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Taskiran SY, Taskiran M, Unal G, Golgeli A. Group I mGluRs positive allosteric modulators improved schizophrenia-related behavioral and molecular deficits in the Poly I:C rat model. Pharmacol Biochem Behav 2023:173593. [PMID: 37390974 DOI: 10.1016/j.pbb.2023.173593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 06/16/2023] [Accepted: 06/26/2023] [Indexed: 07/02/2023]
Abstract
RATIONALE Maternal polyinosinic-polycytidylic acid (Poly I:C) exposure leads to an increase in various proinflammatory cytokines and causes schizophrenia-like symptoms in offspring. In recent years, group I metabotropic glutamate receptors (mGluRs) have emerged as a potential target in the pathophysiology of schizophrenia. OBJECTIVES The aim of our study was to investigate the behavioral and molecular changes by using the mGlu1 receptor positive allosteric modulator (PAM) agent RO 67-7476, and the negative allosteric modulator (NAM) agent JNJ 16259685 and the mGlu5 receptor PAM agent VU-29, and NAM agent fenobam in the Poly I:C-induced schizophrenia model in rats. METHODS Female Wistar albino rats were treated with Poly I:C on day 14 of gestation after mating. On the postnatal day (PND) 35, 56 and 84, behavioral tests were performed in the male offspring. On the PND84, brain tissue was collected and the level of proinflammatory cytokines was determined by ELISA method. RESULTS Poly I:C caused impairments in all behavioral tests and increased the levels of proinflammatory cytokines. While PAM agents caused significant improvements in prepulse inhibition (PPI), novel object recognition (NOR), spontaneous alternation and reference memory tests, they brought the levels of proinflammatory cytokines closer to the control group. NAM agents were ineffective on behavioral tests. It was observed that PAM agents significantly improved Poly I:C-induced disruption in behavioral and molecular analyses. CONCLUSIONS These results suggest that PAM agents, particularly the mGlu5 receptor VU-29, are also promising and could be a potential target in schizophrenia.
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Affiliation(s)
| | - Mehmet Taskiran
- Department of Biology, Faculty of Science, Erciyes University, Kayseri, Turkey.
| | - Gokhan Unal
- Department of Pharmacology, Faculty of Pharmacy, Erciyes University, Kayseri, Turkey.
| | - Asuman Golgeli
- Department of Physiology, Faculty of Medicine, Erciyes University, Kayseri, Turkey.
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de Souza JM, Ferreira-Vieira TH, Maciel EMA, Silva NC, Lima IBQ, Doria JG, Olmo IG, Ribeiro FM. mGluR5 ablation leads to age-related synaptic plasticity impairments and does not improve Huntington’s disease phenotype. Sci Rep 2022; 12:8982. [PMID: 35643779 PMCID: PMC9148310 DOI: 10.1038/s41598-022-13029-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 05/18/2022] [Indexed: 11/29/2022] Open
Abstract
Glutamate receptors, including mGluR5, are involved in learning and memory impairments triggered by aging and neurological diseases. However, each condition involves distinct molecular mechanisms. It is still unclear whether the mGluR5 cell signaling pathways involved in normal brain aging differ from those altered due to neurodegenerative disorders. Here, we employed wild type (WT), mGluR5−/−, BACHD, which is a mouse model of Huntington’s Disease (HD), and mGluR5−/−/BACHD mice, at the ages of 2, 6 and 12 months, to distinguish the mGluR5-dependent cell signaling pathways involved in aging and neurodegenerative diseases. We demonstrated that the memory impairment exhibited by mGluR5−/− mice is accompanied by massive neuronal loss and decreased dendritic spine density in the hippocampus, similarly to BACHD and BACHD/mGluR5−/− mice. Moreover, mGluR5 ablation worsens some of the HD-related alterations. We also show that mGluR5−/− and BACHD/mGluR5−/− mice have decreased levels of PSD95, BDNF, and Arc/Arg3.1, whereas BACHD mice are mostly spared. PSD95 expression was affected exclusively by mGluR5 ablation in the aging context, making it a potential target to treat age-related alterations. Taken together, we reaffirm the relevance of mGluR5 for memory and distinguish the mGluR5 cell signaling pathways involved in normal brain aging from those implicated in HD.
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3
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Esterlis I, DeBonee S, Cool R, Holmes S, Baldassari SR, Maruff P, Pietrzak RH, Davis MT. Differential Role of mGluR5 in Cognitive Processes in Posttraumatic Stress Disorder and Major Depression. CHRONIC STRESS (THOUSAND OAKS, CALIF.) 2022; 6:24705470221105804. [PMID: 35958037 PMCID: PMC9358555 DOI: 10.1177/24705470221105804] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 05/23/2022] [Indexed: 11/16/2022]
Abstract
Background A robust literature supports the role of the metabotropic glutamate receptor type 5 (mGluR5) in cognitive functioning. mGluR5 is also implicated in the pathophysiology of posttraumatic stress disorder (PTSD) and major depressive disorder (MDD), which are characterized by cognitive alterations. However, the relationship between mGluR5 and cognition in MDD and PTSD has not yet been directly investigated. To address this gap, we examined the relationship between in vivo mGluR5 availability and cognition in PTSD, MDD, and matched healthy adults (HA). Methods Individuals with PTSD (N = 28) and MDD (N = 21), and HA (N = 28) were matched for age, gender, and smoking status. Participants completed 18F-FPEB positron emission tomography (PET) scan, psychiatric and cognitive assessments. Results Across models examining the relationship between mGluR5 availability and different domains of cognition across diagnostic groups, only the interaction of diagnosis*attention was significant (F 4,64 = 3.011, P = .024). Higher mGluR5 availability was associated with poorer attention in PTSD in 4 frontolimbic regions of interests (ROI's: OFC (r = -.441, P = .016), vmPFC (r = -.408, P = .028), dlPFC (r = -.421, P = .023), hippocampus (r = -.422, P = .025). By contrast, mGluR5 availability in the MDD group was positively related to Attention (ATTN) in the OFC (r = .590, P = .006), vmPFC (r = .653, P = .002), and dlPFC (r = .620, P = .004). Findings in the hippocampus for MDD followed the same pattern but did not survive correction for multiple comparisons (r = .480, P = .036). ATTN and mGluR5 availability were not significantly related in the HA group. Of note, in MANOVA analyses group*ATTN interaction results in the OFC did not survive multiple comparisons (P = .046). All other findings survived correction for multiple comparisons and remained significant when covarying for potential confounds (eg, depressed mood). Conclusions We observed a significant relationship between frontolimbic mGluR5 availability and performance on tests of attention in individuals with MDD and PTSD. This finding aligns with animal work showing dysregulation in mGluR5 in cognitive functioning, and differed as a function of diagnosis. Results suggest interventions targeting mGluR5 may help bolster cognitive difficulties, highlighting the importance of employing different mGluR5 directed treatment strategies in MDD and PTSD.
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Affiliation(s)
- Irina Esterlis
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
- Department of Psychology, Yale University, New Haven, CT, USA
- National Center for Posttraumatic Stress Disorder, U.S. Department of Veterans Affairs, West Haven, CT, USA
| | - Sarah DeBonee
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
| | - Ryan Cool
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
| | - Sophie Holmes
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
- Department of Psychology, Yale University, New Haven, CT, USA
- National Center for Posttraumatic Stress Disorder, U.S. Department of Veterans Affairs, West Haven, CT, USA
| | - Stephen R. Baldassari
- Department of Internal Medicine, Section of Pulmonary, Critical Care, and Sleep Medicine, Yale University School of Medicine, New Haven, CT, USA
- Program in Addiction Medicine, Yale University School of Medicine, New Haven, CT, USA
| | | | - Robert H. Pietrzak
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
- National Center for Posttraumatic Stress Disorder, U.S. Department of Veterans Affairs, West Haven, CT, USA
| | - Margaret T. Davis
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
- Department of Psychology, Yale University, New Haven, CT, USA
- National Center for Posttraumatic Stress Disorder, U.S. Department of Veterans Affairs, West Haven, CT, USA
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4
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Mahalakshmi AM, Ray B, Tuladhar S, Hediyal TA, Raj P, Rathipriya AG, Qoronfleh MW, Essa MM, Chidambaram SB. Impact of Pharmacological and Non-Pharmacological Modulators on Dendritic Spines Structure and Functions in Brain. Cells 2021; 10:3405. [PMID: 34943913 PMCID: PMC8699406 DOI: 10.3390/cells10123405] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 11/27/2021] [Accepted: 11/29/2021] [Indexed: 12/12/2022] Open
Abstract
Dendritic spines are small, thin, hair-like protrusions found on the dendritic processes of neurons. They serve as independent compartments providing large amplitudes of Ca2+ signals to achieve synaptic plasticity, provide sites for newer synapses, facilitate learning and memory. One of the common and severe complication of neurodegenerative disease is cognitive impairment, which is said to be closely associated with spine pathologies viz., decreased in spine density, spine length, spine volume, spine size etc. Many treatments targeting neurological diseases have shown to improve the spine structure and distribution. However, concise data on the various modulators of dendritic spines are imperative and a need of the hour. Hence, in this review we made an attempt to consolidate the effects of various pharmacological (cholinergic, glutamatergic, GABAergic, serotonergic, adrenergic, and dopaminergic agents) and non-pharmacological modulators (dietary interventions, enriched environment, yoga and meditation) on dendritic spines structure and functions. These data suggest that both the pharmacological and non-pharmacological modulators produced significant improvement in dendritic spine structure and functions and in turn reversing the pathologies underlying neurodegeneration. Intriguingly, the non-pharmacological approaches have shown to improve intellectual performances both in preclinical and clinical platforms, but still more technology-based evidence needs to be studied. Thus, we conclude that a combination of pharmacological and non-pharmacological intervention may restore cognitive performance synergistically via improving dendritic spine number and functions in various neurological disorders.
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Affiliation(s)
- Arehally M. Mahalakshmi
- Department of Pharmacology, JSS College of Pharmacy, JSS Academy of Higher Education & Research, Mysuru 570015, Karnataka, India; (A.M.M.); (B.R.); (S.T.); (T.A.H.); (P.R.)
- SIG-Brain, Behaviour and Cognitive Neurosciences Research (BBRC), JSS Academy of Higher Education & Research, Mysuru 570015, Karnataka, India
| | - Bipul Ray
- Department of Pharmacology, JSS College of Pharmacy, JSS Academy of Higher Education & Research, Mysuru 570015, Karnataka, India; (A.M.M.); (B.R.); (S.T.); (T.A.H.); (P.R.)
- Centre for Experimental Pharmacology and Toxicology, Central Animal Facility, JSS Academy of Higher Education & Research, Mysuru 570015, Karnataka, India
| | - Sunanda Tuladhar
- Department of Pharmacology, JSS College of Pharmacy, JSS Academy of Higher Education & Research, Mysuru 570015, Karnataka, India; (A.M.M.); (B.R.); (S.T.); (T.A.H.); (P.R.)
- Centre for Experimental Pharmacology and Toxicology, Central Animal Facility, JSS Academy of Higher Education & Research, Mysuru 570015, Karnataka, India
| | - Tousif Ahmed Hediyal
- Department of Pharmacology, JSS College of Pharmacy, JSS Academy of Higher Education & Research, Mysuru 570015, Karnataka, India; (A.M.M.); (B.R.); (S.T.); (T.A.H.); (P.R.)
- Centre for Experimental Pharmacology and Toxicology, Central Animal Facility, JSS Academy of Higher Education & Research, Mysuru 570015, Karnataka, India
| | - Praveen Raj
- Department of Pharmacology, JSS College of Pharmacy, JSS Academy of Higher Education & Research, Mysuru 570015, Karnataka, India; (A.M.M.); (B.R.); (S.T.); (T.A.H.); (P.R.)
| | | | - M. Walid Qoronfleh
- Q3CG Research Institute (QRI), Research and Policy Division, 7227 Rachel Drive, Ypsilanti, MI 48917, USA;
| | - Musthafa Mohamed Essa
- Department of Food Science and Nutrition, CAMS, Sultan Qaboos University, Muscat 123, Oman
- Ageing and Dementia Research Group, Sultan Qaboos University, Muscat 123, Oman
- Biomedical Sciences Department, University of Pacific, Sacramento, CA 95211, USA
| | - Saravana Babu Chidambaram
- Department of Pharmacology, JSS College of Pharmacy, JSS Academy of Higher Education & Research, Mysuru 570015, Karnataka, India; (A.M.M.); (B.R.); (S.T.); (T.A.H.); (P.R.)
- SIG-Brain, Behaviour and Cognitive Neurosciences Research (BBRC), JSS Academy of Higher Education & Research, Mysuru 570015, Karnataka, India
- Centre for Experimental Pharmacology and Toxicology, Central Animal Facility, JSS Academy of Higher Education & Research, Mysuru 570015, Karnataka, India
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5
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Smiley CE, McGonigal JT, Nimchuk KE, Gass JT. Optogenetic manipulation of the prelimbic cortex during fear memory reconsolidation alters fear extinction in a preclinical model of comorbid PTSD/AUD. Psychopharmacology (Berl) 2021; 238:3193-3206. [PMID: 34347171 DOI: 10.1007/s00213-021-05935-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Accepted: 07/12/2021] [Indexed: 12/27/2022]
Abstract
RATIONALE AND OBJECTIVE Post-traumatic stress disorder (PTSD) and alcohol use disorder (AUD) are disorders of learning and memory that often occur comorbidly. Exposure to trauma-related cues can increase alcohol intake in PTSD patients that are using alcohol to self-medicate. The recurrence of anxiety symptoms with subsequent alcohol use may initiate a destructive cycle where stress and alcohol exposure impair the function of the prefrontal cortex (PFC). While the incidence of these disorders has steadily increased, current therapies and treatments often lack efficacy. Thus, investigation into the underlying neurocircuitry responsible for the establishment and maintenance of these disorders is necessary to develop novel treatment targets. METHODS The present study examined the effects of ethanol exposure on the ability to create new learned associations around previously conditioned fear cues in a rat model. Animals were exposed to fear conditioning followed by chronic intermittent ethanol to translationally model trauma exposure followed by alcohol abuse. Optogenetics was used to inhibit the prelimbic (PrL) or infralimbic (IfL) cortex during fear memory reconsolidation, and fear behaviors were measured during subsequent extinction and spontaneous recovery tests. Results and conclusion Chronic ethanol exposure led to deficits in fear extinction learning and increased freezing during spontaneous recovery, both of which were prevented following inhibition of the PrL, but not the IfL, during memory reconsolidation. These results support the involvement of the PrL in fear learning and memory, and strongly suggest that the PrL could serve as a potential target for the treatment of the learning and memory deficits that occur following exposure to stress and alcohol.
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Affiliation(s)
- C E Smiley
- Department of Neuroscience, Basic Science Building, Medical University of South Carolina, 173 Ashley Avenue, Room 403, Charleston, SC, 29425, USA.
| | - J T McGonigal
- Department of Neuroscience, Basic Science Building, Medical University of South Carolina, 173 Ashley Avenue, Room 403, Charleston, SC, 29425, USA
| | - K E Nimchuk
- Department of Neuroscience, Basic Science Building, Medical University of South Carolina, 173 Ashley Avenue, Room 403, Charleston, SC, 29425, USA
| | - J T Gass
- Department of Neuroscience, Basic Science Building, Medical University of South Carolina, 173 Ashley Avenue, Room 403, Charleston, SC, 29425, USA.,Department of Biomedical Sciences, James H. Quillen College of Medicine & VA Medical Center, PO Box 70582, Johnson City, TN, 37614, USA
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6
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Connecting the Neurobiology of Developmental Brain Injury: Neuronal Arborisation as a Regulator of Dysfunction and Potential Therapeutic Target. Int J Mol Sci 2021; 22:ijms22158220. [PMID: 34360985 PMCID: PMC8348801 DOI: 10.3390/ijms22158220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 07/23/2021] [Accepted: 07/28/2021] [Indexed: 11/17/2022] Open
Abstract
Neurodevelopmental disorders can derive from a complex combination of genetic variation and environmental pressures on key developmental processes. Despite this complex aetiology, and the equally complex array of syndromes and conditions diagnosed under the heading of neurodevelopmental disorder, there are parallels in the neuropathology of these conditions that suggest overlapping mechanisms of cellular injury and dysfunction. Neuronal arborisation is a process of dendrite and axon extension that is essential for the connectivity between neurons that underlies normal brain function. Disrupted arborisation and synapse formation are commonly reported in neurodevelopmental disorders. Here, we summarise the evidence for disrupted neuronal arborisation in these conditions, focusing primarily on the cortex and hippocampus. In addition, we explore the developmentally specific mechanisms by which neuronal arborisation is regulated. Finally, we discuss key regulators of neuronal arborisation that could link to neurodevelopmental disease and the potential for pharmacological modification of arborisation and the formation of synaptic connections that may provide therapeutic benefit in the future.
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7
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Gonzalez-Lozano MA, Wortel J, van der Loo RJ, van Weering JRT, Smit AB, Li KW. Reduced mGluR5 Activity Modulates Mitochondrial Function. Cells 2021; 10:cells10061375. [PMID: 34199502 PMCID: PMC8228325 DOI: 10.3390/cells10061375] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 05/23/2021] [Accepted: 05/31/2021] [Indexed: 11/30/2022] Open
Abstract
The metabotropic glutamate receptor 5 (mGluR5) is an essential modulator of synaptic plasticity, learning and memory; whereas in pathological conditions, it is an acknowledged therapeutic target that has been implicated in multiple brain disorders. Despite robust pre-clinical data, mGluR5 antagonists failed in several clinical trials, highlighting the need for a better understanding of the mechanisms underlying mGluR5 function. In this study, we dissected the molecular synaptic modulation mediated by mGluR5 using genetic and pharmacological mouse models to chronically and acutely reduce mGluR5 activity. We found that next to dysregulation of synaptic proteins, the major regulation in protein expression in both models concerned specific processes in mitochondria, such as oxidative phosphorylation. Second, we observed morphological alterations in shape and area of specifically postsynaptic mitochondria in mGluR5 KO synapses using electron microscopy. Third, computational and biochemical assays suggested an increase of mitochondrial function in neurons, with increased level of NADP/H and oxidative damage in mGluR5 KO. Altogether, our observations provide diverse lines of evidence of the modulation of synaptic mitochondrial function by mGluR5. This connection suggests a role for mGluR5 as a mediator between synaptic activity and mitochondrial function, a finding which might be relevant for the improvement of the clinical potential of mGluR5.
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Affiliation(s)
- Miguel A. Gonzalez-Lozano
- Center for Neurogenomics and Cognitive Research, Department of Molecular and Cellular Neurobiology, Amsterdam Neuroscience, Vrije Universiteit Amsterdam, 1081 Amsterdam, The Netherlands; (R.J.v.d.L.); (A.B.S.)
- Correspondence: (M.A.G.-L.); (K.W.L.)
| | - Joke Wortel
- Center for Neurogenomics and Cognitive Research, Department of Functional Genomics, Amsterdam Neuroscience, Vrije Universiteit Amsterdam, 1081 Amsterdam, The Netherlands; (J.W.); (J.R.T.v.W.)
| | - Rolinka J. van der Loo
- Center for Neurogenomics and Cognitive Research, Department of Molecular and Cellular Neurobiology, Amsterdam Neuroscience, Vrije Universiteit Amsterdam, 1081 Amsterdam, The Netherlands; (R.J.v.d.L.); (A.B.S.)
| | - Jan R. T. van Weering
- Center for Neurogenomics and Cognitive Research, Department of Functional Genomics, Amsterdam Neuroscience, Vrije Universiteit Amsterdam, 1081 Amsterdam, The Netherlands; (J.W.); (J.R.T.v.W.)
- Center for Neurogenomics and Cognitive Research, Department of Clinical Genetics, Amsterdam Neuroscience, Amsterdam UMC location VUmc, 1081 Amsterdam, The Netherlands
| | - August B. Smit
- Center for Neurogenomics and Cognitive Research, Department of Molecular and Cellular Neurobiology, Amsterdam Neuroscience, Vrije Universiteit Amsterdam, 1081 Amsterdam, The Netherlands; (R.J.v.d.L.); (A.B.S.)
| | - Ka Wan Li
- Center for Neurogenomics and Cognitive Research, Department of Molecular and Cellular Neurobiology, Amsterdam Neuroscience, Vrije Universiteit Amsterdam, 1081 Amsterdam, The Netherlands; (R.J.v.d.L.); (A.B.S.)
- Correspondence: (M.A.G.-L.); (K.W.L.)
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8
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Telias M. Pharmacological Treatments for Fragile X Syndrome Based on Synaptic Dysfunction. Curr Pharm Des 2020; 25:4394-4404. [PMID: 31682210 DOI: 10.2174/1381612825666191102165206] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2019] [Accepted: 10/31/2019] [Indexed: 12/29/2022]
Abstract
BACKGROUND Fragile X syndrome (FXS) is the most common form of monogenic hereditary cognitive impairment, including intellectual disability, autism, hyperactivity, and epilepsy. METHODS This article reviews the literature pertaining to the role of synaptic dysfunction in FXS. RESULTS In FXS, synaptic dysfunction alters the excitation-inhibition ratio, dysregulating molecular and cellular processes underlying cognition, learning, memory, and social behavior. Decades of research have yielded important hypotheses that could explain, at least in part, the development of these neurological disorders in FXS patients. However, the main goal of translating lab research in animal models to pharmacological treatments in the clinic has been so far largely unsuccessful, leaving FXS a still incurable disease. CONCLUSION In this concise review, we summarize and analyze the main hypotheses proposed to explain synaptic dysregulation in FXS, by reviewing the scientific evidence that led to pharmaceutical clinical trials and their outcome.
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Affiliation(s)
- Michael Telias
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, United States
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9
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Biased agonism and allosteric modulation of metabotropic glutamate receptor 5. Clin Sci (Lond) 2018; 132:2323-2338. [PMID: 30389826 DOI: 10.1042/cs20180374] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 10/03/2018] [Accepted: 10/05/2018] [Indexed: 12/18/2022]
Abstract
Metabotropic glutamate receptors belong to class C G-protein-coupled receptors and consist of eight subtypes that are ubiquitously expressed throughout the central nervous system. In recent years, the metabotropic glutamate receptor subtype 5 (mGlu5) has emerged as a promising target for a broad range of psychiatric and neurological disorders. Drug discovery programs targetting mGlu5 are primarily focused on development of allosteric modulators that interact with sites distinct from the endogenous agonist glutamate. Significant efforts have seen mGlu5 allosteric modulators progress into clinical trials; however, recent failures due to lack of efficacy or adverse effects indicate a need for a better understanding of the functional consequences of mGlu5 allosteric modulation. Biased agonism is an interrelated phenomenon to allosterism, describing how different ligands acting through the same receptor can differentially influence signaling to distinct transducers and pathways. Emerging evidence demonstrates that allosteric modulators can induce biased pharmacology at the level of intrinsic agonism as well as through differential modulation of orthosteric agonist-signaling pathways. Here, we present key considerations in the discovery and development of mGlu5 allosteric modulators and the opportunities and pitfalls offered by biased agonism and modulation.
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10
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Isherwood SN, Robbins TW, Dalley JW, Pekcec A. Bidirectional variation in glutamate efflux in the medial prefrontal cortex induced by selective positive and negative allosteric mGluR5 modulators. J Neurochem 2018; 145:111-124. [PMID: 29315577 PMCID: PMC5972455 DOI: 10.1111/jnc.14290] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 12/18/2017] [Accepted: 12/27/2017] [Indexed: 01/30/2023]
Abstract
Dysregulation of prefrontal cortical glutamatergic signalling via NMDA receptor hypofunction has been implicated in cognitive dysfunction and impaired inhibitory control in such neuropsychiatric disorders as schizophrenia, attention‐deficit hyperactivity disorder and drug addiction. Although NMDA receptors functionally interact with metabotropic glutamate receptor 5 (mGluR5), the consequence of this interaction for glutamate release in the prefrontal cortex (PFC) remains unknown. We therefore investigated the effects of positive and negative allosteric mGluR5 modulation on changes in extracellular glutamate efflux in the medial PFC (mPFC) induced by systemic administration of the non‐competitive NMDA receptor antagonist dizocilpine (or MK801) in rats. Extracellular glutamate efflux was measured following systemic administration of the positive allosteric mGluR5 modulator [S‐(4‐Fluoro‐phenyl)‐{3‐[3‐(4‐fluoro‐phenyl)‐[1,2,4]‐oxadiazol‐5‐yl]‐piperidin‐1‐yl}‐methanone] (ADX47273; 100 mg/kg, p.o.) and negative allosteric mGluR5 modulator [2‐chloro‐4‐{[1‐(4‐fluorophenyl)‐2,5‐dimethyl‐1H‐imidazol‐4‐yl]ethynyl}pyridine] (RO4917523; 0.3 mg/kg, p.o.), using a wireless glutamate biosensor in awake, freely moving rats. The effect of MK801 (0.03–0.06 mg/kg, s.c.) on mPFC glutamate efflux was also investigated in addition to the effects of MK801 (0.03 mg/kg, s.c.) following ADX47273 (100 mg/kg, p.o.) pre‐treatment. ADX47273 produced a sustained increase in glutamate efflux and increased the effect of NMDA receptor antagonism on glutamate efflux in the mPFC. In contrast, negative allosteric mGluR5 modulation with RO4917523 decreased glutamate efflux in the mPFC. These findings indicate that positive and negative allosteric mGluR5 modulators produce long lasting and opposing actions on extracellular glutamate efflux in the mPFC. Positive and negative allosteric modulators of mGluR5 may therefore be viable therapeutic agents to correct abnormalities in glutamatergic signalling present in a range of neuropsychiatric disorders. ![]()
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Affiliation(s)
- Sarah N Isherwood
- Boehringer Ingelheim Pharma GmbH & Co. KG, Div. Research Germany, Biberach an der Riss, Germany.,Behavioural and Clinical Neuroscience Institute, University of Cambridge, Cambridge, UK
| | - Trevor W Robbins
- Behavioural and Clinical Neuroscience Institute, University of Cambridge, Cambridge, UK.,Department of Psychology, University of Cambridge, Cambridge, UK
| | - Jeffrey W Dalley
- Behavioural and Clinical Neuroscience Institute, University of Cambridge, Cambridge, UK.,Department of Psychology, University of Cambridge, Cambridge, UK.,Department of Psychiatry, University of Cambridge, Cambridge, UK
| | - Anton Pekcec
- Boehringer Ingelheim Pharma GmbH & Co. KG, Div. Research Germany, Biberach an der Riss, Germany
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11
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Abstract
Dendritic spines are diverse and plastic components of the neuronal cell apparatus and are highly responsive to trophic factors during both development and adulthood. Diolistic labeling of neurons with lipophilic fluorescent dyes, coupled with advanced high-resolution microscopy methods, provides robust labeling of dendritic spines for assessment of their density and morphology. Here, we describe a method for labeling of dendritic spines using diolistic labeling in ex vivo brain slices, visualization using confocal laser scanning microscopy, deconvolution, and analysis using the Surpass module of Bitplane Imaris software.
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Affiliation(s)
- M Foster Olive
- Department of Psychology, Arizona State University, Tempe, AZ, USA.
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12
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Reker AN, Oliveros A, Sullivan JM, Nahar L, Hinton DJ, Kim T, Bruner RC, Choi DS, Goeders NE, Nam HW. Neurogranin in the nucleus accumbens regulates NMDA receptor tolerance and motivation for ethanol seeking. Neuropharmacology 2017; 131:58-67. [PMID: 29225043 DOI: 10.1016/j.neuropharm.2017.12.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2017] [Revised: 11/08/2017] [Accepted: 12/05/2017] [Indexed: 01/15/2023]
Abstract
Dysfunction of N-methyl-d-aspartate receptor (NMDAR) signaling in the nucleus accumbens (NAc) has been implicated in the pathophysiology of alcohol use disorders (AUD). Neurogranin (Ng), a calmodulin-binding protein, is exclusively expressed in the post-synapse, and mediates NMDAR driven synaptic plasticity by regulating the calcium-calmodulin (Ca2+-CaM) pathway. To study the functional role of Ng in AUD, we administrated behavior tests including Pavlovian instrument transfer (PIT), operant conditioning, and rotarod test using Ng null mice (Ng-/- mice). We used adeno-associated virus (AAV)-mediated Ng expression and pharmacological manipulation to validate behavioral responses in Ng-/- mice. The results from our multidisciplinary approaches demonstrated that deficit of Ng increases tolerance to NMDAR inhibition and elicit faster cue reactivity during PIT without changes in ethanol reward. Operant conditioning results demonstrated that Ng-/- mice self-administered significantly more ethanol and displayed reduced sensitivity to aversive motivation. We identified that ethanol exposure decreases mGluR5 (metabotropic glutamate receptor 5) expression in the NAc of Ng-/- mice and pharmacological inhibition of mGluR5 reverses NMDAR desensitization in Ng-/- mice. Together these findings specifically suggest that accumbal Ng plays an essential role in the counterbalance between NMDAR and mGluR5 signaling; which alters NMDAR resistance, and thereby altering aversive motivation for ethanol and may ultimately contribute to susceptibility for alcohol addiction.
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Affiliation(s)
- Ashlie N Reker
- Department of Pharmacology, Toxicology, and Neuroscience, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA
| | - Alfredo Oliveros
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
| | - John M Sullivan
- Department of Pharmacology, Toxicology, and Neuroscience, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA
| | - Lailun Nahar
- Department of Pharmacology, Toxicology, and Neuroscience, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA
| | - David J Hinton
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
| | - Taehyun Kim
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
| | - Robert C Bruner
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
| | - Doo-Sup Choi
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
| | - Nicholas E Goeders
- Department of Pharmacology, Toxicology, and Neuroscience, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA
| | - Hyung W Nam
- Department of Pharmacology, Toxicology, and Neuroscience, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA.
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Opposite Effects of mGluR1a and mGluR5 Activation on Nucleus Accumbens Medium Spiny Neuron Dendritic Spine Density. PLoS One 2016; 11:e0162755. [PMID: 27618534 PMCID: PMC5019418 DOI: 10.1371/journal.pone.0162755] [Citation(s) in RCA: 109] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 08/26/2016] [Indexed: 11/19/2022] Open
Abstract
The group I metabotropic glutamate receptors (mGluR1a and mGluR5) are important modulators of neuronal structure and function. Although these receptors share common signaling pathways, they are capable of having distinct effects on cellular plasticity. We investigated the individual effects of mGluR1a or mGluR5 activation on dendritic spine density in medium spiny neurons in the nucleus accumbens (NAc), which has become relevant with the potential use of group I mGluR based therapeutics in the treatment of drug addiction. We found that systemic administration of mGluR subtype-specific positive allosteric modulators had opposite effects on dendritic spine densities. Specifically, mGluR5 positive modulation decreased dendritic spine densities in the NAc shell and core, but was without effect in the dorsal striatum, whereas increased spine densities in the NAc were observed with mGluR1a positive modulation. Additionally, direct activation of mGluR5 via CHPG administration into the NAc also decreased the density of dendritic spines. These data provide insight on the ability of group I mGluRs to induce structural plasticity in the NAc and demonstrate that the group I mGluRs are capable of producing not just distinct, but opposing, effects on dendritic spine density.
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