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Yang W, Yaggie RE, Schaeffer AJ, Klumpp DJ. AOAH remodels arachidonic acid-containing phospholipid pools in a model of interstitial cystitis pain: A MAPP Network study. PLoS One 2020; 15:e0235384. [PMID: 32925915 PMCID: PMC7489500 DOI: 10.1371/journal.pone.0235384] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Accepted: 06/15/2020] [Indexed: 01/10/2023] Open
Abstract
Interstitial cystitis/bladder pain syndrome (IC) is a debilitating condition of chronic pelvic pain with unknown etiology. Recently, we used a genetic approach in a murine model of IC to identify the lipase acyloxyacyl hydrolase (AOAH) as a modulator of pelvic pain. We found that AOAH-deficient mice have elevated pelvic pain responses, and AOAH immunoreactivity was detected along the bladder-brain axis. Lipidomic analyses identified arachidonic acid (AA) and its metabolite PGE2 as significantly elevated in the sacral spinal cord of AOAH-deficient mice, suggesting AA is a substrate for AOAH. Here, we quantified the effects of AOAH on phospholipids containing AA. Spinal cord lipidomics revealed increased AA-containing phosphatidylcholine in AOAH-deficient mice and concomitantly decreased AA-phosphatidylethanolamine, consistent with decreased CoA-independent transferase activity (CoIT). Overexpression of AOAH in cell cultures similarly altered distribution of AA in phospholipid pools, promoted AA incorporation, and resulted in decreased membrane fluidity. Finally, administration of a PGE2 receptor antagonist reduced pelvic pain in AOAH-deficient mice. Together, these findings suggest that AOAH represents a potential CoA-independent AA transferase that modulates CNS pain pathways at the level of phospholipid metabolism.
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Affiliation(s)
- Wenbin Yang
- Department of Urology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States of America
| | - Ryan E. Yaggie
- Department of Urology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States of America
| | - Anthony J. Schaeffer
- Department of Urology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States of America
| | - David J. Klumpp
- Department of Urology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States of America
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States of America
- * E-mail:
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Guida F, De Gregorio D, Palazzo E, Ricciardi F, Boccella S, Belardo C, Iannotta M, Infantino R, Formato F, Marabese I, Luongo L, de Novellis V, Maione S. Behavioral, Biochemical and Electrophysiological Changes in Spared Nerve Injury Model of Neuropathic Pain. Int J Mol Sci 2020; 21:ijms21093396. [PMID: 32403385 PMCID: PMC7246983 DOI: 10.3390/ijms21093396] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2020] [Revised: 04/27/2020] [Accepted: 05/06/2020] [Indexed: 01/05/2023] Open
Abstract
Neuropathic pain is a pathological condition induced by a lesion or disease affecting the somatosensory system, with symptoms like allodynia and hyperalgesia. It has a multifaceted pathogenesis as it implicates several molecular signaling pathways involving peripheral and central nervous systems. Affective and cognitive dysfunctions have been reported as comorbidities of neuropathic pain states, supporting the notion that pain and mood disorders share some common pathogenetic mechanisms. The understanding of these pathophysiological mechanisms requires the development of animal models mimicking, as far as possible, clinical neuropathic pain symptoms. Among them, the Spared Nerve Injury (SNI) model has been largely characterized in terms of behavioral and functional alterations. This model is associated with changes in neuronal firing activity at spinal and supraspinal levels, and induces late neuropsychiatric disorders (such as anxious-like and depressive-like behaviors, and cognitive impairments) comparable to an advanced phase of neuropathy. The goal of this review is to summarize current findings in preclinical research, employing the SNI model as a tool for identifying pathophysiological mechanisms of neuropathic pain and testing pharmacological agent.
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Affiliation(s)
- Francesca Guida
- Department of Experimental Medicine, Division of Pharmacology, University of Campania Naples, 80138 Naples, Italy; (E.P.); (F.R.); (S.B.); (C.B.); (M.I.); (R.I.); (F.F.); (I.M.); (L.L.); (V.d.N.)
- Correspondence: (F.G.); (S.M.)
| | - Danilo De Gregorio
- Neurobiological Psychiatry Unit, Department of Psychiatry, McGill University, Montréal, QC H3A1A1, Canada;
| | - Enza Palazzo
- Department of Experimental Medicine, Division of Pharmacology, University of Campania Naples, 80138 Naples, Italy; (E.P.); (F.R.); (S.B.); (C.B.); (M.I.); (R.I.); (F.F.); (I.M.); (L.L.); (V.d.N.)
| | - Flavia Ricciardi
- Department of Experimental Medicine, Division of Pharmacology, University of Campania Naples, 80138 Naples, Italy; (E.P.); (F.R.); (S.B.); (C.B.); (M.I.); (R.I.); (F.F.); (I.M.); (L.L.); (V.d.N.)
| | - Serena Boccella
- Department of Experimental Medicine, Division of Pharmacology, University of Campania Naples, 80138 Naples, Italy; (E.P.); (F.R.); (S.B.); (C.B.); (M.I.); (R.I.); (F.F.); (I.M.); (L.L.); (V.d.N.)
| | - Carmela Belardo
- Department of Experimental Medicine, Division of Pharmacology, University of Campania Naples, 80138 Naples, Italy; (E.P.); (F.R.); (S.B.); (C.B.); (M.I.); (R.I.); (F.F.); (I.M.); (L.L.); (V.d.N.)
| | - Monica Iannotta
- Department of Experimental Medicine, Division of Pharmacology, University of Campania Naples, 80138 Naples, Italy; (E.P.); (F.R.); (S.B.); (C.B.); (M.I.); (R.I.); (F.F.); (I.M.); (L.L.); (V.d.N.)
| | - Rosmara Infantino
- Department of Experimental Medicine, Division of Pharmacology, University of Campania Naples, 80138 Naples, Italy; (E.P.); (F.R.); (S.B.); (C.B.); (M.I.); (R.I.); (F.F.); (I.M.); (L.L.); (V.d.N.)
| | - Federica Formato
- Department of Experimental Medicine, Division of Pharmacology, University of Campania Naples, 80138 Naples, Italy; (E.P.); (F.R.); (S.B.); (C.B.); (M.I.); (R.I.); (F.F.); (I.M.); (L.L.); (V.d.N.)
| | - Ida Marabese
- Department of Experimental Medicine, Division of Pharmacology, University of Campania Naples, 80138 Naples, Italy; (E.P.); (F.R.); (S.B.); (C.B.); (M.I.); (R.I.); (F.F.); (I.M.); (L.L.); (V.d.N.)
| | - Livio Luongo
- Department of Experimental Medicine, Division of Pharmacology, University of Campania Naples, 80138 Naples, Italy; (E.P.); (F.R.); (S.B.); (C.B.); (M.I.); (R.I.); (F.F.); (I.M.); (L.L.); (V.d.N.)
| | - Vito de Novellis
- Department of Experimental Medicine, Division of Pharmacology, University of Campania Naples, 80138 Naples, Italy; (E.P.); (F.R.); (S.B.); (C.B.); (M.I.); (R.I.); (F.F.); (I.M.); (L.L.); (V.d.N.)
| | - Sabatino Maione
- Department of Experimental Medicine, Division of Pharmacology, University of Campania Naples, 80138 Naples, Italy; (E.P.); (F.R.); (S.B.); (C.B.); (M.I.); (R.I.); (F.F.); (I.M.); (L.L.); (V.d.N.)
- Correspondence: (F.G.); (S.M.)
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Wang W, Zhong X, Li Y, Guo R, Du S, Wen L, Ying Y, Yang T, Wei X. Rostral ventromedial medulla‐mediated descending facilitation following P2X7 receptor activation is involved in the development of chronic post‐operative pain. J Neurochem 2019; 149:760-780. [DOI: 10.1111/jnc.14650] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 10/14/2018] [Accepted: 12/12/2018] [Indexed: 12/30/2022]
Affiliation(s)
- Wei Wang
- Department of Physiology and Pain Research Center Zhongshan School of Medicine Sun Yat‐sen University Guangzhou Guangdong People's Republic of China
| | - Xiongxiong Zhong
- Department of Physiology and Pain Research Center Zhongshan School of Medicine Sun Yat‐sen University Guangzhou Guangdong People's Republic of China
| | - Yongyong Li
- Department of Physiology and Pain Research Center Zhongshan School of Medicine Sun Yat‐sen University Guangzhou Guangdong People's Republic of China
| | - Ruixian Guo
- Department of Physiology and Pain Research Center Zhongshan School of Medicine Sun Yat‐sen University Guangzhou Guangdong People's Republic of China
- Guangdong Provincial Key Laboratory of Brain Function and Disease Guangzhou Guangdong People's Republic of China
| | - Sujuan Du
- Department of Anesthesiology Sun Yat‐sen Memorial Hospital Sun Yat‐sen University Guangzhou China
| | - Lili Wen
- Department of Anesthesiology Cancer Center State Key Laboratory of Oncology in South China Collaborative, Innovation Center for Cancer Medicine Sun Yat‐sen University Guangzhou P. R. China
| | - Yanlu Ying
- Department of Anesthesiology Guangzhou First People's Hospital Guangzhou Medical University Guangzhou China
| | - Tao Yang
- Department of Anesthesiology Sun Yat‐sen Memorial Hospital Sun Yat‐sen University Guangzhou China
| | - Xu‐Hong Wei
- Department of Physiology and Pain Research Center Zhongshan School of Medicine Sun Yat‐sen University Guangzhou Guangdong People's Republic of China
- Guangdong Provincial Key Laboratory of Brain Function and Disease Guangzhou Guangdong People's Republic of China
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Umana IC, Daniele CA, Miller BA, Abburi C, Gallagher K, Brown MA, Mason P, McGehee DS. Nicotinic modulation of descending pain control circuitry. Pain 2017; 158:1938-50. [PMID: 28817416 DOI: 10.1097/j.pain.0000000000000993] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Along with the well-known rewarding effects, activation of nicotinic acetylcholine receptors (nAChRs) can also relieve pain, and some nicotinic agonists have analgesic efficacy similar to opioids. A major target of analgesic drugs is the descending pain modulatory pathway, including the ventrolateral periaqueductal gray (vlPAG) and the rostral ventromedial medulla (RVM). Although activating nAChRs within this circuitry can be analgesic, little is known about the subunit composition and cellular effects of these receptors, particularly within the vlPAG. Using electrophysiology in brain slices from adult male rats, we examined nAChR effects on vlPAG neurons that project to the RVM. We found that 63% of PAG-RVM projection neurons expressed functional nAChRs, which were exclusively of the α7-subtype. Interestingly, the neurons that express α7 nAChRs were largely nonoverlapping with those expressing μ-opioid receptors (MOR). As nAChRs are excitatory and MORs are inhibitory, these data suggest distinct roles for these neuronal classes in pain modulation. Along with direct excitation, we also found that presynaptic nAChRs enhanced GABAergic release preferentially onto neurons that lacked α7 nAChRs. In addition, presynaptic nAChRs enhanced glutamatergic inputs onto all PAG-RVM projection neuron classes to a similar extent. In behavioral testing, both systemic and intra-vlPAG administration of the α7 nAChR-selective agonist, PHA-543,613, was antinociceptive in the formalin assay. Furthermore, intra-vlPAG α7 antagonist pretreatment blocked PHA-543,613-induced antinociception via either administration method. Systemic administration of submaximal doses of the α7 agonist and morphine produced additive antinociceptive effects. Together, our findings indicate that the vlPAG is a key site of action for α7 nAChR-mediated antinociception.
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Li Z, Yin P, Chen J, Jin S, Liu J, Luo F. CaMKIIα may modulate fentanyl-induced hyperalgesia via a CeLC-PAG-RVM-spinal cord descending facilitative pain pathway in rats. PLoS One 2017; 12:e0177412. [PMID: 28489932 PMCID: PMC5425219 DOI: 10.1371/journal.pone.0177412] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 04/26/2017] [Indexed: 11/30/2022] Open
Abstract
Each of the lateral capsular division of central nucleus of amygdala(CeLC), periaqueductal gray (PAG), rostral ventromedial medulla(RVM) and spinal cord has been proved to contribute to the development of opioid-induced hyperalgesia(OIH). Especially, Ca2+/calmodulin-dependent protein kinase IIα (CaMKIIα) in CeLC and spinal cord seems to play a key role in OIH modulation. However, the pain pathway through which CaMKIIα modulates OIH is not clear. The pathway from CeLC to spinal cord for this modulation was explored in the present study. Mechanical and thermal hyperalgesia were tested by von Frey test or Hargreaves test, respectively. CaMKIIα activity (phospho-CaMKIIα, p-CaMKIIα) was evaluated by western blot analysis. CaMKIIα antagonist (KN93) was micro-infused into CeLC, spinal cord or PAG, respectively, to evaluate its effect on behavioral hyperalgesia and p-CaMKIIα expression in CeLC, PAG, RVM and spinal cord. Then the underlying synaptic mechanism was explored by recording miniature excitatory postsynaptic currents (mEPSCs) on PAG slices using whole-cell voltage-clamp methods. Results showed that inhibition of CeLC, PAG or spinal CaMKIIα activity respectively by KN93, reversed both mechanical and thermal hyperalgesia. Microinjection of KN93 into CeLC decreased p-CaMKIIα expression in CeLC, PAG, RVM and spinal cord; while intrathecal KN93 can only block spinal but not CeLC CaMKIIα activity. KN93 injected into PAG just decreased p-CaMKIIα expression in PAG, RVM and spinal cord, but not in the CeLC. Similarly, whole-cell voltage-clamp recording found the frequency and amplitude of mEPSCs in PAG cells were decreased by KN93 added in PAG slice or micro-infused into CeLC in vivo. These results together with previous findings suggest that CaMKIIα may modulate OIH via a CeLC-PAG-RVM-spinal cord descending facilitative pain pathway.
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Affiliation(s)
- Zhen Li
- Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Pingping Yin
- Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jian Chen
- The Laboratory of Membrane Ion Channels and Medicine, Key Laboratory of Cognitive Science, State Ethnic Affairs Commission, College of Biomedical Engineering, South-Central University for Nationalities, Wuhan, China
| | - Shenglan Jin
- Department of Anesthesiology, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jieqiong Liu
- Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Fang Luo
- Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
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Drake RAR, Leith JL, Almahasneh F, Martindale J, Wilson AW, Lumb B, Donaldson LF. Periaqueductal Grey EP3 Receptors Facilitate Spinal Nociception in Arthritic Secondary Hypersensitivity. J Neurosci 2016; 36:9026-40. [PMID: 27581447 PMCID: PMC5005717 DOI: 10.1523/jneurosci.4393-15.2016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Revised: 06/17/2016] [Accepted: 06/22/2016] [Indexed: 02/06/2023] Open
Abstract
UNLABELLED Descending controls on spinal nociceptive processing play a pivotal role in shaping the pain experience after tissue injury. Secondary hypersensitivity develops within undamaged tissue adjacent and distant to damaged sites. Spinal neuronal pools innervating regions of secondary hypersensitivity are dominated by descending facilitation that amplifies spinal inputs from unsensitized peripheral nociceptors. Cyclooxygenase-prostaglandin (PG) E2 signaling within the ventrolateral periaqueductal gray (vlPAG) is pronociceptive in naive and acutely inflamed animals, but its contributions in more prolonged inflammation and, importantly, secondary hypersensitivity remain unknown. In naive rats, PG EP3 receptor (EP3R) antagonism in vlPAG modulated noxious withdrawal reflex (EMG) thresholds to preferential C-nociceptor, but not A-nociceptor, activation and raised thermal withdrawal thresholds in awake animals. In rats with inflammatory arthritis, secondary mechanical and thermal hypersensitivity of the hindpaw developed and was associated with spinal sensitization to A-nociceptor inputs alone. In arthritic rats, blockade of vlPAG EP3R raised EMG thresholds to C-nociceptor activation in the area of secondary hypersensitivity to a degree equivalent to that evoked by the same manipulation in naive rats. Importantly, vlPAG EP3R blockade also affected responses to A-nociceptor activation, but only in arthritic animals. We conclude that vlPAG EP3R activity exerts an equivalent facilitation on the spinal processing of C-nociceptor inputs in naive and arthritic animals, but gains in effects on spinal A-nociceptor processing from a region of secondary hypersensitivity. Therefore, the spinal sensitization to A-nociceptor inputs associated with secondary hypersensitivity is likely to be at least partly dependent on descending prostanergic facilitation from the vlPAG. SIGNIFICANCE STATEMENT After tissue damage, sensitivity to painful stimulation develops in undamaged areas (secondary hypersensitivity). This is found in many painful conditions, particularly arthritis. The periaqueductal gray (PAG) is an important center that controls spinal nociceptive processing, on which secondary hypersensitivity depends. Prostaglandins (PGs) are mediators of inflammation with pronociceptive actions within the PAG under normal conditions. We find that secondary hindpaw hypersensitivity in arthritic rats results from spinal sensitization to peripheral A-nociceptor inputs. In the PAG of arthritic, but not naive, rats, there is enhanced control of spinal A-nociceptor processing through PG EP3 receptors. The descending facilitatory actions of intra-PAG PGs play a direct and central role in the maintenance of inflammatory secondary hypersensitivity, particularly relating to the processing of A-fiber nociceptive information.
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MESH Headings
- Animals
- Anti-Inflammatory Agents, Non-Steroidal/pharmacology
- Area Under Curve
- Arthritis/chemically induced
- Arthritis/complications
- Disease Models, Animal
- Freund's Adjuvant/toxicity
- Hyperalgesia/physiopathology
- Ketoprofen/pharmacology
- Male
- Nerve Fibers, Myelinated/physiology
- Nerve Fibers, Unmyelinated/physiology
- Neurons/drug effects
- Nitriles/pharmacology
- Nociception/drug effects
- Nociception/physiology
- Pain Measurement/methods
- Pain Threshold/physiology
- Periaqueductal Gray/drug effects
- Periaqueductal Gray/metabolism
- RNA, Messenger/metabolism
- Rats
- Rats, Wistar
- Receptors, Prostaglandin E, EP3 Subtype/antagonists & inhibitors
- Receptors, Prostaglandin E, EP3 Subtype/metabolism
- Spinal Cord/metabolism
- Spinal Cord/pathology
- Statistics, Nonparametric
- Sulfonamides/pharmacology
- Time Factors
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Affiliation(s)
- R A R Drake
- School of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - J L Leith
- School of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - F Almahasneh
- Arthritis Research UK Pain Centre and School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, United Kingdom, and
| | - J Martindale
- Neurosciences CEDD, GlaxoSmithKline, Harlow CM19 5AW, United Kingdom
| | - A W Wilson
- Neurosciences CEDD, GlaxoSmithKline, Harlow CM19 5AW, United Kingdom
| | - B Lumb
- School of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - L F Donaldson
- School of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, United Kingdom, Arthritis Research UK Pain Centre and School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, United Kingdom, and
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Maione S, Radanova L, De Gregorio D, Luongo L, De Petrocellis L, Di Marzo V, Imming P. Effects of metabolites of the analgesic agent dipyrone (metamizol) on rostral ventromedial medulla cell activity in mice. Eur J Pharmacol 2015; 748:115-22. [DOI: 10.1016/j.ejphar.2014.12.022] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 11/13/2014] [Accepted: 12/15/2014] [Indexed: 01/15/2023]
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Leith JL, Wilson AW, You HJ, Lumb BM, Donaldson LF. Periaqueductal grey cyclooxygenase-dependent facilitation of C-nociceptive drive and encoding in dorsal horn neurons in the rat. J Physiol 2014; 592:5093-107. [PMID: 25239460 PMCID: PMC4241027 DOI: 10.1113/jphysiol.2014.275909] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2014] [Accepted: 09/10/2014] [Indexed: 12/22/2022] Open
Abstract
The experience of pain is strongly affected by descending control systems originating in the brainstem ventrolateral periaqueductal grey (VL-PAG), which control the spinal processing of nociceptive information. A- and C-fibre nociceptors detect noxious stimulation, and have distinct and independent contributions to both the perception of pain quality (fast and slow pain, respectively) and the development of chronic pain. Evidence suggests a separation in the central processing of information arising from A- vs. C-nociceptors; for example, inhibition of the cyclooxygenase-1 (COX-1)-prostaglandin system within the VL-PAG alters spinal nociceptive reflexes evoked by C-nociceptor input in vivo via descending pathways, leaving A-nociceptor-evoked reflexes largely unaffected. As the spinal neuronal mechanisms underlying these different responses remain unknown, we determined the effect of inhibition of VL-PAG COX-1 on dorsal horn wide dynamic-range neurons evoked by C- vs. A-nociceptor activation. Inhibition of VL-PAG COX-1 in anaesthetised rats increased firing thresholds of lamina IV-V wide dynamic-range dorsal horn neurons in response to both A- and C-nociceptor stimulation. Importantly, wide dynamic-range dorsal horn neurons continued to faithfully encode A-nociceptive information, even after VL-PAG COX-1 inhibition, whereas the encoding of C-nociceptor information by wide dynamic-range spinal neurons was significantly disrupted. Dorsal horn neurons with stronger C-nociceptor input were affected by COX-1 inhibition to a greater extent than those with weak C-fibre input. These data show that the gain and contrast of C-nociceptive information processed in individual wide dynamic-range dorsal horn neurons is modulated by prostanergic descending control mechanisms in the VL-PAG.
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Affiliation(s)
- J Lianne Leith
- School of Physiology & Pharmacology, University of Bristol, Bristol, BS8 1TD, UK
| | - Alex W Wilson
- Neurosciences CEDD, GlaxoSmithKline, Harlow, Essex, CM19 5AW, UK
| | - Hao-Jun You
- Center for Biomedical Research on Pain (CBRP), College of Medicine, Xi'an Jiaotong University, Xi'an, 710061, PR China
| | - Bridget M Lumb
- School of Physiology & Pharmacology, University of Bristol, Bristol, BS8 1TD, UK
| | - Lucy F Donaldson
- School of Physiology & Pharmacology, University of Bristol, Bristol, BS8 1TD, UK Arthritis Research UK Pain Centre, School of Life Sciences, QMC, University of Nottingham, Nottingham, NG7 2UH, UK
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Hu SSJ, Ho YC, Chiou LC. No more pain upon Gq-protein-coupled receptor activation: role of endocannabinoids. Eur J Neurosci 2014; 39:467-84. [PMID: 24494686 DOI: 10.1111/ejn.12475] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2013] [Revised: 12/02/2013] [Accepted: 12/05/2013] [Indexed: 01/24/2023]
Abstract
Marijuana has been used to relieve pain for centuries. The analgesic mechanism of its constituents, the cannabinoids, was only revealed after the discovery of cannabinoid receptors (CB1 and CB2) two decades ago. The subsequent identification of the endocannabinoids, anandamide and 2-arachidonoylglycerol (2-AG), and their biosynthetic and degradation enzymes discloses the therapeutic potential of compounds targeting the endocannabinoid system for pain control. Inhibitors of the anandamide and 2-AG degradation enzymes, fatty acid amide hydrolase and monoacylglycerol lipase, respectively, may be superior to direct cannabinoid receptor ligands as endocannabinoids are synthesized on demand and rapidly degraded, focusing action at generating sites. Recently, a promising strategy for pain relief was revealed in the periaqueductal gray (PAG). It is initiated by Gq-protein-coupled receptor (Gq PCR) activation of the phospholipase C-diacylglycerol lipase enzymatic cascade, generating 2-AG that produces inhibition of GABAergic transmission (disinhibition) in the PAG, thereby leading to analgesia. Here, we introduce the antinociceptive properties of exogenous cannabinoids and endocannabinoids, involving their biosynthesis and degradation processes, particularly in the PAG. We also review recent studies disclosing the Gq PCR-phospholipase C-diacylglycerol lipase-2-AG retrograde disinhibition mechanism in the PAG, induced by activating several Gq PCRs, including metabotropic glutamatergic (type 5 metabotropic glutamate receptor), muscarinic acetylcholine (M1/M3), and orexin 1 receptors. Disinhibition mediated by type 5 metabotropic glutamate receptor can be initiated by glutamate transporter inhibitors or indirectly by substance P, neurotensin, cholecystokinin and capsaicin. Finally, the putative role of 2-AG generated after activating the above neurotransmitter receptors in stress-induced analgesia is discussed.
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Affiliation(s)
- Sherry Shu-Jung Hu
- Department of Psychology, National Cheng Kung University, Tainan, Taiwan
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10
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Drake RAR, Hulse RP, Lumb BM, Donaldson LF. The degree of acute descending control of spinal nociception in an area of primary hyperalgesia is dependent on the peripheral domain of afferent input. J Physiol 2014; 592:3611-24. [PMID: 24879873 PMCID: PMC4229351 DOI: 10.1113/jphysiol.2013.266494] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Descending controls of spinal nociceptive processing play a critical role in the development of inflammatory hyperalgesia. Acute peripheral nociceptor sensitization drives spinal sensitization and activates spino–supraspinal–spinal loops leading to descending inhibitory and facilitatory controls of spinal neuronal activity that further modify the extent and degree of the pain state. The afferent inputs from hairy and glabrous skin are distinct with respect to both the profile of primary afferent classes and the degree of their peripheral sensitization. It is not known whether these differences in afferent input differentially engage descending control systems to different extents or in different ways. Injection of complete Freund's adjuvant resulted in inflammation and swelling of hairy hind foot skin in rats, a transient thermal hyperalgesia lasting <2 h, and longlasting primary mechanical hyperalgesia (≥7 days). Much longer lasting thermal hyperalgesia was apparent in glabrous skin (1 h to >72 h). In hairy skin, transient hyperalgesia was associated with sensitization of withdrawal reflexes to thermal activation of either A- or C-nociceptors. The transience of the hyperalgesia was attributable to a rapidly engaged descending inhibitory noradrenergic mechanism, which affected withdrawal responses to both A- and C-nociceptor activation and this could be reversed by intrathecal administration of yohimbine (α-2-adrenoceptor antagonist). In glabrous skin, yohimbine had no effect on an equivalent thermal inflammatory hyperalgesia. We conclude that acute inflammation and peripheral nociceptor sensitization in hind foot hairy skin, but not glabrous skin, rapidly activates a descending inhibitory noradrenergic system. This may result from differences in the engagement of descending control systems following sensitization of different primary afferent classes that innervate glabrous and hairy skin.
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Affiliation(s)
- Robert A R Drake
- School of Physiology and Pharmacology, University of Bristol, Bristol, UK
| | - Richard P Hulse
- Cancer Biology, School of Medicine, University of Nottingham, Nottingham, UK
| | - Bridget M Lumb
- School of Physiology and Pharmacology, University of Bristol, Bristol, UK
| | - Lucy F Donaldson
- School of Physiology and Pharmacology, University of Bristol, Bristol, UK Arthritis Research UK Pain Centre, School of Life Sciences, University of Nottingham, Nottingham, UK
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