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Illenberger JM, Flores-Ramirez FJ, Matzeu A, Lütjens R, Martin-Fardon R. ADX106772, an mGlu2 receptor positive allosteric modulator, selectively attenuates oxycodone taking and seeking. Neuropharmacology 2023; 238:109666. [PMID: 37463637 PMCID: PMC10529136 DOI: 10.1016/j.neuropharm.2023.109666] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Revised: 06/29/2023] [Accepted: 07/10/2023] [Indexed: 07/20/2023]
Abstract
Opioid abuse and overdose have risen to epidemic proportions in the United States. Oxycodone is the most abused prescription opioid. Treatments for opioid use disorder (OUD) seek to reduce vulnerability to relapse by reducing sources of reinforcement to seek drug (i.e., acute drug effects or drug withdrawal/craving). Accumulating evidence that glutamate release elicits drug-seeking behaviors has generated interest in pharmacotherapies targeting the glutamate system. Agonists and positive allosteric modulators of the metabotropic glutamate 2 (mGlu2) receptor decrease glutamate activity, reducing drug taking and seeking. The present study tested whether the mGlu2 receptor positive allosteric modulator ADX106772 reduces oxycodone self-administration and the conditioned reinstatement of oxycodone seeking without affecting behaviors directed toward a highly palatable nondrug reinforcer (sweetened condensed milk). Male Wistar rats were trained to self-administer oxycodone (0.15 mg/kg/infusion, i.v., 12 h/day) or sweetened condensed milk (SCM; diluted 2:1 v/v in H2O, orally, 30 min/day) for 13 days in the presence of a contextual/discriminative stimulus (SD), and the ability of ADX106772 (0, 0.3, 1, 3 and-10 mg/kg, s. c.) to decrease self-administration was tested. The rats then underwent extinction training, during which oxycodone, SCM, and the SD were withheld. After extinction, the ability of ADX106772 to prevent SD-induced conditioned reinstatement of oxycodone and SCM seeking was tested. ADX106772 reduced oxycodone self-administration and conditioned reinstatement without affecting SCM self-administration or conditioned reinstatement. ADX106772 reduced oxycodone taking and seeking and did not affect the motivation for the palatable conventional reinforcer, SCM, suggesting that activating mGlu2 receptors with a positive allosteric modulator is a potential approach for prescription OUD treatment.
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Affiliation(s)
- Jessica M Illenberger
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA, USA.
| | | | - Alessandra Matzeu
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA, USA
| | | | - Rémi Martin-Fardon
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA, USA
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Saha S, González-Maeso J. The crosstalk between 5-HT 2AR and mGluR2 in schizophrenia. Neuropharmacology 2023; 230:109489. [PMID: 36889432 PMCID: PMC10103009 DOI: 10.1016/j.neuropharm.2023.109489] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 02/26/2023] [Accepted: 03/05/2023] [Indexed: 03/08/2023]
Abstract
Schizophrenia is a severe brain disorder that usually produces a lifetime of disability. First generation or typical antipsychotics such as haloperidol and second generation or atypical antipsychotics such as clozapine and risperidone remain the current standard for schizophrenia treatment. In some patients with schizophrenia, antipsychotics produce complete remission of positive symptoms, such as hallucinations and delusions. However, antipsychotic drugs are ineffective against cognitive deficits and indeed treated schizophrenia patients have small improvements or even deterioration in several cognitive domains. This underlines the need for novel and more efficient therapeutic targets for schizophrenia treatment. Serotonin and glutamate have been identified as key parts of two neurotransmitter systems involved in fundamental brain processes. Serotonin (or 5-hydroxytryptamine) 5-HT2A receptor (5-HT2AR) and metabotropic glutamate 2 receptor (mGluR2) are G protein-coupled receptors (GPCRs) that interact at epigenetic and functional levels. These two receptors can form GPCR heteromeric complexes through which their pharmacology, function and trafficking becomes affected. Here we review past and current research on the 5-HT2AR-mGluR2 heterocomplex and its potential implication in schizophrenia and antipsychotic drug action. This article is part of the Special Issue on "The receptor-receptor interaction as a new target for therapy".
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Affiliation(s)
- Somdatta Saha
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, VA, 23298, USA
| | - Javier González-Maeso
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, VA, 23298, USA.
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Santini MA, Balu DT, Puhl MD, Hill-Smith TE, Berg AR, Lucki I, Mikkelsen JD, Coyle JT. D-serine deficiency attenuates the behavioral and cellular effects induced by the hallucinogenic 5-HT(2A) receptor agonist DOI. Behav Brain Res 2013; 259:242-6. [PMID: 24269270 DOI: 10.1016/j.bbr.2013.11.022] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Revised: 11/07/2013] [Accepted: 11/12/2013] [Indexed: 01/15/2023]
Abstract
Both the serotonin and glutamate systems have been implicated in the pathophysiology of schizophrenia, as well as in the mechanism of action of antipsychotic drugs. Psychedelic drugs act through the serotonin 2A receptor (5-HT2AR), and elicit a head-twitch response (HTR) in mice, which directly correlates to 5-HT2AR activation and is absent in 5-HT2AR knockout mice. The precise mechanism of this response remains unclear, but both an intrinsic cortico-cortical pathway and a thalamo-cortical pathway involving glutamate release have been proposed. Here, we used a genetic model of NMDAR hypofunction, the serine racemase knockout (SRKO) mouse, to explore the role of glutamatergic transmission in regulating 5-HT2AR-mediated cellular and behavioral responses. SRKO mice treated with the 5-HT2AR agonist (±)-2,5-dimethoxy-4-iodoamphetamine (DOI) showed a clearly diminished HTR and lower induction of c-fos mRNA. These altered functional responses in SRKO mice were not associated with changes in cortical or hippocampal 5-HT levels or in 5-HT2AR and metabotropic glutamate-2 receptor (mGluR2) mRNA and protein expression. Together, these findings suggest that D-serine-dependent NMDAR activity is involved in mediating the cellular and behavioral effects of 5-HT2AR activation.
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Affiliation(s)
- Martin A Santini
- Neurobiology Research Unit, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark; Laboratory for Psychiatric and Molecular Neuroscience, McLean Hospital, Belmont, MA, USA; Department of Psychiatry, Harvard Medical School, Boston, MA, USA
| | - Darrick T Balu
- Laboratory for Psychiatric and Molecular Neuroscience, McLean Hospital, Belmont, MA, USA; Department of Psychiatry, Harvard Medical School, Boston, MA, USA
| | - Matthew D Puhl
- Laboratory for Psychiatric and Molecular Neuroscience, McLean Hospital, Belmont, MA, USA; Department of Psychiatry, Harvard Medical School, Boston, MA, USA
| | | | - Alexandra R Berg
- Laboratory for Psychiatric and Molecular Neuroscience, McLean Hospital, Belmont, MA, USA
| | - Irwin Lucki
- Department of Psychiatry, University of Pennsylvania, Philadelphia, PA, USA; Department of Pharmacology, University of Pennsylvania, Philadelphia, PA, USA
| | - Jens D Mikkelsen
- Neurobiology Research Unit, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark; Laboratory for Psychiatric and Molecular Neuroscience, McLean Hospital, Belmont, MA, USA
| | - Joseph T Coyle
- Laboratory for Psychiatric and Molecular Neuroscience, McLean Hospital, Belmont, MA, USA; Department of Psychiatry, Harvard Medical School, Boston, MA, USA.
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