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Ding X, Cai J, Li S, Liu XD, Wan Y, Xing GG. BDNF contributes to the development of neuropathic pain by induction of spinal long-term potentiation via SHP2 associated GluN2B-containing NMDA receptors activation in rats with spinal nerve ligation. Neurobiol Dis 2014; 73:428-51. [PMID: 25447233 DOI: 10.1016/j.nbd.2014.10.025] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 10/16/2014] [Accepted: 10/31/2014] [Indexed: 12/30/2022] Open
Abstract
The pathogenic mechanisms underlying neuropathic pain still remain largely unknown. In this study, we investigated whether spinal BDNF contributes to dorsal horn LTP induction and neuropathic pain development by activation of GluN2B-NMDA receptors via Src homology-2 domain-containing protein tyrosine phosphatase-2 (SHP2) phosphorylation in rats following spinal nerve ligation (SNL). We first demonstrated that spinal BDNF participates in the development of long-lasting hyperexcitability of dorsal horn WDR neurons (i.e. central sensitization) as well as pain allodynia in both intact and SNL rats. Second, we revealed that BDNF induces spinal LTP at C-fiber synapses via functional up-regulation of GluN2B-NMDA receptors in the spinal dorsal horn, and this BDNF-mediated LTP-like state is responsible for the occlusion of spinal LTP elicited by subsequent high-frequency electrical stimulation (HFS) of the sciatic nerve in SNL rats. Finally, we validated that BDNF-evoked SHP2 phosphorylation is required for subsequent GluN2B-NMDA receptors up-regulation and spinal LTP induction, and also for pain allodynia development. Blockade of SHP2 phosphorylation in the spinal dorsal horn using a potent SHP2 protein tyrosine phosphatase inhibitor NSC-87877, or knockdown of spinal SHP2 by intrathecal delivery of SHP2 siRNA, not only prevents BDNF-mediated GluN2B-NMDA receptors activation as well as spinal LTP induction and pain allodynia elicitation in intact rats, but also reduces the SNL-evoked GluN2B-NMDA receptors up-regulation and spinal LTP occlusion, and ultimately alleviates pain allodynia in neuropathic rats. Taken together, these results suggest that the BDNF/SHP2/GluN2B-NMDA signaling cascade plays a vital role in the development of central sensitization and neuropathic pain after peripheral nerve injury.
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Affiliation(s)
- Xu Ding
- Neuroscience Research Institute, Peking University, Beijing 100191, P.R. China; Department of Neurobiology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, P.R. China.
| | - Jie Cai
- Neuroscience Research Institute, Peking University, Beijing 100191, P.R. China; Department of Neurobiology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, P.R. China.
| | - Song Li
- Neuroscience Research Institute, Peking University, Beijing 100191, P.R. China; Department of Neurobiology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, P.R. China.
| | - Xiao-Dan Liu
- Neuroscience Research Institute, Peking University, Beijing 100191, P.R. China; Department of Neurobiology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, P.R. China.
| | - You Wan
- Neuroscience Research Institute, Peking University, Beijing 100191, P.R. China; Department of Neurobiology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, P.R. China.
| | - Guo-Gang Xing
- Neuroscience Research Institute, Peking University, Beijing 100191, P.R. China; Department of Neurobiology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, P.R. China; Key Laboratory for Neuroscience, Ministry of Education and Ministry of Health, Beijing 100191, P.R. China.
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A spinal analog of memory reconsolidation enables reversal of hyperalgesia. Nat Neurosci 2014; 17:1043-5. [PMID: 24997764 PMCID: PMC4978538 DOI: 10.1038/nn.3758] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Accepted: 06/06/2014] [Indexed: 01/21/2023]
Abstract
Hyperalgesia arising from sensitization of pain relays in the spinal dorsal horn shares many mechanistic and phenotypic parallels with memory formation. We discover that mechanical hyperalgesia can be rendered labile and reversible in mice after reactivation of spinal pain pathways in a process analogous to memory reconsolidation. These findings reveal a novel regulatory mechanism underlying hyperalgesia and demonstrate the existence of reconsolidation-like processes in a sensory system.
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Luo C, Kuner T, Kuner R. Synaptic plasticity in pathological pain. Trends Neurosci 2014; 37:343-55. [DOI: 10.1016/j.tins.2014.04.002] [Citation(s) in RCA: 126] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Revised: 03/31/2014] [Accepted: 04/09/2014] [Indexed: 02/06/2023]
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Yang F, Guo J, Sun WL, Liu FY, Cai J, Xing GG, Wan Y. The induction of long-term potentiation in spinal dorsal horn after peripheral nociceptive stimulation and contribution of spinal TRPV1 in rats. Neuroscience 2014; 269:59-66. [DOI: 10.1016/j.neuroscience.2014.03.037] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Revised: 02/18/2014] [Accepted: 03/18/2014] [Indexed: 11/29/2022]
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Bian C, Wang ZC, Yang JL, Lu N, Zhao ZQ, Zhang YQ. Up-regulation of interleukin-23 induces persistent allodynia via CX3CL1 and interleukin-18 signaling in the rat spinal cord after tetanic sciatic stimulation. Brain Behav Immun 2014; 37:220-30. [PMID: 24362237 DOI: 10.1016/j.bbi.2013.12.011] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Revised: 12/06/2013] [Accepted: 12/13/2013] [Indexed: 12/21/2022] Open
Abstract
Tetanic stimulation of the sciatic nerve (TSS) induces sciatic nerve injury and long-lasting pain hypersensitivity in rats, and spinal glial activation and proinflammatory cytokines releases are involved. In the present study, we showed that spinal interleukin (IL)-23 and its receptor, IL-23R, are crucial for the development of mechanical allodynia after TSS. In the spinal dorsal horn, both IL-23 and IL-23R are expressed in astrocytes, and this expression is substantially increased after TSS. Inhibition of IL-23 signaling attenuated TSS-induced allodynia and decreased the induction of glial fibrillary acidic protein (GFAP, an astrocytic marker). Conversely, intrathecally delivered IL-23 induced a persistent allodynia. Similar to IL-23 signaling, an increase in IL-18 and its receptor, IL-18R, as well as CX3CL1 and its receptor, CX3CR1, was simultaneously observed in the spinal dorsal horn after TSS. Interestingly, IL-18 and CX3CR1 were exclusively expressed in microglia, while IL-18R was mainly localized in astrocytes. In contrast, CX3CL1 was predominately expressed in neurons and secondarily in astrocytes. The functional inhibition of CX3CL1 and IL-18 signaling attenuated TSS-induced allodynia and suppressed IL-23 and IL-23R upregulation. Activation of CX3CR1 and IL-18R induced similar behavioral and biochemical changes to those observed after TSS. These results indicate that the interaction among CX3CL1, IL-18 and IL-23 signaling in the spinal cord plays a critical role in the development of allodynia. Thus, interrupting this chemokine-cytokine network might provide a novel therapeutic strategy for neuropathic pain.
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Affiliation(s)
- Chao Bian
- Institute of Neurobiology, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 200032, China
| | - Zhe-Chen Wang
- Institute of Neurobiology, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 200032, China
| | - Jia-Le Yang
- Institute of Neurobiology, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 200032, China
| | - Ning Lu
- Institute of Neurobiology, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 200032, China
| | - Zhi-Qi Zhao
- Institute of Neurobiology, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 200032, China
| | - Yu-Qiu Zhang
- Institute of Neurobiology, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 200032, China.
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Hur SW, Park JM. Long-term potentiation of excitatory synaptic strength in spinothalamic tract neurons of the rat spinal cord. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2013; 17:553-558. [PMID: 24381506 PMCID: PMC3874444 DOI: 10.4196/kjpp.2013.17.6.553] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Revised: 11/26/2013] [Accepted: 11/27/2013] [Indexed: 06/03/2023]
Abstract
Spinal dorsal horn nociceptive neurons have been shown to undergo long-term synaptic plasticity, including long-term potentiation (LTP) and long-term depression (LTD). Here, we focused on the spinothalamic tract (STT) neurons that are the main nociceptive neurons projecting from the spinal cord to the thalamus. Optical technique using fluorescent dye has made it possible to identify the STT neurons in the spinal cord. Evoked fast mono-synaptic, excitatory postsynaptic currents (eEPSCs) were measured in the STT neurons. Time-based tetanic stimulation (TBS) was employed to induce long-term potentiation (LTP) in the STT neurons. Coincident stimulation of both pre- and postsynaptic neurons using TBS showed immediate and persistent increase in AMPA receptor-mediated EPSCs. LTP can also be induced by postsynaptic spiking together with pharmacological stimulation using chemical NMDA. TBS-induced LTP observed in STT neurons was blocked by internal BAPTA, or Ni(2+), a T-type VOCC blocker. However, LTP was intact in the presence of L-type VOCC blocker. These results suggest that long-term plastic change of STT neurons requires NMDA receptor activation and postsynaptic calcium but is differentially sensitive to T-type VOCCs.
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Affiliation(s)
- Sung Won Hur
- Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Korea
| | - Joo Min Park
- Department of Physiology, Jeju National University College of Medicine, Jeju 690-756, Korea
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Ionotropic glutamate receptors and voltage-gated Ca²⁺ channels in long-term potentiation of spinal dorsal horn synapses and pain hypersensitivity. Neural Plast 2013; 2013:654257. [PMID: 24224102 PMCID: PMC3808892 DOI: 10.1155/2013/654257] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Revised: 08/27/2013] [Accepted: 08/27/2013] [Indexed: 12/18/2022] Open
Abstract
Over the last twenty years of research on cellular mechanisms of pain hypersensitivity, long-term potentiation (LTP) of synaptic transmission in the spinal cord dorsal horn (DH) has emerged as an important contributor to pain pathology. Mechanisms that underlie LTP of spinal DH neurons include changes in the numbers, activity, and properties of ionotropic glutamate receptors (AMPA and NMDA receptors) and of voltage-gated Ca2+ channels. Here, we review the roles and mechanisms of these channels in the induction and expression of spinal DH LTP, and we present this within the framework of the anatomical organization and synaptic circuitry of the spinal DH. Moreover, we compare synaptic plasticity in the spinal DH with classical LTP described for hippocampal synapses.
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Sanoja R, Taepavarapruk N, Benda E, Tadavarty R, Soja PJ. Enhanced excitability of thalamic sensory neurons and slow-wave EEG pattern after stimuli that induce spinal long-term potentiation. J Neurosci 2013; 33:15109-19. [PMID: 24048841 PMCID: PMC6618413 DOI: 10.1523/jneurosci.2110-13.2013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Revised: 07/24/2013] [Accepted: 08/13/2013] [Indexed: 11/21/2022] Open
Abstract
Spinal nociceptive neurons are well known to undergo a process of long-term potentiation (LTP) following conditioning by high-frequency sciatic nerve stimulation (HFS) at intensities recruiting C-fibers. However, little if any information exists as to whether such HFS conditioning that produces spinal LTP affects sensory transmission at supraspinal levels. The present study explored this possibility. Conventional extracellular recording methods were used to examine the consequences of HFS versus sham HFS conditioning on individual wide-dynamic range thalamic neurons located in the ventro-postero-lateral (VPL) nucleus in isoflurane-anesthetized rats. Following HFS, the ongoing firing rate and stimulus-evoked (brush, pinch, sciatic nerve) responses were markedly enhanced as were responses to juxtacellular, microiontophoretic applications of glutamate. These HFS-induced enhancements lasted throughout the recording period. Sham stimuli had no effect on VPL neuron excitability. Cortical electroencephalographic (EEG) wave activities were also measured around HFS in conjunction with VPL neuron recordings. The cortical EEG pattern under baseline conditions consisted of recurring short duration bursts of high-amplitude slow waves followed by longer periods of flat EEG. Following HFS, the EEG shifted to a continuous large-amplitude, slow-wave pattern within the 0.5-8.0 Hz bandwidth lasting throughout the recording period. Sham HFS did not alter EEG activity. Sciatic nerve conditioning at A-δ fiber strength, known to reverse spinal LTP, did not alter enhanced neuronal excitability or the EEG slow-wave pattern induced by HFS. These data support the concept that HFS conditioning of the sciatic nerve, which leads to spinal LTP, is associated with distinct, long-lasting changes in the excitability of neurons comprising thalamocortical networks.
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Affiliation(s)
- Raul Sanoja
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia, V6T 1Z3 Canada
| | - Niwat Taepavarapruk
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia, V6T 1Z3 Canada
| | - Elke Benda
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia, V6T 1Z3 Canada
| | - Ramakrishna Tadavarty
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia, V6T 1Z3 Canada
| | - Peter J. Soja
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia, V6T 1Z3 Canada
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Cortical presynaptic control of dorsal horn C-afferents in the rat. PLoS One 2013; 8:e69063. [PMID: 23935924 PMCID: PMC3728294 DOI: 10.1371/journal.pone.0069063] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Accepted: 06/10/2013] [Indexed: 12/01/2022] Open
Abstract
Lamina 5 sensorimotor cortex pyramidal neurons project to the spinal cord, participating in the modulation of several modalities of information transmission. A well-studied mechanism by which the corticospinal projection modulates sensory information is primary afferent depolarization, which has been characterized in fast muscular and cutaneous, but not in slow-conducting nociceptive skin afferents. Here we investigated whether the inhibition of nociceptive sensory information, produced by activation of the sensorimotor cortex, involves a direct presynaptic modulation of C primary afferents. In anaesthetized male Wistar rats, we analyzed the effects of sensorimotor cortex activation on post tetanic potentiation (PTP) and the paired pulse ratio (PPR) of dorsal horn field potentials evoked by C–fiber stimulation in the sural (SU) and sciatic (SC) nerves. We also explored the time course of the excitability changes in nociceptive afferents produced by cortical stimulation. We observed that the development of PTP was completely blocked when C-fiber tetanic stimulation was paired with cortex stimulation. In addition, sensorimotor cortex activation by topical administration of bicuculline (BIC) produced a reduction in the amplitude of C–fiber responses, as well as an increase in the PPR. Furthermore, increases in the intraspinal excitability of slow-conducting fiber terminals, produced by sensorimotor cortex stimulation, were indicative of primary afferent depolarization. Topical administration of BIC in the spinal cord blocked the inhibition of C–fiber neuronal responses produced by cortical stimulation. Dorsal horn neurons responding to sensorimotor cortex stimulation also exhibited a peripheral receptive field and responded to stimulation of fast cutaneous myelinated fibers. Our results suggest that corticospinal inhibition of nociceptive responses is due in part to a modulation of the excitability of primary C–fibers by means of GABAergic inhibitory interneurons.
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Duration of Analgesia Induced by Acupuncture-Like TENS on Experimental Heat Pain. ISRN PAIN 2013; 2013:792383. [PMID: 27335882 PMCID: PMC4893391 DOI: 10.1155/2013/792383] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Accepted: 03/20/2013] [Indexed: 11/17/2022]
Abstract
Background. Acupuncture-like TENS (AL-TENS) is a treatment modality that can be used to temporarily reduce pain. However, there is no clear data in the literature regarding the specific duration of analgesia induced by AL-TENS. Objectives. To describe and quantify the duration and magnitude of AL-TENS analgesia on experimental heat pain in healthy subjects and verify if the duration or magnitude of analgesia induced by the AL-TENS was influenced by the duration of the application of the AL-TENS (15 versus 30 minutes). Methods. A repeated-measures, intrasubject randomized experimental design was used, where each participant was his/her own control. 22 healthy volunteers underwent heat pain stimulations with a contact thermode before (pretest) and after (posttest) AL-TENS application (15 and 30 minutes). Outcome measures included subjective pain during AL-TENS, duration, and magnitude of AL-TENS-induced analgesia. Results. Survival analysis showed that the median duration of AL-TENS analgesia was 10 minutes following the application of either 15 or 30 minutes of AL-TENS. The magnitude of analgesia following either application was comparable at all points in time (P values > 0.05) and ranged between −20% and −36% pain reduction. Conclusion. Only half of the participants still had heat-pain analgesia induced by the AL-TENS at 15 minutes postapplication.
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Suzuki I, Tsuboi Y, Shinoda M, Shibuta K, Honda K, Katagiri A, Kiyomoto M, Sessle BJ, Matsuura S, Ohara K, Urata K, Iwata K. Involvement of ERK phosphorylation of trigeminal spinal subnucleus caudalis neurons in thermal hypersensitivity in rats with infraorbital nerve injury. PLoS One 2013; 8:e57278. [PMID: 23451198 PMCID: PMC3579857 DOI: 10.1371/journal.pone.0057278] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Accepted: 01/23/2013] [Indexed: 01/19/2023] Open
Abstract
To evaluate the involvement of the mitogen-activated protein kinase (MAPK) cascade in orofacial neuropathic pain mechanisms, this study assessed nocifensive behavior evoked by mechanical or thermal stimulation of the whisker pad skin, phosphorylation of extracellular signal-regulated kinase (ERK) in trigeminal spinal subnucleus caudalis (Vc) neurons, and Vc neuronal responses to mechanical or thermal stimulation of the whisker pad skin in rats with the chronic constriction nerve injury of the infraorbital nerve (ION-CCI). The mechanical and thermal nocifensive behavior was significantly enhanced on the side ipsilateral to the ION-CCI compared to the contralateral whisker pad or sham rats. ION-CCI rats had an increased number of phosphorylated ERK immunoreactive (pERK-IR) cells which also manifested NeuN-IR but not GFAP-IR and Iba1-IR, and were significantly more in ION-CCI rats compared with sham rats following noxious but not non-noxious mechanical stimulation. After intrathecal administration of the MEK1 inhibitor PD98059 in ION-CCI rats, the number of pERK-IR cells after noxious stimulation and the enhanced thermal nocifensive behavior but not the mechanical nocifensive behavior were significantly reduced in ION-CCI rats. The enhanced background activities, afterdischarges and responses of wide dynamic range neurons to noxious mechanical and thermal stimulation in ION-CCI rats were significantly depressed following i.t. administration of PD98059, whereas responses to non-noxious mechanical and thermal stimulation were not altered. The present findings suggest that pERK-IR neurons in the Vc play a pivotal role in the development of thermal hypersensitivity in the face following trigeminal nerve injury.
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Affiliation(s)
- Ikuko Suzuki
- Department of Physiology, Nihon University School of Dentistry, Chiyoda-ku Tokyo, Japan
| | - Yoshiyuki Tsuboi
- Department of Physiology, Nihon University School of Dentistry, Chiyoda-ku Tokyo, Japan
| | - Masamichi Shinoda
- Department of Physiology, Nihon University School of Dentistry, Chiyoda-ku Tokyo, Japan
| | - Kazuo Shibuta
- Department of Physiology, Nihon University School of Dentistry, Chiyoda-ku Tokyo, Japan
| | - Kuniya Honda
- Department of Physiology, Nihon University School of Dentistry, Chiyoda-ku Tokyo, Japan
- Department of Oral and Maxillofacial Surgery, Nihon University School of Dentistry, Chiyoda-ku Tokyo, Japan
| | - Ayano Katagiri
- Department of Physiology, Nihon University School of Dentistry, Chiyoda-ku Tokyo, Japan
| | - Masaaki Kiyomoto
- Department of Physiology, Nihon University School of Dentistry, Chiyoda-ku Tokyo, Japan
| | - Barry J. Sessle
- Department of Oral Physiology, Faculty of Dentistry, University of Toronto, Toronto, Ontario, Canada
| | - Shingo Matsuura
- Department of Endodontics, Nihon University School of Dentistry, Chiyoda-ku Tokyo, Japan
| | - Kinuyo Ohara
- Department of Endodontics, Nihon University School of Dentistry, Chiyoda-ku Tokyo, Japan
| | - Kentaro Urata
- Department of Prosthodontics, Nihon University School of Dentistry, Chiyoda-ku Tokyo, Japan
| | - Koichi Iwata
- Department of Physiology, Nihon University School of Dentistry, Chiyoda-ku Tokyo, Japan
- Division of Functional Morphology, Dental Research Center, Nihon University School of Dentistry, Tokyo, Japan
- Division of Applied System Neuroscience Advanced Medical Research Center, Nihon University Graduate School of Medical Science, Tokyo, Japan
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Ohnami S, Kato A, Ogawa K, Shinohara S, Ono H, Tanabe M. Effects of milnacipran, a 5-HT and noradrenaline reuptake inhibitor, on C-fibre-evoked field potentials in spinal long-term potentiation and neuropathic pain. Br J Pharmacol 2013; 167:537-47. [PMID: 22537101 DOI: 10.1111/j.1476-5381.2012.02007.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND AND PURPOSE The analgesic action of 5-HT and noradrenaline reuptake inhibitors (SNRIs) on nociceptive synaptic transmission in the spinal cord is poorly understood. We investigated the effects of milnacipran, an SNRI, on C-fibre-evoked field potentials (FPs) in spinal long-term potentiation (LTP), a proposed synaptic mechanism of hypersensitivity, and on the FPs in a neuropathic pain model. EXPERIMENTAL APPROACH C-fibre-evoked FPs by electrical stimulation of the sciatic nerve fibres were recorded in the spinal dorsal horn of anaesthetized adult rats, and LTP was induced by high-frequency stimulation of the sciatic nerve fibres. A rat model of neuropathic pain was produced by L5 spinal nerve ligation and transection. KEY RESULTS Milnacipran produced prolonged inhibition of C-fibre-evoked FPs when applied spinally after the establishment of LTP of C-fibre-evoked FPs in naïve animals. In the neuropathic pain model, spinal administration of milnacipran clearly reduced the basal C-fibre-evoked FPs. These inhibitory effects of milnacipran were blocked by spinal administration of methysergide, a 5-HT½ receptor antagonist, and yohimbine or idazoxan, α₂-adrenoceptor antagonists. However, spinal administration of milnacipran in naïve animals did not affect the basal C-fibre-evoked FPs and the induction of spinal LTP. CONCLUSION AND IMPLICATIONS Milnacipran inhibited C-fibre-mediated nociceptive synaptic transmission in the spinal dorsal horn after the establishment of spinal LTP and in the neuropathic pain model, by activating both spinal 5-hydroxytryptaminergic and noradrenergic systems. The condition-dependent inhibition of the C-fibre-mediated transmission by milnacipran could provide novel evidence regarding the analgesic mechanisms of SNRIs in chronic pain.
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Affiliation(s)
- S Ohnami
- Laboratory of CNS Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Japan
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64
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Melin C, Jacquot F, Dallel R, Artola A. Segmental disinhibition suppresses C-fiber inputs to the rat superficial medullary dorsal horn via the activation of GABABreceptors. Eur J Neurosci 2012; 37:417-28. [DOI: 10.1111/ejn.12048] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Revised: 09/13/2012] [Accepted: 09/27/2012] [Indexed: 12/17/2022]
Affiliation(s)
| | - Florian Jacquot
- Clermont Université; Université d'Auvergne; Neuro-Dol, BP 10448, F-63000, Clermont-Ferrand & Inserm U1107; F-63001 Clermont-Ferrand; France
| | | | - Alain Artola
- Clermont Université; Université d'Auvergne; Neuro-Dol, BP 10448, F-63000, Clermont-Ferrand & Inserm U1107; F-63001 Clermont-Ferrand; France
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65
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Hoy KC, Huie JR, Grau JW. AMPA receptor mediated behavioral plasticity in the isolated rat spinal cord. Behav Brain Res 2012; 236:319-326. [PMID: 22982187 DOI: 10.1016/j.bbr.2012.09.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Revised: 08/31/2012] [Accepted: 09/05/2012] [Indexed: 12/18/2022]
Abstract
Previous research has demonstrated that the spinal cord is capable of a simple form of instrumental learning. Spinally transected rats that receive shock to a hind leg in an extended position quickly learn to maintain the leg in a flexed position, reducing net shock exposure whenever that leg is flexed. Subjects that receive shock independent of leg position (uncontrollable shock) do not exhibit an increase in flexion duration and later fail to learn when tested with controllable shock (learning deficit). The present study examined the role of the ionotropic glutamate receptor α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) in spinal learning. Intrathecal application of the AMPA receptor antagonist CNQX disrupted performance of a spinal instrumental learning in a dose dependent fashion (Experiment 1). CNQX also disrupted the maintenance of the instrumental response (Experiment 2) and blocked the induction of the learning deficit (Experiment 3). Intrathecal application of the agonist AMPA had a non-monotonic effect, producing a slight facilitation of performance at a low dose and disrupting learning at a high concentration (Experiment 4). Within the dose range tested, intrathecal application of AMPA did not have a long-term effect (Experiment 5). The results suggest that AMPA-mediated transmission plays an essential role in both instrumental learning and the induction of the learning deficit.
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Affiliation(s)
- Kevin C Hoy
- Texas A&M University, College Station, TX 77843-4235, United States.
| | - J Russell Huie
- University of California, San Francisco, CA, United States
| | - James W Grau
- Texas A&M University, College Station, TX 77843-4235, United States
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Bjersing JL, Dehlin M, Erlandsson M, Bokarewa MI, Mannerkorpi K. Changes in pain and insulin-like growth factor 1 in fibromyalgia during exercise: the involvement of cerebrospinal inflammatory factors and neuropeptides. Arthritis Res Ther 2012; 14:R162. [PMID: 22776095 PMCID: PMC3580554 DOI: 10.1186/ar3902] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Accepted: 07/09/2012] [Indexed: 12/12/2022] Open
Abstract
Introduction Fibromyalgia (FM) is characterized by chronic pain. Impaired growth hormone responses and reduced serum insulin-like growth factor 1 (IGF-1) are common in FM. The aim was to examine changes in serum IGF-1, cerebrospinal fluid (CSF), neuropeptides, and cytokines during aerobic exercise in FM patients. Methods In total, 49 patients (median age, 52 years) with FM were included in the study. They were randomized to either the moderate- to high-intensity Nordic Walking (NW) program (n = 26) or the supervised low-intensity walking (LIW) program (n = 23). Patients participated in blood tests before and after 15 weeks of aerobic exercise. Changes in serum levels of free IGF-1, pain rating on a 0- to 100-mm scale, pain threshold, and 6-minute walk test (6MWT) were examined. CSF, neuropeptides, matrix metalloproteinase 3 (MMP-3), and inflammatory cytokines were determined. Nonparametric tests were used for group comparisons and correlation analyses. Results Serum free IGF-1 levels did not change during 15 weeks of exercise between the two groups, although the 6MWT significantly improved in the NW group (p = 0.033) when compared with LIW. Pain did not significantly change in any of the groups, but tended to decrease (p = 0.052) over time in the total group. A tendency toward a correlation was noted between baseline IGF-1 and a decrease of pain in response to exercise (r = 0.278; p = 0.059). When adjusted for age, this tendency disappeared. The change in serum free IGF-1 correlated positively with an alteration in CSF substance P (SP) levels (rs = 0.495; p = 0.072), neuropeptide Y (NPY) (rs = 0.802; p = 0.001), and pain threshold (rs = 0.276; p = 0.058). Differing CSF SP levels correlated positively to a change in pain threshold (rs = 0.600; p = 0.023), whereas the shift in CSF MMP-3 inversely correlated with an altered pain threshold (rs = -0.569; p = 0.034). Conclusions The baseline level of serum free IGF-1 did not change during high or low intensity of aerobic exercise. Changes in IGF-1 correlated positively with a variation in CSF SP, NPY, and pain threshold. These data indicate a beneficial role of IGF-1 during exercise in FM. Trial registration: ClinicalTrials.gov
NCT00643006.
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Chu YX, Zhang YQ, Zhao ZQ. Involvement of microglia and interleukin-18 in the induction of long-term potentiation of spinal nociceptive responses induced by tetanic sciatic stimulation. Neurosci Bull 2012; 28:49-60. [PMID: 22233889 DOI: 10.1007/s12264-012-1058-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
OBJECTIVE The present study aimed to investigate the potential roles of spinal microglia and downstream molecules in the induction of spinal long-term potentiation (LTP) and mechanical allodynia by tetanic stimulation of the sciatic nerve (TSS). METHODS Spinal LTP was induced in adult male Sprague-Dawley rats by tetanic stimulation of the sciatic nerve (0.5 ms, 100 Hz, 40 V, 10 trains of 2-s duration at 10-s intervals). Mechanical allodynia was determined using von Frey hairs. Immunohistochemical staining and Western blot were used to detect changes in glial expression of interleukin-18 (IL-18) and IL-18 receptor (IL-18R). RESULTS TSS induced LTP of C-fiber-evoked field potentials in the spinal cord. Intrathecal administration of the microglial inhibitor minocycline (200 μg/20 μL) 1 h before TSS completely blocked the induction of spinal LTP. Furthermore, after intrathecal injection of minocycline (200 μg/20 μL) by lumbar puncture 1 h before TSS, administration of minocycline for 7 consecutive days (once per day) partly inhibited bilateral allodynia. Immunohistochemistry showed that minocycline inhibited the sequential activation of microglia and astrocytes, and IL-18 was predominantly colocalized with the microglial marker Iba-1 in the spinal superficial dorsal horn. Western blot revealed that repeated intrathecal injection of minocycline significantly inhibited the increased expression of IL-18 and IL-18Rs in microglia induced by TSS. CONCLUSION The IL-18 signaling pathway in microglia is involved in TSS-induced spinal LTP and mechanical allodynia.
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Affiliation(s)
- Yu-Xia Chu
- Institute of Neurobiology, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, China
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68
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Yuan S, Burrell BD. Long-term depression of nociceptive synapses by non-nociceptive afferent activity: role of endocannabinoids, Ca²+, and calcineurin. Brain Res 2012; 1460:1-11. [PMID: 22578358 DOI: 10.1016/j.brainres.2012.04.030] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Revised: 04/16/2012] [Accepted: 04/16/2012] [Indexed: 02/08/2023]
Abstract
Activity in non-nociceptive afferents is known to produce long-lasting decreases in nociceptive signaling, often referred to as gate control, but the cellular mechanisms mediating this form of neuroplasticity are poorly understood. In the leech, activation of non-nociceptive touch (T) mechanosensory neurons induces a heterosynaptic depression of nociceptive (N) synapses that is endocannabinoid-dependent. This heterosynaptic, endocannabinoid-dependent long-term depression (ecLTD) is observed where the T- and N-cells converge on a common postsynaptic target, in this case the motor neuron that innervates the longitudinal muscles (L-cells) that contributes to a defensive withdrawal reflex. Depression in the nociceptive synapse required both presynaptic and postsynaptic increases in intracellular Ca²⁺. Activation of the Ca²⁺-sensitive protein phosphatase calcineurin was also required, but only in the presynaptic neuron. Heterosynaptic ecLTD was unaffected by antagonists for NMDA or metabotropic glutamate receptors, but was blocked by the 5-HT₂ receptor antagonist ritanserin. Depression was also blocked by the CB1 receptor antagonist rimonabant, but this is thought to represent an effect on a TRPV-like receptor. This heterosynaptic, endocannabinoid-dependent modulation of nociceptive synapses represents a novel mechanism for regulating how injury-inducing or painful stimuli are transmitted to the rest of the central nervous system.
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Affiliation(s)
- Sharleen Yuan
- Sanford School of Medicine at The University of South Dakota, Division of Basic Biomedical Sciences, Neuroscience Group, 414 E. Clark Street, Lee Med Bldg, Vermillion, SD, USA
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69
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Lu VB, Colmers WF, Smith PA. Long-term actions of BDNF on inhibitory synaptic transmission in identified neurons of the rat substantia gelatinosa. J Neurophysiol 2012; 108:441-52. [PMID: 22496528 DOI: 10.1152/jn.00457.2011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Peripheral nerve injury promotes the release of brain-derived neurotrophic factor (BDNF) from spinal microglial cells and primary afferent terminals. This induces an increase in dorsal horn excitability that contributes to "central sensitization" and to the onset of neuropathic pain. Although it is accepted that impairment of GABAergic and/or glycinergic inhibition contributes to this process, certain lines of evidence suggest that GABA release in the dorsal horn may increase after nerve injury. To resolve these contradictory findings, we exposed rat spinal cord neurons in defined-medium organotypic culture to 200 ng/ml BDNF for 6 days to mimic the change in spinal BDNF levels that accompanies peripheral nerve injury. Morphological and electrophysiological criteria and glutamic acid decarboxylase (GAD) immunohistochemistry were used to distinguish putative inhibitory tonic-islet-central neurons from putative excitatory delay-radial neurons. Whole cell recording in the presence of 1 μM tetrodotoxin showed that BDNF increased the amplitude of GABAergic and glycinergic miniature inhibitory postsynaptic currents (mIPSCs) in both cell types. It also increased the amplitude and frequency of spontaneous, action potential-dependent IPSCs (sIPSCs) in putative excitatory neurons. By contrast, BDNF reduced sIPSC amplitude in inhibitory neurons but frequency was unchanged. This increase in inhibitory drive to excitatory neurons and decreased inhibitory drive to inhibitory neurons seems inconsistent with the observation that BDNF increases overall dorsal horn excitability. One of several explanations for this discrepancy is that the action of BDNF in the substantia gelatinosa is dominated by previously documented increases in excitatory synaptic transmission rather than by impediment of inhibitory transmission.
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Affiliation(s)
- Van B Lu
- Department of Pharmacology and Centre for Neuroscience, University of Alberta, Edmonton, Alberta, Canada
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70
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Pickar JG, Bolton PS. Spinal manipulative therapy and somatosensory activation. J Electromyogr Kinesiol 2012; 22:785-94. [PMID: 22349622 DOI: 10.1016/j.jelekin.2012.01.015] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Revised: 12/06/2011] [Accepted: 01/23/2012] [Indexed: 10/28/2022] Open
Abstract
Manually-applied movement and mobilization of body parts as a healing activity has been used for centuries. A relatively high velocity, low amplitude force applied to the vertebral column with therapeutic intent, referred to as spinal manipulative therapy (SMT), is one such activity. It is most commonly used by chiropractors, but other healthcare practitioners including osteopaths and physiotherapists also perform SMT. The mechanisms responsible for the therapeutic effects of SMT remain unclear. Early theories proposed that the nervous system mediates the effects of SMT. The goal of this article is to briefly update our knowledge regarding several physical characteristics of an applied SMT, and review what is known about the signaling characteristics of sensory neurons innervating the vertebral column in response to spinal manipulation. Based upon the experimental literature, we propose that SMT may produce a sustained change in the synaptic efficacy of central neurons by evoking a high frequency, bursting discharge from several types of dynamically-sensitive, mechanosensitive paraspinal primary afferent neurons.
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Affiliation(s)
- J G Pickar
- Palmer Center for Chiropractic Research, Palmer College of Chiropractic, Davenport, IA, USA.
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71
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Manresa JAB, Mørch CD, Andersen OK. Long-term facilitation of nociceptive withdrawal reflexes following low-frequency conditioning electrical stimulation: A new model for central sensitization in humans. Eur J Pain 2012; 14:822-31. [DOI: 10.1016/j.ejpain.2009.12.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2009] [Revised: 11/24/2009] [Accepted: 12/21/2009] [Indexed: 01/21/2023]
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72
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Buesa I, Urrutia A, Bilbao J, Aguilera L, Zimmermann M, Azkue JJ. Morphine-induced depression of spinal excitation is not altered following acute disruption of GABAA or GABAB receptor activity. Eur J Pain 2012; 12:677-85. [DOI: 10.1016/j.ejpain.2007.10.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Svendsen F, Tjølsen A, Rykkja F, Hole K. Behavioural effects of LTP-inducing sciatic nerve stimulation in the rat. Eur J Pain 2012. [DOI: 10.1016/s1090-3801(99)90017-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Foley JC, McIver SR, Haydon PG. Gliotransmission modulates baseline mechanical nociception. Mol Pain 2011; 7:93. [PMID: 22136202 PMCID: PMC3248913 DOI: 10.1186/1744-8069-7-93] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Accepted: 12/02/2011] [Indexed: 02/08/2023] Open
Abstract
Pain is a physiological and adaptive process which occurs to protect organisms from tissue damage and extended injury. Pain sensation beyond injury, however, is a pathological process which is poorly understood. Experimental models of neuropathic pain demonstrate that reactive astrocytes contribute to reduced nociceptive thresholds. Astrocytes release "gliotransmitters" such as D-serine, glutamate, and ATP, which is extracellularly hydrolyzed to adenosine. Adenosine 1 receptor activation in the spinal cord has anti-nociceptive effects on baseline pain threshold, but the source of the endogenous ligand (adenosine) in the spinal cord is unknown. In this study we used a transgenic mouse model in which SNARE-mediated gliotransmission was selectively attenuated (called dnSNARE mice) to investigate the role of astrocytes in mediating baseline nociception and the development of neuropathic pain. Under baseline conditions, immunostaining in the dorsal horn of the spinal cord showed astrocyte-specific transgene expression in dnSNARE mice, and no difference in expression levels of the astrocyte marker GFAP and the microglia marker Iba1 relative to wild-type mice. The Von Frey filament test was used to probe sensitivity to baseline mechanical pain thresholds and allodynia following the spared nerve injury model of neuropathic pain. DnSNARE mice exhibit a reduced nociceptive threshold in response to mechanical stimulation compared to wild-type mice under baseline conditions, but nociceptive thresholds following spared nerve injury were similar between dnSNARE and wild-types. This study is the first to provide evidence that gliotransmission contributes to basal mechanical nociception.
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Affiliation(s)
- Jeannine C Foley
- Department of Neuroscience, Tufts University, 136 Harrison Avenue, Boston, Massachusetts 02111, USA
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75
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Sandkühler J, Gruber-Schoffnegger D. Hyperalgesia by synaptic long-term potentiation (LTP): an update. Curr Opin Pharmacol 2011; 12:18-27. [PMID: 22078436 PMCID: PMC3315008 DOI: 10.1016/j.coph.2011.10.018] [Citation(s) in RCA: 125] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Accepted: 10/17/2011] [Indexed: 11/17/2022]
Abstract
Long-term potentiation of synaptic strength (LTP) in nociceptive pathways shares principle features with hyperalgesia including induction protocols, pharmacological profile, neuronal and glial cell types involved and means for prevention. LTP at synapses of nociceptive nerve fibres constitutes a contemporary cellular model for pain amplification following trauma, inflammation, nerve injury or withdrawal from opioids. It provides a novel target for pain therapy. This review summarizes recent progress which has been made in unravelling the properties and functions of LTP in the nociceptive system and in identifying means for its prevention and reversal.
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Affiliation(s)
- Jürgen Sandkühler
- Medical University of Vienna, Center for Brain Research, Department of Neurophysiology, Spitalgasse 4, A-1090 Vienna, Austria.
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76
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van den Broeke EN, van Heck CH, van Rijn CM, Wilder-Smith OH. Neural correlates of heterotopic facilitation induced after high frequency electrical stimulation of nociceptive pathways. Mol Pain 2011; 7:28. [PMID: 21507241 PMCID: PMC3108312 DOI: 10.1186/1744-8069-7-28] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Accepted: 04/20/2011] [Indexed: 11/22/2022] Open
Abstract
Background High frequency electrical stimulation (HFS) of primary nociceptive afferents in humans induce a heightened sensitivity in the surrounding non-stimulated skin area. Several studies suggest that this heterotopic effect is the result of central (spinal) plasticity. The aim of this study is to investigate HFS-induced central plasticity of sensory processing at the level of the brain using the electroencephalogram (EEG). To this end we measured evoked potentials in response to noxious electrical pinprick-like stimuli applied in the heterotopic skin area before, directly after and 30 minutes after HFS. Results We observed potential cortical electrophysiological correlates of heterotopic facilitation. Two different cortical correlates were found; the first one was a lateralized effect, i.e. a larger N100 amplitude on the conditioned arm than the control arm 30 minutes after end of HFS. This was comparable with the observed lateralized effect of visual analogue scale (VAS) scores as response to the mechanical punctate stimuli. The second correlate seems to be a more general (non-lateralized) effect, because the result affects both arms. On average for both arms the P200 amplitude increased significantly 30 minutes after end of HFS with respect to baseline. Conclusions We suggest that for studying heterotopic nociceptive facilitation the evoked brain response is suitable and relevant for investigating plasticity at the level of the brain and is perhaps a more sensitive and reliable marker than the perceived pain intensity (e.g. VAS).
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Affiliation(s)
- Emanuel N van den Broeke
- Department of Anesthesiology, Pain & Palliative Medicine, Pain & Nociception Neuroscience Research Group, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
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Francis RP, Marchant P, Johnson MI. Conventional versus acupuncture-like transcutaneous electrical nerve stimulation on cold-induced pain in healthy human participants: effects during stimulation. Clin Physiol Funct Imaging 2011; 31:363-70. [PMID: 21771255 DOI: 10.1111/j.1475-097x.2011.01025.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVES To compare the hypoalgesic effects of conventional transcutaneous electrical nerve stimulation (TENS) (high frequency, low intensity) and acupuncture-like TENS (AL-TENS, low frequency, high intensity) on cold-induced pain. DESIGN Randomized controlled parallel group study comparing the effects of strong non-painful AL-TENS, conventional TENS and placebo (no current) TENS on cold-pressor pain threshold (CPT) and pain intensity. Two baseline (pre-intervention) measures and three during intervention measures of CPT and cold pain intensity (four point category scale) were recorded. SETTING Physiology laboratory in Leeds Metropolitan University. PARTICIPANTS One hundred and twenty-one healthy participants. INTERVENTIONS Each participant received one of three TENS interventions over their flexor digitorum profundus: (i) high pulse rate TENS with a strong non-painful paraesthesia (conventional), (ii) low-rate burst mode TENS that caused strong non-painful phasic muscle twitching (acupuncture like) or (iii) no current (placebo) TENS. MAIN OUTCOME MEASURE Difference between conventional TENS and AL-TENS in cold pain threshold relative to pre-TENS baseline after 25 min of stimulation. RESULTS No differences were detected for CPT or cold pain intensity during conventional TENS compared with AL-TENS. When compared with placebo TENS, the confidence intervals for the ratio of intervention CPT to baseline CPT, for both AL-TENS (0·966, 1·424) and conventional TENS (0·948, 1·401), were close to the positive side of one, although neither reached statistical significance. CONCLUSIONS Unlike some previous studies, the present study detected no differences in hypoalgesia between AL-TENS, conventional TENS and placebo (no current) TENS during stimulation.
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Affiliation(s)
- Richard P Francis
- Centre for Pain Research, Faculty of Health, Leeds Metropolitan University, Leeds, UK.
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Ruscheweyh R, Wilder-Smith O, Drdla R, Liu XG, Sandkühler J. Long-term potentiation in spinal nociceptive pathways as a novel target for pain therapy. Mol Pain 2011; 7:20. [PMID: 21443797 PMCID: PMC3078873 DOI: 10.1186/1744-8069-7-20] [Citation(s) in RCA: 160] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Accepted: 03/28/2011] [Indexed: 01/19/2023] Open
Abstract
Long-term potentiation (LTP) in nociceptive spinal pathways shares several features with hyperalgesia and has been proposed to be a cellular mechanism of pain amplification in acute and chronic pain states. Spinal LTP is typically induced by noxious input and has therefore been hypothesized to contribute to acute postoperative pain and to forms of chronic pain that develop from an initial painful event, peripheral inflammation or neuropathy. Under this assumption, preventing LTP induction may help to prevent the development of exaggerated postoperative pain and reversing established LTP may help to treat patients who have an LTP component to their chronic pain. Spinal LTP is also induced by abrupt opioid withdrawal, making it a possible mechanism of some forms of opioid-induced hyperalgesia. Here, we give an overview of targets for preventing LTP induction and modifying established LTP as identified in animal studies. We discuss which of the various symptoms of human experimental and clinical pain may be manifestations of spinal LTP, review the pharmacology of these possible human LTP manifestations and compare it to the pharmacology of spinal LTP in rodents.
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Affiliation(s)
- Ruth Ruscheweyh
- Department of Neurophysiology, Center for Brain Research, Medical University of Vienna, Vienna, Austria
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79
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Schomburg ED, Dibaj P, Steffens H. Differentiation between Aδ and C fibre evoked nociceptive reflexes by TTX resistance and opioid sensitivity in the cat. Neurosci Res 2011; 69:241-5. [PMID: 21147180 DOI: 10.1016/j.neures.2010.12.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Revised: 11/24/2010] [Accepted: 12/05/2010] [Indexed: 11/27/2022]
MESH Headings
- Analgesics/pharmacology
- Analgesics, Opioid/pharmacology
- Anesthetics, Local/pharmacology
- Animals
- Cats
- Dose-Response Relationship, Drug
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-/pharmacology
- Enkephalin, Leucine/analogs & derivatives
- Enkephalin, Leucine/pharmacology
- Excitatory Postsynaptic Potentials/drug effects
- Female
- Foot/innervation
- Male
- Naloxone/pharmacology
- Narcotic Antagonists/pharmacology
- Nerve Fibers, Myelinated/drug effects
- Nerve Fibers, Myelinated/physiology
- Nerve Fibers, Unmyelinated/drug effects
- Nerve Fibers, Unmyelinated/physiology
- Nociceptors/drug effects
- Nociceptors/physiology
- Reflex/drug effects
- Spinal Cord/cytology
- Tetrodotoxin/pharmacology
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Affiliation(s)
- Eike D Schomburg
- Institute of Physiology, Georg August University of Göttingen, Waldweg 33, D-37073 Göttingen, Germany.
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80
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Fukushima T, Takasusuki T, Tomitori H, Hori Y. Possible involvement of syntaxin 1A downregulation in the late phase of allodynia induced by peripheral nerve injury. Neuroscience 2011; 175:344-57. [DOI: 10.1016/j.neuroscience.2010.11.049] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2010] [Revised: 11/11/2010] [Accepted: 11/22/2010] [Indexed: 11/16/2022]
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Role of voltage-dependent calcium channel subtypes in spinal long-term potentiation of C-fiber-evoked field potentials. Pain 2011; 152:623-631. [PMID: 21211907 DOI: 10.1016/j.pain.2010.12.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2010] [Revised: 12/01/2010] [Accepted: 12/02/2010] [Indexed: 11/20/2022]
Abstract
Activity-dependent increases in the responsiveness of spinal neurons to their normal afferent input, termed central sensitization, have been suggested to play a key role in abnormal pain sensation. We investigated the role of distinct voltage-dependent calcium channel (VDCC) subtypes in the long-term potentiation (LTP) of C-fiber-evoked field potentials (FPs) recorded in the spinal dorsal horn of rats, that is, a synaptic model to describe central sensitization. When spinally applied, we observed that omega-conotoxin GVIA (ω-CgTx), an N-type VDCC antagonist, produced a dose-dependent and prolonged inhibition of basal C-fiber-evoked FPs in naïve animals. ω-CgTx did not perturb the induction of LTP by high-frequency stimulation (HFS) of the sciatic nerve; however, potentiation was maintained at a lower level. Following the establishment of spinal LTP in naïve animals, the inhibitory effect of ω-CgTx on C-fiber-evoked FPs was significantly increased. Furthermore, in animals with chronic pain produced via peripheral nerve injury, where spinal LTP was barely induced by HFS, basal C-fiber-evoked FPs were strongly inhibited by ω-CgTx. As a result, ω-CgTx exerted a similar inhibitory profile on C-fiber-evoked FPs following the establishment of spinal LTP and chronic pain. In contrast, spinally administered omega-agatoxin IVA (ω-Aga-IVA), a P/Q-type VDCC antagonist, showed little effect on C-fiber-evoked FPs either before or after the establishment of LTP, but strongly suppressed LTP induction. These results demonstrate the requirement of N- and P/Q-type VDCCs in the maintenance and induction of LTP in the spinal dorsal horn, respectively, and their distinct contribution to nociceptive synaptic transmission and its plasticity. In vivo electrophysiological studies demonstrate the distinct and predominant functions of voltage-dependent calcium channel subtypes for spinal long-term potentiation and chronic pain.
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Liang L, Wang Z, Lü N, Yang J, Zhang Y, Zhao Z. Involvement of nerve injury and activation of peripheral glial cells in tetanic sciatic stimulation-induced persistent pain in rats. J Neurosci Res 2010; 88:2899-910. [PMID: 20544834 DOI: 10.1002/jnr.22439] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Tetanic stimulation of the sciatic nerve (TSS) produces long-lasting pain hypersensitivity in rats. Long-term potentiation (LTP) of C- and A-fiber-evoked field potentials in the spinal cord has been explored as contributing to central sensitization in pain pathways. However, the peripheral mechanism underlying TSS-induced pain hypersensitivity remains largely unknown. We investigated the effect of TSS on peripheral nerve and the expression of activating transcription factor 3 (ATF3) in dorsal root ganglion (DRG) as a marker of neuronal injury. TSS induced a mechanical allodynia for at least 35 days and induced ATF3 expression in the ipsilateral DRG. ATF3 is colocalized with NF200-labeled myelinated DRG neurons or CGRP- and IB4-labeled unmyelinated ones. Furthermore, we found that TSS induced Wallerian degeneration of sciatic nerve at the level of myelinisation by S100 protein (to label Schwann cells) immunohistochemistry, luxol fast blue staining, and electron microscopy. TSS also elicited the activation of satellite glial cells (SGCs) and enhanced the colocalization of GFAP and P2X7 receptors. Repeated local treatment with tetrodotoxin decreased GFAP expression in SGCs and behavioral allodynia induced by TSS. Furthermore, reactive microglia and astrocytes were found in the spinal dorsal horn after TSS. These results suggest that TSS-induced nerve injury and glial activation in the DRG and spinal dorsal horn may be involved in cellular mechanisms underlying the development of persistent pain after TSS and that TSS-induced nerve injury may be used as a novel neuropathic pain model.
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Affiliation(s)
- Lingli Liang
- Institute of Neurobiology, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, China
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83
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Chu YX, Zhang Y, Zhang YQ, Zhao ZQ. Involvement of microglial P2X7 receptors and downstream signaling pathways in long-term potentiation of spinal nociceptive responses. Brain Behav Immun 2010; 24:1176-89. [PMID: 20554014 DOI: 10.1016/j.bbi.2010.06.001] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2010] [Revised: 05/21/2010] [Accepted: 06/02/2010] [Indexed: 12/23/2022] Open
Abstract
Tetanic stimulation of the sciatic nerve (TSS) produces long-term potentiation (LTP) of C-fiber-evoked field potentials in the spinal cord. This potentiation is considered to be a substrate for long-lasting sensitization in the spinal pain pathway. Because microglia have previously been shown to regulate the induction of spinal LTP, we hypothesize that P2X7 receptors (P2X7R), which are predominantly expressed in microglia and participate in the communication between microglia and neurons, may play a role in this induction. This study investigated the potential roles of P2X7Rs in spinal LTP and persistent pain induced by TSS in rats. OxATP or BBG, a P2X7R antagonist, prevented the induction of spinal LTP both in vivo and in spinal cord slices in vitro and alleviated mechanical allodynia. Down-regulation of P2X7Rs with P2X7-siRNA blocked the induction of spinal LTP and inhibited mechanical allodynia. Double immunofluorescence showed colocalization of P2X7Rs with the microglial marker OX-42, but not with the astrocytic marker GFAP or the neuronal marker NeuN. Intrathecal injection of BBG suppressed the up-regulation of microglial P2X7Rs and increased expression of Fos in the spinal superficial dorsal horn. Further, pre-administration of BBG inhibited increased expression of the microglial marker Iba-1, phosphorylated p38 (p-p38), interleukin 1β (IL-1β) and GluR1 following TSS. Pre-administration of the IL-1 receptor antagonist (IL-1ra) blocked both the induction of spinal LTP and the up-regulation of GluR1. These results suggest that microglial P2X7Rs and its downstream signaling pathways play a pivotal role in the induction of spinal LTP and persistent pain induced by TSS.
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Affiliation(s)
- Yu-Xia Chu
- Institute of Neurobiology, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, China
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84
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85
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Gong QJ, Li YY, Xin WJ, Wei XH, Cui Y, Wang J, Liu Y, Liu CC, Li YY, Liu XG. Differential effects of adenosine A1 receptor on pain-related behavior in normal and nerve-injured rats. Brain Res 2010; 1361:23-30. [PMID: 20850420 DOI: 10.1016/j.brainres.2010.09.034] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2010] [Revised: 09/08/2010] [Accepted: 09/08/2010] [Indexed: 11/16/2022]
Abstract
This study investigated the effects of N6-cyclopentyladenosine (CPA), a potent and selective adenosine A1 receptor (A1R) agonist in normal and nerve-injured rats and mechanisms of its action by behavioral tests and electrophysiological technique. The results showed: (1) In normal rats, intraperitoneal administration of CPA (1mg/kg) increased paw withdrawal latencies, in a way blocked by a selective A1R antagonist 8-cyclopentyl-1, 3-dipropylxanthine (DPCPX, 3mg/kg, i.p.), but had no influence on the threshold of mechanical stimulation. (2) In rats with neuropathic pain induced by spinal nerve ligation (SNL), CPA reduced thermal hyperalgesia and mechanical allodynia, which could last 6h and 10h, respectively (n=6/group, P<0.05). Both of the effects could be blocked by pretreatment of DPCPX intraperitoneally. (3) The baseline of C-fiber but not A-fiber evoked field potentials was depressed by spinal application of CPA (0.01 mM), and this effect was prevented by application of DPCPX (0.02 mM) 30 min before CPA. (4) Spinal application of CPA depressed long-term potentiation (LTP) of A- and C-fiber evoked field potentials, and both the depression could be blocked by pretreatment of DPCPX 30 min before CPA. These results suggested that the activation of A1R has different influences on normal and neuropathic rats probably due to the absence and presence of central sensitization in spinal dorsal horn.
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Affiliation(s)
- Qing-Juan Gong
- Department of Physiology and Pain Research Center, Zhongshan Medical School, Sun Yat-Sen University, 74 Zhongshan Rd 2, Guangzhou 510080, China
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86
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Rojas-Piloni G, Martínez-Lorenzana G, Condés-Lara M, Rodríguez-Jiménez J. Direct sensorimotor corticospinal modulation of dorsal horn neuronal C-fiber responses in the rat. Brain Res 2010; 1351:104-114. [DOI: 10.1016/j.brainres.2010.06.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2010] [Revised: 05/12/2010] [Accepted: 06/03/2010] [Indexed: 11/27/2022]
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87
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Sandkühler J. Central Sensitization Versus Synaptic Long-Term Potentiation (LTP): A Critical Comment. THE JOURNAL OF PAIN 2010; 11:798-800. [DOI: 10.1016/j.jpain.2010.05.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2010] [Revised: 04/01/2010] [Indexed: 11/16/2022]
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88
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Zhong Y, Zhou LJ, Ren WJ, Xin WJ, Li YY, Zhang T, Liu XG. The direction of synaptic plasticity mediated by C-fibers in spinal dorsal horn is decided by Src-family kinases in microglia: the role of tumor necrosis factor-alpha. Brain Behav Immun 2010; 24:874-80. [PMID: 20116424 DOI: 10.1016/j.bbi.2010.01.007] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Revised: 01/16/2010] [Accepted: 01/19/2010] [Indexed: 12/27/2022] Open
Abstract
Previous studies have shown that Src-family kinases (SFKs) are selectively activated in spinal microglia following peripheral nerve injury and the activated SFKs play a key role for the development of neuropathic pain. To investigate the underlying mechanism, in the present study the effect of SFKs on long-term potentiation (LTP) at C-fiber synapses in spinal dorsal horn, which is believed as central mechanism of neuropathic pain, was investigated in adult rats. Electrophysiological data revealed that pretreatment with either microglia inhibitor (minocycline, 200 microM) or SFKs inhibitors (PP2, 100 microM and SU6656, 200 microM) reversed the effect of high frequency stimulation (HFS), that is, HFS, which induces long-term potentiation (LTP) normally, induced long-term depression (LTD) after inhibition of either microglia or SFKs. Western blotting analysis showed that the level of phosphorylated SFKs (p-SFKs) in ipsilateral spinal dorsal horn was transiently increased after LTP induced by HFS, starting at 15 min and returning to control level at 60 min after HFS. Double-labeled immunofluorescence staining demonstrated that p-SFKs were highly restricted to microglia. Furthermore, we found that the inhibitory effects of minocycline or SU6656 on spinal LTP were reversed by spinal application of rat recombinant tumor necrosis factor-alpha (TNF-alpha 0.5 ng/ml, 200 microl). HFS failed to induce LTP of C-fiber evoked field potentials in TNF receptor-1 knockout mice and in rats pretreated with TNF-alpha neutralization antibody (0.6 microg/ml, 200 microl). The results suggested that in spinal dorsal horn activation of SFKs in microglia might control the direction of plastic changes at C-fiber synapses and TNF-alpha might be involved in the process.
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Affiliation(s)
- Yi Zhong
- Pain Research Center, Department of Physiology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
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89
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Expression of the immediate-early gene egr-1 and substance P in the spinal cord following locomotor training in adult rats. Brain Res 2010; 1345:125-36. [PMID: 20546710 DOI: 10.1016/j.brainres.2010.05.041] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2009] [Revised: 05/13/2010] [Accepted: 05/14/2010] [Indexed: 01/09/2023]
Abstract
The immediate-early gene egr-1 has been shown to have an increased expression during long-term potentiation (LTP). High frequency electrical stimulation induces an increase in such expression in the dorsal horn of the spinal cord. However, evidence demonstrating the activation of this gene in the spinal cord and its relationship with LTP is still scarce. The substance P (SP) has also been associated with LTP in the dorsal horn of the spinal cord following high frequency stimulation. Here we evaluated the expression of both Egr-1 and SP in the sacrolumbar area of the spinal cord after locomotor training in adult rats. Increased neuronal Egr-1 expression was found in the spinal cord sections in rats that underwent locomotor training, especially in laminae IV and X across L3-S4 levels (p<0.05). Conversely, SP expression in synaptic terminals was not altered in the abovementioned regions. Our results suggest that locomotor training activates mechanisms in a similar way to LTP, and is involved in the synaptic plasticity in the spinal cord. The results also indicate that variations in the training protocol influence Egr-1 expression. Such events appear not to be directly influenced by SP, which suggests a plastic process that differs from those triggered by nociceptive stimuli.
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90
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Leung L, Cahill CM. TNF-alpha and neuropathic pain--a review. J Neuroinflammation 2010; 7:27. [PMID: 20398373 PMCID: PMC2861665 DOI: 10.1186/1742-2094-7-27] [Citation(s) in RCA: 430] [Impact Index Per Article: 30.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2009] [Accepted: 04/16/2010] [Indexed: 12/12/2022] Open
Abstract
Tumor necrosis factor alpha (TNF-α) was discovered more than a century ago, and its known roles have extended from within the immune system to include a neuro-inflammatory domain in the nervous system. Neuropathic pain is a recognized type of pathological pain where nociceptive responses persist beyond the resolution of damage to the nerve or its surrounding tissue. Very often, neuropathic pain is disproportionately enhanced in intensity (hyperalgesia) or altered in modality (hyperpathia or allodynia) in relation to the stimuli. At time of this writing, there is as yet no common consensus about the etiology of neuropathic pain - possible mechanisms can be categorized into peripheral sensitization and central sensitization of the nervous system in response to the nociceptive stimuli. Animal models of neuropathic pain based on various types of nerve injuries (peripheral versus spinal nerve, ligation versus chronic constrictive injury) have persistently implicated a pivotal role for TNF-α at both peripheral and central levels of sensitization. Despite a lack of success in clinical trials of anti-TNF-α therapy in alleviating the sciatic type of neuropathic pain, the intricate link of TNF-α with other neuro-inflammatory signaling systems (e.g., chemokines and p38 MAPK) has indeed inspired a systems approach perspective for future drug development in treating neuropathic pain.
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Affiliation(s)
- Lawrence Leung
- Centre for Neurosciences Studies, 18, Stuart Street, Queen's University, Kingston, Ontario K7L 3N6, Canada.
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91
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van den Broeke EN, van Rijn CM, Biurrun Manresa JA, Andersen OK, Arendt-Nielsen L, Wilder-Smith OHG. Neurophysiological Correlates of Nociceptive Heterosynaptic Long-Term Potentiation in Humans. J Neurophysiol 2010; 103:2107-13. [DOI: 10.1152/jn.00979.2009] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Long-term potentiation (LTP) is a cellular model of synaptic plasticity and reflects an increase of synaptic strength. LTP is also present in the nociceptive system and is believed to be one of the key mechanisms involved in the manifestations of chronic pain. LTP manifested as an increased response in pain perception can be induced in humans using high-frequency electrical stimulation (HFS). The aim of this study was to induce spinal heterosynaptic LTP using HFS and investigate its heterotopic effects on event-related potentials (ERPs) to repeated nonpainful cutaneous stimuli as a possible electrophysiological cortical correlate of sensitization. Twenty-two healthy subjects were randomly assigned to one of the two experimental conditions: HFS and control stimulation. Before and after the stimulation, both conditions received heterotopic mechanical (pinprick) and paired nonpainful electrical test stimuli to quantify and confirm the effects of HFS on the behavioral level. ERPs to paired nonpainful electrical stimulation were measured simultaneously. Conditioning HFS resulted in significant heterotopic effects after 30 min, including increased perceived intensity in response to (pinprick) mechanical and paired nonpainful electrical stimulation compared with control. The paired nonpainful electrical stimuli were accompanied by significantly enhanced responses regarding the ERP N1-P2 peak-to-peak and P300 amplitude compared with control. These findings suggest that HFS is capable of producing heterosynaptic spinal LTP that can be measured not only behaviorally but also using ERPs.
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Affiliation(s)
- Emanuel N. van den Broeke
- Department of Anesthesiology, Pain and Palliative Medicine, Pain and Nociception Neuroscience Research Group, Radboud University Nijmegen Medical Centre
| | - Clementina M. van Rijn
- Donders Institute for Brain, Cognition and Behavior, Radboud University Nijmegen, Nijmegen, The Netherlands; and
| | - José A. Biurrun Manresa
- Centre for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
| | - Ole K. Andersen
- Centre for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
| | - Lars Arendt-Nielsen
- Centre for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
| | - Oliver H. G. Wilder-Smith
- Department of Anesthesiology, Pain and Palliative Medicine, Pain and Nociception Neuroscience Research Group, Radboud University Nijmegen Medical Centre
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92
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LeBlanc BW, Iwata M, Mallon AP, Rupasinghe CN, Goebel DJ, Marshall J, Spaller MR, Saab CY. A cyclic peptide targeted against PSD-95 blocks central sensitization and attenuates thermal hyperalgesia. Neuroscience 2010; 167:490-500. [PMID: 20167266 DOI: 10.1016/j.neuroscience.2010.02.031] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Revised: 02/09/2010] [Accepted: 02/11/2010] [Indexed: 12/29/2022]
Abstract
Post-synaptic density protein PSD-95 is emerging as a valid target for modulating nociception in animal studies. Based on the key role of PSD-95 in neuronal plasticity and the maintenance of pain behavior, we predicted that CN2097, a peptide-based macrocycle of nine residues that binds to the PSD-95 Discs large, Zona occludens 1 (PDZ) domains of PSD-95, would interfere with physiologic phenomena in the spinal cord related to central sensitization. Furthermore, we tested whether spinal intrathecal injection of CN2097 attenuates thermal hyperalgesia in a rat model of sciatic neuropathy. Results demonstrate that spinal CN2097 reverses hyperexcitability of wide dynamic range (WDR) neurons in the dorsal horn of neuropathic rats and decreases their evoked responses to peripheral stimuli (brush, low caliber von Frey and pressure), whereas CN5125 ("negative control") has no effect. CN2097 also blocks C-fiber long-term potentiation (LTP) in the dorsal horn, which is linked to neuronal plasticity and central sensitization. At a molecular level, CN2097 attenuates the increase in phosphorylated p38 MAPK, a key intracellular signaling pathway in neuropathic pain. Moreover, spinal injection of CN2097 blocks thermal hyperalgesia in neuropathic rats. We conclude that CN2097 is a small molecule peptide with putative anti-nociceptive effects that modulates physiologic phenomena related to central sensitization under conditions of chronic pain.
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Affiliation(s)
- B W LeBlanc
- Department of Surgery, Rhode Island Hospital, Brown Alpert Medical School and Department of Neuroscience, Brown University, Providence, RI 02903, USA
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93
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Lee KY, Chung K, Chung JM. Involvement of reactive oxygen species in long-term potentiation in the spinal cord dorsal horn. J Neurophysiol 2009; 103:382-91. [PMID: 19906875 DOI: 10.1152/jn.90906.2008] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Recent studies suggest that reactive oxygen species (ROS) are functional messenger molecules in central sensitization, an underlying mechanism of persistent pain. Because spinal cord long-term potentiation (LTP) is the electrophysiological basis of central sensitization, this study investigates the effects of the increased or decreased spinal ROS levels on spinal cord LTP. Spinal cord LTP is induced by either brief, high-frequency stimulation (HFS) of a dorsal root at C-fiber intensity or superfusion of a ROS donor, tert-butyl hydroperoxide (t-BOOH), onto rat spinal cord slice preparations. Field excitatory postsynaptic potentials (fEPSPs) evoked by dorsal root stimulations with either Abeta- or C-fiber intensity are recorded from the superficial dorsal horn. HFS significantly increases the slope of both Abeta- and C-fiber evoked fEPSPs, thus suggesting LTP development. The induction, not the maintenance, of HFS-induced LTP is blocked by a N-methyl-D-aspartate (NMDA) receptor antagonist, D-2-amino-5-phosphonopentanoic acid (D-AP5). Both the induction and maintenance of LTP of Abeta-fiber-evoked fEPSPs are inhibited by a ROS scavenger, either N-tert-butyl-alpha-phenylnitrone or 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl. A ROS donor, t-BOOH-induced LTP is inhibited by N-tert-butyl-alpha-phenylnitrone but not by D-AP5. Furthermore, HFS-induced LTP and t-BOOH-induced LTP occlude each other. The data suggest that elevated ROS is a downstream event of NMDA receptor activation and an essential step for potentiation of synaptic excitability in the spinal dorsal horn.
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Affiliation(s)
- Kwan Yeop Lee
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, 310 University Blvd., Galveston, TX 77555-1069, USA
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94
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Larsson M. Ionotropic glutamate receptors in spinal nociceptive processing. Mol Neurobiol 2009; 40:260-88. [PMID: 19876771 DOI: 10.1007/s12035-009-8086-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2009] [Accepted: 09/29/2009] [Indexed: 02/07/2023]
Abstract
Glutamate is the predominant excitatory transmitter used by primary afferent synapses and intrinsic neurons in the spinal cord dorsal horn. Accordingly, ionotropic glutamate receptors mediate basal spinal transmission of sensory, including nociceptive, information that is relayed to supraspinal centers. However, it has become gradually more evident that these receptors are also crucially involved in short- and long-term plasticity of spinal nociceptive transmission, and that such plasticity have an important role in the pain hypersensitivity that may result from tissue or nerve injury. This review will cover recent findings on pre- and postsynaptic regulation of synaptic function by ionotropic glutamate receptors in the dorsal horn and how such mechanisms contribute to acute and chronic pain.
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Affiliation(s)
- Max Larsson
- Department of Anatomy and Centre for Molecular Biology and Neuroscience, University of Oslo, Norway.
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95
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Zhao XY, Liu MG, Yuan DL, Wang Y, He Y, Wang DD, Chen XF, Zhang FK, Li H, He XS, Chen J. Nociception-induced spatial and temporal plasticity of synaptic connection and function in the hippocampal formation of rats: a multi-electrode array recording. Mol Pain 2009; 5:55. [PMID: 19772643 PMCID: PMC2759921 DOI: 10.1186/1744-8069-5-55] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2009] [Accepted: 09/22/2009] [Indexed: 12/12/2022] Open
Abstract
Background Pain is known to be processed by a complex neural network (neuromatrix) in the brain. It is hypothesized that under pathological state, persistent or chronic pain can affect various higher brain functions through ascending pathways, leading to co-morbidities or mental disability of pain. However, so far the influences of pathological pain on the higher brain functions are less clear and this may hinder the advances in pain therapy. In the current study, we studied spatiotemporal plasticity of synaptic connection and function in the hippocampal formation (HF) in response to persistent nociception. Results On the hippocampal slices of rats which had suffered from persistent nociception for 2 h by receiving subcutaneous bee venom (BV) or formalin injection into one hand paw, multisite recordings were performed by an 8 × 8 multi-electrode array probe. The waveform of the field excitatory postsynaptic potential (fEPSP), induced by perforant path electrical stimulation and pharmacologically identified as being activity-dependent and mediated by ionotropic glutamate receptors, was consistently positive-going in the dentate gyrus (DG), while that in the CA1 was negative-going in shape in naïve and saline control groups. For the spatial characteristics of synaptic plasticity, BV- or formalin-induced persistent pain significantly increased the number of detectable fEPSP in both DG and CA1 area, implicating enlargement of the synaptic connection size by the injury or acute inflammation. Moreover, the input-output function of synaptic efficacy was shown to be distinctly enhanced by the injury with the stimulus-response curve being moved leftward compared to the control. For the temporal plasticity, long-term potentiation produced by theta burst stimulation (TBS) conditioning was also remarkably enhanced by pain. Moreover, it is strikingly noted that the shape of fEPSP waveform was drastically deformed or split by a TBS conditioning under the condition of persistent nociception, while that in naïve or saline control state was not affected. All these changes in synaptic connection and function, confirmed by the 2-dimentional current source density imaging, were found to be highly correlated with peripheral persistent nociception since pre-blockade of nociceptive impulses could eliminate all of them. Finally, the initial pharmacological investigation showed that AMPA/KA glutamate receptors might play more important roles in mediation of pain-associated spatiotemporal plasticity than NMDA receptors. Conclusion Peripheral persistent nociception produces great impact upon the higher brain structures that lead to not only temporal plasticity, but also spatial plasticity of synaptic connection and function in the HF. The spatial plasticity of synaptic activities is more complex than the temporal plasticity, comprising of enlargement of synaptic connection size at network level, deformed fEPSP at local circuit level and, increased synaptic efficacy at cellular level. In addition, the multi-synaptic model established in the present investigation may open a new avenue for future studies of pain-related brain dysfunctions at the higher level of the neuromatrix.
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Affiliation(s)
- Xiao-Yan Zhao
- Institute for Biomedical Sciences of Pain, Capital Medical University, Beijing, PR China.
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96
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Paraventricular oxytocinergic hypothalamic prevention or interruption of long-term potentiation in dorsal horn nociceptive neurons: Electrophysiological and behavioral evidence. Pain 2009; 144:320-328. [DOI: 10.1016/j.pain.2009.05.002] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2008] [Revised: 04/23/2009] [Accepted: 05/01/2009] [Indexed: 11/22/2022]
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97
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Liu WT, Han Y, Li HC, Adams B, Zheng JH, Wu YP, Henkemeyer M, Song XJ. An in vivo mouse model of long-term potentiation at synapses between primary afferent C-fibers and spinal dorsal horn neurons: essential role of EphB1 receptor. Mol Pain 2009; 5:29. [PMID: 19523204 PMCID: PMC2704201 DOI: 10.1186/1744-8069-5-29] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2009] [Accepted: 06/12/2009] [Indexed: 11/10/2022] Open
Abstract
Background Long-term potentiation (LTP), a much studied cellular model of synaptic plasticity, has not been demonstrated at synapses between primary afferent C-fibers and spinal dorsal horn (DH) neurons in mice in vivo. EphrinB-EphB receptor signaling plays important roles in synaptic connection and plasticity in the nervous system, but its role in spinal synaptic plasticity remains unclear. Results This study characterizes properties of LTP at synapses of C-fibers onto neurons in the superficial DH following high-frequency stimulation (HFS) of a peripheral nerve at an intensity that activates C-fibers and examines associated activation of Ca2+/calmodulin-activated protein kinase II (p-CaMKII), extracellular signal-regulated kinase (p-ERK) and the cyclic AMP response element binding protein (p-CREB) and expression of c-Fos, and it investigates further roles for the EphB1 receptor in LTP. HFS induced LTP within 5 min and lasts for 3–8 h during the period of recording and resulted in upregulation of p-CaMKII, p-ERK and p-CREB protein levels in the spinal cord and expression of c-Fos in DH. Intrathecal pretreatment of MK-801 or EphB2-Fc prevented LTP and significantly reduced upregulation of p-CaMKII, p-ERK, p-CREB and c-Fos. Further, targeted mutation of EphB1 receptor prevented induction of LTP and associated increases in phosphorylation of CaMKII, ERK, and CREB. Conclusion This study provides an in vivo mouse model of LTP at synapses of C-fibers onto the superficial DH neurons that will be valuable for studying the DH neuron excitability and their synaptic plasticity and hyperalgesia. It further takes advantage of examining functional implications of a specific gene targeted mice and demonstrates that the EphB1 receptor is essential for development of LTP.
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Affiliation(s)
- Wen-Tao Liu
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical College, Xuzhou, Jiangsu, PR China.
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98
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Pain and learning in a spinal system: contradictory outcomes from common origins. ACTA ACUST UNITED AC 2009; 61:124-43. [PMID: 19481111 DOI: 10.1016/j.brainresrev.2009.05.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2008] [Revised: 03/18/2009] [Accepted: 05/19/2009] [Indexed: 11/21/2022]
Abstract
The long-standing belief that the spinal cord serves merely as a conduit for information traveling to and from the brain is changing. Over the past decade, research has shown that the spinal cord is sensitive to response-outcome contingencies, demonstrating that spinal circuits have the capacity to modify behavior in response to differential environmental cues. If spinally transected rats are administered shock contingent on leg extension (controllable shock), they will maintain a flexion response that minimizes shock exposure. If, however, this contingency is broken, and shock is administered irrespective of limb position (uncontrollable shock), subjects cannot acquire the same flexion response. Interestingly, each of these treatments has a lasting effect on behavior; controllable shock enables future learning, while uncontrollable shock produces a long-lasting learning deficit. Here we suggest that the mechanisms underlying learning and the deficit may have evolved from machinery responsible for the spinal processing of noxious information. Experiments have shown that learning and the deficit require receptors and signaling cascades shown to be involved in central sensitization, including activation of NMDA and neurokinin receptors, as well as CaMKII. Further supporting this link between pain and learning, research has also shown that uncontrollable stimulation results in allodynia. Moreover, systemic inflammation and neonatal hindpaw injury each facilitate pain responding and undermine the ability of the spinal cord to support learning. These results suggest that the plasticity associated with learning and pain must be placed in a balance in order for adaptive outcomes to be observed.
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99
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Abstract
Hyperalgesia and allodynia are frequent symptoms of disease and may be useful adaptations to protect vulnerable tissues. Both may, however, also emerge as diseases in their own right. Considerable progress has been made in developing clinically relevant animal models for identifying the most significant underlying mechanisms. This review deals with experimental models that are currently used to measure (sect. II) or to induce (sect. III) hyperalgesia and allodynia in animals. Induction and expression of hyperalgesia and allodynia are context sensitive. This is discussed in section IV. Neuronal and nonneuronal cell populations have been identified that are indispensable for the induction and/or the expression of hyperalgesia and allodynia as summarized in section V. This review focuses on highly topical spinal mechanisms of hyperalgesia and allodynia including intrinsic and synaptic plasticity, the modulation of inhibitory control (sect. VI), and neuroimmune interactions (sect. VII). The scientific use of language improves also in the field of pain research. Refined definitions of some technical terms including the new definitions of hyperalgesia and allodynia by the International Association for the Study of Pain are illustrated and annotated in section I.
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Affiliation(s)
- Jürgen Sandkühler
- Department of Neurophysiology, Center for Brain Research, Medical University of Vienna, Vienna, Austria
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100
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Namjoshi DR, McErlane SA, Taepavarapruk N, Soja PJ. Network actions of pentobarbital in the rat mesopontine tegmentum on sensory inflow through the spinothalamic tract. J Neurophysiol 2009; 102:700-13. [PMID: 19458144 DOI: 10.1152/jn.90933.2008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The recent discovery of a barbiturate-sensitive "general anesthesia switch" mechanism localized in the rat brain stem mesopontine tegmental anesthesia area (MPTA) has challenged the current view of the nonspecific actions of general anesthetic agents in the CNS. In this study we provide electrophysiological evidence that the antinociception, which accompanies the behavioral state resembling general anesthesia following pentobarbital (PB) microinjections into the MPTA of awake rats, could be accompanied by the attenuation of sensory transmission through the spinothalamic tract (STT). Following bilateral microinjections of PB into the MPTA spontaneous firing rate (SFR), antidromic firing index (FI), and sciatic (Sc) as well as sural (Su) nerve-evoked responses (ER) of identified lumbar STT neurons in the isoflurane-anesthetized rat were quantified using extracellular recording techniques. Microinjections of PB into the MPTA significantly suppressed the SFR (47%), magnitudes of Sc- (26%) and Su-ER (36%), and FI (41%) of STT neurons. Microinjections of PB-free vehicle control did not alter any of the above-cited electrophysiological parameters. The results from this study suggest that antinociception, which occurs during the anesthesia-like state following PB microinjections into the MPTA, may be due, in part, to (in)direct inhibition of STT neurons via switching mechanism(s) located in the MPTA. This study provides a provenance for investigating electrophysiologically the actions on STT neurons of other current agents used clinically to maintain the state of general anesthesia.
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Affiliation(s)
- Dhananjay R Namjoshi
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
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