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Donlon J, Kumari P, Varghese SP, Bai M, Florentin OD, Frost ED, Banks J, Vadlapatla N, Kam O, Shad MU, Rahman S, Abulseoud OA, Stone TW, Koola MM. Integrative Pharmacology in the Treatment of Substance Use Disorders. J Dual Diagn 2024; 20:132-177. [PMID: 38117676 DOI: 10.1080/15504263.2023.2293854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Abstract
The detrimental physical, mental, and socioeconomic effects of substance use disorders (SUDs) have been apparent to the medical community for decades. However, it has become increasingly urgent in recent years to develop novel pharmacotherapies to treat SUDs. Currently, practitioners typically rely on monotherapy. Monotherapy has been shown to be superior to no treatment at all for most substance classes. However, many randomized controlled trials (RCTs) have revealed that monotherapy leads to poorer outcomes when compared with combination treatment in all specialties of medicine. The results of RCTs suggest that monotherapy frequently fails since multiple dysregulated pathways, enzymes, neurotransmitters, and receptors are involved in the pathophysiology of SUDs. As such, research is urgently needed to determine how various neurobiological mechanisms can be targeted by novel combination treatments to create increasingly specific yet exceedingly comprehensive approaches to SUD treatment. This article aims to review the neurobiology that integrates many pathophysiologic mechanisms and discuss integrative pharmacology developments that may ultimately improve clinical outcomes for patients with SUDs. Many neurobiological mechanisms are known to be involved in SUDs including dopaminergic, nicotinic, N-methyl-D-aspartate (NMDA), and kynurenic acid (KYNA) mechanisms. Emerging evidence indicates that KYNA, a tryptophan metabolite, modulates all these major pathophysiologic mechanisms. Therefore, achieving KYNA homeostasis by harmonizing integrative pathophysiology and pharmacology could prove to be a better therapeutic approach for SUDs. We propose KYNA-NMDA-α7nAChRcentric pathophysiology, the "conductor of the orchestra," as a novel approach to treat many SUDs concurrently. KYNA-NMDA-α7nAChR pathophysiology may be the "command center" of neuropsychiatry. To date, extant RCTs have shown equivocal findings across comparison conditions, possibly because investigators targeted single pathophysiologic mechanisms, hit wrong targets in underlying pathophysiologic mechanisms, and tested inadequate monotherapy treatment. We provide examples of potential combination treatments that simultaneously target multiple pathophysiologic mechanisms in addition to KYNA. Kynurenine pathway metabolism demonstrates the greatest potential as a target for neuropsychiatric diseases. The investigational medications with the most evidence include memantine, galantamine, and N-acetylcysteine. Future RCTs are warranted with novel combination treatments for SUDs. Multicenter RCTs with integrative pharmacology offer a promising, potentially fruitful avenue to develop novel therapeutics for the treatment of SUDs.
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Affiliation(s)
- Jack Donlon
- Cooper Medical School of Rowan University, Camden, New Jersey, USA
| | - Pooja Kumari
- Community Living Trent Highlands, Peterborough, Canada
| | - Sajoy P Varghese
- Addiction Recovery Treatment Services, Veterans Affairs Northern California Health Care System, University of California, Davis, Sacramento, California, USA
| | - Michael Bai
- Columbia University, New York, New York, USA
| | - Ori David Florentin
- Department of Psychiatry, Westchester Medical Center, Valhalla, New York, USA
| | - Emma D Frost
- Department of Neurology, Cooper University Health Care, Camden, New Jersey, USA
| | - John Banks
- Talkiatry Mental Health Clinic, New York, New York, USA
| | - Niyathi Vadlapatla
- Thomas Jefferson High School for Science and Technology, Alexandria, Virginia, USA
| | - Olivia Kam
- Stony Brook University Renaissance School of Medicine, Stony Brook, New York, USA
| | - Mujeeb U Shad
- Department of Psychiatry, University of Nevada Las Vegas, Las Vegas, Nevada, USA
| | - Shafiqur Rahman
- Department of Pharmaceutical Sciences, College of Pharmacy, South Dakota State University, Brookings, South Dakota, USA
| | - Osama A Abulseoud
- Department of Psychiatry and Psychology, Alix School of Medicine at Mayo Clinic, Phoenix, Arizona, USA
| | - Trevor W Stone
- Nuffield Department of Orthopedics, Rheumatology and Musculoskeletal Sciences (NDORMS), University of Oxford, Oxford, UK
| | - Maju Mathew Koola
- Department of Psychiatry and Behavioral Health, Cooper University Health Care, Cooper Medical School of Rowan University, Camden, New Jersey, USA
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Toikumo S, Xu H, Gelernter J, Kember RL, Kranzler HR. Integrating human brain proteomic data with genome-wide association study findings identifies novel brain proteins in substance use traits. Neuropsychopharmacology 2022; 47:2292-2299. [PMID: 35941285 PMCID: PMC9630289 DOI: 10.1038/s41386-022-01406-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 06/13/2022] [Accepted: 07/16/2022] [Indexed: 11/09/2022]
Abstract
Despite the identification of a growing number of genetic risk loci for substance use traits (SUTs), the impact of these loci on protein abundance and the potential utility of relevant proteins as therapeutic targets are unknown. We conducted a proteome-wide association study (PWAS) in which we integrated human brain proteomes from discovery (Banner; N = 152) and validation (ROSMAP; N = 376) datasets with genome-wide association study (GWAS) summary statistics for 4 SUTs. The 4 samples comprised GWAS of European-ancestry individuals for smoking initiation [Smk] (N = 1,232,091), alcohol use disorder [AUD] (N = 313,959), cannabis use disorder [CUD] (N = 384,032), and opioid use disorder [OUD] (N = 302,585). We conducted transcriptome-wide association studies (TWAS) with human brain transcriptomic data to examine the overlap of genetic effects at the proteomic and transcriptomic levels and characterize significant genes through conditional, colocalization, and fine-mapping analyses. We identified 27 genes (Smk = 21, AUD = 3, CUD = 2, OUD = 1) that were significantly associated with cis-regulated brain protein abundance. Of these, 7 showed evidence for causality (Smk: NT5C2, GMPPB, NQO1, RHOT2, SRR and ACTR1B; and AUD: CTNND1). Cis-regulated transcript levels for 8 genes (Smk = 6, CUD = 1, OUD = 1) were associated with SUTs, indicating that genetic loci could confer risk for these SUTs by modulating both gene expression and proteomic abundance. Functional studies of the high-confidence risk proteins identified here are needed to determine whether they are modifiable targets and useful in developing medications and biomarkers for these SUTs.
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Affiliation(s)
- Sylvanus Toikumo
- Department of Psychiatry, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
- Mental Illness Research, Education and Clinical Center, Crescenz VAMC, Philadelphia, PA, USA
| | - Heng Xu
- Department of Psychiatry, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Joel Gelernter
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
| | - Rachel L Kember
- Department of Psychiatry, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA.
- Mental Illness Research, Education and Clinical Center, Crescenz VAMC, Philadelphia, PA, USA.
| | - Henry R Kranzler
- Department of Psychiatry, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA.
- Mental Illness Research, Education and Clinical Center, Crescenz VAMC, Philadelphia, PA, USA.
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Salmani N, Nozari M, Parvan M, Amini-Sardouei S, Shabani M, Khaksari M, Ezzatabadipour M. Nicotine-conditioned place preference, reversal learning, and social interaction in MK-801-induced schizophrenia model: Effects of post-weaning enriched environment. Clin Exp Pharmacol Physiol 2022; 49:871-880. [PMID: 35622536 DOI: 10.1111/1440-1681.13674] [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: 05/04/2021] [Revised: 01/22/2022] [Accepted: 05/24/2022] [Indexed: 11/30/2022]
Abstract
Based on the clinical observations of severe cognitive deficits in schizophrenia patients and the relationship between environmental parameters and the severity of schizophrenia symptoms, the present study investigated these parameters in an MK-801-induced schizophrenia model in rats. In addition to, it evaluated whether a post-weaning enriched environment (EE) would affect the nicotine-induced conditioned place preference (CPP) and the motor and cognitive deficits caused by MK-801 treatment. Male Wistar rat pups were injected peritoneally with MK-801 (1 mg/kg) on a daily basis between the 6th and the 10th postnatal days (P) and were exposed to either an enriched or a standard cage from P21 until the end of the experiments. The rats were evaluated in open-field and three-chamber social interaction tests. Moreover, spatial and reversal learning was assessed by the Morris water maze (MWM). Also, the animals were conditioned with 0.6 mg/kg nicotine and tested for CPP. Increased self-grooming, exploratory behavior, potentiated nicotine-CPP, and decreased social behaviors, delayed spatial learning and memory, and impaired reversal learning in the water maze were observed in the MK-801 treatment group. Housing in an EE improved cognitive and behavioral deficits associated with postnatal MK-801 treatment. The results suggested that neonatal N-methyl-D-aspartate (NMDA) receptor hypofunction may cause susceptibility to these behaviors and indicated the importance of environmental conditions in the development of schizophrenia and probably other neuropsychiatric disorders.
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Affiliation(s)
- Neda Salmani
- Department of Psychology, Zarand Branch, Islamic Azad University, Kerman, Iran
| | - Masoumeh Nozari
- Neuroscience Research Center, Institute of Neuropharmacology, Kerman University of Medical Sciences, Kerman, Iran
| | - Mahdieh Parvan
- Physiology Research Center, Institute of Basic and Clinical Physiology Sciences, Kerman University of Medical Sciences, Kerman, Iran
| | - Sara Amini-Sardouei
- Student Research Committee, Kerman University of Medical Sciences, Kerman, Iran
| | - Mohammad Shabani
- Neuroscience Research Center, Institute of Neuropharmacology, Kerman University of Medical Sciences, Kerman, Iran
| | - Mohammad Khaksari
- Endocrinology and Metabolism Research, and Physiology Research Centers, Kerman University of Medical Sciences, Kerman, Iran
| | - Massood Ezzatabadipour
- Anatomical Sciences Department, School of Medicine, Kerman University of Medical Sciences, Kerman, Iran
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Takagi S, Puhl MD, Anderson T, Balu DT, Coyle JT. Serine Racemase Expression by Striatal Neurons. Cell Mol Neurobiol 2022; 42:279-289. [PMID: 32445040 PMCID: PMC7680280 DOI: 10.1007/s10571-020-00880-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Accepted: 05/15/2020] [Indexed: 01/03/2023]
Abstract
D-serine is synthesized by serine racemase (SR) and is a co-agonist at forebrain N-methyl-D-aspartate receptors (NMDARs). D-serine and SR are expressed primarily in neurons, but not in quiescent astrocytes. In this study, we examined the localization of D-serine and SR in the mouse striatum and the effects of genetically silencing SR expression in GABAergic interneurons (iSR-/-). iSR-/- mice had substantially reduced SR expression almost exclusively in striatum, but only exhibited marginal D-serine reduction. SR positive cells in the striatum showed strong co-localization with dopamine- and cyclic AMP-regulated neuronal phosphoprotein (DARPP32) in wild type mice. Transgenic fluorescent reporter mice for either the D1 or D2 dopamine receptors exhibited a 65:35 ratio for co-localization with D1and D2 receptor positive cells, respectively. These results indicate that GABAergic medium spiny neurons receiving dopaminergic inputs in striatum robustly and uniformly express SR. In behavioral tests, iSR-/- mice showed a blunted response to the hedonic and stimulant effects of cocaine, without affecting anxiety-related behaviors. Because the cocaine effects have been shown in the constitutive SR-/- mice, the restriction of the blunted response to cocaine to iSR-/- mice reinforces the conclusion that D-serine in striatal GABAergic neurons plays an important role in mediating dopaminergic stimulant effects. Results in this study suggest that SR in striatal GABAergic neurons is synthesizing D-serine, not as a glutamatergic co-transmitter, but rather as an autocrine whereby the GABAergic neurons control the excitability of their NMDARs by determining the availability of the co-agonist, D-serine.
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Affiliation(s)
- Shunsuke Takagi
- Department of Psychiatry and Behavioral Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan,Department of Psychiatry, Tokyo Medical and Dental University Hospital, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan,Department of Neuropsychiatry, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan,Laboratory for Psychiatric and Molecular Neuroscience, McLean Hospital, 115 Mill Street, Belmont, MA 02478, USA
| | - Matthew D. Puhl
- Laboratory for Psychiatric and Molecular Neuroscience, McLean Hospital, 115 Mill Street, Belmont, MA 02478, USA
| | - Thea Anderson
- Laboratory for Psychiatric and Molecular Neuroscience, McLean Hospital, 115 Mill Street, Belmont, MA 02478, USA
| | - Darrick T. Balu
- Department of Psychiatry, Harvard Medical School, 25 Shattuck Street, Boston, MA 02115, USA,Translational Psychiatry Laboratory, McLean Hospital, 115 Mill Street, Belmont, MA 02478, USA
| | - Joseph T. Coyle
- Laboratory for Psychiatric and Molecular Neuroscience, McLean Hospital, 115 Mill Street, Belmont, MA 02478, USA,Department of Psychiatry, Harvard Medical School, 25 Shattuck Street, Boston, MA 02115, USA
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Coyle JT, Ruzicka WB, Balu DT. Fifty Years of Research on Schizophrenia: The Ascendance of the Glutamatergic Synapse. Am J Psychiatry 2020; 177:1119-1128. [PMID: 33256439 PMCID: PMC8011846 DOI: 10.1176/appi.ajp.2020.20101481] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Marques BL, Oliveira-Lima OC, Carvalho GA, de Almeida Chiarelli R, Ribeiro RI, Parreira RC, da Madeira Freitas EM, Resende RR, Klempin F, Ulrich H, Gomez RS, Pinto MCX. Neurobiology of glycine transporters: From molecules to behavior. Neurosci Biobehav Rev 2020; 118:97-110. [PMID: 32712279 DOI: 10.1016/j.neubiorev.2020.07.025] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 07/07/2020] [Accepted: 07/17/2020] [Indexed: 12/16/2022]
Abstract
Glycine transporters (GlyTs) are Na+/Cl--dependent neurotransmitter transporters, responsible for l-glycine uptake into the central nervous system. GlyTs are members of the solute carrier family 6 (SLC6) and comprise glycine transporter type 1 (SLC6A9; GlyT1) and glycine transporter type 2 (SLC6A5; Glyt2). GlyT1 and GlyT2 are expressed on both astrocytes and neurons, but their expression pattern in brain tissue is foremost related to neurotransmission. GlyT2 is markedly expressed in brainstem, spinal cord and cerebellum, where it is responsible for glycine uptake into glycinergic and GABAergic terminals. GlyT1 is abundant in neocortex, thalamus and hippocampus, where it is expressed in astrocytes, and involved in glutamatergic neurotransmission. Consequently, inhibition of GlyT1 transporters can modulate glutamatergic neurotransmission through NMDA receptors, suggesting an alternative therapeutic strategy. In this review, we focus on recent progress in the understanding of GlyTs role in brain function and in various diseases, such as epilepsy, hyperekplexia, neuropathic pain, drug addiction, schizophrenia and stroke, as well as in neurodegenerative disorders.
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Affiliation(s)
- Bruno Lemes Marques
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Onésia Cristina Oliveira-Lima
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Gustavo Almeida Carvalho
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Raphaela de Almeida Chiarelli
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Raul Izidoro Ribeiro
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Ricardo Cambraia Parreira
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Elis Marra da Madeira Freitas
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Rodrigo Ribeiro Resende
- Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | | | - Henning Ulrich
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Renato Santiago Gomez
- Departamento de Cirurgia, Faculdade de Medicina, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Mauro Cunha Xavier Pinto
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil.
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7
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Puhl MD, Desai RI, Takagi S, Presti KT, Doyle MR, Donahue RJ, Landino SM, Bergman J, Carlezon WA, Coyle JT. N-Methyl-d-aspartate receptor co-agonist availability affects behavioral and neurochemical responses to cocaine: insights into comorbid schizophrenia and substance abuse. Addict Biol 2019; 24:40-50. [PMID: 29168271 DOI: 10.1111/adb.12577] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Accepted: 10/16/2017] [Indexed: 12/19/2022]
Abstract
Both schizophrenia (SZ) and substance abuse (SA) exhibit significant heritability. Moreover, N-methyl-d-aspartate receptors (NMDARs) have been implicated in the pathophysiology of both SZ and SA. We hypothesize that the high prevalence of comorbid SA in SZ is due to dysfunction of NMDARs caused by shared risk genes. We used transgenic mice with a null mutation of the gene encoding serine racemase (SR), the enzyme that synthesizes the NMDAR co-agonist d-serine and an established risk gene for SZ, to recreate the pathology of SZ. We determined the effect of NMDAR hypofunction resulting from the absence of d-serine on motivated behavior by using intracranial self-stimulation and neurotransmitter release in the nucleus accumbens by using in vivo microdialysis. Compared with wild-type mice, SR-/- mice exhibited similar baseline intracranial self-stimulation thresholds but were less sensitive to the threshold-lowering (rewarding) and the performance-elevating (stimulant) effects of cocaine. While basal dopamine (DA) and glutamate release were elevated in the nucleus accumbens of SR-/- mice, cocaine-induced increases in DA and glutamate release were blunted. γ-Amino-butyric acid efflux was unaffected in the SR-/- mice. Together, these findings suggest that the impaired NMDAR function and a consequent decrease in sensitivity to cocaine effects on behavior are mediated by blunted DA and glutamate responses normally triggered by the drug. Projected to humans, NMDAR hypofunction due to mutations in SR or other genes impacting glutamatergic function in SZ may render abused substances less potent and effective, thus requiring higher doses to achieve a hedonic response, resulting in elevated drug exposure and increased dependence/addiction.
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Affiliation(s)
- Matthew D. Puhl
- Department of Psychiatry; Harvard Medical School; Boston MA USA
- Laboratory for Psychiatric and Molecular Neuroscience; McLean Hospital; Belmont MA USA
| | - Rajeev I. Desai
- Department of Psychiatry; Harvard Medical School; Boston MA USA
- Preclinical Pharmacology Laboratory; McLean Hospital; Belmont MA USA
| | - Shunsuke Takagi
- Department of Psychiatry; Harvard Medical School; Boston MA USA
- Laboratory for Psychiatric and Molecular Neuroscience; McLean Hospital; Belmont MA USA
- Department of Psychiatry and Behavioral Sciences, Graduate School of Medical and Dental Sciences; Tokyo Medical and Dental University; Tokyo Japan
| | - Kendall T. Presti
- Department of Psychiatry; Harvard Medical School; Boston MA USA
- Laboratory for Psychiatric and Molecular Neuroscience; McLean Hospital; Belmont MA USA
| | - Michelle R. Doyle
- Department of Psychiatry; Harvard Medical School; Boston MA USA
- Preclinical Pharmacology Laboratory; McLean Hospital; Belmont MA USA
| | - Rachel J. Donahue
- Department of Psychiatry; Harvard Medical School; Boston MA USA
- Behavioral Genetics Laboratory; McLean Hospital; Belmont MA USA
| | - Samantha M. Landino
- Department of Psychiatry; Harvard Medical School; Boston MA USA
- Behavioral Genetics Laboratory; McLean Hospital; Belmont MA USA
| | - Jack Bergman
- Department of Psychiatry; Harvard Medical School; Boston MA USA
- Preclinical Pharmacology Laboratory; McLean Hospital; Belmont MA USA
| | - William A. Carlezon
- Department of Psychiatry; Harvard Medical School; Boston MA USA
- Behavioral Genetics Laboratory; McLean Hospital; Belmont MA USA
| | - Joseph T. Coyle
- Department of Psychiatry; Harvard Medical School; Boston MA USA
- Laboratory for Psychiatric and Molecular Neuroscience; McLean Hospital; Belmont MA USA
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Zafra F, Ibáñez I, Bartolomé-Martín D, Piniella D, Arribas-Blázquez M, Giménez C. Glycine Transporters and Its Coupling with NMDA Receptors. ADVANCES IN NEUROBIOLOGY 2018; 16:55-83. [PMID: 28828606 DOI: 10.1007/978-3-319-55769-4_4] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Glycine plays two roles in neurotransmission. In caudal areas like the spinal cord and the brainstem, it acts as an inhibitory neurotransmitter, but in all regions of the CNS, it also works as a co-agonist with L-glutamate at N-methyl-D-aspartate receptors (NMDARs). The glycine fluxes in the CNS are regulated by two specific transporters for glycine, GlyT1 and GlyT2, perhaps with the cooperation of diverse neutral amino acid transporters like Asc-1 or SNAT5/SN2. While GlyT2 and Asc-1 are neuronal proteins, GlyT1 and SNAT5 are mainly astrocytic, although neuronal forms of GlyT1 also exist. GlyT1 has attracted considerable interest from the medical community and the pharmaceutical industry since compelling evidence indicates a clear association with the functioning of NMDARs, whose activity is decreased in various psychiatric illnesses. By controlling extracellular glycine, transporter inhibitors might potentiate the activity of NMDARs without activating excitotoxic processes. Physiologically, GlyT1 is a central actor in the cross talk between glutamatergic, glycinergic, dopaminergic, and probably other neurotransmitter systems. Many of these relationships begin to be unraveled by studies performed in recent years using genetic and pharmacological models. These studies are also clarifying the interactions between glycine, glycine transporters, and other co-agonists of the glycine site of NMDARs like D-serine. These findings are also relevant to understand the pathophysiology of devastating diseases like schizophrenia, depression, anxiety, epilepsy, stroke, and chronic pain.
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Affiliation(s)
- Francisco Zafra
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, C / Nicolás Cabrera, 1, 28049, Madrid, Spain. .,Centro de Investigación Biomédica en Red de Enfermedades Raras and IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain.
| | - Ignacio Ibáñez
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, C / Nicolás Cabrera, 1, 28049, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras and IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - David Bartolomé-Martín
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, C / Nicolás Cabrera, 1, 28049, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras and IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Dolores Piniella
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, C / Nicolás Cabrera, 1, 28049, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras and IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Marina Arribas-Blázquez
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, C / Nicolás Cabrera, 1, 28049, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras and IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Cecilio Giménez
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, C / Nicolás Cabrera, 1, 28049, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras and IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
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10
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Maksymetz J, Moran SP, Conn PJ. Targeting metabotropic glutamate receptors for novel treatments of schizophrenia. Mol Brain 2017; 10:15. [PMID: 28446243 PMCID: PMC5405554 DOI: 10.1186/s13041-017-0293-z] [Citation(s) in RCA: 95] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Accepted: 04/04/2017] [Indexed: 12/22/2022] Open
Abstract
Support for the N-methyl-D-aspartate receptor (NMDAR) hypofunction hypothesis of schizophrenia has led to increasing focus on restoring proper glutamatergic signaling as an approach for treatment of this devastating disease. The ability of metabotropic glutamate (mGlu) receptors to modulate glutamatergic neurotransmission has thus attracted considerable attention for the development of novel antipsychotics. Consisting of eight subtypes classified into three groups based on sequence homology, signal transduction, and pharmacology, the mGlu receptors provide a wide range of targets to modulate NMDAR function as well as glutamate release. Recently, allosteric modulators of mGlu receptors have been developed that allow unprecedented selectivity among subtypes, not just groups, facilitating the investigation of the effects of subtype-specific modulation. In preclinical animal models, positive allosteric modulators (PAMs) of the group I mGlu receptor mGlu5 have efficacy across all three symptom domains of schizophrenia (positive, negative, and cognitive). The discovery and development of mGlu5 PAMs that display unique signal bias suggests that efficacy can be retained while avoiding the neurotoxic effects of earlier compounds. Interestingly, mGlu1 negative allosteric modulators (NAMs) appear efficacious in positive symptom models of the disease but are still in early preclinical development. While selective group II mGlu receptor (mGlu2/3) agonists have reached clinical trials but were unsuccessful, specific mGlu2 or mGlu3 receptor targeting still hold great promise. Genetic studies implicated mGlu2 in the antipsychotic effects of group II agonists and mGlu2 PAMs have since entered into clinical trials. Additionally, mGlu3 appears to play an important role in cognition, may confer neuroprotective effects, and thus is a promising target to alleviate cognitive deficits in schizophrenia. Although group III mGlu receptors (mGlu4/6/7/8) have attracted less attention, mGlu4 agonists and PAMs appear to have efficacy across all three symptoms domains in preclinical models. The recent discovery of heterodimers comprising mGlu2 and mGlu4 may explain the efficacy of mGlu4 selective compounds but this remains to be determined. Taken together, compounds targeting mGlu receptors, specifically subtype-selective allosteric modulators, provide a compelling alternative approach to fill the unmet clinical needs for patients with schizophrenia.
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Affiliation(s)
- James Maksymetz
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232 USA
- Vanderbilt Center for Neuroscience Drug Discovery, Nashville, TN 37232 USA
| | - Sean P. Moran
- Vanderbilt Center for Neuroscience Drug Discovery, Nashville, TN 37232 USA
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN 37232 USA
| | - P. Jeffrey Conn
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232 USA
- Vanderbilt Center for Neuroscience Drug Discovery, Nashville, TN 37232 USA
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN 37232 USA
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Chesworth R, Corbit LH. Recent developments in the behavioural and pharmacological enhancement of extinction of drug seeking. Addict Biol 2017; 22:3-43. [PMID: 26687226 DOI: 10.1111/adb.12337] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Revised: 09/13/2015] [Accepted: 10/28/2015] [Indexed: 01/17/2023]
Abstract
One of the principal barriers to overcoming addiction is the propensity to relapse, even after months or years of abstinence. Relapse can be precipitated by cues and contexts associated with drug use; thus, decreasing the conditioned properties of these cues and contexts may assist in preventing relapse. The predictive power of drug cues and contexts can be reduced by repeatedly presenting them in the absence of the drug reinforcer, a process known as extinction. The potential of extinction to limit relapse has generated considerable interest and research over the past few decades. While pre-clinical animal models suggest extinction learning assists relapse prevention, treatment efficacy is often lacking when extinction learning principles are translated into clinical trials. Conklin and Tiffany (Addiction, 2002) suggest the lack of efficacy in clinical practice may be due to limited translation of procedures demonstrated through animal research and propose several methodological improvements to enhance extinction learning for drug addiction. This review will examine recent advances in the behavioural and pharmacological manipulation of extinction learning, based on research from pre-clinical models. In addition, the translation of pre-clinical findings-both those suggested by Conklin and Tiffany () and novel demonstrations from the past 13 years-into clinical trials and the efficacy of these methods in reducing craving and relapse, where available, will be discussed. Finally, we highlight areas where promising pre-clinical models have not yet been integrated into current clinical practice but, if applied, could improve upon existing behavioural and pharmacological methods.
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Hopf FW. Do specific NMDA receptor subunits act as gateways for addictive behaviors? GENES BRAIN AND BEHAVIOR 2016; 16:118-138. [PMID: 27706932 DOI: 10.1111/gbb.12348] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Revised: 09/27/2016] [Accepted: 10/03/2016] [Indexed: 12/19/2022]
Abstract
Addiction to alcohol and drugs is a major social and economic problem, and there is considerable interest in understanding the molecular mechanisms that promote addictive drives. A number of proteins have been identified that contribute to expression of addictive behaviors. NMDA receptors (NMDARs), a subclass of ionotropic glutamate receptors, have been of particular interest because their physiological properties make them an attractive candidate for gating induction of synaptic plasticity, a molecular change thought to mediate learning and memory. NMDARs are generally inactive at the hyperpolarized resting potentials of many neurons. However, given sufficient depolarization, NMDARs are activated and exhibit long-lasting currents with significant calcium permeability. Also, in addition to stimulating neurons by direct depolarization, NMDARs and their calcium signaling can allow strong and/or synchronized inputs to produce long-term changes in other molecules (such as AMPA-type glutamate receptors) which can last from days to years, binding internal and external stimuli in a long-term memory trace. Such memories could allow salient drug-related stimuli to exert strong control over future behaviors and thus promote addictive drives. Finally, NMDARs may themselves undergo plasticity, which can alter subsequent neuronal stimulation and/or the ability to induce plasticity. This review will address recent and past findings suggesting that NMDAR activity promotes drug- and alcohol-related behaviors, with a particular focus on GluN2B subunits as possible central regulators of many addictive behaviors, as well as newer studies examining the importance of non-canonical NMDAR subunits and endogenous NMDAR cofactors.
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Affiliation(s)
- F W Hopf
- Alcohol and Addiction Research Group, Department of Neurology, University of California at San Francisco, San Francisco, CA, USA
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Grigson PS. Addiction: A preclinical and clinical analysis. Brain Res Bull 2016; 123:1-4. [PMID: 27005437 PMCID: PMC5676458 DOI: 10.1016/j.brainresbull.2016.03.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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