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Kędziora M, Boccella S, Marabese I, Mlost J, Infantino R, Maione S, Starowicz K. Inhibition of anandamide breakdown reduces pain and restores LTP and monoamine levels in the rat hippocampus via the CB 1 receptor following osteoarthritis. Neuropharmacology 2023; 222:109304. [PMID: 36341807 DOI: 10.1016/j.neuropharm.2022.109304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Revised: 07/15/2022] [Accepted: 10/23/2022] [Indexed: 11/06/2022]
Abstract
Chronic pain is a persistent, complex condition that contributes to impaired mood, anxiety and emotional problems. Osteoarthritis (OA) is one of the major causes of chronic pain in adults and elderly people. A substantial body of evidence demonstrate that hippocampal neural circuits, especially monoamine dopamine and serotonin levels, contributes to negative affect and avoidance motivation experienced during pain. Current pharmacological strategies for OA patients are unsatisfying and the endocannabinoid system modulation might represent an alternative for the treatment of OA-related pain. In the present study, we used a rat model of osteoarthritis induced by intra-articular injection of sodium monoiodoacetate to assess, 28 days post-induction, the contribution of endocannabinoid system on the possible alteration in pain perception and affective behavior, in LTP and monoamine levels in the lateral entorhinal cortex-dentate gyrus pathway. The results show that OA-related chronic pain induces working memory impairment and depressive-like behavior appearance, diminishes LTP, decreases dopamine levels and increases serotonin levels in the rat dentate gyrus. URB597 administration (i.p., 1 mg/kg) reduces hyperalgesia and mechanical allodynia, improves recognition memory and depressive-live behavior, restores LTP and normalizes monoamine levels in the hippocampus. The effect was observed 60-120 min post-treatment and was blocked by AM251, which proves the action of URB597 via the CB1 receptor. Therefore, our study confirms the role of anandamide in OA-related chronic pain management at the behavioral and hippocampal levels. This article is part of the Special Issue on 'Advances in mechanisms and therapeutic targets relevant to pain'.
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Affiliation(s)
- Marta Kędziora
- Department of Neurochemistry, Maj Institute of Pharmacology, Polish Academy of Sciences, Cracow, Poland
| | - Serena Boccella
- Department of Experimental Medicine, Division of Pharmacology, University of Campania "L. Vanvitelli", Naples, Italy
| | - Ida Marabese
- Department of Experimental Medicine, Division of Pharmacology, University of Campania "L. Vanvitelli", Naples, Italy
| | - Jakub Mlost
- Department of Neurochemistry, Maj Institute of Pharmacology, Polish Academy of Sciences, Cracow, Poland
| | - Rosmara Infantino
- Department of Experimental Medicine, Division of Pharmacology, University of Campania "L. Vanvitelli", Naples, Italy
| | - Sabatino Maione
- Department of Experimental Medicine, Division of Pharmacology, University of Campania "L. Vanvitelli", Naples, Italy; IRCSS, Neuromed, Pozzilli (IS), 86077, Italy; ERG, Endocannabinoid Research Group, CNR, Pozzuoli, Italy
| | - Katarzyna Starowicz
- Department of Neurochemistry, Maj Institute of Pharmacology, Polish Academy of Sciences, Cracow, Poland.
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Effects of Intra-BLA Administration of PPAR Antagonists on Formalin-Evoked Nociceptive Behaviour, Fear-Conditioned Analgesia, and Conditioned Fear in the Presence or Absence of Nociceptive Tone in Rats. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27062021. [PMID: 35335382 PMCID: PMC8949000 DOI: 10.3390/molecules27062021] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 03/02/2022] [Accepted: 03/03/2022] [Indexed: 11/16/2022]
Abstract
There is evidence for the involvement of peroxisome proliferator-activated receptors (PPARs) in pain, cognition, and anxiety. However, their role in pain–fear interactions is unknown. The amygdala plays a key role in pain, conditioned fear, and fear-conditioned analgesia (FCA). We investigated the effects of intra-basolateral amygdala (BLA) administration of PPARα, PPARβ/δ, and PPARγ antagonists on nociceptive behaviour, FCA, and conditioned fear in the presence or absence of nociceptive tone. Male Sprague-Dawley (SD) rats received footshock (FC) or no footshock (NFC) in a conditioning arena. Twenty-three and a half hours later, rats received an intraplantar injection of formalin or saline and, 15 min later, intra-BLA microinjections of vehicle, PPARα (GW6471) PPARβ/δ (GSK0660), or PPARγ (GW9662) antagonists before arena re-exposure. Pain and fear-related behaviour were assessed, and neurotransmitters/endocannabinoids measured post-mortem. Intra-BLA administration of PPARα or PPARγ antagonists potentiated freezing in the presence of nociceptive tone. Blockade of all PPAR subtypes in the BLA increased freezing and BLA dopamine levels in NFC rats in the absence of nociceptive tone. Administration of intra-BLA PPARα and PPARγ antagonists increased levels of dopamine in the BLA compared with the vehicle-treated counterparts. In conclusion, PPARα and PPARγ in the BLA play a role in the expression or extinction of conditioned fear in the presence or absence of nociceptive tone.
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Lapointe T, Wolter M, Leri F. Analysis of memory modulation by conditioned stimuli. ACTA ACUST UNITED AC 2021; 28:87-94. [PMID: 33593927 PMCID: PMC7888238 DOI: 10.1101/lm.052407.120] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Accepted: 12/02/2020] [Indexed: 12/03/2022]
Abstract
Conditioned stimuli (CS) have multiple psychological functions that can potentially contribute to their effect on memory formation. It is generally believed that CS-induced memory modulation is primarily due to conditioned emotional responses, however, well-learned CSs not only generate the appropriate behavioral and physiological reactions required to best respond to an upcoming unconditioned stimulus (US), but they also serve as signals that the US is about to occur. Therefore, it is possible that CSs can impact memory consolidation even when their ability to elicit conditioned emotional arousal is significantly reduced. To test this, male Sprague–Dawley rats trained on a signaled active avoidance task were divided into “Avoider” and “Non-Avoider” subgroups on the basis of percentage avoidance after 6 d of training. Subgroup differences in responding to the CS complex were maintained during a test carried out in the absence of the US. Moreover, the subgroups displayed significant differences in stress-induced analgesia (hot-plate test) immediately after this test, suggesting significant subgroup differences in conditioned emotionality. Importantly, using the spontaneous object recognition task, it was found that immediate post-sample exposure to the avoidance CS complex had a similar enhancing effect on object memory in the two subgroups. Therefore, to our knowledge, this is the first study to demonstrate that a significant conditioned emotional response is not necessary for the action of a predictive CS on modulation of memory consolidation.
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Affiliation(s)
- Thomas Lapointe
- Department of Psychology, Collaborative Program in Neuroscience, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Michael Wolter
- Department of Psychology, Collaborative Program in Neuroscience, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Francesco Leri
- Department of Psychology, Collaborative Program in Neuroscience, University of Guelph, Guelph, Ontario N1G 2W1, Canada
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Alijanpour S, Jafaripour S, Ghasemzadeh Z, Khakpai F, Zarrindast MR. Harmaline potentiates morphine-induced antinociception via affecting the ventral hippocampal GABA-A receptors in mice. Eur J Pharmacol 2020; 893:173806. [PMID: 33345854 DOI: 10.1016/j.ejphar.2020.173806] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Revised: 12/06/2020] [Accepted: 12/10/2020] [Indexed: 11/13/2022]
Abstract
Morphine is one of the most effective medications for treatment of pain, but its side effects limit its use. Therefore, identification of new strategies that can enhance morphine-induced antinociception and/or reduce its side effects will help to develop therapeutic approaches for pain relief. Considering antinociceptive efficacy of harmaline and also highlighted the important role of GABA-A receptors in the pain perception, this research aimed to determine whether the ventral hippocampal (vHip) GABA-A receptors are involved in the possible harmaline-induced enhancement of morphine antinociception. To achieve this, vHip regions of adult male mice were bilaterally cannulated and pain sensitivity was measured in a tail-flick apparatus. Intraperitoneally administration of morphine (0, 2, 4 and 6 mg/kg) or harmaline (0, 1.25, 5 and 10 mg/kg) increased the percentage of maximal possible effect (%MPE) and induced antinociception. Interestingly, co-administration of sub-effective doses of harmaline (5 mg/kg) and morphine (2 mg/kg) induced antinociception. Intra-vHip microinjection of muscimol (0, 200 and 300 ng/mice), a GABA-A receptor agonist, enhanced the anti-nociceptive effects of harmaline (2.5 mg/kg)+morphine (2 mg/kg) combination. Microinjection of the same doses of muscimol into the vHip by itself did not alter tail-flick latency. Intra-vHip microinjection of bicuculline (100 ng/mouse), a GABA-A receptor antagonist, did not cause a significant change in MPE%. Bicuculline (60 and 100 ng/mouse, intra-vHip) was administered with the harmaline (5 mg/kg)+morphine (2 mg/kg), and inhibited the potentiating effect of harmaline on morphine response. These findings favor the notion that GABAergic mechanisms in the vHip facilitate harmaline-induced potentiation of morphine response in the tail-flick test in part through GABA-A receptors. These findings shall provide insights and strategies into the development of pain suppressing drugs.
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Affiliation(s)
- Sakineh Alijanpour
- Department of Biology, Faculty of Science, Gonbad Kavous University, Gonbad Kavous, Iran.
| | - Samira Jafaripour
- Department of Biology, North Tehran Branch, Islamic Azad University, Tehran, Iran
| | - Zahra Ghasemzadeh
- Department of Animal Biology, School of Biology, College of Science, University of Tehran, Tehran, Iran
| | - Fatemeh Khakpai
- Cognitive and Neuroscience Research Center (CNRC), Tehran Medical Sciences, Islamic Azad University, Tehran, Iran
| | - Mohammad-Reza Zarrindast
- Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran; Iranian National Center for Addiction Studies, Tehran University of Medical Sciences, Tehran, Iran; Endocrinology and Metabolism Research Center, Endocrinology and Metabolism Clinical Sciences Institute, Tehran University of Medical Sciences, Tehran, Iran
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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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Gaspar JC, Okine BN, Llorente-Berzal A, Roche M, Finn DP. Pharmacological Blockade of PPAR Isoforms Increases Conditioned Fear Responding in the Presence of Nociceptive Tone. Molecules 2020; 25:molecules25041007. [PMID: 32102354 PMCID: PMC7070536 DOI: 10.3390/molecules25041007] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2019] [Revised: 02/17/2020] [Accepted: 02/18/2020] [Indexed: 12/29/2022] Open
Abstract
Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors with three isoforms (PPARα, PPARβ/δ, PPARγ) and can regulate pain, anxiety, and cognition. However, their role in conditioned fear and pain-fear interactions has not yet been investigated. Here, we investigated the effects of systemically administered PPAR antagonists on formalin-evoked nociceptive behaviour, fear-conditioned analgesia (FCA), and conditioned fear in the presence of nociceptive tone in rats. Twenty-three and a half hours following fear conditioning to context, male Sprague-Dawley rats received an intraplantar injection of formalin and intraperitoneal administration of vehicle, PPARα (GW6471), PPARβ/δ (GSK0660) or PPARγ (GW9662) antagonists, and 30 min later were re-exposed to the conditioning arena for 15 min. The PPAR antagonists did not alter nociceptive behaviour or fear-conditioned analgesia. The PPARα and PPARβ/δ antagonists prolonged context-induced freezing in the presence of nociceptive tone without affecting its initial expression. The PPARγ antagonist potentiated freezing over the entire trial. In conclusion, pharmacological blockade of PPARα and PPARβ/δ in the presence of formalin-evoked nociceptive tone, impaired short-term, within-trial fear-extinction in rats without affecting pain response, while blockade of PPARγ potentiated conditioned fear responding. These results suggest that endogenous signalling through these three PPAR isoforms may reduce the expression of conditioned fear in the presence of nociceptive tone.
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Affiliation(s)
- Jessica C. Gaspar
- Pharmacology and Therapeutics Department, National University of Ireland Galway, University Road, H91 W5P7 Galway, Ireland; (J.C.G.); (B.N.O.); (A.L.-B.)
- Galway Neuroscience Centre, National University of Ireland Galway, University Road, H91 W5P7 Galway, Ireland;
- Centre for Pain Research, National University of Ireland Galway, University Road, H91 W5P7 Galway, Ireland
| | - Bright N. Okine
- Pharmacology and Therapeutics Department, National University of Ireland Galway, University Road, H91 W5P7 Galway, Ireland; (J.C.G.); (B.N.O.); (A.L.-B.)
- Galway Neuroscience Centre, National University of Ireland Galway, University Road, H91 W5P7 Galway, Ireland;
- Centre for Pain Research, National University of Ireland Galway, University Road, H91 W5P7 Galway, Ireland
| | - Alvaro Llorente-Berzal
- Pharmacology and Therapeutics Department, National University of Ireland Galway, University Road, H91 W5P7 Galway, Ireland; (J.C.G.); (B.N.O.); (A.L.-B.)
- Galway Neuroscience Centre, National University of Ireland Galway, University Road, H91 W5P7 Galway, Ireland;
- Centre for Pain Research, National University of Ireland Galway, University Road, H91 W5P7 Galway, Ireland
| | - Michelle Roche
- Galway Neuroscience Centre, National University of Ireland Galway, University Road, H91 W5P7 Galway, Ireland;
- Centre for Pain Research, National University of Ireland Galway, University Road, H91 W5P7 Galway, Ireland
- Physiology Department, National University of Ireland Galway, University Road, H91 W5P7 Galway, Ireland
| | - David P. Finn
- Pharmacology and Therapeutics Department, National University of Ireland Galway, University Road, H91 W5P7 Galway, Ireland; (J.C.G.); (B.N.O.); (A.L.-B.)
- Galway Neuroscience Centre, National University of Ireland Galway, University Road, H91 W5P7 Galway, Ireland;
- Physiology Department, National University of Ireland Galway, University Road, H91 W5P7 Galway, Ireland
- Correspondence: ; Tel.: +353-(0)91-495-280; Fax: +353-(0)91-495-586
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Characterization of cerebral cortical endocannabinoid levels in a rat inguinal surgery model using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Ir J Psychol Med 2019; 39:54-63. [PMID: 31354118 DOI: 10.1017/ipm.2019.29] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
BACKGROUND The brain endocannabinoid system is believed to play significant roles in anti-nociception, fear response, anxiety, and stress. This study investigated the effects of rat inguinal surgery on the levels of endocannabinoids in the cerebral cortex. AIM The aim of this study was to investigate the effects of acute post-surgical pain on the levels of endocannabinoids in the cerebral cortex. METHODS Quantitation of endocannabinoids in the rat cerebral cortex was performed by liquid chromatography-tandem mass spectrometry. RESULTS There was no significant difference in the cerebral cortical levels of anandamide (AEA) and 2-arachidonoylglycerol (2-AG) between the sham and surgery experimental groups. However, there were lateralized differences in the levels of these endocannabinoids between the right and left cerebral cortices irrespective of the two groups. The concentrations of AEA and 2-AG were significantly higher in the right cerebral cortex compared to the contralateral cerebral cortex. CONCLUSION Acute post-surgical pain did not induce significant alterations in the cerebral cortical levels of endocannabinoids in this study, but the phenomenon of lateralization of the cerebral cortical AEA and 2-AG levels was observed; this latter finding may be related to the role played by endocannabinoids in fear conditioning.
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Gobira PH, Oliveira AC, Gomes JS, da Silveira VT, Asth L, Bastos JR, Batista EM, Issy AC, Okine BN, de Oliveira AC, Ribeiro FM, Del Bel EA, Aguiar DC, Finn DP, Moreira FA. Opposing roles of CB 1 and CB 2 cannabinoid receptors in the stimulant and rewarding effects of cocaine. Br J Pharmacol 2018; 176:1541-1551. [PMID: 30101419 DOI: 10.1111/bph.14473] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Revised: 07/19/2018] [Accepted: 07/24/2018] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND AND PURPOSE The endocannabinoids anandamide and 2-arachidonoylglycerol (2-AG) bind to CB1 and CB2 cannabinoid receptors in the brain and modulate the mesolimbic dopaminergic pathway. This neurocircuitry is engaged by psychostimulant drugs, including cocaine. Although CB1 receptor antagonism and CB2 receptor activation are known to inhibit certain effects of cocaine, they have been investigated separately. Here, we tested the hypothesis that there is a reciprocal interaction between CB1 receptor blockade and CB2 receptor activation in modulating behavioural responses to cocaine. EXPERIMENTAL APPROACH Male Swiss mice received i.p. injections of cannabinoid-related drugs followed by cocaine, and were then tested for cocaine-induced hyperlocomotion, c-Fos expression in the nucleus accumbens and conditioned place preference. Levels of endocannabinoids after cocaine injections were also analysed. KEY RESULTS The CB1 receptor antagonist, rimonabant, and the CB2 receptor agonist, JWH133, prevented cocaine-induced hyperlocomotion. The same results were obtained by combining sub-effective doses of both compounds. The CB2 receptor antagonist, AM630, reversed the inhibitory effects of rimonabant in cocaine-induced hyperlocomotion and c-Fos expression in the nucleus accumbens. Selective inhibitors of anandamide and 2-AG hydrolysis (URB597 and JZL184, respectively) failed to modify this response. However, JZL184 prevented cocaine-induced hyperlocomotion when given after a sub-effective dose of rimonabant. Cocaine did not change brain endocannabinoid levels. Finally, CB2 receptor blockade reversed the inhibitory effect of rimonabant in the acquisition of cocaine-induced conditioned place preference. CONCLUSION AND IMPLICATIONS The present data support the hypothesis that CB1 and CB2 receptors work in concert with opposing functions to modulate certain addiction-related effects of cocaine. LINKED ARTICLES This article is part of a themed section on 8th European Workshop on Cannabinoid Research. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.10/issuetoc.
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Affiliation(s)
- Pedro H Gobira
- Department of Pharmacology, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Ana C Oliveira
- Department of Pharmacology, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Julia S Gomes
- Department of Pharmacology, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Vivian T da Silveira
- Department of Pharmacology, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Laila Asth
- Department of Pharmacology, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Juliana R Bastos
- Department of Pharmacology, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Edleusa M Batista
- Department of Biochemistry and Immunology, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Ana C Issy
- Department of Morphology, Stomatology and Basic Pathology, Faculty of Odontology, University of São Paulo, Ribeirão Preto, Brazil
| | - Bright N Okine
- Department of Pharmacology and Therapeutics, School of Medicine, National University of Ireland Galway, Galway, Ireland
| | - Antonio C de Oliveira
- Department of Pharmacology, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Fabiola M Ribeiro
- Department of Biochemistry and Immunology, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Elaine A Del Bel
- Department of Morphology, Stomatology and Basic Pathology, Faculty of Odontology, University of São Paulo, Ribeirão Preto, Brazil
| | - Daniele C Aguiar
- Department of Pharmacology, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - David P Finn
- Department of Pharmacology and Therapeutics, School of Medicine, National University of Ireland Galway, Galway, Ireland
| | - Fabricio A Moreira
- Department of Pharmacology, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
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9
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Rea K, McGowan F, Corcoran L, Roche M, Finn DP. The prefrontal cortical endocannabinoid system modulates fear-pain interactions in a subregion-specific manner. Br J Pharmacol 2018; 176:1492-1505. [PMID: 29847859 DOI: 10.1111/bph.14376] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Revised: 05/11/2018] [Accepted: 05/15/2018] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND AND PURPOSE The emotional processing and coordination of top-down responses to noxious and conditioned aversive stimuli involves the medial prefrontal cortex (mPFC). Evidence suggests that subregions of the mPFC [infralimbic (IfL), prelimbic (PrL) and anterior cingulate (ACC) cortices] differentially alter the expression of contextually induced fear and nociceptive behaviour. We investigated the role of the endocannabinoid system in the IfL, PrL and ACC in formalin-evoked nociceptive behaviour, fear-conditioned analgesia (FCA) and conditioned fear in the presence of nociceptive tone. 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-mPFC administration of AM251 [cannabinoid type 1 (CB1 ) receptor antagonist/inverse agonist], URB597 [fatty acid amide hydrolase (FAAH) inhibitor] or URB597 + AM251 on FCA and freezing behaviour were assessed. KEY RESULTS AM251 attenuated FCA when injected into the IfL or PrL and reduced contextually induced freezing behaviour when injected intra-IfL but not intra-PrL or intra-ACC. Intra-ACC administration of AM251 alone or in combination with URB597 had no effect on FCA or freezing. URB597 attenuated FCA and freezing behaviour when injected intra-IfL, prolonged the expression of FCA when injected intra-PrL and had no effect on these behaviours when injected intra-ACC. CONCLUSIONS AND IMPLICATIONS These results suggest important and differing roles for FAAH substrates or CB1 receptors in the PrL, IfL and ACC in the expression of FCA and conditioned fear in the presence of nociceptive tone. LINKED ARTICLES This article is part of a themed section on 8th European Workshop on Cannabinoid Research. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.10/issuetoc.
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Affiliation(s)
- Kieran Rea
- Pharmacology and Therapeutics, School of Medicine, National University of Ireland Galway, Galway, Ireland.,Galway Neuroscience Centre and Centre for Pain Research, NCBES, National University of Ireland Galway, Galway, Ireland
| | - Fiona McGowan
- Pharmacology and Therapeutics, School of Medicine, National University of Ireland Galway, Galway, Ireland.,Galway Neuroscience Centre and Centre for Pain Research, NCBES, National University of Ireland Galway, Galway, Ireland
| | - Louise Corcoran
- Pharmacology and Therapeutics, School of Medicine, National University of Ireland Galway, Galway, Ireland.,Galway Neuroscience Centre and Centre for Pain Research, NCBES, National University of Ireland Galway, Galway, Ireland
| | - Michelle Roche
- Physiology, School of Medicine, National University of Ireland Galway, Galway, Ireland.,Galway Neuroscience Centre and Centre for Pain Research, NCBES, National University of Ireland Galway, Galway, Ireland
| | - David P Finn
- Pharmacology and Therapeutics, School of Medicine, National University of Ireland Galway, Galway, Ireland.,Galway Neuroscience Centre and Centre for Pain Research, NCBES, National University of Ireland Galway, Galway, Ireland
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10
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Schafer SM, Geuter S, Wager TD. Mechanisms of placebo analgesia: A dual-process model informed by insights from cross-species comparisons. Prog Neurobiol 2018; 160:101-122. [PMID: 29108801 PMCID: PMC5747994 DOI: 10.1016/j.pneurobio.2017.10.008] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 10/24/2017] [Accepted: 10/28/2017] [Indexed: 12/19/2022]
Abstract
Placebo treatments are pharmacologically inert, but are known to alleviate symptoms across a variety of clinical conditions. Associative learning and cognitive expectations both play important roles in placebo responses, however we are just beginning to understand how interactions between these processes lead to powerful effects. Here, we review the psychological principles underlying placebo effects and our current understanding of their brain bases, focusing on studies demonstrating both the importance of cognitive expectations and those that demonstrate expectancy-independent associative learning. To account for both forms of placebo analgesia, we propose a dual-process model in which flexible, contextually driven cognitive schemas and attributions guide associative learning processes that produce stable, long-term placebo effects. According to this model, the placebo-induction paradigms with the most powerful effects are those that combine reinforcement (e.g., the experience of reduced pain after placebo treatment) with suggestions and context cues that disambiguate learning by attributing perceived benefit to the placebo. Using this model as a conceptual scaffold, we review and compare neurobiological systems identified in both human studies of placebo analgesia and behavioral pain modulation in rodents. We identify substantial overlap between the circuits involved in human placebo analgesia and those that mediate multiple forms of context-based modulation of pain behavior in rodents, including forebrain-brainstem pathways and opioid and cannabinoid systems in particular. This overlap suggests that placebo effects are part of a set of adaptive mechanisms for shaping nociceptive signaling based on its information value and anticipated optimal response in a given behavioral context.
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Affiliation(s)
- Scott M Schafer
- Department of Psychology and Neuroscience, University of Colorado, 345 UCB, Boulder, CO 80309, USA
| | - Stephan Geuter
- Department of Psychology and Neuroscience, University of Colorado, 345 UCB, Boulder, CO 80309, USA; Institute of Cognitive Science, University of Colorado Boulder, 344 UCB, Boulder, CO 80309, USA; Department of Biostatistics, Johns Hopkins University, 615 N Wolfe St, Baltimore, MD 21205, USA
| | - Tor D Wager
- Department of Psychology and Neuroscience, University of Colorado, 345 UCB, Boulder, CO 80309, USA; Institute of Cognitive Science, University of Colorado Boulder, 344 UCB, Boulder, CO 80309, USA.
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11
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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: 174] [Impact Index Per Article: 24.9] [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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12
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Starowicz K, Finn DP. Cannabinoids and Pain: Sites and Mechanisms of Action. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2017; 80:437-475. [PMID: 28826543 DOI: 10.1016/bs.apha.2017.05.003] [Citation(s) in RCA: 91] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The endocannabinoid system, consisting of the cannabinoid1 receptor (CB1R) and cannabinoid2 receptor (CB2R), endogenous cannabinoid ligands (endocannabinoids), and metabolizing enzymes, is present throughout the pain pathways. Endocannabinoids, phytocannabinoids, and synthetic cannabinoid receptor agonists have antinociceptive effects in animal models of acute, inflammatory, and neuropathic pain. CB1R and CB2R located at peripheral, spinal, or supraspinal sites are important targets mediating these antinociceptive effects. The mechanisms underlying the analgesic effects of cannabinoids likely include inhibition of presynaptic neurotransmitter and neuropeptide release, modulation of postsynaptic neuronal excitability, activation of the descending inhibitory pain pathway, and reductions in neuroinflammatory signaling. Strategies to dissociate the psychoactive effects of cannabinoids from their analgesic effects have focused on peripherally restricted CB1R agonists, CB2R agonists, inhibitors of endocannabinoid catabolism or uptake, and modulation of other non-CB1R/non-CB2R targets of cannabinoids including TRPV1, GPR55, and PPARs. The large body of preclinical evidence in support of cannabinoids as potential analgesic agents is supported by clinical studies demonstrating their efficacy across a variety of pain disorders.
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Affiliation(s)
- Katarzyna Starowicz
- Institute of Pharmacology, Polish Academy of Sciences, Laboratory of Pain Pathophysiology, Krakow, Poland
| | - David P Finn
- Pharmacology and Therapeutics, School of Medicine, Galway Neuroscience Centre and Centre for Pain Research, NCBES, National University of Ireland, Galway, Ireland.
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Pharmacological inhibition of FAAH modulates TLR-induced neuroinflammation, but not sickness behaviour: An effect partially mediated by central TRPV1. Brain Behav Immun 2017; 62:318-331. [PMID: 28237711 DOI: 10.1016/j.bbi.2017.02.016] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 02/17/2017] [Accepted: 02/19/2017] [Indexed: 01/08/2023] Open
Abstract
Aberrant activation of toll-like receptors (TLRs), key components of the innate immune system, has been proposed to underlie and exacerbate a range of central nervous system disorders. Increasing evidence supports a role for the endocannabinoid system in modulating inflammatory responses including those mediated by TLRs, and thus this system may provide an important treatment target for neuroinflammatory disorders. However, the effect of modulating endocannabinoid tone on TLR-induced neuroinflammation in vivo and associated behavioural changes is largely unknown. The present study examined the effect of inhibiting fatty acid amide hydrolyase (FAAH), the primary enzyme responsible for the metabolism of anandamide (AEA), in vivo on TLR4-induced neuroimmune and behavioural responses, and evaluated sites and mechanisms of action. Systemic administration of the FAAH inhibitor PF3845 increased levels of AEA, and related FAAH substrates N-oleoylethanolamide (OEA) and N-palmitoylethanolamide (PEA), in the frontal cortex and hippocampus of rats, an effect associated with an attenuation in the expression of pro- and anti-inflammatory cytokines and mediators measured 2hrs following systemic administration of the TLR4 agonist, lipopolysaccharide (LPS). These effects were mimicked by central i.c.v. administration of PF3845, but not systemic administration of the peripherally-restricted FAAH inhibitor URB937. Central antagonism of TRPV1 significantly attenuated the PF3845-induced decrease in IL-6 expression, effects not observed following antagonism of CB1, CB2, PPARα, PPARγ or GPR55. LPS-induced a robust sickness-like behavioural response and increased the expression of markers of glial activity and pro-inflammatory cytokines over 24hrs. Systemic administration of PF3845 modulated the TLR4-induced expression of neuroimmune mediators and anhedonia without altering acute sickness behaviour. Overall, these findings support an important role for FAAH substrates directly within the brain in the regulation of TLR4-associated neuroinflammation and highlight a role for TRPV1 in partially mediating these effects.
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Okine BN, Gaspar JC, Madasu MK, Olango WM, Harhen B, Roche M, Finn DP. Characterisation of peroxisome proliferator-activated receptor signalling in the midbrain periaqueductal grey of rats genetically prone to heightened stress, negative affect and hyperalgesia. Brain Res 2016; 1657:185-192. [PMID: 27916440 DOI: 10.1016/j.brainres.2016.11.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Revised: 11/12/2016] [Accepted: 11/19/2016] [Indexed: 10/20/2022]
Abstract
The stress-hyperresponsive Wistar-Kyoto (WKY) rat strain exhibits a hyperalgesic phenotype and is a useful genetic model for studying stress-pain interactions. Peroxisome proliferator-activated receptor (PPAR) signalling in the midbrain periaqueductal grey (PAG) modulates pain. This study characterised PPAR signalling in the PAG of WKY rats exposed to the formalin test of inflammatory pain, versus Sprague-Dawley (SD) controls. Formalin injection reduced levels of the endogenous PPAR ligands N-palmitoylethanolamide (PEA) and N-oleoylethanolamide (OEA) in the lateral(l) PAG of SD rats, but not WKY rats which exhibited higher levels of these analytes compared with formalin-injected SD counterparts. Levels of mRNA coding for fatty acid amide hydrolase (FAAH; catabolises PEA and OEA) were lower in the lPAG of WKY versus SD rats. PPARγ mRNA and protein levels in the lPAG were higher in saline-treated WKY rats, with PPARγ protein levels reduced by formalin treatment in WKY rats only. In the dorsolateral(dl) or ventrolateral(vl) PAG, there were no effects of formalin injection on PEA or OEA levels but there were some differences in levels of these analytes between saline-treated WKY and SD rats and some formalin-evoked alterations in levels of PPARα, PPARγ or FAAH mRNA in WKY and/or SD rats. Pharmacological blockade of PPARγ in the lPAG enhanced formalin-evoked nociceptive behaviour in WKY, but not SD, rats. These data indicate differences in the PPAR signalling system in the PAG of WKY versus SD rats and suggest that enhanced PEA/OEA-mediated tone at PPARγ in the lPAG may represent an adaptive mechanism to lower hyperalgesia in WKY rats.
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Affiliation(s)
- Bright N Okine
- Pharmacology and Therapeutics, Galway Neuroscience Centre and Centre for Pain Research, NCBES, National University of Ireland Galway, University Road, Galway, Ireland; Galway Neuroscience Centre and Centre for Pain Research, NCBES, National University of Ireland Galway, University Road, Galway, Ireland
| | - Jessica C Gaspar
- Pharmacology and Therapeutics, Galway Neuroscience Centre and Centre for Pain Research, NCBES, National University of Ireland Galway, University Road, Galway, Ireland; Galway Neuroscience Centre and Centre for Pain Research, NCBES, National University of Ireland Galway, University Road, Galway, Ireland
| | - Manish K Madasu
- Pharmacology and Therapeutics, Galway Neuroscience Centre and Centre for Pain Research, NCBES, National University of Ireland Galway, University Road, Galway, Ireland; Galway Neuroscience Centre and Centre for Pain Research, NCBES, National University of Ireland Galway, University Road, Galway, Ireland
| | - Weredeselam M Olango
- Pharmacology and Therapeutics, Galway Neuroscience Centre and Centre for Pain Research, NCBES, National University of Ireland Galway, University Road, Galway, Ireland; Galway Neuroscience Centre and Centre for Pain Research, NCBES, National University of Ireland Galway, University Road, Galway, Ireland
| | - Brendan Harhen
- Galway Neuroscience Centre and Centre for Pain Research, NCBES, National University of Ireland Galway, University Road, Galway, Ireland
| | - Michelle Roche
- Physiology, School of Medicine, Galway Neuroscience Centre and Centre for Pain Research, NCBES, National University of Ireland Galway, University Road, Galway, Ireland; Galway Neuroscience Centre and Centre for Pain Research, NCBES, National University of Ireland Galway, University Road, Galway, Ireland
| | - David P Finn
- Pharmacology and Therapeutics, Galway Neuroscience Centre and Centre for Pain Research, NCBES, National University of Ireland Galway, University Road, Galway, Ireland; Galway Neuroscience Centre and Centre for Pain Research, NCBES, National University of Ireland Galway, University Road, Galway, Ireland.
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Szűcs E, Büki A, Kékesi G, Horváth G, Benyhe S. Mu-Opioid (MOP) receptor mediated G-protein signaling is impaired in specific brain regions in a rat model of schizophrenia. Neurosci Lett 2016; 619:29-33. [PMID: 26946106 DOI: 10.1016/j.neulet.2016.02.060] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2016] [Revised: 02/16/2016] [Accepted: 02/29/2016] [Indexed: 12/20/2022]
Abstract
Schizophrenia is a complex mental health disorder. Clinical reports suggest that many patients with schizophrenia are less sensitive to pain than other individuals. Animal models do not interpret schizophrenia completely, but they can model a number of symptoms of the disease, including decreased pain sensitivities and increased pain thresholds of various modalities. Opioid receptors and endogenous opioid peptides have a substantial role in analgesia. In this biochemical study we investigated changes in the signaling properties of the mu-opioid (MOP) receptor in different brain regions, which are involved in the pain transmission, i.e., thalamus, olfactory bulb, prefrontal cortex and hippocampus. Our goal was to compare the transmembrane signaling mediated by MOP receptors in control rats and in a recently developed rat model of schizophrenia. Regulatory G-protein activation via MOP receptors were measured in [(35)S]GTPγS binding assays in the presence of a highly selective MOP receptor peptide agonist, DAMGO. It was found that the MOP receptor mediated activation of G-proteins was substantially lower in membranes prepared from the 'schizophrenic' model rats than in control animals. The potency of DAMGO to activate MOP receptor was also decreased in all brain regions studied. Taken together in our rat model of schizophrenia, MOP receptor mediated G-proteins have a reduced stimulatory activity compared to membrane preparations taken from control animals. The observed distinct changes of opioid receptor functions in different areas of the brain do not explain the augmented nociceptive threshold described in these animals.
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Affiliation(s)
- Edina Szűcs
- Institute of Biochemistry, Biological Research Center, Hungarian Academy of Sciences, H-6726 Szeged, Temesvári krt. 62., Hungary
| | - Alexandra Büki
- Department of Physiology, Faculty of Medicine, University of Szeged, H-6720 Szeged, Dóm tér 10., Hungary
| | - Gabriella Kékesi
- Department of Physiology, Faculty of Medicine, University of Szeged, H-6720 Szeged, Dóm tér 10., Hungary
| | - Gyöngyi Horváth
- Department of Physiology, Faculty of Medicine, University of Szeged, H-6720 Szeged, Dóm tér 10., Hungary
| | - Sándor Benyhe
- Institute of Biochemistry, Biological Research Center, Hungarian Academy of Sciences, H-6726 Szeged, Temesvári krt. 62., Hungary.
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16
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Repeated forced swim stress differentially affects formalin-evoked nociceptive behaviour and the endocannabinoid system in stress normo-responsive and stress hyper-responsive rat strains. Prog Neuropsychopharmacol Biol Psychiatry 2016; 64:181-9. [PMID: 25988529 DOI: 10.1016/j.pnpbp.2015.05.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Revised: 05/09/2015] [Accepted: 05/11/2015] [Indexed: 01/18/2023]
Abstract
Repeated exposure to a homotypic stressor such as forced swimming enhances nociceptive responding in rats. However, the influence of genetic background on this stress-induced hyperalgesia is poorly understood. The aim of the present study was to compare the effects of repeated forced swim stress on nociceptive responding in Sprague-Dawley (SD) rats versus the Wistar Kyoto (WKY) rat strain, a genetic background that is susceptible to stress, negative affect and hyperalgesia. Given the well-documented role of the endocannabinoid system in stress and pain, we investigated associated alterations in endocannabinoid signalling in the dorsal horn of the spinal cord and amygdala. In SD rats, repeated forced swim stress for 10 days was associated with enhanced late phase formalin-evoked nociceptive behaviour, compared with naive, non-stressed SD controls. In contrast, WKY rats exposed to 10 days of swim stress displayed reduced late phase formalin-evoked nociceptive behaviour. Swim stress increased levels of monoacylglycerol lipase (MAGL) mRNA in the ipsilateral side of the dorsal spinal cord of SD rats, an effect not observed in WKY rats. In the amygdala, swim stress reduced anandamide (AEA) levels in the contralateral amygdala of SD rats, but not WKY rats. Additional within-strain differences in levels of CB1 receptor and fatty acid amide hydrolase (FAAH) mRNA and levels of 2-arachidonylglycerol (2-AG) were observed between the ipsilateral and contralateral sides of the dorsal horn and/or amygdala. These data indicate that the effects of repeated stress on inflammatory pain-related behaviour are different in two rat strains that differ with respect to stress responsivity and affective state and implicate the endocannabinoid system in the spinal cord and amygdala in these differences.
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17
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Differential upregulation of the cannabinoid CB₂ receptor in neurotoxic and inflammation-driven rat models of Parkinson's disease. Exp Neurol 2015; 269:133-41. [PMID: 25895887 DOI: 10.1016/j.expneurol.2015.04.007] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Revised: 04/08/2015] [Accepted: 04/11/2015] [Indexed: 11/24/2022]
Abstract
The cannabinoid CB2 receptor has recently emerged as a potential anti-inflammatory target to break the self-sustaining cycle of neuroinflammation and neurodegeneration that is associated with neurodegenerative diseases. However, in order to facilitate the development of cannabinoid drugs for neurodegenerative disease, the changes that occur in the endocannabinoid system in response to different neurodegenerative triggers needs to be elucidated. Therefore, the aim of this study was to investigate and compare the changes that occur in the endocannabinoid system in neurotoxic and inflammation-driven models of Parkinson's disease. To do so, male Sprague Dawley rats were given unilateral, intra-striatal injections of the dopaminergic neurotoxin, 6-hydroxydopamine, or the bacterial inflammagen, lipopolysaccharide (LPS). Animals underwent behavioural testing for motor dysfunction on Days 7, 14 and 28 post-surgery, and were sacrificed on Days 1, 4, 14 and 28. Changes in the endocannabinoid system were investigated by qRT-PCR, liquid chromatography-mass spectrometry and immunohistochemistry. After injection of 6-hydroxydopamine or LPS into the rat striatum, we found that expression of the CB2 receptor was significantly elevated in both models, and that this increase correlated significantly with an increase in microglial activation. Interestingly, the increase in CB2 receptor expression in the inflammation-driven model was significantly more pronounced than that in the neurotoxic model. Moreover, endocannabinoid levels were also elevated in the LPS model but not the 6-hydroxydopamine model. Thus, this study has shown that the endocannabinoid system is dysregulated in animal models of Parkinson's disease, and has also revealed significant differences in the level of dysregulation between the models themselves. This study indicates that targeting the CB2 receptor may represent a viable target for anti-inflammatory disease modification in Parkinson's disease.
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18
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Corcoran L, Roche M, Finn DP. The Role of the Brain's Endocannabinoid System in Pain and Its Modulation by Stress. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2015; 125:203-55. [DOI: 10.1016/bs.irn.2015.10.003] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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19
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Ford GK, Moriarty O, Okine BN, Tully E, Mulcahy A, Harhen B, Finn DP. Involvement of the endocannabinoid system in attentional modulation of nociceptive behaviour in rats. Eur J Pain 2014; 19:1177-85. [PMID: 25504741 DOI: 10.1002/ejp.646] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/15/2014] [Indexed: 12/11/2022]
Abstract
BACKGROUND Distraction is used clinically to relieve and manage pain. It is hypothesized that pain demands attention and that exposure to another attention-demanding stimulus causes withdrawal of attention away from painful stimuli, thereby reducing perceived pain. We have recently developed a rat model that provides an opportunity to investigate the neurobiological mechanisms mediating distraction-induced analgesia, as these mechanisms are, at present, poorly understood. Given the well-described role of the endogenous cannabinoid (endocannabinoid; EC) system in the modulation of pain and attentional processing, the present study investigated its role in distraction-induced antinociception in rats. METHODS Animals received the CB1 receptor antagonist/inverse agonist, rimonabant or vehicle intraperitoneally, 30 min prior to behavioural evaluation. Formalin-evoked nociceptive behaviour was measured in the presence or absence of a novel-object distractor. Liquid chromatography-tandem mass spectrometry was used to determine the levels of the endogenous cannabinoids anandamide and 2-arachidonoylglycerol (2-AG) in the ventral hippocampus (vHip). RESULTS Exposure to a novel object distractor significantly reduced formalin-evoked nociceptive behaviour. The novel object-induced reduction in nociceptive behaviour was attenuated by rimonabant. Novel object exposure was also associated with increased tissue levels of anandamide and 2-AG in the vHip. CONCLUSIONS These data suggest that the reduction in formalin-evoked nociceptive behaviour that occurs as a result of exposure to a novel object may be mediated by engagement of the EC system, in particular in the vHip. The results provide evidence that the EC system may be an important neural substrate subserving attentional modulation of pain.
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Affiliation(s)
- G K Ford
- Pharmacology and Therapeutics, School of Medicine, National University of Ireland, Galway.,NCBES Neuroscience Centre, National University of Ireland, Galway.,Centre for Pain Research, National University of Ireland, Galway
| | - O Moriarty
- Pharmacology and Therapeutics, School of Medicine, National University of Ireland, Galway.,NCBES Neuroscience Centre, National University of Ireland, Galway.,Centre for Pain Research, National University of Ireland, Galway
| | - B N Okine
- Pharmacology and Therapeutics, School of Medicine, National University of Ireland, Galway.,NCBES Neuroscience Centre, National University of Ireland, Galway.,Centre for Pain Research, National University of Ireland, Galway
| | - E Tully
- Pharmacology and Therapeutics, School of Medicine, National University of Ireland, Galway
| | - A Mulcahy
- Pharmacology and Therapeutics, School of Medicine, National University of Ireland, Galway
| | - B Harhen
- NCBES Neuroscience Centre, National University of Ireland, Galway.,Centre for Pain Research, National University of Ireland, Galway
| | - D P Finn
- Pharmacology and Therapeutics, School of Medicine, National University of Ireland, Galway.,NCBES Neuroscience Centre, National University of Ireland, Galway.,Centre for Pain Research, National University of Ireland, Galway
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Kerr DM, Harhen B, Okine BN, Egan LJ, Finn DP, Roche M. The monoacylglycerol lipase inhibitor JZL184 attenuates LPS-induced increases in cytokine expression in the rat frontal cortex and plasma: differential mechanisms of action. Br J Pharmacol 2014; 169:808-19. [PMID: 23043675 DOI: 10.1111/j.1476-5381.2012.02237.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2012] [Revised: 08/31/2012] [Accepted: 09/05/2012] [Indexed: 01/24/2023] Open
Abstract
BACKGROUND AND PURPOSE JZL184 is a selective inhibitor of monoacylglycerol lipase (MAGL), the enzyme that preferentially catabolizes the endocannabinoid 2-arachidonoyl glycerol (2-AG). Here, we have studied the effects of JZL184 on inflammatory cytokines in the brain and plasma following an acute immune challenge and the underlying receptor and molecular mechanisms involved. EXPERIMENTAL APPROACH JZL184 and/or the CB₁ receptor antagonist, AM251 or the CB₂ receptor antagonist, AM630 were administered to rats 30 min before lipopolysaccharide (LPS). 2 h later cytokine expression and levels, MAGL activity, 2-AG, arachidonic acid and prostaglandin levels were measured in the frontal cortex, plasma and spleen. KEY RESULTS JZL184 attenuated LPS-induced increases in IL-1β, IL-6, TNF-α and IL-10 but not the expression of the inhibitor of NFkB (IκBα) in rat frontal cortex. AM251 attenuated JZL184-induced decreases in frontal cortical IL-1β expression. Although arachidonic acid levels in the frontal cortex were reduced in JZL184-treated rats, MAGL activity, 2-AG, PGE₂ and PGD₂ were unchanged. In comparison, MAGL activity was inhibited and 2-AG levels enhanced in the spleen following JZL184. In plasma, LPS-induced increases in TNF-α and IL-10 levels were attenuated by JZL184, an effect partially blocked by AM251. In addition, AM630 blocked LPS-induced increases in plasma IL-1β in the presence, but not absence, of JZL184. CONCLUSION AND IMPLICATIONS Inhibition of peripheral MAGL in rats by JZL184 suppressed LPS-induced circulating cytokines that in turn may modulate central cytokine expression. The data provide further evidence for the endocannabinoid system as a therapeutic target in treatment of central and peripheral inflammatory disorders.
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Affiliation(s)
- D M Kerr
- Physiology, School of Medicine, National University of Ireland, Galway, Ireland
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21
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Rea K, Ford GK, Olango WM, Harhen B, Roche M, Finn DP. Microinjection of 2-arachidonoyl glycerol into the rat ventral hippocampus differentially modulates contextually induced fear, depending on a persistent pain state. Eur J Neurosci 2014; 39:435-43. [PMID: 24494683 DOI: 10.1111/ejn.12452] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 11/09/2013] [Accepted: 11/11/2013] [Indexed: 12/19/2022]
Abstract
The endogenous cannabinoid (endocannabinoid) system plays a key role in the modulation of aversive and nociceptive behaviour. The components of the endocannabinoid system are expressed throughout the hippocampus, a brain region implicated in both conditioned fear and pain. In light of evidence that pain can impact on the expression of fear-related behaviour, and vice versa, we hypothesised that exogenous administration of the endocannabinoid 2-arachidonoyl glycerol (2-AG) into the ventral hippocampus (vHip) would differentially regulate fear responding in the absence vs. the presence of formalin-evoked nociceptive tone. Fear-conditioned rats showed significantly increased freezing and a reduction in formalin-evoked nociceptive behaviour upon re-exposure to a context previously paired with footshock. Bilateral microinjection of 2-AG into the vHip significantly reduced contextually induced freezing in non-formalin-treated rats, and reduced formalin-evoked nociceptive behaviour in non-fear-conditioned rats. In contrast, 2-AG microinjection had no effect on fear responding in formalin-treated rats, and no effect on nociceptive behaviour in fear-conditioned rats. The inhibitory effect of 2-AG on fear-related behaviour, but not pain-related behaviour, was blocked by co-administration of the cannabinoid receptor 1 (CB1) antagonist/inverse agonist rimonabant. Tissue levels of the endocannabinoids N-arachidonoylethanolamide (anandamide, AEA) and 2-AG were similar in the vHip of fear-conditioned rats receiving formalin injection and the vHip of fear-conditioned rats receiving saline injection. However, the levels of AEA and 2-AG were significantly lower in the contralateral ventrolateral periaqueductal grey of formalin-treated fear-conditioned rats than in that of their saline-treated counterparts. These data suggest that 2-AG-CB1 receptor signalling in the vHip has an anti-aversive effect, and that this effect is abolished in the presence of a persistent pain state.
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Affiliation(s)
- Kieran Rea
- Pharmacology and Therapeutics, School of Medicine, National University of Ireland, University Road, Galway, Ireland; Galway Neuroscience Centre and Centre for Pain Research, NCBES, National University of Ireland, Galway, Ireland
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Rea K, Olango WM, Okine BN, Madasu MK, McGuire IC, Coyle K, Harhen B, Roche M, Finn DP. Impaired endocannabinoid signalling in the rostral ventromedial medulla underpins genotype-dependent hyper-responsivity to noxious stimuli. Pain 2014; 155:69-79. [DOI: 10.1016/j.pain.2013.09.012] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2013] [Revised: 08/18/2013] [Accepted: 09/09/2013] [Indexed: 12/20/2022]
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23
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Akirav I. Cannabinoids and glucocorticoids modulate emotional memory after stress. Neurosci Biobehav Rev 2013; 37:2554-63. [PMID: 23954749 DOI: 10.1016/j.neubiorev.2013.08.002] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Revised: 06/16/2013] [Accepted: 08/04/2013] [Indexed: 12/17/2022]
Abstract
Bidirectional and functional relationships between glucocorticoids and the endocannabinoid system have been demonstrated. Here, I review the interaction between the endocannabinoid and glucocorticoid/stress systems. Specifically, stress is known to produce rapid changes in endocannabinoid signaling in stress-responsive brain regions. In turn, the endocannabinoid system plays an important role in the downregulation and habituation of hypothalamic-pituitary-adrenocortical (HPA) axis activity in response to stress. Glucocorticoids also recruit the endocannabinoid system to exert rapid negative feedback control of the HPA axis during stress. It became increasingly clear, however, that cannabinoid CB1 receptors are also abundantly expressed in the basolateral amygdala (BLA) and other limbic regions where they modulate emotional arousal effects on memory. Enhancing cannabinoids signaling using exogenous CB1 receptor agonists prevent the effects of acute stress on emotional memory. I propose a model suggesting that the ameliorating effects of exogenously administered cannabinoids on emotional learning after acute stress are mediated by the decrease in the activity of the HPA axis via GABAergic mechanisms in the amygdala.
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Affiliation(s)
- Irit Akirav
- Department of Psychology, University of Haifa, Haifa 31905, Israel.
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Abd Aziz CB, Ahmad R, Mohamed M, Wan Yusof WN. The effects of Tualang honey intake during prenatal stress on pain responses in the rat offsprings. Eur J Integr Med 2013. [DOI: 10.1016/j.eujim.2013.03.001] [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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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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Kerr DM, Downey L, Conboy M, Finn DP, Roche M. Alterations in the endocannabinoid system in the rat valproic acid model of autism. Behav Brain Res 2013; 249:124-32. [PMID: 23643692 DOI: 10.1016/j.bbr.2013.04.043] [Citation(s) in RCA: 121] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Revised: 04/22/2013] [Accepted: 04/24/2013] [Indexed: 12/17/2022]
Abstract
The endocannabinoid system plays a crucial role in regulating emotionality and social behaviour, however it is unknown whether this system plays a role in symptoms associated with autism spectrum disorders. The current study evaluated if alterations in the endocannabinoid system accompany behavioural changes in the valproic acid (VPA) rat model of autism. Adolescent rats prenatally exposed to VPA exhibited impaired social investigatory behaviour, hypoalgesia and reduced lococmotor activity on exposure to a novel aversive arena. Levels of the endocananbinoids, anandamide (AEA) and 2-arachidonylglycerol (2-AG) in the hippocampus, frontal cortex or cerebellum were not altered in VPA- versus saline-exposed animals. However, the expression of mRNA for diacylglycerol lipase α, the enzyme primarily responsible for the synthesis of 2-AG, was reduced in the cerebellum of VPA-exposed rats. Furthermore, while the expression of mRNA for the 2-AG-catabolising enzyme monoacylglycerol lipase was reduced, the activity of this enzyme was increased, in the hippocampus of VPA-exposed animals. CB1 or CB2 receptor expression was not altered in any of the regions examined, however VPA-exposed rats exhibited reduced PPARα and GPR55 expression in the frontal cortex and PPARγ and GPR55 expression in the hippocampus, additional receptor targets of the endocannabinoids. Furthermore, tissue levels of the fatty acid amide hydrolase substrates, AEA, oleoylethanolamide and palmitoylethanolamide, were higher in the hippocampus of VPA-exposed rats immediately following social exposure. These data indicate that prenatal VPA exposure is associated with alterations in the brain's endocannabinoid system and support the hypothesis that endocannabinoid dysfunction may underlie behavioural abnormalities observed in autism spectrum disorders.
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Affiliation(s)
- D M Kerr
- Physiology, School of Medicine, National University of Ireland Galway, Ireland
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27
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Evidence for a role of GABAergic and glutamatergic signalling in the basolateral amygdala in endocannabinoid-mediated fear-conditioned analgesia in rats. Pain 2013; 154:576-585. [DOI: 10.1016/j.pain.2012.12.021] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Revised: 08/25/2012] [Accepted: 12/20/2012] [Indexed: 12/17/2022]
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28
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Murphy N, Cowley TR, Blau CW, Dempsey CN, Noonan J, Gowran A, Tanveer R, Olango WM, Finn DP, Campbell VA, Lynch MA. The fatty acid amide hydrolase inhibitor URB597 exerts anti-inflammatory effects in hippocampus of aged rats and restores an age-related deficit in long-term potentiation. J Neuroinflammation 2012; 9:79. [PMID: 22537429 PMCID: PMC3409037 DOI: 10.1186/1742-2094-9-79] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Accepted: 04/26/2012] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND Several factors contribute to the deterioration in synaptic plasticity which accompanies age and one of these is neuroinflammation. This is characterized by increased microglial activation associated with increased production of proinflammatory cytokines like interleukin-1β (IL-1β). In aged rats these neuroinflammatory changes are associated with a decreased ability of animals to sustain long-term potentiation (LTP) in the dentate gyrus. Importantly, treatment of aged rats with agents which possess anti-inflammatory properties to decrease microglial activation, improves LTP. It is known that endocannabinoids, such as anandamide (AEA), have anti-inflammatory properties and therefore have the potential to decrease the age-related microglial activation. However, endocannabinoids are extremely labile and are hydrolyzed quickly after production. Here we investigated the possibility that inhibiting the degradation of endocannabinoids with the fatty acid amide hydrolase (FAAH) inhibitor, URB597, could ameliorate age-related increases in microglial activation and the associated decrease in LTP. METHODS Young and aged rats received subcutaneous injections of the FAAH inhibitor URB597 every second day and controls which received subcutaneous injections of 30% DMSO-saline every second day for 28 days. Long-term potentiation was recorded on day 28 and the animals were sacrificed. Brain tissue was analyzed for markers of microglial activation by PCR and for levels of endocannabinoids by liquid chromatography coupled to tandem mass spectrometry. RESULTS The data indicate that expression of markers of microglial activation, MHCII, and CD68 mRNA, were increased in the hippocampus of aged, compared with young, rats and that these changes were associated with increased expression of the proinflammatory cytokines interleukin (IL)-1β and tumor necrosis factor-α (TNFα) which were attenuated by treatment with URB597. Coupled with these changes, we observed an age-related decrease in LTP in the dentate gyrus which was partially restored in URB597-treated aged rats. The data suggest that enhancement of levels of endocannabinoids in the brain by URB597 has beneficial effects on synaptic function, perhaps by modulating microglial activation.
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Affiliation(s)
- Niamh Murphy
- Department of Physiology, Trinity College, Trinity College Institute for Neuroscience, Dublin 2, Ireland.
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