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Dagher M, Alayoubi M, Sigal GH, Cahill CM. Unveiling the link between chronic pain and misuse of opioids and cannabis. J Neural Transm (Vienna) 2024; 131:563-580. [PMID: 38570361 DOI: 10.1007/s00702-024-02765-3] [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: 11/30/2023] [Accepted: 03/10/2024] [Indexed: 04/05/2024]
Abstract
Over 50 million Americans endure chronic pain where many do not receive adequate treatment and self-medicate to manage their pain by taking substances like opioids and cannabis. Research has shown high comorbidity between chronic pain and substance use disorders (SUD) and these disorders share many common neurobiological underpinnings, including hypodopaminergic transmission. Drugs commonly used for self-medication such as opioids and cannabis relieve emotional, bothersome components of pain as well as negative emotional affect that perpetuates misuse and increases the risk of progressing towards drug abuse. However, the causal effect between chronic pain and the development of SUDs has not been clearly established. In this review, we discuss evidence that affirms the proposition that chronic pain is a risk factor for the development of opioid and cannabis use disorders by outlining the clinical evidence and detailing neurobiological mechanisms that link pain and drug misuse. Central to the link between chronic pain and opioid and cannabis misuse is hypodopaminergic transmission and the modulation of dopamine signaling in the mesolimbic pathway by opioids and cannabis. Moreover, we discuss the role of kappa opioid receptor activation and neuroinflammation in the context of dopamine transmission, their contribution to opioid and cannabis withdrawal, along with potential new treatments.
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Affiliation(s)
- Merel Dagher
- MacDonald Research Laboratory Building, Department of Psychiatry and Biobehavioral Sciences, Shirley and Stefan Hatos Center for Neuropharmacology, Semel Institute for Neuroscience and Human Behavior, University of California Los Angeles, 675 Charles E Young Drive South, Office 2774, Los Angeles, CA, 90095, USA
| | - Myra Alayoubi
- MacDonald Research Laboratory Building, Department of Psychiatry and Biobehavioral Sciences, Shirley and Stefan Hatos Center for Neuropharmacology, Semel Institute for Neuroscience and Human Behavior, University of California Los Angeles, 675 Charles E Young Drive South, Office 2774, Los Angeles, CA, 90095, USA
- Neuroscience Interdepartmental Program, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Gabriella H Sigal
- Department of Integrative Biology and Physiology, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Catherine M Cahill
- MacDonald Research Laboratory Building, Department of Psychiatry and Biobehavioral Sciences, Shirley and Stefan Hatos Center for Neuropharmacology, Semel Institute for Neuroscience and Human Behavior, University of California Los Angeles, 675 Charles E Young Drive South, Office 2774, Los Angeles, CA, 90095, USA.
- Neuroscience Interdepartmental Program, University of California Los Angeles, Los Angeles, CA, 90095, USA.
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2
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Pearl-Dowler L, Posa L, Lopez-Canul M, Teggin A, Gobbi G. Anti-allodynic and medullary modulatory effects of a single dose of delta-9-tetrahydrocannabinol (THC) in neuropathic rats tolerant to morphine. Prog Neuropsychopharmacol Biol Psychiatry 2023; 127:110805. [PMID: 37257771 DOI: 10.1016/j.pnpbp.2023.110805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 05/24/2023] [Accepted: 05/25/2023] [Indexed: 06/02/2023]
Abstract
Neuropathic pain (NP) is often treated with opioids, the prolonged use of which causes tolerance to their analgesic effect and can potentially cause death by overdose. The phytocannabinoid delta-9-tetrahydrocannabinol (THC) may be an effective alternative analgesic to treat NP in morphine-tolerant subjects. Male Wistar rats developed NP after spared nerve injury, and were then treated with increasing doses of THC (1, 1.5, 2, 2.5, and 5 mg/kg, intraperitoneally), which reduced mechanical allodynia at the dose of 2.5 and 5 mg/kg. Another group of NP rats were treated with morphine (5 mg/kg, twice daily for 7 days, subcutaneously), until tolerance developed, and on day 8 received a single dose of THC (2.5 mg/kg), which significantly reduced mechanical allodynia. To evaluate the modulation of THC in the descending pain pathway, in vivo electrophysiological recordings of pronociceptive ON cells and antinociceptive OFF cells in the rostroventral medulla (RVM) were recorded after intra-PAG microinjection of THC (10 μg/μl). NP rats with morphine tolerance, compared to the control one, showed a tonic reduction of the spontaneous firing rate of ON cells by 44%, but the THC was able to further decrease it (a hallmark of many analgesic drugs acting at supraspinal level). On the other hand, the firing rate, of the antinociceptive OFF cells was increased after morphine tolerance by 133%, but the THC failed to further activate it. Altogether, these findings indicate that a single dose of THC produces antiallodynic effect in individuals with NP who are tolerant to morphine, acting mostly on the ON cells of the descending pain pathways, but not on OFF cells.
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Affiliation(s)
- Leora Pearl-Dowler
- Neurobiological Psychiatry Unit, Department of Psychiatry, McGill University Health Center, McGill University, Montreal, QC, Canada
| | - Luca Posa
- Neurobiological Psychiatry Unit, Department of Psychiatry, McGill University Health Center, McGill University, Montreal, QC, Canada; Alan Edwards Centre for Research on Pain, McGill University, Montreal, QC, Canada
| | - Martha Lopez-Canul
- Neurobiological Psychiatry Unit, Department of Psychiatry, McGill University Health Center, McGill University, Montreal, QC, Canada
| | - Alexandra Teggin
- Neurobiological Psychiatry Unit, Department of Psychiatry, McGill University Health Center, McGill University, Montreal, QC, Canada
| | - Gabriella Gobbi
- Neurobiological Psychiatry Unit, Department of Psychiatry, McGill University Health Center, McGill University, Montreal, QC, Canada; Alan Edwards Centre for Research on Pain, McGill University, Montreal, QC, Canada.
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3
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Slivicki RA, Wang JG, Nhat VTT, Kravitz AV, Creed MC, Gereau RW. Impact of Δ 9-Tetrahydrocannabinol and oxycodone co-administration on measures of antinociception, dependence, circadian activity, and reward in mice. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.04.569809. [PMID: 38105953 PMCID: PMC10723318 DOI: 10.1101/2023.12.04.569809] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
Oxycodone is commonly prescribed for moderate to severe pain disorders. While efficacious, long-term use can result in tolerance, physical dependence, and the development of opioid use disorder. Cannabis and its derivatives such as Δ9-Tetrahydrocannabinol (Δ9-THC) have been reported to enhance oxycodone analgesia in animal models and in humans. However, it remains unclear if Δ9-THC may facilitate unwanted aspects of oxycodone intake, such as tolerance, dependence, and reward at analgesic doses. This study sought to evaluate the impact of co-administration of Δ9-THC and oxycodone across behavioral measures related to antinociception, dependence, circadian activity, and reward in both male and female mice. Oxycodone and Δ9-THC produced dose-dependent antinociceptive effects in the hotplate assay that were similar between sexes. Repeated treatment (twice daily for 5 days) resulted in antinociceptive tolerance. Combination treatment of oxycodone and Δ9-THC produced a greater antinociceptive effect than either administered alone, and delayed the development of antinociceptive tolerance. Repeated treatment with oxycodone produced physical dependence and alterations in circadian activity, neither of which were exacerbated by co-treatment with Δ9-THC. Combination treatment of oxycodone and Δ9-THC produced CPP when co-administered at doses that did not produce preference when administered alone. These data indicate that Δ9-THC may facilitate oxycodone-induced antinociception without augmenting certain unwanted features of opioid intake (e.g. dependence, circadian rhythm alterations). However, our findings also indicate that Δ9-THC may facilitate rewarding properties of oxycodone at therapeutically relevant doses which warrant consideration when evaluating this combination for its potential therapeutic utility.
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Affiliation(s)
- Richard A. Slivicki
- Washington University Pain Center and Department of Anesthesiology, Washington University, St. Louis, MO
| | - Justin G. Wang
- Washington University Pain Center and Department of Anesthesiology, Washington University, St. Louis, MO
- Neuroscience Graduate Program, Division of Biology & Biomedical Sciences, Washington University, St. Louis, MO
| | - Vy Trinh Tran Nhat
- Washington University Pain Center and Department of Anesthesiology, Washington University, St. Louis, MO
| | - Alexxai V. Kravitz
- Washington University Pain Center and Department of Anesthesiology, Washington University, St. Louis, MO
- Department of Psychiatry, Washington University, St. Louis, MO
- Department of Neuroscience, Washington University, St. Louis, MO
| | - Meaghan C. Creed
- Washington University Pain Center and Department of Anesthesiology, Washington University, St. Louis, MO
- Department of Neuroscience, Washington University, St. Louis, MO
| | - Robert W. Gereau
- Washington University Pain Center and Department of Anesthesiology, Washington University, St. Louis, MO
- Department of Neuroscience, Washington University, St. Louis, MO
- Department of Biomedical Engineering, Washington University, St. Louis, MO
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Briânis RC, Andreotti JP, Moreira FA, Iglesias LP. Interplay between endocannabinoid and endovanilloid mechanisms in fear conditioning. Acta Neuropsychiatr 2023:1-10. [PMID: 37982167 DOI: 10.1017/neu.2023.54] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/21/2023]
Abstract
OBJECTIVE The transient receptor potential cation channel, subfamily V (vanilloid), member 1 (TRPV1) mediates pain perception to thermal and chemical stimuli in peripheral neurons. The cannabinoid receptor type 1 (CB1), on the other hand, promotes analgesia in both the periphery and the brain. TRPV1 and CB1 have also been implicated in learned fear, which involves the association of a previously neutral stimulus with an aversive event. In this review, we elaborate on the interplay between CB1 receptors and TRPV1 channels in learned fear processing. METHODS We conducted a PubMed search for a narrative review on endocannabinoid and endovanilloid mechanisms on fear conditioning. RESULTS TRPV1 and CB1 receptors are activated by a common endogenous agonist, arachidonoyl ethanolamide (anandamide), Moreover, they are expressed in common neuroanatomical structures and recruit converging cellular pathways, acting in concert to modulate fear learning. However, evidence suggests that TRPV1 exerts a facilitatory role, whereas CB1 restrains fear responses. CONCLUSION TRPV1 and CB1 seem to mediate protective and aversive roles of anandamide, respectively. However, more research is needed to achieve a better understanding of how these receptors interact to modulate fear learning.
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Affiliation(s)
- Rayssa C Briânis
- Department of Pharmacology, Institute of Biological Sciences; Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Julia P Andreotti
- Department of Pharmacology, Institute of Biological Sciences; Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Fabrício A Moreira
- Department of Pharmacology, Institute of Biological Sciences; Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Lia P Iglesias
- Department of Pharmacology, Institute of Biological Sciences; Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
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Bouchet CA, McPherson KB, Coutens B, Janowsky A, Ingram SL. Monoacylglycerol Lipase Protects the Presynaptic Cannabinoid 1 Receptor from Desensitization by Endocannabinoids after Persistent Inflammation. J Neurosci 2023; 43:5458-5467. [PMID: 37414560 PMCID: PMC10376933 DOI: 10.1523/jneurosci.0037-23.2023] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Revised: 06/08/2023] [Accepted: 06/28/2023] [Indexed: 07/08/2023] Open
Abstract
Cannabinoid-targeted pain therapies are increasing with the expansion of cannabis legalization, however, their efficacy may be limited by pain-induced adaptations in the cannabinoid system. Cannabinoid receptor subtype 1 (CB1R) inhibition of spontaneous, GABAergic miniature IPSCs (mIPSCs) and evoked IPSCs (eIPSCs) in the ventrolateral periaqueductal gray (vlPAG) were compared in slices from naive and inflamed male and female Sprague Dawley rats. Complete Freund's Adjuvant (CFA) injections into the hindpaw induced persistent inflammation. In naive rats, exogenous cannabinoid agonists robustly reduce both eIPSCs and mIPSCs. After 5-7 d of inflammation, the effects of exogenous cannabinoids are significantly reduced because of CB1R desensitization via GRK2/3, as function is recovered in the presence of the GRK2/3 inhibitor, Compound 101 (Cmp101). Inhibition of GABA release by presynaptic μ-opioid receptors in the vlPAG does not desensitize with persistent inflammation. Unexpectedly, while CB1R desensitization significantly reduces the inhibition produced by exogenous agonists, depolarization-induced suppression of inhibition protocols that promote 2-arachidonoylglycerol (2-AG) synthesis exhibit prolonged CB1R activation after inflammation. 2-AG tone is detected in slices from CFA-treated rats when GRK2/3 is blocked, suggesting an increase in 2-AG synthesis after persistent inflammation. Inhibiting 2-AG degradation with the monoacylglycerol lipase (MAGL) inhibitor JZL184 during inflammation results in the desensitization of CB1Rs by endocannabinoids that is reversed with Cmp101. Collectively, these data indicate that persistent inflammation primes CB1Rs for desensitization, and MAGL degradation of 2-AG protects CB1Rs from desensitization in inflamed rats. These adaptations with inflammation have important implications for the development of cannabinoid-based pain therapeutics targeting MAGL and CB1Rs.SIGNIFICANCE STATEMENT Presynaptic G-protein-coupled receptors are resistant to desensitization. Here we find that persistent inflammation increases endocannabinoid levels, priming presynaptic cannabinoid 1 receptors for desensitization on subsequent addition of exogenous agonists. Despite the reduced efficacy of exogenous agonists, endocannabinoids have prolonged efficacy after persistent inflammation. Endocannabinoids readily induce cannabinoid 1 receptor desensitization if their degradation is blocked, indicating that endocannabinoid concentrations are maintained at subdesensitizing levels and that degradation is critical for maintaining endocannabinoid regulation of presynaptic GABA release in the ventrolateral periaqueductal gray during inflammatory states. These adaptations with inflammation have important implications for the development of cannabinoid-based pain therapies.
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Affiliation(s)
- Courtney A Bouchet
- Department of Neurological Surgery, Oregon Health & Science University, Portland, Oregon 97239
- Neuroscience Graduate Program, Vollum Institute, Portland, Oregon 97239
| | - Kylie B McPherson
- Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045
| | - Basile Coutens
- Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045
| | - Aaron Janowsky
- Research Service, VA Portland Health Care System, Portland, Oregon 97239
- Departments of Psychiatry, and Behavioral Neuroscience, Oregon Health & Science University, Portland, Oregon 97239
| | - Susan L Ingram
- Department of Neurological Surgery, Oregon Health & Science University, Portland, Oregon 97239
- Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045
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Thrul J, Rabinowitz JA, Reboussin BA, Maher BS, Anthony JC, Ialongo NS. Longitudinal associations between age 20 problematic substance use and opioid use disorder incidence at age 30 - findings from an urban cohort. J Psychiatr Res 2023; 160:1-7. [PMID: 36764195 PMCID: PMC10023426 DOI: 10.1016/j.jpsychires.2023.01.033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 12/15/2022] [Accepted: 01/26/2023] [Indexed: 01/30/2023]
Abstract
This study used data from a longitudinal prevention study in an urban cohort to examine associations between nicotine dependence, alcohol, and cannabis use disorder and disorder criteria at age 20, with opioid use disorder (OUD) incidence or criteria onset by age 30. The study sample included 1408 participants (57.5% female, 72.5% African American) drawn from two cohorts of participants in a mid-Atlantic region of the U.S. as part of a series of randomized controlled trials of elementary school-based universal prevention interventions. Lifetime cannabis use disorder (CUD), alcohol use disorder (AUD; both DSM-IV), and current nicotine dependence (Fagerstrom Test for Nicotine Dependence, FTND) assessed at age 20 were used to predict (1) DSM-IV lifetime OUD at age 30, and (2) OUD criteria between ages 20 and 30 in multivariable logistic regression models. Covariates for all analyses included sociodemographics (sex, race, and free/reduced-priced lunch status), community disadvantage, and intervention status. Nicotine dependence (FTND≥3) at age 20 predicted age 30 DSM-IV lifetime OUD (aOR = 2.37; 95% CI 1.02,5.54). The number of CUD criteria (aOR = 1.30; 95% CI 1.09,1.57) and nicotine dependence severity scores (aOR = 1.22; 95% CI = 1.05,1.41) at age 20 predicted any OUD criteria between the ages of 20 and 30. Findings are consistent with previous research on opioid use behavior in young adulthood and suggest that nicotine dependence and CUD criteria among urban young people predict onset of OUD and OUD criteria in young adulthood.
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Affiliation(s)
- Johannes Thrul
- Department of Mental Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA; Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD, USA; Centre for Alcohol Policy Research, La Trobe University, Melbourne, Australia.
| | - Jill A Rabinowitz
- Department of Mental Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Beth A Reboussin
- Department of Biostatistics and Data Science, Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - Brion S Maher
- Department of Mental Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - James C Anthony
- Department of Mental Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA; Epidemiology & Biostatistics, College of Human Medicine, Michigan State University, East Lansing, MI, USA
| | - Nicholas S Ialongo
- Department of Mental Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
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Lee MT, Mackie K, Chiou LC. Alternative pain management via endocannabinoids in the time of the opioid epidemic: Peripheral neuromodulation and pharmacological interventions. Br J Pharmacol 2023; 180:894-909. [PMID: 34877650 PMCID: PMC9170838 DOI: 10.1111/bph.15771] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 11/23/2021] [Accepted: 11/27/2021] [Indexed: 01/18/2023] Open
Abstract
The use of opioids in pain management is hampered by the emergence of analgesic tolerance, which leads to increased dosing and side effects, both of which have contributed to the opioid epidemic. One promising potential approach to limit opioid analgesic tolerance is activating the endocannabinoid system in the CNS, via activation of CB1 receptors in the descending pain inhibitory pathway. In this review, we first discuss preclinical and clinical evidence revealing the potential of pharmacological activation of CB1 receptors in modulating opioid tolerance, including activation by phytocannabinoids, synthetic CB1 receptor agonists, endocannabinoid degradation enzyme inhibitors, and recently discovered positive allosteric modulators of CB1 receptors. On the other hand, as non-pharmacological pain relief is advocated by the US-NIH to combat the opioid epidemic, we also discuss contributions of peripheral neuromodulation, involving the electrostimulation of peripheral nerves, in addressing chronic pain and opioid tolerance. The involvement of supraspinal endocannabinoid systems in peripheral neuromodulation-induced analgesia is also discussed. LINKED ARTICLES: This article is part of a themed issue on Advances in Opioid Pharmacology at the Time of the Opioid Epidemic. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.7/issuetoc.
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Grants
- MOST 108-2321-B-002-005 Ministry of Science and Technology, Taiwan
- MOST 107-2811-B-002-008 Ministry of Science and Technology, Taiwan
- R01 DA041229 NIDA NIH HHS
- MOST 107-2321-B-002-010 Ministry of Science and Technology, Taiwan
- R01 DA047858 NIDA NIH HHS
- 107M4022-3 Ministry of Education, Taiwan
- MOST 106-2321-B-002-019 Ministry of Science and Technology, Taiwan
- NHRI-EX111-11114NI National Health Research Institutes, Taiwan
- FRGS/1/2021/WAB13/UCSI/02/1 Ministry of Higher Education, Malaysia
- R21 DA042584 NIDA NIH HHS
- REIG-FPS-2020/065 UCSI University Research Excellence and Innovation Grant, Malaysia
- NHRI-EX109-10733NI National Health Research Institutes, Taiwan
- MOST 104-2745-B-002-004 Ministry of Science and Technology, Taiwan
- MOST 109-2320-B-002-042-MY3 Ministry of Science and Technology, Taiwan
- MOST 107-2811-B-002 -008 Ministry of Science and Technology, Taiwan
- MOST 108-2320-B-002-029-MY3 Ministry of Science and Technology, Taiwan
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Affiliation(s)
- Ming Tatt Lee
- Department of Pharmacology, College of Medicine, National Taiwan University, Taipei 10051, Taiwan
- Faculty of Pharmaceutical Sciences, UCSI University, Kuala Lumpur 56000, Malaysia
| | - Ken Mackie
- Gill Center for Biomolecular Research, Indiana University, Bloomington, Indiana 47405, USA
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana 47405, USA
| | - Lih-Chu Chiou
- Department of Pharmacology, College of Medicine, National Taiwan University, Taipei 10051, Taiwan
- Graduate Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei 10051, Taiwan
- Graduate Institute of Acupuncture Science, China Medical University, Taichung 40402, Taiwan
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Lei X, Yan Y, Zeng J, Wang R, Li S, Xiao Z, Liu X. Activation of HCN channels caused by elevated cAMP levels in periaqueductal gray promotes bone cancer pain. Neurochem Int 2023; 162:105437. [PMID: 36336089 DOI: 10.1016/j.neuint.2022.105437] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2022] [Revised: 10/06/2022] [Accepted: 10/20/2022] [Indexed: 11/06/2022]
Abstract
The periaqueductal gray (PAG) is an important relay center for the descending pathways that regulate nociceptive information transduction. Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels play critical roles in the nerve injury-induced pain hypersensitivity. Previous studies have identified that HCN1 and HCN2 channel protein located in the ventral-lateral periaqueductal gray (vlPAG), a region important for pain regulation. However, it is not clear whether the HCN channel in vlPAG is involved in bone cancer pain (BCP). In this study, we assessed the role of HCN channels in BCP by measuring changes of HCN channel expression and activity in vlPAG neurons in bone cancer rats. In the present study, the BCP model was established by injecting SHZ-88 breast cancer cells into the right tibia bone marrow in rats. The mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) were measured to evaluate pain behavior in rats. HCN1 and HCN2 channels expression in vlPAG were detected by using Western Blot and immunohistochemistry. In addition, the cAMP level in vlPAG neurons was detected by ELISA, and HCN channel current (Ih) of vlPAG neurons was recorded by whole cell patch-clamp to evaluate HCN channel activity. As a result, decreased MWT and TWL were observed in rats on 7d after SHZ-88 cell inoculation, and the allodynia was sustained until 21d after inoculation. At the same time, HCN1 and HCN2 channels expression and neuronal Ih in vlPAG were significantly increased in BCP rats. In addition, the level of cAMP in vlPAG also increased after SHZ-88 cell inoculation. Furthermore, intravlPAG injection of ZD7288 (HCN channels antagonist) could significantly reduce hyperalgesia and the elevation of cAMP in vlPAG in BCP rats. Our observations suggest that the elevation of cAMP may promote the activation of HCN channels in vlPAG in bone cancer rats, thereby promoting the development of bone cancer pain.
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Affiliation(s)
- Xiaolu Lei
- Key Laboratory of Brain Science, Zunyi Medical University, Zunyi, 563000, China; Guizhou Key Laboratory of Anaesthesia and Organ Protection, Zunyi Medical University, Zunyi, 563000, China
| | - Yan Yan
- Key Laboratory of Brain Science, Zunyi Medical University, Zunyi, 563000, China; Guizhou Key Laboratory of Anaesthesia and Organ Protection, Zunyi Medical University, Zunyi, 563000, China
| | - Junwei Zeng
- Department of Physiology, Zunyi Medical University, Zunyi, 563000, China
| | - Rong Wang
- Department of Physiology, Zunyi Medical University, Zunyi, 563000, China
| | - Song Li
- Department of Physiology, Zunyi Medical University, Zunyi, 563000, China
| | - Zhi Xiao
- Key Laboratory of Brain Science, Zunyi Medical University, Zunyi, 563000, China; Guizhou Key Laboratory of Anaesthesia and Organ Protection, Zunyi Medical University, Zunyi, 563000, China
| | - Xiaohong Liu
- Department of Physiology, Zunyi Medical University, Zunyi, 563000, China.
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9
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Shah J, Fermo O. Review of systemic and syndromic complications of cannabis use: A review. Medicine (Baltimore) 2022; 101:e32111. [PMID: 36626471 PMCID: PMC9750691 DOI: 10.1097/md.0000000000032111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
PURPOSE OF REVIEW Prescribed and non-prescribed cannabis use is common. Providers in specialties treating chronic pain - primary care, pain management, and neurology-will be coming across medical cannabis as a treatment for chronic pain, regardless of whether they are prescribers. It is important to be aware of the systemic and syndromic complications of acute and chronic cannabis use in the differential diagnosis of cardiac, cardiovascular, cerebrovascular, gastrointestinal, and psychiatric disorders. RECENT FINDINGS Medical cannabis is legal in 36 states. Studies have shown several potentially serious adverse effects associated with cannabis use. SUMMARY Cannabis use has the potential to cause several complications that can be easily overlooked without a preexisting high index of suspicion.
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Affiliation(s)
- Jay Shah
- University of Queensland/Ochsner Clinical School, Brisbane, QLD, Australia
| | - Olga Fermo
- Department of Neurology, Mayo Clinic Florida, Jacksonville, FL, USA
- * Correspondence: Olga Fermo, Department of Neurology, Mayo Clinic Florida, 4500 San Pablo Rd., Jacksonville, FL, USA (e-mail: )
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10
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Woyach V, Sherman K, Hillard CJ, Hopp FA, Hogan QH, Dean C. Fatty acid amide hydrolase activity in the dorsal periaqueductal gray attenuates neuropathic pain and associated dysautonomia. Am J Physiol Regul Integr Comp Physiol 2022; 323:R749-R762. [PMID: 36154489 PMCID: PMC9639763 DOI: 10.1152/ajpregu.00073.2022] [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: 04/08/2022] [Revised: 08/29/2022] [Accepted: 09/22/2022] [Indexed: 01/11/2023]
Abstract
The complexity of neuropathic pain and its associated comorbidities, including dysautonomia, make it difficult to treat. Overlap of anatomical regions and pharmacology of sympathosensory systems in the central nervous system (CNS) provide targets for novel treatment strategies. The dorsal periaqueductal gray (dPAG) is an integral component of both the descending pain modulation system and the acute stress response and is critically involved in both analgesia and the regulation of sympathetic activity. Local manipulation of the endocannabinoid signaling system holds great promise to provide analgesia without excessive adverse effects and also influence autonomic output. Inhibition of fatty acid amide hydrolase (FAAH) increases brain concentrations of the endocannabinoid N-arachidonoylethanolamine (AEA) and reduces pain-related behaviors in neuropathic pain models. Neuropathic hyperalgesia and reduced sympathetic tone are associated with increased FAAH activity in the dPAG, which suggests the hypothesis that inhibition of FAAH in the dPAG will normalize pain sensation and autonomic function in neuropathic pain. To test this hypothesis, the effects of systemic or intra-dPAG FAAH inhibition on hyperalgesia and dysautonomia developed after spared nerve injury (SNI) were assessed in male and female rats. Administration of the FAAH inhibitor PF-3845 into the dPAG reduces hyperalgesia behavior and the decrease in sympathetic tone induced by SNI. Prior administration of the CB1 receptor antagonist AM281, attenuated the antihyperalgesic and sympathetic effects of FAAH inhibition. No sex differences were identified. These data support an integrative role for AEA/CB1 receptor signaling in the dPAG contributing to the regulation of both hyperalgesia behavior and altered sympathetic tone in neuropathic pain.
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Affiliation(s)
- Victoria Woyach
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, Wisconsin
- Research Service, Zablocki Veterans Affairs Medical Center, Milwaukee Wisconsin
| | - Katherine Sherman
- Research Service, Zablocki Veterans Affairs Medical Center, Milwaukee Wisconsin
| | - Cecilia J Hillard
- Department of Pharmacology and Toxicology and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Francis A Hopp
- Research Service, Zablocki Veterans Affairs Medical Center, Milwaukee Wisconsin
| | - Quinn H Hogan
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, Wisconsin
- Research Service, Zablocki Veterans Affairs Medical Center, Milwaukee Wisconsin
| | - Caron Dean
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, Wisconsin
- Research Service, Zablocki Veterans Affairs Medical Center, Milwaukee Wisconsin
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11
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Wiese BM, Liktor-Busa E, Couture SA, Nikas SP, Ji L, Liu Y, Makriyannis A, Spigelman I, Vanderah TW, Largent-Milnes TM. Brain Penetrant, but not Peripherally Restricted, Synthetic Cannabinoid 1 Receptor Agonists Promote Morphine-Mediated Respiratory Depression. Cannabis Cannabinoid Res 2022; 7:621-627. [PMID: 34935460 PMCID: PMC9587769 DOI: 10.1089/can.2021.0090] [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] [Indexed: 11/12/2022] Open
Abstract
Introduction: Cannabis acceptance and use continues to rise despite the gaps in knowledge regarding the mechanisms of cannabinoids and the endocannabinoid system in many physiological functions, including respiratory influence. Methods: With recent evidence of cannabinoid receptor 1 (CB1R) presence in the collection of respiratory neurons in the brainstem, as well as in the peripheral lung tissue, it is vital that the mechanisms involved in central and peripheral CB1R modulation of respiratory function be delineated. In this study we sought to define the roles of central versus peripheral CB1R activation on respiratory depression alone and in combination with morphine using whole body plethysmography. Results: We show that the peripherally restricted CB1 agonist (4-{2-[-(1E)-1[(4-propylnaphthalen-1-yl)methylidene]-1H-inden-3yl]ethyl}morpholine [PrNMI] 0.3, 0.6, and 1 mg/kg) does not induce respiratory depression, while our previous studies showed that a central penetrating synthetic cannabinoid does induce respiratory depression. Significantly, the combination of morphine with the peripheral CB1 agonist, PrNMI, attenuated morphine-induced respiratory depression. Conclusions: These studies support that a peripherally restricted CB1R agonist may be a unique strategy to attenuate the respiratory depression associated with opioid therapy.
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Affiliation(s)
- Beth M. Wiese
- Department of Pharmacology, University of Arizona, Tucson, Arizona, USA
| | - Erika Liktor-Busa
- Department of Pharmacology, University of Arizona, Tucson, Arizona, USA
| | - Sarah A. Couture
- Department of Pharmacology, University of Arizona, Tucson, Arizona, USA
| | - Spyros P. Nikas
- Chemistry and Chemical Biology, Bouve College Health Sciences—Center for Drug Discovery, Northeastern University, Boston, Massachusetts, USA
| | - Lipin Ji
- Chemistry and Chemical Biology, Bouve College Health Sciences—Center for Drug Discovery, Northeastern University, Boston, Massachusetts, USA
| | - Yingpeng Liu
- Chemistry and Chemical Biology, Bouve College Health Sciences—Center for Drug Discovery, Northeastern University, Boston, Massachusetts, USA
| | - Alexandros Makriyannis
- Chemistry and Chemical Biology, Bouve College Health Sciences—Center for Drug Discovery, Northeastern University, Boston, Massachusetts, USA
| | - Igor Spigelman
- Division of Oral Biology and Medicine, School of Dentistry, University of California, Los Angeles, California, USA
| | - Todd W. Vanderah
- Department of Pharmacology, University of Arizona, Tucson, Arizona, USA
- Comprehensive Pain and Addiction Center, University of Arizona, Health Sciences, Tucson, Arizona, USA
| | - Tally M. Largent-Milnes
- Department of Pharmacology, University of Arizona, Tucson, Arizona, USA
- Comprehensive Pain and Addiction Center, University of Arizona, Health Sciences, Tucson, Arizona, USA
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12
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Takemura Y, Sudo Y, Saeki T, Kurata S, Suzuki T, Mori T, Uezono Y. Involvement of spinal G-protein inwardly rectifying potassium (GIRK) channels in the enhanced antinociceptive effects of the activation of both μ-opioid and cannabinoid CB1 receptors. J Pharmacol Sci 2022; 149:85-92. [DOI: 10.1016/j.jphs.2022.04.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Revised: 03/30/2022] [Accepted: 04/08/2022] [Indexed: 11/17/2022] Open
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13
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Ram A, Edwards T, McCarty A, Afrose L, McDermott MV, Bobeck EN. GPR171 Agonist Reduces Chronic Neuropathic and Inflammatory Pain in Male, But Not Female Mice. FRONTIERS IN PAIN RESEARCH (LAUSANNE, SWITZERLAND) 2022; 2:695396. [PMID: 35295419 PMCID: PMC8915562 DOI: 10.3389/fpain.2021.695396] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 08/17/2021] [Indexed: 12/22/2022]
Abstract
Chronic pain is a growing public health crisis that requires exigent and efficacious therapeutics. GPR171 is a promising therapeutic target that is widely expressed through the brain, including within the descending pain modulatory regions. Here, we explore the therapeutic potential of the GPR171 agonist, MS15203, in its ability to alleviate chronic pain in male and female mice using a once-daily systemic dose (10 mg/kg, i.p.) of MS15203 over the course of 5 days. We found that in our models of Complete Freund's Adjuvant (CFA)-induced inflammatory pain and chemotherapy-induced peripheral neuropathy (CIPN), MS15203 did not alleviate thermal hypersensitivity and allodynia, respectively, in female mice. On the other hand, MS15203 treatment decreased the duration of thermal hypersensitivity in CFA-treated male mice following 3 days of once-daily administration. MS15203 treatment also produced an improvement in allodynia in male mice, but not female mice, in neuropathic pain after 5 days of treatment. Gene expression of GPR171 and that of its endogenous ligand BigLEN, encoded by the gene PCSK1N, were unaltered within the periaqueductal gray (PAG) in both male and female mice following inflammatory and neuropathic pain. However, following neuropathic pain in male mice, the protein levels of GPR171 were decreased in the PAG. Treatment with MS15203 then rescued the protein levels of GPR171 in the PAG of these mice. Taken together, our results identify GPR171 as a GPCR that displays sexual dimorphism in alleviation of chronic pain. Further, our results suggest that GPR171 and MS15203 have demonstrable therapeutic potential in the treatment of chronic pain.
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Affiliation(s)
- Akila Ram
- Department of Biology, Utah State University, Logan, UT, United States
| | - Taylor Edwards
- Department of Biology, Utah State University, Logan, UT, United States
| | - Ashley McCarty
- Department of Biology, Utah State University, Logan, UT, United States
| | - Leela Afrose
- Department of Biology, Utah State University, Logan, UT, United States
| | - Max V McDermott
- Department of Biology, Utah State University, Logan, UT, United States.,Interdisciplinary Neuroscience Program, Utah State University, Logan, UT, United States
| | - Erin N Bobeck
- Department of Biology, Utah State University, Logan, UT, United States.,Interdisciplinary Neuroscience Program, Utah State University, Logan, UT, United States
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14
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Brainstem Mechanisms of Pain Modulation: A within-Subjects 7T fMRI Study of Placebo Analgesic and Nocebo Hyperalgesic Responses. J Neurosci 2021; 41:9794-9806. [PMID: 34697093 DOI: 10.1523/jneurosci.0806-21.2021] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 09/23/2021] [Accepted: 09/28/2021] [Indexed: 11/21/2022] Open
Abstract
Pain perception can be powerfully influenced by an individual's expectations and beliefs. Although the cortical circuitry responsible for pain modulation has been thoroughly investigated, the brainstem pathways involved in the modulatory phenomena of placebo analgesia and nocebo hyperalgesia remain to be directly addressed. This study used ultra-high-field 7 tesla functional MRI (fMRI) to accurately resolve differences in brainstem circuitry present during the generation of placebo analgesia and nocebo hyperalgesia in healthy human participants (N = 25, 12 male). Over 2 successive days, through blinded application of altered thermal stimuli, participants were deceptively conditioned to believe that two inert creams labeled lidocaine (placebo) and capsaicin (nocebo) were acting to modulate their pain relative to a third Vaseline (control) cream. In a subsequent test phase, fMRI image sets were collected while participants were given identical noxious stimuli to all three cream sites. Pain intensity ratings were collected and placebo and nocebo responses determined. Brainstem-specific fMRI analysis revealed altered activity in key pain modulatory nuclei, including a disparate recruitment of the periaqueductal gray (PAG)-rostral ventromedial medulla (RVM) pathway when both greater placebo and nocebo effects were observed. Additionally, we found that placebo and nocebo responses differentially activated the parabrachial nucleus but overlapped in engagement of the substantia nigra and locus coeruleus. These data reveal that placebo and nocebo effects are generated through differential engagement of the PAG-RVM pathway, which in concert with other brainstem sites likely influences the experience of pain by modulating activity at the level of the dorsal horn.SIGNIFICANCE STATEMENT Understanding endogenous pain modulatory mechanisms would support development of effective clinical treatment strategies for both acute and chronic pain. Specific brainstem nuclei have long been known to play a central role in nociceptive modulation; however, because of the small size and complex organization of the nuclei, previous neuroimaging efforts have been limited in directly identifying how these subcortical networks interact during the development of antinociceptive and pro-nociceptive effects. We used ultra-high-field fMRI to resolve brainstem structures and measure signal change during placebo analgesia and nocebo hyperalgesia. We define overlapping and disparate brainstem circuitry responsible for altering pain perception. These findings extend our understanding of the detailed organization and function of discrete brainstem nuclei involved in pain processing and modulation.
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15
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Iman IN, Ahmad NAZ, Mohd Yusof NA, Talib UN, Norazit A, Kumar J, Mehat MZ, Hassan Z, Müller CP, Muzaimi M. Mitragynine (Kratom)-Induced Cognitive Impairments in Mice Resemble Δ9-THC and Morphine Effects: Reversal by Cannabinoid CB 1 Receptor Antagonism. Front Pharmacol 2021; 12:708055. [PMID: 34603022 PMCID: PMC8481666 DOI: 10.3389/fphar.2021.708055] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Accepted: 08/16/2021] [Indexed: 11/29/2022] Open
Abstract
Kratom is a widely abused plant-based drug preparation with a global interest in recent years, well beyond its native grounds in Southeast Asia. Mitragynine, its major psychoactive constituent is known to exhibit opioid-like behavioral effects with resultant neuroplasticity in the brain reward system. Its chronic administration is associated with cognitive impairments in animal studies. However, the underlying molecular mechanism for such a deficit remains elusive. In this study, the involvement of cannabinoid type-1 (CB1) receptors in cognitive deficits after chronic mitragynine exposures was investigated for 28 days (with incremental dose sensitization from 1 to 25 mg/kg) in adult male Swiss albino mice using the IntelliCage® system. Chronic high-dose mitragynine exposure (5–25 mg/kg, intraperitoneal [i.p.]), but not low-dose exposure (1–4 mg/kg, i.p.), induced hyperlocomotion, potentiated the preference for sucrose reward, increased resistance to punishment, and impaired place learning and its reversal. Comparable deficits were also observed after chronic treatments with Δ-9-tetrahydrocannabinol (THC, 2 mg/kg, i.p.) or morphine (5 mg/kg, subcutaneous). Mitragynine-, morphine-, and THC-induced learning and memory deficits were reversed by co-treatment with the CB1 receptor antagonist, NIDA-41020 (10 mg/kg, i.p.). A significant upregulation of CB1 receptor expression was found in the hippocampal CA1 region and ventral tegmental area after chronic high-dose mitragynine and morphine, whereas a downregulation was observed after chronic THC. In conclusion, the present study suggests a plausible role of the CB1 receptor in mediating the dose-dependent cognitive deficits after chronic high-dose mitragynine exposure. This also highlights the potential of CB1 receptor antagonism in ameliorating the cognitive deficits associated with long-term kratom/mitragynine consumption in humans.
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Affiliation(s)
- Ismail Nurul Iman
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Health Campus, Kota Bharu, Malaysia
| | - Nur Aimi Zawami Ahmad
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Health Campus, Kota Bharu, Malaysia
| | - Nurul Aiman Mohd Yusof
- Department of Anatomy, School of Medical Sciences, Universiti Sains Malaysia, Health Campus, Kota Bharu, Malaysia
| | - Ummi Nasrah Talib
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Health Campus, Kota Bharu, Malaysia
| | - Anwar Norazit
- Department of Biomedical Science, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Jaya Kumar
- Department of Physiology, Universiti Kebangsaan Malaysia Medical Centre, Kuala Lumpur, Malaysia
| | - Muhammad Zulfadli Mehat
- Department of Human Anatomy, Faculty of Medicine and Health Science, Universiti Putra Malaysia, Serdang, Malaysia
| | - Zurina Hassan
- Centre for Drug Research, Universiti Sains Malaysia, Minden, Malaysia
| | - Christian P Müller
- Centre for Drug Research, Universiti Sains Malaysia, Minden, Malaysia.,Section of Addiction Medicine, Department of Psychiatry and Psychotherapy, University Clinic, Friedrich-Alexander-University of Erlangen-Nuremberg, Erlangen, Germany
| | - Mustapha Muzaimi
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Health Campus, Kota Bharu, Malaysia
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16
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Effects of inflammatory pain on CB1 receptor in the midbrain periaqueductal gray. Pain Rep 2021; 6:e897. [PMID: 33693301 PMCID: PMC7939232 DOI: 10.1097/pr9.0000000000000897] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 12/10/2020] [Accepted: 12/25/2020] [Indexed: 11/26/2022] Open
Abstract
Western blot and GTPγS analyses reveal inflammatory pain–induced adaptations in the midbrain periaqueductal gray, which is critically involved in descending pain modulation. Pain upregulates the expression of the CB1 receptor and increases G-protein coupling in the periaqueductal gray. Introduction: The periaqueductal gray (PAG) mediates the antinociceptive properties of analgesics, including opioids and cannabinoids. Administration of either opioids or cannabinoids into the PAG induces antinociception. However, most studies characterizing the antinociceptive properties of cannabinoids in the PAG have been conducted in naive animals. Few studies have reported on the role of CB1 receptors in the PAG during conditions which would prompt the administration of analgesics, namely, during pain states. Objectives: To examine inflammatory pain-induced changes in CB1 receptor expression and function in the midbrain periaqueductal gray. Methods: In this study, we used the Complete Freund Adjuvant model to characterize CB1 receptor expression and G-protein coupling during persistent inflammatory pain. Results: Inflammatory pain induced an upregulation in the expression of synaptic CB1 receptors in the PAG. Despite this pain-induced change in CB1 expression, there was no corresponding upregulation of CB1 mRNA after the induction of inflammatory pain, suggesting a pain-induced recruitment of CB1 receptors to the synaptic sites within PAG neurons or increased coupling efficiency between the receptor and effector systems. Inflammatory pain also enhanced ventrolateral PAG CB1 receptor activity, as there was an increase in CP55,940-stimulated G-protein activation compared with pain-naïve control animals. Conclusion: These findings complement a growing body of evidence which demonstrate pain-induced changes in brain regions that are responsible for both the analgesic and rewarding properties of analgesic pharmacotherapies. Because much of our understanding of the pharmacology of cannabinoids is based on studies which use largely pain-naïve male animals, this work fills in important gaps in the knowledge base by incorporating pain-induced adaptations and cannabinoid pharmacology in females.
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17
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Mohammadkhani A, Borgland SL. Cellular and behavioral basis of cannabinioid and opioid interactions: Implications for opioid dependence and withdrawal. J Neurosci Res 2020; 100:278-296. [PMID: 33352618 DOI: 10.1002/jnr.24770] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Accepted: 11/25/2020] [Indexed: 01/22/2023]
Abstract
The brain's endogenous opioid and endocannabinoid systems are neuromodulatory of synaptic transmission, and play key roles in pain, memory, reward, and addiction. Recent clinical and pre-clinical evidence suggests that opioid use may be reduced with cannabinoid intake. This suggests the presence of a functional interaction between these two systems. Emerging research indicates that cannabinoids and opioids can functionally interact at different levels. At the cellular level, opioid and cannabinoids can have direct receptor associations, alterations in endogenous opioid peptide or cannabinoid release, or post-receptor activation interactions via shared signal transduction pathways. At the systems level, the nature of cannabinoid and opioid interaction might differ in brain circuits underlying different behavioral phenomenon, including reward-seeking or antinociception. Given the rising use of opioid and cannabinoid drugs, a better understanding of how these endogenous signaling systems interact in the brain is of significant interest. This review focuses on the potential relationship of these neural systems in addiction-related processes.
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Affiliation(s)
- Aida Mohammadkhani
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, The University of Calgary, Calgary, AB, Canada
| | - Stephanie L Borgland
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, The University of Calgary, Calgary, AB, Canada
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18
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Positive allosteric modulation of the cannabinoid type-1 receptor (CB1R) in periaqueductal gray (PAG) antagonizes anti-nociceptive and cellular effects of a mu-opioid receptor agonist in morphine-withdrawn rats. Psychopharmacology (Berl) 2020; 237:3729-3739. [PMID: 32857187 PMCID: PMC7687722 DOI: 10.1007/s00213-020-05650-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Accepted: 08/20/2020] [Indexed: 12/24/2022]
Abstract
Opioid drugs are a first-line treatment for severe acute pain and other chronic pain conditions, but long-term opioid drug use produces opioid-induced hyperalgesia (OIH). Co-administration of cannabinoids with opioid receptor agonists produce anti-nociceptive synergy, but cannabinoid receptor agonists may also produce undesirable side effects. Therefore, positive allosteric modulators (PAM) of cannabinoid type-1 receptors (CB1R) may provide an option reducing pain and/or enhancing the anti-hyperalgesic effects of opioids without the side effects, tolerance, and dependence observed with the use of ligands that target the orthosteric binding sites. This study tested GAT211, a PAM of cannabinoid type-1 receptors (CB1R), for its ability to enhance the anti-hyperalgesic effects of the mu-opioid receptor (MOR) agonist DAMGO in rats treated chronically with morphine (or saline) and tested during withdrawal. We tested the effects of intra-periaqueductal gray (PAG) injections of (1) DAMGO, (2) GAT211, or (3) DAMGO + GAT211 on thermal nociception in chronic morphine-treated rats that were hyperalgesic and also in saline-treated control rats. We used slice electrophysiology to test the effects of DAMGO/GAT211 bath application on synaptic transmission in the vlPAG. Intra-PAG DAMGO infusions dose-dependently reversed chronic morphine-induced hyperalgesia, but intra-PAG GAT211 did not alter nociception at the doses we tested. When co-administered into the PAG, GAT211 antagonized the anti-nociceptive effects of DAMGO in morphine-withdrawn rats. DAMGO suppressed synaptic inhibition in the vlPAG of brain slices taken from saline- and morphine-treated rats, and GAT211 attenuated DAMGO-induced suppression of synaptic inhibition in vlPAG neurons via actions at CB1R. These findings show that positive allosteric modulation of CB1R antagonizes the behavioral and cellular effects of a MOR agonist in the PAG of rats.
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19
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Lee MT, Chen YH, Mackie K, Chiou LC. Median Nerve Stimulation as a Nonpharmacological Approach to Bypass Analgesic Tolerance to Morphine: A Proof-of-Concept Study in Mice. THE JOURNAL OF PAIN 2020; 22:300-312. [PMID: 33069869 DOI: 10.1016/j.jpain.2020.09.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 09/23/2020] [Accepted: 09/25/2020] [Indexed: 02/06/2023]
Abstract
Analgesic tolerance to opioids contributes to the opioid crisis by increasing the quantity of opioids prescribed and consumed. Thus, there is a need to develop non-opioid-based pain-relieving regimens as well as strategies to circumvent opioid tolerance. Previously, we revealed a non-opioid analgesic mechanism induced by median nerve electrostimulation at the overlaying PC6 (Neiguan) acupoint (MNS-PC6). Here, we further examined the efficacy of MNS-PC6 in morphine-tolerant mice with neuropathic pain induced by chronic constriction injury (CCI) of the sciatic nerve. Daily treatments of MNS-PC6 (2 Hz, 2 mA), but not electrostimulation at a nonmedian nerve-innervated location, for a week post-CCI induction significantly suppressed established mechanical allodynia in CCI-mice in an orexin-1 (OX1) and cannabinoid-1 (CB1) receptor-dependent fashion. This antiallodynic effect induced by repeated MNS-PC6 was comparable to that induced by repeated gabapentin (50 mg/kg, i.p.) or single morphine (10 mg/kg, i.p.) treatments, but without tolerance, unlike repeated morphine-induced analgesia. Furthermore, single and repeated MNS-PC6 treatments remained fully effective in morphine-tolerant CCI-mice, also in an OX1 and CB1 receptor-dependent fashion. In CCI-mice receiving escalating doses of morphine for 21 days (10, 20 and 50 mg/kg), single and repeated MNS-PC6 treatments remained fully effective. Therefore, repeated MNS-PC6 treatments induce analgesia without tolerance, and retain efficacy in opioid-tolerant mice via a mechanism that involves OX1 and CB1 receptors. This study suggests that MNS-PC6 is an alternative pain management strategy that maybe useful for combatting the opioid epidemic, and opioid-tolerant patients receiving palliative care. PERSPECTIVE: Median nerve stimulation relieves neuropathic pain in mice without tolerance and retains efficacy even in mice with analgesic tolerance to escalating doses of morphine, via an opioid-independent, orexin-endocannabinoid-mediated mechanism. This study provides a proof of concept for utilizing peripheral nerve stimulating devices for pain management in opioid-tolerant patients.
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Affiliation(s)
- Ming Tatt Lee
- Graduate Institute of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan; Graduate Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan; Faculty of Pharmaceutical Sciences, UCSI University, Kuala Lumpur, Malaysia
| | - Yi-Hung Chen
- Graduate Institute of Acupuncture Science, China Medical University, Taichung, Taiwan; Chinese Medicine Research Center, China Medical University, Taichung, Taiwan
| | - Ken Mackie
- Gill Center for Biomolecular Research, Indiana University, Bloomington, Indiana; Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana
| | - Lih-Chu Chiou
- Graduate Institute of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan; Graduate Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan; Graduate Institute of Acupuncture Science, China Medical University, Taichung, Taiwan.
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20
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Quiñonez‐Bastidas GN, Palomino‐Hernández O, López‐Ortíz M, Rocha‐González HI, González‐Anduaga GM, Regla I, Navarrete A. Antiallodynic effect of PhAR-DBH-Me involves cannabinoid and TRPV1 receptors. Pharmacol Res Perspect 2020; 8:e00663. [PMID: 32965798 PMCID: PMC7510332 DOI: 10.1002/prp2.663] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Revised: 08/20/2020] [Accepted: 08/21/2020] [Indexed: 12/29/2022] Open
Abstract
The antiallodynic effect of PhAR-DBH-Me was evaluated on two models of neuropathic pain, and the potential roles of CB1, CB2, and TRPV1 receptors as molecular targets of PhAR-DBH-Me were studied. Female Wistar rats were submitted to L5/L6 spinal nerve ligation (SNL) or repeated doses of cisplatin (0.1 mg/kg, i.p.) to induce experimental neuropathy. Then, tactile allodynia was determined, and animals were treated with logarithmic doses of PhAR-DBH-Me (3.2-100 mg/kg, i.p.). To evaluate the mechanism of action of PhAR-DBH-Me, in silico studies using crystallized structures of CB1, CB2, and TRPV1 receptors were performed. To corroborate the computational insights, animals were intraperitoneally administrated with antagonists for CB1 (AM-251, 3 mg/kg), CB2 (AM-630, 1 mg/kg), and TRPV1 receptors (capsazepine, 3 mg/kg), 15 min before to PhAR-DBH-Me (100 mg/kg) administration. Vagal stimulation evoked on striated muscle contraction in esophagus, was used to elicited pharmacological response of PhAR-DBH-ME on nervous tissue. Systemic administration of PhAR-DBH-Me reduced the SNL- and cisplatin-induced allodynia. Docking studies suggested that PhAR-DBH-Me acts as an agonist for CB1, CB2, and TRPV1 receptors, with similar affinity to the endogenous ligand anandamide. Moreover antiallodynic effect of PhAR-DBH-Me was partially prevented by administration of AM-251 and AM-630, and completely prevented by capsazepine. Finally, PhAR-DBH-Me decreased the vagally evoked electrical response in esophagus rat. Taken together, results indicate that PhAR-DBH-Me induces an antiallodynic effect through partial activation of CB1 and CB2 receptors, as well as desensitization of TRPV1 receptors. Data also shed light on the novel vanilloid nature of the synthetic compound PhAR-DBH-Me.
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Affiliation(s)
| | - Oscar Palomino‐Hernández
- Computational Biomedicine ‐ Institute for Advanced Simulation (IAS‐5) and Institute of Neuroscience and Medicine (INM‐9)Forschungszentrum JülichJülichGermany
- Department of ChemistryRheinisch‐Westfälische Technische Hochschule AachenAachenGermany
| | - Manuel López‐Ortíz
- Facultad de Estudios Superiores ZaragozaUniversidad Nacional Autónoma de México (UNAM)MéxicoDFMéxico
| | - Héctor Isaac Rocha‐González
- Sección de Estudios de Posgrado e InvestigaciónEscuela Superior de MedicinaInstituto Politécnico NacionalMéxicoCiudad de MéxicoMéxico
| | - Gloria Melisa González‐Anduaga
- Facultad de QuímicaDepartamento de FarmaciaUniversidad Nacional Autónoma de MéxicoCiudad UniversitariaCoyoacánCiudad de MéxicoMéxico
| | - Ignacio Regla
- Facultad de Estudios Superiores ZaragozaUniversidad Nacional Autónoma de México (UNAM)MéxicoDFMéxico
| | - Andrés Navarrete
- Facultad de QuímicaDepartamento de FarmaciaUniversidad Nacional Autónoma de MéxicoCiudad UniversitariaCoyoacánCiudad de MéxicoMéxico
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21
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Shahsavari F, Abbasnejad M, Raoof M, Esmaeili-Mahani S. The rostral ventromedial medulla orexin 1 receptors and extracellular signal-regulated kinase in hippocampus are involved in modulation of anxiety behavior induced by dental pulp nociception in adult male rats. Arch Oral Biol 2020; 116:104778. [PMID: 32474210 DOI: 10.1016/j.archoralbio.2020.104778] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 05/21/2020] [Accepted: 05/21/2020] [Indexed: 11/16/2022]
Abstract
OBJECTIVES To explore the role of rostral ventromedial medulla (RVM) orexin 1 receptors (OX1R) on orofacial nociception -induced anxiety and locomotion in rats. DESIGN Forty two adult male Wistar rats (220-270 gr) were randomly divided into 7 groups (n = 6) as follows: untreated control, capsaicin, capsaicin vehicle-treated group (sham operation), capsaicin groups pretreated by intra-RVM administration orexin 1 receptor (OX1R) agonist (orexin A) or antagonist (SB-334867) and the capsaicin groups treated by drugs vehicles (DMSO or aCSF). Orofacial nociception was induced by intradental application of capsaicin (100 μg) into the incisors of rats. Anxiety level and locomotor activity were measured by the elevated plus maze (EPM) and open field (OF) tests, respectively. Hippocampal levels of phosphorylated extracellular signal regulated Kinase (p-ERK) was also assessed by western blotting. RESULTS Intradental application of capsaicin significantly increased anxiety and decreased locomotion behaviors. Intra-RVM microinjection of orexin-A significantly prevented capsaicin-induced anxiety-like behavior and increased locomotor activity in the EPM and OF tests. These effects were inhibited by SB-334867. Furthermore, orexin-A significantly increased p-ERK levels in capsaicin-treated rats. This effect was inhibited by pretreatment of the rats with SB-334867. CONCLUSIONS The results suggest that both OX1R signaling in the RVM and hippocampal p-ERK signaling are involved in orofacial nociception-induced anxiety as well as locomotor activity.
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Affiliation(s)
- Fatemeh Shahsavari
- Department of Biology, Faculty of Sciences, Shahid Bahonar University, Kerman, Iran
| | - Mehdi Abbasnejad
- Department of Biology, Faculty of Sciences, Shahid Bahonar University, Kerman, Iran.
| | - Maryam Raoof
- Neuroscience Research Center, Kerman University of Medical Sciences, Kerman, Iran; Department of Orofacial Pain and Dysfunction, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Saeed Esmaeili-Mahani
- Department of Biology, Faculty of Sciences, Shahid Bahonar University, Kerman, Iran; Neuroscience Research Center, Kerman University of Medical Sciences, Kerman, Iran
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Godoi MM, Junior HZ, da Cunha JM, Zanoveli JM. Mu-opioid and CB1 cannabinoid receptors of the dorsal periaqueductal gray interplay in the regulation of fear response, but not antinociception. Pharmacol Biochem Behav 2020; 194:172938. [PMID: 32376258 DOI: 10.1016/j.pbb.2020.172938] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 04/27/2020] [Accepted: 04/28/2020] [Indexed: 12/21/2022]
Abstract
Evidence indicates that periaqueductal gray matter (PAG) plays an important role in defensive responses and pain control. The activation of cannabinoid type-1 (CB1) or mu-opioid (MOR) receptors in the dorsal region of this structure (dPAG) inhibits fear and facilitates antinociception induced by different aversive stimuli. However, it is still unknown whether these two receptors work cooperatively in order to achieve these inhibitory actions. This study investigated the involvement and a likely interplay between CB1 and MOR receptors localized into the dPAG on the regulation of fear-like defensive responses and antinociception (evaluated in tail-flick test) evoked by dPAG chemical stimulation with N-methyl-d-aspartate (NMDA). Before the administration of NMDA, animals were first intra-dPAG injected with the CB1 agonist ACEA (0.5 pmol), or with the MOR agonist DAMGO (0.5 pmol) in combination with the respective antagonists AM251 (CB1 antagonist, 100 pmol) or CTOP (MOR antagonist, 1 nmol). To investigate the interplay between these receptors, microinjection of CTOP was combined with ACEA, or microinjection of AM251 was combined with DAMGO. Our results showed that both the intra-PAG treatments with ACEA or DAMGO inhibited NMDA-induced freezing expression, whereas only the treatment with DAMGO increased antinociception induced with NMDA, which are completely blocked by its respective antagonists. Interestingly, the inhibitory effects of ACEA or DAMGO on freezing was blocked by CTOP and AM251, respectively, indicating a functional interaction between these two receptors in the mediation of defensive behaviors. However, this cooperative interaction was not observed during the NMDA-induced antinociception. Our findings indicate that there is a cooperative action between the MOR and CB1 receptors within the dPAG and it is involved in the mediation of NMDA-induced defensive responses. Additionally, the MORs into the dPAG are involved in the modulation of the antinociceptive effects that follow a fear-like defense-reaction induced by dPAG chemical stimulation with NMDA.
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Affiliation(s)
- Manuella Machado Godoi
- Department of Pharmacology, Biological Sciences Building, Federal University of Paraná, Rua Coronel H. dos Santos S/N, P.O. Box 19031, Curitiba, Paraná 81540-990, Brazil
| | - Hélio Zangrossi Junior
- Department of Pharmacology, School of Medicine, University of São Paulo, Av. Bandeirantes 3900, Ribeirão Preto, São Paulo 14049-900, Brazil
| | - Joice Maria da Cunha
- Department of Pharmacology, Biological Sciences Building, Federal University of Paraná, Rua Coronel H. dos Santos S/N, P.O. Box 19031, Curitiba, Paraná 81540-990, Brazil; Institute of Neurosciences and Behavior and Laboratory of Neuropsychopharmacology of Faculty of Philosophy, Sciences and Letters of University of São Paulo, Ribeirão Preto, SP 14040-900, Brazil
| | - Janaina Menezes Zanoveli
- Department of Pharmacology, Biological Sciences Building, Federal University of Paraná, Rua Coronel H. dos Santos S/N, P.O. Box 19031, Curitiba, Paraná 81540-990, Brazil; Institute of Neurosciences and Behavior and Laboratory of Neuropsychopharmacology of Faculty of Philosophy, Sciences and Letters of University of São Paulo, Ribeirão Preto, SP 14040-900, Brazil.
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23
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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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24
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Schurman LD, Lu D, Kendall DA, Howlett AC, Lichtman AH. Molecular Mechanism and Cannabinoid Pharmacology. Handb Exp Pharmacol 2020; 258:323-353. [PMID: 32236882 PMCID: PMC8637936 DOI: 10.1007/164_2019_298] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Since antiquity, Cannabis has provoked enormous intrigue for its potential medicinal properties as well as for its unique pharmacological effects. The elucidation of its major cannabinoid constituents, Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD), led to the synthesis of new cannabinoids (termed synthetic cannabinoids) to understand the mechanisms underlying the pharmacology of Cannabis. These pharmacological tools were instrumental in the ultimate discovery of the endogenous cannabinoid system, which consists of CB1 and CB2 cannabinoid receptors and endogenously produced ligands (endocannabinoids), which bind and activate both cannabinoid receptors. CB1 receptors mediate the cannabimimetic effects of THC and are highly expressed on presynaptic neurons in the nervous system, where they modulate neurotransmitter release. In contrast, CB2 receptors are primarily expressed on immune cells. The endocannabinoids are tightly regulated by biosynthetic and hydrolytic enzymes. Accordingly, the endocannabinoid system plays a modulatory role in many physiological processes, thereby generating many promising therapeutic targets. An unintended consequence of this research was the emergence of synthetic cannabinoids sold for human consumption to circumvent federal laws banning Cannabis use. Here, we describe research that led to the discovery of the endogenous cannabinoid system and show how knowledge of this system benefitted as well as unintentionally harmed human health.
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Affiliation(s)
- Lesley D Schurman
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, USA
| | - Dai Lu
- Rangel College of Pharmacy, Health Science Center, Texas A&M University, Kingsville, TX, USA
| | - Debra A Kendall
- Department of Pharmaceutical Sciences, University of Connecticut, Storrs, CT, USA
| | - Allyn C Howlett
- Department of Physiology and Pharmacology and Center for Research on Substance Use and Addiction, Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - Aron H Lichtman
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, USA.
- Department of Medicinal Chemistry, Virginia Commonwealth University, Richmond, VA, USA.
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25
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Abstract
Given the aging Baby Boomer generation, changes in cannabis legislation, and the growing acknowledgment of cannabis for its therapeutic potential, it is predicted that cannabis use in the older population will escalate. It is, therefore, important to determine the interaction between the effects of cannabis and aging. The aim of this report is to describe the link between cannabis use and the aging brain. Our review of the literature found few and inconsistent empirical studies that directly address the impact of cannabis use on the aging brain. However, research focused on long-term cannabis use points toward cumulative effects on multimodal systems in the brain that are similarly affected during aging. Specifically, the effects of cannabis and aging converge on overlapping networks in the endocannabinoid, opioid, and dopamine systems that may affect functional decline particularly in the hippocampus and prefrontal cortex, which are critical areas for memory and executive functioning. To conclude, despite the limited current knowledge on the potential interactive effects between cannabis and aging, evidence from the literature suggests that cannabis and aging effects are concurrently present across several neurotransmitter systems. There is a great need for future research to directly test the interactions between cannabis and aging.
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Affiliation(s)
- Hye Bin Yoo
- Center for BrainHealth, School of Behavioral and Brain Sciences, University of Texas at Dallas, Dallas, Texas, USA
| | - Jennifer DiMuzio
- Center for BrainHealth, School of Behavioral and Brain Sciences, University of Texas at Dallas, Dallas, Texas, USA
| | - Francesca M Filbey
- Center for BrainHealth, School of Behavioral and Brain Sciences, University of Texas at Dallas, Dallas, Texas, USA
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26
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Tamaddonfard E, Erfanparast A, Salighedar R, Tamaddonfard S. Medial prefrontal cortex diclofenac-induced antinociception is mediated through GPR55, cannabinoid CB1, and mu-opioid receptors of this area and periaqueductal gray. Naunyn Schmiedebergs Arch Pharmacol 2019; 393:371-379. [PMID: 31641818 DOI: 10.1007/s00210-019-01735-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Accepted: 09/20/2019] [Indexed: 10/25/2022]
Abstract
Supraspinal mechanisms of non-steroidal anti-inflammatory drug (NSAID)-induced antinociception are not well understood. In the present study, the possible antinociceptive mechanisms induced by intra-medial prefrontal cortex (intra-mPFC) microinjection of diclofenac were investigated after blockade of GPR55, cannabinoid CB1, and mu-opioid receptors in this area and ventrolateral periaqueductal gray (vlPAG). For drug delivery, unilateral (left side) of mPFC and bilateral (right and left sides) of vlPAG were surgically cannulated. Formalin test was induced by subcutaneous injection of a diluted formalin solution into the right vibrissa pad. A typical biphasic (neurogenic and inflammatory phases) pain behavior was produced following formalin injection. Microinjection of diclofenac (2.5, 5, and 10 μg/0.25 μL) into the mPFC suppressed both phases of pain. Intra-mPFC microinjection of naloxonazine (a mu-opioid receptor antagonist, 1 μg/0.25 μL) and AM251 (a cannabinoid CB1 receptor antagonist, 1 μg/0.25 μL) increased both phases of pain intensity. In addition, intra-mPFC-microinjected diclofenac-induced antinociception was inhibited by prior intra-mPFC and intra-vlPAG administration of naloxonazine and AM251. On the other hand, intra-mPFC and intra-vlPAG microinjection of AM251 (0.25 μg/0.25 μL) decreased pain severity which was inhibited by prior administration of ML193. The above-mentioned drugs did not alter locomotor activity. In conclusion, diclofenac suppressed both the neurogenic and inflammatory phases of formalin-induced orofacial pain at the level of mPFC. GPR55, cannabinoid CB1, and mu-opioid receptors of the mPFC and vlPAG might be involved in the mPFC analgesic effects of diclofenac.
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Affiliation(s)
- Esmaeal Tamaddonfard
- Division of Physiology, Department of Basic Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran
| | - Amir Erfanparast
- Division of Physiology, Department of Basic Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran.
| | - Reza Salighedar
- Division of Physiology, Department of Basic Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran
| | - Sina Tamaddonfard
- Division of Physiology, Department of Basic Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran
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27
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McDermott MV, Afrose L, Gomes I, Devi LA, Bobeck EN. Opioid-Induced Signaling and Antinociception Are Modulated by the Recently Deorphanized Receptor, GPR171. J Pharmacol Exp Ther 2019; 371:56-62. [PMID: 31308196 DOI: 10.1124/jpet.119.259242] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Accepted: 07/10/2019] [Indexed: 12/13/2022] Open
Abstract
ProSAAS is one of the most widely expressed proteins throughout the brain and was recently found to be upregulated in chronic fibromyalgia patients. BigLEN is a neuropeptide that is derived from ProSAAS and was recently discovered to be the endogenous ligand for the orphan G protein-coupled receptor GPR171. Although BigLEN-GPR171 has been found to play a role in feeding and anxiety behaviors, it has not yet been explored in pain and opioid modulation. The purpose of this study was to evaluate this novel neuropeptide-receptor system in opioid-induced antinociception. We found that GPR171 is expressed in GABAergic neurons within the periaqueductal gray, which is a key brain area involved in pain modulation and opioid functions. We also found that, although the GPR171 agonist and antagonist do not have nociceptive effects on their own, they oppositely regulate morphine-induced antinociception with the agonist enhancing and antagonist reducing antinociception. Lastly, we showed that the GPR171 antagonist or receptor knockdown decreases signaling by the mu-opioid receptor, but not the delta-opioid receptor. Taken together, these results suggest that antagonism of the GPR171 receptor reduces mu opioid receptor signaling and morphine-induced antinociception, whereas the GPR171 agonist enhances morphine antinociception, suggesting that GPR171 may be a novel target toward the development of pain therapeutics. SIGNIFICANCE STATEMENT: GPR171 is a recently deorphanized receptor that is expressed within the periaqueductal gray and can regulate mu opioid receptor signaling and antinociception. This research may contribute to the development of new therapeutics to treat pain.
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Affiliation(s)
- Max V McDermott
- Department of Biology, Utah State University, Logan, Utah (M.V.M., L.A., E.N.B.) and Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, New York (I.G., L.A.D.)
| | - Leela Afrose
- Department of Biology, Utah State University, Logan, Utah (M.V.M., L.A., E.N.B.) and Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, New York (I.G., L.A.D.)
| | - Ivone Gomes
- Department of Biology, Utah State University, Logan, Utah (M.V.M., L.A., E.N.B.) and Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, New York (I.G., L.A.D.)
| | - Lakshmi A Devi
- Department of Biology, Utah State University, Logan, Utah (M.V.M., L.A., E.N.B.) and Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, New York (I.G., L.A.D.)
| | - Erin N Bobeck
- Department of Biology, Utah State University, Logan, Utah (M.V.M., L.A., E.N.B.) and Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, New York (I.G., L.A.D.)
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28
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Lesniak A, Chmielewska D, Poznanski P, Bujalska-Zadrozny M, Strzemecka J, Sacharczuk M. Divergent Response to Cannabinoid Receptor Stimulation in High and Low Stress-Induced Analgesia Mouse Lines Is Associated with Differential G-Protein Activation. Neuroscience 2019; 404:246-258. [DOI: 10.1016/j.neuroscience.2019.02.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Revised: 02/07/2019] [Accepted: 02/11/2019] [Indexed: 12/21/2022]
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29
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Berrendero F, Flores Á, Robledo P. When orexins meet cannabinoids: Bidirectional functional interactions. Biochem Pharmacol 2018; 157:43-50. [DOI: 10.1016/j.bcp.2018.08.040] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 08/23/2018] [Indexed: 01/11/2023]
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30
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Abstract
Introduction: The opioid epidemic has become an immense problem in North America, and despite decades of research on the most effective means to treat opioid use disorder (OUD), overdose deaths are at an all-time high, and relapse remains pervasive. Discussion: Although there are a number of FDA-approved opioid replacement therapies and maintenance medications to help ease the severity of opioid withdrawal symptoms and aid in relapse prevention, these medications are not risk free nor are they successful for all patients. Furthermore, there are legal and logistical bottlenecks to obtaining traditional opioid replacement therapies such as methadone or buprenorphine, and the demand for these services far outweighs the supply and access. To fill the gap between efficacious OUD treatments and the widespread prevalence of misuse, relapse, and overdose, the development of novel, alternative, or adjunct OUD treatment therapies is highly warranted. In this article, we review emerging evidence that suggests that cannabis may play a role in ameliorating the impact of OUD. Herein, we highlight knowledge gaps and discuss cannabis' potential to prevent opioid misuse (as an analgesic alternative), alleviate opioid withdrawal symptoms, and decrease the likelihood of relapse. Conclusion: The compelling nature of these data and the relative safety profile of cannabis warrant further exploration of cannabis as an adjunct or alternative treatment for OUD.
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Affiliation(s)
- Beth Wiese
- Department of Psychology, University of Missouri–St. Louis, St. Louis, Missouri
- Department of Anesthesiology, Pain Center, Washington University School of Medicine, St. Louis, Missouri
| | - Adrianne R. Wilson-Poe
- Department of Anesthesiology, Pain Center, Washington University School of Medicine, St. Louis, Missouri
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31
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Abstract
Medical cannabis (MC) is used for a variety of conditions including chronic pain. The goal of this report was to provide an in-depth qualitative exploration of patient perspectives on the strengths and limitations of MC. Members of MC dispensaries (N = 984) in New England including two-thirds with a history of chronic pain completed an online survey. In response to "How effective is medical cannabis in treating your symptoms or conditions?," with options of 0% "no relief" to 100% "complete relief," the average was 74.6% ± 0.6. The average amount spent on MC each year was $3064.47 ± 117.60, median = $2320.23, range = $52.14 to $52,140.00. Open-ended responses were coded into themes and subthemes. Analysis of answers to "What is it that you like most about MC?" (N = 2592 responses) identified 10 themes, including health benefits (36.0% of responses, eg, "Changes perception and experience of my chronic pain."), the product (14.2%, eg, "Knowing exactly what strain you are getting"), nonhealth benefits (14.1%), general considerations (10.3%), and medications (7.1%). Responses (N = 1678) to "What is it that you like least about MC?" identified 12 themes, including money (28.4%, eg, "The cost is expensive for someone on a fixed income"), effects (21.7%, eg, "The effects on my lungs"), the view of others (11.4%), access (8.2%), and method of administration (7.1%). These findings provide a patient-centered view on the advantages (eg, efficacy in pain treatment, reduced use of other medications) and disadvantages (eg, economic and stigma) of MC.
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32
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Donvito G, Nass SR, Wilkerson JL, Curry ZA, Schurman LD, Kinsey SG, Lichtman AH. The Endogenous Cannabinoid System: A Budding Source of Targets for Treating Inflammatory and Neuropathic Pain. Neuropsychopharmacology 2018; 43:52-79. [PMID: 28857069 PMCID: PMC5719110 DOI: 10.1038/npp.2017.204] [Citation(s) in RCA: 178] [Impact Index Per Article: 29.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Revised: 08/24/2017] [Accepted: 08/27/2017] [Indexed: 02/07/2023]
Abstract
A great need exists for the development of new medications to treat pain resulting from various disease states and types of injury. Given that the endogenous cannabinoid (that is, endocannabinoid) system modulates neuronal and immune cell function, both of which play key roles in pain, therapeutics targeting this system hold promise as novel analgesics. Potential therapeutic targets include the cannabinoid receptors, type 1 and 2, as well as biosynthetic and catabolic enzymes of the endocannabinoids N-arachidonoylethanolamine and 2-arachidonoylglycerol. Notably, cannabinoid receptor agonists as well as inhibitors of endocannabinoid-regulating enzymes fatty acid amide hydrolase and monoacylglycerol lipase produce reliable antinociceptive effects, and offer opioid-sparing antinociceptive effects in myriad preclinical inflammatory and neuropathic pain models. Emerging clinical studies show that 'medicinal' cannabis or cannabinoid-based medications relieve pain in human diseases such as cancer, multiple sclerosis, and fibromyalgia. However, clinical data have yet to demonstrate the analgesic efficacy of inhibitors of endocannabinoid-regulating enzymes. Likewise, the question of whether pharmacotherapies aimed at the endocannabinoid system promote opioid-sparing effects in the treatment of pain reflects an important area of research. Here we examine the preclinical and clinical evidence of various endocannabinoid system targets as potential therapeutic strategies for inflammatory and neuropathic pain conditions.
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Affiliation(s)
- Giulia Donvito
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA, USA
| | - Sara R Nass
- Department of Psychology, West Virginia University, Morgantown, WV, USA
| | - Jenny L Wilkerson
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA, USA
| | - Zachary A Curry
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA, USA
| | - Lesley D Schurman
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA, USA
| | - Steven G Kinsey
- Department of Psychology, West Virginia University, Morgantown, WV, USA
| | - Aron H Lichtman
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA, USA
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33
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Dean C, Hillard CJ, Seagard JL, Hopp FA, Hogan QH. Upregulation of fatty acid amide hydrolase in the dorsal periaqueductal gray is associated with neuropathic pain and reduced heart rate in rats. Am J Physiol Regul Integr Comp Physiol 2017; 312:R585-R596. [PMID: 28148494 DOI: 10.1152/ajpregu.00481.2016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Revised: 01/26/2017] [Accepted: 01/31/2017] [Indexed: 11/22/2022]
Abstract
Nerve damage can induce a heightened pain response to noxious stimulation, which is termed hyperalgesia. Pain itself acts as a stressor, initiating autonomic and sensory effects through the dorsal periaqueductal gray (dPAG) to induce both sympathoexcitation and analgesia, which prior studies have shown to be affected by endocannabinoid signaling. The present study addressed the hypothesis that neuropathic pain disrupts autonomic and analgesic regulation by endocannabinoid signaling in the dPAG. Endocannabinoid contents, transcript levels of endocannabinoid signaling components, and catabolic enzyme activity were analyzed in the dPAG of rats at 21 days after painful nerve injury. The responses to two nerve injury models were similar, with two-thirds of animals developing hyperalgesia that was maintained throughout the postinjury period, whereas no sustained change in sensory function was observed in the remaining rats. Anandamide content was lower in the dPAG of rats that developed sustained hyperalgesia, and activity of the catabolic enzyme fatty acid amide hydrolase (FAAH) was higher. Intensity of hyperalgesia was correlated to transcript levels of FAAH and negatively correlated to heart rate and sympathovagal balance. These data suggest that maladaptive endocannabinoid signaling in the dPAG after nerve injury could contribute to chronic neuropathic pain and associated autonomic dysregulation. This study demonstrates that reduced anandamide content and upregulation of FAAH in the dPAG are associated with hyperalgesia and reduced heart rate sustained weeks after nerve injury. These data provide support for the evaluation of FAAH inhibitors for the treatment of chronic neuropathic pain.
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Affiliation(s)
- Caron Dean
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, Wisconsin; .,Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin
| | - Cecilia J Hillard
- Department of Pharmacology, Medical College of Wisconsin, Milwaukee, Wisconsin; and
| | - Jeanne L Seagard
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, Wisconsin.,Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin
| | - Francis A Hopp
- Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin
| | - Quinn H Hogan
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, Wisconsin.,Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin
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Hahn AH, Merullo DP, Spool JA, Angyal CS, Stevenson SA, Riters LV. Song-associated reward correlates with endocannabinoid-related gene expression in male European starlings (Sturnus vulgaris). Neuroscience 2017; 346:255-266. [PMID: 28147243 DOI: 10.1016/j.neuroscience.2017.01.028] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Revised: 01/16/2017] [Accepted: 01/17/2017] [Indexed: 01/08/2023]
Abstract
Vocal communication is required for successful social interactions in numerous species. During the breeding season, songbirds produce songs that are reinforced by behavioral consequences (e.g., copulation). However, some songbirds also produce songs not obviously directed at other individuals. The consequences maintaining or reinforcing these songs are less obvious and the neural mechanisms associated with undirected communication are not well-understood. Previous studies indicate that undirected singing is intrinsically rewarding and mediated by opioid or dopaminergic systems; however, endocannabinoids are also involved in regulating reward and singing behavior. We used a conditioned place preference paradigm to examine song-associated reward in European starlings and quantitative real-time PCR to measure expression of endocannabinoid-related neural markers (CB1, FABP7, FABP5, FAAH, DAGLα), in brain regions involved in social behavior, reward and motivation (ventral tegmental area [VTA], periaqueductal gray [PAG], and medial preoptic nucleus [POM]), and a song control region (Area X). Our results indicate that starlings producing high rates of song developed a conditioned place preference, suggesting that undirected song is associated with a positive affective state. We found a significant positive relationship between song-associated reward and CB1 receptors in VTA and a significant negative relationship between song-associated reward and CB1 in PAG. There was a significant positive relationship between reward and the cannabinoid transporter FABP7 in POM and a significant negative relationship between reward and FABP7 in PAG. In Area X, FABP5 and DAGLα correlated positively with singing. These results suggest a role for endocannabinoid signaling in vocal production and reward associated with undirected communication.
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Affiliation(s)
- Allison H Hahn
- Department of Zoology, 426 Birge Hall, 430 Lincoln Drive, University of Wisconsin-Madison, Madison, WI 53706, USA.
| | - Devin P Merullo
- Department of Zoology, 426 Birge Hall, 430 Lincoln Drive, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Jeremy A Spool
- Department of Zoology, 426 Birge Hall, 430 Lincoln Drive, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Caroline S Angyal
- Department of Zoology, 426 Birge Hall, 430 Lincoln Drive, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Sharon A Stevenson
- Department of Zoology, 426 Birge Hall, 430 Lincoln Drive, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Lauren V Riters
- Department of Zoology, 426 Birge Hall, 430 Lincoln Drive, University of Wisconsin-Madison, Madison, WI 53706, USA
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Abstract
Cannabis has been widely used as a medicinal agent in Eastern medicine with earliest evidence in ancient Chinese practice dating back to 2700 BC. Over time, the use of medical cannabis has been increasingly adopted by Western medicine and is thus a rapidly emerging field that all pain physicians need to be aware of. Several randomized controlled trials have shown a significant and dose-dependent relationship between neuropathic pain relief and tetrahydrocannabinol – the principal psychoactive component of cannabis. Despite this, barriers exist to use from both the patient perspective (cost, addiction, social stigma, lack of understanding regarding safe administration) and the physician perspective (credibility, criminality, clinical evidence, patient addiction, and policy from the governing medical colleges). This review addresses these barriers and draws attention to key concerns in the Canadian medical system, providing updated treatment approaches to help clinicians work with their patients in achieving adequate pain control, reduced narcotic medication use, and enhanced quality of life. This review also includes case studies demonstrating the use of medical marijuana by patients with neuropathic low-back pain, neuropathic pain in fibromyalgia, and neuropathic pain in multiple sclerosis. While significant preclinical data have demonstrated the potential therapeutic benefits of cannabis for treating pain in osteoarthritis, rheumatoid arthritis, fibromyalgia, and cancer, further studies are needed with randomized controlled trials and larger study populations to identify the specific strains and concentrations that will work best with selected cohorts.
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Affiliation(s)
- Gordon D Ko
- Apollo Applied Research Inc.; Department of Medicine, Sunnybrook Health Sciences Centre, University of Toronto, Toronto
| | | | - Sean Mindra
- University of Ottawa Medical School, Ottawa, ON, Canada
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Tryon VL, Mizumori SJY, Morgan MM. Analysis of morphine-induced changes in the activity of periaqueductal gray neurons in the intact rat. Neuroscience 2016; 335:1-8. [PMID: 27545314 DOI: 10.1016/j.neuroscience.2016.08.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Revised: 07/09/2016] [Accepted: 08/11/2016] [Indexed: 11/29/2022]
Abstract
Microinjection of morphine into the periaqueductal gray (PAG) produces antinociception. In vitro slice recordings indicate that all PAG neurons are sensitive to morphine either by direct inhibition or indirect disinhibition. We tested the hypothesis that all PAG neurons respond to opioids in vivo by examining the extracellular activity of PAG neurons recorded in lightly anesthetized and awake rats. Spontaneous activity was less than 1Hz in most neurons. Noxious stimuli (heat, pinch) caused an increase in activity in 57% and 75% of the neurons recorded in anesthetized and awake rats, respectively. The same noxious stimuli caused a decrease in activity in only 17% and 6% of neurons recorded in anesthetized and awake rats. Systemic administration of morphine caused approximately equal numbers of neurons to increase, decrease, or show no change in activity in lightly anesthetized rats. In contrast, administration of morphine caused an increase in the activity of 22 of the 27 neurons recorded in awake rats. No change in activity was evident in the remaining five neurons. Changes in activity caused by morphine were surprisingly modest (a median increase from 0.7 to 1.3Hz). The small inconsistent effects of morphine are in stark contrast to the large changes produced by morphine on the activity of rostral ventromedial medulla (RVM) neurons or the widespread inhibition and excitation of PAG neurons treated with opioids in in vitro slice experiments. The relatively modest effects of morphine in the present study suggest that morphine produces antinociception by causing small changes in the activity of many PAG neurons.
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Affiliation(s)
- Valerie L Tryon
- Department of Psychology, University of Washington, Guthrie Hall, Room 119A, UW Box 351525, Seattle, WA 98195, USA.
| | - Sheri J Y Mizumori
- Department of Psychology, University of Washington, Guthrie Hall, Room 119A, UW Box 351525, Seattle, WA 98195, USA.
| | - Michael M Morgan
- Department of Psychology, Washington State University, Vancouver, 14204 NE Salmon Creek Avenue, Vancouver, WA 98686, USA.
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Wills KL, Parker LA. Effect of Pharmacological Modulation of the Endocannabinoid System on Opiate Withdrawal: A Review of the Preclinical Animal Literature. Front Pharmacol 2016; 7:187. [PMID: 27445822 PMCID: PMC4923145 DOI: 10.3389/fphar.2016.00187] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 06/13/2016] [Indexed: 01/20/2023] Open
Abstract
Over the years, animal studies have revealed a role for the endocannabinoid system in the regulation of multiple aspects of opiate addiction. The current review provides an overview of this literature in regards to opiate withdrawal. The opiate withdrawal syndrome, hypothesized to act as a negative reinforcer in mediating continued drug use, can be characterized by the emergence of spontaneous or precipitated aversive somatic and affective states following the termination of drug use. The behaviors measured to quantify somatic opiate withdrawal and the paradigms employed to assess affective opiate withdrawal (e.g., conditioned place aversion) in both acutely and chronically dependent animals are discussed in relation to the ability of the endocannabinoid system to modulate these behaviors. Additionally, the brain regions mediating somatic and affective opiate withdrawal are elucidated with respect to their modulation by the endocannabinoid system. Ultimately, a review of these findings reveals dissociations between the brain regions mediating somatic and affective opiate withdrawal, and the ability of cannabinoid type 1 (CB1) receptor agonism/antagonism to interfere with opiate withdrawal within different brain sub regions.
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Affiliation(s)
- Kiri L Wills
- Department of Psychology and Collaborative Neuroscience Program, University of Guelph, Guelph ON, Canada
| | - Linda A Parker
- Department of Psychology and Collaborative Neuroscience Program, University of Guelph, Guelph ON, Canada
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Molecular Mechanisms of Cannabis Signaling in the Brain. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2015; 137:123-47. [PMID: 26810000 DOI: 10.1016/bs.pmbts.2015.10.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Cannabis has been cultivated and used by humans for thousands of years. Research for decades was focused on understanding the mechanisms of an illegal/addictive drug. This led to the discovery of the vast endocannabinoid system. Research has now shifted to understanding fundamental biological questions related to one of the most widespread signaling systems in both the brain and the body. Our understanding of cannabinoid signaling has advanced significantly in the last two decades. In this review, we discuss the state of knowledge on mechanisms of Cannabis signaling in the brain and the modulation of key brain neurotransmitter systems involved in both brain reward/addiction and psychiatric disorders. It is highly probable that various cannabinoids will be found to be efficacious in the treatment of a number of psychiatric disorders. However, while there is clearly much potential, marijuana has not been properly vetted by the medical-scientific evaluation process and there are clearly a range of potentially adverse side-effects-including addiction. We are at crossroads for research on endocannabinoid function and therapeutics (including the use of exogenous treatments such as Cannabis). With over 100 cannabinoid constituents, the majority of which have not been studied, there is much Cannabis research yet to be done. With more states legalizing both the medicinal and recreational use of marijuana the rigorous scientific investigation into cannabinoid signaling is imperative.
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Cannabinoid Ligands and Alcohol Addiction: A Promising Therapeutic Tool or a Humbug? Neurotox Res 2015; 29:173-96. [PMID: 26353844 PMCID: PMC4701763 DOI: 10.1007/s12640-015-9555-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Revised: 08/04/2015] [Accepted: 08/06/2015] [Indexed: 01/08/2023]
Abstract
The vast therapeutic potential of cannabinoids of both synthetic and plant-derived origins currently makes these compounds the focus of a growing interest. Although cannabinoids are still illicit drugs, their possible clinical usefulness, including treatment of acute or neuropathic pain, have been suggested by several studies. In addition, some observations indicate that cannabinoid receptor antagonists may be useful for the treatment of alcohol dependence and addiction, which is a major health concern worldwide. While the synergism between alcohol and cannabinoid agonists (in various forms) creates undesirable side effects when the two are consumed together, the administration of CB1 antagonists leads to a significant reduction in alcohol consumption. Furthermore, cannabinoid antagonists also mitigate alcohol withdrawal symptoms. Herein, we present an overview of studies focusing on the effects of cannabinoid ligands (agonists and antagonists) during acute or chronic consumption of ethanol.
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Fitzgibbon M, Finn DP, Roche M. High Times for Painful Blues: The Endocannabinoid System in Pain-Depression Comorbidity. Int J Neuropsychopharmacol 2015; 19:pyv095. [PMID: 26342110 PMCID: PMC4815466 DOI: 10.1093/ijnp/pyv095] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 08/17/2015] [Indexed: 01/06/2023] Open
Abstract
Depression and pain are two of the most debilitating disorders worldwide and have an estimated cooccurrence of up to 80%. Comorbidity of these disorders is more difficult to treat, associated with significant disability and impaired health-related quality of life than either condition alone, resulting in enormous social and economic cost. Several neural substrates have been identified as potential mediators in the association between depression and pain, including neuroanatomical reorganization, monoamine and neurotrophin depletion, dysregulation of the hypothalamo-pituitary-adrenal axis, and neuroinflammation. However, the past decade has seen mounting evidence supporting a role for the endogenous cannabinoid (endocannabinoid) system in affective and nociceptive processing, and thus, alterations in this system may play a key role in reciprocal interactions between depression and pain. This review will provide an overview of the preclinical evidence supporting an interaction between depression and pain and the evidence supporting a role for the endocannabinoid system in this interaction.
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Affiliation(s)
| | | | - Michelle Roche
- Physiology (Ms Fitzgibbon and Dr Roche), and Pharmacology and Therapeutics (Dr Finn), School of Medicine, Galway Neuroscience Centre and Centre for Pain Research (Ms Fitzgibbon, Dr Finn, and Dr Roche), National Centre for Biomedical Engineering Science, National University of Ireland Galway, Ireland.
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Ly HG, Ceccarini J, Weltens N, Bormans G, Van Laere K, Tack J, Van Oudenhove L. Increased cerebral cannabinoid-1 receptor availability is a stable feature of functional dyspepsia: a [F]MK-9470 PET study. PSYCHOTHERAPY AND PSYCHOSOMATICS 2015; 84:149-58. [PMID: 25833408 DOI: 10.1159/000375454] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Accepted: 01/17/2015] [Indexed: 11/19/2022]
Abstract
BACKGROUND Functional dyspepsia (FD) is a prevalent functional gastrointestinal disorder (FGID) defined by chronic epigastric symptoms in the absence of organic abnormalities likely to explain them. Comorbidity with mood and anxiety disorders as well as with other FGIDs and functional somatic syndrome (FSS) is high. FD is characterized by abnormal regional cerebral activity in cognitive/affective pain modulatory circuits, but it is unknown which neurotransmitter systems are involved. The authors aimed to assess and compare in vivo cerebral cannabinoid-1 (CB1) receptor availability between FD patients and age-, gender- and BMI-matched healthy controls (HC). METHODS Twelve FD patients and 12 matched HC were investigated using positron emission tomography (PET) with the CB1 receptor radioligand [(18)F]MK-9470. Nine of the patients received a second PET scan after a naturalistic follow-up period of 36 ± 9.6 months (range: 25.2-50.4 months). RESULTS FD patients had significantly higher CB1 receptor availability in the cerebral regions involved in (visceral) nociception (brainstem, insula, anterior cingulate cortex) as well as in the homeostatic and hedonic regulation of food intake [hypothalamus, (ventral) striatum] (p < 0.05 corrected for multiple testing, region of interest analysis), which persisted after a follow-up period of 36 ± 9.6 months. CONCLUSIONS Although these findings need replication in larger samples, they suggest that the abnormal brain activity in several of these regions, previously demonstrated in FD, may be due to a sustained endocannabinoid system dysfunction, identifying it as a potential novel target for treatment and warranting further studies to elucidate whether it is also a feature of other FGIDs or FSSs.
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Affiliation(s)
- Huynh Giao Ly
- Translational Research Center for Gastrointestinal Disorders (TARGID), Department of Clinical and Experimental Medicine, Leuven, Belgium
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Ibrahim BM, Abdel-Rahman AA. A pivotal role for enhanced brainstem Orexin receptor 1 signaling in the central cannabinoid receptor 1-mediated pressor response in conscious rats. Brain Res 2015; 1622:51-63. [PMID: 26096126 DOI: 10.1016/j.brainres.2015.06.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Revised: 06/11/2015] [Accepted: 06/12/2015] [Indexed: 01/02/2023]
Abstract
Orexin receptor 1 (OX1R) signaling is implicated in cannabinoid receptor 1 (CB1R) modulation of feeding. Further, our studies established the dependence of the central CB1R-mediated pressor response on neuronal nitric oxide synthase (nNOS) and extracellular signal-regulated kinase1/2 (ERK1/2) phosphorylation in the RVLM. Here, we tested the novel hypothesis that brainstem orexin-A/OX1R signaling plays a pivotal role in the central CB1R-mediated pressor response. Our multiple labeling immunofluorescence findings revealed co-localization of CB1R, OX1R and the peptide orexin-A within the C1 area of the rostral ventrolateral medulla (RVLM). Activation of central CB1R following intracisternal (i.c.) WIN55,212-2 (15μg/rat) in conscious rats caused significant increases in BP and orexin-A level in RVLM neuronal tissue. Additional studies established a causal role for orexin-A in the central CB1R-mediated pressor response because (i) selective blockade of central CB1R (AM251, 30μg/rat; i.c.) abrogated WIN55,212-2-evoked increases in RVLM orexin-A level, (ii) the selective OX1R antagonist SB-408124 (10nmol/rat; i.c.) attenuated orexin-A (3nmol/rat; i.c.) or WIN55,212-2 (15μg/rat; i.c.)-evoked pressor response while selective CB1R blockade (AM251) had no effect on orexin-A (3nmol/rat; i.c.)-evoked pressor response, (iii) direct CB1R activation in the RVLM (WIN55,212-2; 0.1μg/rat) increased RVLM orexin-A and BP. Finally, SB-408124 attenuated WIN55,212-2-evoked increases in RVLM nNOS and ERK1/2 phosphorylation and BP. Our findings suggest that orexin-A/OX1R dependent activation of the RVLM nNOS/ERK1/2 cascade is essential neurochemical mechanism for the central CB1R-mediated pressor response in conscious rats.
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Affiliation(s)
- Badr Mostafa Ibrahim
- Department of Pharmacology & Toxicology, Brody School of Medicine, East Carolina University, 600 Moye Boulevard, Greenville, NC 27858, United States
| | - Abdel A Abdel-Rahman
- Department of Pharmacology & Toxicology, Brody School of Medicine, East Carolina University, 600 Moye Boulevard, Greenville, NC 27858, United States.
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Gamage TF, Ignatowska-Jankowska BM, Muldoon PP, Cravatt BF, Damaj MI, Lichtman AH. Differential effects of endocannabinoid catabolic inhibitors on morphine withdrawal in mice. Drug Alcohol Depend 2015; 146:7-16. [PMID: 25479915 PMCID: PMC4295928 DOI: 10.1016/j.drugalcdep.2014.11.015] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Revised: 11/16/2014] [Accepted: 11/16/2014] [Indexed: 02/07/2023]
Abstract
BACKGROUND Inhibition of endocannabinoid catabolic enzymes fatty acid amide hydrolase (FAAH) and/or monoacylglycerol lipase (MAGL) reduces somatic morphine withdrawal signs, but its effects on aversive aspects of withdrawal are unknown. The present study investigated whether Δ(9)-tetrahydrocannabinol (THC), the MAGL inhibitor JZL184, the FAAH inhibitor PF-3845, or the dual FAAH/MAGL inhibitor SA-57 would reduce acquisition of morphine withdrawal-induced conditioned place avoidance (CPA) and jumping. METHODS Mice were implanted with placebo or 75 mg morphine pellets, 48 h later injected with naloxone or saline and placed in the conditioning apparatus, and assessed for CPA at 72 h. Subjects were also observed for jumping behavior following naloxone challenge. RESULTS Naloxone (0.056 mg/kg) produced robust CPA in morphine-pelleted, but not placebo-pelleted, mice. Morphine pretreatment prevented the occurrence of withdrawal CPA and withdrawal jumping, while clonidine (an α2 adrenergic receptor agonist) only blocked withdrawal CPA. THC, JZL184, and SA-57 significantly reduced the percentage of mice that jumped during the conditioning session, but did not affect acquisition of withdrawal CPA. PF-3845 did not reduce morphine withdrawal CPA or jumping. Finally, neither THC nor the endocannabinoid catabolic enzyme inhibitors in non-dependent mice elicited a conditioned place preference or aversion. CONCLUSIONS These findings suggest that inhibiting endocannabinoid catabolic enzymes reduces somatic morphine withdrawal signs, but not aversive aspects as inferred in the CPA paradigm. The observation that non-dependent mice administered inhibitors of endocannabinoid degradation did not display place preferences is consistent with the idea that that endocannabinoid catabolic enzymes might be targeted therapeutically, with reduced risk of abuse.
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Affiliation(s)
- Thomas F. Gamage
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Kontos Medical Sciences Building, 1217 East Marshall Street, Richmond, VA, 23298
| | - Bogna M. Ignatowska-Jankowska
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Kontos Medical Sciences Building, 1217 East Marshall Street, Richmond, VA, 23298
| | - Pretal P. Muldoon
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Kontos Medical Sciences Building, 1217 East Marshall Street, Richmond, VA, 23298
| | - Benjamin F. Cravatt
- The Skaggs Institute for Chemical Biology and Department of Chemical Physiology, The Scripps Research Institute, 10550 N. Torrey Pines Rd. La Jolla, CA 92037
| | - M. Imad Damaj
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Kontos Medical Sciences Building, 1217 East Marshall Street, Richmond, VA, 23298
| | - Aron H. Lichtman
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Kontos Medical Sciences Building, 1217 East Marshall Street, Richmond, VA, 23298
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Wilson-Poe AR, Lau BK, Vaughan CW. Repeated morphine treatment alters cannabinoid modulation of GABAergic synaptic transmission within the rat periaqueductal grey. Br J Pharmacol 2014; 172:681-90. [PMID: 24916363 DOI: 10.1111/bph.12809] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2013] [Revised: 05/29/2014] [Accepted: 06/05/2014] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND AND PURPOSE Cannabinoids and opioids produce antinociception by modulating GABAergic synaptic transmission in a descending analgesic pathway from the midbrain periaqueductal grey (PAG). While chronic opioid treatment produces opioid tolerance, it has recently been shown to enhance cannabinoid-induced antinociception within the PAG. This study examined the effect of repeated opioid treatment on opioid and cannabinoid presynaptic modulation of GABAergic synaptic transmission in PAG. EXPERIMENTAL APPROACH Midbrain PAG slices were prepared from untreated rats, and rats that had undergone repeated morphine or saline pretreatment. Whole-cell voltage-clamp recordings were made from neurons within the ventrolateral PAG. KEY RESULTS In slices from untreated animals, the cannabinoid receptor agonist WIN55212 and the μ receptor agonist DAMGO inhibited electrically evoked GABAA receptor-mediated inhibitory postsynaptic currents (IPSCs) IPSCs in PAG neurons, with IC50 s of 30 and 100 nM respectively. The inhibition of evoked IPSCs produced by WIN55212 (30 nM) and DAMGO (100 nM) was similar in PAG neurons from morphine- and saline-treated animals. The cannabinoid CB1 receptor antagonist AM251 increased the frequency of spontaneous miniature IPSCs in PAG neurons from repeated morphine-, but not saline-treated animals. DAMGO inhibition of evoked IPSCs was enhanced in the presence of AM251 in morphine-, but not saline-treated animals. CONCLUSIONS AND IMPLICATIONS These results indicate that the efficiency of agonist-induced inhibition of GABAergic synaptic transmission is enhanced by morphine treatment, although this is dampened by endocannabinoid-mediated tonic inhibition. Thus, endocannabinoid modulation of synaptic transmission could provide an alternative analgesic approach in a morphine-tolerant state. LINKED ARTICLES This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2.
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Affiliation(s)
- A R Wilson-Poe
- Pain Management Research Institute, Kolling Institute for Medical Research, Northern Clinical School, The University of Sydney, St Leonards, NSW, Australia
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Grim TW, Ghosh S, Hsu KL, Cravatt BF, Kinsey SG, Lichtman AH. Combined inhibition of FAAH and COX produces enhanced anti-allodynic effects in mouse neuropathic and inflammatory pain models. Pharmacol Biochem Behav 2014; 124:405-11. [PMID: 25058512 PMCID: PMC4206939 DOI: 10.1016/j.pbb.2014.07.008] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Revised: 07/09/2014] [Accepted: 07/11/2014] [Indexed: 12/31/2022]
Abstract
UNLABELLED Common pharmacological treatments of neuropathic and chronic inflammatory pain conditions generally lack efficacy and/or are associated with significant untoward side effects. However, recent preclinical data indicate that combined inhibition of cyclooxygenase (COX) and fatty acid amide hydrolase (FAAH), the primary catabolic enzyme of the endocannabinoid N-arachidonoylethanolamine (anandamide; AEA), produces enhanced antinociceptive effects in a variety of murine models of pain. Accordingly, the primary objective of the present study was to investigate the consequences of co-administration of the COX inhibitor diclofenac and the highly selective FAAH inhibitor PF-3845 in models of neuropathic pain (i.e., chronic constrictive injury of the sciatic nerve (CCI)) and inflammatory pain induced by an intraplantar injection of carrageenan. Here, we report that combined administration of subthreshold doses of these drugs produced enhanced antinociceptive effects in CCI and carrageenan pain models, the latter of which was demonstrated to require both CB1 and CB2 receptors. The combined administration of subthreshold doses of these drugs also increased AEA levels and decreased prostaglandin levels in whole brain. Together, these data add to the growing research that dual blockade of FAAH and COX represents a potential therapeutic strategy for the treatment of neuropathic and inflammatory pain states. PERSPECTIVE Tandem inhibition of FAAH and COX attenuates inflammatory and neuropathic pain states, which may avoid potentially harmful side effects of other therapeutic options, such as NSAIDs or opioids.
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Affiliation(s)
- Travis W Grim
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298-0613, USA.
| | - Sudeshna Ghosh
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298-0613, USA
| | - Ku-Lung Hsu
- Department of Chemical Physiology, The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 N. Torrey Pines Rd., La Jolla, CA 92037, USA
| | - Benjamin F Cravatt
- Department of Chemical Physiology, The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 N. Torrey Pines Rd., La Jolla, CA 92037, USA
| | - Steven G Kinsey
- Department of Psychology, West Virginia University, Morgantown, WV 26506, USA
| | - Aron H Lichtman
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298-0613, USA
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Detection of cannabinoid receptors CB1 and CB2 within basal ganglia output neurons in macaques: changes following experimental parkinsonism. Brain Struct Funct 2014; 220:2721-38. [PMID: 24972960 PMCID: PMC4549378 DOI: 10.1007/s00429-014-0823-8] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Accepted: 06/10/2014] [Indexed: 11/21/2022]
Abstract
Although type 1 cannabinoid receptors (CB1Rs) are expressed abundantly throughout the brain, the presence of type 2 cannabinoid receptors (CB2Rs) in neurons is still somewhat controversial. Taking advantage of newly designed CB1R and CB2R mRNA riboprobes, we demonstrate by PCR and in situ hybridization that transcripts for both cannabinoid receptors are present within labeled pallidothalamic-projecting neurons of control and MPTP-treated macaques, whereas the expression is markedly reduced in dyskinetic animals. Moreover, an in situ proximity ligation assay was used to qualitatively assess the presence of CB1Rs and CB2Rs, as well as CB1R–CB2R heteromers within basal ganglia output neurons in all animal groups (control, parkinsonian and dyskinetic macaques). A marked reduction in the number of CB1Rs, CB2Rs and CB1R–CB2R heteromers was found in dyskinetic animals, mimicking the observed reduction in CB1R and CB2R mRNA expression levels. The fact that chronic levodopa treatment disrupted CB1R–CB2R heteromeric complexes should be taken into consideration when designing new drugs acting on cannabinoid receptor heteromers.
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47
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Adult cyclical vomiting syndrome: a disorder of allostatic regulation? Exp Brain Res 2014; 232:2541-7. [DOI: 10.1007/s00221-014-3939-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Accepted: 03/25/2014] [Indexed: 10/25/2022]
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Desroches J, Bouchard JF, Gendron L, Beaulieu P. Involvement of cannabinoid receptors in peripheral and spinal morphine analgesia. Neuroscience 2014; 261:23-42. [DOI: 10.1016/j.neuroscience.2013.12.030] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Revised: 10/27/2013] [Accepted: 12/13/2013] [Indexed: 10/25/2022]
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Flores A, Maldonado R, Berrendero F. Cannabinoid-hypocretin cross-talk in the central nervous system: what we know so far. Front Neurosci 2013; 7:256. [PMID: 24391536 PMCID: PMC3868890 DOI: 10.3389/fnins.2013.00256] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Accepted: 12/09/2013] [Indexed: 12/22/2022] Open
Abstract
Emerging findings suggest the existence of a cross-talk between hypocretinergic and endocannabinoid systems. Although few studies have examined this relationship, the apparent overlap observed in the neuroanatomical distribution of both systems as well as their putative functions strongly point to the existence of such cross-modulation. In agreement, biochemical and functional studies have revealed the existence of heterodimers between CB1 cannabinoid receptor and hypocretin receptor-1, which modulates the cellular localization and downstream signaling of both receptors. Moreover, the activation of hypocretin receptor-1 stimulates the synthesis of 2-arachidonoyl glycerol culminating in the retrograde inhibition of neighboring cells and suggesting that endocannabinoids could contribute to some hypocretin effects. Pharmacological data indicate that endocannabinoids and hypocretins might have common physiological functions in the regulation of appetite, reward and analgesia. In contrast, these neuromodulatory systems seem to play antagonistic roles in the regulation of sleep/wake cycle and anxiety-like responses. The present review attempts to piece together what is known about this interesting interaction and describes its potential therapeutic implications.
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Affiliation(s)
- Africa Flores
- Laboratory of Neuropharmacology, Department of Experimental and Health Sciences, Universitat Pompeu Fabra Barcelona, Spain
| | - Rafael Maldonado
- Laboratory of Neuropharmacology, Department of Experimental and Health Sciences, Universitat Pompeu Fabra Barcelona, Spain
| | - Fernando Berrendero
- Laboratory of Neuropharmacology, Department of Experimental and Health Sciences, Universitat Pompeu Fabra Barcelona, Spain
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Abstract
This paper is the thirty-fifth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2012 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).
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Affiliation(s)
- Richard J Bodnar
- Department of Psychology and Neuropsychology Doctoral Sub-Program, Queens College, City University of New York, Flushing, NY 11367, United States.
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