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De Preter CC, Heinricher MM. The 'in's and out's' of descending pain modulation from the rostral ventromedial medulla. Trends Neurosci 2024; 47:447-460. [PMID: 38749825 PMCID: PMC11168876 DOI: 10.1016/j.tins.2024.04.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Revised: 04/12/2024] [Accepted: 04/21/2024] [Indexed: 06/14/2024]
Abstract
The descending-pain modulating circuit controls the experience of pain by modulating transmission of sensory signals through the dorsal horn. This circuit's key output node, the rostral ventromedial medulla (RVM), integrates 'top-down' and 'bottom-up' inputs that regulate functionally defined RVM cell types, 'OFF-cells' and 'ON-cells', which respectively suppress or facilitate pain-related sensory processing. While recent advances have sought molecular definition of RVM cell types, conflicting behavioral findings highlight challenges involved in aligning functional and molecularly defined types. This review summarizes current understanding, derived primarily from rodent studies but with corroborating evidence from human imaging, of the role of RVM populations in pain modulation and persistent pain states and explores recent advances outlining inputs to, and outputs from, RVM pain-modulating neurons.
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Affiliation(s)
- Caitlynn C De Preter
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR 97239, USA; Department of Neurological Surgery, Oregon Health & Science University, Portland, OR 97239, USA
| | - Mary M Heinricher
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR 97239, USA; Department of Neurological Surgery, Oregon Health & Science University, Portland, OR 97239, USA.
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2
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Rogness VM, Juliette J, Khasabova IA, Gupta K, Khasabov SG, Simone DA. Descending Facilitation of Nociceptive Transmission From the Rostral Ventromedial Medulla Contributes to Hyperalgesia in Mice with Sickle Cell Disease. Neuroscience 2023; 526:1-12. [PMID: 37330194 PMCID: PMC10528639 DOI: 10.1016/j.neuroscience.2023.06.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Revised: 05/26/2023] [Accepted: 06/09/2023] [Indexed: 06/19/2023]
Abstract
Sickle cell disease (SCD) is an inherited blood disorder that is associated with acute episodic and chronic pain. Mice with SCD have robust hyperalgesia mediated, in part, by sensitization of spinal dorsal horn neurons. However, underlying mechanisms are not fully understood. Since the rostral ventromedial medulla (RVM) is a major component of descending circuitry that modulates nociceptive transmission in the spinal cord, we examined if the RVM contributes to hyperalgesia in mice with SCD. Injection of lidocaine, but not vehicle, into the RVM eliminated mechanical and heat hyperalgesia in sickle (HbSS-BERK) mice without altering mechanical and heat sensitivity in naïve C57B mice. These data indicate that the RVM contributes to the maintenance of hyperalgesia in mice with SCD. In electrophysiological studies, we determined the changes in response properties of RVM neurons that might contribute to hyperalgesia in sickle mice. Recordings were made from single ON, OFF, and Neutral cells in the RVM of sickle and control (HbAA-BERK) mice. Spontaneous activity and responses of ON, OFF and Neutral cells evoked by heat (50 °C) and mechanical (26 g) stimuli applied to the hind paw were compared between sickle and control mice. Although there were no differences in the proportions of functionally-identified neurons or spontaneous activity between sickle and control mice, evoked responses of ON cells to heat and mechanical stimuli were increased approximately 3-fold in sickle mice as compared to control mice. Thus, the RVM contributes to hyperalgesia in sickle mice via a specific ON cell-dependent descending facilitation of nociceptive transmission.
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Affiliation(s)
- Victoria M Rogness
- Department of Diagnostic & Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN 55455, USA
| | - Joseph Juliette
- Department of Diagnostic & Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN 55455, USA
| | - Iryna A Khasabova
- Department of Diagnostic & Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN 55455, USA
| | - Kalpna Gupta
- Hematology/Oncology, Department of Medicine, University of California, Irvine and Southern California Institute for Research and Education, VA Medical Center, Long Beach, CA, USA
| | - Sergey G Khasabov
- Department of Diagnostic & Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN 55455, USA
| | - Donald A Simone
- Department of Diagnostic & Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN 55455, USA.
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Oikawa I, Kondo S, Hashimoto K, Yoshida A, Hamajima M, Tanimoto H, Furukubo-Tokunaga K, Honjo K. A descending inhibitory mechanism of nociception mediated by an evolutionarily conserved neuropeptide system in Drosophila. eLife 2023; 12:RP85760. [PMID: 37310871 DOI: 10.7554/elife.85760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023] Open
Abstract
Nociception is a neural process that animals have developed to avoid potentially tissue-damaging stimuli. While nociception is triggered in the peripheral nervous system, its modulation by the central nervous system is a critical process in mammals, whose dysfunction has been extensively implicated in chronic pain pathogenesis. The peripheral mechanisms of nociception are largely conserved across the animal kingdom. However, it is unclear whether the brain-mediated modulation is also conserved in non-mammalian species. Here, we show that Drosophila has a descending inhibitory mechanism of nociception from the brain, mediated by the neuropeptide Drosulfakinin (DSK), a homolog of cholecystokinin (CCK) that plays an important role in the descending control of nociception in mammals. We found that mutants lacking dsk or its receptors are hypersensitive to noxious heat. Through a combination of genetic, behavioral, histological, and Ca2+ imaging analyses, we subsequently revealed neurons involved in DSK-mediated nociceptive regulation at a single-cell resolution and identified a DSKergic descending neuronal pathway that inhibits nociception. This study provides the first evidence for a descending modulatory mechanism of nociception from the brain in a non-mammalian species that is mediated by the evolutionarily conserved CCK system, raising the possibility that the descending inhibition is an ancient mechanism to regulate nociception.
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Affiliation(s)
- Izumi Oikawa
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| | - Shu Kondo
- Faculty of Advanced Engineering, Tokyo University of Science, Katsushika-ku, Tokyo, Japan
| | - Kao Hashimoto
- College of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| | - Akiho Yoshida
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| | - Megumi Hamajima
- Center for Development of Advanced Medicine for Dementia, National Center for Geriatrics and Gerontology, Obu, Japan
| | - Hiromu Tanimoto
- Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | | | - Ken Honjo
- Center for Development of Advanced Medicine for Dementia, National Center for Geriatrics and Gerontology, Obu, Japan
- Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
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Pagliusi M, Gomes FV. The Role of The Rostral Ventromedial Medulla in Stress Responses. Brain Sci 2023; 13:brainsci13050776. [PMID: 37239248 DOI: 10.3390/brainsci13050776] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Revised: 04/30/2023] [Accepted: 05/05/2023] [Indexed: 05/28/2023] Open
Abstract
The rostral ventromedial medulla (RVM) is a brainstem structure critical for the descending pain modulation system involved in both pain facilitation and inhibition through its projection to the spinal cord. Since the RVM is well connected with pain- and stress-engaged brain structures, such as the anterior cingulate cortex, nucleus accumbens, and amygdala, its involvement in stress responses has become a matter of great interest. While chronic stress has been proposed as a trigger of pain chronification and related psychiatric comorbidities due to maladaptive stress responses, acute stress triggers analgesia and other adaptative responses. Here we reviewed and highlighted the critical role of the RVM in stress responses, mainly in acute stress-induced analgesia (SIA) and chronic stress-induced hyperalgesia (SIH), providing insights into pain chronification processes and comorbidity between chronic pain and psychiatric disorders.
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Affiliation(s)
- Marco Pagliusi
- Department of Pharmacology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto 14015-069, SP, Brazil
| | - Felipe V Gomes
- Department of Pharmacology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto 14015-069, SP, Brazil
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Peng B, Jiao Y, Zhang Y, Li S, Chen S, Xu S, Gao P, Fan Y, Yu W. Bulbospinal nociceptive ON and OFF cells related neural circuits and transmitters. Front Pharmacol 2023; 14:1159753. [PMID: 37153792 PMCID: PMC10157642 DOI: 10.3389/fphar.2023.1159753] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Accepted: 04/10/2023] [Indexed: 05/10/2023] Open
Abstract
The rostral ventromedial medulla (RVM) is a bulbospinal nuclei in the descending pain modulation system, and directly affects spinal nociceptive transmission through pronociceptive ON cells and antinociceptive OFF cells in this area. The functional status of ON and OFF neurons play a pivotal role in pain chronification. As distinct pain modulative information converges in the RVM and affects ON and OFF cell excitability, neural circuits and transmitters correlated to RVM need to be defined for an in-depth understanding of central-mediated pain sensitivity. In this review, neural circuits including the role of the periaqueductal gray, locus coeruleus, parabrachial complex, hypothalamus, amygdala input to the RVM, and RVM output to the spinal dorsal horn are discussed. Meanwhile, the role of neurotransmitters is concluded, including serotonin, opioids, amino acids, cannabinoids, TRPV1, substance P and cholecystokinin, and their dynamic impact on both ON and OFF cell activities in modulating pain transmission. Via clarifying potential specific receptors of ON and OFF cells, more targeted therapies can be raised to generate pain relief for patients who suffer from chronic pain.
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Affiliation(s)
- Bingxue Peng
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Key Laboratory of Anesthesiology (Shanghai Jiao Tong University), Ministry of Education, Shanghai, China
| | - Yingfu Jiao
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Key Laboratory of Anesthesiology (Shanghai Jiao Tong University), Ministry of Education, Shanghai, China
| | - Yunchun Zhang
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Key Laboratory of Anesthesiology (Shanghai Jiao Tong University), Ministry of Education, Shanghai, China
| | - Shian Li
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Key Laboratory of Anesthesiology (Shanghai Jiao Tong University), Ministry of Education, Shanghai, China
| | - Sihan Chen
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Key Laboratory of Anesthesiology (Shanghai Jiao Tong University), Ministry of Education, Shanghai, China
| | - Saihong Xu
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Key Laboratory of Anesthesiology (Shanghai Jiao Tong University), Ministry of Education, Shanghai, China
| | - Po Gao
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Key Laboratory of Anesthesiology (Shanghai Jiao Tong University), Ministry of Education, Shanghai, China
| | - Yinghui Fan
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Key Laboratory of Anesthesiology (Shanghai Jiao Tong University), Ministry of Education, Shanghai, China
- *Correspondence: Yinghui Fan, ; Weifeng Yu,
| | - Weifeng Yu
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Key Laboratory of Anesthesiology (Shanghai Jiao Tong University), Ministry of Education, Shanghai, China
- *Correspondence: Yinghui Fan, ; Weifeng Yu,
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Xiang T, Li JH, Su HY, Bai KH, Wang S, Traub RJ, Cao DY. Spinal CCK1 Receptors Contribute to Somatic Pain Hypersensitivity Induced by Malocclusion via a Reciprocal Neuron-Glial Signaling Cascade. THE JOURNAL OF PAIN 2022; 23:1629-1645. [PMID: 35691467 PMCID: PMC9560966 DOI: 10.1016/j.jpain.2022.05.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 05/05/2022] [Accepted: 05/25/2022] [Indexed: 06/15/2023]
Abstract
Recent studies have shown that the incidence of chronic primary pain including temporomandibular disorders (TMD) and fibromyalgia syndrome (FMS) often exhibit comorbidities. We recently reported that central sensitization and descending facilitation system contributed to the development of somatic pain hypersensitivity induced by orofacial inflammation combined with stress. The purpose of this study was to explore whether TMD caused by unilateral anterior crossbite (UAC) can induce somatic pain hypersensitivity, and whether the cholecystokinin (CCK) receptor-mediated descending facilitation system promotes hypersensitivity through neuron-glia cell signaling cascade. UAC evoked thermal and mechanical pain hypersensitivity of the hind paws from day 5 to 70 that peaked at week 4 post UAC. The expression levels of CCK1 receptors, interleukin-18 (IL-18) and IL-18 receptors (IL-18R) were significantly up-regulated in the L4 to L5 spinal dorsal horn at 4 weeks post UAC. Intrathecal injection of CCK1 and IL-18 receptor antagonists blocked somatic pain hypersensitivity. IL-18 mainly co-localized with microglia, while IL-18R mainly co-localized with astrocytes and to a lesser extent with neurons. These findings indicate that the signaling transduction between neurons and glia at the spinal cord level contributes to the descending pain facilitation through CCK1 receptors during the development of the comorbidity of TMD and FMS. PERSPECTIVE: CCK1 receptor-dependent descending facilitation may mediate central mechanisms underlying the development of widespread somatic pain via a reciprocal neuron-glial signaling cascade, providing novel therapeutic targets for the clinical treatment of TMD and FMS comorbidities.
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Affiliation(s)
- Ting Xiang
- Key Laboratory of Shaanxi Province for Craniofacial Precision Medicine Research, Research Center of Stomatology, Xi'an Jiaotong University College of Stomatology, Xi'an, Shaanxi, China; Department of Orthodontics, Xi'an Jiaotong University College of Stomatology, Xi'an, Shaanxi, China
| | - Jia-Heng Li
- Key Laboratory of Shaanxi Province for Craniofacial Precision Medicine Research, Research Center of Stomatology, Xi'an Jiaotong University College of Stomatology, Xi'an, Shaanxi, China
| | - Han-Yu Su
- Key Laboratory of Shaanxi Province for Craniofacial Precision Medicine Research, Research Center of Stomatology, Xi'an Jiaotong University College of Stomatology, Xi'an, Shaanxi, China
| | - Kun-Hong Bai
- Key Laboratory of Shaanxi Province for Craniofacial Precision Medicine Research, Research Center of Stomatology, Xi'an Jiaotong University College of Stomatology, Xi'an, Shaanxi, China
| | - Shuang Wang
- Department of Orthodontics, Xi'an Jiaotong University College of Stomatology, Xi'an, Shaanxi, China
| | - Richard J Traub
- Department of Neural and Pain Sciences, School of Dentistry; Center to Advance Chronic Pain Research, University of Maryland Baltimore, Baltimore, Maryland.
| | - Dong-Yuan Cao
- Key Laboratory of Shaanxi Province for Craniofacial Precision Medicine Research, Research Center of Stomatology, Xi'an Jiaotong University College of Stomatology, Xi'an, Shaanxi, China.
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TRPV1: A Common Denominator Mediating Antinociceptive and Antiemetic Effects of Cannabinoids. Int J Mol Sci 2022; 23:ijms231710016. [PMID: 36077412 PMCID: PMC9456209 DOI: 10.3390/ijms231710016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 08/26/2022] [Accepted: 08/29/2022] [Indexed: 12/19/2022] Open
Abstract
The most common medicinal claims for cannabis are relief from chronic pain, stimulation of appetite, and as an antiemetic. However, the mechanisms by which cannabis reduces pain and prevents nausea and vomiting are not fully understood. Among more than 450 constituents in cannabis, the most abundant cannabinoids are Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD). Cannabinoids either directly or indirectly modulate ion channel function. Transient receptor potential vanilloid 1 (TRPV1) is an ion channel responsible for mediating several modalities of pain, and it is expressed in both the peripheral and the central pain pathways. Activation of TRPV1 in sensory neurons mediates nociception in the ascending pain pathway, while activation of TRPV1 in the central descending pain pathway, which involves the rostral ventral medulla (RVM) and the periaqueductal gray (PAG), mediates antinociception. TRPV1 channels are thought to be implicated in neuropathic/spontaneous pain perception in the setting of impaired descending antinociceptive control. Activation of TRPV1 also can cause the release of calcitonin gene-related peptide (CGRP) and other neuropeptides/neurotransmitters from the peripheral and central nerve terminals, including the vagal nerve terminal innervating the gut that forms central synapses at the nucleus tractus solitarius (NTS). One of the adverse effects of chronic cannabis use is the paradoxical cannabis-induced hyperemesis syndrome (HES), which is becoming more common, perhaps due to the wider availability of cannabis-containing products and the chronic use of products containing higher levels of cannabinoids. Although, the mechanism of HES is unknown, the effective treatment options include hot-water hydrotherapy and the topical application of capsaicin, both activate TRPV1 channels and may involve the vagal-NTS and area postrema (AP) nausea and vomiting pathway. In this review, we will delineate the activation of TRPV1 by cannabinoids and their role in the antinociceptive/nociceptive and antiemetic/emetic effects involving the peripheral, spinal, and supraspinal structures.
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CCK2 receptors in chronic pain. NEUROBIOLOGY OF PAIN 2022; 11:100092. [PMID: 35571964 PMCID: PMC9097710 DOI: 10.1016/j.ynpai.2022.100092] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Revised: 04/22/2022] [Accepted: 05/02/2022] [Indexed: 11/21/2022]
Abstract
CCK2R is a historic target for pain management that has shown limited success. We review CCK2Rs and their role in peripheral and central circuits in chronic pain. We discuss the interactions between CCK2Rs and opioids. We highlight recent drug discovery efforts targeting CCK2R for chronic pain.
The cholecystokinin receptor system, specifically cholecystokinin 2 receptor (CCK2R) is a historic target for pain management that has shown limited success. However, new approaches to target CCK2R have incited fresh enthusiasm for this target. In this mini-review, we discuss what is known about CCK2R in peripheral and central circuits under naïve physiological conditions and under conditions of chronic pain, the interactions of CCK2Rs with opioids and briefly, recent efforts to develop new treatments targeting CCK2R for chronic pain.
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Duan LL, Qiu XY, Wei SQ, Su HY, Bai FR, Traub RJ, Zhou Q, Cao DY. Spinal CCK contributes to somatic hyperalgesia induced by orofacial inflammation combined with stress in adult female rats. Eur J Pharmacol 2021; 913:174619. [PMID: 34748768 DOI: 10.1016/j.ejphar.2021.174619] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Revised: 11/01/2021] [Accepted: 11/03/2021] [Indexed: 11/28/2022]
Abstract
In some chronic primary pain conditions such as temporomandibular disorder (TMD) and fibromyalgia syndrome (FMS), mild or chronic stress enhances pain. TMD and FMS often occur together, but the underlying mechanisms are unclear. The purpose of this study was to investigate the role of cholecystokinin (CCK) in the spinal cord in somatic hyperalgesia induced by orofacial inflammation combined with stress. Somatic hyperalgesia was detected by the thermal withdrawal latency and mechanical withdrawal threshold. The expression of CCK1 receptors, CCK2 receptors, ERK1/2 and p-ERK1/2 in the spinal cord was examined by Western blot. After the stimulation of orofacial inflammation combined with 3 day forced swim, the expression of CCK2 receptors and p-ERK1/2 protein in the L4-L5 spinal dorsal horn increased significantly, while the expression of CCK1 receptors and ERK1/2 protein remained unchanged. Intrathecal injection of the CCK2 receptor antagonist YM-022 or mitogen-activated protein kinase (MAPK) kinase (MEK) inhibitor PD98059 blocked somatic hyperalgesia induced by orofacial inflammation combined with stress. Intrathecal administration of the MEK inhibitor blocked somatic sensitization caused by the CCK receptor agonist CCK8. The CCK2 receptor antagonist YM-022 significantly reduced the expression of p-ERK1/2. These data indicate that upregulation of CCK2 receptors through the MAPK pathway contributes to somatic hyperalgesia in this comorbid pain model. Thus, CCK2 receptors and MAPK pathway may be potential targets for the treatment of TMD comorbid with FMS.
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Affiliation(s)
- Lu-Lu Duan
- Key Laboratory of Shaanxi Province for Craniofacial Precision Medicine Research, Xi'an Jiaotong University College of Stomatology, 98 West 5th Road, Xi'an, Shaanxi, 710004, China; Department of Implant Dentistry, Xi'an Jiaotong University College of Stomatology, 98 West 5th Road, Xi'an, Shaanxi, 710004, China
| | - Xin-Yi Qiu
- Key Laboratory of Shaanxi Province for Craniofacial Precision Medicine Research, Xi'an Jiaotong University College of Stomatology, 98 West 5th Road, Xi'an, Shaanxi, 710004, China
| | - Si-Qi Wei
- Key Laboratory of Shaanxi Province for Craniofacial Precision Medicine Research, Xi'an Jiaotong University College of Stomatology, 98 West 5th Road, Xi'an, Shaanxi, 710004, China
| | - Han-Yu Su
- Key Laboratory of Shaanxi Province for Craniofacial Precision Medicine Research, Xi'an Jiaotong University College of Stomatology, 98 West 5th Road, Xi'an, Shaanxi, 710004, China
| | - Fu-Rong Bai
- Key Laboratory of Shaanxi Province for Craniofacial Precision Medicine Research, Xi'an Jiaotong University College of Stomatology, 98 West 5th Road, Xi'an, Shaanxi, 710004, China
| | - Richard J Traub
- Department of Neural and Pain Sciences, UM Center to Advance Chronic Pain Research, University of Maryland School of Dentistry, Baltimore MD, 21201, USA
| | - Qin Zhou
- Department of Implant Dentistry, Xi'an Jiaotong University College of Stomatology, 98 West 5th Road, Xi'an, Shaanxi, 710004, China.
| | - Dong-Yuan Cao
- Department of Implant Dentistry, Xi'an Jiaotong University College of Stomatology, 98 West 5th Road, Xi'an, Shaanxi, 710004, China.
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Khan F, Mehan A. Addressing opioid tolerance and opioid-induced hypersensitivity: Recent developments and future therapeutic strategies. Pharmacol Res Perspect 2021; 9:e00789. [PMID: 34096178 PMCID: PMC8181203 DOI: 10.1002/prp2.789] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Accepted: 04/07/2021] [Indexed: 01/07/2023] Open
Abstract
Opioids are a commonly prescribed and efficacious medication for the treatment of chronic pain but major side effects such as addiction, respiratory depression, analgesic tolerance, and paradoxical pain hypersensitivity make them inadequate and unsafe for patients requiring long-term pain management. This review summarizes recent advances in our understanding of the outcomes of chronic opioid administration to lay the foundation for the development of novel pharmacological strategies that attenuate opioid tolerance and hypersensitivity; the two main physiological mechanisms underlying the inadequacies of current therapeutic strategies. We also explore mechanistic similarities between the development of neuropathic pain states, opioid tolerance, and hypersensitivity which may explain opioids' lack of efficacy in certain patients. The findings challenge the current direction of analgesic research in developing non-opioid alternatives and we suggest that improving opioids, rather than replacing them, will be a fruitful avenue for future research.
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Affiliation(s)
- Faris Khan
- School of Clinical MedicineUniversity of CambridgeCambridgeUK
| | - Aman Mehan
- School of Clinical MedicineUniversity of CambridgeCambridgeUK
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WeiWei Y, WenDi F, Mengru C, Tuo Y, Chen G. The cellular mechanism by which the rostral ventromedial medulla acts on the spinal cord during chronic pain. Rev Neurosci 2021; 32:545-558. [PMID: 33565739 DOI: 10.1515/revneuro-2020-0121] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2020] [Accepted: 12/18/2020] [Indexed: 11/15/2022]
Abstract
Clinical therapies for chronic pain are limited. While targeted drugs are promising therapies for chronic pain, they exhibit insufficient efficacy and poor targeting. The occurrence of chronic pain partly results from central changes caused by alterations in neurons in the rostral ventromedial medulla (RVM) in the brainstem regulatory pathway. The RVM, which plays a key role in the descending pain control pathway, greatly contributes to the development and maintenance of pain. However, the exact roles of the RVM in chronic pain remain unclear, making it difficult to develop new drugs targeting the RVM and related pathways. Here, we first discuss the roles of the RVM and related circuits in chronic pain. Then, we analyze synaptic transmission between RVM neurons and spinal cord neurons, specifically focusing on the release of neurotransmitters, to explore the cellular mechanisms by which the RVM regulates chronic pain. Finally, we propose some ideas for the development of drugs targeting the RVM.
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Affiliation(s)
- Yu WeiWei
- Key Laboratory of Neuroregeneration of Jiangsu and the Ministry of Education, Co-innovation Center of Neuroregeneration, Nantong University, Nantong226001, China
| | - Fei WenDi
- Key Laboratory of Neuroregeneration of Jiangsu and the Ministry of Education, Co-innovation Center of Neuroregeneration, Nantong University, Nantong226001, China
| | - Cui Mengru
- Department of Anesthesiology, Affiliated Hospital of Nantong University, Nantong226001, China
| | - Yang Tuo
- Department of Hand Surgery, China-Japan Union Hospital of Jilin University, Changchun130033, China
| | - Gang Chen
- Department of Anesthesiology, Affiliated Hospital of Nantong University, Nantong226001, China.,Department of Tissue and Embryology, Medical School of Nantong University, Co-innovation Center of Neuroregeneration, Nantong University, Nantong226001, China
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Ahmadi-Soleimani SM, Mianbandi V, Azizi H, Azhdari-Zarmehri H, Ghaemi-Jandabi M, Abbasi-Mazar A, Mohajer Y, Darana SP. Coregulation of sleep-pain physiological interplay by orexin system: An unprecedented review. Behav Brain Res 2020; 391:112650. [DOI: 10.1016/j.bbr.2020.112650] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Revised: 02/28/2020] [Accepted: 04/08/2020] [Indexed: 12/14/2022]
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13
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Bagley EE, Ingram SL. Endogenous opioid peptides in the descending pain modulatory circuit. Neuropharmacology 2020; 173:108131. [PMID: 32422213 DOI: 10.1016/j.neuropharm.2020.108131] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 05/01/2020] [Accepted: 05/04/2020] [Indexed: 02/07/2023]
Abstract
The opioid epidemic has led to a serious examination of the use of opioids for the treatment of pain. Opioid drugs are effective due to the expression of opioid receptors throughout the body. These receptors respond to endogenous opioid peptides that are expressed as polypeptide hormones that are processed by proteolytic cleavage. Endogenous opioids are expressed throughout the peripheral and central nervous system and regulate many different neuronal circuits and functions. One of the key functions of endogenous opioid peptides is to modulate our responses to pain. This review will focus on the descending pain modulatory circuit which consists of the ventrolateral periaqueductal gray (PAG) projections to the rostral ventromedial medulla (RVM). RVM projections modulate incoming nociceptive afferents at the level of the spinal cord. Stimulation within either the PAG or RVM results in analgesia and this circuit has been studied in detail in terms of the actions of exogenous opioids, such as morphine and fentanyl. Further emphasis on understanding the complex regulation of endogenous opioids will help to make rational decisions with regard to the use of opioids for pain. We also include a discussion of the actions of endogenous opioids in the amygdala, an upstream brain structure that has reciprocal connections to the PAG that contribute to the brain's response to pain.
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Affiliation(s)
- Elena E Bagley
- Discipline of Pharmacology and Charles Perkins Centre, University of Sydney, NSW, 2006, Australia
| | - Susan L Ingram
- Department of Neurological Surgery, Oregon Health & Science University, Portland, OR, 97239, USA.
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Bouchet CA, Ingram SL. Cannabinoids in the descending pain modulatory circuit: Role in inflammation. Pharmacol Ther 2020; 209:107495. [PMID: 32004514 PMCID: PMC7183429 DOI: 10.1016/j.pharmthera.2020.107495] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Accepted: 01/17/2020] [Indexed: 01/09/2023]
Abstract
The legalization of cannabis in some states has intensified interest in the potential for cannabis and its constituents to lead to novel therapeutics for pain. Our understanding of the cellular mechanisms underlying cannabinoid actions in the brain have lagged behind opioids; however, the current opioid epidemic has also increased attention on the use of cannabinoids as alternatives to opioids for pain, especially chronic pain that requires long-term use. Endogenous cannabinoids are lipid signaling molecules that have complex roles in modulating neuronal function throughout the brain. In this review, we discuss cannabinoid functions in the descending pain modulatory pathway, a brain circuit that integrates cognitive and emotional processing of pain to modulate incoming sensory inputs. In addition, we highlight areas where further studies are necessary to understand cannabinoid regulation of descending pain modulation.
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Affiliation(s)
- Courtney A Bouchet
- Department of Neurological Surgery, Oregon Health & Science University, Portland, OR 97239, United States of America
| | - Susan L Ingram
- Department of Neurological Surgery, Oregon Health & Science University, Portland, OR 97239, United States of America.
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Benedetti F, Frisaldi E, Barbiani D, Camerone E, Shaibani A. Nocebo and the contribution of psychosocial factors to the generation of pain. J Neural Transm (Vienna) 2019; 127:687-696. [DOI: 10.1007/s00702-019-02104-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Accepted: 11/12/2019] [Indexed: 12/17/2022]
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Jiang M, Bo J, Lei Y, Hu F, Xia Z, Liu Y, Lu C, Sun Y, Hou B, Ni K, Ma Z, Gu X. Anxiety-induced hyperalgesia in female rats is mediated by cholecystokinin 2 receptor in rostral ventromedial medulla and spinal 5-hydroxytryptamine 2B receptor. J Pain Res 2019; 12:2009-2026. [PMID: 31308730 PMCID: PMC6613357 DOI: 10.2147/jpr.s187715] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2018] [Accepted: 05/29/2019] [Indexed: 12/18/2022] Open
Abstract
Background Preoperative anxiety is associated with postoperative hyperalgesia; however, few studies have investigated the mechanism underlying this association in female surgical patients. Research has suggested that ON cells in the rostral ventromedial medulla (RVM) receive nerve impulses via cholecystokinin 2 (CCK2) receptors, facilitating hyperalgesia. Additionally, the downstream serotonergic projection system from the RVM to the spinal cord has a dual regulating effect on pain responses, and the 5-hydoxytryptophan 2B (5-HT2B) receptor in spinal dorsal horn neurons is critically involved in mechanical allodynia. Methods Ovariectomized rats were treated with estrogen replacement, single prolonged stress (SPS), and plantar incision. Various receptor agonists and antagonists were then administered into the RVM and spinal cord to study the mechanism underlying postoperative hyperalgesia caused by preoperative anxiety in female rats. Results Behavioral testing revealed that preoperative SPS induced postoperative hyperalgesia, as well as the expression of the CCK2 receptor in the RVM and the expression of the 5-HT2B receptor, protein kinase Cγ (PKCγ), and phosphorylation of the N-methyl-d-aspartate receptor1 (p-NR1) in the spinal cord increased confirmed by Western blot. RVM microinjection of the CCK2 receptor agonist CCK-8 and intrathecal injection of the 5-HT2B receptor agonist BW723C86 both produced hyperalgesia in female rats after plantar incision, whereas the CCK2 receptor antagonist YM022, the 5-HT2B receptor antagonist RS127445, and the PKCγ inhibitor C37H65N9O13 decreased the rats’ sensitivity to the same stimulus. Additionally, electrophysiological analysis suggested that activation of the 5-HT2B receptor increased the whole-cell current (IBa) in superficial dorsal horn neurons through the PKCγ pathway. Conclusion Our study demonstrated that preoperative anxiety-induced postoperative hyperalgesia in female rats is associated with descending pain pathways. The CCK2 receptor in the RVM and spinal 5-HT2B receptor may play a role in this hyperalgesic effect.
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Affiliation(s)
- Ming Jiang
- Department of Anesthesiology, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing 210008, Jiangsu Province, People's Republic of China
| | - Jinhua Bo
- Department of Anesthesiology, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing 210008, Jiangsu Province, People's Republic of China
| | - Yishan Lei
- Department of Anesthesiology, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing 210008, Jiangsu Province, People's Republic of China
| | - Fan Hu
- Department of Basic Medicine, Analytical & Testing Center, Nanjing Medical University, Nanjing, Jiangsu Province, People's Republic of China
| | - Zhengrong Xia
- Department of Basic Medicine, Analytical & Testing Center, Nanjing Medical University, Nanjing, Jiangsu Province, People's Republic of China
| | - Yue Liu
- Department of Anesthesiology, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing 210008, Jiangsu Province, People's Republic of China
| | - Cui'e Lu
- Department of Anesthesiology, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing 210008, Jiangsu Province, People's Republic of China
| | - Yu'e Sun
- Department of Anesthesiology, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing 210008, Jiangsu Province, People's Republic of China
| | - Bailing Hou
- Department of Anesthesiology, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing 210008, Jiangsu Province, People's Republic of China
| | - Kun Ni
- Department of Anesthesiology, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing 210008, Jiangsu Province, People's Republic of China
| | - Zhengliang Ma
- Department of Anesthesiology, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing 210008, Jiangsu Province, People's Republic of China
| | - Xiaoping Gu
- Department of Anesthesiology, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing 210008, Jiangsu Province, People's Republic of China
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Alterations in the rostral ventromedial medulla after the selective ablation of μ-opioid receptor expressing neurons. Pain 2016; 157:166-173. [PMID: 26335909 DOI: 10.1097/j.pain.0000000000000344] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The rostral ventromedial medulla (RVM) exerts both inhibitory and excitatory controls over nociceptive neurons in the spinal cord and medullary dorsal horn. Selective ablation of mu-opioid receptor (MOR)-expressing neurons in the RVM using saporin conjugated to the MOR agonist dermorphin-saporin (derm-sap) attenuates stress and injury-induced behavioral hypersensitivity, yet the effect of RVM derm-sap on the functional integrity of the descending inhibitory system and the properties of RVM neurons remain unknown. Three classes of RVM neurons (on-cells, off-cells, and neutral cells) have been described with distinct responses to noxious stimuli and MOR agonists. Using single unit recording in lightly anesthetized rats, RVM neurons were characterized after microinjections of derm-sap or saporin. Derm-sap treatment resulted in a reduction in on-cells and off-cells when compared to saporin controls (P < 0.05). The number of neutral cells remained unchanged. After derm-sap treatment, RVM microinjections of the glutamate receptor agonist homocysteic acid increased tail-flick latencies, whereas the MOR agonist DAMGO had no effect. Furthermore, electrical stimulation of the periaqueductal gray produced analgesia in both derm-sap and saporin controls with similar thresholds. Microinjection of kynurenic acid, a glutamate receptor antagonist, into the RVM disrupted periaqueductal gray stimulation-produced analgesia in both saporin-treated and derm-sap-treated rats. These results indicate that MOR-expressing neurons in the RVM are not required for analgesia produced by either direct or indirect activation of neurons in the RVM.
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Hitomi S, Kross K, Kurose M, Porreca F, Meng ID. Activation of dura-sensitive trigeminal neurons and increased c-Fos protein induced by morphine withdrawal in the rostral ventromedial medulla. Cephalalgia 2016; 37:407-417. [DOI: 10.1177/0333102416648655] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Aims Overuse of medications used to treat migraine headache can increase the frequency of headaches. Sudden abstinence from migraine medication can also lead to a period of withdrawal-induced headaches. The aim of this study was to examine the effect of morphine withdrawal localized to the rostral ventromedial medulla (RVM) on the activity of dura-sensitive spinal trigeminal nucleus caudalis (Vc) neurons. Methods Rats were implanted with either morphine or placebo pellets for six to seven days before the microinjection of naloxone methiodide or phosphate-buffered saline into the RVM in urethane-anesthetized animals. Dura-sensitive neurons were recorded in the Vc and the production of c-Fos-like immunoreactivity was quantified. Results In chronic morphine-treated animals, naloxone methiodide microinjections produced a significant increase both in ongoing and facial heat-evoked activity and an increase in Fos-positive neurons in the Vc and in the nucleus reticularis dorsalis, a brainstem region involved in diffuse noxious inhibitory controls. Conclusions These results indicate that activation of pronociceptive neurons in the RVM under conditions of morphine withdrawal can increase the activity of neurons that transmit headache pain. Modulation of the subnucleus reticularis dorsalis by the RVM may explain the attenuation of conditioned pain modulation in patients with chronic headache.
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Affiliation(s)
- Suzuro Hitomi
- Division of Physiology, Kyushu Dental University, Japan
| | - Konrad Kross
- Center for Excellence in the Neurosciences, University of New England, USA
| | - Masayuki Kurose
- Division of Oral Physiology, Department of Oral Biological Sciences, Niigata University, Graduate School of Medical and Dental Sciences, Japan
| | - Frank Porreca
- Department of Pharmacology, College of Medicine, University of Arizona, Health Sciences Center, USA
| | - Ian D Meng
- Center for Excellence in the Neurosciences, University of New England, USA
- Department of Biomedical Sciences, College of Osteopathic Medicine, University of New England, USA
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Abstract
Pain is more than merely nociception and response, but rather it encompasses emotional, behavioral and cognitive components that make up the pain experience. With the recent advances in imaging techniques, we now understand that nociceptive inputs can result in the activation of complex interactions among central sites, including cortical regions that are active in cognitive, emotional and reward functions. These sites can have a bimodal influence on the serotonergic and noradrenergic descending pain modulatory systems via communications among the periaqueductal gray, rostral ventromedial medulla and pontine noradrenergic nuclei, ultimately either facilitating or inhibiting further nociceptive inputs. Understanding these systems can help explain the emotional and cognitive influences on pain perception and placebo/nocebo effects, and can help guide development of better pain therapeutics.
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Affiliation(s)
- Milena De Felice
- The University of Sheffield, Academic Unit of Oral & Maxillofacial Medicine & Surgery, Sheffield, South Yorkshire, UK
| | - Michael H Ossipov
- Department of Pharmacology, University of Arizona College of Medicine, Tucson, AZ 85724-5050, USA
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Boadas-Vaello P, Castany S, Homs J, Álvarez-Pérez B, Deulofeu M, Verdú E. Neuroplasticity of ascending and descending pathways after somatosensory system injury: reviewing knowledge to identify neuropathic pain therapeutic targets. Spinal Cord 2016; 54:330-40. [DOI: 10.1038/sc.2015.225] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 11/25/2015] [Accepted: 11/28/2015] [Indexed: 12/16/2022]
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Heinricher MM. Pain Modulation and the Transition from Acute to Chronic Pain. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 904:105-15. [PMID: 26900066 DOI: 10.1007/978-94-017-7537-3_8] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
There is now increasing evidence that pathological pain states are at least in part driven by changes in the brain itself. Descending modulatory pathways are known to mediate top-down regulation of nociceptive processing, transmitting cortical and limbic influences to the dorsal horn. However, these modulatory pathways are also intimately intertwined with ascending transmission pathways through positive and negative feedback loops. Models of persistent pain that fail to include descending modulatory pathways are thus incomplete. Although teasing out individual links in a recurrent network is never straightforward, it is imperative that understanding of pain modulation be fully integrated into how we think about pain.
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Affiliation(s)
- Mary M Heinricher
- Dept. Neurological Surgery, Oregon Health & Science University, Portland, OR, 97239, USA.
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Selective melatonin MT2 receptor ligands relieve neuropathic pain through modulation of brainstem descending antinociceptive pathways. Pain 2015; 156:305-317. [PMID: 25599452 DOI: 10.1097/01.j.pain.0000460311.71572.5f] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Neuropathic pain is an important public health problem for which only a few treatments are available. Preclinical studies show that melatonin (MLT), a neurohormone acting on MT1 and MT2 receptors, has analgesic properties, likely through MT2 receptors. Here, we determined the effects of the novel selective MLT MT2 receptor partial agonist N-{2-([3-bromophenyl]-4-fluorophenylamino)ethyl}acetamide (UCM924) in 2 neuropathic pain models in rats and examined its supraspinal mechanism of action. In rat L5-L6 spinal nerve ligation and spared nerve injury models, UCM924 (20-40 mg/kg, subcutaneously) produced a prolonged antinociceptive effect that is : (1) dose-dependent and blocked by the selective MT2 receptor antagonist 4-phenyl-2-propionamidotetralin, (2) superior to a high dose of MLT (150 mg/kg) and comparable with gabapentin (100 mg/kg), but (3) without noticeable motor coordination impairments in the rotarod test. Using double staining immunohistochemistry, we found that MT2 receptors are expressed by glutamatergic neurons in the rostral ventrolateral periaqueductal gray. Using in vivo electrophysiology combined with tail flick, we observed that microinjection of UCM924 into the ventrolateral periaqueductal gray decreased tail flick responses, depressed the firing activity of ON cells, and activated the firing of OFF cells; all effects were MT2 receptor-dependent. Altogether, these data demonstrate that selective MT2 receptor partial agonists have analgesic properties through modulation of brainstem descending antinociceptive pathways, and MT2 receptors may represent a novel target in the treatment of neuropathic pain.
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Wang EM, Li WT, Yan XJ, Chen X, Liu Q, Feng CC, Cao ZJ, Fang JY, Chen SL. Vagal afferent-dependent cholecystokinin modulation of visceral pain requires central amygdala NMDA-NR2B receptors in rats. Neurogastroenterol Motil 2015. [PMID: 26197883 DOI: 10.1111/nmo.12633] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
BACKGROUND Cholecystokinin (CCK), a gut hormone that is released during feeding, exerts gastrointestinal effects in part through vagal pathway. It is reported to be a potential trigger for increased postprandial visceral sensitivity in healthy subjects and, especially in patients with irritable bowel syndrome. NR2B-containing N-methyl-d-aspartate (NMDA) receptors in the central amygdala (CeA) participate in pain modulation. Systemically administered CCK activates the CeA-innervating neurons. Here, we investigated whether CCK modulation of visceral sensitivity is mediated through CeA NMDA-NR2B receptors and whether this modulation involves vagal pathway. METHODS We first examined the visceromotor response (VMR) to colorectal distention (CRD) following i.p. injection of CCK octapeptide (CCK-8) in a rat model. Next, the NR2B antagonist ifenprodil and the NR2A antagonist NVP-AAM077 were microinjected into the CeA before systemic CCK injection. NR2B phosphorylation was detected by Western blot. To down-regulate NR2B gene expression, NR2B-specific small interfering RNA (siRNA) was delivered into CeA neurons by electroporation. In addition, the effects of functional deafferentation by perivagal application of capsaicin and pretreatment with the CCK1 receptor antagonist devazepide were investigated. KEY RESULTS CCK-8 increased VMR to CRD in a dose-dependent manner. This effect was blunted by intra-CeA administration of ifenprodil (but not NVP-AAM077) and was accompanied by phosphorylation of NR2B subunits in the CeA. CCK failed to increase VMR to CRD in NR2B siRNA-treated rats. Perivagal capsaicin application and pretreatment with devazepide prevented CCK-induced pronociception and CeA NR2B phosphorylation. CONCLUSIONS & INFERENCES The pronociception induced by systemic CCK, which is vagal afferent-dependent, requires activation of CeA NMDA-NR2B receptors.
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Affiliation(s)
- E M Wang
- Division of Gastroenterology and Hepatology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai, China
| | - W T Li
- Division of Gastroenterology and Hepatology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai, China
| | - X J Yan
- Division of Gastroenterology and Hepatology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai, China
| | - X Chen
- Division of Gastroenterology and Hepatology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai, China
| | - Q Liu
- Division of Gastroenterology and Hepatology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai, China
| | - C C Feng
- Division of Gastroenterology and Hepatology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai, China
| | - Z J Cao
- Division of Gastroenterology and Hepatology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai, China
| | - J Y Fang
- Division of Gastroenterology and Hepatology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai, China
| | - S L Chen
- Division of Gastroenterology and Hepatology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai, China
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Spinal and supraspinal N-methyl-d-aspartate and melanocortin-1 receptors contribute to a qualitative sex difference in morphine-induced hyperalgesia. Physiol Behav 2015; 147:364-72. [DOI: 10.1016/j.physbeh.2015.05.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Revised: 05/01/2015] [Accepted: 05/04/2015] [Indexed: 12/27/2022]
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Tomim DH, Pontarolla FM, Bertolini JF, Arase M, Tobaldini G, Lima MMS, Fischer L. The Pronociceptive Effect of Paradoxical Sleep Deprivation in Rats: Evidence for a Role of Descending Pain Modulation Mechanisms. Mol Neurobiol 2015; 53:1706-1717. [DOI: 10.1007/s12035-014-9059-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 12/08/2014] [Indexed: 01/22/2023]
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Pineda-Farias JB, Velázquez-Lagunas I, Barragán-Iglesias P, Cervantes-Durán C, Granados-Soto V. 5-HT 2B Receptor Antagonists Reduce Nerve Injury-Induced Tactile Allodynia and Expression of 5-HT 2B Receptors. Drug Dev Res 2015; 76:31-39. [PMID: 25620128 DOI: 10.1002/ddr.21238] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Accepted: 12/10/2014] [Indexed: 01/01/2023]
Abstract
Preclinical Research This work was performed to assess the effects of intrathecal serotonin 2B (5-HT2B ) receptor antagonists in rats with neuropathic pain. With RS-127445, its effect was also determined on 5-HT2B receptor expression. Neuropathic pain was induced by L5/L6 spinal nerve ligation. Western blotting was used to determine 5-HT2B receptor expression. Dose-response curves with the 5-HT2B receptor antagonists 2-amino-4-(4-fluoronaphth-1-yl)-6-isopropylpyridine (RS-127445, 1-100 nmol) and 1-[(2-chloro-3,4-dimethoxyphenyl)methyl]-2,3,4,9-tetrahydro-6-methyl-1H-pyrido[3,4-b]indole hydrochloride (LY-266097, 1-100 nmol) were performed in rats. Tactile allodynia of the left hind paw (ipsilateral) was assessed for 8 h after compound administration. Intrathecal injection of the 5-HT2B receptor antagonists RS-127445 and LY-266097 diminished spinal nerve ligation-induced allodynia. In contrast, intrathecal injection of the 5-HT2 receptor agonist (±)-2,5-dimethoxy-4-iodoamphetamine hydrochloride (DOI, 10 nmol) did not modify tactile allodynia induced by nerve ligation. L5/L6 nerve ligation increased expression of the 5-HT2B receptors in the ipsilateral, but not contralateral, dorsal root ganglia. Furthermore, nerve injury also enhanced 5-HT2B receptor expression in the ipsilateral dorsal part of the spinal cord. Intrathecal treatment with RS-127445 (100 nmol) diminished spinal nerve injury-induced increased expression of 5-HT2B receptors in dorsal root ganglia and spinal cord. Our results imply that spinal 5-HT2B receptors are present on sites related to nociception and participate in neuropathic pain. © 2014 Wiley Periodicals, Inc.
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Affiliation(s)
- Jorge B Pineda-Farias
- Neurobiology of Pain Laboratory, Departamento de Farmacobiología, Centro de Investigación y de Estudios Avanzados (Cinvestav), Sede Sur. México, D.F., México
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Thomas J, Mustafa S, Johnson J, Nicotra L, Hutchinson M. The relationship between opioids and immune signalling in the spinal cord. Handb Exp Pharmacol 2015; 227:207-238. [PMID: 25846621 DOI: 10.1007/978-3-662-46450-2_11] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Opioids are considered the gold standard for the treatment of moderate to severe pain. However, heterogeneity in analgesic efficacy, poor potency and side effects are associated with opioid use, resulting in dose limitations and suboptimal pain management. Traditionally thought to exhibit their analgesic actions via the activation of the neuronal G-protein-coupled opioid receptors, it is now widely accepted that neuronal activity of opioids cannot fully explain the initiation and maintenance of opioid tolerance, hyperalgesia and allodynia. In this review we will highlight the evidence supporting the role of non-neuronal mechanisms in opioid signalling, paying particular attention to the relationship of opioids and immune signalling.
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Affiliation(s)
- Jacob Thomas
- Discipline of Pharmacology, School of Medical Sciences, University of Adelaide, Adelaide, Australia,
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Li MH, Suchland KL, Ingram SL. GABAergic transmission and enhanced modulation by opioids and endocannabinoids in adult rat rostral ventromedial medulla. J Physiol 2014; 593:217-30. [PMID: 25556797 DOI: 10.1113/jphysiol.2014.275701] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Accepted: 10/17/2014] [Indexed: 01/24/2023] Open
Abstract
KEY POINTS Electrical stimulation of the rostral ventromedial medulla (RVM) facilitates pain behaviours in neonates but inhibits these behaviours in adults. The cellular mechanisms underlying these changes in RVM modulation of pain behaviours are not known. We optimized whole-cell patch-clamp recordings for RVM neurons in animals older than postnatal day 30 and compared the results to postnatal day 10-21 animals. Our results demonstrate that the γ-aminobutyric acid (GABA) release is lower and opioid effects are more evident in adult rats compared to early postnatal rats. A cannabinoid receptor antagonist significantly increased GABA release in mature but not in immature RVM neurons suggesting the presence of local endocannabinoid tone in mature RVM. Neurons in the rostral ventromedial medulla (RVM) play critical and complex roles in pain modulation. Recent studies have shown that electrical stimulation of the RVM produces pain facilitation in young animals (postnatal (PN) day < 21) but predominantly inhibits pain behaviours in adults. The cellular mechanisms underlying these changes in RVM modulation of pain behaviours are not known. This is in part because whole-cell patch-clamp studies in RVM to date have been in young (PN day < 18) animals because the organization and abundance of myelinated fibres in this region make the RVM a challenging area for whole-cell patch-clamp recording in adults. Several neurotransmitter systems, including GABAergic neurotransmission, undergo developmental changes that mature by PN day 21. Thus, we focused on optimizing whole-cell patch-clamp recordings for RVM neurons in animals older than PN day 30 and compared the results to animals at PN day 10-21. Our results demonstrate that the probability of GABA release is lower and that opioid and endocannabinoid effects are more evident in adult rats (mature) compared to early postnatal (immature) rats. Differences in these properties of RVM neurons may contribute to the developmental changes in descending control of pain from the RVM to the spinal cord.
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Affiliation(s)
- Ming-Hua Li
- Department of Neurological Surgery, Oregon Health and Science University, Portland, OR, 97239, USA
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Stress-induced hyperalgesia. Prog Neurobiol 2014; 121:1-18. [DOI: 10.1016/j.pneurobio.2014.06.003] [Citation(s) in RCA: 159] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2014] [Revised: 05/17/2014] [Accepted: 06/29/2014] [Indexed: 12/25/2022]
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Wen D, Sun D, Zang G, Hao L, Liu X, Yu F, Ma C, Cong B. Cholecystokinin octapeptide induces endogenous opioid-dependent anxiolytic effects in morphine-withdrawal rats. Neuroscience 2014; 277:14-25. [DOI: 10.1016/j.neuroscience.2014.06.048] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Revised: 06/17/2014] [Accepted: 06/17/2014] [Indexed: 11/27/2022]
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Cleary DR, Roeder Z, Elkhatib R, Heinricher MM. Neuropeptide Y in the rostral ventromedial medulla reverses inflammatory and nerve injury hyperalgesia in rats via non-selective excitation of local neurons. Neuroscience 2014; 271:149-59. [PMID: 24792711 PMCID: PMC4071144 DOI: 10.1016/j.neuroscience.2014.04.035] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Revised: 04/18/2014] [Accepted: 04/21/2014] [Indexed: 01/03/2023]
Abstract
Chronic pain reflects not only sensitization of the ascending nociceptive pathways, but also changes in descending modulation. The rostral ventromedial medulla (RVM) is a key structure in a well-studied descending pathway, and contains two classes of modulatory neurons, the ON-cells and the OFF-cells. Disinhibition of OFF-cells depresses nociception; increased ON-cell activity facilitates nociception. Multiple lines of evidence show that sensitization of ON-cells contributes to chronic pain, and reversing or blocking this sensitization is of interest as a treatment of persistent pain. Neuropeptide Y (NPY) acting via the Y1 receptor has been shown to attenuate hypersensitivity in nerve-injured animals without affecting normal nociception when microinjected into the RVM, but the neural basis for this effect was unknown. We hypothesized that behavioral anti-hyperalgesia was due to selective inhibition of ON-cells by NPY at the Y1 receptor. To explore the possibility of Y1 selectivity on ON-cells, we stained for the NPY-Y1 receptor in the RVM, and found it broadly expressed on both serotonergic and non-serotonergic neurons. In subsequent behavioral experiments, NPY microinjected into the RVM in lightly anesthetized animals reversed signs of mechanical hyperalgesia following either nerve injury or chronic hindpaw inflammation. Unexpectedly, rather than decreasing ON-cell activity, NPY increased spontaneous activity of both ON- and OFF-cells without altering noxious-evoked changes in firing. Based on these results, we conclude that the anti-hyperalgesic effects of NPY in the RVM are not explained by selective inhibition of ON-cells, but rather by increased spontaneous activity of OFF-cells. Although ON-cells undoubtedly facilitate nociception and contribute to hypersensitivity, the present results highlight the importance of parallel OFF-cell-mediated descending inhibition in limiting the expression of chronic pain.
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Affiliation(s)
- D R Cleary
- Department of Neurological Surgery, Oregon Health & Science University, Portland, OR, United States.
| | - Z Roeder
- Department of Neurological Surgery, Oregon Health & Science University, Portland, OR, United States
| | - R Elkhatib
- Department of Neurological Surgery, Oregon Health & Science University, Portland, OR, United States; Department of Anesthesia, Cairo University Hospital, Cairo, Egypt
| | - M M Heinricher
- Department of Neurological Surgery, Oregon Health & Science University, Portland, OR, United States; Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR, United States
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Giri AK, Hruby VJ. Investigational peptide and peptidomimetic μ and δ opioid receptor agonists in the relief of pain. Expert Opin Investig Drugs 2014; 23:227-41. [PMID: 24329035 PMCID: PMC4282681 DOI: 10.1517/13543784.2014.856879] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
INTRODUCTION Current methods for treating prolonged and neuropathic pain are inadequate and lead to toxicities that greatly diminish quality of life. Therefore, new approaches to the treatment of pain states are needed to address these problems. AREAS COVERED The review primarily reviews approaches that have been taken in the peer-reviewed literature of multivalent ligands that interact with both μ and δ opioid receptors as agonists, and in some cases, also with pharmacophores for antagonist ligands that interact with other receptors as antagonists to block pain. EXPERT OPINION Although there are a number of drugs currently on the market for the treatment of pain; none of them are 100% successful. In the authors' opinion, it is clear that new directions and modalities are needed to better address the treatment of prolonged and neuropathic pain; one drug or class clearly is not the answer for all pain therapy. Undoubtedly, there are many different phenotypes of prolonged and neuropathic pain and this should be one avenue to further develop appropriate therapies.
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Affiliation(s)
- Aswini Kumar Giri
- University of Arizona, Department of Chemistry and Biochemistry , 1306 East University Boulevard, PO Box 210041, Tucson, AZ 85721 , USA
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Besson M, Piguet V, Dayer P, Desmeules J. New approaches to the pharmacotherapy of neuropathic pain. Expert Rev Clin Pharmacol 2014; 1:683-93. [PMID: 24422738 DOI: 10.1586/17512433.1.5.683] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Pain is one of the most debilitating symptoms that presents with neuropathy. Neuropathic pain syndrome is a challenge to treat and, even with appropriate evidence-based treatment, only a 40% reduction of symptoms can be achieved in approximately half of patients. Furthermore, efficient doses are often difficult to obtain because of adverse effects. These observations underline that the treatment of neuropathic pain is still an unmet medical need. New approaches to the pharmacotherapy of neuropathy embrace different lines of work, including a fundamental mechanism-based approach, a clinical mechanism-based approach and an evidence-based approach. Moreover, interindividual variability in drug response, and genetic polymorphism in particular, is an emerging aspect to consider. Together with reviewing recent evidence-based guidelines as well as briefly discussing genetic polymorphisms that may influence the individual responses to treatments, this article will focus on what a mechanism-based approach is bringing to the clinical setting, on the perspective in fundamental research and on the difficulty of bridging the gap between fundamental notions and positive clinical outcomes.
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Affiliation(s)
- Marie Besson
- Division of Clinical Pharmacology and Toxicology, Geneva University Hospital, Rue Micheli du Crest 24, 1211 Geneva 14, Switzerland.
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Thomas J, Hutchinson MR. Exploring neuroinflammation as a potential avenue to improve the clinical efficacy of opioids. Expert Rev Neurother 2014; 12:1311-24. [DOI: 10.1586/ern.12.125] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Wen D, Zang G, Sun D, Yu F, Mei D, Ma C, Cong B. Cholecystokinin-octapeptide restored morphine-induced hippocampal long-term potentiation impairment in rats. Neurosci Lett 2013; 559:76-81. [PMID: 24309294 DOI: 10.1016/j.neulet.2013.11.043] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Revised: 11/11/2013] [Accepted: 11/21/2013] [Indexed: 11/29/2022]
Abstract
Cholecystokinin-octapeptide (CCK-8), which is a typical brain-gut peptide, exerts a wide range of biological activities on the central nervous system. We have previously reported that CCK-8 significantly alleviated morphine-induced amnesia and reversed spine density decreases in the CA1 region of the hippocampus in morphine-treated animals. Here, we investigated the effects of CCK-8 on long-term potentiation (LTP) in the lateral perforant path (LPP)-granule cell synapse of rat dentate gyrus (DG) in acute saline or morphine-treated rats. Population spikes (PS), which were evoked by stimulation of the LPP, were recorded in the DG region. Acute morphine (30mg/kg, s.c.) treatment significantly attenuated hippocampal LTP and CCK-8 (1μg, i.c.v.) restored the amplitude of PS that was attenuated by morphine injection. Furthermore, microinjection of CCK-8 (0.1 and 1μg, i.c.v.) also significantly augmented hippocampal LTP in saline-treated (1ml/kg, s.c.) rats. Pre-treatment of the CCK2 receptor antagonist L-365,260 (10μg, i.c.v) reversed the effects of CCK-8, but the CCK1 receptor antagonist L-364,718 (10μg, i.c.v) did not. The present results demonstrate that CCK-8 attenuates the effect of morphine on hippocampal LTP through CCK2 receptors and suggest an ameliorative function of CCK-8 on morphine-induced memory impairment.
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Affiliation(s)
- Di Wen
- Department of Forensic Medicine, Hebei Medical University, Hebei Key Laboratory of Forensic Medicine, Shijiazhuang 050017, PR China
| | - Guoqing Zang
- Department of Forensic Medicine, Hebei Medical University, Hebei Key Laboratory of Forensic Medicine, Shijiazhuang 050017, PR China
| | - DongLei Sun
- Department of Forensic Medicine, Hebei Medical University, Hebei Key Laboratory of Forensic Medicine, Shijiazhuang 050017, PR China
| | - Feng Yu
- Department of Forensic Medicine, Hebei Medical University, Hebei Key Laboratory of Forensic Medicine, Shijiazhuang 050017, PR China
| | - Dong Mei
- Department of Forensic Medicine, Hebei Medical University, Hebei Key Laboratory of Forensic Medicine, Shijiazhuang 050017, PR China
| | - Chunling Ma
- Department of Forensic Medicine, Hebei Medical University, Hebei Key Laboratory of Forensic Medicine, Shijiazhuang 050017, PR China.
| | - Bin Cong
- Department of Forensic Medicine, Hebei Medical University, Hebei Key Laboratory of Forensic Medicine, Shijiazhuang 050017, PR China.
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Carballosa-Gonzalez MM, Vitores A, Hentall ID. Hindbrain raphe stimulation boosts cyclic adenosine monophosphate and signaling proteins in the injured spinal cord. Brain Res 2013; 1543:165-72. [PMID: 24246733 DOI: 10.1016/j.brainres.2013.11.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Revised: 11/05/2013] [Accepted: 11/09/2013] [Indexed: 12/20/2022]
Abstract
Early recovery from incomplete spinal cord contusion is improved by prolonged stimulation of the hindbrain's serotonergic nucleus raphe magnus (NRM). Here we examine whether increases in cyclic adenosine monophosphate (cAMP), an intracellular signaling molecule with several known restorative actions on damaged neural tissue, could play a role. Subsequent changes in cAMP-dependent phosphorylation of protein kinase A (PKA) and PKA-dependent phosphorylation of the transcription factor "cAMP response element-binding protein" (CREB) are also analyzed. Rats with moderate weight-drop injury at segment T8 received 2h of NRM stimulation beginning three days after injury, followed immediately by separate extraction of cervical, thoracic and lumbar spinal cord for immunochemical assay. Controls lacked injury, stimulation or both. Injury reduced cAMP levels to under half of normal in all three spinal regions. NRM stimulation completely restored these levels, while producing no significant change in non-injured rats. Pretreatment with the 5-HT7 receptor antagonist pimozide (1 mg/kg, intraperitoneal) lowered cAMP in non-injured rats to injury amounts, which were unchanged by NRM stimulation. The phosphorylated fraction of PKA (pPKA) and CREB (pCREB) was reduced significantly in all three regions after SCI and restored by NRM stimulation, except for pCREB in lumbar segments. In conclusion, SCI produces spreading deficits in cAMP, pPKA and pCREB that are reversible by Gs protein-coupled 5-HT receptors responding to raphe-spinal activity, although these signaling molecules are not reactive to NRM stimulation in normal tissue. These findings can partly explain the benefits of NRM stimulation after SCI.
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Affiliation(s)
| | - Alberto Vitores
- Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Ian D Hentall
- Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, USA.
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van den Broeke EN, Geene N, van Rijn CM, Wilder-Smith OHG, Oosterman J. Negative expectations facilitate mechanical hyperalgesia after high-frequency electrical stimulation of human skin. Eur J Pain 2013; 18:86-91. [PMID: 23754275 DOI: 10.1002/j.1532-2149.2013.00342.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/09/2013] [Indexed: 11/10/2022]
Abstract
BACKGROUND High-frequency electrical stimulation (HFS) of human skin induces not only an increased pain sensitivity in the conditioning area but also an increased pain sensitivity to mechanical punctate stimuli in the non-conditioned surrounding skin area. The aim of the present study was to investigate whether this heterotopically increased mechanical pain sensitivity can be facilitated through the induction of negative expectations. METHODS In two independent conditions [a nocebo (n = 15) and control condition (n = 15)], we applied mechanical pain stimuli before, directly after, 10 min and 20 min after HFS in the skin area surrounding the conditioning area, and measured the reported pain intensity [visual analogue scale (VAS)]. All subjects (of both conditions) received a written instruction about the HFS protocol, but only the instruction in the nocebo condition was extended by the following text (in Dutch): 'After the HFS, your skin will become more sensitive to the pinprick stimulation'. RESULTS Our results clearly show that induced expectations of increased mechanical pain sensitivity after HFS facilitates the reported pain intensity after HFS more than when no information is given. CONCLUSIONS This study shows for the first time that brain mechanisms, via the induction of negative expectations, can facilitate heterotopic mechanical hyperalgesia after HFS of human skin.
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Affiliation(s)
- E N van den Broeke
- Donders Institute for Brain, Cognition, and Behaviour, Radboud University Nijmegen, The Netherlands
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38
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Cleary DR, Heinricher MM. Adaptations in responsiveness of brainstem pain-modulating neurons in acute compared with chronic inflammation. Pain 2013; 154:845-55. [PMID: 23588008 PMCID: PMC3661698 DOI: 10.1016/j.pain.2013.02.019] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Revised: 01/15/2013] [Accepted: 02/19/2013] [Indexed: 12/23/2022]
Abstract
Despite similar behavioral hypersensitivity, acute and chronic pain have distinct neural bases. We used intraplantar injection of complete Freund's adjuvant to directly compare activity of pain-modulating neurons in the rostral ventromedial medulla (RVM) in acute vs chronic inflammation. Heat-evoked and von Frey-evoked withdrawal reflexes and corresponding RVM neuronal activity were recorded in lightly anesthetized animals either during the first hour after complete Freund's adjuvant injection (acute) or 3 to 10 days later (chronic). Thermal and modest mechanical hyperalgesia during acute inflammation were associated with increases in the spontaneous activity of pain-facilitating ON-cells and suppression of pain-inhibiting OFF-cells. Acute hyperalgesia was reversed by RVM block, showing that the increased activity of RVM ON-cells is necessary for acute behavioral hypersensitivity. In chronic inflammation, thermal hyperalgesia had resolved but mechanical hyperalgesia had become pronounced. The spontaneous discharges of ON- and OFF-cells were not different from those in control subjects, but the mechanical response thresholds for both cell classes were reduced into the innocuous range. RVM block in the chronic condition worsened mechanical hyperalgesia. These studies identify distinct contributions of RVM ON- and OFF-cells to acute and chronic inflammatory hyperalgesia. During early immune-mediated inflammation, ON-cell spontaneous activity promotes hyperalgesia. After inflammation is established, the antinociceptive influence of OFF-cells is dominant, yet the lowered threshold for the OFF-cell pause allows behavioral responses to stimuli that would normally be considered innocuous. The efficacy of OFF-cells in counteracting sensitization of ascending transmission pathways could therefore be an important determining factor in development of chronic inflammatory pain.
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Affiliation(s)
- Daniel R Cleary
- Department of Neurological Surgery, Oregon Health & Science University, Portland, OR, USA.
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Wen D, Zang G, Sun D, Yang S, Yu F, Li S, Ma C, Cong B. Effects of CCK-8 on the reinstatement of morphine-induced CPP and expression of behavioral sensitization in rats. Neuroscience 2013; 238:230-41. [DOI: 10.1016/j.neuroscience.2013.02.057] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Revised: 02/20/2013] [Accepted: 02/21/2013] [Indexed: 10/27/2022]
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40
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Wagner KM, Roeder Z, Desrochers K, Buhler AV, Heinricher MM, Cleary DR. The dorsomedial hypothalamus mediates stress-induced hyperalgesia and is the source of the pronociceptive peptide cholecystokinin in the rostral ventromedial medulla. Neuroscience 2013; 238:29-38. [PMID: 23415792 DOI: 10.1016/j.neuroscience.2013.02.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Revised: 01/18/2013] [Accepted: 02/05/2013] [Indexed: 12/31/2022]
Abstract
While intense or highly arousing stressors have long been known to suppress pain, relatively mild or chronic stress can enhance pain. The mechanisms underlying stress-induced hyperalgesia (SIH) are only now being defined. The physiological and neuroendocrine effects of mild stress are mediated by the dorsomedial hypothalamus (DMH), which has documented connections with the rostral ventromedial medulla (RVM), a brainstem region capable of facilitating nociception. We hypothesized that stress engages both the DMH and the RVM to produce hyperalgesia. Direct pharmacological activation of the DMH increased sensitivity to mechanical stimulation in awake animals, confirming that the DMH can mediate behavioral hyperalgesia. A behavioral model of mild stress also produced mechanical hyperalgesia, which was blocked by inactivation of either the DMH or the RVM. The neuropeptide cholecystokinin (CCK) acts in the RVM to enhance nociception and is abundant in the DMH. Using a retrograde tracer and immunohistochemical labeling, we determined that CCK-expressing neurons in the DMH are the only significant supraspinal source of CCK in the RVM. However, not all neurons projecting from the DMH to the RVM contained CCK, and microinjection of the CCK2 receptor antagonist YM022 in the RVM did not interfere with SIH, suggesting that transmitters in addition to CCK play a significant role in this connection during acute stress. While the RVM has a well-established role in facilitation of nociception, the DMH, with its well-documented role in stress, may also be engaged in a number of chronic or abnormal pain states. Taken as a whole, these findings establish an anatomical and functional connection between the DMH and RVM by which stress can facilitate pain.
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Affiliation(s)
- K M Wagner
- Department of Neurological Surgery, Oregon Health & Science University, Portland, OR, USA
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41
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Ossipov MH. The perception and endogenous modulation of pain. SCIENTIFICA 2012; 2012:561761. [PMID: 24278716 PMCID: PMC3820628 DOI: 10.6064/2012/561761] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Accepted: 11/19/2012] [Indexed: 06/02/2023]
Abstract
Pain is often perceived an unpleasant experience that includes sensory and emotional/motivational responses. Accordingly, pain serves as a powerful teaching signal enabling an organism to avoid injury, and is critical to survival. However, maladaptive pain, such as neuropathic or idiopathic pain, serves no survival function. Genomic studies of individuals with congenital insensitivity to pain or paroxysmal pain syndromes considerable increased our understanding of the function of peripheral nociceptors, and especially of the roles of voltage-gated sodium channels and of nerve growth factor (NGF)/TrkA receptors in nociceptive transduction and transmission. Brain imaging studies revealed a "pain matrix," consisting of cortical and subcortical regions that respond to noxious inputs and can positively or negatively modulate pain through activation of descending pain modulatory systems. Projections from the periaqueductal grey (PAG) and the rostroventromedial medulla (RVM) to the trigeminal and spinal dorsal horns can inhibit or promote further nociceptive inputs. The "pain matrix" can explain such varied phenomena as stress-induced analgesia, placebo effect and the role of expectation on pain perception. Disruptions in these systems may account for the existence idiopathic pan states such as fibromyalgia. Increased understanding of pain modulatory systems will lead to development of more effective therapeutics for chronic pain.
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Affiliation(s)
- Michael H. Ossipov
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, AZ 85724, USA
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Khasabov SG, Brink TS, Schupp M, Noack J, Simone DA. Changes in response properties of rostral ventromedial medulla neurons during prolonged inflammation: modulation by neurokinin-1 receptors. Neuroscience 2012; 224:235-48. [PMID: 22917610 PMCID: PMC3498481 DOI: 10.1016/j.neuroscience.2012.08.029] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Revised: 08/10/2012] [Accepted: 08/14/2012] [Indexed: 01/05/2023]
Abstract
Activation of neurokinin-1 (NK-1) receptors in the rostral ventromedial medulla (RVM) can facilitate pain transmission in conditions such as inflammation, and thereby contribute to hyperalgesia. Since blockade of NK-1 receptors in the RVM can attenuate hyperalgesia produced by prolonged inflammation, we examined the role of NK-1 receptors in changes of response properties of RVM neurons following four days of hind paw inflammation with complete Freund's adjuvant. Recordings were made from functionally identified ON, OFF and NEUTRAL cells in the RVM. Spontaneous activity and responses evoked by a series of mechanical (10, 15, 26, 60, 100, and 180 g) and heat (34-50 °C) stimuli applied to the inflamed and non-inflamed hind paws were determined before and at 15 and 60 min after injection of the NK-1-antagonist L-733,060 or vehicle into the RVM. Prolonged inflammation did not alter the proportions of functionally-identified ON, OFF and NEUTRAL cells. ON cells exhibited enhanced responses to mechanical (60-100g) and heat (48-50 °C) stimuli applied to the inflamed paw, which were attenuated by L-733,060 but not by vehicle. Inhibitory responses of OFF cells evoked by mechanical stimuli applied to the inflamed paw were also inhibited by L-733,060, but responses evoked by stimulation of the contralateral paw were increased. Heat-evoked responses of OFF cells were not altered by L-733,060. Also, neither L-733,060 nor vehicle altered spontaneous ongoing discharge rate of RVM neurons. These data indicate that NK-1 receptors modulate excitability of ON cells which contribute to both mechanical and heat hyperalgesia, whereas NK-1 modulation of OFF cells contributes to mechanical hyperalgesia during prolonged inflammation.
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Affiliation(s)
- S G Khasabov
- Department of Diagnostic & Biological Sciences, University of Minnesota, School of Dentistry, Minneapolis, MN 55455, United States
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Effects of exogenous cholecystokinin octapeptide on acquisition of naloxone precipitated withdrawal induced conditioned place aversion in rats. PLoS One 2012; 7:e41860. [PMID: 22848639 PMCID: PMC3407117 DOI: 10.1371/journal.pone.0041860] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Accepted: 06/26/2012] [Indexed: 11/22/2022] Open
Abstract
Cholecystokinin octapeptide (CCK-8), a gut-brain peptide, regulates a variety of physiological behavioral processes. Previously, we reported that exogenous CCK-8 attenuated morphine-induced conditioned place preference, but the possible effects of CCK-8 on aversively motivated drug seeking remained unclear. To investigate the effects of endogenous and exogenous CCK on negative components of morphine withdrawal, we evaluated the effects of CCK receptor antagonists and CCK-8 on the naloxone-precipitated withdrawal-induced conditioned place aversion (CPA). The results showed that CCK2 receptor antagonist (LY-288,513, 10 µg, i.c.v.), but not CCK1 receptor antagonist (L-364,718, 10 µg, i.c.v.), inhibited the acquisition of CPA when given prior to naloxone (0.3 mg/kg) administration in morphine-dependent rats. Similarly, CCK-8 (0.1–1 µg, i.c.v.) significantly attenuated naloxone-precipitated withdrawal-induced CPA, and this inhibitory function was blocked by co-injection with L-364,718. Microinjection of L-364,718, LY-288,513 or CCK-8 to saline pretreated rats produced neither a conditioned preference nor aversion, and the induction of CPA by CCK-8 itself after morphine pretreatments was not significant. Our study identifies a different role of CCK1 and CCK2 receptors in negative affective components of morphine abstinence and an inhibitory effect of exogenous CCK-8 on naloxone-precipitated withdrawal-induced CPA via CCK1 receptor.
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Godínez-Chaparro B, López-Santillán FJ, Orduña P, Granados-Soto V. Secondary mechanical allodynia and hyperalgesia depend on descending facilitation mediated by spinal 5-HT₄, 5-HT₆ and 5-HT₇ receptors. Neuroscience 2012; 222:379-91. [PMID: 22796074 DOI: 10.1016/j.neuroscience.2012.07.008] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Revised: 07/03/2012] [Accepted: 07/03/2012] [Indexed: 12/26/2022]
Abstract
In the present study we determined the role of spinal 5-hydroxytriptamine (5-HT) and 5-HT(4/6/7) receptors in the long-term secondary mechanical allodynia and hyperalgesia induced by formalin in the rat. Formalin produced acute nociceptive behaviors (flinching and licking/lifting) followed by long-term secondary mechanical allodynia and hyperalgesia in both paws. In addition, formalin increased the tissue content of 5-HT in the ipsilateral, but not contralateral, dorsal part of the spinal cord compared to control animals. Intrathecal (i.t.) administration of 5,7-dihydroxytriptamine (5,7-DHT), a serotonergic neurotoxin, diminished tissue 5-HT content in the ipsilateral and contralateral dorsal parts of the spinal cord. Accordingly, i.t. 5,7-DHT prevented formalin-induced secondary allodynia and hyperalgesia in both paws. I.t. pre-treatment (-10 min) with ML-10302 (5-HT(4) agonist), EMD-386088 (5-HT(6) agonist) and LP-12 (5-HT(7) agonist) significantly increased secondary mechanical allodynia and hyperalgesia in both paws. In contrast, i.t. pre-treatment (-20 min) with GR-125487 (5-HT(4) antagonist), SB-258585 (5-HT(6) antagonist) and SB-269970 (5-HT(7) antagonist) significantly prevented formalin-induced long-term effects in both paws. In addition, these antagonists prevented the pro-nociceptive effect of ML-10302, EMD-386088 and LP-12, respectively. The i.t. post-treatment (6 days after formalin injection) with GR-125487, SB-258585 and SB-269970 reversed formalin-induced secondary allodynia and hyperalgesia in both paws. These results suggest that spinal 5-HT, released from the serotonergic projections in response to formalin injection, activates pre- or post-synaptic 5-HT(4/6/7) receptors at the dorsal root ganglion/spinal cord promoting the development and maintenance of secondary allodynia and hyperalgesia.
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Affiliation(s)
- B Godínez-Chaparro
- Departamento de Farmacobiología, Centro de Investigación y de Estudios Avanzados (Cinvestav), Sede Sur, México, DF, Mexico
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Wen D, Ma CL, Zhang YJ, Meng YX, Ni ZY, Li SJ, Cong B. Cholecystokinin receptor-1 mediates the inhibitory effects of exogenous cholecystokinin octapeptide on cellular morphine dependence. BMC Neurosci 2012; 13:63. [PMID: 22682150 PMCID: PMC3407485 DOI: 10.1186/1471-2202-13-63] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Accepted: 06/08/2012] [Indexed: 11/16/2022] Open
Abstract
Background Cholecystokinin octapeptide (CCK-8), the most potent endogenous anti-opioid peptide, has been shown to regulate the processes of morphine dependence. In our previous study, we found that exogenous CCK-8 attenuated naloxone induced withdrawal symptoms. To investigate the precise effect of exogenous CCK-8 and the role of cholecystokinin (CCK) 1 and/or 2 receptors in morphine dependence, a SH-SY5Y cell model was employed, in which the μ-opioid receptor, CCK1/2 receptors, and endogenous CCK are co-expressed. Results Forty-eight hours after treating SH-SY5Y cells with morphine (10 μM), naloxone (10 μM) induced a cAMP overshoot, indicating that cellular morphine dependence had been induced. The CCK receptor and endogenous CCK were up-regulated after chronic morphine exposure. The CCK2 receptor antagonist (LY-288,513) at 1–10 μM inhibited the naloxone-precipitated cAMP overshoot, but the CCK1 receptor antagonist (L-364,718) did not. Interestingly, CCK-8 (0.1-1 μM), a strong CCK receptor agonist, dose-dependently inhibited the naloxone-precipitated cAMP overshoot in SH-SY5Y cells when co-pretreated with morphine. The L-364,718 significantly blocked the inhibitory effect of exogenous CCK-8 on the cAMP overshoot at 1–10 μM, while the LY-288,513 did not. Therefore, the CCK2 receptor appears to be necessary for low concentrations of endogenous CCK to potentiate morphine dependence in SH-SY5Y cells. An additional inhibitory effect of CCK-8 at higher concentrations appears to involve the CCK1 receptor. Conclusions This study reveals the difference between exogenous CCK-8 and endogenous CCK effects on the development of morphine dependence, and provides the first evidence for the participation of the CCK1 receptor in the inhibitory effects of exogenous CCK-8 on morphine dependence.
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Affiliation(s)
- Di Wen
- Department of Forensic Medicine, Hebei Medical University, Hebei Key Laboratory of Forensic Medicine, Shijiazhuang 050017, PR China
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Wen D, Cong B, Ma C, Yang S, Yu H, Ni Z, Li S. The effects of exogenous CCK-8 on the acquisition and expression of morphine-induced CPP. Neurosci Lett 2012; 510:24-8. [PMID: 22245440 DOI: 10.1016/j.neulet.2011.12.063] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Revised: 11/17/2011] [Accepted: 12/29/2011] [Indexed: 11/27/2022]
Abstract
Cholecystokinin octapeptide (CCK-8) is the most potent endogenous anti-opioid peptide and regulates a variety of physiological processes. In our previous study, we found that exogenous CCK-8 attenuated naloxone-induced withdrawal symptoms, but the possible regulative effects of CCK-8 on the rewarding effects of morphine were not examined. In the present study, we aimed to determine the exact effects of exogenous CCK-8 at various doses on the rewarding action of morphine by utilizing the unbiased conditioned place preference (CPP) paradigm. We therefore examined the effects of CCK-8 on the acquisition, expression and extinction of morphine-induced CPP and on locomotor activity. The results showed that CCK-8 (0.01-1μg, i.c.v.), administered alone, induced neither CPP nor place aversion, but blocked the acquisition of CPP when administered with 10mg/kg morphine. The highest dose of CCK-8 (1μg) administered before CPP testing increased CPP and, along with lower doses (0.1μg), reduced its extinction. In addition, the highest dose (1μg) of CCK-8 suppressed locomotor activity. Our study provides the first behavioral evidence for the inhibitory effects of exogenous CCK-8 on rewarding activity and reveals significant effects of exogenous CCK-8 on various stages of place preference and the development of opioid dependence.
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Affiliation(s)
- Di Wen
- Department of Forensic Medicine, Hebei Medical University, Hebei Key Laboratory of Forensic Medicine, Shijiazhuang 050017, PR China
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Akbari E. The role of cyclo-oxygenase inhibitors in attenuating opioid-induced tolerance, hyperalgesia, and dependence. Med Hypotheses 2011; 78:102-6. [PMID: 22047988 DOI: 10.1016/j.mehy.2011.10.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Revised: 08/21/2011] [Accepted: 10/04/2011] [Indexed: 11/28/2022]
Abstract
There is no denying that opioids are the most important analgesic drugs which are widely used in clinical situations. Still, prolonged administration of these drugs can cause to reduce their analgesic efficacy due to the development of tolerance. These drugs can also cause induction of hyperalgesia. In addition, long-term administration of opioids through reinforcing- and rewarding pathways of limbic system can result in expression of opioid dependence with the unintended consequences of opioid abuse/misuse and finally opioid addiction. As studies show, over-activity in cyclo-oxygenase pathways and production of prostaglandins due to long-term exposures of opioid have a critical role in the development of tolerance to antinociceptive effect of opioid, hyperalgesia, and opioid dependence. The present study aims at suggesting the hypothesis that through blending a non-steroid anti-inflammatory drug with opioid actively causes reduction in unwanted effects of opioid i.e. by inhibition of opioid-induced cyclo-oxygenase overactivity whereas it is well-known that the combination therapy via reducing opioid dosage reduces the unwanted effects.
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Affiliation(s)
- Esmaeil Akbari
- Department of Physiology, Molecular and Cell Biology Research Center, School of Medicine, Mazandaran University of Medical Sciences, Sari, Iran.
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Brink TS, Pacharinsak C, Khasabov SG, Beitz AJ, Simone DA. Differential modulation of neurons in the rostral ventromedial medulla by neurokinin-1 receptors. J Neurophysiol 2011; 107:1210-21. [PMID: 22031765 DOI: 10.1152/jn.00678.2011] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The rostral ventromedial medulla (RVM) is part of descending circuitry that modulates nociceptive processing at the level of the spinal cord. RVM output can facilitate pain transmission under certain conditions such as inflammation, and thereby contribute to hyperalgesia. Evidence suggests that substance P and activation of neurokinin-1 (NK-1) receptors in the RVM are involved in descending facilitation of nociception. We showed previously that injection of NK-1 receptor antagonists into the RVM attenuated mechanical and heat hyperalgesia produced by intraplantar injection of capsaicin. Furthermore, intraplantar injection of capsaicin excited ON cells in the RVM and inhibited ongoing activity of OFF cells. In the present studies, we therefore examined changes in responses of RVM neurons to mechanical and heat stimuli after intraplantar injection of capsaicin and determined the role of NK-1 receptors by injecting a NK-1 receptor antagonist into the RVM prior to capsaicin. After capsaicin injection, excitatory responses of ON cells and inhibitory responses of OFF cells evoked by mechanical and heat stimuli applied to the injected, but not contralateral, paw were increased. Injection of the NK-1 antagonist L-733,060 did not alter evoked responses of ON or OFF cells but attenuated the capsaicin-evoked enhanced responses of ON cells to mechanical and heat stimuli with less of an effect on the enhanced inhibitory responses of OFF cells. These data support the notion that descending facilitation from RVM contributes to hyperalgesia and that NK-1 receptors, presumably located on ON cells, play an important role in initiating descending facilitation of nociceptive transmission.
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Affiliation(s)
- Thaddeus S Brink
- Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis 55455, USA
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Marshall TM, Herman DS, Largent-Milnes TM, Badghisi H, Zuber K, Holt SC, Lai J, Porreca F, Vanderah TW. Activation of descending pain-facilitatory pathways from the rostral ventromedial medulla by cholecystokinin elicits release of prostaglandin-E₂ in the spinal cord. Pain 2011; 153:86-94. [PMID: 22030324 DOI: 10.1016/j.pain.2011.09.021] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Revised: 09/20/2011] [Accepted: 09/21/2011] [Indexed: 11/18/2022]
Abstract
Cholecystokinin (CCK) has been suggested to be both pro-nociceptive and "anti-opioid" by actions on pain-modulatory cells within the rostral ventromedial medulla (RVM). One consequence of activation of RVM CCK₂ receptors may be enhanced spinal nociceptive transmission; but how this might occur, especially in states of pathological pain, is unknown. Here, in vivo microdialysis was used to demonstrate that levels of RVM CCK increased by approximately 2-fold after ligation of L₅/L₆ spinal nerves (SNL). Microinjection of CCK into the RVM of naïve rats elicited hypersensitivity to tactile stimulation of the hindpaw. In addition, RVM CCK elicited a time-related increase in (prostaglandin-E₂) PGE₂ measured in cerebrospinal fluid from the lumbar spinal cord. The peak increase in spinal PGE₂ was approximately 5-fold and was observed at approximately 80 minutes post-RVM CCK, a time coincident with maximal RVM CCK-induced mechanical hypersensitivity. Spinal administration of naproxen, a nonselective COX-inhibitor, significantly attenuated RVM CCK-induced hindpaw tactile hypersensitivity. RVM-CCK also resulted in a 2-fold increase in spinal 5-hydroxyindoleacetic acid (5-HIAA), a 5-hydoxytryptophan (5-HT) metabolite, as compared with controls, and mechanical hypersensitivity that was attenuated by spinal application of ondansetron, a 5-HT₃ antagonist. The present studies suggest that chronic nerve injury can result in activation of descending facilitatory mechanisms that may promote hyperalgesia via ultimate release of PGE₂ and 5-HT in the spinal cord.
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Affiliation(s)
- Timothy M Marshall
- Department of Pharmacology, University of Arizona Health Sciences Center, College of Medicine, Tucson, AZ, USA
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Maione S, Piscitelli F, Gatta L, Vita D, De Petrocellis L, Palazzo E, de Novellis V, Di Marzo V. Non-psychoactive cannabinoids modulate the descending pathway of antinociception in anaesthetized rats through several mechanisms of action. Br J Pharmacol 2011; 162:584-96. [PMID: 20942863 DOI: 10.1111/j.1476-5381.2010.01063.x] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND AND PURPOSE Two non-psychoactive cannabinoids, cannabidiol (CBD) and cannabichromene (CBC), are known to modulate in vitro the activity of proteins involved in nociceptive mechanisms, including transient receptor potential (TRP) channels of vanilloid type-1 (TRPV1) and of ankyrin type-1 (TRPA1), the equilibrative nucleoside transporter and proteins facilitating endocannabinoid inactivation. Here we have tested these two cannabinoids on the activity of the descending pathway of antinociception. EXPERIMENTAL APPROACH Electrical activity of ON and OFF neurons of the rostral ventromedial medulla in anaesthetized rats was recorded extracellularly and tail flick latencies to thermal stimuli were measured. CBD or CBC along with various antagonists were injected into the ventrolateral periaqueductal grey. KEY RESULTS Cannabidiol and CBC dose-dependently reduced the ongoing activity of ON and OFF neurons in anaesthetized rats, whilst inducing antinociceptive responses in the tail flick-test. These effects were maximal with 3 nmol CBD and 6 nmol CBC, and were antagonized by selective antagonists of cannabinoid CB(1) adenosine A(1) and TRPA1, but not of TRPV1, receptors. Both CBC and CBD also significantly elevated endocannabinoid levels in the ventrolateral periaqueductal grey. A specific agonist at TRPA1 channels and a synthetic inhibitor of endocannabinoid cellular reuptake exerted effects similar to those of CBC and CBD. CONCLUSIONS AND IMPLICATIONS CBD and CBC stimulated descending pathways of antinociception and caused analgesia by interacting with several target proteins involved in nociceptive control. These compounds might represent useful therapeutic agents with multiple mechanisms of action.
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Affiliation(s)
- Sabatino Maione
- Endocannabinoid Research Group, Department of Experimental Medicine - Division of Pharmacology 'L. Donatelli', Second University of Naples, Naples, Italy
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