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Role of Cannabinoid CB2 Receptor in Alcohol Use Disorders: From Animal to Human Studies. Int J Mol Sci 2022; 23:ijms23115908. [PMID: 35682586 PMCID: PMC9180470 DOI: 10.3390/ijms23115908] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 05/22/2022] [Accepted: 05/23/2022] [Indexed: 12/04/2022] Open
Abstract
Cumulative evidence has pointed out cannabinoid CB2 receptors (CB2r) as a potential therapeutic key target for treating alcohol use disorder (AUD). This review provides the most relevant results obtained from rodent and human studies, including an integrative section focused on the involvement of CB2r in the neurobiology of alcohol addiction. A literature search was conducted using the electronic databases Medline and Scopus for articles. The search strategy was as follows: “Receptor, Cannabinoid, CB2” AND “Alcohol-Related Disorders” AND “human/or patients”; “Receptor, Cannabinoid, CB2” AND “Alcohol” OR “Ethanol” AND “rodents/or mice/or rats”. Pharmacological approaches demonstrated that the activation or blockade of CB2r modulated different alcohol-addictive behaviors. Rodent models of alcoholism revealed significant alterations of CB2r in brain areas of the reward system. In addition, mice lacking CB2r (CB2KO) show increased alcohol consumption, motivation, and relapse alterations. It has been stressed that the potential neurobiological mechanisms underlying their behavioral effects involve critical elements of the alcohol reward system. Interestingly, recent postmortem studies showed CNR2 alterations in brain areas of alcoholic patients. Moreover, although the number of studies is limited, the results revealed an association between some genetic alterations of the CNR2 and an increased risk for developing AUD. This review provides evidence that CB2r may play a role in alcohol addiction. Clinical studies are necessary to figure out whether CB2r ligands may prove useful for the treatment of AUD in humans.
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Visvanathar R, Papanikolaou M, Nôga DA, Pádua-Reis M, Tort ABL, Blunder M. Hippocampal Cb 2 receptors: an untold story. Rev Neurosci 2021; 33:413-426. [PMID: 34717053 DOI: 10.1515/revneuro-2021-0109] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 10/01/2021] [Indexed: 12/13/2022]
Abstract
The field of cannabinoid research has been receiving ever-growing interest. Ongoing debates worldwide about the legislation of medical cannabis further motivates research into cannabinoid function within the central nervous system (CNS). To date, two well-characterized cannabinoid receptors exist. While most research has investigated Cb1 receptors (Cb1Rs), Cb2 receptors (Cb2Rs) in the brain have started to attract considerable interest in recent years. With indisputable evidence showing the wide-distribution of Cb2Rs in the brain of different species, they are no longer considered just peripheral receptors. However, in contrast to Cb1Rs, the functionality of central Cb2Rs remains largely unexplored. Here we review recent studies on hippocampal Cb2Rs. While conflicting results about their function have been reported, we have made significant progress in understanding the involvement of Cb2Rs in modulating cellular properties and network excitability. Moreover, Cb2Rs have been shown to be expressed in different subregions of the hippocampus, challenging our prior understanding of the endocannabinoid system. Although more insight into their functional roles is necessary, we propose that targeting hippocampal Cb2Rs may offer novel therapies for diseases related to memory and adult neurogenesis deficits.
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Affiliation(s)
- Robin Visvanathar
- Behavioral Neurophysiology, Department of Neuroscience, Biomedical Center, Uppsala University, Husargatan 3, 751 23, Uppsala, Sweden
| | - Maria Papanikolaou
- Behavioral Neurophysiology, Department of Neuroscience, Biomedical Center, Uppsala University, Husargatan 3, 751 23, Uppsala, Sweden
| | - Diana Aline Nôga
- Behavioral Neurophysiology, Department of Neuroscience, Biomedical Center, Uppsala University, Husargatan 3, 751 23, Uppsala, Sweden
| | - Marina Pádua-Reis
- Behavioral Neurophysiology, Department of Neuroscience, Biomedical Center, Uppsala University, Husargatan 3, 751 23, Uppsala, Sweden
| | | | - Martina Blunder
- Behavioral Neurophysiology, Department of Neuroscience, Biomedical Center, Uppsala University, Husargatan 3, 751 23, Uppsala, Sweden
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Morris G, Walder K, Kloiber S, Amminger P, Berk M, Bortolasci CC, Maes M, Puri BK, Carvalho AF. The endocannabinoidome in neuropsychiatry: Opportunities and potential risks. Pharmacol Res 2021; 170:105729. [PMID: 34119623 DOI: 10.1016/j.phrs.2021.105729] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 05/31/2021] [Accepted: 06/09/2021] [Indexed: 02/08/2023]
Abstract
The endocannabinoid system (ECS) comprises two cognate endocannabinoid receptors referred to as CB1R and CB2R. ECS dysregulation is apparent in neurodegenerative/neuro-psychiatric disorders including but not limited to schizophrenia, major depressive disorder and potentially bipolar disorder. The aim of this paper is to review mechanisms whereby both receptors may interact with neuro-immune and neuro-oxidative pathways, which play a pathophysiological role in these disorders. CB1R is located in the presynaptic terminals of GABAergic, glutamatergic, cholinergic, noradrenergic and serotonergic neurons where it regulates the retrograde suppression of neurotransmission. CB1R plays a key role in long-term depression, and, to a lesser extent, long-term potentiation, thereby modulating synaptic transmission and mediating learning and memory. Optimal CB1R activity plays an essential neuroprotective role by providing a defense against the development of glutamate-mediated excitotoxicity, which is achieved, at least in part, by impeding AMPA-mediated increase in intracellular calcium overload and oxidative stress. Moreover, CB1R activity enables optimal neuron-glial communication and the function of the neurovascular unit. CB2R receptors are detected in peripheral immune cells and also in central nervous system regions including the striatum, basal ganglia, frontal cortex, hippocampus, amygdala as well as the ventral tegmental area. CB2R upregulation inhibits the presynaptic release of glutamate in several brain regions. CB2R activation also decreases neuroinflammation partly by mediating the transition from a predominantly neurotoxic "M1" microglial phenotype to a more neuroprotective "M2" phenotype. CB1R and CB2R are thus novel drug targets for the treatment of neuro-immune and neuro-oxidative disorders including schizophrenia and affective disorders.
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Affiliation(s)
- Gerwyn Morris
- Deakin University, IMPACT - the Institute for Mental and Physical Health and Clinical Translation, School of Medicine, Barwon Health, Geelong, Australia
| | - Ken Walder
- Deakin University, IMPACT - the Institute for Mental and Physical Health and Clinical Translation, School of Medicine, Barwon Health, Geelong, Australia; Deakin University, Centre for Molecular and Medical Research, School of Medicine, Geelong, Australia
| | - Stefan Kloiber
- Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, 33 Ursula Franklin Street, Toronto, ON, Canada; Department of Psychiatry, University of Toronto, Toronto, ON, Canada
| | - Paul Amminger
- Orygen, Parkville, Victoria, Australia; Centre for Youth Mental Health, The University of Melbourne, Parkville, Victoria, Australia
| | - Michael Berk
- Deakin University, IMPACT - the Institute for Mental and Physical Health and Clinical Translation, School of Medicine, Barwon Health, Geelong, Australia; Orygen, The National Centre of Excellence in Youth Mental Health, Centre for Youth Mental Health, Florey Institute for Neuroscience and Mental Health and the Department of Psychiatry, The University of Melbourne, Melbourne, Australia
| | - Chiara C Bortolasci
- Deakin University, IMPACT - the Institute for Mental and Physical Health and Clinical Translation, School of Medicine, Barwon Health, Geelong, Australia
| | - Michael Maes
- Deakin University, IMPACT - the Institute for Mental and Physical Health and Clinical Translation, School of Medicine, Barwon Health, Geelong, Australia; Department of Psychiatry, Faculty of Medicine, King Chulalongkorn Memorial Hospital, Bangkok, Thailand; Department of Psychiatry, Medical University of Plovdiv, Plovdiv, Bulgaria
| | | | - Andre F Carvalho
- Deakin University, IMPACT - the Institute for Mental and Physical Health and Clinical Translation, School of Medicine, Barwon Health, Geelong, Australia.
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