1
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Szabo B. Presynaptic Adrenoceptors. Handb Exp Pharmacol 2024. [PMID: 38755350 DOI: 10.1007/164_2024_714] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/18/2024]
Abstract
Presynaptic α2-adrenoceptors are localized on axon terminals of many noradrenergic and non-noradrenergic neurons in the peripheral and central nervous systems. Their activation by exogenous agonists leads to inhibition of the exocytotic release of noradrenaline and other transmitters from the neurons. Most often, the α2A-receptor subtype is involved in this inhibition. The chain of molecular events between receptor occupation and inhibition of the exocytotic release of transmitters has been determined. Physiologically released endogenous noradrenaline elicits retrograde autoinhibition of its own release. Some clonidine-like α2-receptor agonists have been used to treat hypertension. Dexmedetomidine is used for prolonged sedation in the intensive care; It also has a strong analgesic effect. The α2-receptor antagonist mirtazapine increases the noradrenaline concentration in the synaptic cleft by interrupting physiological autoinhibion of release. It belongs to the most effective antidepressive drugs. β2-Adrenoceptors are also localized on axon terminals in the peripheral and central nervous systems. Their activation leads to enhanced transmitter release, however, they are not activated by endogenous adrenaline.
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Affiliation(s)
- Bela Szabo
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany.
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2
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Wang X, Zhang R, Chen B, Zhang T, Jin X, Gao P. Preliminary evaluation of the efficacy and safety of brimonidine for deep sedation. Fundam Clin Pharmacol 2024; 38:139-151. [PMID: 37612481 DOI: 10.1111/fcp.12944] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 05/16/2023] [Accepted: 07/20/2023] [Indexed: 08/25/2023]
Abstract
BACKGROUND Although brimonidine is currently used in the clinical treatment of glaucoma and rosacea, research of the deep sedative effect on animals after systemic administration is reported firstly and has shown promising results. METHODS The median effective dose (ED50 ), the median lethal dose (LD50 ), and the therapeutic index of brimonidine for deep sedation and formalin stimulation assay were determined by various animal experiments. The effect of synergistic anesthesia in rabbits with brimonidine and chloral hydrate was preliminarily evaluated. RESULTS The ED50 of brimonidine for highly effective sedation by intraperitoneal injection in rats was calculated to be 2.05 mg kg-1 with a 95% confidence interval (CI) of 1.87 to 2.25 mg kg-1 . The ED50 of brimonidine for deep sedation by intravenous and intrarectal injection in rabbits was calculated to be 0.087 mg kg-1 with a 95% CI of 0.084 to 0.091 mg kg-1 and 1.65 mg kg-1 with a 95% CI of 1.43 to 1.91 mg kg-1 , respectively. The LD50 of intraperitoneal brimonidine injection in rats was calculated to be 468 mg kg-1 with a 95% CI of 441 to 497 mg kg-1 and a therapeutic index of 228. Brimonidine has a certain analgesic and heart rate lowering effects. CONCLUSION The results confirmed that brimonidine has deep sedation and analgesic effects after systemic administration and has high safety. It can be used in combination with other types of sedative drugs to achieve better effects.
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Affiliation(s)
- Xiaohui Wang
- Laboratory of Traditional Chinese Medicine Preparations, Tianjin Institute of Medical & Pharmaceutical Sciences, Tianjin, China
| | - Rui Zhang
- School of Pharmaceutical Science and Technology, Tianjin University, Tianjin, China
| | - Bin Chen
- Laboratory of Medical Biomaterials, Tianjin Institute of Medical & Pharmaceutical Sciences, Tianjin, China
| | - Ting Zhang
- Pharmacokinetics Laboratory, Tianjin Institute of Medical & Pharmaceutical Sciences, Tianjin, China
| | - Xinghua Jin
- School of Pharmaceutical Science and Technology, Tianjin University, Tianjin, China
| | - Ping Gao
- Laboratory of Medical Biomaterials, Tianjin Institute of Medical & Pharmaceutical Sciences, Tianjin, China
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3
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Huang Y, Chen H, Chen SR, Pan HL. Duloxetine and Amitriptyline Reduce Neuropathic Pain by Inhibiting Primary Sensory Input to Spinal Dorsal Horn Neurons via α1- and α2-Adrenergic Receptors. ACS Chem Neurosci 2023; 14:1261-1277. [PMID: 36930958 DOI: 10.1021/acschemneuro.2c00780] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/19/2023] Open
Abstract
Antidepressants, such as duloxetine and amitriptyline, are effective for treating patients with chronic neuropathic pain. Inhibiting norepinephrine and serotonin transporters at presynaptic terminals raises extracellular concentrations of norepinephrine. The α1- and α2-adrenergic receptor agonists inhibit glutamatergic input from primary afferent nerves to the spinal dorsal horn. However, the contribution of spinal α1- and α2-adrenergic receptors to the analgesic effect of antidepressants and associated synaptic plasticity remains uncertain. In this study, we showed that systemic administration of duloxetine or amitriptyline acutely reduced tactile allodynia and mechanical and thermal hyperalgesia caused by spinal nerve ligation in rats. In contrast, duloxetine or amitriptyline had no effect on nociception in sham rats. Blocking α1-adrenergic receptors with WB-4101 or α2-adrenergic receptors with yohimbine at the spinal level diminished the analgesic effect of systemically administered duloxetine and amitriptyline. Furthermore, intrathecal injection of duloxetine or amitriptyline similarly attenuated pain hypersensitivity in nerve-injured rats; the analgesic effect was abolished by intrathecal pretreatment with both WB-4101 and yohimbine. In addition, whole-cell patch-clamp recordings in spinal cord slices showed that duloxetine or amitriptyline rapidly inhibited dorsal root-evoked excitatory postsynaptic currents in dorsal horn neurons in nerve-injured rats but had no such effect in sham rats. The inhibitory effect of duloxetine and amitriptyline was abolished by the WB-4101 and yohimbine combination. Therefore, antidepressants attenuate neuropathic pain predominantly by inhibiting primary afferent input to the spinal cord via activating both α1- and α2-adrenergic receptors. This information helps the design of new strategies to improve the treatment of neuropathic pain.
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Affiliation(s)
- Yuying Huang
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, United States
| | - Hong Chen
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, United States
| | - Shao-Rui Chen
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, United States
| | - Hui-Lin Pan
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, United States
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4
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Song FH, Liu DQ, Zhou YQ, Mei W. SIRT1: A promising therapeutic target for chronic pain. CNS Neurosci Ther 2022; 28:818-828. [PMID: 35396903 PMCID: PMC9062570 DOI: 10.1111/cns.13838] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 03/12/2022] [Accepted: 03/30/2022] [Indexed: 12/14/2022] Open
Abstract
Chronic pain remains an unresolved problem. Current treatments have limited efficacy. Thus, novel therapeutic targets are urgently required for the development of more effective analgesics. An increasing number of studies have proved that sirtuin 1 (SIRT1) agonists can relieve chronic pain. In this review, we summarize recent progress in understanding the roles and mechanisms of SIRT1 in mediating chronic pain associated with peripheral nerve injury, chemotherapy‐induced peripheral neuropathy, spinal cord injury, bone cancer, and complete Freund's adjuvant injection. Emerging studies have indicated that SIRT1 activation may exert positive effects on chronic pain relief by regulating inflammation, oxidative stress, and mitochondrial dysfunction. Therefore, SIRT1 agonists may serve as potential therapeutic drugs for chronic pain.
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Affiliation(s)
- Fan-He Song
- Anesthesiology Institute, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.,Department of Anesthesiology and Pain Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Dai-Qiang Liu
- Anesthesiology Institute, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.,Department of Anesthesiology and Pain Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Ya-Qun Zhou
- Anesthesiology Institute, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.,Department of Anesthesiology and Pain Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Wei Mei
- Anesthesiology Institute, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.,Department of Anesthesiology and Pain Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
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5
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Kearns A, Jayasi J, Liu X, Wang J, Shi Y, Chung JM, La JH, Tang SJ, Bae C. Neuron Type-Dependent Synaptic Activity in the Spinal Dorsal Horn of Opioid-Induced Hyperalgesia Mouse Model. Front Synaptic Neurosci 2021; 13:748929. [PMID: 34867259 PMCID: PMC8637419 DOI: 10.3389/fnsyn.2021.748929] [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: 07/28/2021] [Accepted: 10/26/2021] [Indexed: 11/26/2022] Open
Abstract
Opioids are widely used for pain relief; however, chronic opioid use causes a paradoxical state of enhanced pain sensitivity, termed “Opioid-induced hyperalgesia (OIH).” Despite the clinical importance of OIH, the detailed mechanism by which it enhances pain sensitivity remains unclear. In this study, we tested whether repeated morphine induces a neuronal circuit polarization in the mouse spinal dorsal horn (SDH). Transgenic mice expressing GFP to neurokinin 1 receptor-expressing neurons (sNK1Rn) and GABAergic interneurons (sGABAn) that received morphine [20 mg/kg, once daily for four consecutive days (i.p.)] developed mechanical hypersensitivity. Repeated morphine altered synaptic strengths in the SDH as a specific cell-type but not in a gender-dependent manner. In sNK1Rn and non-tonic firing neurons, repeated morphine treatment significantly increased frequency of spontaneous excitatory postsynaptic current (sEPSC) and evoked EPSC (eEPSC). In addition, repeated morphine treatment significantly decreased evoked inhibitory postsynaptic current (eIPSC) in sNK1Rn. Conversely, in sGABAn and tonic firing neurons, repeated morphine treatment significantly decreased sEPSC frequency and eEPSC, but had no change of eIPSC in sGABAn. Interestingly, repeated morphine treatment significantly decreased neuronal rheobase of sNK1Rn but had no effect on sGABAn. These findings suggest that spinal neuronal circuit polarization maybe the mechanism of OIH and identify a potential therapeutic mechanism to prevent or treat opioid-induced pain.
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Affiliation(s)
- Austin Kearns
- School of Electrical, Computer, and Biomedical Engineering, Southern Illinois University, Carbondale, IL, United States
| | - Jazmine Jayasi
- School of Electrical, Computer, and Biomedical Engineering, Southern Illinois University, Carbondale, IL, United States
| | - Xin Liu
- Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX, United States
| | - Jigong Wang
- Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX, United States
| | - Yuqiang Shi
- Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX, United States
| | - Jin Mo Chung
- Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX, United States
| | - Jun-Ho La
- Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX, United States
| | - Shao-Jun Tang
- Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX, United States
| | - Chilman Bae
- School of Electrical, Computer, and Biomedical Engineering, Southern Illinois University, Carbondale, IL, United States.,Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX, United States
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6
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Bin C, Xiaohui W, Mengrou S, Xin L, Ting Z, Ping G. Preliminary evaluation of the efficacy and safety of brimonidine for general anesthesia. BMC Anesthesiol 2021; 21:305. [PMID: 34861822 PMCID: PMC8641169 DOI: 10.1186/s12871-021-01516-1] [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: 08/02/2021] [Accepted: 11/08/2021] [Indexed: 12/04/2022] Open
Abstract
Background To determine the hypnotic and analgesic effects of brimonidine, and evaluate its efficacy and safety for general anesthesia. Potentiation of pentobarbital sleeping time following brimonidine administration was observed in mice, as was the analgesic activity of brimonidine. Methods The median effective dose (ED50) and lethal dose (LD50) of intraperitoneally injected brimonidine were determined in hypnotized mice. In addition, the LD50 of intravenously injected brimonidine, and ED50 of intravenously, intramuscularly, and intrarectally injected brimonidine in hypnotized rabbits were determined. Finally, the synergistic anesthetic effect of brimonidine and chloral hydrate was evaluated in rabbits. Results Intraperitoneal injection of 10 mg/kg brimonidine enhanced the hypnotic effect of a threshold dose of pentobarbital. Intraperitoneally injected brimonidine produced dose-related analgesic effects in mice. The ED50 of intraperitoneally administered brimonidine in hypnotized mice was 75.7 mg/kg and the LD50 was 379 mg/kg. ED50 values of intravenous, intramuscular, and intrarectal brimonidine for hypnosis in rabbits were 5.2 mg/kg, 8.8 mg/kg, and 8.7 mg/kg, respectively; the LD50 of intravenous brimonidine was 146 mg/kg. Combined intravenous administration of 0.6 mg/kg brimonidine and 0.03 g/kg chloral hydrate had a synergistic anesthetic effect. Conclusions Brimonidine elicited hypnotic and analgesic effects after systemic administration and exhibited safety. Moreover, brimonidine enhanced the effects of other types of narcotics when combined. Supplementary Information The online version contains supplementary material available at 10.1186/s12871-021-01516-1.
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Affiliation(s)
- Chen Bin
- Tianjin Institute of Medical & Pharmaceutical Sciences, No. 79 Duolun Road, Heping District, Tianjin, 300020, China
| | - Wang Xiaohui
- Tianjin Institute of Medical & Pharmaceutical Sciences, No. 79 Duolun Road, Heping District, Tianjin, 300020, China
| | - Shi Mengrou
- Tianjin Institute of Medical & Pharmaceutical Sciences, No. 79 Duolun Road, Heping District, Tianjin, 300020, China
| | - Li Xin
- Tianjin Institute of Medical & Pharmaceutical Sciences, No. 79 Duolun Road, Heping District, Tianjin, 300020, China
| | - Zhang Ting
- Tianjin Institute of Medical & Pharmaceutical Sciences, No. 79 Duolun Road, Heping District, Tianjin, 300020, China
| | - Gao Ping
- Tianjin Institute of Medical & Pharmaceutical Sciences, No. 79 Duolun Road, Heping District, Tianjin, 300020, China.
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7
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Vicente-Baz J, Lopez-Garcia JA, Rivera-Arconada I. Central sensitization of dorsal root potentials and dorsal root reflexes: An in vitro study in the mouse spinal cord. Eur J Pain 2021; 26:356-369. [PMID: 34587321 DOI: 10.1002/ejp.1864] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND Axo-axonic contacts onto central terminals of primary afferents modulate sensory inputs to the spinal cord. These contacts produce primary afferent depolarization (PAD), which serves as a mechanism for presynaptic inhibition, and also produce dorsal root reflexes (DRRs), which may regulate the excitability of peripheral terminals and second order neurons. We aimed to identify changes in these responses as a consequence of peripheral inflammation. METHODS In vitro spinal cord recordings of spontaneous activities in dorsal and ventral roots were performed in control mice and following paw inflammation. We also used pharmacological assays to define the neurotransmitter systems implicated in such responses. RESULTS Paw inflammation increased the frequency and amplitude of spontaneous dorsal root depolarizations, the occurrence of DRRs and the amplitude of ventral roots depolarizations. PAD was classified in two different patterns based on their relation to ventral activity: time-locked and independent events. Both patterns increased in amplitude after paw inflammation, and independent events also increased in frequency. The circuits that were responsible for this activity implicated both glutamatergic and GABAergic transmission. Adrenergic modulation differentially affected both types of PAD, and this modulation changed after paw inflammation. CONCLUSIONS Our findings suggest the existence of independent spinal circuits at the origin of PAD and DRRs. Inflammation modulates these circuits differentially, unveiling varied mechanisms of spinal sensitization. This in vitro approach provides an isolated model for the study of the mechanisms of central sensitization and for the performance of pharmacological assays with the purpose of identifying and testing novel antinociceptive targets. SIGNIFICANCE Spinal circuits modulate activity of primary afferents acting on central terminals. Under in vitro conditions, dorsal roots show spontaneous activity in the form of depolarizations and action potentials. Our findings are consistent with the existence of several independent generator circuits. Experimental paw inflammation reduced mechanical withdrawal threshold and significantly increased the spontaneous activity of dorsal roots, which may be secondary to an enhanced output of spinal generators. This can be considered as a novel sign of central sensitization.
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Affiliation(s)
- Jorge Vicente-Baz
- Department of Systems Biology (Physiology), Universidad de Alcala, Alcala de Henares, Madrid, Spain
| | | | - Ivan Rivera-Arconada
- Department of Systems Biology (Physiology), Universidad de Alcala, Alcala de Henares, Madrid, Spain
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8
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Takemura M, Niki K, Okamoto Y, Matsuda Y, Omae T, Takagi T, Ueda M. Tapentadol in Cancer Patients with Neuropathic Pain: A Comparison of Methadone, Oxycodone, Fentanyl, and Hydromorphone. Biol Pharm Bull 2021; 44:1286-1293. [PMID: 34471056 DOI: 10.1248/bpb.b21-00212] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Tapentadol has μ-opioid receptor stimulating and noradrenaline reuptake inhibiting properties, and should be effective for neuropathic pain (NP). However, the efficacy of tapentadol for NP in cancer patients is unclear. Ashiya Municipal Hospital (Hyogo, Japan) enrolled five groups of Japanese cancer patients between January 1, 2013, and December 31, 2019. Patients with NP were administered tapentadol (n = 29), methadone (n = 32), oxycodone (n = 20), fentanyl (n = 26), or hydromorphone (n = 20). The primary endpoint was the difference in the verbal rating scale (VRS) scores between days 0 and 7. The secondary endpoint was the tolerability of each opioid. Before administering opioids among the five groups, there was no significant difference in the VRS score (p = 0.99). The mean reduction in the VRS score on day 7 was significantly greater in the tapentadol group than in the oxycodone group (p = 0.0024) and was larger than that of the methadone, fentanyl, and hydromorphone groups. Regarding safety, the discontinuation rate in the tapentadol group was the lowest of all groups (tapentadol vs. methadone vs. oxycodone vs. fentanyl vs. hydromorphone, 0.0% vs. 6.3% vs. 5.0% vs. 3.8% vs. 10.0%, respectively). This study suggests that tapentadol could be efficacious for cancer patients with NP, and a preferred option in cases that require immediate dose adjustment or for those at high risk for adverse effects. However, the pain intensity was evaluated without pain assessment scales specific to NP. Thus, we think that it is desirable to validate our findings using assessment scales, such as the painDETECT questionnaire in future.
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Affiliation(s)
- Miho Takemura
- Department of Clinical Pharmacy Research and Education, Osaka University Graduate School of Pharmaceutical Sciences
| | - Kazuyuki Niki
- Department of Clinical Pharmacy Research and Education, Osaka University Graduate School of Pharmaceutical Sciences.,Department of Pharmacy, Ashiya Municipal Hospital
| | | | | | - Takahito Omae
- Department of Palliative Care, Ashiya Municipal Hospital
| | - Tatsuya Takagi
- Department of Pharmainformatics and Pharmacometrics, Osaka University Graduate School of Pharmaceutical Sciences
| | - Mikiko Ueda
- Department of Clinical Pharmacy Research and Education, Osaka University Graduate School of Pharmaceutical Sciences
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9
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Chia JSM, Izham NAM, Farouk AAO, Sulaiman MR, Mustafa S, Hutchinson MR, Perimal EK. Zerumbone Modulates α 2A-Adrenergic, TRPV1, and NMDA NR2B Receptors Plasticity in CCI-Induced Neuropathic Pain In Vivo and LPS-Induced SH-SY5Y Neuroblastoma In Vitro Models. Front Pharmacol 2020; 11:92. [PMID: 32194397 PMCID: PMC7064019 DOI: 10.3389/fphar.2020.00092] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Accepted: 01/27/2020] [Indexed: 01/08/2023] Open
Abstract
Zerumbone has shown great potential in various pathophysiological models of diseases, particularly in neuropathic pain conditions. Further understanding the mechanisms of action is important to develop zerumbone as a potential anti-nociceptive agent. Numerous receptors and pathways function to inhibit and modulate transmission of pain signals. Previously, we demonstrated involvement of the serotonergic system in zerumbone's anti-neuropathic effects. The present study was conducted to determine zerumbone's modulatory potential involving noradrenergic, transient receptor potential vanilloid type 1 (TRPV1) and N-methyl-D-aspartate (NMDA) receptors in chronic constriction injury (CCI)-induced in vitro and lipopolysaccharide (LPS)-induced SH-SY5Y in vitro neuroinflammatory models. von Frey filament and Hargreaves plantar tests were used to assess allodynia and hyperalgesia in the chronic constriction injury-induced neuropathic pain mouse model. Involvement of specific adrenoceptors were investigated using antagonists- prazosin (α1-adrenoceptor antagonist), idazoxan (α2-adrenoceptor antagonist), metoprolol (β1-adrenoceptor antagonist), ICI 118,551 (β2-adrenoceptor antagonist), and SR 59230 A (β3-adrenoceptor antagonist), co-administered with zerumbone (10 mg/kg). Involvement of excitatory receptors; TRPV and NMDA were conducted using antagonists capsazepine (TRPV1 antagonist) and memantine (NMDA antagonist). Western blot was conducted to investigate the effect of zerumbone on the expression of α2A-adrenoceptor, TRPV1 and NMDA NR2B receptors in CCI-induced whole brain samples of mice as well as in LPS-induced SH-SY5Y neuroblastoma cells. Pre-treatment with α1- and α2-adrenoceptor antagonists significantly attenuated both anti-allodynic and anti-hyperalgesic effects of zerumbone. For β-adrenoceptors, only β2-adrenoceptor antagonist significantly reversed the anti-allodynic and anti-hyperalgesic effects of zerumbone. β1-adrenoceptor antagonist only reversed the anti-allodynic effect of zerumbone. The anti-allodynic and anti-hyperalgesic effects of zerumbone were both absent when TRPV1 and NMDA receptors were antagonized in both nociceptive assays. Zerumbone treatment markedly decreased the expression of α2A-adrenoceptor, while an up-regulation was observed of NMDA NR2B receptors. Expression of TRPV1 receptors however did not significantly change. The in vitro study, representing a peripheral model, demonstrated the reduction of both NMDA NR2B and TRPV1 receptors while significantly increasing α2A-adrenoceptor expression in contrast to the brain samples. Our current findings suggest that the α1-, α2-, β1- and β2-adrenoceptors, TRPV1 and NMDA NR2B are essential for the anti-allodynic and antihyperalgesic effects of zerumbone. Alternatively, we demonstrated the plasticity of these receptors through their response to zerumbone's administration.
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Affiliation(s)
- Jasmine Siew Min Chia
- Department of Biomedical Science, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang, Malaysia.,Centre for Community Health Studies, Faculty of Health Sciences, Universiti Kebangsaan Malaysia, Kuala Lumpur, Malaysia
| | - Noor Aishah Mohammed Izham
- Department of Biomedical Science, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang, Malaysia
| | - Ahmad Akira Omar Farouk
- Department of Biomedical Science, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang, Malaysia
| | - Mohd Roslan Sulaiman
- Department of Biomedical Science, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang, Malaysia
| | - Sanam Mustafa
- Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, SA, Australia
| | - Mark R Hutchinson
- Australian Research Council Centre of Excellence for Nanoscale BioPhotonics, University of Adelaide, Adelaide, SA, Australia
| | - Enoch Kumar Perimal
- Department of Biomedical Science, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang, Malaysia.,Australian Research Council Centre of Excellence for Nanoscale BioPhotonics, University of Adelaide, Adelaide, SA, Australia
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10
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Lyu C, Lyu GW, Mulder J, Martinez A, Shi TJS. G Protein-Gated Inwardly Rectifying Potassium Channel Subunit 3 is Upregulated in Rat DRGs and Spinal Cord After Peripheral Nerve Injury. J Pain Res 2020; 13:419-429. [PMID: 32110090 PMCID: PMC7034995 DOI: 10.2147/jpr.s233744] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Accepted: 01/28/2020] [Indexed: 12/15/2022] Open
Abstract
Background G protein-gated inwardly rectifying potassium (GIRK) channels are involved in the regulation of neuronal excitability. Four GIRK subunits (GIRK1-4) are expressed in rat dorsal root ganglia (DRGs). Recently, we have characterized the expression of GIRK1 and −2, and both are downregulated in rat DRGs and spinal cord after a complete sciatic nerve transection (axotomy). Here, we aimed to study the neurochemical characteristics of GIRK3, and its regulation in rat DRGs and spinal cord induced by nerve injury. Methods A sciatic nerve axotomy was performed to study the influences of injury on GIRK3 expression in DRGs and spinal cord. A dorsal root rhizotomy and a sciatic nerve crush were employed to study the axonal transport of GIRK3 protein, respectively. Immunohistochemistry analysis was employed for investigating the neurochemical characteristics of GIRK3. Results In control DRGs, ~18% of neuron profiles (NPs) were GIRK3-positive (+), and ~41%, ~48% and ~45% of GIRK3+ NPs were CGRP+, IB4+ and NF200+, respectively. GIRK3-like immunoreactivity was observed in glabrous skin of hind paws and axons originating from DRG neurons. Fourteen days after axotomy, more than one-third of DRG NPs were GIRK3+, and among these ~51% and ~56% coexpressed galanin and neuropeptide Y, respectively. In control animals, a small group of interneurons found in the dorsal horn was GIRK3+. In addition, GIRK3+ processes could be observed in superficial laminae of spinal dorsal horn. After nerve injury, the intensity of GIRK3-like immunoreactivity in the superficial layers was increased. Evidence based on rhizotomy and sciatic nerve crush indicated both anterograde and retrograde transport of GIRK3. Conclusion Our study demonstrates that GIRK3 is expressed in sensory neurons and spinal cord. GIRK3 has both anterograde and retrograde axonal transport. GIRK3 expression can be regulated by peripheral nerve injury.
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Affiliation(s)
- Chuang Lyu
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin 150069, People's Republic of China
| | - Gong-Wei Lyu
- Department of Neurology, 1st Hospital of Harbin Medical University, Harbin 150001, People's Republic of China
| | - Jan Mulder
- Department of Neuroscience, Karolinska Institutet, Stockholm SE-171 77, Sweden.,Science for Life Laboratory, Karolinska Institutet, Stockholm SE-171 65, Sweden
| | - Aurora Martinez
- Department of Biomedicine, University of Bergen, Bergen 5009, Norway
| | - Tie-Jun Sten Shi
- Department of Biomedicine, University of Bergen, Bergen 5009, Norway
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11
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Caraci F, Merlo S, Drago F, Caruso G, Parenti C, Sortino MA. Rescue of Noradrenergic System as a Novel Pharmacological Strategy in the Treatment of Chronic Pain: Focus on Microglia Activation. Front Pharmacol 2019; 10:1024. [PMID: 31572196 PMCID: PMC6751320 DOI: 10.3389/fphar.2019.01024] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2019] [Accepted: 08/12/2019] [Indexed: 12/11/2022] Open
Abstract
Different types of pain can evolve toward a chronic condition characterized by hyperalgesia and allodynia, with an abnormal response to normal or even innocuous stimuli, respectively. A key role in endogenous analgesia is recognized to descending noradrenergic pathways that originate from the locus coeruleus and project to the dorsal horn of the spinal cord. Impairment of this system is associated with pain chronicization. More recently, activation of glial cells, in particular microglia, toward a pro-inflammatory state has also been implicated in the transition from acute to chronic pain. Both α2- and β2-adrenergic receptors are expressed in microglia, and their activation leads to acquisition of an anti-inflammatory phenotype. This review analyses in more detail the interconnection between descending noradrenergic system and neuroinflammation, focusing on drugs that, by rescuing the noradrenergic control, exert also an anti-inflammatory effect, ultimately leading to analgesia. More specifically, the potential efficacy in the treatment of neuropathic pain of different drugs will be analyzed. On one side, drugs acting as inhibitors of the reuptake of serotonin and noradrenaline, such as duloxetine and venlafaxine, and on the other, tapentadol, inhibitor of the reuptake of noradrenaline, and agonist of the µ-opioid receptor.
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Affiliation(s)
- Filippo Caraci
- Department of Drug Sciences, Section of Pharmacology and Toxicology, University of Catania, Catania, Italy.,Oasi Research Institute-IRCCS, Troina, Italy
| | - Sara Merlo
- Department of Biomedical and Biotechnological Sciences, Section of Pharmacology, University of Catania, Catania, Italy
| | - Filippo Drago
- Department of Biomedical and Biotechnological Sciences, Section of Pharmacology, University of Catania, Catania, Italy
| | | | - Carmela Parenti
- Department of Drug Sciences, Section of Pharmacology and Toxicology, University of Catania, Catania, Italy
| | - Maria Angela Sortino
- Department of Biomedical and Biotechnological Sciences, Section of Pharmacology, University of Catania, Catania, Italy
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12
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Chen SR, Zhang J, Chen H, Pan HL. Streptozotocin-Induced Diabetic Neuropathic Pain Is Associated with Potentiated Calcium-Permeable AMPA Receptor Activity in the Spinal Cord. J Pharmacol Exp Ther 2019; 371:242-249. [PMID: 31481518 DOI: 10.1124/jpet.119.261339] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 08/20/2019] [Indexed: 12/22/2022] Open
Abstract
Neuronal hyperactivity in the spinal dorsal horn can amplify nociceptive input in diabetic neuropathic pain. The glutamate N-methyl-d-aspartate and α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors (NMDA receptors and AMPA receptors, respectively) are involved in spinal nociceptive transmission. It is unclear, however, whether painful diabetic neuropathy is associated with changes in the activity of synaptic NMDA receptors and AMPA receptors in spinal dorsal horn neurons. AMPA receptors lacking GluA2 are Ca2+-permeable (CP-AMPA receptors), and their currents display characteristic inward rectification. In this study, we showed that evoked excitatory postsynaptic currents (EPSCs), induced by streptozotocin, exhibited inward rectification in spinal dorsal neurons in diabetic rats. Presynaptic and postsynaptic NMDA receptor activity in the spinal dorsal horn was similar in diabetic and control rats. In the dorsal spinal cord, the membrane GluA2 protein level was significantly lower in diabetic than in control rats, whereas the cytosolic GluA2 level was greater in diabetic than in control rats. In contrast, the GluA1 subunit levels in the plasma membrane and cytosol did not differ between the two groups. Blocking CP-AMPA receptors significantly reduced the amplitude of EPSCs of dorsal horn neurons in diabetic but not in control rats. Furthermore, blocking spinal CP-AMPA receptors reduced pain hypersensitivity in diabetic rats but had no effect on nociception in control rats. Our study suggests that diabetic neuropathy augments CP-AMPA receptor activity in the spinal dorsal horn by causing intracellular retention of GluA2 and impairing GluA2 membrane trafficking. Increased prevalence of spinal CP-AMPA receptors sustains diabetic neuropathic pain. SIGNIFICANCE STATEMENT: This study demonstrates that the prevalence of synaptic calcium-permeable AMPA receptors is increased in the spinal dorsal horn, which mediates pain hypersensitivity in diabetic neuropathy. Thus, calcium-permeable AMPA receptors play an important role in glutamatergic synaptic plasticity in the spinal cord in painful diabetic neuropathy. This new knowledge improves our understanding of the mechanisms involved in central sensitization associated with diabetic neuropathic pain and suggests that calcium-permeable AMPA receptors are an alternative therapeutic target for treating this chronic pain condition.
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Affiliation(s)
- Shao-Rui Chen
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Jixiang Zhang
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Hong Chen
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Hui-Lin Pan
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas
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13
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Ganugula R, Deng M, Arora M, Pan HL, Kumar MNVR. Polyester Nanoparticle Encapsulation Mitigates Paclitaxel-Induced Peripheral Neuropathy. ACS Chem Neurosci 2019; 10:1801-1812. [PMID: 30609902 DOI: 10.1021/acschemneuro.8b00703] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Chemotherapy utilizing cytotoxic drugs, such as paclitaxel (PTX), is still a commonly used therapeutic approach to treat both localized and metastasized cancers. Unlike traditional regimens in which PTX is administered at the maximum tolerated dose, alternative regimens like metronomic dosing are beneficial by administering PTX more frequently and in much lower doses exploiting antiangiogenic and immunomodulatory effects. However, PTX-induced peripheral neuropathy and lack of patient compliant dosage forms of PTX are major roadblocks for the successful implementation of metronomic regimens. Because of the success of polyester nanoparticle drug delivery, we explored the potential of nanoparticle-encapsulated paclitaxel (nPTX) in alleviating peripheral neuropathy using a rat model. Rats were injected intraperitoneally with 2 mg/kg body weight of PTX or nPTX on four alternate days, and neuropathic pain and neuronal damage were characterized using behavioral assessments, histology, and immunohistochemistry. The reduction in tactile and nociceptive pressure thresholds was significantly less in nPTX-treated rats than in PTX-treated rats over a 16-day study period. Histological analysis showed that the degree of dorsal root ganglion (DRG) degeneration and reduction in motor neurons in the spinal cord was significantly lower in the nPTX group than the PTX group. Further, immunofluorescence data reveals that nPTX-treated rats had an increased density of a neuronal marker, β-tubulin-III, reduced TUNEL positive cells, and increased high molecular weight neurofilament in the spinal cord, DRG, and sciatic nerves compared with PTX-treated rats. Therefore, this work has important implications in improving risk-benefit profile of PTX, paving the way for metronomic regimens.
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Affiliation(s)
- R. Ganugula
- Department of Pharmaceutical Sciences, College of Pharmacy, Texas A&M University, Reynolds Medical Building, TAMU Mail Stop 1114, College Station, Texas 77843, United States
| | - M. Deng
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, United States
| | - M. Arora
- Department of Pharmaceutical Sciences, College of Pharmacy, Texas A&M University, Reynolds Medical Building, TAMU Mail Stop 1114, College Station, Texas 77843, United States
| | - H.-L. Pan
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, United States
| | - M. N. V. Ravi Kumar
- Department of Pharmaceutical Sciences, College of Pharmacy, Texas A&M University, Reynolds Medical Building, TAMU Mail Stop 1114, College Station, Texas 77843, United States
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14
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Bahari Z, Meftahi GH. Spinal α 2 -adrenoceptors and neuropathic pain modulation; therapeutic target. Br J Pharmacol 2019; 176:2366-2381. [PMID: 30657594 DOI: 10.1111/bph.14580] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Revised: 11/23/2018] [Accepted: 12/04/2018] [Indexed: 12/22/2022] Open
Abstract
Neuropathic pain can arise from disease or damage to the nervous system. The most common symptoms of neuropathic pain include spontaneous pain, allodynia, and hyperalgesia. There is still limited knowledge about the factors that initiate and maintain neuropathic pain. However, ample evidence has proved the antinociceptive role of spinal α-adrenoceptors following nerve injury. It is well-documented that noradrenergic descending pathways from supraspinal loci exert an inhibitory influence on the spinal cord nociceptive neurons, mostly through the activation of spinal α2 -adrenoceptors. This, in turn, suppresses transmission of pain input and the hyperexcitability of spinal dorsal horn neurons. There is considerable evidence demonstrating that spinal application of α2 -adrenoceptor agonists leads to analgesic effects in animal models of neuropathic pain. Today, despite the recent rapid development of neuroscience and drug discovery, effective drugs with clear basic mechanisms have remained a mystery. Here, we give an overview of the cellular mechanisms through which brainstem adrenergic descending inhibitory processing can alter spinal pain transmission to the higher centres, and how these pathways change in neuropathic pain conditions focusing on the role of spinal α2 -adrenoceptors in the spinal dorsal horn. We then suggest that α2 -adrenoceptor agonist may be useful to treat neuropathic pain. LINKED ARTICLES: This article is part of a themed section on Adrenoceptors-New Roles for Old Players. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.14/issuetoc.
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Affiliation(s)
- Zahra Bahari
- Neuroscience Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran.,Department of Physiology and Medical Physics, Faculty of Medicine, Baqiyatallah University of Medical Sciences, Tehran, Iran
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15
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Caputi FF, Nicora M, Simeone R, Candeletti S, Romualdi P. Tapentadol: an analgesic that differs from classic opioids due to its noradrenergic mechanism of action. Minerva Med 2019; 110:62-78. [PMID: 30667206 DOI: 10.23736/s0026-4806.18.05909-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Chronic pain treatment represents one of the most complex clinical challenges and even though opioids exhibit particular efficacy on nociceptive pain, their use must be controlled to avoid the risk of adverse reactions. A useful approach, aimed at maintaining analgesia and mitigating side effects, is represented by the use of a new class of analgesics endowed of µ-opioid (MOR) receptor agonism and noradrenaline reuptake inhibition (NRI) mechanisms. Tapentadol is the progenitor of this new class of drugs called MOP-NRI. A literature review has been conducted to gain information about the efficacy and the tolerability profile of tapentadol shifting from MOR agonism (acute pain) to NRI activity (chronic pain). The tolerability and therapeutic safety of tapentadol in neuropathic pain models, as well as in clinical settings, has been analyzed showing a good gastrointestinal tolerability profile, a moderate effect on hormone levels (in healthy volunteers and in patients) and on cognitive performance, a lack of significant alteration of the electrocardiogram recording and no changes of the QT/QTc interval, a minimal effect on serotonin reuptake in vivo with a low risk of serotonin syndrome, a longer time for the onset of analgesic tolerance and a less occurrence of abuse liability compared to formulations containing other comparator compounds. Tapentadol represents a great innovation in chronic pain therapy with a unique analgesic profile different form classical opioids, therefore, thanks to its synergistic MOR-NRI action, it may be a good option for the treatment of chronic, neuropathic and mixed pain.
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Affiliation(s)
- Francesca F Caputi
- Department of Pharmacy and Biotechnology, Alma Mater Studiorum, University of Bologna, Bologna, Italy -
| | | | | | - Sanzio Candeletti
- Department of Pharmacy and Biotechnology, Alma Mater Studiorum, University of Bologna, Bologna, Italy
| | - Patrizia Romualdi
- Department of Pharmacy and Biotechnology, Alma Mater Studiorum, University of Bologna, Bologna, Italy
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16
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Sirtuin 1 alleviates diabetic neuropathic pain by regulating synaptic plasticity of spinal dorsal horn neurons. Pain 2019; 160:1082-1092. [DOI: 10.1097/j.pain.0000000000001489] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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17
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Zhao JY, Yang L, Bai HH, Liu JP, Suo ZW, Yang X, Hu XD. Inhibition of protein tyrosine phosphatase 1B in spinal cord dorsal horn of rats attenuated diabetic neuropathic pain. Eur J Pharmacol 2018. [DOI: 10.1016/j.ejphar.2018.03.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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18
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Opioid and noradrenergic contributions of tapentadol to the inhibition of locus coeruleus neurons in the streptozotocin rat model of polyneuropathic pain. Neuropharmacology 2018; 135:202-210. [PMID: 29551688 DOI: 10.1016/j.neuropharm.2018.03.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 03/12/2018] [Accepted: 03/14/2018] [Indexed: 12/23/2022]
Abstract
Tapentadol is an analgesic that acts as an agonist of µ opioid receptors (MOR) and that inhibits noradrenaline reuptake. Data from healthy rats show that tapentadol inhibits neuronal activity in the locus coeruleus (LC), a nucleus regulated by both the noradrenergic and opioid systems. Thus, we set out to investigate the effect of tapentadol on LC activity in streptozotocin (STZ)-induced diabetic rats, a model of diabetic polyneuropathy, by analyzing single-unit extracellular recordings of LC neurons. Four weeks after inducing diabetes, tapentadol dose-response curves were obtained from animals pre-treated with RX821002 or naloxone (alpha2-adrenoceptors and opioid receptors antagonists, respectively). In STZ rats, the spontaneous activity of LC neurons (0.9 ± 0.1 Hz) was lower than in naïve animals (1.5 ± 0.1 Hz), and tapentadol's inhibitory effect was also weaker. Alpha2-adrenoceptors blockade by RX821002 (100 μg/kg i.v.) in STZ animals significantly increased the spontaneous activity (from 0.8 ± 0.1 to 1.4 ± 0.2 Hz) and it dampened the inhibition of LC neurons produced by tapentadol. However, opioid receptors blockade following naloxone pre-treatment (5 mg/kg i.v.) did not alter the spontaneous firing rate (0.9 ± 0.2 vs 0.9 ± 0.2 Hz) or the inhibitory effect of tapentadol on LC neurons in STZ animals. Thus, diabetic polyneuropathy appears to exert neuroplastic changes in LC neurotransmission, enhancing the sensitivity of alpha2-adrenoceptors and dampening opioid receptors expression. Tapentadol's activity seems to be predominantly mediated through its noradrenergic effects rather than its influence on opioid receptors in the STZ model of diabetic polyneuropathy.
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19
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Xie JD, Chen SR, Pan HL. Presynaptic mGluR5 receptor controls glutamatergic input through protein kinase C-NMDA receptors in paclitaxel-induced neuropathic pain. J Biol Chem 2017; 292:20644-20654. [PMID: 29074619 DOI: 10.1074/jbc.m117.818476] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Revised: 10/13/2017] [Indexed: 12/22/2022] Open
Abstract
Chemotherapeutic drugs such as paclitaxel cause painful peripheral neuropathy in many cancer patients and survivors. Although NMDA receptors (NMDARs) at primary afferent terminals are known to be critically involved in chemotherapy-induced chronic pain, the upstream signaling mechanism that leads to presynaptic NMDAR activation is unclear. Group I metabotropic glutamate receptors (mGluRs) play a role in synaptic plasticity and NMDAR regulation. Here we report that the Group I mGluR agonist (S)-3,5-dihydroxyphenylglycine (DHPG) significantly increased the frequency of miniature excitatory postsynaptic currents (EPSCs) and the amplitude of monosynaptic EPSCs evoked from the dorsal root. DHPG also reduced the paired-pulse ratio of evoked EPSCs in spinal dorsal horn neurons. These effects were blocked by the selective mGluR5 antagonist 2-methyl-6-(phenylethynyl)-pyridine (MPEP), but not by an mGluR1 antagonist. MPEP normalized the frequency of miniature EPSCs and the amplitude of evoked EPSCs in paclitaxel-treated rats but had no effect in vehicle-treated rats. Furthermore, mGluR5 protein levels in the dorsal root ganglion and spinal cord synaptosomes were significantly higher in paclitaxel- than in vehicle-treated rats. Inhibiting protein kinase C (PKC) or blocking NMDARs abolished DHPG-induced increases in the miniature EPSC frequency of spinal dorsal horn neurons in vehicle- and paclitaxel-treated rats. Moreover, intrathecal administration of MPEP reversed pain hypersensitivity caused by paclitaxel treatment. Our findings suggest that paclitaxel-induced painful neuropathy is associated with increased presynaptic mGluR5 activity at the spinal cord level, which serves as upstream signaling for PKC-mediated tonic activation of NMDARs. mGluR5 is therefore a promising target for reducing chemotherapy-induced neuropathic pain.
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Affiliation(s)
- Jing-Dun Xie
- From the Department of Anesthesiology and Perioperative Medicine, Center for Neuroscience and Pain Research, The University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030 and.,the Department of Anesthesiology, Sun Yat-Sen University Cancer Center, Guangzhou, Guangdong 510060, China
| | - Shao-Rui Chen
- From the Department of Anesthesiology and Perioperative Medicine, Center for Neuroscience and Pain Research, The University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030 and
| | - Hui-Lin Pan
- From the Department of Anesthesiology and Perioperative Medicine, Center for Neuroscience and Pain Research, The University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030 and
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20
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Cao XC, Pappalardo LW, Waxman SG, Tan AM. Dendritic spine dysgenesis in superficial dorsal horn sensory neurons after spinal cord injury. Mol Pain 2017; 13:1744806916688016. [PMID: 28326929 PMCID: PMC5302173 DOI: 10.1177/1744806916688016] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Neuropathic pain is a major complication of spinal cord injury, and despite aggressive efforts, this type of pain is refractory to available clinical treatment. Our previous work has demonstrated a structure–function link between dendritic spine dysgenesis on nociceptive sensory neurons in the intermediate zone, laminae IV/V, and chronic pain in central nervous system and peripheral nervous system injury models of neuropathic pain. To extend these findings, we performed a follow-up structural analysis to assess whether dendritic spine remodeling occurs on superficial dorsal horn neurons located in lamina II after spinal cord injury. Lamina II neurons are responsible for relaying deep, delocalized, often thermally associated pain commonly experienced in spinal cord injury pathologies. We analyzed dendritic spine morphometry and localization in tissue obtained from adult rats exhibiting neuropathic pain one-month following spinal cord injury. Although the total density of dendritic spines on lamina II neurons did not change after spinal cord injury, we observed an inverse relationship between the densities of thin- and mushroom-shaped spines: thin-spine density decreased while mushroom-spine density increased. These structural changes were specifically noted along dendritic branches within 150 µm from the soma, suggesting a possible adverse contribution to nociceptive circuit function. Intrathecal treatment with NSC23766, a Rac1-GTPase inhibitor, significantly reduced spinal cord injury-induced changes in both thin- and mushroom-shaped dendritic spines. Overall, these observations demonstrate that dendritic spine remodeling occurs in lamina II, regulated in part by the Rac1-signaling pathway, and suggests that structural abnormalities in this spinal cord region may also contribute to abnormal nociception after spinal cord injury.
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Affiliation(s)
- Xiaoyu C Cao
- 1 Department of Neurology, Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, USA.,2 Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA
| | - Laura W Pappalardo
- 1 Department of Neurology, Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, USA.,2 Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA
| | - Stephen G Waxman
- 1 Department of Neurology, Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, USA.,2 Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA
| | - Andrew M Tan
- 1 Department of Neurology, Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, USA.,2 Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA
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21
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Chen H, Xu X, Yang XY, Ling BY, Sun HP, Liu C, Zhang YQ, Cao H, Xu L. Systemic dexmedetomidine attenuates mechanical allodynia through extracellular sign db type 2 diabetic mice. Neurosci Lett 2017; 657:126-133. [PMID: 28757391 DOI: 10.1016/j.neulet.2017.07.048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 07/23/2017] [Accepted: 07/26/2017] [Indexed: 10/19/2022]
Abstract
Painful diabetic neuropathy (PDN) is a common complication of diabetes mellitus. However, the treatment for PDN is limited in clinical practice. In the present study, we investigated the effect of systemic administration dexmedetomidine (DEX), a selective alpha 2 adrenergic receptor (α2AR) agonist, on mechanical allodynia and its underlying mechanism in db/db mice, an animal model of type 2 diabetes mellitus. Our data demonstrated that db/db mice develop mechanical allodynia at the early stage of diabetes. During the period of mechanical allodynia, we detected increased release of norepinephrine (NE) and decreased levels of α2A-Adrenoceptors in db/db mice. Immunohistochemistry showed that the α2A-Adrenoceptor is predominantly expressed in neurons in the spinal cord. Acute injection of dexmedetomidine significantly decreased mechanical allodynia, which was blocked by its selective antagonist BRL44408. Furthermore, the upregulation of pERK1 and pERK2 in db/db mice were attenuated by preadministration of dexmedetomidine. We provide the first evidence that the functional alternation of spinal noradrenergic system might underlie exaggerated nociception in PDN. Systemic dexmedetomidine inhibits the mechanical allodynia which is related to ERK signaling pathway in type 2 diabetes, implying that the α2-Adrenoceptor might be a potential therapeutic strategy for PDN.
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Affiliation(s)
- Hui Chen
- Department of Endocrinology, Wuxi People's Hospital, Nanjing Medical University, Wuxi, Jiangsu, 214023, China
| | - Xiang Xu
- Department of Endocrinology, Wuxi People's Hospital, Nanjing Medical University, Wuxi, Jiangsu, 214023, China
| | - Xiao-Yu Yang
- Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and Collaborative Innovation Center for Brain Science, Fudan University, 200032, China
| | - Bing-Yu Ling
- Department of Endocrinology, Wuxi People's Hospital, Nanjing Medical University, Wuxi, Jiangsu, 214023, China
| | - He-Ping Sun
- Department of Endocrinology, Wuxi People's Hospital, Nanjing Medical University, Wuxi, Jiangsu, 214023, China
| | - Chao Liu
- Department of Endocrinology, Wuxi People's Hospital, Nanjing Medical University, Wuxi, Jiangsu, 214023, China
| | - Yu Qiu Zhang
- Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and Collaborative Innovation Center for Brain Science, Fudan University, 200032, China; Institutes of Integrative Medicine, Fudan University, 200032, China
| | - Hong Cao
- Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and Collaborative Innovation Center for Brain Science, Fudan University, 200032, China; Institutes of Integrative Medicine, Fudan University, 200032, China.
| | - Lan Xu
- Department of Endocrinology, Wuxi People's Hospital, Nanjing Medical University, Wuxi, Jiangsu, 214023, China.
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22
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Bortezomib induces neuropathic pain through protein kinase C-mediated activation of presynaptic NMDA receptors in the spinal cord. Neuropharmacology 2017; 123:477-487. [PMID: 28663117 DOI: 10.1016/j.neuropharm.2017.06.027] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 06/06/2017] [Accepted: 06/24/2017] [Indexed: 12/22/2022]
Abstract
Chemotherapeutic drugs, including bortezomib, often cause painful peripheral neuropathy, which is a severe dose-limiting adverse effect experienced by many cancer patients. The glutamate N-methyl-d-aspartate receptors (NMDARs) at the spinal cord level are critically involved in the synaptic plasticity associated with neuropathic pain. In this study, we determined whether treatment with bortezomib, a proteasome inhibitor, affects the NMDAR activity of spinal dorsal horn neurons. Systemic treatment with bortezomib in rats did not significantly affect postsynaptic NMDAR currents elicited by puff application of NMDA directly to dorsal horn neurons. Bortezomib treatment markedly increased the baseline frequency of miniature excitatory postsynaptic currents (EPSCs), which was completely normalized by the NMDAR antagonist 2-amino-5-phosphonopentanoic acid (AP5). AP5 also reduced the amplitude of monosynaptic EPSCs evoked by dorsal root stimulation in bortezomib-treated, but not vehicle-treated, rats. Furthermore, inhibition of protein kinase C (PKC) with chelerythrine fully reversed the increased frequency of miniature EPSCs and the amplitude of evoked EPSCs in bortezomib-treated rats. Intrathecal injection of AP5 and chelerythrine both profoundly attenuated mechanical allodynia and hyperalgesia induced by systemic treatment with bortezomib. In addition, treatment with bortezomib induced striking membrane translocation of PKC-βII, PKC-δ, and PKC-ε in the dorsal root ganglion. Our findings indicate that bortezomib treatment potentiates nociceptive input from primary afferent nerves via PKC-mediated tonic activation of presynaptic NMDARs. Targeting presynaptic NMDARs and PKC at the spinal cord level may be an effective strategy for treating chemotherapy-induced neuropathic pain.
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Comorbid anxiety-like behavior and locus coeruleus impairment in diabetic peripheral neuropathy: A comparative study with the chronic constriction injury model. Prog Neuropsychopharmacol Biol Psychiatry 2016; 71:45-56. [PMID: 27328428 DOI: 10.1016/j.pnpbp.2016.06.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Revised: 05/31/2016] [Accepted: 06/16/2016] [Indexed: 01/22/2023]
Abstract
Anxiety frequently appears in patients with diabetic neuropathic pain, a highly prevalent clinical condition. However, the neurobiological mechanisms of this comorbidity are poorly known. Anxiogenic phenotype has been associated with alterations of the noradrenergic locus coeruleus (LC) after peripheral nerve entrapment. We have examined the sensorial (pain) and affective (anxiety) behaviors, and the LC activity in streptozotocin (STZ)-induced diabetic rats. A comparative study with the chronic constriction injury (CCI) model of sciatic nerve was also carried out. Diabetic nociceptive hypersensitivity was observed to appear gradually, reaching their maximum at fourth week. In contrast, CCI displayed a sharp decrease in their sensorial threshold at seventh day. In both models, anxiety-like phenotype was evident after four weeks but not earlier, coincident with the LC alterations. Indeed, STZ animals showed reduced LC firing activity, tyrosine hydroxylase, pCREB and noradrenaline transporter levels, contrary to observed in CCI animals. However, in both models, enhanced LC alpha2-adrenoceptor sensitivity was presented at this time point. This study demonstrated that diabetes induced anxiety-like behavior comorbid with LC impairment at long-term. However, the nociceptive sensitivity time-course, as well as the LC functions, showed distinct features compared to the CCI model, indicating that specific neuroplastic mechanisms are at play in every model.
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24
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Aydın TH, Can ÖD, Demir Özkay Ü, Turan N. Effect of subacute agomelatine treatment on painful diabetic neuropathy: involvement of catecholaminergic mechanisms. Fundam Clin Pharmacol 2016; 30:549-567. [PMID: 27421789 DOI: 10.1111/fcp.12224] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Revised: 06/22/2016] [Accepted: 07/08/2016] [Indexed: 12/18/2022]
Abstract
In this study, we investigated the effects of subacute agomelatine (40 and 80 mg/kg) administration on chronic hyperglycemia, metabolic parameters, and pain perception in streptozotocin-induced diabetic rats. Fasting blood glucose measurements and oral glucose tolerance tests were performed to evaluate the effect of agomelatine on glycemia, while metabolic parameters were monitored using metabolic cages. Potential effect of agomelatine on diabetes-induced mechanical and thermal allodynia was evaluated using dynamic plantar aesthesiometer and warm plate (38 °C) tests, respectively. Additionally, influence of agomelatine on hyperalgesia occurring in connection with diabetic neuropathy was examined using the Randall-Selitto (mechanical nociceptive stimulus), Hargreaves (thermal nociceptive stimulus), and cold plate (4 °C, thermal nociceptive stimulus) tests. Obtained data indicated that, in diabetic rats, agomelatine significantly improved hyperalgesia and allodynia responses, without no effect on hyperglycemia or the associated polydipsia, polyuria, and hyperphagia. Therapeutic potential of agomelatine on neuropathic pain was suppressed with α-methyl-para-tyrosine methyl ester (an inhibitor of catecholamine synthesis), phentolamine (a nonselective α-adrenoceptor antagonist), and propranolol (a nonselective β-adrenoceptor antagonist) administrations. However, p-chlorophenylalanine methyl ester (an inhibitor of serotonin synthesis) pretreatment could not be achieved to reverse these antihyperalgesic and antiallodynic effects. These results suggest that the curative effect of agomelatine on neuropathic pain is mediated through rising synaptic catecholamine levels as well as through interactions with both α- and β-adrenoceptors. To our knowledge, this is the first study to show findings that indicate catecholaminergic system mediated antihyperalgesic and antiallodynic effects of agomelatine.
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Affiliation(s)
- Taliha H Aydın
- Department of Pharmacology, Faculty of Pharmacy, Anadolu University, 26470, Eskişehir, Turkey
| | - Özgür D Can
- Department of Pharmacology, Faculty of Pharmacy, Anadolu University, 26470, Eskişehir, Turkey
| | - Ümide Demir Özkay
- Department of Pharmacology, Faculty of Pharmacy, Anadolu University, 26470, Eskişehir, Turkey
| | - Nazlı Turan
- Department of Pharmacology, Faculty of Pharmacy, Anadolu University, 26470, Eskişehir, Turkey
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Kou ZZ, Wan FP, Bai Y, Li CY, Hu JC, Zhang GT, Zhang T, Chen T, Wang YY, Li H, Li YQ. Decreased Endomorphin-2 and μ-Opioid Receptor in the Spinal Cord Are Associated with Painful Diabetic Neuropathy. Front Mol Neurosci 2016; 9:80. [PMID: 27656127 PMCID: PMC5013037 DOI: 10.3389/fnmol.2016.00080] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2016] [Accepted: 08/24/2016] [Indexed: 12/17/2022] Open
Abstract
Painful diabetic neuropathy (PDN) is one of the most common complications in the early stage of diabetes mellitus (DM). Endomorphin-2 (EM2) selectively activates the μ-opioid receptor (MOR) and subsequently induces antinociceptive effects in the spinal dorsal horn. However, the effects of EM2-MOR in PDN have not yet been clarified in the spinal dorsal horn. Therefore, we aimed to explore the role of EM2-MOR in the pathogenesis of PDN. The main findings were the following: (1) streptozotocin (STZ)-induced diabetic rats exhibited hyperglycemia, body weight loss and mechanical allodynia; (2) in the spinal dorsal horn, the expression levels of EM2 and MOR decreased in diabetic rats; (3) EM2 protein concentrations decreased in the brain, lumbar spinal cord and cerebrospinal fluid (CSF) in diabetic rats but were unchanged in the plasma; (4) the frequency but not the amplitude of spontaneous excitatory postsynaptic currents (sEPSCs) was significantly higher in diabetic rats than in control rats; and (5) intrathecal injection of EM2 for 14 days in the early stage of PDN partially alleviated mechanical allodynia and reduced MOR expression in diabetic rats. Our results demonstrate that the EM2-MOR signal may be involved in the early stage of PDN.
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Affiliation(s)
- Zhen-Zhen Kou
- Department of Anatomy and K.K. Leung Brain Research Centre, The Fourth Military Medical University Xi'an, China
| | - Fa-Ping Wan
- Department of Anatomy and K.K. Leung Brain Research Centre, The Fourth Military Medical University Xi'an, China
| | - Yang Bai
- Department of Anatomy and K.K. Leung Brain Research Centre, The Fourth Military Medical University Xi'an, China
| | - Chun-Yu Li
- Department of Anatomy and K.K. Leung Brain Research Centre, The Fourth Military Medical University Xi'an, China
| | - Jia-Chen Hu
- Department of Anatomy and K.K. Leung Brain Research Centre, The Fourth Military Medical University Xi'an, China
| | - Guo-Tao Zhang
- Department of Anatomy and K.K. Leung Brain Research Centre, The Fourth Military Medical University Xi'an, China
| | - Ting Zhang
- Department of Anatomy and K.K. Leung Brain Research Centre, The Fourth Military Medical University Xi'an, China
| | - Tao Chen
- Department of Anatomy and K.K. Leung Brain Research Centre, The Fourth Military Medical University Xi'an, China
| | - Ya-Yun Wang
- Department of Anatomy and K.K. Leung Brain Research Centre, The Fourth Military Medical University Xi'an, China
| | - Hui Li
- Department of Anatomy and K.K. Leung Brain Research Centre, The Fourth Military Medical University Xi'an, China
| | - Yun-Qing Li
- Department of Anatomy and K.K. Leung Brain Research Centre, The Fourth Military Medical UniversityXi'an, China; Collaborative Innovation Center for Brain Science, Fudan UniversityShanghai, China
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Xie JD, Chen SR, Chen H, Zeng WA, Pan HL. Presynaptic N-Methyl-d-aspartate (NMDA) Receptor Activity Is Increased Through Protein Kinase C in Paclitaxel-induced Neuropathic Pain. J Biol Chem 2016; 291:19364-73. [PMID: 27458019 DOI: 10.1074/jbc.m116.732347] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Indexed: 11/06/2022] Open
Abstract
Painful peripheral neuropathy is a severe adverse effect of chemotherapeutic drugs such as paclitaxel (Taxol). The glutamate N-methyl-d-aspartate receptors (NMDARs) are critically involved in the synaptic plasticity associated with neuropathic pain. However, paclitaxel treatment does not alter the postsynaptic NMDAR activity of spinal dorsal horn neurons. In this study, we determined whether paclitaxel affects presynaptic NMDAR activity by recording excitatory postsynaptic currents (EPSCs) of dorsal horn neurons in spinal cord slices. In paclitaxel-treated rats, the baseline frequency of miniature EPSCs (mEPSCs) was significantly increased; the NMDAR antagonist 2-amino-5-phosphonopentanoic acid (AP5) completely normalized this frequency. Also, AP5 significantly reduced the amplitude of monosynaptic EPSCs evoked by dorsal root stimulation and reversed the reduction in the paired-pulse ratio of evoked EPSCs in paclitaxel-treated rats. Blocking GluN2A-containing, but not GluN2B-containing, NMDARs largely decreased the frequency of mEPSCs and the amplitude of evoked EPSCs of dorsal horn neurons in paclitaxel-treated rats. Furthermore, inhibition of protein kinase C fully reversed the increased frequency of mEPSCs and the amplitude of evoked EPSCs in paclitaxel-treated rats. Paclitaxel treatment significantly increased the protein level of GluN2A and phosphorylated GluN1 in the dorsal root ganglion. In addition, intrathecal injection of AP5 or systemic administration of memantine profoundly attenuated pain hypersensitivity induced by paclitaxel. Our findings indicate that paclitaxel treatment induces tonic activation of presynaptic NMDARs in the spinal cord through protein kinase C to potentiate nociceptive input from primary afferent nerves. Targeting presynaptic NMDARs at the spinal cord level may be an effective strategy for treating chemotherapy-induced neuropathic pain.
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Affiliation(s)
- Jing-Dun Xie
- From the Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, The University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030 and Department of Anesthesiology, Sun Yat-Sen University Cancer Center, Guangzhou, Guangdong 510060, China
| | - Shao-Rui Chen
- From the Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, The University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030 and
| | - Hong Chen
- From the Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, The University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030 and
| | - Wei-An Zeng
- Department of Anesthesiology, Sun Yat-Sen University Cancer Center, Guangzhou, Guangdong 510060, China
| | - Hui-Lin Pan
- From the Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, The University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030 and
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He WY, Zhang B, Xiong QM, Yang CX, Zhao WC, He J, Zhou J, Wang HB. Intrathecal administration of rapamycin inhibits the phosphorylation of DRG Nav1.8 and attenuates STZ-induced painful diabetic neuropathy in rats. Neurosci Lett 2016; 619:21-8. [DOI: 10.1016/j.neulet.2016.02.064] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Revised: 02/27/2016] [Accepted: 02/29/2016] [Indexed: 01/19/2023]
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Benitez SU, Carneiro EM, de Oliveira ALR. Synaptic input changes to spinal cord motoneurons correlate with motor control impairments in a type 1 diabetes mellitus model. Brain Behav 2015; 5:e00372. [PMID: 26516607 PMCID: PMC4614060 DOI: 10.1002/brb3.372] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Revised: 07/09/2015] [Accepted: 07/18/2015] [Indexed: 01/07/2023] Open
Abstract
INTRODUCTION Hyperglycemia is the main cause of diabetic complications, contributing to a widespread degeneration of the nervous system. Nevertheless, the main focus has been the sensory neurons because of neuropathic pain, while the impairments associated with the spinal cord and motor deficits, mostly of those initiated at early stages of the disease, have been poorly investigated. In this way, the present study used the nonobese diabetic mouse model to evaluate the microenvironment around motoneurons at ventral horn of the spinal cord, following prolonged hyperglycemia. METHODS Adult female mice were divided into two groups: spontaneously diabetic (n = 33) and nondiabetic (n = 26). Mice were considered hyperglycemic when blood glucose surpassed 400 mg/dL. Following 2 weeks from that stage, part of the animals was euthanized and the lumbar intumescences were obtained and processed for immunohistochemistry and transmission electron microscopy. For immunohistochemistry, the antibodies used for integrated density of pixels quantification were anti-synaptophysin, anti-GFAP, and anti-Iba1. The functional analysis was monitored with the walking track test (CatWalk system) during 4 weeks. RESULTS The results revealed significant motor impairment in diabetic animals in comparison to the control group. Such loss of motor control correlated with a significant reduction in presynaptic terminals apposed to the motoneurons. Nevertheless, there were no significant changes in glial reaction in the spinal cord. CONCLUSION Overall, the results herein revealed central nervous system changes at early stages of the disease that may in turn contribute to the motor deficit. Such changes open a new window of investigation in early stages of diabetes to better comprehend motor impairment as a long-term complication of the disease.
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Affiliation(s)
- Suzana Ulian Benitez
- Department of Structural and Functional Biology Institute of Biology State University of Campinas 13083-970 Campinas Sao Paulo Brazil
| | - Everardo Magalhães Carneiro
- Department of Structural and Functional Biology Institute of Biology State University of Campinas 13083-970 Campinas Sao Paulo Brazil
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Lyu C, Mulder J, Barde S, Sahlholm K, Zeberg H, Nilsson J, Århem P, Hökfelt T, Fried K, Shi TJS. G protein-gated inwardly rectifying potassium channel subunits 1 and 2 are down-regulated in rat dorsal root ganglion neurons and spinal cord after peripheral axotomy. Mol Pain 2015. [PMID: 26199148 PMCID: PMC4511542 DOI: 10.1186/s12990-015-0044-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Background Increased nociceptive neuronal excitability underlies chronic pain conditions. Various ion channels, including sodium, calcium and potassium channels have pivotal roles in the control of neuronal excitability. The members of the family of G protein-gated inwardly rectifying potassium (GIRK) channels, GIRK1–4, have been implicated in modulating excitability. Here, we investigated the expression and distribution of GIRK1 and GIRK2 in normal and injured dorsal root ganglia (DRGs) and spinal cord of rats. Results We found that ~70% of the DRG neurons expressed GIRK1, while only <10% expressed GIRK2. The neurochemical profiles of GIRK1- and GIRK2-immunoreactive neurons were characterized using the neuronal markers calcitonin gene-related peptide, isolectin-B4 and neurofilament-200, and the calcium-binding proteins calbindin D28k, calretinin, parvalbumin and secretagogin. Both GIRK subunits were expressed in DRG neurons with nociceptive characteristics. However, while GIRK1 was widely expressed in several sensory neuronal subtypes, GIRK2 was detected mainly in a group of small C-fiber neurons. In the spinal dorsal horn, GIRK1- and -2-positive cell bodies and processes were mainly observed in lamina II, but also in superficial and deeper layers. Abundant GIRK1-, but not GIRK2-like immunoreactivity, was found in the ventral horn (laminae VI–X). Fourteen days after axotomy, GIRK1 and GIRK2 were down-regulated in DRG neurons at the mRNA and protein levels. Both after axotomy and rhizotomy there was a reduction of GIRK1- and -2-positive processes in the dorsal horn, suggesting a presynaptic localization of these potassium channels. Furthermore, nerve ligation caused accumulation of both subunits on both sides of the lesion, providing evidence for anterograde and retrograde fast axonal transport. Conclusions Our data support the hypothesis that reduced GIRK function is associated with increased neuronal excitability and causes sensory disturbances in post-injury conditions, including neuropathic pain. Electronic supplementary material The online version of this article (doi:10.1186/s12990-015-0044-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Chuang Lyu
- School of Life Science and Technology, Harbin Institute of Technology, 150001, Harbin, China. .,Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden.
| | - Jan Mulder
- Department of Neuroscience, Science for Life Laboratory, Karolinska Institutet, 171 77, Stockholm, Sweden.
| | - Swapnali Barde
- Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden.
| | - Kristoffer Sahlholm
- Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden.
| | - Hugo Zeberg
- Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden.
| | - Johanna Nilsson
- Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden.
| | - Peter Århem
- Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden.
| | - Tomas Hökfelt
- Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden.
| | - Kaj Fried
- Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden.
| | - Tie-Jun Sten Shi
- School of Life Science and Technology, Harbin Institute of Technology, 150001, Harbin, China. .,Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden.
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Üçel Uİ, Can ÖD, Demir Özkay Ü, Öztürk Y. Antihyperalgesic and antiallodynic effects of mianserin on diabetic neuropathic pain: a study on mechanism of action. Eur J Pharmacol 2015; 756:92-106. [PMID: 25771454 DOI: 10.1016/j.ejphar.2015.02.048] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Revised: 02/20/2015] [Accepted: 02/24/2015] [Indexed: 12/14/2022]
Abstract
This study used various experimental pain methods to investigate the effects of subacute mianserin administration on diabetes-induced neuropathic pain in rats. The effect of mianserin on hyperalgesia occurring in connection with peripheral diabetic neuropathy was examined using the Randall-Selitto (mechanical nociceptive stimulus), Hargreaves (thermal nociceptive stimulus), and cold-plate (4°C, thermal nociceptive stimulus) tests. The dynamic plantar aesthesiometer, which measures the threshold values for mechanical stimuli, was used for allodynia studies. Thermal allodynia was evaluated with the warm-plate (38°C) test. At 30 and 45 mg/kg, mianserin effectively improved mechanical and thermal hyperalgesia occurring in connection with diabetic neuropathy. Subacute administration of mianserin also reduced diabetes-associated mechanical and thermal allodynia. The ability of mianserin to reduce diabetic neuropathic pain was comparable to that of pregabalin (10mg/kg). The antihyperalgesic and antiallodynic effects of mianserin were reversed with α-methyl-para-tyrosine methyl ester (AMPT, an inhibitor of catecholamine synthesis), phentolamine (a non-selective α-adrenoceptor antagonist), propranolol (a non-selective β-adrenoceptor antagonist), and naloxone (a non-selective opioid receptor antagonist) administrations. The same effects were not reversed, however, by para-chlorophenylalanine methyl ester (PCPA; an inhibitor of serotonin synthesis). These results suggest that the beneficial effect of mianserin on diabetic neuropathic pain is mediated through an increase in catecholamine levels in the synaptic cleft as well as through interactions with both subtypes of adrenoceptors and opioid receptors. Considering that mianserin exhibits simultaneous antidepressant and antinociceptive effects, this drug could provide a good alternative for treating the pain associated with diabetic neuropathy and the mood disorders caused directly by diabetes.
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Affiliation(s)
- Umut İrfan Üçel
- Anadolu University, Faculty of Pharmacy, Department of Pharmacology, 26470 Eskişehir, Turkey
| | - Özgür Devrim Can
- Anadolu University, Faculty of Pharmacy, Department of Pharmacology, 26470 Eskişehir, Turkey.
| | - Ümide Demir Özkay
- Anadolu University, Faculty of Pharmacy, Department of Pharmacology, 26470 Eskişehir, Turkey
| | - Yusuf Öztürk
- Anadolu University, Faculty of Pharmacy, Department of Pharmacology, 26470 Eskişehir, Turkey
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Altamirano-Espinoza AH, Manrique-Maldonado G, Marichal-Cancino BA, Villalón CM. Specific role of α2A - and α2B -, but not α2C -, adrenoceptor subtypes in the inhibition of the vasopressor sympathetic out-flow in diabetic pithed rats. Basic Clin Pharmacol Toxicol 2014; 117:31-8. [PMID: 25407049 DOI: 10.1111/bcpt.12354] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Accepted: 11/11/2014] [Indexed: 11/30/2022]
Abstract
Several lines of evidence have shown an association of diabetes with a catecholamines' aberrant homeostasis involving a drastic change in the expression of adrenoceptors. This homeostatic alteration includes, among other things, atypical actions of α2 -adrenoceptor agonists within central and peripheral α2 -adrenoceptors (e.g. profound antinociceptive effects in diabetic subjects). Hence, this study investigated the pharmacological profile of the α2 -adrenoceptor subtypes that inhibit the vasopressor sympathetic out-flow in streptozotocin-pre-treated (diabetic) pithed rats. For this purpose, B-HT 933 (up to 30 μg/kg min) was used as a selective α2 -adrenoceptor agonist and rauwolscine as a non-selective α2A/2B/2C -adrenoceptor antagonist; in addition, BRL 44408, imiloxan and JP-1302 were used as subtype-selective α2A -, α2B - and α2C -adrenoceptor antagonists, respectively (all given i.v.). I.v. continuous infusions of B-HT 933 inhibited the vasopressor responses induced by electrical sympathetic stimulation without affecting those by i.v. bolus injections of noradrenaline in both normoglycaemic and diabetic rats. Interestingly, the ED50 for B-HT 933 in diabetic rats (25 μg/kg min) was almost 1-log unit greater than that in normoglycaemic rats (3 μg/kg.min). Moreover, the sympatho-inhibition induced by 10 μg/kg min B-HT 933 in diabetic rats was (i) abolished by 300 μg/kg rauwolscine or 100 and 300 μg/kg BRL 44408; (ii) partially blocked by 1000 μg/kg imiloxan; and (iii) unchanged by 1000 μg/kg JP-1302. Our findings, taken together, suggest that B-HT 933 has a less potent inhibitory effect on the sympathetic vasopressor responses in diabetic (compared to normoglycaemic) rats and that can probably be ascribed to a down-regulation of α2C -adrenoceptors.
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Affiliation(s)
| | | | | | - Carlos M Villalón
- Deparment of pharmaco-biology, Cinvestav-Coapa, Tlalpan, Mexico D.F., Mexico
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Aira Z, Barrenetxea T, Buesa I, Azkue JJ. Plasticity of α2-adrenergic spinal antinociception following nerve injury: selective, bidirectional interaction with the delta opioid receptor. Brain Res 2014; 1594:190-203. [PMID: 25446445 DOI: 10.1016/j.brainres.2014.11.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Revised: 11/04/2014] [Accepted: 11/06/2014] [Indexed: 11/25/2022]
Abstract
Interactions of opioid receptors with other receptor families can be made use of to improve analgesia and reduce adverse effects of opioid analgesics. We investigated interactions of the α2-adrenergic receptor (α2AR) with opioid receptors of the mu (MOR) and delta (DOR) types in the spinal dorsal horn in an animal model of neuropathic pain induced by spinal nerve ligation. Nine days after nerve injury, immunoreactivity for the α2AR subtype A (α2AAR) was increased both in tissue homogenates and at pre- and post-synaptic sites in transverse sections. The efficacy of spinally administered α2AAR agonist guanfacine at reducing C-fiber-evoked field potentials was increased in nerve-ligated rats. This reducing effect was impaired by simultaneous administration of DOR antagonist naltrindole, but not MOR antagonist CTOP, suggesting that concurrent DOR activation was required for α2AAR-mediated inhibition. While DOR agonist deltorphin II and MOR agonist DAMGO both effectively depressed C-fiber-evoked spinal field potentials, DOR- but not MOR-mediated depression was enhanced by subclinical guanfacine. In conscious, nerve-ligated rats, chronically administered deltorphin II produced stable thermal and mechanical antinociception over the 9 following days after nerve injury without apparent signs of habituation. Such an effect was dramatically enhanced by co-administration of a low dose of guanfacine, which reversed thermal and mechanical thresholds to levels near those prior to injury. The results suggest that spinal, α2AAR-mediated antinociception is increased after nerve injury and based on DOR co-activation. We demonstrate in vivo that α2AAR/DOR interaction can be exploited to provide effective behavioral antinociception during neuropathic pain.
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Affiliation(s)
- Zigor Aira
- Department of Neurosciences, School of Medicine and Dentistry, University of the Basque Country, PO Box 699, 48080 Bilbao, Spain
| | - Teresa Barrenetxea
- Department of Neurosciences, School of Medicine and Dentistry, University of the Basque Country, PO Box 699, 48080 Bilbao, Spain
| | - Itsaso Buesa
- Department of Neurosciences, School of Medicine and Dentistry, University of the Basque Country, PO Box 699, 48080 Bilbao, Spain
| | - Jon Jatsu Azkue
- Department of Neurosciences, School of Medicine and Dentistry, University of the Basque Country, PO Box 699, 48080 Bilbao, Spain.
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Sakakiyama M, Maeda S, Isami K, Asakura K, So K, Shirakawa H, Nakagawa T, Kaneko S. Preventive and Alleviative Effect of Tramadol on Neuropathic Pain in Rats: Roles of α2-Adrenoceptors and Spinal Astrocytes. J Pharmacol Sci 2014; 124:244-57. [DOI: 10.1254/jphs.13223fp] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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Kinoshita J, Takahashi Y, Watabe AM, Utsunomiya K, Kato F. Impaired noradrenaline homeostasis in rats with painful diabetic neuropathy as a target of duloxetine analgesia. Mol Pain 2013; 9:59. [PMID: 24279796 PMCID: PMC4222693 DOI: 10.1186/1744-8069-9-59] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Accepted: 11/22/2013] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND Painful diabetic neuropathy (PDN) is a serious complication of diabetes mellitus that affects a large number of patients in many countries. The molecular mechanisms underlying the exaggerated nociception in PDN have not been established. Recently, duloxetine (DLX), a serotonin and noradrenaline re-uptake inhibitor, has been recommended as one of the first-line treatments of PDN in the United States Food and Drug Administration, the European Medicines Agency and the Japanese Guideline for the Pharmacologic Management of Neuropathic pain. Because selective serotonin re-uptake inhibitors show limited analgesic effects in PDN, we examined whether the potent analgesic effect of DLX contributes toward improving the pathologically aberrant noradrenaline homeostasis in diabetic models. RESULTS In streptozotocin (STZ) (50 mg/kg, i.v.)-induced diabetic rats that exhibited robust mechanical allodynia and thermal hyperalgesia, DLX (10 mg/kg, i.p.) significantly and markedly increased the nociceptive threshold. The analgesic effect of DLX was nullified by the prior administration of N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) (50 mg/kg, i.p.), which drastically eliminated dopamine-beta-hydroxylase- and norepinephrine transporter-immunopositive fibers in the lumbar spinal dorsal horn and significantly reduced the noradrenaline content in the lumbar spinal cord. The treatment with DSP-4 alone markedly lowered the nociceptive threshold in vehicle-treated non-diabetic rats; however, this pro-nociceptive effect was occluded in STZ-treated diabetic rats. Furthermore, STZ-treated rats exhibited a higher amount of dopamine-beta-hydroxylase- and norepinephrine transporter-immunopositive fibers in the dorsal horn and noradrenaline content in the spinal cord compared to vehicle-treated rats. CONCLUSIONS Impaired noradrenaline-mediated regulation of the spinal nociceptive network might underlie exaggerated nociception in PDN. DLX might exert its analgesic effect by selective enhancement of noradrenergic signals, thus counteracting this situation.
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Affiliation(s)
- Jun Kinoshita
- Department of Neuroscience, Jikei University School of Medicine, Minato, Tokyo 105-8461, Japan.
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Zhao YL, Chen SR, Chen H, Pan HL. Chronic opioid potentiates presynaptic but impairs postsynaptic N-methyl-D-aspartic acid receptor activity in spinal cords: implications for opioid hyperalgesia and tolerance. J Biol Chem 2012; 287:25073-85. [PMID: 22679016 DOI: 10.1074/jbc.m112.378737] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Opioids are the most effective analgesics for the treatment of moderate to severe pain. However, chronic opioid treatment can cause both hyperalgesia and analgesic tolerance, which limit their clinical efficacy. In this study, we determined the role of pre- and postsynaptic NMDA receptors (NMDARs) in controlling increased glutamatergic input in the spinal cord induced by chronic systemic morphine administration. Whole-cell voltage clamp recordings of excitatory postsynaptic currents (EPSCs) were performed on dorsal horn neurons in rat spinal cord slices. Chronic morphine significantly increased the amplitude of monosynaptic EPSCs evoked from the dorsal root and the frequency of spontaneous EPSCs, and these changes were largely attenuated by blocking NMDARs and by inhibiting PKC, but not PKA. Also, blocking NR2A- or NR2B-containing NMDARs significantly reduced the frequency of spontaneous EPSCs and the amplitude of evoked EPSCs in morphine-treated rats. Strikingly, morphine treatment largely decreased the amplitude of evoked NMDAR-EPSCs and NMDAR currents of dorsal horn neurons elicited by puff NMDA application. The reduction in postsynaptic NMDAR currents caused by morphine was prevented by resiniferatoxin pretreatment to ablate TRPV1-expressing primary afferents. Furthermore, intrathecal injection of the NMDAR antagonist significantly attenuated the development of analgesic tolerance and the reduction in nociceptive thresholds induced by chronic morphine. Collectively, our findings indicate that chronic opioid treatment potentiates presynaptic, but impairs postsynaptic, NMDAR activity in the spinal cord. PKC-mediated increases in NMDAR activity at nociceptive primary afferent terminals in the spinal cord contribute critically to the development of opioid hyperalgesia and analgesic tolerance.
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Affiliation(s)
- Yi-Lin Zhao
- Center for Pain and Neuroscience Research, Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA
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Alba-Delgado C, Borges G, Sánchez-Blázquez P, Ortega JE, Horrillo I, Mico JA, Meana JJ, Neto F, Berrocoso E. The function of alpha-2-adrenoceptors in the rat locus coeruleus is preserved in the chronic constriction injury model of neuropathic pain. Psychopharmacology (Berl) 2012; 221:53-65. [PMID: 22038538 DOI: 10.1007/s00213-011-2542-7] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Accepted: 10/11/2011] [Indexed: 11/24/2022]
Abstract
RATIONALE Peripheral neuropathic pain is a chronic condition that may produce plastic changes in several brain regions. The noradrenergic locus coeruleus (LC) is a crucial component of ascending and descending pain pathways, both of which are frequently compromised after nerve injury. OBJECTIVES The objective of the study was to examine whether chronic constriction injury (CCI), a model of neuropathic pain, alters noradrenergic activity in the rat LC. METHODS Activity in the LC was assessed by electrophysiology and microdialysis, while protein expression was monitored in western blots and by immunohistochemistry. RESULTS The pain threshold had dropped in injured rats 7 days after inducing neuropathy. While alpha-2-adrenoceptors mediate activity in the LC and in its terminal areas, no alterations in either spontaneous neuronal activity or extracellular noradrenaline levels were observed following CCI. Moreover, alpha-2-adrenoceptor activity in the LC of CCI rats remained unchanged after systemic administration of UK14,304, RX821002 or desipramine. Accordingly, extracellular noradrenaline levels in the LC were similar in CCI and control animals following local administration of clonidine or RX821002. In addition, there were no changes in the expression of the alpha-2-adrenoceptors, Gαi/z subunits or the regulators of G-protein signaling. However, pERK1/2 (phosphorylated extracellular signal-regulated kinases 1/2) expression augmented in the spinal cord, paragigantocellularis nucleus (PGi) and dorsal raphe nucleus (DRN) following CCI. CONCLUSIONS Neuropathic pain is not accompanied by modifications in tonic LC activity after the onset of pain. This may indicate that the signals from the PGi and DRN, the excitatory and inhibitory afferents of the LC, cancel one another out.
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Affiliation(s)
- Cristina Alba-Delgado
- Neuropsychopharmacology Research Group, Department of Neuroscience, University of Cadiz, 11003 Cadiz, Spain
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Lee KK, Omiya Y, Yuzurihara M, Kase Y, Kobayashi H. Antinociceptive effect of paeoniflorin via spinal α2
-adrenoceptor activation in diabetic mice. Eur J Pain 2012; 15:1035-9. [DOI: 10.1016/j.ejpain.2011.04.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Revised: 03/14/2011] [Accepted: 04/20/2011] [Indexed: 11/28/2022]
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Li L, Cao XH, Chen SR, Han HD, Lopez-Berestein G, Sood AK, Pan HL. Up-regulation of Cavβ3 subunit in primary sensory neurons increases voltage-activated Ca2+ channel activity and nociceptive input in neuropathic pain. J Biol Chem 2011; 287:6002-13. [PMID: 22187436 DOI: 10.1074/jbc.m111.310110] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
High voltage-activated calcium channels (HVACCs) are essential for synaptic and nociceptive transmission. Although blocking HVACCs can effectively reduce pain, this treatment strategy is associated with intolerable adverse effects. Neuronal HVACCs are typically composed of α(1), β (Cavβ), and α(2)δ subunits. The Cavβ subunit plays a crucial role in the membrane expression and gating properties of the pore-forming α(1) subunit. However, little is known about how nerve injury affects the expression and function of Cavβ subunits in primary sensory neurons. In this study, we found that Cavβ(3) and Cavβ(4) are the most prominent subtypes expressed in the rat dorsal root ganglion (DRG) and dorsal spinal cord. Spinal nerve ligation (SNL) in rats significantly increased mRNA and protein levels of the Cavβ(3), but not Cavβ(4), subunit in the DRG. SNL also significantly increased HVACC currents in small DRG neurons and monosynaptic excitatory postsynaptic currents of spinal dorsal horn neurons evoked from the dorsal root. Intrathecal injection of Cavβ(3)-specific siRNA significantly reduced HVACC currents in small DRG neurons and the amplitude of monosynaptic excitatory postsynaptic currents of dorsal horn neurons in SNL rats. Furthermore, intrathecal treatment with Cavβ(3)-specific siRNA normalized mechanical hyperalgesia and tactile allodynia caused by SNL but had no significant effect on the normal nociceptive threshold. Our findings provide novel evidence that increased expression of the Cavβ(3) subunit augments HVACC activity in primary sensory neurons and nociceptive input to dorsal horn neurons in neuropathic pain. Targeting the Cavβ(3) subunit at the spinal level represents an effective strategy for treating neuropathic pain.
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Affiliation(s)
- Li Li
- Department of Anesthesiology and Perioperative Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, USA
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