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Hadizadeh H, Flores JM, Mayerson T, Worhunsky PD, Potenza MN, Angarita GA. Glutamatergic Agents for the Treatment of Cocaine Use Disorder. Curr Behav Neurosci Rep 2022. [DOI: 10.1007/s40473-022-00252-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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Hámor PU, Schwendt M. Metabotropic Glutamate Receptor Trafficking and its Role in Drug-Induced Neurobehavioral Plasticity. Brain Plast 2021; 7:61-76. [PMID: 34868874 PMCID: PMC8609495 DOI: 10.3233/bpl-210120] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/06/2021] [Indexed: 12/18/2022] Open
Abstract
Glutamate is the major excitatory neurotransmitter in the mammalian central nervous system that guides developmental and experience-dependent changes in many cellular substrates and brain circuits, through the process collectively referred to as neurobehavioral plasticity. Regulation of cell surface expression and membrane trafficking of glutamate receptors represents an important mechanism that assures optimal excitatory transmission, and at the same time, also allows for fine-tuning neuronal responses to glutamate. On the other hand, there is growing evidence implicating dysregulated glutamate receptor trafficking in the pathophysiology of several neuropsychiatric disorders. This review provides up-to-date information on the molecular determinants regulating trafficking and surface expression of metabotropic glutamate (mGlu) receptors in the rodent and human brain and discusses the role of mGluR trafficking in maladaptive synaptic plasticity produced by addictive drugs. As substantial evidence links glutamatergic dysfunction to the progression and the severity of drug addiction, advances in our understanding of mGluR trafficking may provide opportunities for the development of novel pharmacotherapies of addiction and other neuropsychiatric disorders.
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Affiliation(s)
- Peter U. Hámor
- Department of Psychology, University of Florida, Gainesville, FL, USA
- Center for Addiction Research and Education, University of Florida, Gainesville, FL, USA
| | - Marek Schwendt
- Department of Psychology, University of Florida, Gainesville, FL, USA
- Center for Addiction Research and Education, University of Florida, Gainesville, FL, USA
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Loweth JA, Reimers JM, Caccamise A, Stefanik MT, Woo KKY, Chauhan NM, Werner CT, Wolf ME. mGlu1 tonically regulates levels of calcium-permeable AMPA receptors in cultured nucleus accumbens neurons through retinoic acid signaling and protein translation. Eur J Neurosci 2018; 50:2590-2601. [PMID: 30222904 DOI: 10.1111/ejn.14151] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Revised: 08/22/2018] [Accepted: 08/28/2018] [Indexed: 12/24/2022]
Abstract
In several brain regions, ongoing metabotropic glutamate receptor 1 (mGlu1) transmission has been shown to tonically suppress synaptic levels of Ca2+ -permeable AMPA receptors (CP-AMPARs) while pharmacological activation of mGlu1 removes CP-AMPARs from these synapses. Consistent with this, we previously showed in nucleus accumbens (NAc) medium spiny neurons (MSNs) that reduced mGlu1 tone enables and mGlu1 positive allosteric modulation reverses the elevation of CP-AMPAR levels in the NAc that underlies enhanced cocaine craving in the "incubation of craving" rat model of addiction. To better understand mGlu1/CP-AMPAR interactions, we used a NAc/prefrontal cortex co-culture system in which NAc MSNs express high CP-AMPAR levels, providing an in vitro model for NAc MSNs after the incubation of cocaine craving. The non-specific group I orthosteric agonist dihydroxyphenylglycine (10 min) decreased cell surface GluA1 but not GluA2, indicating CP-AMPAR internalization. This was prevented by mGlu1 (LY367385) or mGlu5 (MTEP) blockade. However, a selective role for mGlu1 emerged in studies of long-term antagonist treatment. Thus, LY367385 (24 hr) increased surface GluA1 without affecting GluA2, whereas MTEP (24 hr) had no effect. In hippocampal neurons, scaling up of CP-AMPARs can occur through a mechanism requiring retinoic acid (RA) signaling and new GluA1 synthesis. Consistent with this, the LY367385-induced increase in surface GluA1 was blocked by anisomycin (translation inhibitor) or 4-(diethylamino)-benzaldehyde (RA synthesis inhibitor). Thus, mGlu1 transmission tonically suppresses cell surface CP-AMPAR levels, and decreasing mGlu1 tone increases surface CP-AMPARs via RA signaling and protein translation. These results identify a novel mechanism for homeostatic plasticity in NAc MSNs.
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Affiliation(s)
- Jessica A Loweth
- Department of Neuroscience, The Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois
| | - Jeremy M Reimers
- Department of Neuroscience, The Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois
| | - Aaron Caccamise
- Department of Neuroscience, The Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois
| | - Michael T Stefanik
- Department of Neuroscience, The Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois
| | - Kenneth Kin Yan Woo
- Department of Neuroscience, The Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois
| | - Nirav M Chauhan
- Department of Neuroscience, The Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois
| | - Craig T Werner
- Department of Neuroscience, The Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois
| | - Marina E Wolf
- Department of Neuroscience, The Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois
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Li X, Peng XQ, Jordan CJ, Li J, Bi GH, He Y, Yang HJ, Zhang HY, Gardner EL, Xi ZX. mGluR5 antagonism inhibits cocaine reinforcement and relapse by elevation of extracellular glutamate in the nucleus accumbens via a CB1 receptor mechanism. Sci Rep 2018; 8:3686. [PMID: 29487381 PMCID: PMC5829076 DOI: 10.1038/s41598-018-22087-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 02/16/2018] [Indexed: 12/02/2022] Open
Abstract
Metabotropic glutamate receptor 5 (mGluR5) antagonism inhibits cocaine self-administration and reinstatement of drug-seeking behavior. However, the cellular and molecular mechanisms underlying this action are poorly understood. Here we report a presynaptic glutamate/cannabinoid mechanism that may underlie this action. Systemic or intra-nucleus accumbens (NAc) administration of the mGluR5 antagonist 2-methyl-6-(phenylethynyl)-pyridine (MPEP) dose-dependently reduced cocaine (and sucrose) self-administration and cocaine-induced reinstatement of drug-seeking behavior. The reduction in cocaine-taking and cocaine-seeking was associated with a reduction in cocaine-enhanced extracellular glutamate, but not cocaine-enhanced extracellular dopamine (DA) in the NAc. MPEP alone, when administered systemically or locally into the NAc, elevated extracellular glutamate, but not DA. Similarly, the cannabinoid CB1 receptor antagonist, rimonabant, elevated NAc glutamate, not DA. mGluR5s were found mainly in striatal medium-spiny neurons, not in astrocytes, and MPEP-enhanced extracellular glutamate was blocked by a NAc CB1 receptor antagonist or N-type Ca++ channel blocker, suggesting that a retrograde endocannabinoid-signaling mechanism underlies MPEP-induced glutamate release. This interpretation was further supported by our findings that genetic deletion of CB1 receptors in CB1-knockout mice blocked both MPEP-enhanced extracellular glutamate and MPEP-induced reductions in cocaine self-administration. Together, these results indicate that the therapeutic anti-cocaine effects of mGluR5 antagonists are mediated by elevation of extracellular glutamate in the NAc via an endocannabinoid-CB1 receptor disinhibition mechanism.
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Affiliation(s)
- Xia Li
- Department of Psychiatry, School of Medicine, University of California San Diego, La Jolla, CA, 92093, USA. .,Molecular Targets and Medications Discovery Branch, Intramural Research Program, National Institute on Drug Abuse, Baltimore, MD, 21224, USA.
| | - Xiao-Qing Peng
- Molecular Targets and Medications Discovery Branch, Intramural Research Program, National Institute on Drug Abuse, Baltimore, MD, 21224, USA.,Psychiatry Residency Training Program, Department of Behavioral Health, Saint Elizabeths Hospital, 1100 Alabama Ave. SE, Washington, DC, 20032, USA
| | - Chloe J Jordan
- Molecular Targets and Medications Discovery Branch, Intramural Research Program, National Institute on Drug Abuse, Baltimore, MD, 21224, USA
| | - Jie Li
- Department of Psychiatry, School of Medicine, University of California San Diego, La Jolla, CA, 92093, USA.,Molecular Targets and Medications Discovery Branch, Intramural Research Program, National Institute on Drug Abuse, Baltimore, MD, 21224, USA
| | - Guo-Hua Bi
- Molecular Targets and Medications Discovery Branch, Intramural Research Program, National Institute on Drug Abuse, Baltimore, MD, 21224, USA
| | - Yi He
- Molecular Targets and Medications Discovery Branch, Intramural Research Program, National Institute on Drug Abuse, Baltimore, MD, 21224, USA
| | - Hong-Ju Yang
- Molecular Targets and Medications Discovery Branch, Intramural Research Program, National Institute on Drug Abuse, Baltimore, MD, 21224, USA
| | - Hai-Ying Zhang
- Molecular Targets and Medications Discovery Branch, Intramural Research Program, National Institute on Drug Abuse, Baltimore, MD, 21224, USA
| | - Eliot L Gardner
- Molecular Targets and Medications Discovery Branch, Intramural Research Program, National Institute on Drug Abuse, Baltimore, MD, 21224, USA
| | - Zheng-Xiong Xi
- Molecular Targets and Medications Discovery Branch, Intramural Research Program, National Institute on Drug Abuse, Baltimore, MD, 21224, USA.
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Torkzaban M, Zendehdel M, Babapour V, Panahi N, Hassanpour S. Interaction Between Central Opioidergic and Glutamatergic Systems on Food Intake in Neonatal Chicks: Role of NMDA, AMPA and mGLU1 Receptors. Int J Pept Res Ther 2017. [DOI: 10.1007/s10989-017-9601-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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Jong YJI, Sergin I, Purgert CA, O'Malley KL. Location-dependent signaling of the group 1 metabotropic glutamate receptor mGlu5. Mol Pharmacol 2014; 86:774-85. [PMID: 25326002 DOI: 10.1124/mol.114.094763] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Although G protein-coupled receptors are primarily known for converting extracellular signals into intracellular responses, some receptors, such as the group 1 metabotropic glutamate receptor, mGlu5, are also localized on intracellular membranes where they can mediate both overlapping and unique signaling effects. Thus, besides "ligand bias," whereby a receptor's signaling modality can shift from G protein dependence to independence, canonical mGlu5 receptor signaling can also be influenced by "location bias" (i.e., the particular membrane and/or cell type from which it signals). Because mGlu5 receptors play important roles in both normal development and in disorders such as Fragile X syndrome, autism, epilepsy, addiction, anxiety, schizophrenia, pain, dyskinesias, and melanoma, a large number of drugs are being developed to allosterically target this receptor. Therefore, it is critical to understand how such drugs might be affecting mGlu5 receptor function on different membranes and in different brain regions. Further elucidation of the site(s) of action of these drugs may determine which signal pathways mediate therapeutic efficacy.
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Affiliation(s)
- Yuh-Jiin I Jong
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri
| | - Ismail Sergin
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri
| | - Carolyn A Purgert
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri
| | - Karen L O'Malley
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri
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Abstract
Metabotropic glutamate receptor 5 (mGluR5) is widely expressed throughout the CNS and participates in regulating neuronal function and synaptic transmission. Recent work in the striatum led to the groundbreaking discovery that intracellular mGluR5 activation drives unique signaling pathways, including upregulation of ERK1/2, Elk-1 (Jong et al., 2009) and Arc (Kumar et al., 2012). To determine whether mGluR5 signals from intracellular membranes of other cell types, such as excitatory pyramidal neurons in the hippocampus, we used dissociated rat CA1 hippocampal cultures and slice preparations to localize and characterize endogenous receptors. As in the striatum, CA1 neurons exhibited an abundance of mGluR5 both on the cell surface and intracellular membranes, including the endoplasmic reticulum and the nucleus where it colocalized with the sodium-dependent excitatory amino acid transporter, EAAT3. Inhibition of EAAT3 or sodium-free buffer conditions prevented accumulations of radiolabeled agonist. Using a pharmacological approach to isolate different pools of mGluR5, both intracellular and cell surface receptors induced oscillatory Ca(2+) responses in dissociated CA1 neurons; however, only intracellular mGluR5 activation triggered sustained high amplitude Ca(2+) rises in dendrites. Consistent with the notion that mGluR5 can signal from intracellular membranes, uncaging glutamate on a CA1 dendrite led to a local Ca(2+) rise, even in the presence of ionotropic and cell surface metabotropic receptor inhibitors. Finally, activation of intracellular mGluR5 alone mediated both electrically induced and chemically induced long-term depression, but not long-term potentiation, in acute hippocampal slices. These data suggest a physiologically relevant and important role for intracellular mGluR5 in hippocampal synaptic plasticity.
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Keck TM, Zou MF, Bi GH, Zhang HY, Wang XF, Yang HJ, Srivastava R, Gardner EL, Xi ZX, Newman AH. A novel mGluR5 antagonist, MFZ 10-7, inhibits cocaine-taking and cocaine-seeking behavior in rats. Addict Biol 2014; 19:195-209. [PMID: 24001208 DOI: 10.1111/adb.12086] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Pre-clinical studies suggest that negative allosteric modulators (NAMs) of the metabotropic glutamate receptor subtype 5 (mGluR5), including 2-methyl-6-(phenylethynyl)pyridine (MPEP), 3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]pyridine (MTEP) and fenobam are highly effective in attenuating drug-taking and drug-seeking behaviors. However, both MPEP and MTEP have no translational potential for use in humans because of their off-target effects and short half-lives. Here, we report that 3-fluoro-5-[(6-methylpyridin-2-yl)ethynyl]benzonitrile (MFZ 10-7), a novel mGluR5 NAM, is more potent and selective than MPEP, MTEP and fenobam in both in vitro binding and functional assays. Similar to MTEP, intraperitoneal administration of MFZ 10-7 inhibited intravenous cocaine self-administration, cocaine-induced reinstatement of drug-seeking behavior and cocaine-associated cue-induced cocaine-seeking behavior in rats. Although MFZ 10-7 and MTEP lowered the rate of oral sucrose self-administration, they did not alter total sucrose intake. Further, MFZ 10-7 appeared to be more potent than MTEP in inducing downward shifts in the cocaine dose-response curve, but less effective than MTEP in attenuating sucrose-induced reinstatement of sucrose-seeking behavior. MFZ 10-7 and MTEP had no effect on basal locomotor behavior. These findings not only provide additional evidence supporting an important role for mGluR5 in cocaine reward and addiction, but also introduce a new tool for both in vitro and in vivo investigations with which to further characterize this role.
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Affiliation(s)
- Thomas M. Keck
- Medicinal Chemistry Section; Molecular Targets and Medications Discovery Branch; National Institute on Drug Abuse. NIH, DHHS; Baltimore MD USA
| | - Mu-Fa Zou
- Medicinal Chemistry Section; Molecular Targets and Medications Discovery Branch; National Institute on Drug Abuse. NIH, DHHS; Baltimore MD USA
| | - Guo-Hua Bi
- Neuropsychopharmacology Section; Chemical Biology Research Branch; Intramural Research Program; National Institute on Drug Abuse. NIH, DHHS; Baltimore MD USA
| | - Hai-Ying Zhang
- Neuropsychopharmacology Section; Chemical Biology Research Branch; Intramural Research Program; National Institute on Drug Abuse. NIH, DHHS; Baltimore MD USA
| | - Xiao-Fei Wang
- Neuropsychopharmacology Section; Chemical Biology Research Branch; Intramural Research Program; National Institute on Drug Abuse. NIH, DHHS; Baltimore MD USA
| | - Hong-Ju Yang
- Neuropsychopharmacology Section; Chemical Biology Research Branch; Intramural Research Program; National Institute on Drug Abuse. NIH, DHHS; Baltimore MD USA
| | - Ratika Srivastava
- Neuropsychopharmacology Section; Chemical Biology Research Branch; Intramural Research Program; National Institute on Drug Abuse. NIH, DHHS; Baltimore MD USA
| | - Eliot L. Gardner
- Neuropsychopharmacology Section; Chemical Biology Research Branch; Intramural Research Program; National Institute on Drug Abuse. NIH, DHHS; Baltimore MD USA
| | - Zheng-Xiong Xi
- Neuropsychopharmacology Section; Chemical Biology Research Branch; Intramural Research Program; National Institute on Drug Abuse. NIH, DHHS; Baltimore MD USA
| | - Amy Hauck Newman
- Medicinal Chemistry Section; Molecular Targets and Medications Discovery Branch; National Institute on Drug Abuse. NIH, DHHS; Baltimore MD USA
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Keck TM, Yang HJ, Bi GH, Huang Y, Zhang HY, Srivastava R, Gardner EL, Newman AH, Xi ZX. Fenobam sulfate inhibits cocaine-taking and cocaine-seeking behavior in rats: implications for addiction treatment in humans. Psychopharmacology (Berl) 2013; 229:253-65. [PMID: 23615919 PMCID: PMC4191672 DOI: 10.1007/s00213-013-3106-9] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2012] [Accepted: 03/30/2013] [Indexed: 12/14/2022]
Abstract
RATIONALE The metabotropic glutamate receptor subtype 5 (mGluR5) has been reported to be critically involved in drug reward and addiction. Because the mGluR5 negative allosteric modulators (NAMs) 2-methyl-6-(phenylethynyl)pyridine (MPEP) and 3-((2-methyl-1,3-thiazol-4-yl)ethynyl)pyridine (MTEP) significantly inhibit addictivelike behaviors of cocaine and other drugs of abuse in experimental animals, it has been suggested that mGluR5 NAMs may have translational potential for treatment of addiction in humans. However, neither MPEP nor MTEP have been evaluated in humans due to their off-target actions and rapid metabolism. OBJECTIVES Herein, we evaluate a potential candidate for translational addiction research: a new sulfate salt formulation of fenobam, a selective mGluR5 NAM that has been investigated in humans. RESULTS In rats, fenobam sulfate had superior pharmacokinetics compared to the free base, with improved maximal plasma concentration (C max) and longer half life. Oral (p.o.) administration of fenobam sulfate (30 or 60 mg/kg) inhibited intravenous (i.v.) cocaine self-administration, cocaine-induced reinstatement of drug-seeking behavior, and cocaine-associated cue-induced cocaine-seeking behavior in rats. Fenobam sulfate also inhibited p.o. sucrose self-administration and sucrose-induced reinstatement of sucrose-seeking behavior, but had no effect on locomotion. CONCLUSIONS This study provides additional support for the role of mGluR5 signaling in cocaine addiction and suggests that fenobam sulfate may have translational potential in medication development for the treatment of cocaine addiction in humans.
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Affiliation(s)
- Thomas M. Keck
- Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, Intramural Research Program, National Institute on Drug Abuse, NIH, DHHS, Baltimore, MD, USA 21224
| | - Hong-Ju Yang
- Neuropsychopharmacology Section, Chemical Biology Research Branch, Intramural Research Program, National Institute on Drug Abuse, NIH, DHHS, Baltimore, MD, USA 21224
| | - Guo-Hua Bi
- Neuropsychopharmacology Section, Chemical Biology Research Branch, Intramural Research Program, National Institute on Drug Abuse, NIH, DHHS, Baltimore, MD, USA 21224
| | - Yong Huang
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, CA, USA 94143
| | - Hai-Ying Zhang
- Neuropsychopharmacology Section, Chemical Biology Research Branch, Intramural Research Program, National Institute on Drug Abuse, NIH, DHHS, Baltimore, MD, USA 21224
| | - Ratika Srivastava
- Neuropsychopharmacology Section, Chemical Biology Research Branch, Intramural Research Program, National Institute on Drug Abuse, NIH, DHHS, Baltimore, MD, USA 21224
| | - Eliot L. Gardner
- Neuropsychopharmacology Section, Chemical Biology Research Branch, Intramural Research Program, National Institute on Drug Abuse, NIH, DHHS, Baltimore, MD, USA 21224
| | - Amy Hauck Newman
- Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, Intramural Research Program, National Institute on Drug Abuse, NIH, DHHS, Baltimore, MD, USA 21224
- Corresponding authors: Z.-X. Xi – Phone: (443) 740-2517. Fax: (443) 740-2781. ; A. H. Newman – Phone: (443) 740-2887. Fax: (443) 740-2111.
| | - Zheng-Xiong Xi
- Neuropsychopharmacology Section, Chemical Biology Research Branch, Intramural Research Program, National Institute on Drug Abuse, NIH, DHHS, Baltimore, MD, USA 21224
- Corresponding authors: Z.-X. Xi – Phone: (443) 740-2517. Fax: (443) 740-2781. ; A. H. Newman – Phone: (443) 740-2887. Fax: (443) 740-2111.
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Timmer KM, Steketee JD. Group I metabotropic glutamate receptors in the medial prefrontal cortex: role in mesocorticolimbic glutamate release in cocaine sensitization. Synapse 2013; 67:887-96. [PMID: 23913407 DOI: 10.1002/syn.21699] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2013] [Revised: 07/02/2013] [Accepted: 07/12/2013] [Indexed: 11/08/2022]
Abstract
Cocaine sensitization is associated with increased excitability of pyramidal projection neurons in the medial prefrontal cortex. Such hyperexcitability is presumed to increase glutamatergic input to the nucleus accumbens and ventral tegmental area. This study examined the effects of medial prefrontal cortex Group I metabotropic glutamate receptor activation on glutamate levels in the medial prefrontal cortex, nucleus accumbens, and ventral tegmental area in sensitized and control animals. Male Sprague-Dawley rats received four daily injections of cocaine (15 mg/kg, i.p.) or saline (1 mL/kg i.p.). One, 7, or 21 days from the fourth injection, dual-probe microdialysis experiments were performed wherein Group I metabotropic glutamate receptor agonist DHPG was infused into the medial prefrontal cortex and glutamate levels in this region as well as the nucleus accumbens or ventral tegmental area were examined. Intra-mPFC DHPG infusion increased glutamate levels in the medial prefrontal cortex at 1 and 7 days withdrawal, and in the nucleus accumbens at 21 days withdrawal in sensitized rats. These results suggest Group I metabotropic glutamate receptor activation may contribute to the increased excitability of medial prefrontal cortex pyramidal neurons in sensitized animals.
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Affiliation(s)
- Kristin M Timmer
- Department of Pharmacology, University of Tennessee Health Science Center, Memphis, Tennessee, 38163
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Martínez-Rivera A, Rodríguez-Borrero E, Matías-Alemán M, Montalvo-Acevedo A, Guerrero-Figuereo K, Febo-Rodríguez LJ, Morales-Rivera A, Maldonado-Vlaar CS. Metabotropic glutamate receptor 5 within nucleus accumbens shell modulates environment-elicited cocaine conditioning expression. Pharmacol Biochem Behav 2013; 110:154-60. [PMID: 23850523 DOI: 10.1016/j.pbb.2013.06.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Revised: 06/05/2013] [Accepted: 06/23/2013] [Indexed: 10/26/2022]
Abstract
The metabotropic glutamate receptors 5 (mGluRs5) within the Nucleus Accumbens (NAc) have been implicated in the modulation of psychostimulant reward. We hypothesized that blockade of mGluR5 within the NAc shell would impair cocaine conditioning in rats. For this study, animals were implanted with cannulae within the NAc shell, and separate groups were exposed to a multimodal environment within activity chambers that signaled cocaine (cocaine-paired) or saline (controls, cocaine-unpaired) injections. Prior to placing the animals in the chambers, rats received systemic intraperitoneal injections of saline or cocaine for 10 consecutive sessions. In the test session (D12), animals were exposed to the multimodal environment without any cocaine or saline pre-treatment. Before placing the rats in the chambers, separate groups of animals were infused within the NAc shell with 2.5, 12 or 25 nmol/0.5 μl/side of 2-methyl-6-(phenylethynyl) pyridine (MPEP), an antagonist of mGluR5 or with vehicle. Blockade of the mGluR5 subtype at a 2.5 nmol dose showed no significant difference in either the ambulatory distance (AD) or the vertical plane move time (VPT). In contrast, mGluR5 blockade at 12 nmol and 25 nmol decreased conditioned locomotion in the cocaine-paired groups. An association of the environmental cues with the effects of cocaine implies the involvement of memory process during the conditioning response. Our results suggest that mGluR5 within the NAc shell could be modulating the expression of memory related to the association of environmental cues with the effects of cocaine. We suggest that mGluR5 could be taking into account to further studies related with cocaine exposure and cocaine addiction treatments.
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12
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Adaptations in AMPA receptor transmission in the nucleus accumbens contributing to incubation of cocaine craving. Neuropharmacology 2013; 76 Pt B:287-300. [PMID: 23727437 DOI: 10.1016/j.neuropharm.2013.04.061] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Revised: 04/29/2013] [Accepted: 04/30/2013] [Indexed: 12/23/2022]
Abstract
Cue-induced cocaine craving in rodents intensifies or "incubates" during the first months of withdrawal from long access cocaine self-administration. This incubation phenomenon is relevant to human users who achieve abstinence but exhibit persistent vulnerability to cue-induced relapse. It is well established that incubation of cocaine craving involves complex neuronal circuits. Here we will focus on neuroadaptations in the nucleus accumbens (NAc), a region of convergence for pathways that control cocaine seeking. A key adaptation is a delayed (~3-4 weeks) accumulation of Ca(2+)-permeable AMPAR receptors (CP-AMPARs) in synapses on medium spiny neurons (MSN) of the NAc. These CP-AMPARs mediate the expression of incubation after prolonged withdrawal, although different mechanisms must be responsible during the first weeks of withdrawal, prior to CP-AMPAR accumulation. The cascade of events leading to CP-AMPAR accumulation is still unclear. However, several candidate mechanisms have been identified. First, mGluR1 has been shown to negatively regulate CP-AMPAR levels in NAc synapses, and it is possible that a withdrawal-dependent decrease in this effect may help explain CP-AMPAR accumulation during incubation. Second, an increase in phosphorylation of GluA1 subunits (at the protein kinase A site) within extrasynaptic homomeric GluA1 receptors (CP-AMPARs) may promote their synaptic insertion and oppose their removal. Finally, elevation of brain-derived neurotrophic factor (BDNF) levels in the NAc may contribute to maintenance of incubation after months of withdrawal, although incubation-related increases in BDNF accumulation do not account for CP-AMPAR accumulation. Receptors and pathways that negatively regulate incubation, such as mGluR1, are promising targets for the development of therapeutic strategies to help recovering addicts maintain abstinence. This article is part of a Special Issue entitled 'NIDA 40th Anniversary Issue'.
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Loweth JA, Tseng KY, Wolf ME. Using metabotropic glutamate receptors to modulate cocaine's synaptic and behavioral effects: mGluR1 finds a niche. Curr Opin Neurobiol 2013; 23:500-6. [PMID: 23385114 DOI: 10.1016/j.conb.2013.01.009] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2012] [Revised: 01/10/2013] [Accepted: 01/11/2013] [Indexed: 11/29/2022]
Abstract
Group I metabotropic glutamate receptors (mGluR) are important modulators of excitatory synaptic transmission and therefore potential targets for drug development. In several brain regions (ventral tegmental area (VTA), cerebellum, and amygdala), stimulation of mGluR1 selectively inhibits synaptic transmission mediated by calcium-permeable AMPA receptors (CP-AMPARs) and thus produces synaptic depression. The same relationship has now been demonstrated in the nucleus accumbens (NAc), a region that is critical for cocaine craving. CP-AMPAR levels in NAc synapses are normally low, but they increase after prolonged withdrawal from extended-access cocaine self-administration (SA). These CP-AMPARs mediate the intensified ('incubated') cue-induced cocaine craving observed under these conditions. Therefore, activation of mGluR1 with positive allosteric modulators (PAM) may reduce cue-induced relapse in abstinent cocaine addicts.
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Affiliation(s)
- Jessica A Loweth
- Department of Neuroscience, Rosalind Franklin University of Medicine, USA
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Xie X, Lasseter HC, Ramirez DR, Ponds KL, Wells AM, Fuchs RA. Subregion-specific role of glutamate receptors in the nucleus accumbens on drug context-induced reinstatement of cocaine-seeking behavior in rats. Addict Biol 2012; 17:287-99. [PMID: 21521425 PMCID: PMC4384648 DOI: 10.1111/j.1369-1600.2011.00325.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The functional integrity of the nucleus accumbens (NAC) core and shell is necessary for contextual cocaine-seeking behavior in the reinstatement animal model of drug relapse; however, the neuropharmacological mechanisms underlying this phenomenon are poorly understood. The present study evaluated the contribution of metabotropic glutamate receptor subtype 1 (mGluR1) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate receptor populations to drug context-induced reinstatement of cocaine-seeking behavior. Rats were trained to lever press for un-signaled cocaine infusions in a distinct context followed by extinction training in a different context. Cocaine-seeking behavior (non-reinforced active lever pressing) was then assessed in the previously cocaine-paired and extinction contexts after JNJ16259685 (mGluR1 antagonist: 0.0, 0.6, or 30 pg/0.3 µl/hemisphere) or CNQX (AMPA/kainate receptor antagonist: 0.0, 0.03, or 0.3 µg/0.3 µl /hemisphere) administration into the NAC core, medial or lateral NAC shell, or the ventral caudate-putamen (vCPu, anatomical control). JNJ16259685 or CNQX in the NAC core dose-dependently impaired contextual cocaine-seeking behavior relative to vehicle. Conversely, CNQX, but not JNJ16259685, in the lateral or medial NAC shell attenuated, whereas CNQX or JNJ16259685 in vCPu failed to inhibit, this behavior. The manipulations failed to alter instrumental behavior in the extinction context, general motor activity or food-reinforced instrumental behavior in control experiments. Thus, glutamate-mediated changes in drug context-induced motivation for cocaine involve distinct neuropharmacological mechanisms within the core and shell subregions of the NAC, with the stimulation of mGlu1 and AMPA/kainate receptors in the NAC core and the stimulation of AMPA/kainate, but not mGlu1, receptors in the NAC shell being necessary for this phenomenon.
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Affiliation(s)
- Xiaohu Xie
- Department of Psychology, University of North Carolina, Chapel Hill, NC, USA
| | - Heather C. Lasseter
- Department of Psychology, University of North Carolina, Chapel Hill, NC, USA
| | - Donna R. Ramirez
- Department of Psychology, University of North Carolina, Chapel Hill, NC, USA
| | - KaiCee L. Ponds
- Department of Psychology, University of North Carolina, Chapel Hill, NC, USA
| | - Audrey M. Wells
- Department of Psychology, University of North Carolina, Chapel Hill, NC, USA
| | - Rita A. Fuchs
- Department of Psychology, University of North Carolina, Chapel Hill, NC, USA
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15
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Cleva RM, Olive MF. Metabotropic glutamate receptors and drug addiction. ACTA ACUST UNITED AC 2012; 1:281-295. [DOI: 10.1002/wmts.18] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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16
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Abstract
The repeated use of drugs that directly or indirectly stimulate dopamine transmission carry addiction liability and produce enduring pathological changes in the brain circuitry that normally regulates adaptive behavioral responding to a changing environment. This circuitry is rich in glutamatergic projections, and addiction-related behaviors in animal models have been linked to impairments in excitatory synaptic plasticity. Among the best-characterized glutamatergic projection in this circuit is the prefrontal efferent to the nucleus accumbens. A variety of molecular adaptations have been identified in the prefrontal glutamate synapses in the accumbens, many of which are induced by different classes of addictive drugs. Based largely on work with cocaine, we hypothesize that the drug-induced adaptations impair synaptic plasticity in the cortico-accumbens projection, and thereby dysregulate the ability of addicts to control their drug-taking habits. Accordingly, we go on to describe the literature implicating the drug-induced changes in protein content or function that impinge upon synaptic plasticity and have been targeted in preclinical models of relapse and, in some cases, in pilot clinical trials. Based upon modeling drug-induced impairments in neuroplasticity in the cortico-accumbens pathway, we argue for a concerted effort to clinically evaluate the hypothesis that targeting glial and neuronal proteins regulating excitatory synaptic plasticity may prove beneficial in treating addiction.
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Duncan JR, Lawrence AJ. The role of metabotropic glutamate receptors in addiction: evidence from preclinical models. Pharmacol Biochem Behav 2011; 100:811-24. [PMID: 21443897 DOI: 10.1016/j.pbb.2011.03.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Revised: 02/21/2011] [Accepted: 03/16/2011] [Indexed: 11/25/2022]
Abstract
Addiction is a chronic disorder characterised by repeated bouts of drug taking, abstinence and relapse. The addicted state may be in part due to drug-induced neuroadaptations in the mesocorticolimbic and corticostriatal pathways. Recently focus has been on the role of aberrant glutamate transmission and its contribution to the hierarchical control over these systems. This review will expand our current knowledge of the most recent advances that have been made in preclinical animal models that provide evidence that implicate metabotropic glutamate receptors (mGluRs) in contributing to the neuroadaptations pertinent to addiction, as well as the role of Homer proteins in regulating these responses. The recent discovery of receptor mosaics will be discussed which add an additional dimension to the complexity of understanding the mechanism of glutamate mediated behaviours. Finally this review introduces a new area related to glutamatergic responses, namely microRNAs, that may become pivotal in directing our future understanding of how to best target intervention strategies to prevent addictive behaviours.
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Affiliation(s)
- Jhodie R Duncan
- Florey Neuroscience Institutes, University of Melbourne, Parkville, Vic., 3010, Australia.
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18
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Uys JD, Reissner KJ. Glutamatergic Neuroplasticity in Cocaine Addiction. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2011; 98:367-400. [DOI: 10.1016/b978-0-12-385506-0.00009-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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19
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RGS14 is a natural suppressor of both synaptic plasticity in CA2 neurons and hippocampal-based learning and memory. Proc Natl Acad Sci U S A 2010; 107:16994-8. [PMID: 20837545 DOI: 10.1073/pnas.1005362107] [Citation(s) in RCA: 140] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Learning and memory have been closely linked to strengthening of synaptic connections between neurons (i.e., synaptic plasticity) within the dentate gyrus (DG)-CA3-CA1 trisynaptic circuit of the hippocampus. Conspicuously absent from this circuit is area CA2, an intervening hippocampal region that is poorly understood. Schaffer collateral synapses on CA2 neurons are distinct from those on other hippocampal neurons in that they exhibit a perplexing lack of synaptic long-term potentiation (LTP). Here we demonstrate that the signaling protein RGS14 is highly enriched in CA2 pyramidal neurons and plays a role in suppression of both synaptic plasticity at these synapses and hippocampal-based learning and memory. RGS14 is a scaffolding protein that integrates G protein and H-Ras/ERK/MAP kinase signaling pathways, thereby making it well positioned to suppress plasticity in CA2 neurons. Supporting this idea, deletion of exons 2-7 of the RGS14 gene yields mice that lack RGS14 (RGS14-KO) and now express robust LTP at glutamatergic synapses in CA2 neurons with no impact on synaptic plasticity in CA1 neurons. Treatment of RGS14-deficient CA2 neurons with a specific MEK inhibitor blocked this LTP, suggesting a role for ERK/MAP kinase signaling pathways in this process. When tested behaviorally, RGS14-KO mice exhibited marked enhancement in spatial learning and in object recognition memory compared with their wild-type littermates, but showed no differences in their performance on tests of nonhippocampal-dependent behaviors. These results demonstrate that RGS14 is a key regulator of signaling pathways linking synaptic plasticity in CA2 pyramidal neurons to hippocampal-based learning and memory but distinct from the canonical DG-CA3-CA1 circuit.
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20
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Hao Y, Martin-Fardon R, Weiss F. Behavioral and functional evidence of metabotropic glutamate receptor 2/3 and metabotropic glutamate receptor 5 dysregulation in cocaine-escalated rats: factor in the transition to dependence. Biol Psychiatry 2010; 68:240-8. [PMID: 20416862 PMCID: PMC2907426 DOI: 10.1016/j.biopsych.2010.02.011] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2009] [Revised: 02/11/2010] [Accepted: 02/12/2010] [Indexed: 10/25/2022]
Abstract
BACKGROUND Rats with extended daily cocaine access show escalating cocaine self-administration and behavioral signs of dependence. Regulation of glutamatergic transmission by metabotropic glutamate receptors has emerged as a mechanism in the addictive actions of drugs of abuse. We examined here whether neuroadaptive dysregulation of metabotropic glutamate receptor function is a factor in escalating cocaine self-administration. METHODS Rats with 1 hour daily cocaine access (short access [ShA]) versus 6-hour access (long access [LgA]) were tested for differences in the effects of the metabotropic glutamate receptor 2/3 (mGluR2/3) agonist (-)-2-oxa-4-aminobicylco(3.1.0)hexane-4,6-dicarboxylic acid (LY379268) and the metabotropic glutamate receptor 5 (mGluR5) antagonist 3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]-pyridine (MTEP) on cocaine-reinforced progressive-ratio responding and differences in expression levels and functional activity of mGluR2/3 and mGluR5. RESULTS The LgA groups showed higher progressive-ratio breakpoints than ShA groups. LY379268 (0-3 mg/kg subcutaneous) dose-dependently lowered breakpoints in the LgA group but reduced breakpoints only at 3 mg/kg in the ShA group. Consistent with this behavioral effect, functional mGluR2/3 activity was significantly elevated following LgA cocaine exposure. MTEP (0-3 mg/kg intraperitoneal) reduced breakpoints in the ShA group only. Long access cocaine exposure was associated with decreased mGluR5 expression, accompanied by reduced functional mGluR5 activity in the nucleus accumbens. A downward trend developed in mGluR5 protein expression in the medial prefrontal cortex and hippocampus. CONCLUSIONS Functional upregulation of mGluR2/3 and downregulation of mGluR5 are likely factors in the transition to cocaine dependence. The differential behavioral effects of LY379268 and MTEP in rats with a history of long access to cocaine have implications for the treatment target potential of mGluR2/3 and mGluR5.
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Affiliation(s)
- Yue Hao
- Molecular and Integrative Neurosciences Department, The Scripps Research Institute, La Jolla, California, USA.
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21
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Hundahl C, Hannibal J, Fahrenkrug J, Dewilde S, Hay-Schmidt A. Neuroglobin expression in the rat suprachiasmatic nucleus: Colocalization, innervation, and response to light. J Comp Neurol 2010; 518:1556-69. [DOI: 10.1002/cne.22290] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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22
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Mitrano D, Pare JF, Smith Y. Ultrastructural relationships between cortical, thalamic, and amygdala glutamatergic inputs and group I metabotropic glutamate receptors in the rat accumbens. J Comp Neurol 2010; 518:1315-29. [PMID: 20151362 PMCID: PMC3895817 DOI: 10.1002/cne.22277] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Changes in glutamatergic transmission in the nucleus accumbens play a key role in mediating reward-related behaviors and addiction to psychostimulants. Glutamatergic inputs to the accumbens originate from multiple sources, including the prefrontal cortex, basolateral amygdala, and midline thalamus. The group I metabotropic glutamate receptors (mGluRs) are found throughout the core and shell of the nucleus accumbens, but their localization and function at specific glutamatergic synapses remain unknown. To further characterize the substrate that underlies group I mGluR functions in the accumbens, we combined anterograde tract tracing method with electron microscopy immunocytochemistry to study the ultrastructural relationships between specific glutamatergic afferents and mGluR1a- or mGluR5-containing neurons in the rat nucleus accumbens. Although cortical, thalamic, and amygdala glutamatergic terminals contact both mGluR1a- and mGluR5-immunoreactive dendrites and spines in the shell and core of the accumbens, they do so to varying degrees. Overall, glutamatergic terminals contact mGluR1a-positive spines about 30% of the time, whereas they form synapses twice as frequently with mGluR5-labeled spines. At the subsynaptic level, mGluR5 is more frequently expressed perisynaptically and closer to the edges of glutamatergic axospinous synapses than mGluR1a, suggesting a differential degree of activation of the two group I mGluRs by transmitter spillover from glutamatergic synapses in the rat accumbens. These results lay the foundation for a deeper understanding of group I mGluR-mediated effects in the ventral striatum, and their potential therapeutic benefits in drug addiction and other neuropsychiatric changes in reward-related behaviors.
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Affiliation(s)
- D.A. Mitrano
- Yerkes National Primate Research Center, Emory University, Atlanta, Georgia 30322
- Department of Human Genetics, Emory University, Atlanta, Georgia 30322
| | - J.-F. Pare
- Yerkes National Primate Research Center, Emory University, Atlanta, Georgia 30322
| | - Y. Smith
- Yerkes National Primate Research Center, Emory University, Atlanta, Georgia 30322
- Department of Neurology, Emory University, Atlanta, Georgia 30322
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23
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D'Souza MS, Markou A. Neural substrates of psychostimulant withdrawal-induced anhedonia. Curr Top Behav Neurosci 2010; 3:119-178. [PMID: 21161752 DOI: 10.1007/7854_2009_20] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Psychostimulant drugs have powerful reinforcing and hedonic properties and are frequently abused. Cessation of psychostimulant administration results in a withdrawal syndrome characterized by anhedonia (i.e., an inability to experience pleasure). In humans, psychostimulant withdrawal-induced anhedonia can be debilitating and has been hypothesized to play an important role in relapse to drug use. Hence, understanding the neural substrates involved in psychostimulant withdrawal-induced anhedonia is essential. In this review, we first summarize the theoretical perspectives of psychostimulant withdrawal-induced anhedonia. Experimental procedures and measures used to assess anhedonia in experimental animals are also discussed. The review then focuses on neural substrates hypothesized to play an important role in anhedonia experienced after termination of psychostimulant administration, such as with cocaine, amphetamine-like drugs, and nicotine. Both neural substrates that have been extensively investigated and some that need further evaluation with respect to psychostimulant withdrawal-induced anhedonia are reviewed. In the context of reviewing the various neurosubstrates of psychostimulant withdrawal, we also discuss pharmacological medications that have been used to treat psychostimulant withdrawal in humans. This literature review indicates that great progress has been made in understanding the neural substrates of anhedonia associated with psychostimulant withdrawal. These advances in our understanding of the neurobiology of anhedonia may also shed light on the neurobiology of nondrug-induced anhedonia, such as that seen as a core symptom of depression and a negative symptom of schizophrenia.
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Affiliation(s)
- Manoranjan S D'Souza
- Department of Psychiatry, University of California, San Diego, La Jolla, CA 92093, USA
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24
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Neuroplastic alterations in the limbic system following cocaine or alcohol exposure. Curr Top Behav Neurosci 2010; 3:3-27. [PMID: 21161748 DOI: 10.1007/7854_2009_23] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Neuroplastic changes in the CNS are thought to be a fundamental component of learning and memory. While pioneering studies in the hippocampus and cerebellum have detailed many of the basic mechanisms that can lead to alterations in synaptic transmission based on previous activity, only more recently has synaptic plasticity been monitored after behavioral manipulation or drug exposure. In this chapter, we review evidence that drugs of abuse are powerful modulators of synaptic plasticity. Both the dopaminergic neurons of the ventral tegmental area as well medium spiny neurons in nucleus accumbens show enhanced excitatory synaptic strength following passive or active exposure to drugs such as cocaine and alcohol. In the VTA, both the enhancement of excitatory synaptic strength and the acquisition of drug-related behaviors depend on signaling through the N-methyl-D: -aspartate receptors (NMDARs) which are mechanistically thought to lead to increased synaptic insertion of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs). Synaptic insertion of AMPARs by drugs of abuse can be long lasting, depending on the route of administration, number of drug exposures, or whether the drugs are received passively or self-administered.
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25
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Hong YH, Kim JY, Lee JH, Chae HG, Jang SS, Jeon JH, Kim CH, Kim J, Kim SJ. Agonist-induced internalization of mGluR1alpha is mediated by caveolin. J Neurochem 2009; 111:61-71. [PMID: 19627451 DOI: 10.1111/j.1471-4159.2009.06289.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Agonist-induced internalization of metabotropic glutamate receptors (mGluRs) plays an important role in neuronal signaling. Although internalization of mGluRs has been reported to be mediated by clathrin-dependent pathway, studies describing clathrin-independent pathways are emerging. Here, we report that agonist-induced internalization of mGluR1alpha is mediated by caveolin. We show that two caveolin-binding motifs of mGluR1alpha interact with caveolin1/2. Using cell surface-immunoprecipitation and total internal reflection fluorescence imaging, we found that agonist-induced internalization of mGluR1alpha is regulated by caveolin-binding motifs of the receptor in heterologous cells. Moreover, in the cerebellum, group I mGluR agonist dihydroxyphenylglycol increased the interaction of phosphorylated caveolin with mGluR1alpha. This interaction was blocked by methyl-beta-cyclodextrin, known to disrupt caveolin/caveolae-dependent signaling by cholesterol depletion. Methyl-beta-cyclodextrin also blocked the agonist-induced internalization of mGluR1alpha. Thus, these findings represent the evidence for agonist-induced internalization of mGluR1alpha via caveolin and suggest that caveolin might play a role in synaptic metaplasticity by regulating internalization of mGluR1alpha in the cerebellum.
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Affiliation(s)
- Yun Hwa Hong
- Department of Physiology, Seoul National University College of Medicine, Seoul, Korea
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26
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Abstract
Addiction is associated with neuroplasticity in the corticostriatal brain circuitry that is important for guiding adaptive behaviour. The hierarchy of corticostriatal information processing that normally permits the prefrontal cortex to regulate reinforcement-seeking behaviours is impaired by chronic drug use. A failure of the prefrontal cortex to control drug-seeking behaviours can be linked to an enduring imbalance between synaptic and non-synaptic glutamate, termed glutamate homeostasis. The imbalance in glutamate homeostasis engenders changes in neuroplasticity that impair communication between the prefrontal cortex and the nucleus accumbens. Some of these pathological changes are amenable to new glutamate- and neuroplasticity-based pharmacotherapies for treating addiction.
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Guo Y, Wang HL, Xiang XH, Zhao Y. The role of glutamate and its receptors in mesocorticolimbic dopaminergic regions in opioid addiction. Neurosci Biobehav Rev 2009; 33:864-73. [DOI: 10.1016/j.neubiorev.2009.02.005] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2008] [Revised: 02/10/2009] [Accepted: 02/19/2009] [Indexed: 11/28/2022]
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