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Straiker A, Dvorakova M, Bosquez-Berger T, Blahos J, Mackie K. A collection of cannabinoid-related negative findings from autaptic hippocampal neurons. Sci Rep 2023; 13:9610. [PMID: 37311900 PMCID: PMC10264370 DOI: 10.1038/s41598-023-36710-3] [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: 10/13/2022] [Accepted: 06/08/2023] [Indexed: 06/15/2023] Open
Abstract
Autaptic hippocampal neurons are an architecturally simple model of neurotransmission that express several forms of cannabinoid signaling. Over the past twenty years this model has proven valuable for studies ranging from enzymatic control of endocannabinoid production and breakdown, to CB1 receptor structure/function, to CB2 signaling, understanding 'spice' (synthetic cannabinoid) pharmacology, and more. However, while studying cannabinoid signaling in these neurons, we have occasionally encountered what one might call 'interesting negatives', valid and informative findings in the context of our experimental design that, given the nature of scientific publishing, may not otherwise find their way into the scientific literature. In autaptic hippocampal neurons we have found that: (1) The fatty acid binding protein (FABP) blocker SBFI-26 does not alter CB1-mediated neuroplasticity. (2) 1-AG signals poorly relative to 2-AG in autaptic neurons. (3) Indomethacin is not a CB1 PAM in autaptic neurons. (4) The CB1-associated protein SGIP1a is not necessary for CB1 desensitization. We are presenting these negative or perplexing findings in the hope that they will prove beneficial to other laboratories and elicit fruitful discussions regarding their relevance and significance.
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Affiliation(s)
- Alex Straiker
- Department of Psychological and Brain Sciences, Gill Center for Biomolecular Science, Program in Neuroscience, Indiana University, Bloomington, IN, 47405, USA.
| | - Michaela Dvorakova
- Department of Psychological and Brain Sciences, Gill Center for Biomolecular Science, Program in Neuroscience, Indiana University, Bloomington, IN, 47405, USA
| | - Taryn Bosquez-Berger
- Department of Psychological and Brain Sciences, Gill Center for Biomolecular Science, Program in Neuroscience, Indiana University, Bloomington, IN, 47405, USA
| | - Jaroslav Blahos
- Department of Molecular Pharmacology, Institute of Molecular Genetics of the Czech Academy of Sciences, Videnska 1083, 142 20, Prague 4, Czech Republic
| | - Ken Mackie
- Department of Psychological and Brain Sciences, Gill Center for Biomolecular Science, Program in Neuroscience, Indiana University, Bloomington, IN, 47405, USA
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Pagliusi M, Gomes FV. The Role of The Rostral Ventromedial Medulla in Stress Responses. Brain Sci 2023; 13:brainsci13050776. [PMID: 37239248 DOI: 10.3390/brainsci13050776] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Revised: 04/30/2023] [Accepted: 05/05/2023] [Indexed: 05/28/2023] Open
Abstract
The rostral ventromedial medulla (RVM) is a brainstem structure critical for the descending pain modulation system involved in both pain facilitation and inhibition through its projection to the spinal cord. Since the RVM is well connected with pain- and stress-engaged brain structures, such as the anterior cingulate cortex, nucleus accumbens, and amygdala, its involvement in stress responses has become a matter of great interest. While chronic stress has been proposed as a trigger of pain chronification and related psychiatric comorbidities due to maladaptive stress responses, acute stress triggers analgesia and other adaptative responses. Here we reviewed and highlighted the critical role of the RVM in stress responses, mainly in acute stress-induced analgesia (SIA) and chronic stress-induced hyperalgesia (SIH), providing insights into pain chronification processes and comorbidity between chronic pain and psychiatric disorders.
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Affiliation(s)
- Marco Pagliusi
- Department of Pharmacology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto 14015-069, SP, Brazil
| | - Felipe V Gomes
- Department of Pharmacology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto 14015-069, SP, Brazil
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3
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UHPLC-ESI-MS/MS assay for quantification of endocannabinoids in cerebrospinal fluid using surrogate calibrant and surrogate matrix approaches. J Pharm Biomed Anal 2023; 222:115090. [DOI: 10.1016/j.jpba.2022.115090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 10/01/2022] [Accepted: 10/02/2022] [Indexed: 11/07/2022]
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Nocheva H, Sabit Z, Bakalov D, Grigorov E. Interactions between the cannabinoid and the serotonergic systems in modulation of pain perception. PHARMACIA 2021. [DOI: 10.3897/pharmacia.68.e49219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The aim of our study was to evaluate the effects of cannabinoids and serotonergic system on nociception in intact rats and after heat stress. Cannabinoid receptor type 1 (CB1) and 5-hydroxytryptamine receptor (5НТ1А) agonists and antagonists have been administered according to different experimental designs (alone and in combinations) in intact male Wistar rats, as well in animals subjected to one hour of heat stress. Pain perception has been evaluated by Paw pressure test. Our results pointed out that cannabinoids and the serotonergic system interact in nociception in intact animals as well as after heat stress. Cannabinoids seemed to have less prominent role in such interaction in intact animals than after heat stress. The interplay between the two systems probably involves different mechanisms in intact animals and after heat stress with time-dependent effects. The interaction between the cannabinoid and the serotonergic systems exerts a modulating rather than mediating effect on h-SIA.
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Corcoran L, Mattimoe D, Roche M, Finn DP. Attenuation of fear-conditioned analgesia in rats by monoacylglycerol lipase inhibition in the anterior cingulate cortex: Potential role for CB 2 receptors. Br J Pharmacol 2020; 177:2240-2255. [PMID: 31967664 PMCID: PMC7174879 DOI: 10.1111/bph.14976] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2019] [Revised: 12/01/2019] [Accepted: 12/19/2019] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND AND PURPOSE Improved understanding of brain mechanisms regulating endogenous analgesia is important from a fundamental physiological perspective and for identification of novel therapeutic strategies for pain. The endocannabinoid system plays a key role in stress-induced analgesia, including fear-conditioned analgesia (FCA), a potent form of endogenous analgesia. Here, we studied the role of the endocannabinoid 2-arachidonoyl glycerol (2-AG) within the anterior cingulate cortex (ACC; a brain region implicated in the affective component of pain) in FCA in rats. EXPERIMENTAL APPROACH FCA was modelled in male Lister-hooded rats by assessing formalin-evoked nociceptive behaviour in an arena previously paired with footshock. The effects of intra-ACC administration of MJN110 (inhibitor of monoacylglycerol lipase [MGL], the primary enzyme catabolizing 2-AG), AM630 (CB2 receptor antagonist), AM251 (CB1 receptor antagonist) or MJN110 + AM630 on FCA were assessed. KEY RESULTS MJN110 attenuated FCA when microinjected into the ACC, an effect associated with increased levels of 2-AG in the ACC. This effect of MJN110 on FCA was unaltered by co-administration of AM251 but was blocked by AM630, which alone reduced nociceptive behaviour in non-fear-conditioned rats. RT-qPCR confirmed that mRNA encoding CB1 and CB2 receptors was detectable in the ACC of formalin-injected rats and unchanged in those expressing FCA. CONCLUSION AND IMPLICATIONS These results suggest that an MGL substrate in the ACC, likely 2-AG, modulates FCA and that within the ACC, 2-AG-CB2 receptor signalling may suppress this form of endogenous analgesia. These results may facilitate increased understanding and improved treatment of pain- and fear-related disorders and their co-morbidity.
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Affiliation(s)
- Louise Corcoran
- Pharmacology and Therapeutics, School of MedicineNational University of Ireland GalwayGalwayIreland
- Galway Neuroscience Centre and Centre for Pain ResearchNational University of Ireland GalwayGalwayIreland
| | - Darragh Mattimoe
- Pharmacology and Therapeutics, School of MedicineNational University of Ireland GalwayGalwayIreland
- Galway Neuroscience Centre and Centre for Pain ResearchNational University of Ireland GalwayGalwayIreland
| | - Michelle Roche
- Physiology, School of MedicineNational University of Ireland GalwayGalwayIreland
- Galway Neuroscience Centre and Centre for Pain ResearchNational University of Ireland GalwayGalwayIreland
| | - David P. Finn
- Pharmacology and Therapeutics, School of MedicineNational University of Ireland GalwayGalwayIreland
- Galway Neuroscience Centre and Centre for Pain ResearchNational University of Ireland GalwayGalwayIreland
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6
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Role of Endocannabinoid System in the Peripheral Antinociceptive Action of Aripiprazole. Anesth Analg 2019; 129:263-268. [DOI: 10.1213/ane.0000000000003723] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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Poznański P, Lesniak A, Bujalska-Zadrozny M, Strzemecka J, Sacharczuk M. Bidirectional selection for high and low stress-induced analgesia affects G-protein activity. Neuropharmacology 2018; 144:37-42. [PMID: 30326238 DOI: 10.1016/j.neuropharm.2018.10.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Revised: 09/03/2018] [Accepted: 10/12/2018] [Indexed: 11/19/2022]
Abstract
Mice selected for high (HA) and low (LA) swim stress-induced analgesia (SSIA) are a unique model for studying the genetic background of this phenomenon. HA and LA miceshow substantial differences in the magnitude of the antinociceptive response to stress and when treated with exogenous opioids. However, the direct cause underplaying this distinctive feature has not yet been identified. The current study was designed to investigate the possibility that disturbances in G-protein signaling could explain the divergent response to opioid agonists. Supraspinal and spinal opioid sensitivity was assessed in vivo with intraperitoneal morphine and subsequent thermal stimulus exposure. The level of opioid receptor-mediated G-protein activation was investigated by means of DAMGO and morphine-stimulated [35S]GTPγS assay in the brain and spinal cord homogenates from HA and LA mice. Morphine (3-249 μmol/kg, i.p) was over 6 - and 3 - times more potent in HA than LA mice in the hot plate and tail-flick assays, respectively. Additionally, HA mice showed elevated β - endorphin levels in the brain. Enhanced efficacy of agonist-stimulated [35S]GTPγS binding was detected in opioid receptor-rich limbic regions of HA mice like the hypothalamus and hippocampus. Increased G-protein activity also emerged in the thalamus, periaqueductal gray matter and prefrontal cortex. In conclusion, the magnitude of the antinociceptive response to opioids in HA and LA mice is correlated with alterations in G-protein activation in brain regions responsible for integration and descending modulation of nociceptive information as well as at sites governing the emotional response to stressful stimuli.
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Affiliation(s)
- Piotr Poznański
- Department of Genomics, Institute of Genetics and Animal Breeding, Polish Academy of Sciences, Jastrzebiec, Poland
| | - Anna Lesniak
- Faculty of Pharmacy with the Laboratory Medicine Division, Department of Pharmacodynamics, Medical University of Warsaw, Centre for Preclinical Research and Technology, Warsaw, Poland
| | - Magdalena Bujalska-Zadrozny
- Faculty of Pharmacy with the Laboratory Medicine Division, Department of Pharmacodynamics, Medical University of Warsaw, Centre for Preclinical Research and Technology, Warsaw, Poland
| | - Joanna Strzemecka
- Institute of Health Sciences, Pope John Paul II State School of Higher Education, Biala Podlaska, Poland
| | - Mariusz Sacharczuk
- Faculty of Pharmacy with the Laboratory Medicine Division, Department of Pharmacodynamics, Medical University of Warsaw, Centre for Preclinical Research and Technology, Warsaw, Poland; Department of Genomics, Institute of Genetics and Animal Breeding, Polish Academy of Sciences, Jastrzebiec, Poland; Department of Internal Medicine, Hypertension and Vascular Diseases, Medical University of Warsaw, Warsaw, Poland.
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Acetaminophen Relieves Inflammatory Pain through CB 1 Cannabinoid Receptors in the Rostral Ventromedial Medulla. J Neurosci 2017; 38:322-334. [PMID: 29167401 DOI: 10.1523/jneurosci.1945-17.2017] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2017] [Revised: 10/27/2017] [Accepted: 11/14/2017] [Indexed: 12/30/2022] Open
Abstract
Acetaminophen (paracetamol) is a widely used analgesic and antipyretic drug with only incompletely understood mechanisms of action. Previous work, using models of acute nociceptive pain, indicated that analgesia by acetaminophen involves an indirect activation of CB1 receptors by the acetaminophen metabolite and endocannabinoid reuptake inhibitor AM 404. However, the contribution of the cannabinoid system to antihyperalgesia against inflammatory pain, the main indication of acetaminophen, and the precise site of the relevant CB1 receptors have remained elusive. Here, we analyzed acetaminophen analgesia in mice of either sex with inflammatory pain and found that acetaminophen exerted a dose-dependent antihyperalgesic action, which was mimicked by intrathecally injected AM 404. Both compounds lost their antihyperalgesic activity in CB1-/- mice, confirming the involvement of the cannabinoid system. Consistent with a mechanism downstream of proinflammatory prostaglandin formation, acetaminophen also reversed hyperalgesia induced by intrathecal prostaglandin E2 To distinguish between a peripheral/spinal and a supraspinal action, we administered acetaminophen and AM 404 to hoxB8-CB1-/- mice, which lack CB1 receptors from the peripheral nervous system and the spinal cord. These mice exhibited unchanged antihyperalgesia indicating a supraspinal site of action. Accordingly, local injection of the CB1 receptor antagonist rimonabant into the rostral ventromedial medulla blocked acetaminophen-induced antihyperalgesia, while local rostral ventromedial medulla injection of AM 404 reduced hyperalgesia in wild-type mice but not in CB1-/- mice. Our results indicate that the cannabinoid system contributes not only to acetaminophen analgesia against acute pain but also against inflammatory pain, and suggest that the relevant CB1 receptors reside in the rostral ventromedial medulla.SIGNIFICANCE STATEMENT Acetaminophen is a widely used analgesic drug with multiple but only incompletely understood mechanisms of action, including a facilitation of endogenous cannabinoid signaling via one of its metabolites. Our present data indicate that enhanced cannabinoid signaling is also responsible for the analgesic effects of acetaminophen against inflammatory pain. Local injections of the acetaminophen metabolite AM 404 and of cannabinoid receptor antagonists as well as data from tissue-specific CB1 receptor-deficient mice suggest the rostral ventromedial medulla as an important site of the cannabinoid-mediated analgesia by acetaminophen.
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Woodhams SG, Chapman V, Finn DP, Hohmann AG, Neugebauer V. The cannabinoid system and pain. Neuropharmacology 2017; 124:105-120. [PMID: 28625720 PMCID: PMC5785108 DOI: 10.1016/j.neuropharm.2017.06.015] [Citation(s) in RCA: 182] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Revised: 05/31/2017] [Accepted: 06/14/2017] [Indexed: 01/20/2023]
Abstract
Chronic pain states are highly prevalent and yet poorly controlled by currently available analgesics, representing an enormous clinical, societal, and economic burden. Existing pain medications have significant limitations and adverse effects including tolerance, dependence, gastrointestinal dysfunction, cognitive impairment, and a narrow therapeutic window, making the search for novel analgesics ever more important. In this article, we review the role of an important endogenous pain control system, the endocannabinoid (EC) system, in the sensory, emotional, and cognitive aspects of pain. Herein, we briefly cover the discovery of the EC system and its role in pain processing pathways, before concentrating on three areas of current major interest in EC pain research; 1. Pharmacological enhancement of endocannabinoid activity (via blockade of EC metabolism or allosteric modulation of CB1receptors); 2. The EC System and stress-induced modulation of pain; and 3. The EC system & medial prefrontal cortex (mPFC) dysfunction in pain states. Whilst we focus predominantly on the preclinical data, we also include extensive discussion of recent clinical failures of endocannabinoid-related therapies, the future potential of these approaches, and important directions for future research on the EC system and pain. This article is part of the Special Issue entitled "A New Dawn in Cannabinoid Neurobiology".
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Affiliation(s)
- Stephen G Woodhams
- Arthritis UK Pain Centre, School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, United Kingdom.
| | - Victoria Chapman
- Arthritis UK Pain Centre, School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, United Kingdom
| | - David P Finn
- Pharmacology & Therapeutics, School of Medicine, Galway Neuroscience Centre and Centre for Pain Research, NCBES, National University of Ireland Galway, University Road, Galway, Ireland
| | - Andrea G Hohmann
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, USA; Program in Neuroscience, Indiana University, Bloomington, IN, USA; Interdisciplinary Biochemistry Graduate Program, Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, USA; Gill Center for Biomolecular Science, Indiana University, Bloomington, IN, USA
| | - Volker Neugebauer
- Department of Pharmacology and Neuroscience, Center of Excellence for Translational Neuroscience and Therapeutics, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
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Summers T, Hanten B, Peterson W, Burrell B. Endocannabinoids Have Opposing Effects On Behavioral Responses To Nociceptive And Non-nociceptive Stimuli. Sci Rep 2017; 7:5793. [PMID: 28724917 PMCID: PMC5517658 DOI: 10.1038/s41598-017-06114-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Accepted: 06/08/2017] [Indexed: 11/09/2022] Open
Abstract
The endocannabinoid system is thought to modulate nociceptive signaling making it a potential therapeutic target for treating pain. However, there is evidence that endocannabinoids have both pro- and anti-nociceptive effects. In previous studies using Hirudo verbana (the medicinal leech), endocannabinoids were found to depress nociceptive synapses, but enhance non-nociceptive synapses. Here we examined whether endocannabinoids have similar bidirectional effects on behavioral responses to nociceptive vs. non-nociceptive stimuli in vivo. Hirudo were injected with either the 2-arachidonoylglycerol (2-AG) or anandamide and tested for changes in response to nociceptive and non-nociceptive stimuli. Both endocannabinoids enhanced responses to non-nociceptive stimuli and reduced responses to nociceptive stimuli. These pro- and anti-nociceptive effects were blocked by co-injection of a TRPV channel inhibitor, which are thought to function as an endocannabinoid receptor. In experiments to determine the effects of endocannabinoids on animals that had undergone injury-induced sensitization, 2-AG and anandamide diminished sensitization to nociceptive stimuli although the effects of 2-AG were longer lasting. Sensitized responses to non-nociceptive stimuli were unaffected 2-AG or anandamide. These results provide evidence that endocannabinoids can have opposing effects on nociceptive vs. non-nociceptive pathways and suggest that cannabinoid-based therapies may be more appropriate for treating pain disorders in which hyperalgesia and not allodynia is the primary symptom.
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Affiliation(s)
- Torrie Summers
- Division of Basic Biomedical Sciences, Center for Brain and Behavior Research, Sanford School of Medicine, University of South Dakota, Vermillion, SD, 57069, USA.,Riot Games, Santa Monica, CA, USA
| | - Brandon Hanten
- Division of Basic Biomedical Sciences, Center for Brain and Behavior Research, Sanford School of Medicine, University of South Dakota, Vermillion, SD, 57069, USA
| | - Warren Peterson
- Division of Basic Biomedical Sciences, Center for Brain and Behavior Research, Sanford School of Medicine, University of South Dakota, Vermillion, SD, 57069, USA
| | - Brian Burrell
- Division of Basic Biomedical Sciences, Center for Brain and Behavior Research, Sanford School of Medicine, University of South Dakota, Vermillion, SD, 57069, USA.
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11
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Dócs K, Mészár Z, Gonda S, Kiss-Szikszai A, Holló K, Antal M, Hegyi Z. The Ratio of 2-AG to Its Isomer 1-AG as an Intrinsic Fine Tuning Mechanism of CB1 Receptor Activation. Front Cell Neurosci 2017; 11:39. [PMID: 28265242 PMCID: PMC5316530 DOI: 10.3389/fncel.2017.00039] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Accepted: 02/07/2017] [Indexed: 12/23/2022] Open
Abstract
Endocannabinoids are pleiotropic lipid messengers that play pro-homeostatic role in cellular physiology by strongly influencing intracellular Ca2+ concentration through the activation of cannabinoid receptors. One of the best-known endocannabinoid ‘2-AG’ is chemically unstable in aqueous solutions, thus its molecular rearrangement, resulting in the formation of 1-AG, may influence 2-AG-mediated signaling depending on the relative concentration and potency of the two isomers. To predict whether this molecular rearrangement may be relevant in physiological processes and in experiments with 2-AG, here we studied if isomerization of 2-AG has an impact on 2-AG-induced, CB1-mediated Ca2+ signaling in vitro. We found that the isomerization-dependent drop in effective 2-AG concentration caused only a weak diminution of Ca2+ signaling in CB1 transfected COS7 cells. We also found that 1-AG induces Ca2+ transients through the activation of CB1, but its working concentration is threefold higher than that of 2-AG. Decreasing the concentration of 2-AG in parallel to the prevention of 1-AG formation by rapid preparation of 2-AG solutions, caused a significant diminution of Ca2+ signals. However, various mixtures of the two isomers in a fix total concentration – mimicking the process of isomerization over time – attenuated the drop in 2-AG potency, resulting in a minor decrease in CB1 mediated Ca2+ transients. Our results indicate that release of 2-AG into aqueous medium is accompanied by its isomerization, resulting in a drop of 2-AG concentration and simultaneous formation of the similarly bioactive isomer 1-AG. Thus, the relative concentration of the two isomers with different potency and efficacy may influence CB1 activation and the consequent biological responses. In addition, our results suggest that 1-AG may play role in stabilizing the strength of cannabinoid signal in case of prolonged 2-AG dependent cannabinoid mechanisms.
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Affiliation(s)
- Klaudia Dócs
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen Debrecen, Hungary
| | - Zoltán Mészár
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen Debrecen, Hungary
| | - Sándor Gonda
- Department of Botany, Faculty of Sciences, University of Debrecen Debrecen, Hungary
| | - Attila Kiss-Szikszai
- Department of Organic Chemistry, Faculty of Sciences, University of Debrecen Debrecen, Hungary
| | - Krisztina Holló
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen Debrecen, Hungary
| | - Miklós Antal
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen Debrecen, Hungary
| | - Zoltán Hegyi
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen Debrecen, Hungary
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Burrell BD. Comparative biology of pain: What invertebrates can tell us about how nociception works. J Neurophysiol 2017; 117:1461-1473. [PMID: 28053241 DOI: 10.1152/jn.00600.2016] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 01/04/2017] [Accepted: 01/04/2017] [Indexed: 12/30/2022] Open
Abstract
The inability to adequately treat chronic pain is a worldwide health care crisis. Pain has both an emotional and a sensory component, and this latter component, nociception, refers specifically to the detection of damaging or potentially damaging stimuli. Nociception represents a critical interaction between an animal and its environment and exhibits considerable evolutionary conservation across species. Using comparative approaches to understand the basic biology of nociception could promote the development of novel therapeutic strategies to treat pain, and studies of nociception in invertebrates can provide especially useful insights toward this goal. Both vertebrates and invertebrates exhibit segregated sensory pathways for nociceptive and nonnociceptive information, injury-induced sensitization to nociceptive and nonnociceptive stimuli, and even similar antinociceptive modulatory processes. In a number of invertebrate species, the central nervous system is understood in considerable detail, and it is often possible to record from and/or manipulate single identifiable neurons through either molecular genetic or physiological approaches. Invertebrates also provide an opportunity to study nociception in an ethologically relevant context that can provide novel insights into the nature of how injury-inducing stimuli produce persistent changes in behavior. Despite these advantages, invertebrates have been underutilized in nociception research. In this review, findings from invertebrate nociception studies are summarized, and proposals for how research using invertebrates can address questions about the fundamental mechanisms of nociception are presented.
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Affiliation(s)
- Brian D Burrell
- Division of Basic Biomedical Sciences, Center for Brain and Behavior Research, Sanford School of Medicine, University of South Dakota, Vermillion, South Dakota
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Carey LM, Slivicki RA, Leishman E, Cornett B, Mackie K, Bradshaw H, Hohmann AG. A pro-nociceptive phenotype unmasked in mice lacking fatty-acid amide hydrolase. Mol Pain 2016; 12:12/0/1744806916649192. [PMID: 27178246 PMCID: PMC4956176 DOI: 10.1177/1744806916649192] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Accepted: 04/15/2016] [Indexed: 11/25/2022] Open
Abstract
Fatty-acid amide hydrolase (FAAH) is the major enzyme responsible for degradation of anandamide, an endocannabinoid. Pharmacological inhibition or genetic deletion of FAAH (FAAH KO) produces antinociception in preclinical pain models that is largely attributed to anandamide-induced activation of cannabinoid receptors. However, FAAH metabolizes a wide range of structurally related, biologically active lipid signaling molecules whose functions remain largely unknown. Some of these endogenous lipids, including anandamide itself, may exert pro-nociceptive effects under certain conditions. In our study, FAAH KO mice exhibited a characteristic analgesic phenotype in the tail flick test and in both formalin and carrageenan models of inflammatory nociception. Nonetheless, intradermal injection of the transient receptor potential channel V1 (TRPV1) agonist capsaicin increased nocifensive behavior as well as mechanical and heat hypersensitivity in FAAH KO relative to wild-type mice. This pro-nociceptive phenotype was accompanied by increases in capsaicin-evoked Fos-like immunoreactive (FLI) cells in spinal dorsal horn regions implicated in nociceptive processing and was attenuated by CB1 (AM251) and TRPV1 (AMG9810) antagonists. When central sensitization was established, FAAH KO mice displayed elevated levels of anandamide, other fatty-acid amides, and endogenous TRPV1 agonists in both paw skin and lumbar spinal cord relative to wild-type mice. Capsaicin decreased spinal cord 2-AG levels and increased arachidonic acid and prostaglandin E2 levels in both spinal cord and paw skin irrespective of genotype. Our studies identify a previously unrecognized pro-nociceptive phenotype in FAAH KO mice that was unmasked by capsaicin challenge. The heightened nociceptive response was mediated by CB1 and TRPV1 receptors and accompanied by enhanced spinal neuronal activation. Moreover, genetic deletion of FAAH has a profound impact on the peripheral and central lipidome. Thus, genetic deletion of FAAH may predispose animals to increased sensitivity to certain types of pain. More work is necessary to determine whether such changes could explain the lack of efficacy of FAAH inhibitors in clinical trials.
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Affiliation(s)
- Lawrence M Carey
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, USA Program in Neuroscience, Indiana University, Bloomington, IN, USA
| | - Richard A Slivicki
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, USA Program in Neuroscience, Indiana University, Bloomington, IN, USA
| | - Emma Leishman
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, USA Program in Neuroscience, Indiana University, Bloomington, IN, USA
| | - Ben Cornett
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, USA
| | - Ken Mackie
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, USA Program in Neuroscience, Indiana University, Bloomington, IN, USA Gill Center for Biomolecular Science, Indiana University, Bloomington, IN, USA
| | - Heather Bradshaw
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, USA Program in Neuroscience, Indiana University, Bloomington, IN, USA
| | - Andrea G Hohmann
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, USA Program in Neuroscience, Indiana University, Bloomington, IN, USA Gill Center for Biomolecular Science, Indiana University, Bloomington, IN, USA
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Cannabinoids to treat spinal cord injury. Prog Neuropsychopharmacol Biol Psychiatry 2016; 64:190-9. [PMID: 25805333 DOI: 10.1016/j.pnpbp.2015.03.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Revised: 03/09/2015] [Accepted: 03/13/2015] [Indexed: 02/06/2023]
Abstract
Spinal cord injury (SCI) is a devastating condition for which there is no standard treatment beyond rehabilitation strategies. In this review, we discuss the current knowledge on the use of cannabinoids to treat this condition. The endocannabinoid system is expressed in the intact spinal cord, and it is dramatically upregulated after lesion. Endogenous activation of this system counteracts secondary damage following SCI, and treatments with endocannabinoids or synthetic cannabinoid receptor agonists promote a better functional outcome in experimental models. The use of cannabinoids in SCI is a new research field and many questions remain open. Here, we discuss caveats and suggest some future directions that may help to understand the role of cannabinoids in SCI and how to take advantage of this system to regain functions after spinal cord damage.
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da Silva JA, Biagioni AF, Almada RC, de Souza Crippa JA, Cecílio Hallak JE, Zuardi AW, Coimbra NC. Dissociation between the panicolytic effect of cannabidiol microinjected into the substantia nigra, pars reticulata, and fear-induced antinociception elicited by bicuculline administration in deep layers of the superior colliculus: The role of CB1-cannabinoid receptor in the ventral mesencephalon. Eur J Pharmacol 2015; 758:153-63. [PMID: 25841876 DOI: 10.1016/j.ejphar.2015.03.051] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Revised: 03/11/2015] [Accepted: 03/17/2015] [Indexed: 01/17/2023]
Abstract
Many studies suggest that the substantia nigra, pars reticulata (SNpr), a tegmental mesencephalic structure rich in γ-aminobutyric acid (GABA)- and cannabinoid receptor-containing neurons, is involved in the complex control of defensive responses through the neostriatum-nigral disinhibitory and nigro-tectal inhibitory GABAergic pathways during imminently dangerous situations. The aim of the present work was to investigate the role played by CB1-cannabinoid receptor of GABAergic pathways terminal boutons in the SNpr or of SNpr-endocannabinoid receptor-containing interneurons on the effect of intra-nigral microinjections of cannabidiol in the activity of nigro-tectal inhibitory pathways. GABAA receptor blockade in the deep layers of the superior colliculus (dlSC) elicited vigorous defensive behaviour. This explosive escape behaviour was followed by significant antinociception. Cannabidiol microinjection into the SNpr had a clear anti-aversive effect, decreasing the duration of defensive alertness, the frequency and duration of defensive immobility, and the frequency and duration of explosive escape behaviour, expressed by running and jumps, elicited by transitory GABAergic dysfunction in dlSC. However, the innate fear induced-antinociception was not significantly changed. The blockade of CB1 endocannabinoid receptor in the SNpr decreased the anti-aversive effect of canabidiol based on the frequency and duration of defensive immobility, the frequency of escape expressed by running, and both the frequency and duration of escape expressed by jumps. These findings suggest a CB1 mediated endocannabinoid signalling in cannabidiol modulation of panic-like defensive behaviour, but not of innate fear-induced antinociception evoked by GABAA receptor blockade with bicuculline microinjection into the superior colliculus, with a putative activity in nigro-collicular GABAergic pathways.
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Affiliation(s)
- Juliana Almeida da Silva
- Laboratory of Neuroanatomy and Neuropsychobiology, Department of Pharmacology, Ribeirão Preto School of Medicine of the University of São Paulo (FMRP-USP), Av Bandeirantes, 3900, Ribeirão Preto 14049-900, São Paulo, Brazil; Behavioural Neurosciences Institute (INeC), Av. do Café, 2450, Monte Alegre, Ribeirão Preto 14050-220, São Paulo, Brazil
| | - Audrey Francisco Biagioni
- Laboratory of Neuroanatomy and Neuropsychobiology, Department of Pharmacology, Ribeirão Preto School of Medicine of the University of São Paulo (FMRP-USP), Av Bandeirantes, 3900, Ribeirão Preto 14049-900, São Paulo, Brazil
| | - Rafael Carvalho Almada
- Laboratory of Neuroanatomy and Neuropsychobiology, Department of Pharmacology, Ribeirão Preto School of Medicine of the University of São Paulo (FMRP-USP), Av Bandeirantes, 3900, Ribeirão Preto 14049-900, São Paulo, Brazil; Behavioural Neurosciences Institute (INeC), Av. do Café, 2450, Monte Alegre, Ribeirão Preto 14050-220, São Paulo, Brazil
| | - José Alexandre de Souza Crippa
- Department of Neurosciences and Behavioural Sciences, Division of Psychiatry, Ribeirão Preto School of Medicine of the University of São Paulo (FMRP-USP), Av. dos Bandeirantes, 3900, Ribeirão Preto 14049-900, São Paulo, Brazil
| | - Jaime Eduardo Cecílio Hallak
- Department of Neurosciences and Behavioural Sciences, Division of Psychiatry, Ribeirão Preto School of Medicine of the University of São Paulo (FMRP-USP), Av. dos Bandeirantes, 3900, Ribeirão Preto 14049-900, São Paulo, Brazil
| | - Antônio Waldo Zuardi
- Department of Neurosciences and Behavioural Sciences, Division of Psychiatry, Ribeirão Preto School of Medicine of the University of São Paulo (FMRP-USP), Av. dos Bandeirantes, 3900, Ribeirão Preto 14049-900, São Paulo, Brazil
| | - Norberto Cysne Coimbra
- Laboratory of Neuroanatomy and Neuropsychobiology, Department of Pharmacology, Ribeirão Preto School of Medicine of the University of São Paulo (FMRP-USP), Av Bandeirantes, 3900, Ribeirão Preto 14049-900, São Paulo, Brazil; Behavioural Neurosciences Institute (INeC), Av. do Café, 2450, Monte Alegre, Ribeirão Preto 14050-220, São Paulo, Brazil; Neurobiology of Emotions Research Centre (NAP-USP-NuPNE), Ribeirão Preto School of Medicine of the University of São Paulo (FMRP-USP), Av. dos Bandeirantes, 3900, Ribeirão Preto, São Paulo 14049-900, São Paulo, Brazil.
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16
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The Potential of Inhibitors of Endocannabinoid Metabolism for Drug Development: A Critical Review. Handb Exp Pharmacol 2015; 231:95-128. [PMID: 26408159 DOI: 10.1007/978-3-319-20825-1_4] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The endocannabinoids anandamide and 2-arachidonoylglycerol are metabolised by both hydrolytic enzymes (primarily fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MGL)) and oxygenating enzymes (e.g. cyclooxygenase-2, COX-2). In the present article, the in vivo data for compounds inhibiting endocannabinoid metabolism have been reviewed, focussing on inflammation and pain. Potential reasons for the failure of an FAAH inhibitor in a clinical trial in patients with osteoarthritic pain are discussed. It is concluded that there is a continued potential for compounds inhibiting endocannabinoid metabolism in terms of drug development, but that it is wise not to be unrealistic in terms of expectations of success.
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Horváth E, Woodhams SG, Nyilas R, Henstridge CM, Kano M, Sakimura K, Watanabe M, Katona I. Heterogeneous presynaptic distribution of monoacylglycerol lipase, a multipotent regulator of nociceptive circuits in the mouse spinal cord. Eur J Neurosci 2014; 39:419-34. [PMID: 24494682 PMCID: PMC3979158 DOI: 10.1111/ejn.12470] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Revised: 11/29/2013] [Accepted: 12/02/2013] [Indexed: 01/10/2023]
Abstract
Monoacylglycerol lipase (MGL) is a multifunctional serine hydrolase, which terminates anti-nociceptive endocannabinoid signaling and promotes pro-nociceptive prostaglandin signaling. Accordingly, both acute nociception and its sensitization in chronic pain models are prevented by systemic or focal spinal inhibition of MGL activity. Despite its analgesic potential, the neurobiological substrates of beneficial MGL blockade have remained unexplored. Therefore, we examined the regional, cellular and subcellular distribution of MGL in spinal circuits involved in nociceptive processing. All immunohistochemical findings obtained with light, confocal or electron microscopy were validated in MGL-knockout mice. Immunoperoxidase staining revealed a highly concentrated accumulation of MGL in the dorsal horn, especially in superficial layers. Further electron microscopic analysis uncovered that the majority of MGL-immunolabeling is found in axon terminals forming either asymmetric glutamatergic or symmetric γ-aminobutyric acid/glycinergic synapses in laminae I/IIo. In line with this presynaptic localization, analysis of double-immunofluorescence staining by confocal microscopy showed that MGL colocalizes with neurochemical markers of peptidergic and non-peptidergic nociceptive terminals, and also with markers of local excitatory or inhibitory interneurons. Interestingly, the ratio of MGL-immunolabeling was highest in calcitonin gene-related peptide-positive peptidergic primary afferents, and the staining intensity of nociceptive terminals was significantly reduced in MGL-knockout mice. These observations highlight the spinal nociceptor synapse as a potential anatomical site for the analgesic effects of MGL blockade. Moreover, the presence of MGL in additional terminal types raises the possibility that MGL may play distinct regulatory roles in synaptic endocannabinoid or prostaglandin signaling according to its different cellular locations in the dorsal horn pain circuitry.
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Affiliation(s)
- Eszter Horváth
- Momentum Laboratory of Molecular Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Szigony utca 43., H-1083, Budapest, Hungary
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Raehal KM, Bohn LM. β-arrestins: regulatory role and therapeutic potential in opioid and cannabinoid receptor-mediated analgesia. Handb Exp Pharmacol 2014; 219:427-43. [PMID: 24292843 PMCID: PMC4804701 DOI: 10.1007/978-3-642-41199-1_22] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Pain is a complex disorder with neurochemical and psychological components contributing to the severity, the persistence, and the difficulty in adequately treating the condition. Opioid and cannabinoids are two classes of analgesics that have been used to treat pain for centuries and are arguably the oldest of "pharmacological" interventions used by man. Unfortunately, they also produce several adverse side effects that can complicate pain management. Opioids and cannabinoids act at G protein-coupled receptors (GPCRs), and much of their effects are mediated by the mu-opioid receptor (MOR) and cannabinoid CB1 receptor (CB1R), respectively. These receptors couple to intracellular second messengers and regulatory proteins to impart their biological effects. In this chapter, we review the role of the intracellular regulatory proteins, β-arrestins, in modulating MOR and CB1R and how they influence the analgesic and side-effect profiles of opioid and cannabinoid drugs in vivo. This review of the literature suggests that the development of opioid and cannabinoid agonists that bias MOR and CB1R toward G protein signaling cascades and away from β-arrestin interactions may provide a novel mechanism by which to produce analgesia with less severe adverse effects.
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MESH Headings
- Analgesics/adverse effects
- Analgesics/pharmacology
- Analgesics, Opioid/adverse effects
- Analgesics, Opioid/pharmacology
- Animals
- Arrestins/metabolism
- Cannabinoids/adverse effects
- Cannabinoids/pharmacology
- Drug Design
- Humans
- Pain/drug therapy
- Pain/physiopathology
- Receptor, Cannabinoid, CB1/drug effects
- Receptor, Cannabinoid, CB1/metabolism
- Receptors, G-Protein-Coupled/drug effects
- Receptors, G-Protein-Coupled/metabolism
- Receptors, Opioid, mu/drug effects
- Receptors, Opioid, mu/metabolism
- beta-Arrestins
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Affiliation(s)
- Kirsten M Raehal
- The Scripps Research Institute, 130 Scripps Way #2A2, Jupiter, FL, 33458, USA,
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19
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Abstract
The endocannabinoid (EC) system consists of two main receptors: cannabinoid type 1 receptor cannabinoid receptors are found in both the central nervous system (CNS) and periphery, whereas the cannabinoid type 2 receptor cannabinoid receptor is found principally in the immune system and to a lesser extent in the CNS. The EC family consists of two classes of well characterised ligands; the N-acyl ethanolamines, such as N-arachidonoyl ethanolamide or anandamide (AEA), and the monoacylglycerols, such as 2-arachidonoyl glycerol. The various synthetic and catabolic pathways for these enzymes have been (with the exception of AEA synthesis) elucidated. To date, much work has examined the role of EC in nociceptive processing and the potential of targeting the EC system to produce analgesia. Cannabinoid receptors and ligands are found at almost every level of the pain pathway from peripheral sites, such as peripheral nerves and immune cells, to central integration sites such as the spinal cord, and higher brain regions such as the periaqueductal grey and the rostral ventrolateral medulla associated with descending control of pain. EC have been shown to induce analgesia in preclinical models of acute nociception and chronic pain states. The purpose of this review is to critically evaluate the evidence for the role of EC in the pain pathway and the therapeutic potential of EC to produce analgesia. We also review the present clinical work conducted with EC, and examine whether targeting the EC system might offer a novel target for analgesics, and also potentially disease-modifying interventions for pathophysiological pain states.
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Forced Swimming Stress-Related Hypoalgesia:Nondependence on the Histaminergic Mechanisms. NEUROPHYSIOLOGY+ 2013. [DOI: 10.1007/s11062-013-9378-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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21
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Olango W, Géranton S, Roche M, Hunt S, Finn D. Novel molecular correlates of endocannabinoid-mediated fear-conditioned analgesia in rats. Eur J Pain 2013; 18:182-91. [DOI: 10.1002/j.1532-2149.2013.00369.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/20/2013] [Indexed: 11/12/2022]
Affiliation(s)
- W.M. Olango
- Pharmacology and Therapeutics; School of Medicine; National University of Ireland Galway; Ireland
- NCBES Neuroscience Cluster; National University of Ireland Galway; Ireland
- Centre for Pain Research; National University of Ireland Galway; Ireland
| | - S.M. Géranton
- Department of Cell and Developmental Biology; University College London; UK
| | - M. Roche
- Physiology; School of Medicine; National University of Ireland Galway; Ireland
- NCBES Neuroscience Cluster; National University of Ireland Galway; Ireland
- Centre for Pain Research; National University of Ireland Galway; Ireland
| | - S.P. Hunt
- Department of Cell and Developmental Biology; University College London; UK
| | - D.P. Finn
- Pharmacology and Therapeutics; School of Medicine; National University of Ireland Galway; Ireland
- NCBES Neuroscience Cluster; National University of Ireland Galway; Ireland
- Centre for Pain Research; National University of Ireland Galway; Ireland
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Woodhams SG, Wong A, Barrett DA, Bennett AJ, Chapman V, Alexander SPH. Spinal administration of the monoacylglycerol lipase inhibitor JZL184 produces robust inhibitory effects on nociceptive processing and the development of central sensitization in the rat. Br J Pharmacol 2013; 167:1609-19. [PMID: 22924700 DOI: 10.1111/j.1476-5381.2012.02179.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Revised: 08/07/2012] [Accepted: 08/13/2012] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND AND PURPOSE The cannabinoid receptor-mediated analgesic effects of 2-arachidonoylglycerol (2-AG) are limited by monoacylglycerol lipase (MAGL). 4-nitrophenyl 4-[bis (1,3-benzodioxol-5-yl) (hydroxy) methyl] piperidine-1-carboxylate (JZL184) is a potent inhibitor of MAGL in the mouse, though potency is reportedly reduced in the rat. Here we have assessed the effects of spinal inhibition of MAGL with JZL184 on nociceptive processing in rats. EXPERIMENTAL APPROACH In vivo spinal electrophysiological assays in anaesthetized rats were used to determine the effects of spinal administration of JZL184 on spinal nociceptive processing in the presence and absence of hindpaw inflammation. Contributions of CB(1) receptors to these effects was assessed with AM251. Inhibition of 2-oleoylglycerol hydrolytic activity and alterations of 2-AG in the spinal cord after JZL 184 were also assessed. KEY RESULTS Spinal JZL184 dose-dependently inhibited mechanically evoked responses of wide dynamic range (WDR) neurones in naïve anaesthetized rats, in part via the CB(1) receptor. A single spinal administration of JZL184 abolished inflammation-induced expansion of the receptive fields of spinal WDR neurones. However, neither spinal nor systemic JZL184 altered levels of 2-AG, or 2-oleoylglycerol hydrolytic activity in the spinal cord, although JZL184 displayed robust inhibition of MAGL when incubated with spinal cord tissue in vitro. CONCLUSIONS AND IMPLICATIONS JZL184 exerted robust anti-nociceptive effects at the level of the spinal cord in vivo and inhibited rat spinal cord MAGL activity in vitro. The discordance between in vivo and in vitro assays suggests that localized sites of action of JZL184 produce these profound functional inhibitory effects. LINKED ARTICLES This article is part of a themed section on Cannabinoids. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.167.issue-8.
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Affiliation(s)
- S G Woodhams
- School of Biomedical Sciences, University of Nottingham Medical School, Nottingham, UK
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23
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Gilmore AJ, Heblinski M, Reynolds A, Kassiou M, Connor M. Inhibition of human recombinant T-type calcium channels by N-arachidonoyl 5-HT. Br J Pharmacol 2013; 167:1076-88. [PMID: 22624680 DOI: 10.1111/j.1476-5381.2012.02047.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
Abstract
BACKGROUND AND PURPOSE N-arachidonoyl 5-HT (NA-5HT) has anti-nociceptive effects reported to be mediated by inhibitory actions at the transient receptor potential vanilloid receptor 1 (TRPV1) and fatty acid amide hydrolase (FAAH). Anandamide and N-arachidonoyl dopamine (NA-DA), endocannabinoids that activate TRPV1 or are metabolized by FAAH, also inhibit T-type calcium channels (I(Ca) ). T-type I(Ca) are expressed by many excitable cells, including neurons involved in pain detection and processing. We sought to determine whether NA-5HT also modulates T-type I(Ca) . EXPERIMENTAL APPROACH Human recombinant T-type I(Ca) (Ca(V) 3 channels) expressed in HEK 293 cells were examined using standard whole-cell voltage-clamp electrophysiology techniques. KEY RESULTS NA-5HT completely inhibited Ca(V) 3 channels with a rank order of potency (pEC(50) ) of Ca(V) 3.1 (7.4) > Ca(V) 3.3 (6.8) ≥ Ca(V) 3.2 (6.6). The effects of NA-5HT were voltage-dependent, and it produced significant hyperpolarizing shifts in Ca(V) 3 steady-state inactivation relationships. NA-5HT selectively affected Ca(V) 3.3 channel kinetics. CONCLUSIONS AND IMPLICATIONS NA-5HT increases the steady-state inactivation of Ca(V) 3 channels, reducing the number of channels available to open during depolarization. These effects occur at NA-5HT concentrations at or below those at which NA-5HT affects TRPV1 receptors and FAAH. NA-5HT is one of the most potent inhibitors of T-type I(Ca) described to date, and it is likely to exert some of its biological effects, including anti-nociception, via inhibition of these channels.
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Affiliation(s)
- Andrew J Gilmore
- Pain Management Research Institute, Kolling Institute, University of Sydney at Royal North Hospital St Leonards, Australia
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24
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Starowicz K, Di Marzo V. Non-psychotropic analgesic drugs from the endocannabinoid system: "magic bullet" or "multiple-target" strategies? Eur J Pharmacol 2013; 716:41-53. [PMID: 23500197 DOI: 10.1016/j.ejphar.2013.01.075] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Revised: 01/21/2013] [Accepted: 01/29/2013] [Indexed: 02/06/2023]
Abstract
The exploitation of preparations of Cannabis sativa to combat pain seems to date back to time immemorial, although their psychotropic effects, which are at the bases of their recreational use and limit their therapeutic use, are at least as ancient. Indeed, it has always been different to tease apart the unwanted central effects from the therapeutic benefits of Δ⁹-tetrahydrocannabinol (THC), the main psychotropic component of cannabis. The discovery of the cannabinoid receptors and of their endogenous ligands, the endocannabinoids, which, unlike THC, play a pro-homeostatic function in a tissue- and time-selective manner, offered the opportunity to develop new analgesics from synthetic inhibitors of endocannabinoid inactivation. The advantages of this approach over direct activation of cannabinoid receptors as a therapeutic strategy against neuropathic and inflammatory pain are discussed here along with its potential complications. These latter have been such that clinical success has been achieved so far more rapidly with naturally occurring THC or endocannabinoid structural analogues acting at a plethora of cannabinoid-related and -unrelated molecular targets, than with selective inhibitors of endocannabinoid enzymatic hydrolysis, thus leading to revisit the potential usefulness of "multi-target" versus "magic bullet" compounds as new analgesics.
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Affiliation(s)
- Katarzyna Starowicz
- Department of Pain Pharmacolgy, Institute of Pharmacology Polish Academy of Sciences, 12 Smetna str, 31-343 Krakow, Poland.
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25
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Gregg LC, Jung KM, Spradley JM, Nyilas R, Suplita RL, Zimmer A, Watanabe M, Mackie K, Katona I, Piomelli D, Hohmann AG. Activation of type 5 metabotropic glutamate receptors and diacylglycerol lipase-α initiates 2-arachidonoylglycerol formation and endocannabinoid-mediated analgesia. J Neurosci 2012; 32:9457-68. [PMID: 22787031 PMCID: PMC3652685 DOI: 10.1523/jneurosci.0013-12.2012] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2011] [Revised: 05/11/2012] [Accepted: 05/17/2012] [Indexed: 11/21/2022] Open
Abstract
Acute stress reduces pain sensitivity by engaging an endocannabinoid signaling circuit in the midbrain. The neural mechanisms governing this process and molecular identity of the endocannabinoid substance(s) involved are unknown. We combined behavior, pharmacology, immunohistochemistry, RNA interference, quantitative RT-PCR, enzyme assays, and lipidomic analyses of endocannabinoid content to uncover the role of the endocannabinoid 2-arachidonoyl-sn-glycerol (2-AG) in controlling pain sensitivity in vivo. Here, we show that footshock stress produces antinociception in rats by activating type 5 metabotropic glutamate receptors (mGlu(5)) in the dorsolateral periaqueductal gray (dlPAG) and mobilizing 2-AG. Stimulation of mGlu(5) in the dlPAG with DHPG [(S)-3,5-dihydroxyphenylglycine] triggered 2-AG formation and enhanced stress-dependent antinociception through a mechanism dependent upon both postsynaptic diacylglycerol lipase (DGL) activity, which releases 2-AG, and presynaptic CB(1) cannabinoid receptors. Pharmacological blockade of DGL activity in the dlPAG with RHC80267 [1,6-bis(cyclohexyloximinocarbonylamino)hexane] and (-)-tetrahydrolipstatin (THL), which inhibit activity of DGL-α and DGL-β isoforms, suppressed stress-induced antinociception. Inhibition of DGL activity in the dlPAG with THL selectively decreased accumulation of 2-AG without altering levels of anandamide. The putative 2-AG-synthesizing enzyme DGL-α colocalized with mGlu(5) at postsynaptic sites of the dlPAG, whereas CB(1) was confined to presynaptic terminals, consistent with a role for 2-AG as a retrograde signaling messenger. Finally, virally mediated silencing of DGL-α, but not DGL-β, transcription in the dlPAG mimicked effects of DGL inhibition in suppressing both endocannabinoid-mediated stress antinociception and 2-AG formation. The results indicate that activation of the postsynaptic mGlu(5)-DGL-α cascade triggers retrograde 2-AG signaling in vivo. This pathway is required for endocannabinoid-mediated stress-induced analgesia.
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Affiliation(s)
- Laura C. Gregg
- Neuroscience Program, Biomedical and Health Sciences Institute, and
| | - Kwang-Mook Jung
- Department of Pharmacology, University of California, Irvine, Irvine, California 92697
| | | | - Rita Nyilas
- Institute of Experimental Medicine, Hungarian Academy of Sciences, H-1083 Budapest, Hungary
| | - Richard L. Suplita
- Psychology Department, University of Georgia, Athens, Georgia 30602-3013
| | - Andreas Zimmer
- Insitute of Molecular Psychiatry, University of Bonn, 53105 Bonn, Germany
| | - Masahiko Watanabe
- Department of Anatomy, Hokkaido University School of Medicine, Sapporo 060-8638, Japan
| | - Ken Mackie
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana 47405-2204, and
| | - István Katona
- Institute of Experimental Medicine, Hungarian Academy of Sciences, H-1083 Budapest, Hungary
| | - Daniele Piomelli
- Department of Pharmacology, University of California, Irvine, Irvine, California 92697
- Unit of Drug Discovery and Development, Italian Institute of Technology, 16163 Genoa, Italy
| | - Andrea G. Hohmann
- Neuroscience Program, Biomedical and Health Sciences Institute, and
- Psychology Department, University of Georgia, Athens, Georgia 30602-3013
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana 47405-2204, and
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Dogrul A, Seyrek M, Yalcin B, Ulugol A. Involvement of descending serotonergic and noradrenergic pathways in CB1 receptor-mediated antinociception. Prog Neuropsychopharmacol Biol Psychiatry 2012; 38:97-105. [PMID: 22300745 DOI: 10.1016/j.pnpbp.2012.01.007] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2011] [Revised: 01/03/2012] [Accepted: 01/15/2012] [Indexed: 12/18/2022]
Abstract
Cannabinoids produce antinociceptive and antihyperalgesic effects mainly through activation of the inhibitory CB1 receptors. The demonstration that antinociceptive effects of systemic cannabinoids are significantly diminished following surgical dorsolateral funiculus lesion provides evidence that supraspinal sites and descending pain modulatory pathways play crucial roles in systemic cannabinoid analgesia. In this review, we will firstly provide a background, brief overview of descending modulatory pathways followed by descending pathways implicated in cannabinoid analgesia. We will then describe the recent evidence of the involvement of descending serotonergic and noradrenergic pathways in CB1 receptor-mediated antinociception. This review will provide evidences that systemically administered cannabinoids reinforce the descending serotonergic and noradrenergic pathways to produce acute antinociceptive effects via spinal 5-HT7, 5-HT2A and alpha-2 adrenoceptors activation.
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Affiliation(s)
- Ahmet Dogrul
- Department of Medical Pharmacology, Gulhane Military Academy of Medicine, Ankara, Turkey.
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27
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Veress G, Meszar Z, Muszil D, Avelino A, Matesz K, Mackie K, Nagy I. Characterisation of cannabinoid 1 receptor expression in the perikarya, and peripheral and spinal processes of primary sensory neurons. Brain Struct Funct 2012; 218:733-50. [PMID: 22618437 DOI: 10.1007/s00429-012-0425-2] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2011] [Accepted: 04/25/2012] [Indexed: 11/24/2022]
Abstract
The cannabinoid 1 (CB1) receptor is expressed by a sub-population of primary sensory neurons. However, data on the neurochemical identity of the CB1 receptor-expressing cells, and CB1 receptor expression by the peripheral and central terminals of these neurons are inconsistent and limited. We characterised CB1 receptor expression in dorsal root ganglia (DRG) and spinal cord at the lumbar 4-5 level, as well as in the urinary bladder and glabrous skin of the hindpaw. About 1/3 of DRG neurons exhibited immunopositivity for the CB1 receptor, the majority of which showed positivity for the nociceptive markers calcitonin gene-related peptide (CGRP) or/and Griffonia (bandeiraea) simplicifolia IB4 isolectin-binding. Virtually all CB1 receptor-immunostained fibres showed immunopositivity for CGRP in the skin, while very few did in the urinary bladder. No CB1 receptor-immunopositive nerve fibres were IB4 positive in either peripheral tissue. Spinal laminae I and II-outer showed the highest density of CB1 receptor-immunopositive punctae, the majority of which showed positivity for CGRP or/and IB4 binding. These data indicate that a major sub-population of nociceptive primary sensory neurons expresses CB1 receptors that are transported to both peripheral and central terminals of these cells. Therefore, the present data suggest that manipulation of endogenous CB1 receptor agonist levels in these areas may significantly reduce nociceptive input into the spinal cord.
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MESH Headings
- Analysis of Variance
- Animals
- Calcitonin Gene-Related Peptide/metabolism
- Cholera Toxin/metabolism
- Epidermal Cells
- Ganglia, Spinal/cytology
- Hippocampus/cytology
- Hippocampus/metabolism
- Horseradish Peroxidase/metabolism
- Keratinocytes/metabolism
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Microscopy, Confocal
- Nerve Fibers/metabolism
- RNA, Messenger/metabolism
- Rats
- Rats, Inbred WKY
- Receptor, Cannabinoid, CB1/deficiency
- Receptor, Cannabinoid, CB1/metabolism
- Sensory Receptor Cells/metabolism
- Spinal Cord/cytology
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Affiliation(s)
- Gabor Veress
- Pathology Unit, Kaposi Mór Teaching Hospital, Kaposvár H7400, Hungary
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28
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Petrovszki Z, Kovacs G, Tömböly C, Benedek G, Horvath G. The effects of peptide and lipid endocannabinoids on arthritic pain at the spinal level. Anesth Analg 2012; 114:1346-52. [PMID: 22451592 DOI: 10.1213/ane.0b013e31824c4eeb] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
BACKGROUND Hemopressin, a nonapeptide (PVNFKFLSH: HP) derived from the α chain of hemoglobin was shown to interact specifically with brain cannabinoid CB(1) receptors. Therefore, it seems to be the only peptide structure with cannabinoid activities. Our goal in this study was to further characterize this peptide and to clarify the antinociceptive potency of the polyunsaturated fatty acid derivates, 2-arachidonoyl-glycerol (2-AG) and anandamide, by investigating their effects on mechanical allodynia at the spinal level. METHODS HP was prepared on solid phase by in situ neutralization. After chronic intrathecal catheterization, mechanical hypersensitivity was produced in male Wistar rats by injection of carrageenan (300 μg/30 μL) into the tibiotarsal joint of one of the hind legs. Three hours after carrageenan administration, the ligands were administered intrathecally. The mechanical threshold was assessed using a dynamic aesthesiometer. RESULTS 2-AG (1-200 μg) and anandamide (10-200 μg) decreased carrageenan-induced mechanical allodynia in a dose-dependent manner, whereas HP had no antinociceptive effect in a wide dose range (0.3-30 μg). The effect of 2-AG was prevented by the CB(1) receptor antagonist AM 251, but not by the CB(2) antagonist SSR144528-2. HP (3 and 30 μg) also inhibited the effect of 2-AG. None of the ligands influenced the degree of edema. CONCLUSIONS HP posttreatment had no effect on mechanical allodynia, whereas spinally injected 2-AG and anandamide were potent drugs.
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Affiliation(s)
- Zita Petrovszki
- Department of Physiology, Faculty of Medicine, University of Szeged, Szeged, Hungary
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29
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Zoerner AA, Gutzki FM, Batkai S, May M, Rakers C, Engeli S, Jordan J, Tsikas D. Quantification of endocannabinoids in biological systems by chromatography and mass spectrometry: A comprehensive review from an analytical and biological perspective. Biochim Biophys Acta Mol Cell Biol Lipids 2011; 1811:706-23. [DOI: 10.1016/j.bbalip.2011.08.004] [Citation(s) in RCA: 120] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2011] [Revised: 08/11/2011] [Accepted: 08/12/2011] [Indexed: 11/26/2022]
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30
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Molecular sites for the positive allosteric modulation of glycine receptors by endocannabinoids. PLoS One 2011; 6:e23886. [PMID: 21901142 PMCID: PMC3162021 DOI: 10.1371/journal.pone.0023886] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2011] [Accepted: 07/29/2011] [Indexed: 11/19/2022] Open
Abstract
Glycine receptors (GlyRs) are transmitter-gated anion channels of the Cys-loop superfamily which mediate synaptic inhibition at spinal and selected supraspinal sites. Although they serve pivotal functions in motor control and sensory processing, they have yet to be exploited as drug targets partly because of hitherto limited possibilities for allosteric control. Endocannabinoids (ECs) have recently been characterized as direct allosteric GlyR modulators, but the underlying molecular sites have remained unknown. Here, we show that chemically neutral ECs (e.g. anandamide, AEA) are positive modulators of α1, α2 and α3 GlyRs, whereas acidic ECs (e.g. N-arachidonoyl-glycine; NA-Gly) potentiate α1 GlyRs but inhibit α2 and α3. This subunit-specificity allowed us to identify the underlying molecular sites through analysis of chimeric and mutant receptors. We found that alanine 52 in extracellular loop 2, glycine 254 in transmembrane (TM) region 2 and intracellular lysine 385 determine the positive modulation of α1 GlyRs by NA-Gly. Successive substitution of non-conserved extracellular and TM residues in α2 converted NA-Gly-mediated inhibition into potentiation. Conversely, mutation of the conserved lysine within the intracellular loop between TM3 and TM4 attenuated NA-Gly-mediated potentiation of α1 GlyRs, without affecting inhibition of α2 and α3. Notably, this mutation reduced modulation by AEA of all three GlyRs. These results define molecular sites for allosteric control of GlyRs by ECs and reveal an unrecognized function for the TM3-4 intracellular loop in the allosteric modulation of Cys-loop ion channels. The identification of these sites may help to understand the physiological role of this modulation and facilitate the development of novel therapeutic approaches to diseases such as spasticity, startle disease and possibly chronic pain.
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31
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Dimitrov EL, Petrus E, Usdin TB. Tuberoinfundibular peptide of 39 residues (TIP39) signaling modulates acute and tonic nociception. Exp Neurol 2010; 226:68-83. [PMID: 20696160 DOI: 10.1016/j.expneurol.2010.08.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Revised: 07/26/2010] [Accepted: 08/02/2010] [Indexed: 11/19/2022]
Abstract
Tuberoinfundibular peptide of 39 residues (TIP39) synthesizing neurons at the caudal border of the thalamus and in the lateral pons project to areas rich in its receptor, the parathyroid hormone 2 receptor (PTH2R). These areas include many involved in processing nociceptive information. Here we examined the potential role of TIP39 signaling in nociception using a PTH2R antagonist (HYWH) and mice with deletion of TIP39's coding sequence or PTH2R null mutation. Intracerebroventricular (icv) infusion of HYWH significantly inhibited nociceptive responses in tail-flick and hot-plate tests and attenuated the nociceptive response to hindpaw formalin injection. TIP39-KO and PTH2R-KO had increased response latency in the 55°C hot-plate test and reduced responses in the hindpaw formalin test. The tail-flick test was not affected in either KO line. Thermal hypoalgesia in KO mice was dose-dependently reversed by systemic administration of the cannabinoid receptor 1 (CB1) antagonist rimonabant, which did not affect nociception in wild-type (WT). Systemic administration of the cannabinoid agonist CP 55,940 did not affect nociception in KO mice at a dose effective in WT. WT mice administered HYWH icv, and both KOs, had significantly increased stress-induced analgesia (SIA). Rimonabant blocked the increased SIA in TIP39-KO, PTH2R-KO or after HYWH infusion. CB1 and FAAH mRNA were decreased and increased, respectively, in the basolateral amygdala of TIP39-KO mice. These data suggest that TIP39 signaling modulates nociception, very likely by inhibiting endocannabinoid circuitry at a supraspinal level. We infer a new central mechanism for endocannabinoid regulation, via TIP39 acting on the PTH2R in discrete brain regions.
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MESH Headings
- Amidohydrolases/metabolism
- Animals
- Cannabinoid Receptor Modulators/metabolism
- Formaldehyde
- In Situ Hybridization
- Injections, Intraventricular
- Injections, Spinal
- Male
- Mice
- Mice, Knockout
- Naloxone/pharmacology
- Narcotic Antagonists/pharmacology
- Neuropeptides/administration & dosage
- Neuropeptides/pharmacology
- Nociceptors/drug effects
- Nociceptors/physiology
- Pain/pathology
- Pain/physiopathology
- Pain Measurement/drug effects
- Piperidines/pharmacology
- Pyrazoles/pharmacology
- RNA, Messenger/biosynthesis
- RNA, Messenger/genetics
- Receptor, Cannabinoid, CB1/antagonists & inhibitors
- Receptor, Cannabinoid, CB1/biosynthesis
- Receptor, Parathyroid Hormone, Type 2/biosynthesis
- Receptor, Parathyroid Hormone, Type 2/genetics
- Rimonabant
- Signal Transduction/physiology
- Stress, Psychological/psychology
- Synapses/physiology
- Vesicular Glutamate Transport Protein 2/biosynthesis
- Vesicular Glutamate Transport Protein 2/genetics
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Affiliation(s)
- Eugene L Dimitrov
- Section on Fundamental Neuroscience, National Institute of Mental Health, 35 Convent Drive, Room 1B-213, Bethesda, MD 20892, USA.
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32
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Endocannabinoid-mediated modulation of stress responses: Physiological and pathophysiological significance. Immunobiology 2010; 215:629-46. [DOI: 10.1016/j.imbio.2009.05.011] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2009] [Revised: 05/30/2009] [Accepted: 05/30/2009] [Indexed: 12/18/2022]
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33
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Greco R, Gasperi V, Sandrini G, Bagetta G, Nappi G, Maccarrone M, Tassorelli C. Alterations of the endocannabinoid system in an animal model of migraine: evaluation in cerebral areas of rat. Cephalalgia 2010; 30:296-302. [PMID: 19515121 DOI: 10.1111/j.1468-2982.2009.01924.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Endocannabinoids are involved in the modulation of pain and hyperalgesia. In this study we investigated the role of the endocannabinoid system in the migraine model based on nitroglycerin-induced hyperalgesia in the rat. Male rats were injected with nitroglycerin (10 mg/kg, i.p.) or vehicle and sacrificed 4 h later. The medulla, the mesencephalon and the hypothalamus were dissected out and utilized for the evaluation of activity of fatty acid amide hydrolase (that degrades the endocannabinoid anandamide), monoacylglycerol lipase (that degrades the endocannabinoid 2-arachidonoylglycerol), and binding sites specific for cannabinoid (CB) receptors. The findings obtained show that nitroglycerin-induced hyperalgesia is associated with increased activity of both hydrolases and increased density of CB binding sites in the mesencephalon. In the hypothalamus we observed an increase in the activity of fatty acid amide hydrolase associated with an increase in density of CB binding sites, while in the medulla only the activity of fatty acid amide hydrolase was increased. Anandamide also proved effective in preventing nitroglycerin-induced activation (c-Fos) of neurons in the nucleus trigeminalis caudalis. These data strongly support the involvement of the endocannabinoid system in the modulation of nitroglycerin-induced hyperalgesia, and, possibly, in the pathophysiological mechanisms of migraine.
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Affiliation(s)
- R Greco
- IRCCS Neurological Institute C Mondino Foundation, University of Pavia, Pavia, Italy
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34
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Bertrand T, Augé F, Houtmann J, Rak A, Vallée F, Mikol V, Berne PF, Michot N, Cheuret D, Hoornaert C, Mathieu M. Structural basis for human monoglyceride lipase inhibition. J Mol Biol 2009; 396:663-73. [PMID: 19962385 DOI: 10.1016/j.jmb.2009.11.060] [Citation(s) in RCA: 126] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2009] [Revised: 11/24/2009] [Accepted: 11/24/2009] [Indexed: 11/16/2022]
Abstract
Monoglyceride lipase (MGL) is a serine hydrolase that hydrolyses 2-arachidonoylglycerol (2-AG) into arachidonic acid and glycerol. 2-AG is an endogenous ligand of cannabinoid receptors, involved in various physiological processes in the brain. We present here the first crystal structure of human MGL in its apo form and in complex with the covalent inhibitor SAR629. MGL shares the classic fold of the alpha/beta hydrolase family but depicts an unusually large hydrophobic occluded tunnel with a highly flexible lid at its entry and the catalytic triad buried at its end. Structures reveal the configuration of the catalytic triad and the shape and nature of the binding site of 2-AG. The bound structure of SAR629 highlights the key interactions for productive binding with MGL. The shape of the tunnel suggests a high druggability of the protein and provides an attractive template for drug discovery.
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Affiliation(s)
- T Bertrand
- Department of Structural Biology, Sanofi-Aventis, 13 Quai Jules Guesde, 94403 Vitry-sur-Seine cedex, France.
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35
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Guindon J, Hohmann AG. The endocannabinoid system and pain. CNS & NEUROLOGICAL DISORDERS DRUG TARGETS 2009; 8:403-21. [PMID: 19839937 DOI: 10.2174/187152709789824660] [Citation(s) in RCA: 318] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2009] [Accepted: 06/24/2009] [Indexed: 12/29/2022]
Abstract
The therapeutic potential of cannabinoids has been the topic of extensive investigation following the discovery of cannabinoid receptors and their endogenous ligands. Cannabinoid receptors and their endogenous ligands are present at supraspinal, spinal and peripheral levels. Cannabinoids suppress behavioral responses to noxious stimulation and suppress nociceptive processing through activation of cannabinoid CB(1) and CB(2) receptor subtypes. Endocannabinoids, the brain's own cannabis-like substances, share the same molecular target as Delta(9)-tetrahydrocannabinol, the main psychoactive component in cannabis. Endocannabinoids serve as synaptic circuit breakers and regulate multiple physiological and pathological conditions, e.g. regulation of food intake, immunomodulation, inflammation, analgesia, cancer, addictive behavior, epilepsy and others. This review will focus on uncovering the roles of anandamide and 2-arachidonoylglycerol, the two best characterized endocannabinoids identified to date, in controlling nociceptive responding. The roles of anandamide and 2-arachidonoylglycerol, released under physiological conditions, in modulating nociceptive responding at different levels of the neuraxis will be emphasized in this review. Effects of modulation of endocannabinoid levels through inhibition of endocannabinoid hydrolysis and uptake is also compared with effects of exogenous administration of synthetic endocannabinoids in acute, inflammatory and neuropathic pain models. Finally, the therapeutic potential of the endocannabinoid signaling system is discussed in the context of identifying novel pharmacotherapies for the treatment of pain.
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Affiliation(s)
- Josée Guindon
- Neuroscience and Behavior Program, Department of Psychology, University of Georgia, Athens, GA 30602-3013, USA
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36
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Nyilas R, Gregg LC, Mackie K, Watanabe M, Zimmer A, Hohmann AG, Katona I. Molecular architecture of endocannabinoid signaling at nociceptive synapses mediating analgesia. Eur J Neurosci 2009; 29:1964-78. [PMID: 19453631 DOI: 10.1111/j.1460-9568.2009.06751.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cannabinoid administration suppresses pain by acting at spinal, supraspinal and peripheral levels. Intrinsic analgesic pathways also exploit endocannabinoids; however, the underlying neurobiological substrates of endocannabinoid-mediated analgesia have remained largely unknown. Compelling evidence shows that, upon exposure to a painful environmental stressor, an endocannabinoid molecule called 2-arachidonoylglycerol (2-AG) is mobilized in the lumbar spinal cord in temporal correlation with stress-induced antinociception. We therefore characterized the precise molecular architecture of 2-AG signaling and its involvement in nociception in the rodent spinal cord. Nonradioactive in situ hybridization revealed that dorsal horn neurons widely expressed the mRNA of diacylglycerol lipase-alpha (DGL-alpha), the synthesizing enzyme of 2-AG. Peroxidase-based immunocytochemistry demonstrated high levels of DGL-alpha protein and CB(1) cannabinoid receptor, a receptor for 2-AG, in the superficial dorsal horn, at the first site of modulation of the ascending pain pathway. High-resolution electron microscopy uncovered postsynaptic localization of DGL-alpha at nociceptive synapses formed by primary afferents, and revealed presynaptic positioning of CB(1) on excitatory axon terminals. Furthermore, DGL-alpha in postsynaptic elements receiving nociceptive input was colocalized with metabotropic glutamate receptor 5 (mGluR(5)), whose activation induces 2-AG biosynthesis. Finally, intrathecal activation of mGluR(5) at the lumbar level evoked endocannabinoid-mediated stress-induced analgesia through the DGL-2-AG-CB(1) pathway. Taken together, these findings suggest a key role for 2-AG-mediated retrograde suppression of nociceptive transmission at the spinal level. The striking positioning of the molecular players of 2-AG synthesis and action at nociceptive excitatory synapses suggests that pharmacological manipulation of spinal 2-AG levels may be an efficacious way to regulate pain sensation.
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Affiliation(s)
- Rita Nyilas
- Institute of Experimental Medicine, Hungarian Academy of Sciences, Szigony u. 43., H-1083 Budapest, Hungary
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37
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García MDC, Adler-Graschinsky E, Celuch SM. Enhancement of the hypotensive effects of intrathecally injected endocannabinoids by the entourage compound palmitoylethanolamide. Eur J Pharmacol 2009; 610:75-80. [DOI: 10.1016/j.ejphar.2009.03.021] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2008] [Revised: 03/03/2009] [Accepted: 03/05/2009] [Indexed: 10/21/2022]
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38
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Butler RK, Finn DP. Stress-induced analgesia. Prog Neurobiol 2009; 88:184-202. [PMID: 19393288 DOI: 10.1016/j.pneurobio.2009.04.003] [Citation(s) in RCA: 442] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2008] [Revised: 03/15/2009] [Accepted: 04/15/2009] [Indexed: 12/21/2022]
Abstract
For over 30 years, scientists have been investigating the phenomenon of pain suppression upon exposure to unconditioned or conditioned stressful stimuli, commonly known as stress-induced analgesia. These studies have revealed that individual sensitivity to stress-induced analgesia can vary greatly and that this sensitivity is coupled to many different phenotypes including the degree of opioid sensitivity and startle response. Furthermore, stress-induced analgesia is influenced by age, gender, and prior experience to stressful, painful, or other environmental stimuli. Stress-induced analgesia is mediated by activation of the descending inhibitory pain pathway. Pharmacological and neurochemical studies have demonstrated involvement of a large number of neurotransmitters and neuropeptides. In particular, there are key roles for the endogenous opioid, monoamine, cannabinoid, gamma-aminobutyric acid and glutamate systems. The study of stress-induced analgesia has enhanced our understanding of the fundamental physiology of pain and stress and can be a useful approach for uncovering new therapeutic targets for the treatment of pain and stress-related disorders.
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Affiliation(s)
- Ryan K Butler
- Department of Pharmacology and Therapeutics, NCBES Neuroscience Cluster and Centre for Pain Research, National University of Ireland, Galway, University Road, Galway, Ireland
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39
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Abstract
Pharmacological and biochemical investigations on the endocannabinoid system are facilitated by the availability of compounds which interact with its constituents in specific and understandable ways. This chapter describes the main representatives of several classes of chemicals employed as pharmacological tools in this field, focusing on small organic compounds having, where possible, a drug-like structure. Many compounds having different intrinsic activity and selectivity towards the G-protein coupled receptors (GPCR) CB₁ and CB₂ are now available and are currently employed in research protocols. Recently, allosteric ligands for CB₁ receptor and selective ligands for GPR55, a newly characterised GPCR, have also been described in the literature. As for compounds affecting endocannabinoid levels in living tissues, many classes of selective and, in some cases, drug-like inhibitors of FAAH are available, while only compounds with poor selectivity or in vivo activity are known to inhibit other enzymes involved in endocannabinoid catabolism, such as NAAA or MGL, and in endocannabinoid biosynthesis.
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Affiliation(s)
- Marco Mor
- Dipartimento Farmaceutico, Università degli Studi di Parma, viale G. P. Usberti 27/A Campus Universitario, Parma, I-43100, Italy.
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40
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Butler RK, Rea K, Lang Y, Gavin AM, Finn DP. Endocannabinoid-mediated enhancement of fear-conditioned analgesia in rats: Opioid receptor dependency and molecular correlates. Pain 2008; 140:491-500. [DOI: 10.1016/j.pain.2008.10.002] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2008] [Revised: 10/05/2008] [Accepted: 10/07/2008] [Indexed: 11/16/2022]
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41
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Zhang J, Chen C. Endocannabinoid 2-arachidonoylglycerol protects neurons by limiting COX-2 elevation. J Biol Chem 2008; 283:22601-11. [PMID: 18534982 PMCID: PMC2504873 DOI: 10.1074/jbc.m800524200] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2008] [Revised: 05/28/2008] [Indexed: 11/06/2022] Open
Abstract
Endocannabinoids are involved in synaptic signaling and neuronal protection; however, our understanding of the mechanisms by which endocannabinoids protect neurons from harmful insults remains elusive. 2-Arachidonoylglycerol (2-AG), the most abundant endogenous cannabinoid and a full agonist for cannabinoid receptors (CB1 and CB2), is a substrate for cyclooxygenase-2 (COX-2) and can be metabolized by COX-2. Here we show, however, that 2-AG is also capable of suppressing elevation of hippocampal COX-2 expression in response to proinflammatory and excitotoxic stimuli. 2-AG prevents neurodegeneration from toxic assaults that elevate COX-2 expression and inhibits the COX-2 elevation-enhanced excitatory glutamatergic synaptic transmission. The action of 2-AG on suppression of COX-2 appeared to be mediated via the pertussis toxin-sensitive G protein-coupled CB1 receptor and MAPK/NF-kappaB signaling pathways. Our results reveal that 2-AG functions as an endogenous COX-2 inhibitor protecting neurons from harmful insults by preventing excessive expression of COX-2, which provides a mechanistic basis for opening up new therapeutic approaches for protecting neurons from inflammation- and excitotoxicity-induced neurodegeneration.
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Affiliation(s)
- Jian Zhang
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, USA
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42
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Desroches J, Guindon J, Lambert C, Beaulieu P. Modulation of the anti-nociceptive effects of 2-arachidonoyl glycerol by peripherally administered FAAH and MGL inhibitors in a neuropathic pain model. Br J Pharmacol 2008; 155:913-24. [PMID: 18695638 DOI: 10.1038/bjp.2008.322] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
BACKGROUND AND PURPOSE There are limited options for the treatment of neuropathic pain. Endocannabinoids, such as anandamide and 2-arachidonoyl glycerol (2-AG), are promising pain modulators and there is recent evidence of interactions between anandamide and 2-AG biosynthesis and metabolism. It has been clearly demonstrated that 2-AG degradation is mainly catalysed not only by monoacylglycerol lipase (MGL) but also by a fatty acid amide hydrolase (FAAH). Inhibitors specifically targeting these two enzymes have also been described: URB602 and URB597, respectively. However, the anti-nociceptive effects of the combination of peripherally injected 2-AG, URB602 and URB597 in a neuropathic pain model have not yet been determined. This was performed in the presence or absence of cannabinoid CB(1) (AM251) and CB(2) (AM630) receptor antagonists. EXPERIMENTAL APPROACH Mechanical allodynia and thermal hyperalgesia were evaluated in 213 male Wistar rats allocated to 32 different groups. Drugs were injected subcutaneously in the dorsal surface of the hind paw (50 muL) 15 min before pain tests. KEY RESULTS 2-AG, URB602 and URB597 significantly decreased mechanical allodynia and thermal hyperalgesia with ED50 of 1.6+/-1.5 and 127+/-83 mug for 2-AG and URB602, respectively. These effects were mediated locally and were mostly inhibited by the two cannabinoid antagonists. CONCLUSIONS AND IMPLICATIONS The combination of the three compounds did not produce any greater anti-allodynic or anti-hyperalgesic effects, suggesting that FAAH inhibition could reduce or limit the anti-nociceptive effects of 2-AG. Peripheral administration of endocannabinoids or MGL/FAAH inhibitors is a promising analgesic approach requiring further investigation.
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Affiliation(s)
- J Desroches
- Department of Pharmacology, Université de Montréal-CHUM, Montréal, Quebec, Canada
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43
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Kurrikoff K, Inno J, Matsui T, Vasar E. Stress-induced analgesia in mice: evidence for interaction between endocannabinoids and cholecystokinin. Eur J Neurosci 2008; 27:2147-55. [DOI: 10.1111/j.1460-9568.2008.06160.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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44
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Schuelert N, McDougall JJ. Cannabinoid-mediated antinociception is enhanced in rat osteoarthritic knees. ACTA ACUST UNITED AC 2008; 58:145-53. [PMID: 18163511 DOI: 10.1002/art.23156] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
OBJECTIVE To determine whether local administration of the cannabinoid 1 (CB(1)) receptor agonist arachidonyl-2-chloroethylamide (ACEA) can modulate joint nociception in control rat knee joints and in experimental osteoarthritis (OA). METHODS OA was induced in male Wistar rats by intraarticular injection of 3 mg of sodium mono-iodoacetate, with a recovery period of 14 days. Electrophysiologic recordings were made of knee joint primary afferent nerve fibers in response to normal rotation and noxious hyperrotation of the joint both before and after close intraarterial injection of different doses of ACEA. RESULTS Local application of the CB(1) agonist significantly reduced the firing rate of afferent nerve fibers by up to 50% in control knee joints (n=19) and up to 62% in OA knee joints (n=29; P<0.01). Coadministration of the CB(1) receptor antagonist AM251 or the transient receptor potential vanilloid 1 (TRPV-1) ion channel antagonist SB366791 significantly reduced the desensitizing effect of ACEA. The CB(1) receptor antagonist AM251 by itself had no effect in the control joint but significantly increased the firing rate of afferent nerve fibers in the OA joint. CONCLUSION These findings indicate that activation of peripheral CB(1) receptors reduces the mechanosensitivity of afferent nerve fibers in control and OA knee joints. Blockade of either the CB(1) receptor or the TRPV-1 channel significantly reduced the efficacy of ACEA, which suggests that both receptors are involved in cannabinoid-mediated antinociception. The increased nerve activity observed following CB(1) receptor antagonism suggests a tonic release of endocannabinoids during OA. As such, peripheral CB(1) receptors may be important targets in controlling OA pain.
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Vogeser M, Schelling G. Pitfalls in measuring the endocannabinoid 2-arachidonoyl glycerol in biological samples. Clin Chem Lab Med 2008; 45:1023-5. [PMID: 17867992 DOI: 10.1515/cclm.2007.197] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND The endocannabinoid 2-arachidonoyl glycerol (2-AG) undergoes spontaneous isomerization to biologically inactive 1-AG. This effect has not been adequately addressed in previous studies that reported 2-AG concentrations in biological samples. METHODS Liquid chromatography tandem-mass spectrometry (LC-MS/MS) was used for 1-AG and 2-AG analyses. RESULTS Identical collision-induced disintegration spectra were found for 1-AG and 2-AG. For specific detection of both compounds, which share a common mass transition, baseline chromatographic separation is mandatory, even when applying MS/MS technology with its generally high detection specificity. When using standard chromatographic conditions with the very short run times typically used in LC-MS/MS methods, co-elution of 2-AG with 1-AG, which is present in human serum, causes false 2-AG results. CONCLUSIONS Our data highlight that the analytical specificity of MS/MS can be limited by interference from isobaric isomers with identical disintegration patterns. The specificity of this technology must be carefully evaluated for each individual application.
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Affiliation(s)
- Michael Vogeser
- Institute of Clinical Chemistry, Hospital of the University of Munich, Munich, Germany.
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Saario SM, Laitinen JT. Therapeutic Potential of Endocannabinoid-Hydrolysing Enzyme Inhibitors. Basic Clin Pharmacol Toxicol 2007; 101:287-93. [PMID: 17910610 DOI: 10.1111/j.1742-7843.2007.00130.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The specific protein target of delta9-tetrahydrocannabinol (delta9-THC), the main active ingredient of Cannabis sativa L., was characterized from rat brain nearly 20 years ago, and several endogenous compounds and proteins comprising the endocannabinoid (eCB) system have since been discovered. It has become evident that the eCB system consists of at least two cannabinoid receptors (i.e. the CB1 and CB2 receptors), in addition to their endogenous ligands (the eCBs) and several enzymes involved in the biosynthesis and catabolism of the eCBs. The two well-established eCBs, N-arachidonoylethanolamide (AEA) and 2-arachidonoylglycerol (2-AG), are produced by neurons on demand, act near their sites of synthesis and are effectively metabolized by fatty acid amide hydrolase (FAAH) and monoglyceride lipase (MGL), respectively. Inhibitors specifically targeting these enzymes could offer novel therapeutic approaches (e.g. for the treatment of pain and movement disorders). This MiniReview summarizes the literature concerning the potential therapeutic potential of FAAH and MGL inhibitors.
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Affiliation(s)
- Susanna M Saario
- Department of Pharmaceutical Chemistry, University of Kuopio, Kuopio, Finland.
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Comelli F, Giagnoni G, Bettoni I, Colleoni M, Costa B. The inhibition of monoacylglycerol lipase by URB602 showed an anti-inflammatory and anti-nociceptive effect in a murine model of acute inflammation. Br J Pharmacol 2007; 152:787-94. [PMID: 17700715 PMCID: PMC2190015 DOI: 10.1038/sj.bjp.0707425] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND AND PURPOSE 2-arachidonoylglycerol (2-AG) is an endocannabinoid whose hydrolysis is predominantly catalysed by the enzyme monoacylglycerol lipase (MAGL). The development of MAGL inhibitors could offer an opportunity to investigate the anti-inflammatory and anti-nociceptive role of 2-AG, which have not yet been elucidated. On these bases, URB602, a MAGL inhibitor, was tested in a murine model of inflammation/inflammatory pain. EXPERIMENTAL APPROACH Acute inflammation was induced by intraplantar injection of lambda-carrageenan into mice. The highest dose to be employed has been selected performing the tetrad assays for cannabimimetic activity in mice. URB602 anti-inflammatory and anti-nociceptive efficacy (assessed by plethysmometer and plantar test, respectively) was evaluated both in a preventive regimen (drug administered 30 min before carrageenan) and in a therapeutic regimen (URB602 administered 30 min after carrageenan). To elucidate the cannabinoid receptor involvement, rimonabant and SR144528, CB1 and CB2 selective antagonists, respectively, were given 15 min before URB602. KEY RESULTS Systemic administration of URB602 elicited a dose-dependent anti-oedemigen and anti-nociceptive effect that was reversed exclusively by the CB2 receptor antagonist. The efficacy of URB602 persisted also when the compound was administered in a therapeutic regimen, suggesting the ability of URB602 to improve established disease. CONCLUSIONS AND IMPLICATIONS The present report highlighted the ability of the selective MAGL inhibitor, URB602, to prevent and treat an acute inflammatory disease without producing adverse psychoactive effects. The data presented herein also contributed to clarify the physiological role of 2-AG in respect to inflammatory reactions, suggesting its protective role in the body.
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Affiliation(s)
- F Comelli
- Department of Biotechnology and Bioscience, University of Milano-Bicocca, Milano, Italy
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Suplita RL, Eisenstein SA, Neely MH, Moise AM, Hohmann AG. Cross-sensitization and cross-tolerance between exogenous cannabinoid antinociception and endocannabinoid-mediated stress-induced analgesia. Neuropharmacology 2007; 54:161-71. [PMID: 17714742 PMCID: PMC2771679 DOI: 10.1016/j.neuropharm.2007.07.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2007] [Revised: 06/22/2007] [Accepted: 07/04/2007] [Indexed: 11/22/2022]
Abstract
Footshock stress induces both endocannabinoid mobilization and antinociception. The present studies investigated behavioral plasticity in cannabinoid antinociceptive mechanisms following repeated activation using the tail-flick test. A secondary objective was to ascertain whether blockade of stress antinociception by the CB(1) antagonist rimonabant could be attributed to changes in locomotor activity. The cannabinoid agonist WIN55,212-2 induced hypoactivity in the open field relative to vehicle-treated controls. By contrast, rimonabant, administered at a dose that virtually eliminated endocannabinoid-mediated stress antinociception, failed to alter locomotor behavior (i.e. time resting, ambulatory counts, distance traveled) in rats subjected to the same stressor. Rats exposed acutely to footshock were hypersensitive to the antinociceptive effects of WIN55,212-2 and Delta(9)-tetrahydrocannabinol (Delta(9)-THC). The converse was also true; acute Delta(9)-THC and WIN55,212-2 administration potentiated stress antinociception, suggesting a bidirectional sensitization between endocannabinoid-mediated stress antinociception and exogenous cannabinoid antinociception. Stress antinociception was also attenuated following chronic relative to acute treatment with WIN55,212-2 or Delta(9)-THC. Repeated exposure to footshock (3 min/day for 15 days), however, failed to attenuate antinociception induced by either footshock stress or WIN55,212-2. Our results demonstrate that endocannabinoid-mediated stress antinociception cannot be attributed to motor suppression. Our results further identify a functional plasticity of the cannabinoid system in response to repeated activation. The existence of cross-sensitization between endocannabinoid-mediated stress antinociception and exogenous cannabinoid antinociception suggests that these phenomena are mediated by a common mechanism. The observation of stress-induced hypersensitivity to effects of exogenous cannabinoids may have clinical implications for understanding marijuana abuse liability in humans.
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Affiliation(s)
| | | | | | | | - Andrea G. Hohmann
- Corresponding Author: Andrea G. Hohmann, Ph.D., Telephone: (706) 542-2252, Fax: (706) 542-3275,
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Fowler CJ. The cannabinoid system and its pharmacological manipulation--a review, with emphasis upon the uptake and hydrolysis of anandamide. Fundam Clin Pharmacol 2007; 20:549-62. [PMID: 17109648 DOI: 10.1111/j.1472-8206.2006.00442.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Although cannabis has been used both recreationally and for medicinal purposes since ancient times, it was not until the 1990s that the receptors responsible for many of the actions of Delta(9)-tetrahydrocannabinol, the main psychoactive ingredient of cannabis, were cloned. Since then, our knowledge of the endogenous cannabinoid system, its physiology, pharmacology and therapeutic potential have expanded enormously. In the present review, the cannabinoid system is described, with particular emphasis on the mechanisms of removal and metabolism of the endocannabinoid signalling molecule anandamide. The current literature shows that cells can accumulate anandamide, and that this process can be disrupted pharmacologically, but that the nature of the mechanism(s) involved remains a matter of some debate. The main enzyme for the hydrolysis of anandamide, fatty acid amide hydrolase, is well characterized, and molecules selectively inhibiting this enzyme have potential therapeutic utility in a number of areas, in particular for the treatment of pain conditions.
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Affiliation(s)
- Christopher J Fowler
- Department of Pharmacology and Clinical Neuroscience, Umeå University, SE901 87 Umeå, Sweden.
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Abstract
2-Arachidonoylglycerol (2-AG) is an endogenous cannabinoid (endocannabinoid) lipid whose functions remain poorly understood. Guindon and colleagues report the novel finding that exogenous application of 2-AG induces peripheral antinociceptive effects that are mediated, at least in part, by actions at peripheral cannabinoid CB(2) receptors. URB602, a recently described inhibitor of monoacylglycerol lipase, an enzyme that catalyzes 2-AG hydrolysis in vivo, also induced peripheral antinociceptive effects and enhanced the actions of 2-AG. Peripheral analgesic mechanisms represent promising therapeutic targets for suppressing pain in the absence of unwanted central nervous system side-effects (e.g. psychoactivity) associated with activation of central CB(1) receptors. The therapeutic potential of inhibitors of 2-AG deactivation for the treatment of inflammatory pain is discussed.
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Affiliation(s)
- A G Hohmann
- Neuroscience and Behavior Program, Department of Psychology, University of Georgia, Athens, GA 30602-3013, USA.
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