 3, and once weekly after SNL model establishment. At 7 days after the infusion of saline or lidocaine ended, spinal activation of proinflammatory cytokines and astrocytes was evaluated immunohistochemically, using antibodies to interleukin-6 (IL-6) and glial fibrillary acidic protein (GFAP). Results Continuous epidural administration of 2% lidocaine for 14 days increased the mechanical withdrawal threshold regardless of the difference in timing of initiating lidocaine administration. Epidurally infusing 2% lidocaine inhibited nerve ligation-induced IL-6 and GFAP activation. In the 2% lidocaine infusion group, rats maintained the increased mechanical withdrawal threshold even at 7 days after the discontinuation of 2% lidocaine infusion. Conclusions Continuous epidural administration of 2% lidocaine inhibited the development of SNL-induced mechanical allodynia and suppressed IL-6 and GFAP activation regardless of the difference in timing of initiating lidocaine administration.
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Affiliation(s)
- Yuseon Cheong
- Department of Anesthesiology and Pain Medicine, Kangwon National University Hospital, Kangwon National University School of Medicine, Chuncheon, Korea
| | - Minsoo Kim
- Department of Anesthesiology and Pain Medicine, Kangwon National University Hospital, Kangwon National University School of Medicine, Chuncheon, Korea
| | - Namyoong Kim
- Department of Anesthesiology and Pain Medicine, Kangwon National University Hospital, Kangwon National University School of Medicine, Chuncheon, Korea
| | - Byeongmun Hwang
- Department of Anesthesiology and Pain Medicine, Kangwon National University Hospital, Kangwon National University School of Medicine, Chuncheon, Korea
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Antinociceptive effects of nefopam modulating serotonergic, adrenergic, and glutamatergic neurotransmission in the spinal cord. Neurosci Lett 2020; 731:135057. [PMID: 32450186 DOI: 10.1016/j.neulet.2020.135057] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 04/10/2020] [Accepted: 05/15/2020] [Indexed: 11/23/2022]
Abstract
The present study investigated the effects of intrathecal nefopam on the pain behavior and on the extracellular levels of serotonin (5-HT), norepinephrine (NE), and glutamate in the spinal cord, in a rat model of pain induced by formalin. Nefopam was intrathecally administered 10 min prior to the formalin test to assess its antinociceptive effects. In another cohorts of animals, dihydroergocristine, yohimbine, or (RS)-α-Methylserine-O-phosphate (MSOP), a serotonergic, α-2 adrenergic receptor, or group III metabotropic glutamate receptor antagonist, respectively, were administered prior to the application of nefopam in the formalin test. Microdialysis studies were conducted to measure the extracellular levels of 5-HT, NE, and glutamate in the spinal cord following nefopam administration. Intrathecal nefopam reduced formalin-induced behavior in both phases of the test. The blockade of serotonergic or adrenergic receptors partially reversed the analgesic effects of nefopam in the first phase of the formalin test whereas MSOP reversed these effects in both phases. The microdialysis results revealed that intrathecal nefopam significantly increased 5-HT and NE levels and attenuated the formalin-induced release of glutamate in the spinal cord. Thus, the present data suggest that the increase in the extracellular levels of 5-HT and NE, and reductions in glutamate release in the spinal cord, may have contributed to the analgesic effects of nefopam.
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