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Sample records for glutamate receptor delta2

  1. The amino-terminal domain of glutamate receptor {delta}2 triggers presynaptic differentiation

    SciTech Connect

    Uemura, Takeshi; Mishina, Masayoshi

    2008-12-26

    Glutamate receptor (GluR) {delta}2 selectively expressed in cerebellar Purkinje cells plays key roles in synapse formation, long-term depression and motor learning. We propose that GluR{delta}2 regulates synapse formation by making a physical linkage between the active zone and postsynaptic density. To examine the issue, GluR{delta}2-transfected 293T cells were cultured with cerebellar neurons. We found numerous punctate signals for presynaptic markers on the surface of 293T cells expressing GluR{delta}2. The presynaptic specializations induced by GluR{delta}2 were capable of exo- and endocytosis as indicated by FM1-43 dye labeling. Replacement of the extracellular N-terminal domain (NTD) of GluR{delta}2 with that of the AMPA receptor GluR{alpha}1 abolished the inducing activity. The NTD of GluR{delta}2 fused to the immunoglobulin constant region successfully induced the accumulation of presynaptic specializations on the surface of beads bearing the fusion protein. These results suggest that GluR{delta}2 triggers presynaptic differentiation by direct interaction with presynaptic components through the NTD.

  2. Cbln1 is a ligand for an orphan glutamate receptor delta2, a bidirectional synapse organizer.

    PubMed

    Matsuda, Keiko; Miura, Eriko; Miyazaki, Taisuke; Kakegawa, Wataru; Emi, Kyoichi; Narumi, Sakae; Fukazawa, Yugo; Ito-Ishida, Aya; Kondo, Tetsuro; Shigemoto, Ryuichi; Watanabe, Masahiko; Yuzaki, Michisuke

    2010-04-16

    Cbln1, secreted from cerebellar granule cells, and the orphan glutamate receptor delta2 (GluD2), expressed by Purkinje cells, are essential for synapse integrity between these neurons in adult mice. Nevertheless, no endogenous binding partners for these molecules have been identified. We found that Cbln1 binds directly to the N-terminal domain of GluD2. GluD2 expression by postsynaptic cells, combined with exogenously applied Cbln1, was necessary and sufficient to induce new synapses in vitro and in the adult cerebellum in vivo. Further, beads coated with recombinant Cbln1 directly induced presynaptic differentiation and indirectly caused clustering of postsynaptic molecules via GluD2. These results indicate that the Cbln1-GluD2 complex is a unique synapse organizer that acts bidirectionally on both pre- and postsynaptic components.

  3. A new mouse allele of glutamate receptor delta 2 with cerebellar atrophy and progressive ataxia.

    PubMed

    Miyoshi, Yuka; Yoshioka, Yoshichika; Suzuki, Kinuko; Miyazaki, Taisuke; Koura, Minako; Saigoh, Kazumasa; Kajimura, Naoko; Monobe, Yoko; Kusunoki, Susumu; Matsuda, Junichiro; Watanabe, Masahiko; Hayasaka, Naoto

    2014-01-01

    Spinocerebellar degenerations (SCDs) are a large class of sporadic or hereditary neurodegenerative disorders characterized by progressive motion defects and degenerative changes in the cerebellum and other parts of the CNS. Here we report the identification and establishment from a C57BL/6J mouse colony of a novel mouse line developing spontaneous progressive ataxia, which we refer to as ts3. Frequency of the phenotypic expression was consistent with an autosomal recessive Mendelian trait of inheritance, suggesting that a single gene mutation is responsible for the ataxic phenotype of this line. The onset of ataxia was observed at about three weeks of age, which slowly progressed until the hind limbs became entirely paralyzed in many cases. Micro-MRI study revealed significant cerebellar atrophy in all the ataxic mice, although individual variations were observed. Detailed histological analyses demonstrated significant atrophy of the anterior folia with reduced granule cells (GC) and abnormal morphology of cerebellar Purkinje cells (PC). Study by ultra-high voltage electron microscopy (UHVEM) further indicated aberrant morphology of PC dendrites and their spines, suggesting both morphological and functional abnormalities of the PC in the mutants. Immunohistochemical studies also revealed defects in parallel fiber (PF)-PC synapse formation and abnormal distal extension of climbing fibers (CF). Based on the phenotypic similarities of the ts3 mutant with other known ataxic mutants, we performed immunohistological analyses and found that expression levels of two genes and their products, glutamate receptor delta2 (grid2) and its ligand, cerebellin1 (Cbln1), are significantly reduced or undetectable. Finally, we sequenced the candidate genes and detected a large deletion in the coding region of the grid2 gene. Our present study suggests that ts3 is a new allele of the grid2 gene, which causes similar but different phenotypes as compared to other grid2 mutants.

  4. A New Mouse Allele of Glutamate Receptor Delta 2 with Cerebellar Atrophy and Progressive Ataxia

    PubMed Central

    Miyoshi, Yuka; Yoshioka, Yoshichika; Suzuki, Kinuko; Miyazaki, Taisuke; Koura, Minako; Saigoh, Kazumasa; Kajimura, Naoko; Monobe, Yoko; Kusunoki, Susumu; Matsuda, Junichiro; Watanabe, Masahiko; Hayasaka, Naoto

    2014-01-01

    Spinocerebellar degenerations (SCDs) are a large class of sporadic or hereditary neurodegenerative disorders characterized by progressive motion defects and degenerative changes in the cerebellum and other parts of the CNS. Here we report the identification and establishment from a C57BL/6J mouse colony of a novel mouse line developing spontaneous progressive ataxia, which we refer to as ts3. Frequency of the phenotypic expression was consistent with an autosomal recessive Mendelian trait of inheritance, suggesting that a single gene mutation is responsible for the ataxic phenotype of this line. The onset of ataxia was observed at about three weeks of age, which slowly progressed until the hind limbs became entirely paralyzed in many cases. Micro-MRI study revealed significant cerebellar atrophy in all the ataxic mice, although individual variations were observed. Detailed histological analyses demonstrated significant atrophy of the anterior folia with reduced granule cells (GC) and abnormal morphology of cerebellar Purkinje cells (PC). Study by ultra-high voltage electron microscopy (UHVEM) further indicated aberrant morphology of PC dendrites and their spines, suggesting both morphological and functional abnormalities of the PC in the mutants. Immunohistochemical studies also revealed defects in parallel fiber (PF)–PC synapse formation and abnormal distal extension of climbing fibers (CF). Based on the phenotypic similarities of the ts3 mutant with other known ataxic mutants, we performed immunohistological analyses and found that expression levels of two genes and their products, glutamate receptor delta2 (grid2) and its ligand, cerebellin1 (Cbln1), are significantly reduced or undetectable. Finally, we sequenced the candidate genes and detected a large deletion in the coding region of the grid2 gene. Our present study suggests that ts3 is a new allele of the grid2 gene, which causes similar but different phenotypes as compared to other grid2 mutants. PMID

  5. New (but old) molecules regulating synapse integrity and plasticity: Cbln1 and the delta2 glutamate receptor.

    PubMed

    Yuzaki, M

    2009-09-01

    The delta2 glutamate receptor (GluRdelta2) is predominantly expressed in cerebellar Purkinje cells and plays crucial roles in cerebellar functions: GluRdelta2-null mice display ataxia and impaired motor learning. Interestingly, the contact state of synapses between parallel fibers (PFs) and Purkinje cells is specifically and severely affected, and the number of normal PF synapses is markedly reduced in GluRdelta2-null Purkinje cells. Furthermore, long-term depression at PF-Purkinje cell synapses is abrogated. Cbln1, a member of the C1q/tumor necrosis factor (TNF) superfamily, is predominantly expressed and released from cerebellar granule cells. Unexpectedly, the behavioral, physiological and anatomical phenotypes of cbln1-null mice precisely mimic those of GluRdelta2-null mice. Thus, we propose that Cbln1, which is released from granule cells, and GluRdelta2, which is predominantly expressed in Purkinje cells, are involved in a common signaling pathway crucial for synapse formation/maintenance and plasticity in the cerebellum. Since molecules related to Cbln1 are expressed in various brain regions other than the cerebellum, other C1q/TNF superfamily proteins may also regulate various aspects of synapses in the CNS. Therefore, an understanding of the signaling mechanisms underlying Cbln1 and GluRdelta2 in the cerebellum will provide new insights into the roles of C1q/TNF superfamily proteins as new cytokines that regulate normal and abnormal brain functions.

  6. Metabotropic Glutamate Receptors

    PubMed Central

    Dillon, James; Franks, Christopher J.; Murray, Caitriona; Edwards, Richard J.; Calahorro, Fernando; Ishihara, Takeshi; Katsura, Isao; Holden-Dye, Lindy; O'Connor, Vincent

    2015-01-01

    Glutamatergic neurotransmission is evolutionarily conserved across animal phyla. A major class of glutamate receptors consists of the metabotropic glutamate receptors (mGluRs). In C. elegans, three mGluR genes, mgl-1, mgl-2, and mgl-3, are organized into three subgroups, similar to their mammalian counterparts. Cellular reporters identified expression of the mgls in the nervous system of C. elegans and overlapping expression in the pharyngeal microcircuit that controls pharyngeal muscle activity and feeding behavior. The overlapping expression of mgls within this circuit allowed the investigation of receptor signaling per se and in the context of receptor interactions within a neural network that regulates feeding. We utilized the pharmacological manipulation of neuronally regulated pumping of the pharyngeal muscle in the wild-type and mutants to investigate MGL function. This defined a net mgl-1-dependent inhibition of pharyngeal pumping that is modulated by mgl-3 excitation. Optogenetic activation of the pharyngeal glutamatergic inputs combined with electrophysiological recordings from the isolated pharyngeal preparations provided further evidence for a presynaptic mgl-1-dependent regulation of pharyngeal activity. Analysis of mgl-1, mgl-2, and mgl-3 mutant feeding behavior in the intact organism after acute food removal identified a significant role for mgl-1 in the regulation of an adaptive feeding response. Our data describe the molecular and cellular organization of mgl-1, mgl-2, and mgl-3. Pharmacological analysis identified that, in these paradigms, mgl-1 and mgl-3, but not mgl-2, can modulate the pharyngeal microcircuit. Behavioral analysis identified mgl-1 as a significant determinant of the glutamate-dependent modulation of feeding, further highlighting the significance of mGluRs in complex C. elegans behavior. PMID:25869139

  7. Glutamate receptors at atomic resolution

    SciTech Connect

    Mayer, Mark L.

    2010-12-03

    At synapses throughout the brain and spinal cord, the amino-acid glutamate is the major excitatory neurotransmitter. During evolution, a family of glutamate-receptor ion channels seems to have been assembled from a kit consisting of discrete ligand-binding, ion-channel, modulatory and cytoplasmic domains. Crystallographic studies that exploit this unique architecture have greatly aided structural analysis of the ligand-binding core, but the results also pose a formidable challenge, namely that of resolving the allosteric mechanisms by which individual domains communicate and function in an intact receptor.

  8. Modes of glutamate receptor gating

    PubMed Central

    Popescu, Gabriela K

    2012-01-01

    Abstract The time course of excitatory synaptic currents, the major means of fast communication between neurons of the central nervous system, is encoded in the dynamic behaviour of post-synaptic glutamate-activated channels. First-pass attempts to explain the glutamate-elicited currents with mathematical models produced reaction mechanisms that included only the most basic functionally defined states: resting vs. liganded, closed vs. open, responsive vs. desensitized. In contrast, single-molecule observations afforded by the patch-clamp technique revealed an unanticipated kinetic multiplicity of transitions: from microseconds-lasting flickers to minutes-long modes. How these kinetically defined events impact the shape of the synaptic response, how they relate to rearrangements in receptor structure, and whether and how they are physiologically controlled represent currently active research directions. Modal gating, which refers to the slowest, least frequently observed ion-channel transitions, has been demonstrated for representatives of all ion channel families. However, reaction schemes have been largely confined to the short- and medium-range time scales. For glutamate receptors as well, modal gating has only recently come under rigorous scrutiny. This article reviews the evidence for modal gating of glutamate receptors and the still developing hypotheses about the mechanism(s) by which modal shifts occur and the ways in which they may impact the time course of synaptic transmission. PMID:22106181

  9. Metabotropic glutamate receptors in cancer.

    PubMed

    Yu, Lumeng J; Wall, Brian A; Wangari-Talbot, Janet; Chen, Suzie

    2016-02-16

    Metabotropic glutamate receptors (mGluRs) are widely known for their roles in synaptic signaling. However, accumulating evidence suggests roles of mGluRs in human malignancies in addition to synaptic transmission. Somatic cell homeostasis presents intriguing possibilities of mGluRs and glutamate signaling as novel targets for human cancers. More recently, aberrant glutamate signaling has been shown to participate in the transformation and maintenance of various cancer types, including glioma, melanoma skin cancer, breast cancer, and prostate cancer, indicating that genes encoding mGluRs, GRMs, can function as oncogenes. Here, we provide a review on the interactions of mGluRs and their ligand, glutamate, in processes that promote the growth of tumors of neuronal and non-neuronal origins. Further, we discuss the evolution of riluzole, a glutamate release inhibitor approved for amyotrophic lateral sclerosis (ALS), but now fashioned as an mGluR1 inhibitor for melanoma therapy and as a radio-sensitizer for tumors that have metastasized to the brain. With the success of riluzole, it is not far-fetched to believe that other drugs that may act directly or indirectly on other mGluRs can be beneficial for multiple applications.

  10. Ligands for Ionotropic Glutamate Receptors

    PubMed Central

    Swanson, Geoffrey T.; Sakai, Ryuichi

    2010-01-01

    Marine-derived small molecules and peptides have played a central role in elaborating pharmacological specificities and neuronal functions of mammalian ionotropic glutamate receptors (iGluRs), the primary mediators of excitatory synaptic transmission in the central nervous system (CNS). As well, the pathological sequelae elicited by one class of compounds (the kainoids) constitute a widely-used animal model for human mesial temporal lobe epilepsy (mTLE). New and existing molecules could prove useful as lead compounds for the development of therapeutics for neuropathologies that have aberrant glutamatergic signaling as a central component. In this chapter we discuss natural source origins and pharmacological activities of those marine compounds that target ionotropic glutamate receptors. PMID:19184587

  11. Ionotropic Glutamate Receptors & CNS Disorders

    PubMed Central

    Bowie, Derek

    2008-01-01

    Disorders of the central nervous system (CNS) are complex disease states that represent a major challenge for modern medicine. Although etiology is often unknown, it is established that multiple factors such as defects in genetics and/or epigenetics, the environment as well as imbalance in neurotransmitter receptor systems are all at play in determining an individual’s susceptibility to disease. Gene therapy is currently not available and therefore, most conditions are treated with pharmacological agents that modify neurotransmitter receptor signaling. Here, I provide a review of ionotropic glutamate receptors (iGluRs) and the roles they fulfill in numerous CNS disorders. Specifically, I argue that our understanding of iGluRs has reached a critical turning point to permit, for the first time, a comprehensive re-evaluation of their role in the cause of disease. I illustrate this by highlighting how defects in AMPA receptor trafficking are important to Fragile X mental retardation and ectopic expression of kainate (KA) receptor synapses contributes to the pathology of temporal lobe epilepsy. Finally, I discuss how parallel advances in studies of other neurotransmitter systems may allow pharmacologists to work towards a cure for many CNS disorders rather than developing drugs to treat their symptoms. PMID:18537642

  12. Mechanism for the activation of glutamate receptors

    Cancer.gov

    Scientists at the NIH have used a technique called cryo-electron microscopy to determine a molecular mechanism for the activation and desensitization of ionotropic glutamate receptors, a prominent class of neurotransmitter receptors in the brain and spina

  13. Glutamate Receptor Dynamics in Dendritic Microdomains

    PubMed Central

    Newpher, Thomas M.; Ehlers, Michael D.

    2008-01-01

    Among diverse factors regulating excitatory synaptic transmission, the abundance of postsynaptic glutamate receptors figures prominently in molecular memory and learning-related synaptic plasticity. To allow for both long-term maintenance of synaptic transmission and acute changes in synaptic strength, the relative rates of glutamate receptor insertion and removal must be tightly regulated. Interactions with scaffolding proteins control the targeting and signaling properties of glutamate receptors within the postsynaptic membrane. In addition, extrasynaptic receptor populations control the equilibrium of receptor exchange at synapses and activate distinct signaling pathways involved in plasticity. Here, we review recent findings that have shaped our current understanding of receptor mobility between synaptic and extrasynaptic compartments at glutamatergic synapses, focusing on AMPA and NMDA receptors. We also examine the cooperative relationship between intracellular trafficking and surface diffusion of glutamate receptors that underlies the expression of learning-related synaptic plasticity. PMID:18498731

  14. The action of antidepressants on the glutamate system: regulation of glutamate release and glutamate receptors.

    PubMed

    Musazzi, Laura; Treccani, Giulia; Mallei, Alessandra; Popoli, Maurizio

    2013-06-15

    Recent compelling evidence has suggested that the glutamate system is a primary mediator of psychiatric pathology and also a target for rapid-acting antidepressants. Clinical research in mood and anxiety disorders has shown alterations in levels, clearance, and metabolism of glutamate and consistent volumetric changes in brain areas where glutamate neurons predominate. In parallel, preclinical studies with rodent stress and depression models have found dendritic remodeling and synaptic spines reduction in corresponding areas, suggesting these as major factors in psychopathology. Enhancement of glutamate release/transmission, in turn induced by stress/glucocorticoids, seems crucial for structural/functional changes. Understanding mechanisms of maladaptive plasticity may allow identification of new targets for drugs and therapies. Interestingly, traditional monoaminergic-based antidepressants have been repeatedly shown to interfere with glutamate system function, starting with modulation of N-methyl-D-aspartate (NMDA) receptors. Subsequently, it has been shown that antidepressants reduce glutamate release and synaptic transmission; in particular, it was found antidepressants prevent the acute stress-induced enhancement of glutamate release. Additional studies have shown that antidepressants may partly reverse the maladaptive changes in synapses/circuitry in stress and depression models. Finally, a number of studies over the years have shown that these drugs regulate glutamate receptors, reducing the function of NMDA receptors, potentiating the function of α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptors, and, more recently, exerting variable effects on different subtypes of metabotropic glutamate receptors. The development of NMDA receptor antagonists has opened new avenues for glutamatergic, rapid acting, antidepressants, while additional targets in the glutamate synapse await development of new compounds for better, faster antidepressant action.

  15. Effect of ambient extracellular glutamate on Drosophila glutamate receptor trafficking and function.

    PubMed

    Chen, Kaiyun; Augustin, Hrvoje; Featherstone, David E

    2009-01-01

    Measurements suggest that the hemolymph glutamate concentrations in Drosophila are relatively high. This raises the possibility that extracellular glutamate could be an important regulator of glutamatergic transmission in vivo. Using voltage clamp electrophysiology, we found that synaptic currents in D. melanogaster larval neuromuscular junctions are reduced by extracellular glutamate (EC50: approximately 0.4 mM), such that only 10-30% of receptors were functionally available in 1 mM extracellular glutamate. The kinetics of synaptic currents were also slowed in a dose-dependent fashion (EC50: approximately 1 mM), consistent with the idea that extracellular glutamate preferentially removes the fastest-desensitizing receptors from the functional pool. Prolonged exposure (several hours) to extracellular glutamate also triggers loss of glutamate receptor immunoreactivity from neuromuscular junctions. To determine whether this receptor loss requires that glutamate bind directly to the lost receptors, we examined glutamate-dependent loss of receptor immunoreactivity in larvae with glutamate receptor ligand binding mutations. Our results suggest that glutamate-dependent receptor loss requires binding of glutamate directly to the lost receptors. To determine whether lost receptor protein is degraded or merely redistributed, we used immunoblots. Results suggest that glutamate receptor protein is redistributed, but not degraded, after prolonged exposure to high extracellular glutamate.

  16. Metabotropic Glutamate Receptors: Physiology, Pharmacology, and Disease

    PubMed Central

    Niswender, Colleen M.; Conn, P. Jeffrey

    2010-01-01

    The metabotropic glutamate receptors (mGluRs) are family C G-protein-coupled receptors that participate in the modulation of synaptic transmission and neuronal excitability throughout the central nervous system. The mGluRs bind glutamate within a large extracellular domain and transmit signals through the receptor protein to intracellular signaling partners. A great deal of progress has been made in determining the mechanisms by which mGluRs are activated, proteins with which they interact, and orthosteric and allosteric ligands that can modulate receptor activity. The widespread expression of mGluRs makes these receptors particularly attractive drug targets, and recent studies continue to validate the therapeutic utility of mGluR ligands in neurological and psychiatric disorders such as Alzheimer’s disease, Parkinson’s disease, anxiety, depression, and schizophrenia. PMID:20055706

  17. Presynaptic glutamate receptors: physiological functions and mechanisms of action.

    PubMed

    Pinheiro, Paulo S; Mulle, Christophe

    2008-06-01

    Glutamate acts on postsynaptic glutamate receptors to mediate excitatory communication between neurons. The discovery that additional presynaptic glutamate receptors can modulate neurotransmitter release has added complexity to the way we view glutamatergic synaptic transmission. Here we review evidence of a physiological role for presynaptic glutamate receptors in neurotransmitter release. We compare the physiological roles of ionotropic and metabotropic glutamate receptors in short- and long-term regulation of synaptic transmission. Furthermore, we discuss the physiological conditions that are necessary for their activation, the source of the glutamate that activates them, their mechanisms of action and their involvement in higher brain function.

  18. Diagnostic and pathogenic significance of glutamate receptor autoantibodies.

    PubMed

    Pleasure, David

    2008-05-01

    Autoantibodies against glutamate receptors, first reported in Rasmussen encephalitis, have been observed in other focal epilepsies, central nervous system ischemic infarcts, transient ischemic attacks, sporadic olivopontocerebellar atrophy, systemic lupus erythematosus, and paraneoplastic encephalopathies. The detection of glutamate receptor autoantibodies is not useful in the evaluation of Rasmussen encephalitis but may be a biomarker for brain ischemia, and it is helpful in diagnosing certain paraneoplastic encephalopathies. Passive transfer of glutamate receptor autoantibodies from patients with systemic lupus erythematosus or paraneoplastic encephalopathy suggests that glutamate receptor autoantibodies can actively contribute to neurologic dysfunction.

  19. Allosteric Modulation of Metabotropic Glutamate Receptors

    PubMed Central

    Sheffler, Douglas J.; Gregory, Karen J.; Rook, Jerri M.; Conn, P. Jeffrey

    2013-01-01

    The development of receptor subtype-selective ligands by targeting allosteric sites of G protein-coupled receptors (GPCRs) has proven highly successful in recent years. One GPCR family that has greatly benefited from this approach is the metabotropic glutamate receptors (mGlus). These family C GPCRs participate in the neuromodulatory actions of glutamate throughout the CNS, where they play a number of key roles in regulating synaptic transmission and neuronal excitability. A large number of mGlu subtype-selective allosteric modulators have been identified, the majority of which are thought to bind within the transmembrane regions of the receptor. These modulators can either enhance or inhibit mGlu functional responses and, together with mGlu knockout mice, have furthered the establishment of the physiologic roles of many mGlu subtypes. Numerous pharmacological and receptor mutagenesis studies have been aimed at providing a greater mechanistic understanding of the interaction of mGlu allosteric modulators with the receptor, which have revealed evidence for common allosteric binding sites across multiple mGlu subtypes and the presence for multiple allosteric sites within a single mGlu subtype. Recent data have also revealed that mGlu allosteric modulators can display functional selectivity toward particular signal transduction cascades downstream of an individual mGlu subtype. Studies continue to validate the therapeutic utility of mGlu allosteric modulators as a potential therapeutic approach for a number of disorders including anxiety, schizophrenia, Parkinson’s disease, and Fragile X syndrome. PMID:21907906

  20. Group II metabotropic glutamate receptors and schizophrenia.

    PubMed

    Moreno, José L; Sealfon, Stuart C; González-Maeso, Javier

    2009-12-01

    Schizophrenia is one of the most common mental illnesses, with hereditary and environmental factors important for its etiology. All antipsychotics have in common a high affinity for monoaminergic receptors. Whereas hallucinations and delusions usually respond to typical (haloperidol-like) and atypical (clozapine-like) monoaminergic antipsychotics, their efficacy in improving negative symptoms and cognitive deficits remains inadequate. In addition, devastating side effects are a common characteristic of monoaminergic antipsychotics. Recent biochemical, preclinical and clinical findings support group II metabotropic glutamate receptors (mGluR2 and mGluR3) as a new approach to treat schizophrenia. This paper reviews the status of general knowledge of mGluR2 and mGluR3 in the psychopharmacology, genetics and neuropathology of schizophrenia.

  1. Therapeutic promise and principles: metabotropic glutamate receptors.

    PubMed

    Maiese, Kenneth; Chong, Zhao Zhong; Shang, Yan Chen; Hou, Jinling

    2008-01-01

    For a number of disease entities, oxidative stress becomes a significant factor in the etiology and progression of cell dysfunction and injury. Therapeutic strategies that can identify novel signal transduction pathways to ameliorate the toxic effects of oxidative stress may lead to new avenues of treatment for a spectrum of disorders that include diabetes, Alzheimer's disease, Parkinson's disease and immune system dysfunction. In this respect, metabotropic glutamate receptors (mGluRs) may offer exciting prospects for several disorders since these receptors can limit or prevent apoptotic cell injury as well as impact upon cellular development and function. Yet the role of mGluRs is complex in nature and may require specific mGluR modulation for a particular disease entity to maximize clinical efficacy and limit potential disability. Here we discuss the potential clinical translation of mGluRs and highlight the role of novel signal transduction pathways in the metabotropic glutamate system that may be vital for the clinical utility of mGluRs.

  2. Functional reconstitution of Drosophila melanogaster NMJ glutamate receptors

    DOE PAGES

    Han, Tae Hee; Dharkar, Poorva; Mayer, Mark L.; ...

    2015-04-27

    The Drosophila larval neuromuscular junction (NMJ), at which glutamate acts as the excitatory neurotransmitter, is a widely used model for genetic analysis of synapse function and development. Despite decades of study, the inability to reconstitute NMJ glutamate receptor function using heterologous expression systems has complicated the analysis of receptor function, such that it is difficult to resolve the molecular basis for compound phenotypes observed in mutant flies. In this paper, we find that Drosophila Neto functions as an essential component required for the function of NMJ glutamate receptors, permitting analysis of glutamate receptor responses in Xenopus oocytes. Finally, in combinationmore » with a crystallographic analysis of the GluRIIB ligand binding domain, we use this system to characterize the subunit dependence of assembly, channel block, and ligand selectivity for Drosophila NMJ glutamate receptors.« less

  3. Expression of glutamate receptor subunits in human cancers.

    PubMed

    Stepulak, Andrzej; Luksch, Hella; Gebhardt, Christine; Uckermann, Ortrud; Marzahn, Jenny; Sifringer, Marco; Rzeski, Wojciech; Staufner, Christian; Brocke, Katja S; Turski, Lechoslaw; Ikonomidou, Chrysanthy

    2009-10-01

    Emerging evidence suggests a role for glutamate and its receptors in the biology of cancer. This study was designed to systematically analyze the expression of ionotropic and metabotropic glutamate receptor subunits in various human cancer cell lines, compare expression levels to those in human brain tissue and, using electrophysiological techniques, explore whether cancer cells respond to glutamate receptor agonists and antagonists. Expression analysis of glutamate receptor subunits NR1-NR3B, GluR1-GluR7, KA1, KA2 and mGluR1-mGluR8 was performed by means of RT-PCR in human rhabdomyosarcoma/medulloblastoma (TE671), neuroblastoma (SK-NA-S), thyroid carcinoma (FTC 238), lung carcinoma (SK-LU-1), astrocytoma (MOGGCCM), multiple myeloma (RPMI 8226), glioma (U87-MG and U343), lung carcinoma (A549), colon adenocarcinoma (HT 29), T cell leukemia cells (Jurkat E6.1), breast carcinoma (T47D) and colon adenocarcinoma (LS180). Analysis revealed that all glutamate receptor subunits were differentially expressed in the tumor cell lines. For the majority of tumors, expression levels of NR2B, GluR4, GluR6 and KA2 were lower compared to human brain tissue. Confocal imaging revealed that selected glutamate receptor subunit proteins were expressed in tumor cells. By means of patch-clamp analysis, it was shown that A549 and TE671 cells depolarized in response to application of glutamate agonists and that this effect was reversed by glutamate receptor antagonists. This study reveals that glutamate receptor subunits are differentially expressed in human tumor cell lines at the mRNA and the protein level, and that their expression is associated with the formation of functional channels. The potential role of glutamate receptor antagonists in cancer therapy is a feasible goal to be explored in clinical trials.

  4. The glutamate receptor subunit delta1 is highly expressed in hair cells of the auditory and vestibular systems.

    PubMed

    Safieddine, S; Wenthold, R J

    1997-10-01

    In the inner ear, fast excitatory synaptic transmission is mediated by ionotropic glutamate receptors, including AMPA, kainate, and NMDA receptors. The recently identified delta1 and delta2 glutamate receptors share low homology with the other three types, and no clear response or ligand binding has been obtained from cells transfected with delta alone or in combination with other ionotropic receptors. Studies of mice lacking expression of delta2 show that this subunit plays a crucial role in plasticity of cerebellar glutamatergic synapses. In addition, these mice show a deficit in vestibular compensation. These findings and the nature of glutamatergic synapses between vestibulocochlear hair cells and primary afferent dendrites suggest that delta receptors may be functionally important in the inner ear and prompted us to investigate the expression of delta receptors in the cochlea and peripheral vestibular system. Reverse transcription and DNA amplification by PCR combined with immunocytochemistry and in situ hybridization were used. Our results show that the expression of delta1 in the organ of Corti is intense and restricted to the inner hair cells, whereas delta1 is expressed in all spiral ganglion neurons as well as in their satellite glial cells. In the vestibular end organ, delta1 was highly expressed in both hair cell types and also was expressed in the vestibular ganglion neurons. The prominent expression of delta1 in inner hair cells and in type I and type II vestibular hair cells suggests a functional role in hair cell neurotransmission.

  5. Glutamate Receptor Ion Channels: Structure, Regulation, and Function

    PubMed Central

    Wollmuth, Lonnie P.; McBain, Chris J.; Menniti, Frank S.; Vance, Katie M.; Ogden, Kevin K.; Hansen, Kasper B.; Yuan, Hongjie; Myers, Scott J.; Dingledine, Ray

    2010-01-01

    The mammalian ionotropic glutamate receptor family encodes 18 gene products that coassemble to form ligand-gated ion channels containing an agonist recognition site, a transmembrane ion permeation pathway, and gating elements that couple agonist-induced conformational changes to the opening or closing of the permeation pore. Glutamate receptors mediate fast excitatory synaptic transmission in the central nervous system and are localized on neuronal and non-neuronal cells. These receptors regulate a broad spectrum of processes in the brain, spinal cord, retina, and peripheral nervous system. Glutamate receptors are postulated to play important roles in numerous neurological diseases and have attracted intense scrutiny. The description of glutamate receptor structure, including its transmembrane elements, reveals a complex assembly of multiple semiautonomous extracellular domains linked to a pore-forming element with striking resemblance to an inverted potassium channel. In this review we discuss International Union of Basic and Clinical Pharmacology glutamate receptor nomenclature, structure, assembly, accessory subunits, interacting proteins, gene expression and translation, post-translational modifications, agonist and antagonist pharmacology, allosteric modulation, mechanisms of gating and permeation, roles in normal physiological function, as well as the potential therapeutic use of pharmacological agents acting at glutamate receptors. PMID:20716669

  6. Extracellular glutamate diffusion determines the occupancy of glutamate receptors at CA1 synapses in the hippocampus.

    PubMed Central

    Kullmann, D M; Min, M Y; Asztely, F; Rusakov, D A

    1999-01-01

    Following exocytosis at excitatory synapses in the brain, glutamate binds to several subtypes of postsynaptic receptors. The degree of occupancy of AMPA and NMDA receptors at hippocampal synapses is, however, not known. One approach to estimate receptor occupancy is to examine quantal amplitude fluctuations of postsynaptic signals in hippocampal neurons studied in vitro. The results of such experiments suggest that NMDA receptors at CA1 synapses are activated not only by glutamate released from the immediately apposed presynaptic terminals, but also by glutamate spillover from neighbouring terminals. Numerical simulations point to the extracellular diffusion coefficient as a critical parameter that determines the extent of activation of receptors positioned at different distances from the release site. We have shown that raising the viscosity of the extracellular medium can modulate the diffusion coefficient, providing an experimental tool to investigate the role of diffusion in activation of synaptic and extrasynaptic receptors. Whether intersynaptic cross-talk mediated by NMDA receptors occurs in vivo remains to be determined. The theoretical and experimental approaches described here also promise to shed light on the roles of metabotropic and kainate receptors, which often occur in an extrasynaptic distribution, and are therefore positioned to sense glutamate escaping from the synaptic cleft. PMID:10212489

  7. Metabotropic glutamate receptor type 1 autoimmunity

    PubMed Central

    Lopez-Chiriboga, A. Sebastian; Komorowski, Lars; Kümpfel, Tania; Probst, Christian; Hinson, Shannon R.; Pittock, Sean J.

    2016-01-01

    Objective: To describe retrospectively the clinical associations of immunoglobulin G (IgG) targeting metabotropic glutamate receptor 1 (mGluR1-IgG). Methods: Specimens of 9 patients evaluated on a service basis in the Mayo Clinic Neuroimmunology Laboratory by tissue-based immunofluorescence assay (IFA) yielded a robust, synaptic immunostaining pattern consistent with mGluR1-IgG (serum, 9; CSF, 2 available). Transfected HEK293 cell-based assay (CBA) confirmed mGluR1 specificity in all 11 specimens. A further 2 patients were detected in Germany primarily by CBA. Results: The median symptom onset age for the 11 patients was 58 years (range 33–81 years); 6 were male. All 9 Mayo Clinic patients had subacute onset of cerebellar ataxia, 4 had dysgeusia, 1 had psychiatric symptoms, and 1 had cognitive impairment. All were evaluated for malignancy, but only 1 was affected (cutaneous T-cell lymphoma). One developed ataxia post–herpes zoster infection. Head MRIs were generally atrophic or normal-appearing, and CSF was inflammatory in just 1 of 5 tested, though mGluR1-IgG was detected in both specimens submitted. Five patients improved (attributable to immunotherapy in 4, spontaneously in 1), 3 stabilized (attributable to immunotherapy in 2, cancer therapy in 1), and 1 progressively declined (untreated). The 2 German patients had ataxia, but fulfilled multiple sclerosis diagnostic criteria (1 relapsing-remitting, 1 progressive). However, both had histories of hematologic malignancy (acute lymphocytic leukemia and mantle cell lymphoma), and had mGluR1-IgG detected in serum by CBA (weakly positive on tissue-based IFA). Conclusions: mGluR1 autoimmunity represents a treatable form of cerebellar ataxia. Dysgeusia may be a diagnostic clue. Paraneoplastic, parainfectious, or idiopathic causes may occur. PMID:26888994

  8. [Metabotropic glutamate receptors as targets for new drug development].

    PubMed

    Arkhipov, V I; Kapralova, M V

    2011-01-01

    The review is devoted to experimental investigations of metabotropic glutamate receptors and the properties of drugs (ligands) belonging to agonists, antagonists, and modulators of the activity of these receptors. Possibilities of the treatment of neurodegenerative disorders, cognitive disturbances in schizophrenia patients, and narcotic dependency by using drugs of this class are considered.

  9. Therapeutic Modulation of Glutamate Receptors in Major Depressive Disorder.

    PubMed

    Jaso, Brittany A; Niciu, Mark J; Iadarola, Nicolas D; Lally, Niall; Richards, Erica M; Park, Minkyung; Ballard, Elizabeth D; Nugent, Allison C; Machado-Vieira, Rodrigo; Zarate, Carlos A

    2017-01-01

    Current pharmacotherapies for major depressive disorder (MDD) have a distinct lag of onset that can prolong distress and impairment for patients, and realworld effectiveness trials further suggest that antidepressant efficacy is limited in many patients. All currently approved antidepressant medications for MDD act primarily through monoaminergic mechanisms, e.g., receptor/reuptake agonists or antagonists with varying affinities for serotonin, norepinephrine, or dopamine. Glutamate is the major excitatory neurotransmitter in the central nervous system, and glutamate and its cognate receptors are implicated in the pathophysiology of MDD, as well as in the development of novel therapeutics for this disorder. Since the rapid and robust antidepressant effects of the N-methyl-D-aspartate (NMDA) antagonist ketamine were first observed in 2000, other NMDA receptor antagonists have been studied in MDD. These have been associated with relatively modest antidepressant effects compared to ketamine, but some have shown more favorable characteristics with increased potential in clinical practice (for instance, oral administration, decreased dissociative and/or psychotomimetic effects, and reduced abuse/diversion liability). This article reviews the clinical evidence supporting the use of glutamate receptor modulators with direct affinity for cognate receptors: 1) non-competitive NMDA receptor antagonists (ketamine, memantine, dextromethorphan, AZD6765); 2) subunit (NR2B)-specific NMDA receptor antagonists (CP- 101,606/traxoprodil, MK-0657); 3) NMDA receptor glycine-site partial agonists (D-cycloserine, GLYX- 13); and 4) metabotropic glutamate receptor (mGluR) modulators (AZD2066, RO4917523/basimglurant). Several other theoretical glutamate receptor targets with preclinical antidepressant-like efficacy, but that have yet to be studied clinically, are also briefly discussed; these include α-amino-3-hydroxyl-5-methyl-4- isoxazoleproprionic acid (AMPA) agonists, mGluR2/3 negative

  10. Metabotropic glutamate receptors: From the workbench to the bedside

    PubMed Central

    Nicoletti, F.; Bockaert, J.; Collingridge, G.L.; Conn, P.J.; Ferraguti, F.; Schoepp, D.D.; Wroblewski, J.T.; Pin, J.P.

    2013-01-01

    Metabotropic glutamate (mGlu) receptors were discovered in the mid 1980s and originally described as glutamate receptors coupled to polyphosphoinositide hydrolysis. Almost 6500 articles have been published since then, and subtype-selective mGlu receptor ligands are now under clinical development for the treatment of a variety of disorders such as Fragile-X syndrome, schizophrenia, Parkinson’s disease and L-DOPA-induced dyskinesias, generalized anxiety disorder, chronic pain, and gastroesophageal reflux disorder. Prof. Erminio Costa was linked to the early times of the mGlu receptor history, when a few research groups challenged the general belief that glutamate could only activate ionotropic receptors and all metabolic responses to glutamate were secondary to calcium entry. This review moves from those nostalgic times to the most recent advances in the physiology and pharmacology of mGlu receptors, and highlights the role of individual mGlu receptor subtypes in the pathophysiology of human disorders. This article is part of a Special Issue entitled ‘Trends in Neuropharmacology: In Memory of Erminio Costa’. PMID:21036182

  11. Metabotropic glutamate receptor ligands as potential therapeutics for addiction

    PubMed Central

    Olive, M. F.

    2009-01-01

    There is now compelling evidence that the excitatory amino acid neurotransmitter glutamate plays a pivotal role in drug addiction and alcoholism. As a result, there has been increasing interest in developing glutamate-based therapies for the treatment of addictive disorders. Receptors for glutamate are primarily divided into two classes: ionotropic glutamate receptors (iGluRs) that mediate fast excitatory glutamate transmission, and metabotropic glutamate receptors (mGluRs), which are G-protein coupled receptors that mediate slower, modulatory glutamate transmission. Most iGluR antagonists, while showing some efficacy in animal models of addiction, exhibit serious side effects when tested in humans. mGluR ligands, on the other hand, which have been advanced to testing in clinical trials for various medical conditions, have demonstrated the ability to reduce drug reward, reinforcement, and relapse-like behaviors in animal studies. mGluR ligands that have been shown to be primarily effective are Group I (mGluR1 and mGluR5) negative allosteric modulators and Group II (mGluR2 and mGluR3) orthosteric presynaptic autoreceptor agonists. In this review, we will summarize findings from animal studies suggesting that these mGluR ligands may be of potential benefit in reducing on-going drug self-administration and may aid in the prevention of relapse. The neuroanatomical distribution of mGluR1, mGluR2/3, and mGluR5 receptors and the pharmacological properties of Group I negative allosteric modulators and Group II agonists will also be overviewed. Finally, we will discuss the current status of mGluR ligands in human clinical trials. PMID:19630739

  12. Dynamic DNA methylation controls glutamate receptor trafficking and synaptic scaling.

    PubMed

    Sweatt, J David

    2016-05-01

    Hebbian plasticity, including long-term potentiation and long-term depression, has long been regarded as important for local circuit refinement in the context of memory formation and stabilization. However, circuit development and stabilization additionally relies on non-Hebbian, homeostatic, forms of plasticity such as synaptic scaling. Synaptic scaling is induced by chronic increases or decreases in neuronal activity. Synaptic scaling is associated with cell-wide adjustments in postsynaptic receptor density, and can occur in a multiplicative manner resulting in preservation of relative synaptic strengths across the entire neuron's population of synapses. Both active DNA methylation and demethylation have been validated as crucial regulators of gene transcription during learning, and synaptic scaling is known to be transcriptionally dependent. However, it has been unclear whether homeostatic forms of plasticity such as synaptic scaling are regulated via epigenetic mechanisms. This review describes exciting recent work that has demonstrated a role for active changes in neuronal DNA methylation and demethylation as a controller of synaptic scaling and glutamate receptor trafficking. These findings bring together three major categories of memory-associated mechanisms that were previously largely considered separately: DNA methylation, homeostatic plasticity, and glutamate receptor trafficking. This review describes exciting recent work that has demonstrated a role for active changes in neuronal DNA methylation and demethylation as a controller of synaptic scaling and glutamate receptor trafficking. These findings bring together three major categories of memory-associated mechanisms that were previously considered separately: glutamate receptor trafficking, DNA methylation, and homeostatic plasticity.

  13. Spatiotemporal patterning of glutamate receptors in developing ferret striate cortex.

    PubMed

    Smith, A L; Thompson, I D

    1999-03-01

    We have studied glutamate receptor levels during very early phases of cortical formation by using quantitative in vitro autoradiography to map the expression of NMDA, AMPA and kainate receptors in the developing primary visual cortex of the ferret. NMDA and non-NMDA receptors exhibit very different developmental profiles in primary visual cortex. NMDA receptor density is low at birth and increases throughout the first 2 postnatal months, rising between threefold (layers II/III) and ninefold (layer VI). In contrast, AMPA receptors are abundant at birth and their density remains constant for the first postnatal month, before rising by a maximum of 1.7-fold (layer I) at around the time of eye-opening (postnatal day 32). Kainate receptors are also present in high levels at birth and their expression levels rise in the early postnatal period by between 1. 5-fold (layer I) and threefold (layers V/VI) to a peak just after eye-opening. The proportion of the total ionotropic glutamate receptor binding contributed by NMDA receptors thus rises from 5% at birth to a maximum of 22% at 2 months of age, while the AMPA receptor contribution falls from 87% to 72% over the same period. Below cortex, all three glutamate receptor subtypes are expressed in the subplate region for the first 3 postnatal weeks. These developmental patterns, combined with the fact that AMPA receptors are densely expressed in the proliferative zones underlying presumptive area 17, indicate that non-NMDA receptor expression levels in primary visual cortex are mostly specified much earlier than those of NMDA receptors.

  14. Modafinil attenuates reinstatement of cocaine seeking: role for cystine-glutamate exchange and metabotropic glutamate receptors.

    PubMed

    Mahler, Stephen V; Hensley-Simon, Megan; Tahsili-Fahadan, Pouya; LaLumiere, Ryan T; Thomas, Charles; Fallon, Rebecca V; Kalivas, Peter W; Aston-Jones, Gary

    2014-01-01

    Modafinil may be useful for treating stimulant abuse, but the mechanisms by which it acts to do so are unknown. Indeed, a primary effect of modafinil is to inhibit dopamine transport, which typically promotes rather than inhibits motivated behavior. Therefore, we examined the role of nucleus accumbens extracellular glutamate and the group II metabotropic glutamate receptor (mGluR2/3) in modafinil effects. One group of rats was trained to self-administer cocaine for 10 days and extinguished, then given priming injections of cocaine to elicit reinstatement. Modafinil (300 mg/kg, intraperitoneal) inhibited reinstated cocaine seeking (but did not alter extinction responding by itself), and this effect was prevented by pre-treatment with bilateral microinjections of the mGluR2/3 antagonist LY-341495 (LY) into nucleus accumbens core. No reversal of modafinil effects was seen after unilateral accumbens core LY, or bilateral LY in the rostral pole of accumbens. Next, we sought to explore effects of modafinil on extracellular glutamate levels in accumbens after chronic cocaine. Separate rats were administered non-contingent cocaine, and after 3 weeks of withdrawal underwent accumbens microdialysis. Modafinil increased extracellular accumbens glutamate in chronic cocaine, but not chronic saline-pre-treated animals. This increase was prevented by reverse dialysis of cystine-glutamate exchange or voltage-dependent calcium channel antagonists. Voltage-dependent sodium channel blockade partly attenuated the increase in glutamate, but mGluR1 blockade did not. We conclude that modafinil increases extracellular glutamate in nucleus accumbens from glial and neuronal sources in cocaine-exposed rats, which may be important for its mGluR2/3-mediated antirelapse properties.

  15. Glutamate receptor functions in sensory relay in the thalamus.

    PubMed Central

    Salt, T E

    2002-01-01

    It is known that glutamate is a major excitatory transmitter of sensory and cortical afferents to the thalamus. These actions are mediated via several distinct receptors with postsynaptic excitatory effects predominantly mediated by ionotropic receptors of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) and N-methyl-D-aspartate varieties (NMDA). However, there are also other kinds of glutamate receptor present in the thalamus, notably the metabotropic and kainate types, and these may have more complex or subtle roles in sensory transmission. This paper describes recent electrophysiological experiments done in vitro and in vivo which aim to determine how the metabotropic and kainate receptor types can influence transmission through the sensory thalamic relay. A particular focus will be how such mechanisms might operate under physiological conditions. PMID:12626010

  16. Molecular Characteristics of Membrane Glutamate Receptor-Ionophore Interaction.

    DTIC Science & Technology

    1986-08-29

    Neurochemical - Research , 1984, 9, 29-44. Chang, H.H., Michaelis, E.K. & Roy, S. Functional characteristics of . -Z L-glutamate, N-methyl-D-aspartate and kainate...receptors in isolated brain synaptic membranes. Neurochemical Research , 1984, 9, 901-913. Michaelis, E. K., Galton, N. and Early, S. L. Spider venous

  17. Metabotropic Glutamate Receptors and Interacting Proteins in Epileptogenesis

    PubMed Central

    Qian, Feng; Tang, Feng-Ru

    2016-01-01

    Neurotransmitter and receptor systems are involved in different neurological and neuropsychological disorders such as Parkinson's disease, depression, Alzheimer’s disease and epilepsy. Recent advances in studies of signal transduction pathways or interacting proteins of neurotransmitter receptor systems suggest that different receptor systems may share the common signal transduction pathways or interacting proteins which may be better therapeutic targets for development of drugs to effectively control brain diseases. In this paper, we reviewed metabotropic glutamate receptors (mGluRs) and their related signal transduction pathways or interacting proteins in status epilepticus and temporal lobe epilepsy, and proposed some novel therapeutical drug targets for controlling epilepsy and epileptogenesis. PMID:27030135

  18. Costimulation of AMPA and metabotropic glutamate receptors underlies phospholipase C activation by glutamate in hippocampus.

    PubMed

    Kim, Hye-Hyun; Lee, Kyu-Hee; Lee, Doyun; Han, Young-Eun; Lee, Suk-Ho; Sohn, Jong-Woo; Ho, Won-Kyung

    2015-04-22

    Glutamate, a major neurotransmitter in the brain, activates ionotropic and metabotropic glutamate receptors (iGluRs and mGluRs, respectively). The two types of glutamate receptors interact with each other, as exemplified by the modulation of iGluRs by mGluRs. However, the other way of interaction (i.e., modulation of mGluRs by iGluRs) has not received much attention. In this study, we found that group I mGluR-specific agonist (RS)-3,5-dihydroxyphenylglycine (DHPG) alone is not sufficient to activate phospholipase C (PLC) in rat hippocampus, while glutamate robustly activates PLC. These results suggested that additional mechanisms provided by iGluRs are involved in group I mGluR-mediated PLC activation. A series of experiments demonstrated that glutamate-induced PLC activation is mediated by mGluR5 and is facilitated by local Ca(2+) signals that are induced by AMPA-mediated depolarization and L-type Ca(2+) channel activation. Finally, we found that PLC and L-type Ca(2+) channels are involved in hippocampal mGluR-dependent long-term depression (mGluR-LTD) induced by paired-pulse low-frequency stimulation, but not in DHPG-induced chemical LTD. Together, we propose that AMPA receptors initiate Ca(2+) influx via the L-type Ca(2+) channels that facilitate mGluR5-PLC signaling cascades, which underlie mGluR-LTD in rat hippocampus.

  19. The Delta 2 launcher

    NASA Astrophysics Data System (ADS)

    Ousley, Gilbert W., Sr.

    1991-12-01

    The utilization of the Delta 2 as the vehicle for launching Aristoteles into its near Sun synchronous orbit is addressed. Delta is NASA's most reliable launch vehicle and is well suited for placing the present Aristoteles spacecraft into a 400 m circular orbit. A summary of some of the Delta 2 flight parameters is presented. Diagrams of a typical Delta 2 two stage separation are included along with statistics on delta reliability and launch plans.

  20. Red nucleus glutamate facilitates neuropathic allodynia induced by spared nerve injury through non-NMDA and metabotropic glutamate receptors.

    PubMed

    Yu, Jing; Ding, Cui-Ping; Wang, Jing; Wang, Ting; Zhang, Tao; Zeng, Xiao-Yan; Wang, Jun-Yang

    2015-12-01

    Previous studies have demonstrated that glutamate plays an important role in the development of pathological pain. This study investigates the expression changes of glutamate and the roles of different types of glutamate receptors in the red nucleus (RN) in the development of neuropathic allodynia induced by spared nerve injury (SNI). Immunohistochemistry indicated that glutamate was constitutively expressed in the RN of normal rats. After SNI, the expression levels of glutamate were significantly increased in the RN at 1 week and reached the highest level at 2 weeks postinjury compared with sham-operated and normal rats. The RN glutamate was colocalized with neurons, oligodendrocytes, and astrocytes but not microglia under physiological and neuropathic pain conditions. To elucidate further the roles of the RN glutamate and different types of glutamate receptors in the development of neuropathic allodynia, antagonists to N-methyl-D-aspartate (NMDA), non-NMDA, or metabotropic glutamate receptors (mGluRs) were microinjected into the RN contralateral to the nerve-injury side of rats with SNI, and the paw withdrawal threshold (PWT) was dynamically assessed with von Frey filaments. Microinjection of the NMDA receptor antagonist MK-801 into the RN did not show any effect on SNI-induced mechanical allodynia. However, microinjection of the non-NMDA receptor antagonist 6,7-dinitroquinoxaline-2,3(1H,4H)-dione or the mGluR antagonist (±)-α-methyl-(4-carboxyphenyl) glycine into the RN significantly increased the PWT and alleviated SNI-induced mechanical allodynia. These findings suggest that RN glutamate is involved in regulating neuropathic pain and facilitates the development of SNI-induced neuropathic allodynia. The algesic effect of glutamate is transmitted by the non-NMDA glutamate receptor and mGluRs.

  1. Genetic analysis of neuronal ionotropic glutamate receptor subunits.

    PubMed

    Granger, Adam J; Gray, John A; Lu, Wei; Nicoll, Roger A

    2011-09-01

    In the brain, fast, excitatory synaptic transmission occurs primarily through AMPA- and NMDA-type ionotropic glutamate receptors. These receptors are composed of subunit proteins that determine their biophysical properties and trafficking behaviour. Therefore, determining the function of these subunits and receptor subunit composition is essential for understanding the physiological properties of synaptic transmission. Here, we discuss and evaluate various genetic approaches that have been used to study AMPA and NMDA receptor subunits. These approaches have demonstrated that the GluA1 AMPA receptor subunit is required for activity-dependent trafficking and contributes to basal synaptic transmission, while the GluA2 subunit regulates Ca(2+) permeability, homeostasis and trafficking to the synapse under basal conditions. In contrast, the GluN2A and GluN2B NMDA receptor subunits regulate synaptic AMPA receptor content, both during synaptic development and plasticity. Ongoing research in this field is focusing on the molecular interactions and mechanisms that control these functions. To accomplish this, molecular replacement techniques are being used, where native subunits are replaced with receptors containing targeted mutations. In this review, we discuss a single-cell molecular replacement approach which should arguably advance our physiological understanding of ionotropic glutamate receptor subunits, but is generally applicable to study of any neuronal protein.

  2. Nicotine recruits glutamate receptors to postsynaptic sites.

    PubMed

    Duan, Jing-Jing; Lozada, Adrian F; Gou, Chen-Yu; Xu, Jing; Chen, Yuan; Berg, Darwin K

    2015-09-01

    Cholinergic neurons project throughout the nervous system and activate nicotinic receptors to modulate synaptic function in ways that shape higher order brain function. The acute effects of nicotinic signaling on long-term synaptic plasticity have been well-characterized. Less well understood is how chronic exposure to low levels of nicotine, such as those encountered by habitual smokers, can alter neural connections to promote addiction and other lasting behavioral effects. We show here that chronic exposure of hippocampal neurons in culture to low levels of nicotine recruits AMPA and NMDA receptors to the cell surface and sequesters them at postsynaptic sites. The receptors include GluA2-containing AMPA receptors, which are responsible for most of the excitatory postsynaptic current mediated by AMPA receptors on the neurons, and include NMDA receptors containing GluN1 and GluN2B subunits. Moreover, we find that the nicotine treatment also increases expression of the presynaptic component synapsin 1 and arranges it in puncta juxtaposed to the additional AMPA and NMDA receptor puncta, suggestive of increases in synaptic contacts. Consistent with increased synaptic input, we find that the nicotine treatment leads to an increase in the excitatory postsynaptic currents mediated by AMPA and NMDA receptors. Further, the increases skew the ratio of excitatory-to-inhibitory input that the cell receives, and this holds both for pyramidal neurons and inhibitory neurons in the hippocampal CA1 region. The GluN2B-containing NMDA receptor redistribution at synapses is associated with a significant increase in GluN2B phosphorylation at Tyr1472, a site known to prevent GluN2B endocytosis. These results suggest that chronic exposure to low levels of nicotine not only alters functional connections but also is likely to change excitability levels across networks. Further, it may increase the propensity for synaptic plasticity, given the increase in synaptic NMDA receptors.

  3. Nicotine Recruits Glutamate Receptors to Postsynaptic Sites

    PubMed Central

    Duan, Jing-jing; Lozada, Adrian F.; Gou, Chen-yu; Xu, Jing; Chen, Yuan; Berg, Darwin K.

    2015-01-01

    Cholinergic neurons project throughout the nervous system and activate nicotinic receptors to modulate synaptic function in ways that shape higher order brain function. The acute effects of nicotinic signaling on long-term synaptic plasticity have been well-characterized. Less well understood is how chronic exposure to low levels of nicotine, such as those encountered by habitual smokers, can alter neural connections to promote addiction and other lasting behavioral effects. We show here that chronic exposure of hippocampal neurons in culture to low levels of nicotine recruits AMPA and NMDA receptors to the cell surface and sequesters them at postsynaptic sites. The receptors include GluA2-containing AMPA receptors, which are responsible for most of the excitatory postsynaptic current mediated by AMPA receptors on the neurons, and include NMDA receptors containing GluN1 and GluN2B subunits. Moreover, we find that the nicotine treatment also increases expression of the presynaptic component synapsin 1 and arranges it in puncta juxtaposed to the additional AMPA and NMDA receptor puncta, suggestive of increases in synaptic contacts. Consistent with increased synaptic input, we find that the nicotine treatment leads to an increase in the excitatory postsynaptic currents mediated by AMPA and NMDA receptors. Further, the increases skew the ratio of excitatory-to-inhibitory input the cell receives, and this holds both for pyramidal neurons and inhibitory neurons in the hippocampal CA1 region. The GluN2B-containing NMDA receptor redistribution at synapses is associated with a significant increase in GluN2B phosphorylation at Tyr1472, a site known to prevent GluN2B endocytosis. These results suggest that chronic exposure to low levels of nicotine not only alters functional connections but also is likely to change excitability levels across networks. Further, it may increase the propensity for synaptic plasticity, given the increase in synaptic NMDA receptors. PMID:26365992

  4. The Role of Metabotropic Glutamate Receptor Genes in Schizophrenia

    PubMed Central

    Maj, Carlo; Minelli, Alessandra; Giacopuzzi, Edoardo; Sacchetti, Emilio; Gennarelli, Massimo

    2016-01-01

    Genomic studies revealed two main components in the genetic architecture of schizophrenia, one constituted by common variants determining a distributed polygenic effect and one represented by a large number of heterogeneous rare and highly disruptive mutations. These gene modifications often affect neural transmission and different studies proved an involvement of metabotropic glutamate receptors in schizophrenia phenotype. Through the combination of literature information with genomic data from public repositories, we analyzed the current knowledge on the involvement of genetic variations of the human metabotropic glutamate receptors in schizophrenia and related endophenotypes. Despite the analysis did not reveal a definitive connection, different suggestive associations have been identified and in particular a relevant role has emerged for GRM3 in affecting specific schizophrenia endophenotypes. This supports the hypothesis that these receptors are directly involved in schizophrenia disorder. PMID:27296644

  5. The Role of Metabotropic Glutamate Receptor Genes in Schizophrenia.

    PubMed

    Maj, Carlo; Minelli, Alessandra; Giacopuzzi, Edoardo; Sacchetti, Emilio; Gennarelli, Massimo

    2016-01-01

    Genomic studies revealed two main components in the genetic architecture of schizophrenia, one constituted by common variants determining a distributed polygenic effect and one represented by a large number of heterogeneous rare and highly disruptive mutations. These gene modifications often affect neural transmission and different studies proved an involvement of metabotropic glutamate receptors in schizophrenia phenotype. Through the combination of literature information with genomic data from public repositories, we analyzed the current knowledge on the involvement of genetic variations of the human metabotropic glutamate receptors in schizophrenia and related endophenotypes. Despite the analysis did not reveal a definitive connection, different suggestive associations have been identified and in particular a relevant role has emerged for GRM3 in affecting specific schizophrenia endophenotypes. This supports the hypothesis that these receptors are directly involved in schizophrenia disorder.

  6. Glutamate receptor-mediated toxicity in optic nerve oligodendrocytes

    PubMed Central

    Matute, Carlos; Sánchez-Gómez, M. Victoria; Martínez-Millán, Luis; Miledi, Ricardo

    1997-01-01

    In cultured oligodendrocytes isolated from perinatal rat optic nerves, we have analyzed the expression of ionotropic glutamate receptor subunits as well as the effect of the activation of these receptors on oligodendrocyte viability. Reverse transcription–PCR, in combination with immunocytochemistry, demonstrated that most oligodendrocytes differentiated in vitro express the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunits GluR3 and GluR4 and the kainate receptor subunits GluR6, GluR7, KA1 and KA2. Acute and chronic exposure to kainate caused extensive oligodendrocyte death in culture. This effect was partially prevented by the AMPA receptor antagonist GYKI 52466 and was completely abolished by the non-N-methyl-d-aspartate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), suggesting that both AMPA and kainate receptors mediate the observed kainate toxicity. Furthermore, chronic application of kainate to optic nerves in vivo resulted in massive oligodendrocyte death which, as in vitro, could be prevented by coinfusion of the toxin with CNQX. These findings suggest that excessive activation of the ionotropic glutamate receptors expressed by oligodendrocytes may act as a negative regulator of the size of this cell population. PMID:9238063

  7. Kaitocephalin Antagonism of Glutamate Receptors Expressed in Xenopus Oocytes

    PubMed Central

    2009-01-01

    Kaitocephalin is the first discovered natural toxin with protective properties against excitotoxic death of cultured neurons induced by N-methyl-d-aspartate (NMDA) or α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)/kainic acid (kainate, KA) receptors. Nevertheless, the effects of kaitocephalin on the function of these receptors were unknown. In this work, we report some pharmacological properties of synthetic (−)-kaitocephalin on rat brain glutamate receptors expressed in Xenopus laevis oocytes and on the homomeric AMPA-type GluR3 and KA-type GluR6 receptors. Kaitocephalin was found to be a more potent antagonist of NMDA receptors (IC50 = 75 ± 9 nM) than of AMPA receptors from cerebral cortex (IC50 = 242 ± 37 nM) and from homomeric GluR3 subunits (IC50 = 502 ± 55 nM). Moreover, kaitocephalin is a weak antagonist of the KA-type receptor GluR6 (IC50 ∼ 100 μM) and of metabotropic (IC50 > 100 μM) glutamate receptors expressed by rat brain mRNA. PMID:20436943

  8. Group I Metabotropic Glutamate Receptor Interacting Proteins: Fine-Tuning Receptor Functions in Health and Disease

    PubMed Central

    Kalinowska, Magdalena; Francesconi, Anna

    2016-01-01

    Group I metabotropic glutamate receptors mediate slow excitatory neurotransmission in the central nervous system and are critical to activity-dependent synaptic plasticity, a cellular substrate of learning and memory. Dysregulated receptor signaling is implicated in neuropsychiatric conditions ranging from neurodevelopmental to neurodegenerative disorders. Importantly, group I metabotropic glutamate receptor signaling functions can be modulated by interacting proteins that mediate receptor trafficking, expression and coupling efficiency to signaling effectors. These interactions afford cell- or pathway-specific modulation to fine-tune receptor function, thus representing a potential target for pharmacological interventions in pathological conditions. PMID:27296642

  9. TAAR1 Modulates Cortical Glutamate NMDA Receptor Function.

    PubMed

    Espinoza, Stefano; Lignani, Gabriele; Caffino, Lucia; Maggi, Silvia; Sukhanov, Ilya; Leo, Damiana; Mus, Liudmila; Emanuele, Marco; Ronzitti, Giuseppe; Harmeier, Anja; Medrihan, Lucian; Sotnikova, Tatyana D; Chieregatti, Evelina; Hoener, Marius C; Benfenati, Fabio; Tucci, Valter; Fumagalli, Fabio; Gainetdinov, Raul R

    2015-08-01

    Trace Amine-Associated Receptor 1 (TAAR1) is a G protein-coupled receptor expressed in the mammalian brain and known to influence subcortical monoaminergic transmission. Monoamines, such as dopamine, also play an important role within the prefrontal cortex (PFC) circuitry, which is critically involved in high-o5rder cognitive processes. TAAR1-selective ligands have shown potential antipsychotic, antidepressant, and pro-cognitive effects in experimental animal models; however, it remains unclear whether TAAR1 can affect PFC-related processes and functions. In this study, we document a distinct pattern of expression of TAAR1 in the PFC, as well as altered subunit composition and deficient functionality of the glutamate N-methyl-D-aspartate (NMDA) receptors in the pyramidal neurons of layer V of PFC in mice lacking TAAR1. The dysregulated cortical glutamate transmission in TAAR1-KO mice was associated with aberrant behaviors in several tests, indicating a perseverative and impulsive phenotype of mutants. Conversely, pharmacological activation of TAAR1 with selective agonists reduced premature impulsive responses observed in the fixed-interval conditioning schedule in normal mice. Our study indicates that TAAR1 plays an important role in the modulation of NMDA receptor-mediated glutamate transmission in the PFC and related functions. Furthermore, these data suggest that the development of TAAR1-based drugs could provide a novel therapeutic approach for the treatment of disorders related to aberrant cortical functions.

  10. TAAR1 Modulates Cortical Glutamate NMDA Receptor Function

    PubMed Central

    Espinoza, Stefano; Lignani, Gabriele; Caffino, Lucia; Maggi, Silvia; Sukhanov, Ilya; Leo, Damiana; Mus, Liudmila; Emanuele, Marco; Ronzitti, Giuseppe; Harmeier, Anja; Medrihan, Lucian; Sotnikova, Tatyana D; Chieregatti, Evelina; Hoener, Marius C; Benfenati, Fabio; Tucci, Valter; Fumagalli, Fabio; Gainetdinov, Raul R

    2015-01-01

    Trace Amine-Associated Receptor 1 (TAAR1) is a G protein-coupled receptor expressed in the mammalian brain and known to influence subcortical monoaminergic transmission. Monoamines, such as dopamine, also play an important role within the prefrontal cortex (PFC) circuitry, which is critically involved in high-o5rder cognitive processes. TAAR1-selective ligands have shown potential antipsychotic, antidepressant, and pro-cognitive effects in experimental animal models; however, it remains unclear whether TAAR1 can affect PFC-related processes and functions. In this study, we document a distinct pattern of expression of TAAR1 in the PFC, as well as altered subunit composition and deficient functionality of the glutamate N-methyl-D-aspartate (NMDA) receptors in the pyramidal neurons of layer V of PFC in mice lacking TAAR1. The dysregulated cortical glutamate transmission in TAAR1-KO mice was associated with aberrant behaviors in several tests, indicating a perseverative and impulsive phenotype of mutants. Conversely, pharmacological activation of TAAR1 with selective agonists reduced premature impulsive responses observed in the fixed-interval conditioning schedule in normal mice. Our study indicates that TAAR1 plays an important role in the modulation of NMDA receptor-mediated glutamate transmission in the PFC and related functions. Furthermore, these data suggest that the development of TAAR1-based drugs could provide a novel therapeutic approach for the treatment of disorders related to aberrant cortical functions. PMID:25749299

  11. Structural basis of kainate subtype glutamate receptor desensitization

    PubMed Central

    Meyerson, Joel R.; Chittori, Sagar; Merk, Alan; Rao, Prashant; Han, Tae Hee; Serpe, Mihaela; Mayer, Mark L.; Subramaniam, Sriram

    2016-01-01

    Glutamate receptors are ligand gated tetrameric ion channels that mediate synaptic transmission in the central nervous system. They are instrumental in vertebrate cognition and their dysfunction underlies diverse diseases1,2. In both the resting and desensitized states of AMPA and kainate subtype glutamate receptors the ion channels are closed while the ligand binding domain, which is physically coupled to the channel, adopts dramatically different conformations3–6. Without an atomic model for the desensitized state, it is not possible to address a central question in receptor gating: how the resting and desensitized receptor states both display closed ion channels, even though they have major differences in quaternary structure of the ligand binding domain. By determining the cryo-EM structure of the kainate receptor GluK2 subtype in its desensitized state at 3.8 Å resolution, we show that desensitization is characterized by establishment of a ring-like structure in the ligand binding domain layer of the receptor. Formation of this “desensitization ring” is mediated by staggered helix contacts between adjacent subunits, which leads to a pseudo four-fold symmetric arrangement of the ligand binding domains, illustrating subtle changes in symmetry that are at the heart of the gating mechanism. Disruption of the desensitization ring is likely the key switch that enables restoration of the receptor to its resting state, thereby completing the gating cycle. PMID:27580033

  12. A modern ionotropic glutamate receptor with a K(+) selectivity signature sequence.

    PubMed

    Janovjak, H; Sandoz, G; Isacoff, E Y

    2011-01-01

    Glutamate is the major excitatory neurotransmitter in the mammalian central nervous system and gates non-selective cation channels. The origins of glutamate receptors are not well understood as they differ structurally and functionally from simple bacterial ligand-gated ion channels. Here we report the discovery of an ionotropic glutamate receptor that combines the typical eukaryotic domain architecture with the 'TXVGYG' signature sequence of the selectivity filter found in K(+) channels. This receptor exhibits functional properties intermediate between bacterial and eukaryotic glutamate-gated ion channels, suggesting a link in the evolution of ionotropic glutamate receptors.

  13. Emerging structural insights into the function of ionotropic glutamate receptors

    PubMed Central

    Karakas, Erkan; Regan, Michael C.; Furukawa, Hiro

    2015-01-01

    Summary Ionotropic glutamate receptors (iGluRs) are ligand-gated ion channels that mediate excitatory neurotransmission crucial for brain development and function including learning and memory formation. Recently a wealth of structural studies on iGluRs, including AMPA receptors (AMPARs), kainate receptors, and NMDA receptors (NMDARs) became available.. These studies showed structures of non-NMDARs including AMPAR and kainate receptor in various functional states, thereby providing the first visual sense of how non-NMDAR iGluRs may function in the context of homotetramers. Furthermore, they provided the first view of heterotetrameric NMDAR ion channels, which illuminated the similarities with and differences from non-NMDARs, thus raising a mechanistic distinction between the two groups of iGluRs. Here we review mechanistic insights into iGluR functions gained through structural studies of multiple groups. PMID:25941168

  14. Coantagonism of Glutamate Receptors and Nicotinic Acetylcholinergic Receptors Disrupts Fear Conditioning and Latent Inhibition of Fear Conditioning

    ERIC Educational Resources Information Center

    Gould, Thomas J.; Lewis, Michael C.

    2005-01-01

    The present study investigated the hypothesis that both nicotinic acetylcholinergic receptors (nAChRs) and glutamate receptors ([alpha]-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptors (AMPARs) and N-methyl-D-aspartate glutamate receptors (NMDARs)) are involved in fear conditioning, and may modulate similar processes. The effects of the…

  15. Characterization of an extended glutamate receptor of the ON bipolar neuron in the vertebrate retina

    SciTech Connect

    Slaughter, M.M.; Miller, R.F.

    1985-01-01

    The synaptic receptors of ON bipolar neurons are selectively activated by 2-amino-4-phosphonobutyrate, a glutamate analogue. This agent uniquely distinguishes these receptors from other types of excitatory amino acid receptors found in the retina. Various glutamate and aspartate analogues were used to assess the structure-activity characteristics of this receptor. The results suggest that it represents one class of glutamate receptor which can be distinguished by its preferential activation by acidic amino acid analogues that match the extended conformation of glutamate.

  16. Ionotropic GABA and Glutamate Receptor Mutations and Human Neurologic Diseases

    PubMed Central

    Yuan, Hongjie; Low, Chian-Ming; Moody, Olivia A.; Jenkins, Andrew

    2015-01-01

    The advent of whole exome/genome sequencing and the technology-driven reduction in the cost of next-generation sequencing as well as the introduction of diagnostic-targeted sequencing chips have resulted in an unprecedented volume of data directly linking patient genomic variability to disorders of the brain. This information has the potential to transform our understanding of neurologic disorders by improving diagnoses, illuminating the molecular heterogeneity underlying diseases, and identifying new targets for therapeutic treatment. There is a strong history of mutations in GABA receptor genes being involved in neurologic diseases, particularly the epilepsies. In addition, a substantial number of variants and mutations have been found in GABA receptor genes in patients with autism, schizophrenia, and addiction, suggesting potential links between the GABA receptors and these conditions. A new and unexpected outcome from sequencing efforts has been the surprising number of mutations found in glutamate receptor subunits, with the GRIN2A gene encoding the GluN2A N-methyl-d-aspartate receptor subunit being most often affected. These mutations are associated with multiple neurologic conditions, for which seizure disorders comprise the largest group. The GluN2A subunit appears to be a locus for epilepsy, which holds important therapeutic implications. Virtually all α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor mutations, most of which occur within GRIA3, are from patients with intellectual disabilities, suggesting a link to this condition. Similarly, the most common phenotype for kainate receptor variants is intellectual disability. Herein, we summarize the current understanding of disease-associated mutations in ionotropic GABA and glutamate receptor families, and discuss implications regarding the identification of human mutations and treatment of neurologic diseases. PMID:25904555

  17. MicroRNA-223 is neuroprotective by targeting glutamate receptors

    PubMed Central

    Harraz, Maged M.; Eacker, Stephen M.; Wang, Xueqing; Dawson, Ted M.; Dawson, Valina L.

    2012-01-01

    Stroke is a major cause of mortality and morbidity worldwide. Extracellular glutamate accumulation leading to overstimulation of the ionotropic glutamate receptors mediates neuronal injury in stroke and in neurodegenerative disorders. Here we show that miR-223 controls the response to neuronal injury by regulating the functional expression of the glutamate receptor subunits GluR2 and NR2B in brain. Overexpression of miR-223 lowers the levels of GluR2 and NR2B by targeting 3′-UTR target sites (TSs) in GluR2 and NR2B, inhibits NMDA-induced calcium influx in hippocampal neurons, and protects the brain from neuronal cell death following transient global ischemia and excitotoxic injury. MiR-223 deficiency results in higher levels of NR2B and GluR2, enhanced NMDA-induced calcium influx, and increased miniature excitatory postsynaptic currents in hippocampal neurons. In addition, the absence of MiR-223 leads to contextual, but not cued memory deficits and increased neuronal cell death following transient global ischemia and excitotoxicity. These data identify miR-223 as a major regulator of the expression of GluR2 and NR2B, and suggest a therapeutic role for miR-223 in stroke and other excitotoxic neuronal disorders. PMID:23112146

  18. Tyrosine phosphorylation of glutamate receptors by non-receptor tyrosine kinases: roles in depression-like behavior

    PubMed Central

    Mao, Li-Min; Wang, John Q.

    2016-01-01

    Several key members of the non-receptor tyrosine kinase (nRTK) family are abundantly present within excitatory synapses in the mammalian brain. These neuron-enriched nRTKs interact with glutamate receptors and phosphorylate the receptors at tyrosine sites. The N-methyl-D-aspartate receptor is a direct substrate of nRTKs and has been extensively investigated in its phosphorylation responses to nRTKs. The α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor is the other glutamate receptor subtype that is subject to nRTK-mediated tyrosine phosphorylation. Recently, group I metabotropic glutamate receptors (mGluR1/5) were found to be sensitive to nRTKs. Robust tyrosine phosphorylation may occur in C-terminal tails of mGluR5. Tyrosine phosphorylation of glutamate receptors is either constitutive or induced activity-dependently by changing cellular and/or synaptic input. Through inducing tyrosine phosphorylation, nRTKs regulate trafficking, subcellular distribution, and function of modified receptors. Available data show that nRTK-glutamate receptor interactions and tyrosine phosphorylation of the receptors undergo drastic adaptations in mood disorders such as major depressive disorder. The remodeling of the nRTK-glutamate receptor interplay contributes to the long-lasting pathophysiology and symptomology of depression. This review summarizes the recent progress in tyrosine phosphorylation of glutamate receptors and analyzes the role of nRTKs in regulating glutamate receptors and depression-like behavior. PMID:26942227

  19. Three-dimensional models of non-NMDA glutamate receptors.

    PubMed Central

    Sutcliffe, M J; Wo, Z G; Oswald, R E

    1996-01-01

    Structural models have been produced for three types of non-NMDA inotropic glutamate receptors: an AMPA receptor, GluR1, a kainate receptor, GluR6; and a low-molecular-weight kainate receptor from goldfish, GFKAR alpha. Modeling was restricted to the domains of the proteins that bind the neurotransmitter glutamate and that form the ion channel. Model building combined homology modeling, distance geometry, molecular mechanics, interactive modeling, and known constraints. The models indicate new potential interactions in the extracellular domain between protein and agonists, and suggest that the transition from the "closed" to the "open" state involves the movement of a conserved positive residue away from, and two conserved negative residues into, the extracellular entrance to the pore upon binding. As a first approximation, the ion channel domain was modeled with a structure comprising a central antiparallel beta-barrel that partially crosses the membrane, and against which alpha-helices from each subunit are packed; a third alpha-helix packs against these two helices in each subunit. Much, but not all, of the available data were consistent with this structure. Modifying the beta-barrel to a loop-like topology produced a model consistent with available data. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 7 PMID:8785317

  20. EVALUATING THE NMDA-GLUTAMATE RECEPTOR AS A SITE OF ACTION FOR TOLUENE, IN VIVO

    EPA Science Inventory

    In vitro, toluene disrupts the function of NMDA-glutamate receptors, indicating that effects on NMDA receptor function may contribute to toluene neurotoxicity. NMDA-glutamate receptors are widely present in the visual system and contribute to pattern-elicited visual evoked potent...

  1. [A 16-year-old boy with meningoencephalitis with auto-antibody against glutamate receptor].

    PubMed

    Tomioka, Shiho; Shimono, Masayuki; Kato, Ayako; Takano, Kenichi; Shiota, Naoki; Takahashi, Yukitoshi

    2008-01-01

    We herein report a 16-year-old boy who presented with fever and generalized convulsion. His symptoms progressively worsened, and electroencephalography (EEG) showed status with bi-frontal focus. One month after the initial presentation, examination of the cerebrospinal fluid showed pleocytosis, an increase in the IgG index and a positive oligoclonal IgG band. Brain MRI suggested slightly high signal intensity in the cerebral gray matter on FLAIR images. We considered that the patient had autoimmune meningoencephalitis, and therefore treated him with methyl-predonisolone pulse therapy, which substantially improved both his clinical condition and EEG findings. Before the therapy, the IgM and IgG auto-antibodies against glutamate receptor (GluR) epsilon 2 and delta 2 were positive, however they became negative after the therapy. In conclusion, some cases of meningoencephalitis with auto-antibodies against GluR may show an electrical status, mild brain MRI findings, and a good response to methylprednisolone pulse therapy. These clinical features were quite different from those observed for cases of Rasmussen's encephalitis.

  2. Novel Functional Properties of Drosophila CNS Glutamate Receptors

    SciTech Connect

    Li, Yan; Dharkar, Poorva; Han, Tae-Hee; Serpe, Mihaela; Lee, Chi-Hon; Mayer, Mark L.

    2016-12-01

    Phylogenetic analysis reveals AMPA, kainate, and NMDA receptor families in insect genomes, suggesting conserved functional properties corresponding to their vertebrate counterparts. However, heterologous expression of the Drosophila kainate receptor DKaiR1D and the AMPA receptor DGluR1A revealed novel ligand selectivity at odds with the classification used for vertebrate glutamate receptor ion channels (iGluRs). DKaiR1D forms a rapidly activating and desensitizing receptor that is inhibited by both NMDA and the NMDA receptor antagonist AP5; crystallization of the KaiR1D ligand-binding domain reveals that these ligands stabilize open cleft conformations, explaining their action as antagonists. Surprisingly, the AMPA receptor DGluR1A shows weak activation by its namesake agonist AMPA and also by quisqualate. Crystallization of the DGluR1A ligand-binding domain reveals amino acid exchanges that interfere with binding of these ligands. The unexpected ligand-binding profiles of insect iGluRs allows classical tools to be used in novel approaches for the study of synaptic regulation.

  3. Extrasynaptic glutamate NMDA receptors: key players in striatal function.

    PubMed

    Garcia-Munoz, Marianela; Lopez-Huerta, Violeta G; Carrillo-Reid, Luis; Arbuthnott, Gordon W

    2015-02-01

    N-methyl-D-aspartate receptors (NMDAR) are crucial for the function of excitatory neurotransmission and are present at the synapse and on the extrasynaptic membrane. The major nucleus of the basal ganglia, striatum, receives a large glutamatergic excitatory input carrying information about movements and associated sensory stimulation for its proper function. Such bombardment of glutamate synaptic release results in a large extracellular concentration of glutamate that can overcome the neuronal and glial uptake homeostatic systems therefore allowing the stimulation of extrasynaptic glutamate receptors. Here we have studied the participation of their extrasynaptic type in cortically evoked responses or in the presence of NMDARs stimulation. We report that extrasynaptic NMDAR blocker memantine, reduced in a dose-dependent manner cortically induced NMDA excitatory currents in striatal neurons (recorded in zero-Mg(++) plus DNQX 10 μM). Moreover, memantine (2-4 μM) significantly reduced the NMDAR-dependent membrane potential oscillations called up and down states. Recordings of neuronal striatal networks with a fluorescent calcium indicator or with multielectrode arrays (MEA) also showed that memantine reduced in a dose-dependent manner, NMDA-induced excitatory currents and network behavior. We used multielectrode arrays (MEA) to grow segregated cortical and striatal neurons. Once synaptic contacts were developed (>21DIV) recordings of extracellular activity confirmed the cortical drive of spontaneous synchronous discharges in both compartments. After severing connections between compartments, active striatal neurons in the presence of memantine (1 μM) and CNQX (10 μM) were predominantly fast spiking interneurons (FSI). The significance of extrasynaptic receptors in the regulation of striatal function and neuronal network activity is evident.

  4. Receptor-mediated glutamate release from volume sensitive channels in astrocytes

    NASA Astrophysics Data System (ADS)

    Takano, Takahiro; Kang, Jian; Jaiswal, Jyoti K.; Simon, Sanford M.; Lin, Jane H.-C.; Yu, Yufei; Li, Yuxing; Yang, Jay; Dienel, Gerald; Zielke, H. Ronald; Nedergaard, Maiken

    2005-11-01

    Several lines of work have shown that astrocytes release glutamate in response to receptor activation, which results in a modulation of local synaptic activity. Astrocytic glutamate release is Ca2+-dependent and occurs in conjunction with exocytosis of glutamate containing vesicles. However, astrocytes contain a millimolar concentration of cytosolic glutamate and express channels permeable to small anions, such as glutamate. Here, we tested the idea that astrocytes respond to receptor stimulation by dynamic changes in cell volume, resulting in volume-sensitive channel activation, and efflux of cytosolic glutamate. Confocal imaging and whole-cell recordings demonstrated that astrocytes exhibited a transient Ca2+-dependent cell volume increase, which activated glutamate permeable channels. HPLC analysis revealed that glutamate was released in conjunction with other amino acid osmolytes. Our observations indicate that volume-sensitive channel may constitute a previously uncharacterized target for modulation of astrocyte-neuronal interactions. electrophysiology | exocytosis | neurotransmitters | osmolarity | synapses

  5. Metabotropic Glutamate Receptor 7: From Synaptic Function to Therapeutic Implications

    PubMed Central

    Palazzo, Enza; Marabese, Ida; de Novellis, Vito; Rossi, Francesco; Maione, Sabatino

    2016-01-01

    Metabotropic glutamate receptor 7 (mGluR7) is localized presynaptically at the active zone of neurotransmitter release. Unlike mGluR4 and mGluR8, which share mGluR7’s presynaptic location, mGluR7 shows low affinity for glutamate and is activated only by high glutamate concentrations. Its wide distribution in the central nervous system (CNS) and evolutionary conservation across species suggest that mGluR7 plays a primary role in controlling excitatory synapse function. High mGluR7 expression has been observed in several brain regions that are critical for CNS functioning and are involved in neurological and psychiatric disorder development. Until the recent discovery of selective ligands for mGluR7, techniques to elucidate its role in neural function were limited to the use of knockout mice and gene silencing. Studies using these two techniques have revealed that mGluR7 modulates emotionality, stress and fear responses. N,N'-dibenzhydrylethane-1,2-diamine dihydrochloride (AMN082) was reported as the first selective mGluR7 allosteric agonist. Pharmacological effects of AMN082 have not completely confirmed the mGluR7-knockout mouse phenotype; this has been attributed to rapid receptor internalization after drug treatment and to the drug’s apparent lack of in vivo selectivity. Therefore, the more recently developed mGluR7 negative allosteric modulators (NAMs) are crucial for understanding mGluR7 function and for exploiting its potential as a target for therapeutic interventions. This review presents the main findings regarding mGluR7’s effect on modulation of synaptic function and its role in normal CNS function and in models of neurologic and psychiatric disorders. PMID:27306064

  6. Bridging the synaptic cleft: lessons from orphan glutamate receptors.

    PubMed

    Schmid, Sabine M; Hollmann, Michael

    2010-08-24

    For neurons to communicate, signals must cross the cell-to-cell distance at their points of contact. At the predominant cell-cell contact in the central nervous system, the chemical synapse, the synaptic cleft spans roughly 20 nanometers. To signal across this distance, the presynaptic neuron secretes a diffusible neurotransmitter, which is detected by receptors on the postsynaptic neuron. Although this signaling mechanism has become common knowledge, it remains unclear how synapses are maintained when they are not in immediate use. New evidence reveals how Nature solved this problem at a particular type of synapse in the cerebellum: Three old acquaintances bridge the cleft. The ionotropic glutamate receptor GluD2 constitutes the postsynaptic anchor that indirectly interacts with the presynaptic anchor neurexin through a presynaptically secreted soluble factor, a member of the C1q protein family named Cbln1. This trio collaborates to align pre- and postsynaptic sides.

  7. Glutamate receptors on myelinated spinal cord axons: II)AMPA and GluR5 receptors

    PubMed Central

    Ouardouz, M.; Coderre, E.; Zamponi, G. W.; Hameed, S.; Yin, X.; Trapp, B.D.; Stys, P.K.

    2010-01-01

    Objective Glutamate receptors, which play a major role in the physiology and pathology of CNS gray matter, are also involved in the pathophysiology of white matter. However the cellular and molecular mechanisms responsible for excitotoxic damage to white matter elements are not fully understood. We explored the roles of AMPA and GluR5 kainate receptors in axonal Ca2+ deregulation. Methods Dorsal column axons were loaded with a Ca2+ indicator and imaged in vitro using confocal microscopy. Results Both AMPA and a GluR5 kainate receptor agonists increased intra-axonal Ca2+ in myelinated rat dorsal column fibers. These responses were inhibited by selective antagonists of these glutamate receptors. The GluR5-mediated Ca2+ rise was mediated by both canonical (i.e. ionotropic) and non-canonical (metabotropic) signalling, dependent on a pertussis toxin-sensitive G protein and a phospholipase C-dependent pathway, promoting Ca2+ release from IP3-dependent stores. Additionally, the GluR5 response was significantly reduced by intra-axonal NO scavengers. In contrast, GluR4 AMPA receptors operated via Ca2+ induced Ca2+ release, dependent on ryanodine receptors, and unaffected by NO scavengers. Neither pathway depended on L-type Ca2+ channels, in contrast to GlurR6 kainate receptor action 1. Immunohistochemistry confirmed the presence of GluR4 and GluR5 clustered at the surface of myelinated axons; GluR5 co-immunoprecipitated with nNOS and often co-localized with nNOS clusters on the internodal axon. Interpretation Central myelinated axons express functional AMPA and GluR5 kainate receptors, and can directly respond to glutamate receptor agonists. These glutamate receptor-dependent signalling pathways promote an increase in intra-axonal Ca2+ levels potentially contributing to axonal degeneration. PMID:19224531

  8. Functional reconstitution of Drosophila melanogaster NMJ glutamate receptors

    SciTech Connect

    Han, Tae Hee; Dharkar, Poorva; Mayer, Mark L.; Serpe, Mihaela

    2015-04-27

    The Drosophila larval neuromuscular junction (NMJ), at which glutamate acts as the excitatory neurotransmitter, is a widely used model for genetic analysis of synapse function and development. Despite decades of study, the inability to reconstitute NMJ glutamate receptor function using heterologous expression systems has complicated the analysis of receptor function, such that it is difficult to resolve the molecular basis for compound phenotypes observed in mutant flies. In this paper, we find that Drosophila Neto functions as an essential component required for the function of NMJ glutamate receptors, permitting analysis of glutamate receptor responses in Xenopus oocytes. Finally, in combination with a crystallographic analysis of the GluRIIB ligand binding domain, we use this system to characterize the subunit dependence of assembly, channel block, and ligand selectivity for Drosophila NMJ glutamate receptors.

  9. delta-Opioid receptor agonist SNC80 elicits peripheral antinociception via delta(1) and delta(2) receptors and activation of the l-arginine/nitric oxide/cyclic GMP pathway.

    PubMed

    Pacheco, Daniela F; Reis, Gláucia M L; Francischi, Janetti N; Castro, Maria S A; Perez, Andrea C; Duarte, Igor D G

    2005-11-19

    In this study, we characterized the role of delta(1) and delta(2) opioids receptors, as well the involvement of the l-arginine/NO/cGMP pathway in the peripheral antinociception induced by delta-opioid receptor agonist (+)-4-[(alphaR)-alpha-((2S,5R)-4-Allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide (SNC80). The paw pressure test was utilized, in which pain sensitivity is increased by intraplantar injection of prostaglandin E(2) (2 microg). Administration of SNC80 (20, 40 and 80 microg/paw) decreased the hyperalgesia induced by prostaglandin E(2) in a dose-dependent manner. The possibility that the higher dose of SNC80 (80 microg) has a central or systemic effect was excluded, since administration of the drug into the contralateral paw did not elicit antinociception in the right paw. 7-Benzylidenenaltrexone (BNTX), 5, 10 and 20 microg/paw, and 17-(Cyclopropylmethyl)-6,7-didehydro-3,14beta-dihydroxy-4,5alpha-epoxy-6,7-2',3'-benzo[b]furanomorphinan (naltriben), 2.5, 5 and 10 microg/paw, delta(1) and delta(2) opioid receptor antagonist respectively, elicited partial antagonism of the peripheral antinociceptive effect of the SNC80 (80 microg). The BNTX (10 microg/paw)-naltriben (5 microg/paw) combination completely antagonized the peripheral antinociception induced by SNC80 (80 microg). Further, blockers of the l-arginine/NO/cGMP pathway, N(G)-nitro-l-arginine (12, 18 and 24 microg/paw) and methylene blue (125, 250 and 500 microg/paw) were observed reverting the peripheral antinociceptive effect of SNC80. This study provides evidence that the peripheral antinociception induced by SNC80 occurs via delta(1) and delta(2) receptors and may result from l-arginine/NO/cGMP pathway activation.

  10. Neurosteroid binding to the amino terminal and glutamate binding domains of ionotropic glutamate receptors.

    PubMed

    Cameron, Krasnodara; Bartle, Emily; Roark, Ryan; Fanelli, David; Pham, Melissa; Pollard, Beth; Borkowski, Brian; Rhoads, Sarah; Kim, Joon; Rocha, Monica; Kahlson, Martha; Kangala, Melinda; Gentile, Lisa

    2012-06-01

    The endogenous neurosteroids, pregnenolone sulfate (PS) and 3α-hydroxy-5β-pregnan-20-one sulfate (PREGAS), have been shown to differentially regulate the ionotropic glutamate receptor (iGluR) family of ligand-gated ion channels. Upon binding to these receptors, PREGAS decreases current flow through the channels. Upon binding to non-NMDA or NMDA receptors containing an GluN2C or GluN2D subunit, PS also decreases current flow through the channels, however, upon binding to NMDA receptors containing an GluN2A or GluN2B subunit, flow through the channels increases. To begin to understand this differential regulation, we have cloned the S1S2 and amino terminal domains (ATD) of the NMDA GluN2B and GluN2D and AMPA GluA2 subunits. Here we present results that show that PS and PREGAS bind to different sites in the ATD of the GluA2 subunit, which when combined with previous results from our lab, now identifies two binding domains for each neurosteroid. We also show both neurosteroids bind only to the ATD of the GluN2D subunit, suggesting that this binding is distinct from that of the AMPA GluA2 subunit, with both leading to iGluR inhibition. Finally, we provide evidence that both PS and PREGAS bind to the S1S2 domain of the NMDA GluN2B subunit. Neurosteroid binding to the S1S2 domain of NMDA subunits responsible for potentiation of iGluRs and to the ATD of NMDA subunits responsible for inhibition of iGluRs, provides an interesting option for therapeutic design.

  11. A Transmembrane Accessory Subunit that Modulates Kainate-Type Glutamate Receptors

    PubMed Central

    Zhang, Wei; St-Gelais, Fannie; Grabner, Chad P.; Trinidad, Jonathan C.; Sumioka, Akio; Morimoto-Tomita, Megumi; Kim, Kwang S.; Straub, Christoph; Burlingame, Alma L.; Howe, James R.; Tomita, Susumu

    2009-01-01

    SUMMARY Glutamate receptors play major roles in excitatory transmission in the vertebrate brain. Among ionotropic glutamate receptors (AMPA, kainate, NMDA), AMPA receptors mediate fast synaptic transmission and require TARP auxiliary subunits. NMDA receptors and kainate receptors play roles in synaptic transmission, but it remains uncertain whether these ionotropic glutamate receptors also have essential subunits. Using a proteomic screen, we have identified NETO2, a brain-specific protein of unknown function, as an interactor with kainate-type glutamate receptors. NETO2 modulates the channel properties of recombinant and native kainate receptors without affecting trafficking of the receptors and also modulates kainate-receptor-mediated mEPSCs. Furthermore, we found that kainate receptors regulate the surface expression of NETO2 and that NETO2 protein levels and surface expression are decreased in mice lacking the kainate receptor GluR6. The results show that NETO2 is a kainate receptor subunit with significant effects on glutamate signaling mechanisms in brain. PMID:19217376

  12. Effects of stimulation of glutamate receptors in medial septum on some immune responses in rats.

    PubMed

    Dutta, Goutam; Raj Goswami, Ananda; Ghosh, Tusharkanti

    2013-11-13

    The immunomodulatory role of medial septum (MS) has been explored so far only in MS lesioned rats. But in MS lesioned rats, all the nerve cells and fibres of the lesioned area are damaged and the specific role of the neural circuits of MS on immunomodulation cannot be assessed from the lesion of MS. Considering the presence of a large number of glutamate receptors in MS, the specific role of glutamate receptors stimulation on some immune responses has been investigated in the present study. Hyperreactive behaviour, TC and DC of WBC, phagocytic activity of peripheral leukocytes, adhesibility and cytotoxicity of splenic mononuclear cells (MNC), delayed type of hypersensitivity (DTH) responses and the serum corticosterone (CORT) were measured after microinfusion of glutamate into MS of rats. To ascertain the specific role of those glutamate receptors, the parameters were also measured after microinfusion of glutamate receptor blocker 6, 7-dinitroquinoxaline-2, 3-dione (DNQX). The hyperreactive behaviour, TC and DC of WBC remained unaltered after stimulation or blocking of glutamate receptors. The phagocytic activity, adhesibility and cytotoxicity of splenic MNC, and DTH responses were increased after infusion of 0.25 and 0.5µM glutamate. But after infusion of higher dose of glutamate (1µM), the phagocytic activity and the adhesibility of splenic MNC were decreased and other parameters remained unaltered in that condition. After infusion of 4 and 8mM DNQX all the observed immunological parameters were decreased. The CORT concentration was decreased after infusion of 0.25 and 0.5µM of glutamate but it was increased after infusion of 1µM glutamate or 4 and 8mM DNQX. Results indicate that the medial septal glutamate receptors play an important role in the modulation of some immune responses.

  13. Redefining the classification of AMPA-selective ionotropic glutamate receptors

    PubMed Central

    Bowie, Derek

    2012-01-01

    Abstract AMPA-type ionotropic glutamate receptors (iGluRs) represent the major excitatory neurotransmitter receptor in the developing and adult vertebrate CNS. They are crucial for the normal hardwiring of glutamatergic circuits but also fine tune synaptic strength by cycling into and out of synapses during periods of sustained patterned activity or altered homeostasis. AMPARs are grouped into two functionally distinct tetrameric assemblies based on the inclusion or exclusion of the GluA2 receptor subunit. GluA2-containing receptors are thought to be the most abundant AMPAR in the CNS, typified by their small unitary events, Ca2+ impermeability and insensitivity to polyamine block. In contrast, GluA2-lacking AMPARs exhibit large unitary conductance, marked divalent permeability and nano- to micromolar polyamine affinity. Here, I review evidence for the existence of a third class of AMPAR which, though similarly Ca2+ permeable, is characterized by its near-insensitivity to internal and external channel block by polyamines. This novel class of AMPAR is most notably found at multivesicular release synapses found in the avian auditory brainstem and mammalian retina. Curiously, these synapses lack NMDA-type iGluRs, which are conventionally associated with controlling AMPAR insertion. The lack of NMDARs suggests that a different set of rules may govern AMPAR cycling at these synapses. AMPARs with similar functional profiles are also found on some glial cells suggesting they may have a more widespread distribution in the mammalian CNS. I conclude by noting that modest changes to the ion-permeation pathway might be sufficient to retain divalent permeability whilst eliminating polyamine sensitivity. Consequently, this emerging AMPAR subclass need not be assembled from novel subunits, yet to be cloned, but could simply occur by varying the stoichiometry of existing proteins. PMID:22106175

  14. Emerging models of glutamate receptor ion channel structure and function.

    PubMed

    Mayer, Mark L

    2011-10-12

    Excitatory synaptic transmission in the brain is mediated by ligand-gated ion channels (iGluRs) activated by glutamate. Distinct from other neurotransmitter receptors, the extracellular domains of iGluRs are loosely packed assemblies with two clearly distinct layers, each of which has both local and global 2-fold axes of symmetry. By contrast, the iGluR transmembrane segments have 4-fold symmetry and share a conserved pore loop architecture found in tetrameric voltage-gated ion channels. The striking layered architecture of iGluRs revealed by the 3.6 Å resolution structure of an AMPA receptor homotetramer likely arose from gene fusion events that occurred early in evolution. Although this modular design has greatly facilitated biophysical and structural studies on individual iGluR domains, and suggested conserved mechanisms for iGluR gating, recent work is beginning to reveal unanticipated diversity in the structure, allosteric regulation, and assembly of iGluR subtypes.

  15. Reconsolidation of Reminder-Induced Amnesia: Role of NMDA and AMPA Glutamate Receptors.

    PubMed

    Nikitin, V P; Kozyrev, S A; Solntseva, S V

    2015-11-01

    We studied the role of glutamate receptors and reminder in the mechanisms of amnesia maintenance caused by disruption of conditioned food aversion reconsolidation with an antagonist of NMDA glutamate receptor in snails. At the early stage of amnesia (day 3 after induction), injection or NMDA of AMPA glutamate receptor antagonists prior to reminder (presentation of the conditioned food stimulus) led to memory recovery. Reminder alone or injection of antagonists without reminder or after reminder was ineffective. At the late stage of amnesia (day 10), antagonists/reminder had no effect on amnesia maintenance. It was hypothesized that reminder at the early stage of amnesia led to reactivation and reconsolidation of the molecular processes of amnesia including activation NMDA and AMPA glutamate receptors. Injection of antagonists of these receptors prior to reminder led to disruption of reactivation/reconsolidation of amnesia and recovery of the conditioned food aversion memory.

  16. A slow excitatory postsynaptic current mediated by a novel metabotropic glutamate receptor in CA1 pyramidal neurons.

    PubMed

    Sheng, Nengyin; Yang, Jing; Silm, Katlin; Edwards, Robert H; Nicoll, Roger A

    2017-03-15

    Slow excitatory postsynaptic currents (EPSCs) mediated by metabotropic glutamate receptors (mGlu receptors) have been reported in several neuronal subtypes, but their presence in hippocampal pyramidal neurons remains elusive. Here we find that in CA1 pyramidal neurons a slow EPSC is induced by repetitive stimulation while ionotropic glutamate receptors and glutamate-uptake are blocked whereas it is absent in the VGLUT1 knockout mouse in which presynaptic glutamate is lost, suggesting the slow EPSC is mediated by glutamate activating mGlu receptors. However, it is not inhibited by known mGlu receptor antagonists. These findings suggest that this slow EPSC is mediated by a novel mGlu receptor, and that it may be involved in neurological diseases associated with abnormal high-concentration of extracellular glutamate. This article is part of the Special Issue entitled 'Metabotropic Glutamate Receptors, 5 years on'.

  17. Metabotropic and ionotropic glutamate receptors as potential targets for the treatment of alcohol use disorder.

    PubMed

    Goodwani, Sunil; Saternos, Hannah; Alasmari, Fawaz; Sari, Youssef

    2017-02-24

    Emerging evidence indicates that dysfunctional glutamate neurotransmission is critical in the initiation and development of alcohol and drug dependence. Alcohol consumption induced downregulation of glutamate transporter 1 (GLT-1) as reported in previous studies from our laboratory. Glutamate is the major excitatory neurotransmitter in the brain, which acts via interactions with several glutamate receptors. Alcohol consumption interferes with the glutamatergic signal transmission by altering the functions of these receptors. Among the glutamate receptors involved in alcohol-drinking behavior are the metabotropic receptors such as mGluR1/5, mGluR2/3, and mGluR7, as well as the ionotropic receptors, NMDA and AMPA. Preclinical studies using agonists and antagonists implicate these glutamatergic receptors in the development of alcohol use disorder (AUD). Therefore, the purpose of this review is to discuss the neurocircuitry involving glutamate transmission in animals exposed to alcohol and further outline the role of metabotropic and ionotropic receptors in the regulation of alcohol-drinking behavior. This review provides ample information about the potential therapeutic role of glutamatergic receptors for the treatment of AUD.

  18. Molecular cloning, chromosomal mapping, and functional expression of human brain glutamate receptors

    SciTech Connect

    Sun, W.; Ferrer-Montiel, A.V.; Schinder, A.F.; Montal, M. ); McPherson, J.P. ); Evans, G.A. )

    1992-02-15

    A full-length cDNA clone encoding a glutamate receptor was isolated from a human brain cDNA library, and the gene product was characterized after expression in Xenopus oocytes. Degenerate PCR primers to conserved regions of published rat brain glutamate receptor sequences amplified a 1-kilobase fragment from a human brain cDNA library. This fragment was used as a probe for subsequent hybridization screening. Two clones were isolated that, based on sequence information, code for different receptors: a 3-kilobase clone, HBGR1, contains a full-length glutamate receptor cDNA highly homologous to the rat brain clone GluR1, and a second clone, HBGR2, contains approximately two-thirds of the coding region of a receptor homologous to rat brain clone GluR2. Southern and PCr analysis of a somatic cell-hybrid panel mapped HBGR1 to human chromosome 5q31.3-33.3 and mapped HBGR2 to chromosome 4q25-34.3. Xenopus oocytes injected with in vitro-synthesized HBGR1 cRNA expressed currents activated by glutamate receptor agonists. These results indicate that clone HBGR1 codes for a glutamate receptor of the kainate subtype cognate to members of the glutamate receptor family from rodent brain.

  19. [Comparative analysis of metabotropic and ionotropic glutamate striatal receptors blockade influence on rats locomotor behaviour].

    PubMed

    Iakimovskiĭ, A F; Kerko, T V

    2013-02-01

    The influence of NMDA and metabotropic neostriatal glutamate receptors blockade to avoidance conditioning (in shuttle box) and free locomotor behavior (in open field) in chronic experiments in rats were investigated. The glutamate receptor antagonists were injected bilateral into striatum separately and with the GABA-A receptor antagonist picrotoxin (2 microg), that produced in rats the impairment of avoidance conditioning and choreo-myoklonic hyperkinesis. The most effective in preventing of negative picrotoxin influence on behavior was 5-type metabotropic glutamate receptors antagonist MTEP (3 microg). Separately injected MTEP did not influence on avoidance conditioning and free locomotor behavior. Unlike that, 1-type metabotropic glutamate receptors antagonist EMQMCM (3 microg) impaired normal locomotor behavior and did not prevent the picrotoxin effects. The NMDA glutamate receptors MK 801 (disocilpin--1 and 5 microg) impaired the picrotoxin-induced hyperkinesis, but did not to prevent the negative effects on avoidance conditioning; separately injected MK 801 reduced free locomotor activity. Based on location of investigated receptor types in neostriatal neurons membranes, we proposed that the most effective influence on 5-type metabotropic glutamate receptors is associated with their involvement in "indirect" efferent pathway, suffered in hyperkinetic extrapyramidal motor dysfunction--Huntington's chorea in human.

  20. Recovery of network-driven glutamatergic activity in rat hippocampal neurons during chronic glutamate receptor blockade.

    PubMed

    Leininger, Eric; Belousov, Andrei B

    2009-01-28

    Previous studies indicated that a long-term decrease in the activity of ionotropic glutamate receptors induces cholinergic activity in rat and mouse hypothalamic neuronal cultures. Here we studied whether a prolonged inactivation of ionotropic glutamate receptors also induces cholinergic activity in hippocampal neurons. Receptor activity was chronically suppressed in rat hippocampal primary neuronal cultures with two proportionally increasing sets of concentrations of NMDA plus non-NMDA receptor antagonists: 100 microM/10 microM AP5/CNQX (1X cultures) and 200 microM/20 microM AP5/CNQX (2X cultures). Using calcium imaging we demonstrate that cholinergic activity does not develop in these cultures. Instead, network-driven glutamate-dependent activity, that normally is detected in hyper-excitable conditions, reappears in each culture group in the presence of these antagonists and can be reversibly suppressed by higher concentrations of AP5/CNQX. This activity is mediated by non-NMDA receptors and is modulated by NMDA receptors. Further, non-NMDA receptors, the general level of glutamate receptor activity and CaMK-dependent signaling are critical for development of this network-driven glutamatergic activity in the presence of receptor antagonists. Using electrophysiology, western blotting and calcium imaging we show that some neuronal parameters are either reduced or not affected by chronic glutamate receptor blockade. However, other parameters (including neuronal excitability, mEPSC frequency, and expression of GluR1, NR1 and betaCaMKII) become up-regulated and, in some cases, proportionally between the non-treated, 1X and 2X cultures. Our data suggest recovery of the network-driven glutamatergic activity after chronic glutamate receptor blockade. This recovery may represent a form of neuronal plasticity that compensates for the prolonged suppression of the activity of glutamate receptors.

  1. Mechanisms Associated with Activation of Intracellular Metabotropic Glutamate Receptor, mGluR5.

    PubMed

    Jong, Yuh-Jiin I; O'Malley, Karen L

    2017-01-01

    The group 1 metabotropic glutamate receptor, mGluR5, is found on the cell surface as well as on intracellular membranes where it can mediate both overlapping and unique signaling effects. Previously we have shown that glutamate activates intracellular mGluR5 by entry through sodium-dependent transporters and/or cystine glutamate exchangers. Calibrated antibody labelling suggests that the glutamate concentration within neurons is quite high (~10 mM) raising the question as to whether intracellular mGluR5 is maximally activated at all times or whether a different ligand might be responsible for receptor activation. To address this issue, we used cellular, optical and molecular techniques to show that intracellular glutamate is largely sequestered in mitochondria; that the glutamate concentration necessary to activate intracellular mGluR5 is about ten-fold higher than what is necessary to activate cell surface mGluR5; and uncaging caged glutamate within neurons can directly activate the receptor. Thus these studies further the concept that glutamate itself serves as the ligand for intracellular mGluR5.

  2. Simulation of Postsynaptic Glutamate Receptors Reveals Critical Features of Glutamatergic Transmission

    PubMed Central

    Greget, Renaud; Pernot, Fabien; Bouteiller, Jean-Marie C.; Ghaderi, Viviane; Allam, Sushmita; Keller, Anne Florence; Ambert, Nicolas; Legendre, Arnaud; Sarmis, Merdan; Haeberle, Olivier; Faupel, Michel; Bischoff, Serge; Berger, Theodore W.; Baudry, Michel

    2011-01-01

    Activation of several subtypes of glutamate receptors contributes to changes in postsynaptic calcium concentration at hippocampal synapses, resulting in various types of changes in synaptic strength. Thus, while activation of NMDA receptors has been shown to be critical for long-term potentiation (LTP) and long term depression (LTD) of synaptic transmission, activation of metabotropic glutamate receptors (mGluRs) has been linked to either LTP or LTD. While it is generally admitted that dynamic changes in postsynaptic calcium concentration represent the critical elements to determine the direction and amplitude of the changes in synaptic strength, it has been difficult to quantitatively estimate the relative contribution of the different types of glutamate receptors to these changes under different experimental conditions. Here we present a detailed model of a postsynaptic glutamatergic synapse that incorporates ionotropic and mGluR type I receptors, and we use this model to determine the role of the different receptors to the dynamics of postsynaptic calcium with different patterns of presynaptic activation. Our modeling framework includes glutamate vesicular release and diffusion in the cleft and a glutamate transporter that modulates extracellular glutamate concentration. Our results indicate that the contribution of mGluRs to changes in postsynaptic calcium concentration is minimal under basal stimulation conditions and becomes apparent only at high frequency of stimulation. Furthermore, the location of mGluRs in the postsynaptic membrane is also a critical factor, as activation of distant receptors contributes significantly less to calcium dynamics than more centrally located ones. These results confirm the important role of glutamate transporters and of the localization of mGluRs in postsynaptic sites in their signaling properties, and further strengthen the notion that mGluR activation significantly contributes to postsynaptic calcium dynamics only following

  3. Development of PET and SPECT Probes for Glutamate Receptors

    PubMed Central

    Nakayama, Morio

    2015-01-01

    l-Glutamate and its receptors (GluRs) play a key role in excitatory neurotransmission within the mammalian central nervous system (CNS). Impaired regulation of GluRs has also been implicated in various neurological disorders. GluRs are classified into two major groups: ionotropic GluRs (iGluRs), which are ligand-gated ion channels, and metabotropic GluRs (mGluRs), which are coupled to heterotrimeric guanosine nucleotide binding proteins (G-proteins). Positron emission tomography (PET) and single photon emission computed tomography (SPECT) imaging of GluRs could provide a novel view of CNS function and of a range of brain disorders, potentially leading to the development of new drug therapies. Although no satisfactory imaging agents have yet been developed for iGluRs, several PET ligands for mGluRs have been successfully employed in clinical studies. This paper reviews current progress towards the development of PET and SPECT probes for GluRs. PMID:25874256

  4. The multifaceted subunit interfaces of ionotropic glutamate receptors.

    PubMed

    Green, Tim; Nayeem, Naushaba

    2015-01-01

    The past fifteen years has seen a revolution in our understanding of ionotropic glutamate receptor (iGluR) structure, starting with the first view of the ligand binding domain (LBD) published in 1998, and in many ways culminating in the publication of the full-length structure of GluA2 in 2009. These reports have revealed not only the central role played by subunit interfaces in iGluR function, but also myriad binding sites within interfaces for endogenous and exogenous factors. Changes in the conformation of inter-subunit interfaces are central to transmission of ligand gating into pore opening (itself a rearrangement of interfaces), and subsequent closure through desensitization. With the exception of the agonist binding site, which is located entirely within individual subunits, almost all modulatory factors affecting iGluRs appear to bind to sites in subunit interfaces. This review seeks to summarize what we currently understand about the diverse roles interfaces play in iGluR function, and to highlight questions for future research.

  5. The multifaceted subunit interfaces of ionotropic glutamate receptors.

    PubMed

    Green, Tim; Nayeem, Naushaba

    2014-06-06

    The past fifteen years has seen a revolution in our understanding of ionotropic glutamate receptor (iGluR) structure, starting with the first view of the ligand binding domain (LBD) published in 1998, and in many ways culminating in the publication of the full-length structure of GluA2 in 2009. These reports have revealed not only the central role played by subunit interfaces in iGluR function, but also myriad binding sites within interfaces for endogenous and exogenous factors. Changes in the conformation of inter-subunit interfaces are central to transmission of ligand gating into pore opening (itself a rearrangement of interfaces), and subsequent closure through desensitization. With the exception of the agonist binding site, which is located entirely within individual subunits, almost all modulatory factors affecting iGluRs appear to bind to sites in subunit interfaces. This review seeks to summarize what we currently understand about the diverse roles interfaces play in iGluR function, and to highlight questions for future research.

  6. Telmisartan ameliorates glutamate-induced neurotoxicity: roles of AT1 receptor blockade and PPARγ activation

    PubMed Central

    Wang, Juan; Pang, Tao; Hafko, Roman; Benicky, Julius; Sanchez-Lemus, Enrique; Saavedra, Juan M.

    2014-01-01

    Sartans (Angiotensin II AT1 Receptor Blockers, ARBs) are powerful neuroprotective agents in vivo and protect against IL-1β neurotoxicity in vitro. The purpose of this research was to determine the extent of sartan neuroprotection against glutamate excitotoxicity, a common cause of neuronal injury and apoptosis. The results show that sartans are neuroprotective, significantly reducing glutamate-induced neuronal injury and apoptosis in cultured rat primary cerebellar granule cells (CGCs). Telmisartan was the most potent sartan studied, with an order of potency telmisartan > candesartan > losartan > valsartan. Mechanisms involved reduction of pro-apoptotic caspase-3 activation, protection of the survival PI3K/Akt/GSK-3β pathway, and prevention of glutamate-induced ERK1/2 activation. NMDA receptor stimulation was essential for glutamate-induced cell injury and apoptosis. Participation of AT1A receptor was supported by glutamate-induced upregulation of AT1A gene expression and AT1 receptor binding. Conversely, AT1B or AT2 receptor played no role. Glutamate-induced neuronal injury and the neuroprotective effect of telmisartan were decreased, but not abolished, in CGCs obtained from AT1A knock-out mice. This indicates that although AT1 receptors are necessary for glutamate to exert its full neurotoxic potential, part of the neuroprotective effect of telmisartan is independent of AT1 receptor blockade. PPARγ activation was also involved in the neuroprotective effects of telmisartan, as telmisartan enhanced PPARγ nuclear translocation, and the PPARγ antagonist GW9662 partially reversed the neuroprotective effects of telmisartan. The present results substantiate the therapeutic use of sartans, in particular telmisartan, in neurodegenerative diseases and traumatic brain disorders where glutamate neurotoxicity plays a significant role. PMID:24316465

  7. Role of glutamate receptors in tetrabrominated diphenyl ether (BDE-47) neurotoxicity in mouse cerebellar granule neurons

    PubMed Central

    Costa, Lucio G.; Tagliaferri, Sara; Roqué, Pamela J.; Pellacani, Claudia

    2015-01-01

    The polybrominated diphenyl ether (PBDE) flame retardants are developmental neurotoxicants, as evidenced by numerous in vitro, animal and human studies. PBDEs can alter the homeostasis of thyroid hormone and directly interact with brain cells. Induction of oxidative stress, leading to DNA damage and apoptotic cell death is a prominent mechanism of PBDE neurotoxicity, though other mechanisms have also been suggested. In the present study we investigated the potential role played by glutamate receptors in the in vitro neurotoxicity of the tetrabromodiphenyl ether BDE-47, one of the most abundant PBDE congeners. Toxicity of BDE-47 in mouse cerebellar neurons was diminished by antagonists of glutamate ionotropic receptors, but not by antagonists of glutamate metabotropic receptors. Antagonists of NMDA and AMPA/Kainate receptors also inhibited BDE-47-induced oxidative stress and increases in intracellular calcium. The calcium chelator BAPTA-AM also inhibited BDE-47 cytotoxicity and oxidative stress. BDE-47 caused a rapid increase of extracellular glutamate levels, which was not antagonized by any of the compounds tested. The results suggest that BDE-47, by still unknown mechanisms, increases extracellular glutamate which in turn activates ionotropic glutamate receptors leading to increased calcium levels, oxidative stress, and ultimately cell death. PMID:26640238

  8. The role of glutamate and its receptors in autism and the use of glutamate receptor antagonists in treatment

    PubMed Central

    Rojas, Donald C.

    2014-01-01

    Glutamate is the major excitatory neurotransmitter in the brain and may be a key neurotransmitter involved in autism. Literature pertaining to glutamate and autism or related disorders (e.g., Fragile X syndrome) is reviewed in this article. Interest in glutamatergic dysfunction in autism is high due to increasing convergent evidence implicating the system in the disorder from peripheral biomarkers, neuroimaging, protein expression, genetics and animal models. Currently, there are no pharmaceutical interventions approved for autism that address glutamate deficits in the disorder. New treatments related to glutamatergic neurotransmission, however, are emerging. In addition, older glutamate-modulating medications with approved indications for use in other disorders are being investigated for re-tasking as treatments for autism. This review presents evidence in support of glutamate abnormalities in autism and the potential for translation into new treatments for the disorder. PMID:24752754

  9. Metabotropic glutamate receptors differentially regulate GABAergic inhibition in thalamus.

    PubMed

    Govindaiah, G; Cox, Charles L

    2006-12-27

    Thalamic interneurons and thalamic reticular nucleus (TRN) neurons provide inhibitory innervation of thalamocortical cells that significantly influence thalamic gating. The local interneurons in the dorsal lateral geniculate nucleus (dLGN) give rise to two distinct synaptic outputs: classical axonal and dendrodendritic. Activation of metabotropic glutamate receptors (mGluRs) by agonists or optic tract stimulation increases the output of these presynaptic dendrites leading to increased inhibition of thalamocortical neurons. The present study was aimed to evaluate the actions of specific mGluRs on inhibitory GABA-mediated signaling. We found that the group I mGluR (mGluR(1,5)) agonist (RS)-3,5-dihydroxyphenylglycine (DHPG) or optic tract stimulation produced a robust increase in spontaneous IPSCs (sIPSCs) in thalamocortical neurons that was attenuated by the selective mGluR(5) antagonist 2-methyl-6-(phenylethynyl)pyridine hydrochloride (MPEP). In contrast, the group II mGluR (mGluR(2,3)) agonists (2R, 4R)-4-aminopyrrolidine-2,4-dicarboxylate (APDC) or (2S,2'R,3'R)-2-(2'3'-dicarboxycyclopropyl)glycine (DCG-IV) suppressed the frequency of sIPSCs. In addition, mGluR(1,5) agonist DHPG produced depolarizations and mGluR(2/3) agonists APDC or L-CCG-I [(2S,1'S,2'S)-2-(carboxycyclopropyl)glycine] produced hyperpolarizations in dLGN interneurons. Furthermore, the enhanced sIPSC activity by optic tract stimulation was reduced when paired with corticothalamic fiber stimulation. The present data indicate that activation of specific mGluR subtypes differentially regulates inhibitory activity via different synaptic pathways. Our results suggest that activation of specific mGluR subtypes can upregulate or downregulate inhibitory activity in thalamic relay neurons, and these actions likely shape excitatory synaptic integration and thus regulate information transfer through thalamocortical circuits.

  10. Involvement of metabotropic glutamate 5 receptor in visceral pain.

    PubMed

    Lindström, Erik; Brusberg, Mikael; Hughes, Patrick A; Martin, Christopher M; Brierley, Stuart M; Phillis, Benjamin D; Martinsson, Rakel; Abrahamsson, Christina; Larsson, Håkan; Martinez, Vicente; Blackshaw, L Ashley

    2008-07-15

    Metabotropic glutamate 5 receptor (mGluR5) antagonists are effective in animal models of inflammatory and neuropathic pain. The involvement of mGluR5 in visceral pain pathways from the gastrointestinal tract is as yet unknown. We evaluated effects of mGluR5 antagonists on the colorectal distension (CRD)-evoked visceromotor (VMR) and cardiovascular responses in conscious rats, and on mechanosensory responses of mouse colorectal afferents in vitro. Sprague-Dawley rats were subjected to repeated, isobaric CRD (12 x 80 mmHg, for 30s with 5 min intervals). The VMR and cardiovascular responses to CRD were monitored. The mGluR5 antagonists MPEP (1-10 micromol/kg, i.v.) and MTEP (1-3 micromol/kg, i.v.) reduced the VMR to CRD dose-dependently with maximal inhibition of 52+/-8% (p<0.01) and 25+/-11% (p<0.05), respectively, without affecting colonic compliance. MPEP (10 micromol/kg, i.v.) reduced CRD-evoked increases in blood pressure and heart rate by 33+/-9% (p<0.01) and 35+/-8% (p<0.05), respectively. Single afferent recordings were made from mouse pelvic and splanchnic nerves of colorectal mechanoreceptors. Circumferential stretch (0-5 g force) elicited slowly-adapting excitation of action potentials in pelvic distension-sensitive afferents. This response was reduced 55-78% by 10 microM MTEP (p<0.05). Colonic probing (2g von Frey hair) activated serosal splanchnic afferents; their responses were reduced 50% by 10 microM MTEP (p<0.01). We conclude that mGluR5 antagonists inhibit CRD-evoked VMR and cardiovascular changes in conscious rats, through an effect, at least in part, at peripheral afferent endings. Thus, mGluR5 participates in mediating mechanically evoked visceral nociception in the gastrointestinal tract.

  11. Activation of Group I Metabotropic Glutamate Receptors Potentiates Heteromeric Kainate Receptors

    PubMed Central

    Wetherington, Jonathon; Shaw, Renee; Serrano, Geidy; Swanger, Sharon; Dingledine, Raymond

    2013-01-01

    Kainate receptors (KARs), a family of ionotropic glutamate receptors, are widely expressed in the central nervous system and are critically involved in synaptic transmission. KAR activation is influenced by metabotropic glutamate receptor (mGlu) signaling, but the underlying mechanisms are not understood. We undertook studies to examine how mGlu modulation affects activation of KARs. Confocal immunohistochemistry of rat hippocampus and cultured rat cortex revealed colocalization of the high-affinity KAR subunits with group I mGlu receptors. In hippocampal and cortical cultures, the calcium signal caused by activation of native KARs was potentiated by activation of group I mGlu receptors. In Xenopus laevis oocytes, activation of group I mGlu receptors potentiated heteromeric but not homomeric KAR-mediated currents, with no change in agonist potency. The potentiation of heteromeric KARs by mGlu1 activation was attenuated by GDPβS, blocked by an inhibitor of phospholipase C or the calcium chelator 1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA), prolonged by the phosphatase inhibitor okadaic acid, but unaffected by the tyrosine kinase inhibitor lavendustin A. Protein kinase C (PKC) inhibition reduced the potentiation by mGlu1 of GluK2/GluK5, and conversely, direct activation of PKC by phorbol 12-myristate,13-acetate potentiated GluK2/GluK5. Using site-directed mutagenesis, we identified three serines (Ser833, Ser836, and Ser840) within the membrane proximal region of the GluK5 C-terminal domain that, in combination, are required for mGlu1-mediated potentiation of KARs. Together, these data suggest that phosphorylation of key residues in the C-terminal domain changes the overall charge of this domain, resulting in potentiated agonist responses. PMID:23066089

  12. Metabotropic glutamate receptor-mediated signaling dampens the HPA axis response to restraint stress.

    PubMed

    Evanson, Nathan K; Herman, James P

    2015-10-15

    Glutamate is an important neurotransmitter in the regulation of the neural portion of hypothalamus-pituitary-adrenal (HPA) axis activity, and signals through ionotropic and metabotropic receptors. In the current studies we investigated the role of hypothalamic paraventricular group I metabotropic glutamate receptors in the regulation of the HPA axis response to restraint stress in rats. Direct injection of the group I metabotropic glutamate receptor agonist 3,5-dihydroxyphenylglycine (DHPG) into the PVN prior to restraint leads to blunting of the HPA axis response in awake animals. Consistent with this result, infusion of the group I receptor antagonist hexyl-homoibotenic acid (HIBO) potentiates the HPA axis response to restraint. The excitatory effect of blocking paraventricular group I metabotropic glutamate signaling is blocked by co-administration of dexamethasone into the PVN. However, the inhibitory effect of DHPG is not affected by co-administration of the cannabinoid CB1 receptor antagonist AM-251 into the PVN. Together, these results suggest that paraventricular group I metabotropic glutamate receptor signaling acts to dampen HPA axis reactivity. This effect appears to be similar to the rapid inhibitory effect of glucocorticoids at the PVN, but is not mediated by endocannabinoid signaling.

  13. Regulation of synaptic signalling by postsynaptic, non-glutamate receptor ion channels

    PubMed Central

    Bloodgood, Brenda L; Sabatini, Bernardo L

    2008-01-01

    Activation of glutamatergic synapses onto pyramidal neurons produces a synaptic depolarization as well as a buildup of intracellular calcium (Ca2+). The synaptic depolarization propagates through the dendritic arbor and can be detected at the soma with a recording electrode. Current influx through AMPA-type glutamate receptors (AMPARs) provides the depolarizing drive, and the amplitudes of synaptic potentials are generally thought to reflect the number and properties of these receptors at each synapse. In contrast, synaptically evoked Ca2+ transients are limited to the spine containing the active synapse and result primarily from Ca2+ influx through NMDA-type glutamate receptors (NMDARs). Here we review recent studies that reveal that both synaptic depolarizations and spine head Ca2+ transients are strongly regulated by the activity of postsynaptic, non-glutamate receptor ion channels. In hippocampal pyramidal neurons, voltage- and Ca2+-gated ion channels located in dendritic spines open as downstream consequences of glutamate receptor activation and act within a complex signalling loop that feeds back to regulate synaptic signals. Dynamic regulation of these ion channels offers a powerful mechanism of synaptic plasticity that is independent of direct modulation of glutamate receptors. PMID:18096597

  14. Excitatory amino acids acting on metabotropic glutamate receptors broaden the action potential in hippocampal neurons.

    PubMed

    Hu, G Y; Storm, J F

    1991-12-24

    Activation of metabotropic glutamate receptors (mGluRs, QP or ACPD receptors) has recently been shown to cause depolarization, blockade of the slow after-hyperpolarization and depression of calcium currents in hippocampal pyramidal cells. Here, we report evidence for a new mGluR-mediated effect: slowing of the spike repolarization in CA1 cells in rat hippocampal slices. During blockade of the ionotropic glutamate receptors, the mGluR agonists trans-1-amino-cyclopentyl-1,3-dicarboxylate (t-ACPD), quisqualate or L-glutamate caused spike broadening. In contrast, the ionotropic receptor agonist alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA) was ineffective. The spike broadening may act in concert with the other mGluR effects, e.g. by further increasing the influx of Ca2+ ions which, in turn, may contribute to synaptic modulation.

  15. Allosteric activation of membrane-bound glutamate receptors using coordination chemistry within living cells

    NASA Astrophysics Data System (ADS)

    Kiyonaka, Shigeki; Kubota, Ryou; Michibata, Yukiko; Sakakura, Masayoshi; Takahashi, Hideo; Numata, Tomohiro; Inoue, Ryuji; Yuzaki, Michisuke; Hamachi, Itaru

    2016-10-01

    The controlled activation of proteins in living cells is an important goal in protein-design research, but to introduce an artificial activation switch into membrane proteins through rational design is a significant challenge because of the structural and functional complexity of such proteins. Here we report the allosteric activation of two types of membrane-bound neurotransmitter receptors, the ion-channel type and the G-protein-coupled glutamate receptors, using coordination chemistry in living cells. The high programmability of coordination chemistry enabled two His mutations, which act as an artificial allosteric site, to be semirationally incorporated in the vicinity of the ligand-binding pockets. Binding of Pd(2,2‧-bipyridine) at the allosteric site enabled the active conformations of the glutamate receptors to be stabilized. Using this approach, we were able to activate selectively a mutant glutamate receptor in live neurons, which initiated a subsequent signal-transduction pathway.

  16. In vivo modulation of alpha7 nicotinic receptors on striatal glutamate release induced by anatoxin-A.

    PubMed

    Campos, F; Alfonso, M; Durán, R

    2010-01-01

    In vitro studies suggest that alpha7 nicotinic receptors located on striatal glutamatergic terminals stimulate the release of glutamate which in turn acts at ionotropic glutamate receptors on dopaminergic terminals to increase dopamine release. However, this mechanism has never been observed in in vivo studies. In the present work, the effect of the nicotinic receptors agonist, anatoxin-a, on striatal glutamate and dopamine release has been studied. Using in vivo microdialysis technique, our results have shown that anatoxin-a evokes glutamate release in a dependent way of activation alpha7 nicotinic receptors. The increase of glutamate is followed by an increase on dopamine levels. These results represent a clear in vivo evidence of the striatal modulation of dopamine by means of glutamate release through alpha7 nicotinic receptors.

  17. Neurobeachin Regulates Glutamate- and GABA-Receptor Targeting to Synapses via Distinct Pathways.

    PubMed

    Farzana, F; Zalm, R; Chen, N; Li, K W; Grant, Seth G N; Smit, A B; Toonen, R F; Verhage, M

    2016-05-01

    Neurotransmission and synaptic strength depend on expression of post-synaptic receptors on the cell surface. Post-translational modification of receptors, trafficking to the synapse through the secretory pathway, and subsequent insertion into the synapse involves interaction of the receptor with A-kinase anchor proteins (AKAPs) and scaffolding proteins. Neurobeachin (Nbea), a brain specific AKAP, is required for synaptic surface expression of both glutamate and GABA receptors. Here, we investigated the role of Nbea-dependent targeting of postsynaptic receptors by studying Nbea interaction with synapse-associated protein 102 (SAP102/Dlg3) and protein kinase A subunit II (PKA II). A Nbea mutant lacking the PKA binding domain showed a similar distribution as wild-type Nbea in Nbea null neurons and partially restored GABA receptor surface expression. To understand the relevance of Nbea interaction with SAP102, we analysed SAP102 null mutant mice. Nbea levels were reduced by ~80% in SAP102 null mice, but glutamatergic receptor expression was normal. A single-point mutation in the pleckstrin homology domain of Nbea (E2218R) resulted in loss of binding with SAP102. When expressed in Nbea null neurons, this mutant fully restored GABA receptor surface expression, but not glutamate receptor expression. Our results suggest that the PKA-binding domain is not essential for Nbea's role in receptor targeting and that Nbea targets glutamate and GABA receptors to the synapse via distinct molecular pathways by interacting with specific effector proteins.

  18. Downregulation of postsynaptic density-95-interacting regulator of spine morphogenesis reduces glutamate-induced excitotoxicity by differentially regulating glutamate receptors in rat cortical neurons.

    PubMed

    Luo, Peng; Yang, Yuefan; Liu, Wei; Rao, Wei; Bian, Huan; Li, Xin; Chen, Tao; Liu, Mengdong; Zhao, Yongbo; Dai, Shuhui; Yan, Xu; Fei, Zhou

    2013-12-01

    Glutamate-induced excitotoxicity is involved in many neurological diseases. Preso, a novel postsynaptic scaffold protein, mediates excitatory synaptic transmission and various synaptic functions. In this study, we investigated the role of Preso in the regulation of glutamate-induced excitotoxicity in rat cortical neurons. Knockdown of Preso with small interfering RNA improved neuronal viability and attenuated the elevation of lactate dehydrogenase (LDH) release after glutamate treatment. Downregulation of Preso also inhibited an increase in the BAX/Bcl-2 ratio and cleavage of caspase-9 and caspase-3. Although the expression and distribution of metabotropic glutamate receptor (mGluR) 1/5, NR1, NR2A and NR2B were not changed by knockdown of Preso, downregulation of Preso protected neurons from glutamate-induced excitotoxicity by inhibiting mGluR and N-methyl-D-aspartate receptor function. However, downregulation of Preso neither affected the expression of GluR1 and GluR2 nor influenced the function of α-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor after glutamate treatment. Furthermore, intracellular Ca(2+) was an important downstream effector of Preso in the regulation of excitotoxicity. These results suggest that expression of Preso promotes the induction of excitotoxicity by facilitating different glutamate receptor signaling pathways. Therefore, Preso might be a potential pharmacological target for preventing and treating neurological diseases.

  19. Immunohistochemical localization of ionotropic glutamate receptors in the rat red nucleus

    PubMed Central

    Minbay, Zehra; Kocoglu, Sema Serter; Yurtseven, Duygu Gok; Eyigor, Ozhan

    2017-01-01

    In this study, we aimed to determine the presence as well as the diverse distribution of N-methyl-D-aspartate (NMDA) and non-NMDA glutamate receptor subunits in the rat red nucleus. Using adult Sprague-Dawley rats as the experimental animals, immunohistochemistry was performed on 30 µm thick coronal brain sections with antibodies against α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (GluA1-4), kainate (GluK1, GluK2/3, and GluK5), and NMDA (GluN1 and GluN2A) receptor subunits. The results showed that all ionotropic glutamate receptor subunits are expressed in the red nucleus. Specific staining was localized in the neuron bodies and processes. However, the pattern of immunoreactivity and the number of labeled neurons changed depending on the type of ionotropic glutamate receptor subunits and the localization of neurons in the red nucleus. The neurons localized in the magnocellular part of the red nucleus were particularly immunopositive for GluA2, GluA4, GluK2/3, GluK5, GluN1, and GluN2A receptor proteins. In the parvocellular part of the red nucleus, ionotropic glutamate receptor subunit immunoreactivity of variable intensity (lightly to moderately stained) was detected in the neurons. These results suggest that red nucleus neurons in rat heterogeneously express ionotropic glutamate receptor subunits to form functional receptor channels. In addition, the likelihood of the coexpression of different subunits in the same subgroup of neurons suggests the formation of receptor channels with diverse structure by way of different subunit combination, and the possibility of various neuronal functions through these channels in the red nucleus. PMID:28027456

  20. Domain-based identification and analysis of glutamate receptor ion channels and their relatives in prokaryotes.

    PubMed

    Ger, Mao-Feng; Rendon, Gloria; Tilson, Jeffrey L; Jakobsson, Eric

    2010-10-06

    Voltage-gated and ligand-gated ion channels are used in eukaryotic organisms for the purpose of electrochemical signaling. There are prokaryotic homologues to major eukaryotic channels of these sorts, including voltage-gated sodium, potassium, and calcium channels, Ach-receptor and glutamate-receptor channels. The prokaryotic homologues have been less well characterized functionally than their eukaryotic counterparts. In this study we identify likely prokaryotic functional counterparts of eukaryotic glutamate receptor channels by comprehensive analysis of the prokaryotic sequences in the context of known functional domains present in the eukaryotic members of this family. In particular, we searched the nonredundant protein database for all proteins containing the following motif: the two sections of the extracellular glutamate binding domain flanking two transmembrane helices. We discovered 100 prokaryotic sequences containing this motif, with a wide variety of functional annotations. Two groups within this family have the same topology as eukaryotic glutamate receptor channels. Group 1 has a potassium-like selectivity filter. Group 2 is most closely related to eukaryotic glutamate receptor channels. We present analysis of the functional domain architecture for the group of 100, a putative phylogenetic tree, comparison of the protein phylogeny with the corresponding species phylogeny, consideration of the distribution of these proteins among classes of prokaryotes, and orthologous relationships between prokaryotic and human glutamate receptor channels. We introduce a construct called the Evolutionary Domain Network, which represents a putative pathway of domain rearrangements underlying the domain composition of present channels. We believe that scientists interested in ion channels in general, and ligand-gated ion channels in particular, will be interested in this work. The work should also be of interest to bioinformatics researchers who are interested in the use

  1. G-protein coupled receptor-evoked glutamate exocytosis from astrocytes: role of prostaglandins.

    PubMed

    Cali, Corrado; Lopatar, Jan; Petrelli, Francesco; Pucci, Luca; Bezzi, Paola

    2014-01-01

    Astrocytes are highly secretory cells, participating in rapid brain communication by releasing glutamate. Recent evidences have suggested that this process is largely mediated by Ca(2+)-dependent regulated exocytosis of VGLUT-positive vesicles. Here by taking advantage of VGLUT1-pHluorin and TIRF illumination, we characterized mechanisms of glutamate exocytosis evoked by endogenous transmitters (glutamate and ATP), which are known to stimulate Ca(2+) elevations in astrocytes. At first we characterized the VGLUT1-pHluorin expressing vesicles and found that VGLUT1-positive vesicles were a specific population of small synaptic-like microvesicles containing glutamate but which do not express VGLUT2. Endogenous mediators evoked a burst of exocytosis through activation of G-protein coupled receptors. Subsequent glutamate exocytosis was reduced by about 80% upon pharmacological blockade of the prostaglandin-forming enzyme, cyclooxygenase. On the other hand, receptor stimulation was accompanied by extracellular release of prostaglandin E2 (PGE2). Interestingly, administration of exogenous PGE2 produced per se rapid, store-dependent burst exocytosis of glutamatergic vesicles in astrocytes. Finally, when PGE2-neutralizing antibody was added to cell medium, transmitter-evoked exocytosis was again significantly reduced (by about 50%). Overall these data indicate that cyclooxygenase products are responsible for a major component of glutamate exocytosis in astrocytes and that large part of such component is sustained by autocrine/paracrine action of PGE2.

  2. Ionotropic AMPA-type glutamate and metabotropic GABAB receptors: determining cellular physiology by proteomes.

    PubMed

    Bettler, Bernhard; Fakler, Bernd

    2017-03-07

    Ionotropic AMPA-type glutamate receptors and G-protein-coupled metabotropic GABAB receptors are key elements of neurotransmission whose cellular functions are determined by their protein constituents. Over the past couple of years unbiased proteomic approaches identified comprehensive sets of protein building blocks of these two types of neurotransmitter receptors in the brain (termed receptor proteomes). This provided the opportunity to match receptor proteomes with receptor physiology and to study the structural organization, regulation and function of native receptor complexes in an unprecedented manner. In this review we discuss the principles of receptor architecture and regulation emerging from the functional characterization of the proteomes of AMPA and GABAB receptors. We also highlight progress in unraveling the role of unexpected protein components for receptor physiology.

  3. Effects of metabotropic glutamate receptor activation in auditory thalamus.

    PubMed

    Tennigkeit, F; Schwarz, D W; Puil, E

    1999-08-01

    Metabotropic glutamate receptors (mGluRs) are expressed predominantly in dendritic regions of neurons of auditory thalamus. We studied the effects of mGluR activation in neurons of the ventral partition of medial geniculate body (MGBv) using whole cell current- and voltage-clamp recordings in brain slices. Bath application of the mGluR-agonist, 1S,3R-1-aminocyclopentan-1,3-dicarboxylic acid or 1S,3R-ACPD (5-100 microM), depolarized MGBv neurons (n = 67), changing evoked response patterns from bursts to tonic firing as well as frequency responses from resonance ( approximately 1 Hz) to low-pass filter characteristics. The depolarization was resistant to Na(+)-channel blockade with tetrodotoxin (TTX; 300 nM) and Ca(2+)-channel blockade with Cd(2+) (0.1 mM). The application of 1S, 3R-ACPD did not change input conductance and produced an inward current (I(ACPD)) with an average amplitude of 84.2 +/- 5.3 pA (at -70 mV, n = 22). The application of the mGluR antagonist, (RS)-alpha-methyl-4-carboxyphenylglycine (0.5 mM), reversibly blocked the depolarization or I(ACPD). During intracellular application of guanosine 5'-O-(3-thiotriphosphate) from the recording electrode, bath application of 1S,3R-ACPD irreversibly activated a large amplitude I(ACPD). During intracellular application of guanosine 5'-O-(2-thiodiphosphate), application of 1S, 3R-ACPD evoked only a small I(ACPD). These results implicate G proteins in mediation of the 1S,3R-ACPD response. A reduction of external [Na(+)] from 150 to 26 mM decreased I(ACPD) to 32.8 +/- 10. 3% of control. Internal applications of a Ca(2+) chelator, 1, 2-bis-(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA; 10 mM), suppressed I(ACPD), implying a contribution of a Ca(2+) signal or Na(+)/Ca(2+) exchange. However, partial replacement of Na(+) with Li(+) (50 mM) did not significantly change I(ACPD). Therefore it seemed less likely that a Na(+)/Ca(2+) exchange current was a major participant in the response. A reduction of

  4. Presynaptic c-Jun N-terminal Kinase 2 regulates NMDA receptor-dependent glutamate release

    PubMed Central

    Nisticò, Robert; Florenzano, Fulvio; Mango, Dalila; Ferraina, Caterina; Grilli, Massimo; Di Prisco, Silvia; Nobili, Annalisa; Saccucci, Stefania; D'Amelio, Marcello; Morbin, Michela; Marchi, Mario; Mercuri, Nicola B.; Davis, Roger J.; Pittaluga, Anna; Feligioni, Marco

    2015-01-01

    Activation of c-Jun N-terminal kinase (JNK) signaling pathway is a critical step for neuronal death occurring in several neurological conditions. JNKs can be activated via receptor tyrosine kinases, cytokine receptors, G-protein coupled receptors and ligand-gated ion channels, including the NMDA glutamate receptors. While JNK has been generally associated with postsynaptic NMDA receptors, its presynaptic role remains largely unexplored. Here, by means of biochemical, morphological and functional approaches, we demonstrate that JNK and its scaffold protein JIP1 are also expressed at the presynaptic level and that the NMDA-evoked glutamate release is controlled by presynaptic JNK-JIP1 interaction. Moreover, using knockout mice for single JNK isoforms, we proved that JNK2 is the essential isoform in mediating this presynaptic event. Overall the present findings unveil a novel JNK2 localization and function, which is likely to play a role in different physiological and pathological conditions. PMID:25762148

  5. A Temporally Distinct Role for Group I and Group II Metabotropic Glutamate Receptors in Object Recognition Memory

    ERIC Educational Resources Information Center

    Brown, Malcolm Watson; Warburton, Elizabeth Clea; Barker, Gareth Robert Isaac; Bashir, Zafar Iqbal

    2006-01-01

    Recognition memory, involving the ability to discriminate between a novel and familiar object, depends on the integrity of the perirhinal cortex (PRH). Glutamate, the main excitatory neurotransmitter in the cortex, is essential for many types of memory processes. Of the subtypes of glutamate receptor, metabotropic receptors (mGluRs) have received…

  6. 5-HT2 presynaptic receptors mediate inhibition of glutamate release from cerebellar mossy fibre terminals.

    PubMed

    Maura, G; Carbone, R; Guido, M; Pestarino, M; Raiteri, M

    1991-09-17

    'Giant' synaptosomes originating from mossy fibre terminals and having sedimentation properties different from those of standard synaptosomes were obtained from rat cerebellum. Exposure of superfused giant synaptosomes to 15 mM KCl caused the release of endogenous glutamate in a largely (about 80%) calcium-dependent manner. The K(+)-evoked overflow of glutamate was inhibited in a concentration-dependent manner by 5-hydroxytryptamine (5-HT) and by the 5-HT2 receptor agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane HCl (DOI), but not by the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT). The effects of 5-HT and DOI were quite potent, already reaching significant inhibition (about 25%) at 10 nM. The 5-HT2 receptor antagonist ketanserin counteracted the inhibitory effect of 5-HT. In cerebellar slices, ketanserin increased on its own the calcium-dependent K(+)-evoked release of glutamate and this effect was not prevented by tetrodotoxin (TTX). The results support the idea that cerebellar mossy fibres use glutamate as a transmitter and show that the release of glutamate can be inhibited via presynaptic heteroreceptors of the 5-HT2 type probably localized on the mossy fibre terminals.

  7. Presynaptic GluN2D receptors detect glutamate spillover and regulate cerebellar GABA release

    PubMed Central

    Dubois, Christophe J.; Lachamp, Philippe M.; Sun, Lu; Mishina, Masayoshi

    2015-01-01

    Glutamate directly activates N-methyl-d-aspartate (NMDA) receptors on presynaptic inhibitory interneurons and enhances GABA release, altering the excitatory-inhibitory balance within a neuronal circuit. However, which class of NMDA receptors is involved in the detection of glutamate spillover is not known. GluN2D subunit-containing NMDA receptors are ideal candidates as they exhibit a high affinity for glutamate. We now show that cerebellar stellate cells express both GluN2B and GluN2D NMDA receptor subunits. Genetic deletion of GluN2D subunits prevented a physiologically relevant, stimulation-induced, lasting increase in GABA release from stellate cells [long-term potentiation of inhibitory transmission (I-LTP)]. NMDA receptors are tetramers composed of two GluN1 subunits associated to either two identical subunits (di-heteromeric receptors) or to two different subunits (tri-heteromeric receptors). To determine whether tri-heteromeric GluN2B/2D NMDA receptors mediate I-LTP, we tested the prediction that deletion of GluN2D converts tri-heteromeric GluN2B/2D to di-heteromeric GluN2B NMDA receptors. We find that prolonged stimulation rescued I-LTP in GluN2D knockout mice, and this was abolished by GluN2B receptor blockers that failed to prevent I-LTP in wild-type mice. Therefore, NMDA receptors that contain both GluN2D and GluN2B mediate the induction of I-LTP. Because these receptors are not present in the soma and dendrites, presynaptic tri-heteromeric GluN2B/2D NMDA receptors in inhibitory interneurons are likely to mediate the cross talk between excitatory and inhibitory transmission. PMID:26510761

  8. Group II metabotropic glutamate receptors modify N-methyl-D-aspartate receptors via Src kinase

    PubMed Central

    Trepanier, Catherine; Lei, Gang; Xie, Yu-Feng; MacDonald, John F.

    2013-01-01

    Group II metabotropic glutamate receptors (mGluR2/3) have emerged as important targets for the treatment of schizophrenia. Since hypofunction of N-methyl-D-aspartate receptors (NMDARs) has also been implicated in the etiology of schizophrenia, we examined whether postsynaptic mGluR2/3 regulate NMDAR function. Activation of mGluR2/3 significantly decreased the ratio of AMPA-to-NMDA excitatory postsynaptic currents at Schaffer Collateral-CA1 synapses and enhanced the peak of NMDA-evoked currents in acutely isolated CA1 neurons. The mGluR2/3-mediated potentiation of NMDAR currents was selective for GluN2A-containing NMDARs and was mediated by the Src family kinase Src. Activation of mGluR2/3 inhibited the adenylyl cyclase-cAMP-PKA pathway and thereby activated Src by inhibiting its regulatory C-terminal Src kinase (Csk). We suggest a novel model of regulation of NMDARs by Gi/o-coupled receptors whereby inhibition of the cAMP-PKA pathway via mGluR2/3 activates Src kinase and potentiates GluN2A-containing NMDAR currents. This represents a potentially novel mechanism to correct the hypoglutamatergic state found in schizophrenia. PMID:23378895

  9. Striatal dopamine and glutamate receptors modulate methamphetamine-induced cortical Fos expression

    PubMed Central

    Gross, Noah B.; Marshall, John F.

    2009-01-01

    Methamphetamine (mAMPH) is a psychostimulant drug that increases extracellular levels of monoamines throughout the brain. It has previously been observed that a single injection of mAMPH increases immediate early gene (IEG) expression in both the striatum and cerebral cortex. Moreover, this effect is modulated by dopamine and glutamate receptors since systemic administration of dopamine or glutamate antagonists has been found to alter mAMPH-induced striatal and cortical IEG expression. However, because dopamine and glutamate receptors are found in extra-striatal as well as striatal brain regions, studies employing systemic injection of dopamine or glutamate antagonists fail to localize the effects of mAMPH-induced activation. In the present experiments, the roles of striatal dopamine and glutamate receptors in mAMPH-induced gene expression in the striatum and cerebral cortex were examined. The nuclear expression of Fos, the protein product of the IEG c-fos, was quantified in both the striatum and the cortex of animals receiving intrastriatal dopamine or glutamate antagonist administration. Intrastriatal infusion of dopamine (D1 or D2) or glutamate [N-methyl-D-aspartic acid (NMDA) or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)] antagonists affected not only mAMPH-induced striatal, but also cortical, Fos expression. Overall, the effects of the antagonists occurred dose-dependently, in both the infused and non-infused hemispheres, with greater influences occurring in the infused hemisphere. Finally, unilateral intrastriatal infusion of dopamine or glutamate antagonists changed the behavior of the rats from characteristic mAMPH-induced stereotypy to rotation ipsilateral to the infusion. These results demonstrate that mAMPH’s actions on striatal dopamine and glutamate receptors modulate the widespread cortical activation induced by mAMPH. It is hypothesized that dopamine release from nigrostriatal terminals modulates activity within striatal

  10. Lack of the Metabotropic Glutamate Receptor Subtype 7 Selectively Modulates Theta Rhythm and Working Memory

    ERIC Educational Resources Information Center

    Holscher, Christian; Schmid, Susanne; Pilz, Peter K. D.; Sansig, Gilles; van der Putten, Herman; Plappert, Claudia F.

    2005-01-01

    Metabotropic glutamate receptors (mGluRs) are known to play a role in synaptic plasticity and learning. We have previously shown that mGluR7 deletion in mice produces a selective working memory (WM) impairment, while other types of memory such as reference memory remain unaffected. Since WM has been associated with Theta activity (6-12 Hz) in…

  11. Glycine activated ion channel subunits encoded by ctenophore glutamate receptor genes

    PubMed Central

    Alberstein, Robert; Grey, Richard; Zimmet, Austin; Simmons, David K.; Mayer, Mark L.

    2015-01-01

    Recent genome projects for ctenophores have revealed the presence of numerous ionotropic glutamate receptors (iGluRs) in Mnemiopsis leidyi and Pleurobrachia bachei, among our earliest metazoan ancestors. Sequence alignments and phylogenetic analysis show that these form a distinct clade from the well-characterized AMPA, kainate, and NMDA iGluR subtypes found in vertebrates. Although annotated as glutamate and kainate receptors, crystal structures of the ML032222a and PbiGluR3 ligand-binding domains (LBDs) reveal endogenous glycine in the binding pocket, whereas ligand-binding assays show that glycine binds with nanomolar affinity; biochemical assays and structural analysis establish that glutamate is occluded from the binding cavity. Further analysis reveals ctenophore-specific features, such as an interdomain Arg-Glu salt bridge, present only in subunits that bind glycine, but also a conserved disulfide in loop 1 of the LBD that is found in all vertebrate NMDA but not AMPA or kainate receptors. We hypothesize that ctenophore iGluRs are related to an early ancestor of NMDA receptors, suggesting a common evolutionary path for ctenophores and bilaterian species, and suggest that future work should consider both glycine and glutamate as candidate neurotransmitters in ctenophore species. PMID:26460032

  12. Glycine activated ion channel subunits encoded by ctenophore glutamate receptor genes

    DOE PAGES

    Alberstein, Robert; Grey, Richard; Zimmet, Austin; ...

    2015-10-12

    Recent genome projects for ctenophores have revealed the presence of numerous ionotropic glutamate receptors (iGluRs) in Mnemiopsis leidyi and Pleurobrachia bachei, among our earliest metazoan ancestors. Sequence alignments and phylogenetic analysis show that these form a distinct clade from the well-characterized AMPA, kainate, and NMDA iGluR subtypes found in vertebrates. Although annotated as glutamate and kainate receptors, crystal structures of the ML032222a and PbiGluR3 ligand-binding domains (LBDs) reveal endogenous glycine in the binding pocket, whereas ligand-binding assays show that glycine binds with nanomolar affinity; biochemical assays and structural analysis establish that glutamate is occluded from the binding cavity. Further analysismore » reveals ctenophore-specific features, such as an interdomain Arg-Glu salt bridge, present only in subunits that bind glycine, but also a conserved disulfide in loop 1 of the LBD that is found in all vertebrate NMDA but not AMPA or kainate receptors. In this paper, we hypothesize that ctenophore iGluRs are related to an early ancestor of NMDA receptors, suggesting a common evolutionary path for ctenophores and bilaterian species, and finally suggest that future work should consider both glycine and glutamate as candidate neurotransmitters in ctenophore species.« less

  13. Glycine activated ion channel subunits encoded by ctenophore glutamate receptor genes

    SciTech Connect

    Alberstein, Robert; Grey, Richard; Zimmet, Austin; Simmons, David K.; Mayer, Mark L.

    2015-10-12

    Recent genome projects for ctenophores have revealed the presence of numerous ionotropic glutamate receptors (iGluRs) in Mnemiopsis leidyi and Pleurobrachia bachei, among our earliest metazoan ancestors. Sequence alignments and phylogenetic analysis show that these form a distinct clade from the well-characterized AMPA, kainate, and NMDA iGluR subtypes found in vertebrates. Although annotated as glutamate and kainate receptors, crystal structures of the ML032222a and PbiGluR3 ligand-binding domains (LBDs) reveal endogenous glycine in the binding pocket, whereas ligand-binding assays show that glycine binds with nanomolar affinity; biochemical assays and structural analysis establish that glutamate is occluded from the binding cavity. Further analysis reveals ctenophore-specific features, such as an interdomain Arg-Glu salt bridge, present only in subunits that bind glycine, but also a conserved disulfide in loop 1 of the LBD that is found in all vertebrate NMDA but not AMPA or kainate receptors. In this paper, we hypothesize that ctenophore iGluRs are related to an early ancestor of NMDA receptors, suggesting a common evolutionary path for ctenophores and bilaterian species, and finally suggest that future work should consider both glycine and glutamate as candidate neurotransmitters in ctenophore species.

  14. Glycine activated ion channel subunits encoded by ctenophore glutamate receptor genes.

    PubMed

    Alberstein, Robert; Grey, Richard; Zimmet, Austin; Simmons, David K; Mayer, Mark L

    2015-11-03

    Recent genome projects for ctenophores have revealed the presence of numerous ionotropic glutamate receptors (iGluRs) in Mnemiopsis leidyi and Pleurobrachia bachei, among our earliest metazoan ancestors. Sequence alignments and phylogenetic analysis show that these form a distinct clade from the well-characterized AMPA, kainate, and NMDA iGluR subtypes found in vertebrates. Although annotated as glutamate and kainate receptors, crystal structures of the ML032222a and PbiGluR3 ligand-binding domains (LBDs) reveal endogenous glycine in the binding pocket, whereas ligand-binding assays show that glycine binds with nanomolar affinity; biochemical assays and structural analysis establish that glutamate is occluded from the binding cavity. Further analysis reveals ctenophore-specific features, such as an interdomain Arg-Glu salt bridge, present only in subunits that bind glycine, but also a conserved disulfide in loop 1 of the LBD that is found in all vertebrate NMDA but not AMPA or kainate receptors. We hypothesize that ctenophore iGluRs are related to an early ancestor of NMDA receptors, suggesting a common evolutionary path for ctenophores and bilaterian species, and suggest that future work should consider both glycine and glutamate as candidate neurotransmitters in ctenophore species.

  15. Regional development of glutamate-N-methyl-D-aspartate receptor sites in asphyxiated newborn infants.

    PubMed

    Andersen, D L; Tannenberg, A E; Burke, C J; Dodd, P R

    1998-04-01

    The N-methyl-D-aspartate (NMDA) subclass of glutamate receptors was examined in newborn infants dying between 25 weeks' gestation and term, either from acute cerebral hypoxia, or from other noncerebral conditions incompatible with life. Frontal, occipital, temporal, and motor cortex tissue samples were obtained at autopsy (post mortem delay: median, 45.9 hr; range, 24-96 hr) and frozen for subsequent [3H]MK801 homogenate binding assays. Whereas no significant variation was observed in ligand affinity (KD), in all cases receptor density (BMAX) increased with gestational age, in occipital cortex (27 weeks, BMAX = 222 +/- 44 fmol x mg protein(-1); 39 weeks, 439 +/- 42 fmol x mg protein[-1]), but not in motor or temporal cortex. The gestational-age increase also occurred in control frontal cortex (27 weeks, 284 +/- 80; 39 weeks, 567 +/- 40 fmol x mg protein[-1]), but was significantly less marked in frontal cortex in hypoxia cases (27 weeks, 226 +/- 90; 39 weeks, 326 +/- 47 fmol x mg protein[-1]). In all cortical areas except temporal, the maximal response to glutamate did not vary across case groups. Hypoxia cases showed an increased response to glutamate enhancement selectively in temporal cortex. Binding site density did not correlate with degree of hypoxia as assessed pathologically, suggesting that receptor differences preceded the hypoxic episode. Regional differences in glutamate-NMDA receptor sites may underlie increased vulnerability to hypoxia at birth.

  16. The Role of Metabotropic Glutamate Receptors and Cortical Adaptation in Habituation of Odor-Guided Behavior

    ERIC Educational Resources Information Center

    Yadon, Carly A.; Wilson, Donald A.

    2005-01-01

    Decreases in behavioral investigation of novel stimuli over time may be mediated by a variety of factors including changes in attention, internal state, and motivation. Sensory cortical adaptation, a decrease in sensory cortical responsiveness over prolonged stimulation, may also play a role. In olfaction, metabotropic glutamate receptors on…

  17. Effect of chronic glutamate administration to pregnant rats during gestation on metabotropic glutamate receptors from mothers and full-term fetuses brain.

    PubMed

    León Navarro, D; Albasanz, J L; Iglesias, I; Ruiz, M A; Martín, M

    2005-03-01

    Chronic glutamate treatment during gestational period caused a significant decrease in total metabotropic glutamate receptors (mGluR) number. Similar results were observed on the steady-state level of mGlu(1) receptor detected by immunoblotting assays, suggesting that this is the main receptor subtype modulated by agonist exposure. Furthermore, no variations on mRNA coding mGlu(1) receptor were found, suggesting post-transcriptional modulation as a possible mechanism of the lost of receptor detected at the membrane surface. On the other hand, western-blotting to determine level of G(q/11) protein and phospholipase C beta(1) revealed a significant decrease of both proteins in mothers brain. This decrease was associated with significant variation in glutamate and DHPG-stimulated phospholipase C activity. No significant differences on mGluR transduction pathway components were observed in fetuses brain. These results suggest that glutamate intake during pregnancy causes a down-regulation of different proteins involved in glutamate response mediated by mGluR only in mothers brain without significantly affecting fetuses brain.

  18. Molecular Characteristics of Membrane Glutamate Receptor-Ionophore Interaction.

    DTIC Science & Technology

    1982-10-15

    accompanied by an increase in membrane permeability to sodium ions and to a lesser extent to potassium ions (Anwyl, 1977; Krnjevic, 1974). Clearly the issues...been examined in the last three years are: (1) Whether L-glutamic acid does activate a sodium ionophore in synaptic membranes from brain. Na+ fluxes...the presence of 10 pM kainic acid (I) or L-- glutamat ~e (I| ) was compared to the basal SCN"uptake (0O). (C) InfluJx of SCN" in the presence of 10 p H

  19. Effects of glutamate receptor activation on NG2-glia in the rat optic nerve

    PubMed Central

    Hamilton, Nicola; Hubbard, Paul S; Butt, Arthur M

    2009-01-01

    NG2-glia are a substantial population of cells in the central nervous system (CNS) that can be identified by their specific expression of the NG2 chondroitin sulphate (CSPG). NG2-glia can generate oligodendrocytes, but it is unlikely this is their only function; indeed, they may be multipotent neural stem cells. Moreover, NG2-glia are a highly reactive cell type and a major function is to help form the axon growth inhibitory glial scar in response to CNS injury. The factors that regulate these diverse behaviours of NG2-glia are not fully resolved, but NG2-glia express receptors to the neurotransmitter glutamate, which has known potent effects on other glia. Here, we have examined the actions of glutamate receptor activation on NG2-glia in the rat optic nerve, a typical CNS white matter tract that does not contain neuronal cell bodies. Glutamate induces an increase in [Ca2+]i in immuno-identified NG2-glia in situ and in vitro. In addition, we examined the effects of glutamate receptor activation in vivo by focal injection of the glutamate receptor agonist kainate into the optic nerve; saline was injected in controls. Changes in glial and axonal function were determined at 7 days post injection (dpi), by immunohistochemistry and electrophysiological measurement of the compound action potential (CAP). Injection of kainate resulted in a highly localized ‘injury response’ in NG2-glia, marked by dense labelling for NG2 at the lesion site, as compared to astrocytes, which displayed a more extensive reactive astrogliosis. Furthermore, injection of kainate resulted in an axonal conduction block. These glial and axonal changes were not observed following injection of saline vehicle. In addition, we provide evidence that endogenous glutamate induces calcium-dependent phosphorylation of extracellular signal-regulated kinases (ERK1/2), which may provide a potential mechanism by which glutamate-mediated changes in raised intracellular calcium could regulate the observed

  20. Glutamate Binding and Conformational Flexibility of Ligand-binding Domains Are Critical Early Determinants of Efficient Kainate Receptor Biogenesis

    PubMed Central

    Gill, Martin B.; Vivithanaporn, Pornpun; Swanson, Geoffrey T.

    2009-01-01

    Intracellular glutamate binding within the endoplasmic reticulum (ER) is thought to be necessary for plasma membrane expression of ionotropic glutamate receptors. Here we determined the importance of glutamate binding to folding and assembly of soluble ligand-binding domains (LBDs), as well as full-length receptors, by comparing the secretion of a soluble GluR6-S1S2 protein versus the plasma membrane localization of GluR6 kainate receptors following mutagenesis of the LBD. The mutations were designed to either eliminate glutamate binding, thereby trapping the bilobate LBD in an “open” conformation, or “lock” the LBD in a closed conformation with an engineered interdomain disulfide bridge. Analysis of plasma membrane localization, medium secretion of soluble LBD proteins, and measures of folding efficiency suggested that loss of glutamate binding affinity significantly impacted subunit protein folding and assembly. In contrast, receptors with conformationally restricted LBDs also exhibited decreased PM expression and altered oligomeric receptor assembly but did not exhibit any deficits in subunit folding. Secretion of the closed LBD protein was enhanced compared with wild-type GluR6-S1S2. Our results suggest that glutamate acts as a chaperone molecule for appropriate folding of nascent receptors and that relaxation of LBDs from fully closed states during oligomerization represents a critical transition that necessarily engages other determinants within receptor dimers. Glutamate receptor LBDs therefore must access multiple conformations for efficient biogenesis. PMID:19342380

  1. Metabotropic glutamate receptors are required for the induction of long-term potentiation

    NASA Technical Reports Server (NTRS)

    Zheng, F.; Gallagher, J. P.

    1992-01-01

    Recent observations have led to the suggestion that the metabotropic glutamate receptor may play a role in the induction or maintenance of long-term potentiation (LTP). However, experimental evidence supporting a role for this receptor in the induction of LTP is still inconclusive and controversial. Here we report that, in rat dorsolateral septal nucleus (DLSN) neurons, which have the highest density of metabotropic receptors and show functional responses, the induction of LTP is not blocked by the NMDA receptor antagonist 2-amino-5-phosphonovalerate, but is blocked by two putative metabotropic glutamate receptor antagonists, L-2-amino-3-phosphonopropionic acid and L-2-amino-4-phosphonobutyrate. Furthermore, superfusion of (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid, a selective metabotropic glutamate agonist, resulted in a long-lasting potentiation of synaptic transmission similar to that induced by tetanic stimuli. Our results demonstrated that activation of postsynaptic metabotropic receptors is both necessary and sufficient for the induction of LTP in the DLSN, and we suggest that such a mechanism may be important at other CNS synapses.

  2. Pre-synaptic GABA receptors inhibit glutamate release through GIRK channels in rat cerebral cortex.

    PubMed

    Ladera, Carolina; del Carmen Godino, María; José Cabañero, María; Torres, Magdalena; Watanabe, Masahiko; Luján, Rafael; Sánchez-Prieto, José

    2008-12-01

    Neuronal G protein-gated inwardly rectifying potassium (GIRK) channels mediate the slow inhibitory effects of many neurotransmitters post-synaptically. However, no evidence exists that supports that GIRK channels play any role in the inhibition of glutamate release by GABA(B) receptors. In this study, we show for the first time that GABA(B) receptors operate through two mechanisms in nerve terminals from the cerebral cortex. As shown previously, GABA(B) receptors reduces glutamate release and the Ca(2+) influx mediated by N-type Ca(2+) channels in a mode insensitive to the GIRK channel blocker tertiapin-Q and consistent with direct inhibition of this voltage-gated Ca(2+) channel. However, by means of weak stimulation protocols, we reveal that GABA(B) receptors also reduce glutamate release mediated by P/Q-type Ca(2+) channels, and that these responses are reversed by the GIRK channel blocker tertiapin-Q. Consistent with the functional interaction between GABA(B) receptors and GIRK channels at nerve terminals we demonstrate by immunogold electron immunohistochemistry that pre-synaptic boutons of asymmetric synapses co-express GABA(B) receptors and GIRK channels, thus suggesting that the functional interaction of these two proteins, found at the post-synaptic level, also occurs at glutamatergic nerve terminals.

  3. [Studying specific effects of nootropic drugs on glutamate receptors in the rat brain].

    PubMed

    Firstova, Iu Iu; Vasil'eva, E V; Kovalev, G I

    2011-01-01

    The influence of nootropic drugs of different groups (piracetam, phenotropil, nooglutil, noopept, semax, meclofenoxate, pantocalcine, and dimebon) on the binding of the corresponding ligands to AMPA, NMDA, and mGlu receptors of rat brain has been studied by the method of radio-ligand binding in vitro. It is established that nooglutil exhibits pharmacologically significant competition with a selective agonist of AMPA receptors ([G-3H]Ro 48-8587) for the receptor binding sites (with IC50 = 6.4 +/- 0.2 microM), while the competition of noopept for these receptor binding sites was lower by an order of magnitude (IC50 = 80 +/- 5.6 microM). The heptapeptide drug semax was moderately competitive with [G-3H]LY 354740 for mGlu receptor sites (IC50 = 33 +/- 2.4 microM). Dimebon moderately influenced the specific binding of the ligand of NMDA receptor channel ([G-3H]MK-801) at IC50 = 59 +/- 3.6 microM. Nootropic drugs of the pyrrolidone group (piracetam, phenotropil) as well as meclofenoxate, pantocalcine (pantogam) in a broad rage of concentrations (10(-4)-10(-10) M) did not affect the binding of the corresponding ligands to glutamate receptors (IC50 100 pM). Thus, the direct neurochemical investigation was used for the first time to qualitatively characterize the specific binding sites for nooglutil and (to a lower extent) noopept on AMPA receptors, for semax on metabotropic glutamate receptors, and for dimebon on the channel region of NMDA receptors. The results are indicative of a selective action of some nootropes on the glutamate family.

  4. The SOL-2/Neto auxiliary protein modulates the function of AMPA-subtype ionotropic glutamate receptors.

    PubMed

    Wang, Rui; Mellem, Jerry E; Jensen, Michael; Brockie, Penelope J; Walker, Craig S; Hoerndli, Frédéric J; Hauth, Linda; Madsen, David M; Maricq, Andres V

    2012-09-06

    The neurotransmitter glutamate mediates excitatory synaptic transmission by gating ionotropic glutamate receptors (iGluRs). AMPA receptors (AMPARs), a subtype of iGluR, are strongly implicated in synaptic plasticity, learning, and memory. We previously discovered two classes of AMPAR auxiliary proteins in C. elegans that modify receptor kinetics and thus change synaptic transmission. Here, we have identified another auxiliary protein, SOL-2, a CUB-domain protein that associates with both the related auxiliary subunit SOL-1 and with the GLR-1 AMPAR. In sol-2 mutants, behaviors dependent on glutamatergic transmission are disrupted, GLR-1-mediated currents are diminished, and GLR-1 desensitization and pharmacology are modified. Remarkably, a secreted variant of SOL-1 delivered in trans can rescue sol-1 mutants, and this rescue depends on in cis expression of SOL-2. Finally, we demonstrate that SOL-1 and SOL-2 have an ongoing role in the adult nervous system to control AMPAR-mediated currents.

  5. Disruption of glutamate receptors at Shank-postsynaptic platform in Alzheimer's disease

    PubMed Central

    Gong, Yuesong; Lippa, Carol F.; Zhu, Jinghua; Lin, Qishan; Rosso, Andrea L.

    2009-01-01

    Synaptic loss underlies the memory deficit of Alzheimer's disease (AD). The molecular mechanism is elusive; however, excitatory synapses organized by the postsynaptic density (PSD) have been used as targets for AD treatment. To identify pathological entities at the synapse in AD, synaptic proteins were screened by quantitative proteomic profiling. The critical proteins were then selected for immunoblot analysis. The glutamate receptors N-methyl-d-aspartate (NMDA) receptor 1 and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor 2 (GluR2) were substantially lost; specifically, the loss of GluR2 was up to 40% at PSD in AD. Shank proteins, the organizers of these glutamate receptors at excitatory synapses, were dramatically altered in AD. The level of Shank2 was increased, whereas the protein level of Shank3 was decreased. Further, the Shank3 protein was modified by ubiquitin, indicating that abnormal activity of the ubiquitin–proteasome system may lead to Shank3 degradation in AD. Our findings suggest that disruption of glutamate receptors at the Shank-postsynaptic platform could contribute to destruction of the PSD which underlies the synaptic dysfunction and loss in AD. PMID:19635471

  6. X-ray structure, symmetry and mechanism of an AMPA-subtype glutamate receptor

    SciTech Connect

    Sobolevsky, Alexander I.; Rosconi, Michael P.; Gouaux, Eric

    2010-02-02

    Ionotropic glutamate receptors mediate most excitatory neurotransmission in the central nervous system and function by opening a transmembrane ion channel upon binding of glutamate. Despite their crucial role in neurobiology, the architecture and atomic structure of an intact ionotropic glutamate receptor are unknown. Here we report the crystal structure of the {alpha}-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)-sensitive, homotetrameric, rat GluA2 receptor at 3.6 {angstrom} resolution in complex with a competitive antagonist. The receptor harbours an overall axis of two-fold symmetry with the extracellular domains organized as pairs of local dimers and with the ion channel domain exhibiting four-fold symmetry. A symmetry mismatch between the extracellular and ion channel domains is mediated by two pairs of conformationally distinct subunits, A/C and B/D. Therefore, the stereochemical manner in which the A/C subunits are coupled to the ion channel gate is different from the B/D subunits. Guided by the GluA2 structure and site-directed cysteine mutagenesis, we suggest that GluN1 and GluN2A NMDA (N-methyl-D-aspartate) receptors have a similar architecture, with subunits arranged in a 1-2-1-2 pattern. We exploit the GluA2 structure to develop mechanisms of ion channel activation, desensitization and inhibition by non-competitive antagonists and pore blockers.

  7. Ionotropic glutamate receptors in the external lateral parabrachial nucleus participate in processing cardiac sympathoexcitatory reflexes.

    PubMed

    Fu, Liang-Wu; Guo, Zhi-Ling; Longhurst, John C

    2012-04-01

    Stimulation of cardiac sympathetic afferents during myocardial ischemia with metabolites such as bradykinin (BK) evokes sympathoexcitatory reflex responses and activates neurons in the external lateral parabrachial nucleus (elPBN). The present study tested the hypothesis that this region in the pons processes sympathoexcitatory cardiac reflexes through an ionotropic glutamate receptor mechanism. The ischemic metabolite BK (0.1-1 μg) was injected into the pericardial space of anesthetized and bilaterally vagotomized or intact cats. Hemodynamic and renal sympathetic nerve activity (RSNA) responses to repeated administration of BK before and after unilateral 50-nl microinjections of kynurenic acid (Kyn; 25 mM), 2-amino-5-phosphonopentanoic acid (AP5; 25 mM), and 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzol(F)quinoxaline (NBQX; 10 mM) into the elPBN were recorded. Intrapericardial BK evoked significant increases in mean arterial pressure (MAP) and RSNA in seven vagotomized cats. After blockade of glutamate receptors with the nonselective glutamate receptor antagonist Kyn, the BK-evoked reflex increases in MAP (50 ± 6 vs. 29 ± 2 mmHg) and RSNA (59 ± 8.6 vs. 29 ± 4.7%, before vs. after) were significantly attenuated. The BK-evoked responses returned to pre-Kyn levels 85 min after the application of Kyn. Similarly, BK-evoked reflex responses were reversibly attenuated by blockade of glutamate N-methyl-d-aspartate (NMDA) receptors with AP5 (n = 5) and α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors with NBQX (n = 5). In contrast, we observed that the repetitive administration of BK evoked consistent reflex responses including MAP and RSNA before and after microinjection of 50 nl of the artificial cerebrospinal fluid vehicle into the elPBN in five animals. Microinjection of glutamate receptor antagonists into regions outside the elPBN did not alter BK-induced reflex responses. Microinjection of Kyn into the elPBN reversibly attenuated BK

  8. Astrocytic glutamate uptake is slow and does not limit neuronal NMDA receptor activation in the neonatal neocortex.

    PubMed

    Hanson, Elizabeth; Armbruster, Moritz; Cantu, David; Andresen, Lauren; Taylor, Amaro; Danbolt, Niels Christian; Dulla, Chris G

    2015-10-01

    Glutamate uptake by astrocytes controls the time course of glutamate in the extracellular space and affects neurotransmission, synaptogenesis, and circuit development. Astrocytic glutamate uptake has been shown to undergo post-natal maturation in the hippocampus, but has been largely unexplored in other brain regions. Notably, glutamate uptake has never been examined in the developing neocortex. In these studies, we investigated the development of astrocytic glutamate transport, intrinsic membrane properties, and control of neuronal NMDA receptor activation in the developing neocortex. Using astrocytic and neuronal electrophysiology, immunofluorescence, and Western blot analysis we show that: (1) glutamate uptake in the neonatal neocortex is slow relative to neonatal hippocampus; (2) astrocytes in the neonatal neocortex undergo a significant maturation of intrinsic membrane properties; (3) slow glutamate uptake is accompanied by lower expression of both GLT-1 and GLAST; (4) glutamate uptake is less dependent on GLT-1 in neonatal neocortex than in neonatal hippocampus; and (5) the slow glutamate uptake we report in the neonatal neocortex corresponds to minimal astrocytic control of neuronal NMDA receptor activation. Taken together, our results clearly show fundamental differences between astrocytic maturation in the developing neocortex and hippocampus, and corresponding changes in how astrocytes control glutamate signaling.

  9. Ionotropic glutamate receptors mediate OFF responses in light-adapted ON bipolar cells

    PubMed Central

    Pang, Ji-Jie; Gao, Fan; Wu, Samuel M.

    2013-01-01

    Previous studies have suggested that photoreceptor synaptic inputs to depolarizing bipolar cells (DBCs or ON bipolar cells) are mediated by mGluR6 receptors and those to hyperpolarizing bipolar cells (HBCs or OFF bipolar cells) are mediated by AMPA/kainate receptors. Here we show that in addition to mGluR6 receptors which mediate the sign-inverting, depolarizing light responses, subpopulations of cone-dominated and rod/cone mixed DBCs use GluR4 AMPA receptors to generate a transient sign-preserving OFF response under light adapted conditions. These AMPA receptors are located at the basal junctions postsynaptic to rods and they are silent under dark-adapted conditions, as tonic glutamate release in darkness desensitizes these receptors. Light adaptation enhances rod-cone coupling and thus allows cone photocurrents with an abrupt OFF depolarization to enter the rods. The abrupt rod depolarization triggers glutamate activation of unoccupied AMPA receptors, resulting in a transient OFF response in DBCs. It has been widely accepted that the DNQX-sensitive, OFF transient responses in retinal amacrine cells and ganglion cells are mediated exclusively by HBCs. Our results suggests that this view needs revision as AMPA receptors in subpopulations of DBCs are likely to significantly contribute to the DNQX-sensitive OFF transient responses in light-adapted third- and higher-order visual neurons. PMID:22842089

  10. LTD expression is independent of glutamate receptor subtype.

    PubMed

    Granger, Adam J; Nicoll, Roger A

    2014-01-01

    Long-term depression (LTD) is a form of synaptic plasticity that plays a major role in the activity-dependent reshaping of synaptic transmission. LTD is expressed as a decrease in synaptic AMPA receptor number, though the exact mechanism remains controversial. Several lines of evidence have suggested necessary roles for both the GluA1 and GluA2 subunits, and specifically certain interactions with their cytoplasmic tails. However, it is unclear if either GluA1 or GluA2 are absolutely required for LTD. We tested this hypothesis using constitutive knock-outs and single-cell molecular replacement of AMPA receptor subunits in mouse hippocampus. We found that neither GluA1 or GluA2 are required for normal expression of LTD, and indeed a normal decrease in synaptic transmission was observed in cells in which all endogenous AMPA receptors have been replaced by kainate receptors. Thus, LTD does not require removal of specific AMPA receptor subunits, but likely involves a more general modification of the synapse and its ability to anchor a broad range of receptor proteins.

  11. Inhibition of a slow synaptic response by a metabotropic glutamate receptor antagonist in hippocampal CA3 pyramidal cells.

    PubMed

    Gerber, U; Lüthi, A; Gähwiler, B H

    1993-11-22

    The effects of a novel antagonist of metabotropic glutamate receptors were investigated in CA3 pyramidal cells in hippocampal slice cultures of the rat. Earlier experiments showed that selective activation of metabotropic glutamate receptors with low concentrations of an agonist, 1S, 3R-1-amino-cyclopentane-1,3-dicarboxylic acid (ACPD), induced an inward current associated with a decrease in membrane conductance and inhibition of the slow calcium-dependent potassium current. These responses were strongly and reversibly reduced by the antagonist, (RS)-alpha-methyl-4-carboxyphenylglycine (MCPG, 0.5-1 mM). In the presence of antagonists of ionotropic glutamate receptors, stimulation of the afferent mossy fibres evoked postsynaptic responses in CA3 pyramidal cells which paralleled those observed with exogenously applied metabotropic glutamate receptor agonists, i.e. a slow inward current and a reduction of calcium-dependent potassium current. Both responses were greatly reduced by bath-applied MCPG (1 mM). These results show that MCPG acts as an effective antagonist at metabotropic glutamate receptors coupled to potassium conductances in the hippocampus. Furthermore, they confirm that glutamate release from presynaptic terminals can modulate postsynaptic properties by activation of metabotropic glutamate receptors.

  12. Benzodiazepine receptor inverse agonist-induced kindling of rats alters learning and glutamate binding.

    PubMed

    Rössler, A S; Schröder, H; Dodd, R H; Chapouthier, G; Grecksch, G

    2000-09-01

    Kindling, recognized as a model of epilepsy, can be obtained by applications of repeated nonconvulsive stimulations that finally lead to generalized seizures. Epileptics often show cognitive impairments. The present work analyzed the learning performance of male Wistar rats kindled with a convulsant inverse agonist of the GABA(A)-benzodiazepine receptor complex, methyl beta-carboline-3-carboxylate (beta-CCM). This compound is also known to have an action on learning processes. It was thus interesting to verify if beta-CCM kindling had the same impairing action on learning as other kindling agents, such as pentylenetetrazol (PTZ). A two-way active-avoidance shuttle-box learning task was chosen, because a deficit was found after PTZ kindling in this learning model. On the other hand, hippocampal glutamate binding, has previously been shown to be modified by both seizures and learning. Thus, the level of glutamate binding was also measured in the present study. Results showed that fully kindled rats had poorer learning performance after the third day of test than controls or not fully kindled animals. L-[3H] glutamate binding to hippocampal membrane fractions of the fully kindled animals was significantly higher when compared with controls, whereas L-[3H] glutamate binding of not fully kindled subjects did not differ from that of controls. Neuronal plasticity changes are a possible explanation for the correlation between kindling, learning deficits, and increased glutamate binding.

  13. A Molecular Determinant of Subtype-Specific Desensitization in Ionotropic Glutamate Receptors

    PubMed Central

    Alsaloum, Matthew; Kazi, Rashek; Gan, Quan; Amin, Johansen

    2016-01-01

    AMPA and NMDA receptors are glutamate-gated ion channels that mediate fast excitatory synaptic transmission throughout the nervous system. In the continual presence of glutamate, AMPA and NMDA receptors containing the GluN2A or GluN2B subunit enter into a nonconducting, desensitized state that can impact synaptic responses and glutamate-mediated excitotoxicity. The process of desensitization is dramatically different between subtypes, but the basis for these differences is unknown. We generated an extensive sequence alignment of ionotropic glutamate receptors (iGluRs) from diverse animal phyla and identified a highly conserved motif, which we termed the “hydrophobic box,” located at the extracellular interface of transmembrane helices. A single position in the hydrophobic box differed between mammalian AMPA and NMDA receptors. Surprisingly, we find that an NMDAR-to-AMPAR exchange mutation at this position in the rat GluN2A or GluN2B subunit had a dramatic and highly specific effect on NMDAR desensitization, making it AMPAR-like. In contrast, a reverse exchange mutation in AMPARs had minimal effects on desensitization. These experiments highlight differences in desensitization between iGluR subtypes and the highly specific contribution of the GluN2 subunit to this process. SIGNIFICANCE STATEMENT Rapid communication between cells in the nervous system depends on ion channels that are directly activated by neurotransmitter molecules. Here, we studied ionotropic glutamate receptors (iGluRs), which are ion channels activated by the neurotransmitter glutamate. By comparing the sequences of a vast number of iGluR proteins from diverse animal species, assisted by available structural information, we identified a highly conserved motif. We showed that a single amino acid difference in this motif between mammalian iGluR subtypes has dramatic effects on receptor function. These results have implications in both the evolution of synaptic function, as well as the role of i

  14. The Metabotropic Glutamate Receptor mGlu7 Activates Phospholipase C, Translocates Munc-13-1 Protein, and Potentiates Glutamate Release at Cerebrocortical Nerve Terminals*

    PubMed Central

    Martín, Ricardo; Durroux, Thierry; Ciruela, Francisco; Torres, Magdalena; Pin, Jean-Philippe; Sánchez-Prieto, José

    2010-01-01

    At synaptic boutons, metabotropic glutamate receptor 7 (mGlu7 receptor) serves as an autoreceptor, inhibiting glutamate release. In this response, mGlu7 receptor triggers pertussis toxin-sensitive G protein activation, reducing presynaptic Ca2+ influx and the subsequent depolarization evoked release. Here we report that receptor coupling to signaling pathways that potentiate release can be seen following prolonged exposure of nerve terminals to the agonist l-(+)-phosphonobutyrate, l-AP4. This novel mGlu7 receptor response involves an increase in the release induced by the Ca2+ ionophore ionomycin, suggesting a mechanism that is independent of Ca2+ channel activity, but dependent on the downstream exocytotic release machinery. The mGlu7 receptor-mediated potentiation resists exposure to pertussis toxin, but is dependent on phospholipase C, and increased phosphatidylinositol (4,5)-bisphosphate hydrolysis. Furthermore, the potentiation of release does not depend on protein kinase C, although it is blocked by the diacylglycerol-binding site antagonist calphostin C. We also found that activation of mGlu7 receptors translocate the active zone protein essential for synaptic vesicle priming, munc13-1, from soluble to particulate fractions. We propose that the mGlu7 receptor can facilitate or inhibit glutamate release through multiple pathways, thereby exerting homeostatic control of presynaptic function. PMID:20375012

  15. Presynaptic Inhibition of Glutamate Transmission by Alpha-2 Receptors in the VTA

    PubMed Central

    Jiménez-Rivera, Carlos A.; Figueroa, Johnny; Vázquez, Rafael; Vélez, María; Schwarz, David; Velásquez-Martinez, María C.; Arencibia-Albite, Francisco

    2013-01-01

    The ventral tegmental area (VTA) forms part of the mesocorticolimbic system and plays a pivotal role in reward and reinforcing actions of drugs of abuse. Glutamate transmission within the VTA controls important aspects of goal-directed behavior and motivation. Noradrenergic receptors also present in the VTA have important functions in the modulation of neuronal activity. Here we studied the effects of alpha-2 noradrenergic receptor activation in the alteration of glutamate neurotransmission in VTA dopaminergic neurons from male Sprague-Dawley rats. We used whole cell patch clamp recordings from putative VTA dopaminergic neurons and measured excitatory postsynaptic currents. Clonidine (40 μM) and UK 13,408 (40 μM), both alpha-2 receptor agonists, reduced (~ 40%) the amplitude of glutamate-induced excitatory postsynaptic currents. After clonidine administration, there was a dose-dependent reduction over the concentration range of 15–40 μM. Using yohimbine (20μM) and two other alpha-2 adrenergic receptor antagonists, idaxozan (40 μM) and atipemazole (20μM), we demonstrated that the inhibitory action is specifically mediated by alpha-2 receptors. Moreover, by inhibiting protein kinases with H-7 (75 μM), Rp-adenosine 3′,5′-cyclic (11 μM) and chelerythrine (1 μM) it was shown that the clonidine-induced inhibition seems to involve a selective activation of the protein kinase C intracellular pathway. An increased paired-pulse ratios and changes in spontaneous and miniature excitatory postsynaptic currents frequencies but not amplitudes indicated that the alpha-2 agonist’s effect was presynaptically mediated. It is suggested that the suppression of glutamate excitatory inputs onto VTA dopaminergic neurons might be relevant in the regulation of reward and drug seeking behaviors. PMID:22564071

  16. An interaction of oxytocin receptors with metabotropic glutamate receptors in hypothalamic astrocytes.

    PubMed

    Kuo, J; Hariri, O R; Micevych, P

    2009-12-01

    Hypothalamic astrocytes play a critical role in the regulation and support of many different neuroendocrine events, and are affected by oestradiol. Both nuclear and membrane oestrogen receptors (ERs) are expressed in astrocytes. Upon oestradiol activation, membrane-associated ER signals through the type 1a metabotropic glutamate receptor (mGluR1a) to induce an increase of free cytoplasmic calcium concentration ([Ca(2+)](i)). Because the expression of oxytocin receptors (OTRs) is modulated by oestradiol, we tested whether oestradiol also influences oxytocin signalling. Oxytocin at 1, 10, and 100 nm induced a [Ca(2+)](i) flux measured as a change in relative fluorescence [DeltaF Ca(2+) = 330 +/- 17 relative fluorescent units (RFU), DeltaF Ca(2+) = 331 +/- 22 RFU, and DeltaF Ca(2+) = 347 +/- 13 RFU, respectively] in primary cultures of female post-pubertal hypothalamic astrocytes. Interestingly, OTRs interacted with mGluRs. The mGluR1a antagonist, LY 367385 (20 nm), blocked the oxytocin (1 nm)-induced [Ca(2+)](i) flux (DeltaF Ca(2+) = 344 +/- 19 versus 127 +/- 11 RFU, P < 0.001). Conversely, the mGluR1a receptor agonist, (RS)-3,5-dihydroxyphenyl-glycine (100 nm), increased the oxytocin (1 nm)-induced [Ca(2+)](i) response (DeltaF Ca(2+) = 670 +/- 31 RFU) compared to either compound alone (P < 0.001). Because both oxytocin and oestradiol rapidly signal through the mGluR1a, we treated hypothalamic astrocytes sequentially with oxytocin and oestradiol to determine whether stimulation with one hormone affected the subsequent [Ca(2+)](i) response to the second hormone. Oestradiol treatment did not change the subsequent [Ca(2+)](i) flux to oxytocin (P > 0.05) and previous oxytocin exposure did not affect the [Ca(2+)](i) response to oestradiol (P > 0.05). Furthermore, simultaneous oestradiol and oxytocin stimulation failed to yield a synergistic [Ca(2+)](i) response. These results suggest that the OTR signals through the mGluR1a to release Ca(2+) from intracellular stores and

  17. Mechanism of partial agonism in AMPA-type glutamate receptors

    PubMed Central

    Salazar, Hector; Eibl, Clarissa; Chebli, Miriam; Plested, Andrew

    2017-01-01

    Neurotransmitters trigger synaptic currents by activating ligand-gated ion channel receptors. Whereas most neurotransmitters are efficacious agonists, molecules that activate receptors more weakly—partial agonists—also exist. Whether these partial agonists have weak activity because they stabilize less active forms, sustain active states for a lesser fraction of the time or both, remains an open question. Here we describe the crystal structure of an α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptor (AMPAR) ligand binding domain (LBD) tetramer in complex with the partial agonist 5-fluorowillardiine (FW). We validate this structure, and others of different geometry, using engineered intersubunit bridges. We establish an inverse relation between the efficacy of an agonist and its promiscuity to drive the LBD layer into different conformations. These results suggest that partial agonists of the AMPAR are weak activators of the receptor because they stabilize multiple non-conducting conformations, indicating that agonism is a function of both the space and time domains. PMID:28211453

  18. Glutamate Stimulates Local Protein Synthesis in the Axons of Rat Cortical Neurons by Activating α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid (AMPA) Receptors and Metabotropic Glutamate Receptors*

    PubMed Central

    Hsu, Wei-Lun; Chung, Hui-Wen; Wu, Chih-Yueh; Wu, Huei-Ing; Lee, Yu-Tao; Chen, En-Chan; Fang, Weilun; Chang, Yen-Chung

    2015-01-01

    Glutamate is the principal excitatory neurotransmitter in the mammalian CNS. By analyzing the metabolic incorporation of azidohomoalanine, a methionine analogue, in newly synthesized proteins, we find that glutamate treatments up-regulate protein translation not only in intact rat cortical neurons in culture but also in the axons emitting from cortical neurons before making synapses with target cells. The process by which glutamate stimulates local translation in axons begins with the binding of glutamate to the ionotropic AMPA receptors and metabotropic glutamate receptor 1 and members of group 2 metabotropic glutamate receptors on the plasma membrane. Subsequently, the activated mammalian target of rapamycin (mTOR) signaling pathway and the rise in Ca2+, resulting from Ca2+ influxes through calcium-permeable AMPA receptors, voltage-gated Ca2+ channels, and transient receptor potential canonical channels, in axons stimulate the local translation machinery. For comparison, the enhancement effects of brain-derived neurotrophic factor (BDNF) on the local protein synthesis in cortical axons were also studied. The results indicate that Ca2+ influxes via transient receptor potential canonical channels and activated the mTOR pathway in axons also mediate BDNF stimulation to local protein synthesis. However, glutamate- and BDNF-induced enhancements of translation in axons exhibit different kinetics. Moreover, Ca2+ and mTOR signaling appear to play roles carrying different weights, respectively, in transducing glutamate- and BDNF-induced enhancements of axonal translation. Thus, our results indicate that exposure to transient increases of glutamate and more lasting increases of BDNF would stimulate local protein synthesis in migrating axons en route to their targets in the developing brain. PMID:26134564

  19. Effects of AMPARs trafficking and glutamate-receptors binding probability on stochastic variability of EPSC.

    PubMed

    Ventriglia, Francesco; Di Maio, Vito

    2013-06-01

    Mathematical models of the excitatory synapse are providing valuable information about the synaptic response. The effects of several synaptic components on EPSC variability have been tested by computer simulation. Our model, based on Brownian diffusion of glutamate in the synaptic cleft, is basically the same we have used in previous papers but parameters have been upgraded according to the new experimental findings. The presence of filaments into the synaptic cleft and the number and the ratio of AMPA and NMDA receptors have been the main parameters upgraded. A different way of computing the binding probability of glutamate molecules to receptors by means of geometrical considerations has been also used. The obtained results were more precise and they suggested that the new elements can play a significant role in the stochastic variability of the synaptic response. Nevertheless, new problems arise concerning the value of the lower limit of the binding probability.

  20. Glutamate receptor-like channels in plants: a role as amino acid sensors in plant defence?

    PubMed Central

    Roberts, Michael R.

    2014-01-01

    Plant glutamate receptor-like genes (GLRs) are homologous to the genes for mammalian ionotropic glutamate receptors (iGluRs), after which they were named, but in the 16 years since their existence was first revealed, progress in elucidating their biological role has been disappointingly slow. Recently, however, studies from a number of laboratories focusing on the model plant species Arabidopsis thaliana (L.) have thrown new light on the functional properties of some members of the GLR gene family. One important finding has been that plant GLR receptors have a much broader ligand specificity than their mammalian iGluR counterparts, with evidence that some individual GLR receptors can be gated by as many as seven amino acids. These results, together with the ubiquity of their expression throughout the plant, open up the possibility that GLR receptors could have a pervasive role in plants as non-specific amino acid sensors in diverse biological processes. Addressing what one of these roles could be, recent studies examining the wound response and disease susceptibility in GLR knockout mutants have provided evidence that some members of clade 3 of the GLR gene family encode important components of the plant's defence response. Ways in which this family of amino acid receptors might contribute to the plant's ability to respond to an attack from pests and pathogens are discussed. PMID:24991414

  1. Receptor regulation of the glutamate, GABA and taurine high-affinity uptake into astrocytes in primary culture.

    PubMed

    Hansson, E; Rönnbäck, L

    1991-05-10

    From experiments using dissociated primary astroglial cultures from newborn rat cerebral cortex, the stimulation of monoamine receptors (alpha, beta and 5HT) was shown to affect the high-affinity uptake kinetics of glutamate, GABA and taurine. In the presence of the alpha 1 agonist phenylephrine, there was an increased uptake (Vmax) of glutamate, while beta adrenoceptor activation slightly inhibited the glutamate uptake and stimulated the GABA and taurine uptakes. 5HT2 receptor stimulation caused a slight inhibition of the taurine uptake. The uptake rate of GABA was not affected by 5HT, alpha 1 or alpha 2 receptor agonists and the glutamate uptake was not affected by 5HT or alpha 2 receptor agonists. Nor was the taurine uptake affected by alpha 1 or alpha 2 receptor agonists. The active uptake of aspartate was unaffected by the presence of any of the monoamine receptor agonists used in this study. When the mechanisms behind these effects were studied, the GABA uptake seemed to be mediated via the G protein-adenylate cyclase complex in the receptor domain. Moreover, the K+ channels seemed to be involved. The taurine uptake, however, did not seem to be regulated by the same mechanism. It seems more probable that there is a direct interaction between the receptor and carrier of taurine at the membrane level. The mechanism underlying the receptor-regulated glutamate uptake is at present unclear, although it does not seem to involve protein kinase C.

  2. Constitutive internalization and recycling of metabotropic glutamate receptor 5 (mGluR5).

    PubMed

    Trivedi, Rishi Raj; Bhattacharyya, Samarjit

    2012-10-12

    Ligand-dependent and ligand-independent endocytic trafficking of G-protein coupled receptors (GPCRs) is critical for accurate receptor-mediated signaling and its regulation. Metabotropic glutamate receptor 5 (mGluR5) is a GPCR that plays a crucial role in circuit formation in the brain and also in various forms of synaptic plasticity including learning and memory. Outside the central nervous system this receptor also plays very important role in various other non-neuronal cells like heart cells, skin cells, hepatocytes, etc. Although the ligand-mediated endocytosis of mGluR5 has been studied in some detail, ligand-independent/constitutive endocytosis of the receptor has not been properly studied. Here, we have investigated the constitutive endocytosis of mGluR5 and also the sub-cellular fate of the receptor subsequent to internalization. We show here that mGluR5 undergoes constitutive internalization in HEK293 cells. Following endocytosis, the receptor enters the recycling compartment and no localization of the receptor was observed in the lysosome. In addition, we also report here that most of the receptors recycle to the cell surface subsequent to constitutive internalization. Thus, our data demonstrate that mGluR5 receptors internalize without the application of ligand and the internalized receptors recycle back to the cell surface following constitutive endocytosis.

  3. Metabotropic glutamate receptor 5 couples cellular prion protein to intracellular signalling in Alzheimer’s disease

    PubMed Central

    Haas, Laura T.; Salazar, Santiago V.; Kostylev, Mikhail A.; Um, Ji Won; Kaufman, Adam C.

    2016-01-01

    Alzheimer’s disease-related phenotypes in mice can be rescued by blockade of either cellular prion protein or metabotropic glutamate receptor 5. We sought genetic and biochemical evidence that these proteins function cooperatively as an obligate complex in the brain. We show that cellular prion protein associates via transmembrane metabotropic glutamate receptor 5 with the intracellular protein mediators Homer1b/c, calcium/calmodulin-dependent protein kinase II, and the Alzheimer’s disease risk gene product protein tyrosine kinase 2 beta. Coupling of cellular prion protein to these intracellular proteins is modified by soluble amyloid-β oligomers, by mouse brain Alzheimer’s disease transgenes or by human Alzheimer’s disease pathology. Amyloid-β oligomer-triggered phosphorylation of intracellular protein mediators and impairment of synaptic plasticity in vitro requires Prnp–Grm5 genetic interaction, being absent in transheterozygous loss-of-function, but present in either single heterozygote. Importantly, genetic coupling between Prnp and Grm5 is also responsible for signalling, for survival and for synapse loss in Alzheimer’s disease transgenic model mice. Thus, the interaction between metabotropic glutamate receptor 5 and cellular prion protein has a central role in Alzheimer’s disease pathogenesis, and the complex is a potential target for disease-modifying intervention. PMID:26667279

  4. Structure, Dynamics, and Allosteric Potential of Ionotropic Glutamate Receptor N-Terminal Domains

    PubMed Central

    Krieger, James; Bahar, Ivet; Greger, Ingo H.

    2015-01-01

    Ionotropic glutamate receptors (iGluRs) are tetrameric cation channels that mediate synaptic transmission and plasticity. They have a unique modular architecture with four domains: the intracellular C-terminal domain (CTD) that is involved in synaptic targeting, the transmembrane domain (TMD) that forms the ion channel, the membrane-proximal ligand-binding domain (LBD) that binds agonists such as L-glutamate, and the distal N-terminal domain (NTD), whose function is the least clear. The extracellular portion, comprised of the LBD and NTD, is loosely arranged, mediating complex allosteric regulation and providing a rich target for drug development. Here, we briefly review recent work on iGluR NTD structure and dynamics, and further explore the allosteric potential for the NTD in AMPA-type iGluRs using coarse-grained simulations. We also investigate mechanisms underlying the established NTD allostery in NMDA-type iGluRs, as well as the fold-related metabotropic glutamate and GABAB receptors. We show that the clamshell motions intrinsically favored by the NTD bilobate fold are coupled to dimeric and higher-order rearrangements that impact the iGluR LBD and ultimately the TMD. Finally, we explore the dynamics of intact iGluRs and describe how it might affect receptor operation in a synaptic environment. PMID:26255587

  5. Glutamate and its receptors in the pathophysiology and treatment of major depressive disorder

    PubMed Central

    Ionescu, Dawn F.; Richards, Erica M.; Zarate, Carlos A.

    2014-01-01

    Monoaminergic neurotransmitter (serotonin, norepinephrine and dopamine) mechanisms of disease dominated the research landscape in the pathophysiology and treatment of major depressive disorder (MDD) for more than 50 years and still dominate available treatment options. However, the sum of all brain neurons that use monoamines as their primary neurotransmitter is <20 %. In addition, most patients treated with monoaminergic antidepressants are left with significant residual symptoms and psychosocial disability not to mention side effects, e.g., sexual dysfunction. In the past several decades, there has been greater focus on the major excitatory neurotransmitter in the human brain, glutamate, in the pathophysiology and treatment of MDD. Although several preclinical and human magnetic resonance spectroscopy studies had already implicated glutamatergic abnormalities in the human brain, it was rocketed by the discovery that the N-methyl-D-aspartate receptor antagonist ketamine has rapid and potent antidepressant effects in even the most treatment-resistant MDD patients, including those who failed to respond to electroconvulsive therapy and who have active suicidal ideation. In this review, we will first provide a brief introduction to glutamate and its receptors in the mammalian brain. We will then review the clinical evidence for glutamatergic dysfunction in MDD, the discovery and progress-to-date with ketamine as a rapidly acting antidepressant, and other glutamate receptor modulators (including proprietary medications) for treatment-resistant depression. We will finally conclude by offering potential future directions necessary to realize the enormous therapeutic promise of glutamatergic antidepressants. PMID:24318540

  6. Glutamate and its receptors in the pathophysiology and treatment of major depressive disorder.

    PubMed

    Niciu, Mark J; Ionescu, Dawn F; Richards, Erica M; Zarate, Carlos A

    2014-08-01

    Monoaminergic neurotransmitter (serotonin, norepinephrine and dopamine) mechanisms of disease dominated the research landscape in the pathophysiology and treatment of major depressive disorder (MDD) for more than 50 years and still dominate available treatment options. However, the sum of all brain neurons that use monoamines as their primary neurotransmitter is <20%. In addition, most patients treated with monoaminergic antidepressants are left with significant residual symptoms and psychosocial disability not to mention side effects, e.g., sexual dysfunction. In the past several decades, there has been greater focus on the major excitatory neurotransmitter in the human brain, glutamate, in the pathophysiology and treatment of MDD. Although several preclinical and human magnetic resonance spectroscopy studies had already implicated glutamatergic abnormalities in the human brain, it was rocketed by the discovery that the N-methyl-D-aspartate receptor antagonist ketamine has rapid and potent antidepressant effects in even the most treatment-resistant MDD patients, including those who failed to respond to electroconvulsive therapy and who have active suicidal ideation. In this review, we will first provide a brief introduction to glutamate and its receptors in the mammalian brain. We will then review the clinical evidence for glutamatergic dysfunction in MDD, the discovery and progress-to-date with ketamine as a rapidly acting antidepressant, and other glutamate receptor modulators (including proprietary medications) for treatment-resistant depression. We will finally conclude by offering potential future directions necessary to realize the enormous therapeutic promise of glutamatergic antidepressants.

  7. Metabotropic glutamate receptor 5 couples cellular prion protein to intracellular signalling in Alzheimer's disease.

    PubMed

    Haas, Laura T; Salazar, Santiago V; Kostylev, Mikhail A; Um, Ji Won; Kaufman, Adam C; Strittmatter, Stephen M

    2016-02-01

    Alzheimer's disease-related phenotypes in mice can be rescued by blockade of either cellular prion protein or metabotropic glutamate receptor 5. We sought genetic and biochemical evidence that these proteins function cooperatively as an obligate complex in the brain. We show that cellular prion protein associates via transmembrane metabotropic glutamate receptor 5 with the intracellular protein mediators Homer1b/c, calcium/calmodulin-dependent protein kinase II, and the Alzheimer's disease risk gene product protein tyrosine kinase 2 beta. Coupling of cellular prion protein to these intracellular proteins is modified by soluble amyloid-β oligomers, by mouse brain Alzheimer's disease transgenes or by human Alzheimer's disease pathology. Amyloid-β oligomer-triggered phosphorylation of intracellular protein mediators and impairment of synaptic plasticity in vitro requires Prnp-Grm5 genetic interaction, being absent in transheterozygous loss-of-function, but present in either single heterozygote. Importantly, genetic coupling between Prnp and Grm5 is also responsible for signalling, for survival and for synapse loss in Alzheimer's disease transgenic model mice. Thus, the interaction between metabotropic glutamate receptor 5 and cellular prion protein has a central role in Alzheimer's disease pathogenesis, and the complex is a potential target for disease-modifying intervention.

  8. Distribution of Vesicular Glutamate Transporter 2 and Ionotropic Glutamate Receptors in the Auditory Ganglion and Cochlear Nuclei of Pigeons (Columba livia).

    PubMed

    Karim, M R; Atoji, Y

    2016-02-01

    Glutamate is a principal excitatory neurotransmitter in the auditory system. Our previous studies revealed localization of glutamate receptor mRNAs in the pigeon cochlear nuclei, suggesting the existence of glutamatergic input from the auditory nerve to the brainstem. This study demonstrated localization of mRNAs for vesicular glutamate transporter 2 (vGluT2) and ionotropic glutamate receptors (AMPA, kainate and NMDA) in the auditory ganglion (AG) and cochlear nuclei (magnocellular, angular and laminar nuclei). VGluT2 mRNA was intensely expressed in AG and intensely or moderately in the cochlear nuclei. The AG and cochlear nuclei showed intense-to-moderate mRNA signals for GluA2, GluA3, GluA4, GluK4 and GluN1. These results suggest that the pigeon AG neurons receives glutamatergic input from hair cells and in turn projects to the magnocellular and angular nuclei. Glutamate may play a pivotal role in the excitatory synapse transmission in the peripheral auditory pathway of birds.

  9. Cognitive effects of Group I metabotropic glutamate receptor ligands in the context of drug addiction

    PubMed Central

    Olive, M. Foster

    2010-01-01

    Glutamate plays a pivotal role in regulating drug self-administration and drug-seeking behavior, and the past decade has witnessed a substantial surge of interest in the role of Group I metabotropic glutamate receptors (mGlu1 and mGlu5 receptors) in mediating these behaviors. As will be reviewed here, Group I mGlu receptors are involved in normal and drug-induced synaptic plasticity, drug reward, reinforcement and relapse-like behaviors, and addiction-related cognitive processes such as maladaptive learning and memory, behavioral inflexibility, and extinction learning. Animal models of addiction have revealed that antagonists of Group I mGlu receptors, particularly the mGlu5 receptor, reduce self-administration of virtually all drugs of abuse. Since inhibitors of mGlu5 receptor function have now entered clinical trials for other medical conditions and appear to be well-tolerated, a key question that remains unanswered is - what changes in cognition are produced by these compounds that result in reduced drug intake and drug-seeking behavior? Finally, in contrast to mGlu5 receptor antagonists, recent studies have indicated that positive allosteric modulation of mGlu5 receptors actually enhances synaptic plasticity and improves various aspects of cognition, including spatial learning, behavioral flexibility, and extinction of drug-seeking behavior. Thus, while inhibition of Group I mGlu receptor function may reduce drug reward, reinforcement, and relapse-related behaviors, positive allosteric modulation of the mGlu5 receptor subtype may actually enhance cognition and potentially reverse some of the cognitive deficits associated with chronic drug use. PMID:20371237

  10. Positive Allosteric Modulators of Metabotropic Glutamate 2 Receptors in Schizophrenia Treatment

    PubMed Central

    Ellaithy, Amr; Younkin, Jason; Gonzalez-Maeso, Javier; Logothetis, Diomedes E.

    2015-01-01

    The last two decades have witnessed a rise in the “NMDA receptor hypofunction” hypothesis for schizophrenia, a devastating disorder that affects around 1% of the population worldwide. A variety of presynaptic, postsynaptic and regulatory proteins involved in glutamatergic signaling have thus been proposed as potential therapeutic targets. This Review focuses on positive allosteric modulation of metabotropic glutamate 2 receptors (mGlu2Rs) and discusses how recent preclinical epigenetic data may provide a molecular explanation for the discrepant results of clinical studies, further stimulating the field to exploit the promise of mGlu2R as a target for schizophrenia treatment. PMID:26148747

  11. Role of zinc influx via AMPA/kainate receptor activation in metabotropic glutamate receptor-mediated calcium release.

    PubMed

    Takeda, Atsushi; Fuke, Sayuri; Minami, Akira; Oku, Naoto

    2007-05-01

    The uptake of free zinc into CA3 pyramidal cells and its significance was examined in rat hippocampal slices with ZnAF-2DA, a membrane-permeable zinc indicator. Intracellular ZnAF-2 signal in the CA3 pyramidal cell layer was increased during delivery of tetanic stimuli to the dentate granule cell layer. This increase was completely blocked in the presence of CNQX, an AMPA/kainate receptor antagonist. These results suggest that free zinc is taken up into CA3 pyramidal cells via activation of AMPA/kainate receptors. The effect of free zinc levels in the CA3 pyramidal cells on the increase in intracellular calcium via Group I metabotropic glutamate receptors was examined by regional delivery of tADA, a Group I metabotropic glutamate receptor agonist, to the stratum lucidum after blockade of AMPA/kainate receptor-mediated calcium and zinc influx. Intracellular calcium orange signal in the CA3 pyramidal cell layer was increased by tADA, whereas intracellular ZnAF-2 signal was not increased even in the presence of 100 muM zinc, suggesting that tADA induces calcium release from internal stores in CA3 pyramidal cells and is not involved in zinc uptake. The increase in calcium orange signal by tADA was enhanced by perfusion with pyrithione, a zinc ionophore that decreased basal ZnAF-2 signal in the CA3 pyramidal cell layer. It was blocked by perfusion with pyrithione and zinc that increased basal ZnAF-2 signal. The present study indicates that the increase in free calcium levels via the metabotropic glutamate receptor pathway is inversely related to free zinc levels in CA3 pyramidal cells.

  12. Involvement of putative glutamate receptors in plant defence signaling and NO production.

    PubMed

    Vatsa, Parul; Chiltz, Annick; Bourque, Stéphane; Wendehenne, David; Garcia-Brugger, Angela; Pugin, Alain

    2011-12-01

    Ionotropic glutamate receptors (iGluRs) are non-selective cation channels permeable to calcium, present in animals and plants. In mammals, glutamate is a well-known neurotransmitter and recently has been recognized as an immunomodulator. As animals and plants share common mechanisms that govern innate immunity with calcium playing a key role in plant defence activation, we have checked the involvement of putative iGluRs in plant defence signaling. Using tobacco cells, we first provide evidence supporting the activity of iGluRs as calcium channels and their involvement in NO production as reported in animals. Thereafter, iGluRs were shown to be activated in response to cryptogein, a well studied elicitor of defence response, and partly responsible for cryptogein-induced NO production. However, other cryptogein-induced calcium-dependent events including anion efflux, H(2)O(2) production, MAPK activation and hypersensitive response (HR) did not depend on iGluRs indicating that different calcium channels regulate different processes at the cell level. We have also demonstrated that cryptogein induces efflux of glutamate in the apoplast by exocytosis. Taken together, our results demonstrate for the first time, an involvement of a putative iGluR in plant defence signaling and NO production, by mechanisms that show homology with glutamate mode of action in mammals.

  13. Α-amino-β-fluorocyclopropanecarboxylic acids as a new tool for drug development: synthesis of glutamic acid analogs and agonist activity towards metabotropic glutamate receptor 4.

    PubMed

    Lemonnier, Gérald; Lion, Cédric; Quirion, Jean-Charles; Pin, Jean-Philippe; Goudet, Cyril; Jubault, Philippe

    2012-08-01

    Herein we describe the diastereoselective synthesis of glutamic acid analogs and the evaluation of their agonist activity towards metabotropic glutamate receptor subtype 4 (mGluR4). These analogs are based on a monofluorinated cyclopropane core substituted with an α-aminoacid function. The potential of this new building block as a tool for the development of a novel class of drugs is demonstrated with racemic analog 11a that displayed the best agonist activity with an EC50 of 340 nM.

  14. Endocannabinoid control of glutamate NMDA receptors: the therapeutic potential and consequences of dysfunction

    PubMed Central

    Rodríguez-Muñoz, María; Sánchez-Blázquez, Pilar; Merlos, Manuel; Garzón-Niño, Javier

    2016-01-01

    Glutamate is probably the most important excitatory neurotransmitter in the brain. The glutamate N-methyl-D-aspartate receptor (NMDAR) is a calcium-gated channel that coordinates with G protein-coupled receptors (GPCRs) to establish the efficiency of the synaptic transmission. Cross-regulation between these receptors requires the concerted activity of the histidine triad nucleotide-binding protein 1 (HINT1) and of the sigma receptor type 1 (σ1R). Essential brain functions like learning, memory formation and consolidation, mood and behavioral responses to exogenous stimuli depend on the activity of NMDARs. In this biological context, endocannabinoids are released to retain NMDAR activity within physiological limits. The efficacy of such control depends on HINT1/σ1R assisting in the physical coupling between cannabinoid type 1 receptors (CB1Rs) and NMDARs to dampen their activity. Subsequently, the calcium-regulated HINT1/σ1R protein tandem uncouples CB1Rs to prevent NMDAR hypofunction. Thus, early recruitment or a disproportionate cannabinoid induced response can bring about excess dampening of NMDAR activity, impeding its adequate integration with GPCR signaling. Alternatively, this control circuit can apparently be overridden in situations where bursts of NMDAR overactivity provoke convulsive syndromes. In this review we will discuss the possible relevance of the HINT1/σ1R tandem and its use by endocannabinoids to diminish NMDAR activity and their implications in psychosis/schizophrenia, as well as in NMDAR-mediated convulsive episodes. PMID:27323834

  15. GRLD-1 regulates cell-wide abundance of glutamate receptor through post-transcriptional regulation

    PubMed Central

    Wang, George J.; Kang, Lijun; Kim, Julie E.; Maro, Géraldine S.; Xu, X. Z. Shawn; Shen, Kang

    2011-01-01

    AMPA receptors mediate most of the fast postsynaptic response at glutamatergic synapses. The abundance of AMPA receptors in neurons and at postsynaptic membranes is tightly regulated. Changes in synaptic AMPA receptor levels have been proposed to be a key regulatory event in synaptic plasticity and learning and memory. While the local, synapse-specific regulation of AMPA receptors has been intensely studied, the global, cell-wide control is less well understood. Using a forward genetic approach, we identified Glutamate Receptor Level Decreased-1 (GRLD-1), a putative RNA-binding protein that is required for efficient production of GLR-1 in the AVE interneurons in the nematode Caenorhabditis elegans. In grld-1 mutants, GLR-1 levels were drastically reduced. Consistently, both glutamate-induced currents in AVE and glr-1-dependent nose-touch avoidance behavior were defective in grld-1 mutants. We propose that this evolutionarily conserved family of proteins controls the abundance of GLR-1 by regulating glr-1 transcript splicing. PMID:21037582

  16. Reduction in Ventral Midbrain NMDA Receptors Reveals Two Opposite Modulatory Roles for Glutamate on Reward

    PubMed Central

    Hernandez, Giovanni; Khodami-Pour, Ali; Lévesque, Daniel; Rompré, Pierre-Paul

    2015-01-01

    Glutamate is a major component of the reward circuitry and recent clinical studies suggest that new molecules that would target glutamate neurotransmission are most likely to constitute more effective medications for mood disorders. It is well known that activation of N-methyl-D-aspartate glutamate receptors (NMDARs) initiates dopamine burst firing, a mode associated with reward signaling; but NMDARs also contribute to the maintenance of an inhibitory drive to dopamine neurons. Such opposite modulatory functions imply that different subtypes of NMDARs are expressed on different ventral midbrain (VM) neurons and/or afferent inputs to dopamine neurons. By using the small interfering RNA (siRNA) technique, we studied the effects of VM downregulation of NMDAR subunits GluN1, GluN2A, and GluN2D on reward induced by dorsal raphe electrical stimulation. Reward thresholds were measured before and 24 h after each of three consecutive daily bilateral microinjections of siRNA for the targeted receptor subunit(s) or non-active RNA sequence. After the last measurement, reward thresholds were reassessed following a bilateral microinjection of the preferred GluN2A-NMDA antagonist, (2R,4S)-4-(3-Phosphopropyl)-2-piperidinecarboxylic acid (PPPA). Western-blot analysis showed that siRNAs reduced GluN1- and GluN2A-containing receptors whereas behavioral tests showed that only a reduction in GluN1 produced reward attenuation. Despite NMDAR reduction, reward-enhancing effect of PPPA remained unchanged. We conclude that VM glutamate relays the reward signal initiated by dorsal raphe electrical stimulation by acting on NMDARs devoid of GluN2A/2D subunits and exerts an inhibition on this reward signal by acting on GluN2A-containing NMDARs most likely located on afferent terminals. PMID:25578795

  17. Microbial methodological artifacts in (/sup 3/H)glutamate receptor binding assays

    SciTech Connect

    Yoneda, Y.; Ogita, K.

    1989-03-01

    Incubation of radiolabeled L-glutamic acid, a putative central excitatory neurotransmitter, in 50 mM Tris-acetate buffer (pH 7.4) at 30 degrees C in the absence of brain synaptic membranes resulted in a significant adsorption of the radioactivity to glass fiber filters routinely employed to trap the bound ligand in receptor binding assays. The adsorption was not only eliminated by the inclusion of L-isomers of structurally related amino acids, but also inhibited by that of most presumed agonists and antagonists for the brain glutamate receptors. This displaceable adsorption was a temperature-dependent nonreversible, and saturable phenomenon. Scatchard analysis of these data revealed that the adsorption consisted of a single component with an apparent dissociation constant of 73 nM. The displaceable adsorption was significantly attenuated by a concurrent incubation with papain, pronase E, and phospholipase C. A significant amount of the radioactivity was detected in the pass-through fraction of the Dowex column following an application of the reaction mixture incubated with purified (/sup 3/H)glutamate at 30/degree/C for 60 min in the absence of membranous proteins added. Complete abolition of the displaceable adsorption resulted from the use of incubation buffer boiled at 100 degrees C as well as filtered through a nitrocellulose membrane filter with a pore size of 0.45 micron immediately before use. These results suggest that the displaceable adsorption may be attributable to the radioactive metabolite of (/sup 3/H)glutamate by microorganisms contaminating the Tris-acetate buffer. This might in part contribute to some of the controversial results with regard to receptor binding studies on acidic amino acids.

  18. Structural, signalling and regulatory properties of the group I metabotropic glutamate receptors: prototypic family C G-protein-coupled receptors.

    PubMed Central

    Hermans, E; Challiss, R A

    2001-01-01

    In 1991 a new type of G-protein-coupled receptor (GPCR) was cloned, the type 1a metabotropic glutamate (mGlu) receptor, which, despite possessing the defining seven-transmembrane topology of the GPCR superfamily, bore little resemblance to the growing number of other cloned GPCRs. Subsequent studies have shown that there are eight mammalian mGlu receptors that, together with the calcium-sensing receptor, the GABA(B) receptor (where GABA is gamma-aminobutyric acid) and a subset of pheromone, olfactory and taste receptors, make up GPCR family C. Currently available data suggest that family C GPCRs share a number of structural, biochemical and regulatory characteristics, which differ markedly from those of the other GPCR families, most notably the rhodopsin/family A GPCRs that have been most widely studied to date. This review will focus on the group I mGlu receptors (mGlu1 and mGlu5). This subgroup of receptors is widely and differentially expressed in neuronal and glial cells within the brain, and receptor activation has been implicated in the control of an array of key signalling events, including roles in the adaptative changes needed for long-term depression or potentiation of neuronal synaptic connectivity. In addition to playing critical physiological roles within the brain, the mGlu receptors are also currently the focus of considerable attention because of their potential as drug targets for the treatment of a variety of neurological and psychiatric disorders. PMID:11672421

  19. Expression of ionotropic glutamate receptors, AMPA, kainite and NMDA, in the pigeon retina.

    PubMed

    Atoji, Yasuro

    2015-07-01

    Glutamate is an excitatory neurotransmitter in the vertebrate retina. A previous study found vesicular glutamate transporter 2 (vGluT2) mRNA in the pigeon retina, suggesting that bipolar and ganglion cells are glutamatergic. The present study examined the localization of ionotropic glutamate receptors to identify receptor cells in the pigeon retina using in situ hybridization histochemistry. Nine subunits of AMPA receptor (GluA1, GluA2, GluA3, and GluA4), kainate receptor (GluK1, GluK2, and GluK4), and NMDA receptor (GluN1 and GluN2A) were found to be expressed in the inner nuclear layer (INL) and ganglion cell layers. GluA1, GluA2, GluA3, and GluA4 were primarily expressed in the inner half of INL, and the signal intensity was strong for GluA2, GluA3, and GluA4. GluK1 was intensely expressed in the outer half of INL, whereas GluK2 and GluK4 were mainly localized in the inner half of INL. GluN1 and GluN2A were moderately expressed in the inner half of INL. Horizontal cells expressed GluA3 and GluA4, and ganglion cells expressed all subunits examined. These results suggest that the glutamatergic neurotransmission in the pigeon retina is similar to that in mammals.

  20. The possible involvement of NMDA glutamate receptor in the etiopathogenesis of bipolar disorder.

    PubMed

    Fountoulakis, Konstantinos N

    2012-01-01

    Glutamate is the most abundant excitatory neurotransmitter in the brain and the ionotropic NMDA receptor is one of the major classes of its receptors, thought to play an important role in schizophrenia and mood disorders. The current systematic review summarized the evidence concerning the involvement of NMDA receptors in the pathophysiology of bipolar disorder. Genetic studies point to the genes encoding the NMDA 1, 2A and 2B subunits while neuropathological studies suggest a possible region specific decrease in the density of NMDA receptor and more consistently a reduced NMDA-mediated glutamatergic activity in patients with bipolar disorder in the frame of slower NMDA kinetics because of lower contribution of NR2A subunits. However the literature is poor and incomplete; future research is necessary to elucidate the mechanisms underlying bipolar disorder and its specific relationship to a possible NMDA malfunction and to explore the possibility of developing novel therapeutic agents.

  1. Glutamate-induced depression of EPSP-spike coupling in rat hippocampal CA1 neurons and modulation by adenosine receptors.

    PubMed

    Ferguson, Alexandra L; Stone, Trevor W

    2010-04-01

    The presence of high concentrations of glutamate in the extracellular fluid following brain trauma or ischaemia may contribute substantially to subsequent impairments of neuronal function. In this study, glutamate was applied to hippocampal slices for several minutes, producing over-depolarization, which was reflected in an initial loss of evoked population potential size in the CA1 region. Orthodromic population spikes recovered only partially over the following 60 min, whereas antidromic spikes and excitatory postsynaptic potentials (EPSPs) showed greater recovery, implying a change in EPSP-spike coupling (E-S coupling), which was confirmed by intracellular recording from CA1 pyramidal cells. The recovery of EPSPs was enhanced further by dizocilpine, suggesting that the long-lasting glutamate-induced change in E-S coupling involves NMDA receptors. This was supported by experiments showing that when isolated NMDA-receptor-mediated EPSPs were studied in isolation, there was only partial recovery following glutamate, unlike the composite EPSPs. The recovery of orthodromic population spikes and NMDA-receptor-mediated EPSPs following glutamate was enhanced by the adenosine A1 receptor blocker DPCPX, the A2A receptor antagonist SCH58261 or adenosine deaminase, associated with a loss of restoration to normal of the glutamate-induced E-S depression. The results indicate that the long-lasting depression of neuronal excitability following recovery from glutamate is associated with a depression of E-S coupling. This effect is partly dependent on activation of NMDA receptors, which modify adenosine release or the sensitivity of adenosine receptors. The results may have implications for the use of A1 and A2A receptor ligands as cognitive enhancers or neuroprotectants.

  2. Corticothalamic Activation Modulates Thalamic Firing Through Glutamate "Metabotropic" Receptors

    NASA Astrophysics Data System (ADS)

    McCormick, David A.; von Krosigk, Marcus

    1992-04-01

    The mammalian thalamus forms an obligatory relay for nearly all sensory information that reaches the cerebral cortex. The transmission of sensory information by the thalamus varies in a state-dependent manner, such that during slow wave sleep or drowsiness thalamic responsiveness is markedly reduced, whereas during the waking, attentive state transmission is enhanced. Although activation of brainstem inputs to thalamic neurons has long been assumed to underlie this gating of sensory transfer through the thalamus, numerically the largest input to thalamic relay neurons derives from layer VI cells of the cerebral cortex. Here we report that activation of corticothalamic fibers causes a prolonged excitatory postsynaptic potential in guinea pig dorsal lateral geniculate relay neurons resulting from the reduction of a potassium conductance, consistent with the activation of glutamatergic "metabotropic" receptors. This slow depolarization can switch firing of thalamic neurons from the burst firing mode, which is prevalent during slow wave sleep, to the single spike mode, which is prevalent during waking, thereby facilitating transmission of sensory information through the thalamus. This prolonged enhancement of thalamic transfer may allow the cerebral cortex to gate or control selective fields of sensory inputs in a manner that facilitates arousal, attention, and cognition.

  3. The Effect of Glutamate Receptor Agonists on Mouse Retinal Astrocyte [Ca2+]i

    PubMed Central

    Blandford, Stephanie N.

    2016-01-01

    Calcium-imaging techniques were used to determine if mouse retinal astrocytes in situ respond to agonists of ionotropic (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, AMPA; N-methyl-D-aspartate, NMDA) and metabotropic (S-3,5-dihydroxyphenylglycine, DHPG; trans-1-amino-1,3-cyclopentanedicarboxylic acid, ACPD) glutamate receptors. In most cases we found no evidence that retinal astrocyte intracellular calcium ion concentration ([Ca2+]i) increased in response to these glutamate agonists. The one exception was AMPA that increased [Ca2+]i in some, but not all, mouse retinal astrocytes in situ. However, AMPA did not increase [Ca2+]i in mouse retinal astrocytes in vitro, suggesting that the effect of AMPA in situ may be indirect. PMID:27413752

  4. The Effect of Glutamate Receptor Agonists on Mouse Retinal Astrocyte [Ca(2+)]i.

    PubMed

    Blandford, Stephanie N; Baldridge, William H

    2016-01-01

    Calcium-imaging techniques were used to determine if mouse retinal astrocytes in situ respond to agonists of ionotropic (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, AMPA; N-methyl-D-aspartate, NMDA) and metabotropic (S-3,5-dihydroxyphenylglycine, DHPG; trans-1-amino-1,3-cyclopentanedicarboxylic acid, ACPD) glutamate receptors. In most cases we found no evidence that retinal astrocyte intracellular calcium ion concentration ([Ca(2+)]i) increased in response to these glutamate agonists. The one exception was AMPA that increased [Ca(2+)]i in some, but not all, mouse retinal astrocytes in situ. However, AMPA did not increase [Ca(2+)]i in mouse retinal astrocytes in vitro, suggesting that the effect of AMPA in situ may be indirect.

  5. Recent advances in the medicinal chemistry of the metabotropic glutamate receptor 1 (mGlu₁).

    PubMed

    Owen, Dafydd R

    2011-08-17

    This Review summarizes the medicinal chemistry found in publications on both orthosteric and allosteric modulators of the metabotropic glutamate receptor 1 (mGlu(1)) from 2005 to the present. The time period covered by the scope of this current review has been particularly rich in mGlu(1)-related publications with numbers quadrupling when compared to the preceding five year period of 2000-2005. Publications in the field peaked in 2007 with over 35 articles appearing in the peer reviewed literature in the course of that year. Given that glutamate is one of the primary excitatory neurotransmitters in the mammalian central nervous system (CNS), it is unsurprising that it acts upon several receptors that are considered to be of potential therapeutic interest for many indications. Orthosteric and allosteric modulation of the receptor is possible, with a logical extrapolation to the chemotypes used for each strategy. The last five years of publications have yielded many mGlu(1) selective antagonist chemotypyes, most of which have shown efficacy in pain in vivo models. However, the primary impact of these compounds has been to highlight the mechanistic safety risks of mGlu(1) antagonism, independent of chemotype. As a review in medicinal chemistry, the primary focus of this paper will be on the design and, to a lesser degree, synthetic strategies for the delivery of subtype selective, CNS penetrant, druglike compounds through a "medchem" program, targeting modulators of the mGlu(1) receptor.

  6. Filamin, a synaptic organizer in Drosophila, determines glutamate receptor composition and membrane growth

    PubMed Central

    Lee, GaYoung; Schwarz, Thomas L

    2016-01-01

    Filamin is a scaffolding protein that functions in many cells as an actin-crosslinker. FLN90, an isoform of the Drosophila ortholog Filamin/cheerio that lacks the actin-binding domain, is here shown to govern the growth of postsynaptic membrane folds and the composition of glutamate receptor clusters at the larval neuromuscular junction. Genetic and biochemical analyses revealed that FLN90 is present surrounding synaptic boutons. FLN90 is required in the muscle for localization of the kinase dPak and, downstream of dPak, for localization of the GTPase Ral and the exocyst complex to this region. Consequently, Filamin is needed for growth of the subsynaptic reticulum. In addition, in the absence of filamin, type-A glutamate receptor subunits are lacking at the postsynapse, while type-B subunits cluster correctly. Receptor composition is dependent on dPak, but independent of the Ral pathway. Thus two major aspects of synapse formation, morphological plasticity and subtype-specific receptor clustering, require postsynaptic Filamin. DOI: http://dx.doi.org/10.7554/eLife.19991.001 PMID:27914199

  7. Differential effects of protein phosphatases in the recycling of metabotropic glutamate receptor 5.

    PubMed

    Mahato, P K; Pandey, S; Bhattacharyya, S

    2015-10-15

    The major excitatory neurotransmitter Glutamate acts on both ionotropic and metabotropic glutamate receptors (mGluRs) in the central nervous system. mGluR5, a member of the group I mGluR family is widely expressed throughout the brain and plays important roles in a variety of neuronal processes including various forms of synaptic plasticity. This receptor is also involved in various neuropsychiatric disorders, viz., Fragile X syndrome, autism etc. It has been reported that mGluR5 undergoes desensitization and subsequently internalization on ligand exposure in various cell types. However, the downstream events after the internalization and the molecular players involved in the post-endocytic events of this receptor have not been studied. In the present study, we find that subsequent to internalization mGluR5 enters the recycling compartment. After that the receptor recycles back to the cell surface. We also show here that the recycling of mGluR5 is dependent on protein phosphatases. Our data suggest that mGluR5 recycling is completely dependent on the activity of PP2A whereas, PP2B has partial effect on this process. Thus our study suggests that mGluR5 recycles back to the cell surface after ligand-dependent internalization and protein phosphatases that have been implicated in various forms of synaptic plasticity have differential effects on the recycling of mGluR5.

  8. Glutamate receptors in the nucleus tractus solitarius contribute to ventilatory acclimatization to hypoxia in rat

    PubMed Central

    Pamenter, Matthew E; Carr, J Austin; Go, Ariel; Fu, Zhenxing; Reid, Stephen G; Powell, Frank L

    2014-01-01

    When exposed to a hypoxic environment the body's first response is a reflex increase in ventilation, termed the hypoxic ventilatory response (HVR). With chronic sustained hypoxia (CSH), such as during acclimatization to high altitude, an additional time-dependent increase in ventilation occurs, which increases the HVR. This secondary increase persists after exposure to CSH and involves plasticity within the circuits in the central nervous system that control breathing. Currently these mechanisms of HVR plasticity are unknown and we hypothesized that they involve glutamatergic synapses in the nucleus tractus solitarius (NTS), where afferent endings from arterial chemoreceptors terminate. To test this, we treated rats held in normoxia (CON) or 10% O2 (CSH) for 7 days and measured ventilation in conscious, unrestrained animals before and after microinjecting glutamate receptor agonists and antagonists into the NTS. In normoxia, AMPA increased ventilation 25% and 50% in CON and CSH, respectively, while NMDA doubled ventilation in both groups (P < 0.05). Specific AMPA and NMDA receptor antagonists (NBQX and MK801, respectively) abolished these effects. MK801 significantly decreased the HVR in CON rats, and completely blocked the acute HVR in CSH rats but had no effect on ventilation in normoxia. NBQX decreased ventilation whenever it was increased relative to normoxic controls; i.e. acute hypoxia in CON and CSH, and normoxia in CSH. These results support our hypothesis that glutamate receptors in the NTS contribute to plasticity in the HVR with CSH. The mechanism underlying this synaptic plasticity is probably glutamate receptor modification, as in CSH rats the expression of phosphorylated NR1 and GluR1 proteins in the NTS increased 35% and 70%, respectively, relative to that in CON rats. PMID:24492841

  9. Glutamate receptors in the nucleus tractus solitarius contribute to ventilatory acclimatization to hypoxia in rat.

    PubMed

    Pamenter, Matthew E; Carr, J Austin; Go, Ariel; Fu, Zhenxing; Reid, Stephen G; Powell, Frank L

    2014-04-15

    When exposed to a hypoxic environment the body's first response is a reflex increase in ventilation, termed the hypoxic ventilatory response (HVR). With chronic sustained hypoxia (CSH), such as during acclimatization to high altitude, an additional time-dependent increase in ventilation occurs, which increases the HVR. This secondary increase persists after exposure to CSH and involves plasticity within the circuits in the central nervous system that control breathing. Currently these mechanisms of HVR plasticity are unknown and we hypothesized that they involve glutamatergic synapses in the nucleus tractus solitarius (NTS), where afferent endings from arterial chemoreceptors terminate. To test this, we treated rats held in normoxia (CON) or 10% O2 (CSH) for 7 days and measured ventilation in conscious, unrestrained animals before and after microinjecting glutamate receptor agonists and antagonists into the NTS. In normoxia, AMPA increased ventilation 25% and 50% in CON and CSH, respectively, while NMDA doubled ventilation in both groups (P < 0.05). Specific AMPA and NMDA receptor antagonists (NBQX and MK801, respectively) abolished these effects. MK801 significantly decreased the HVR in CON rats, and completely blocked the acute HVR in CSH rats but had no effect on ventilation in normoxia. NBQX decreased ventilation whenever it was increased relative to normoxic controls; i.e. acute hypoxia in CON and CSH, and normoxia in CSH. These results support our hypothesis that glutamate receptors in the NTS contribute to plasticity in the HVR with CSH. The mechanism underlying this synaptic plasticity is probably glutamate receptor modification, as in CSH rats the expression of phosphorylated NR1 and GluR1 proteins in the NTS increased 35% and 70%, respectively, relative to that in CON rats.

  10. Metabotropic glutamate receptor antagonists selectively enhance responses of slowly adapting type I mechanoreceptors.

    PubMed

    Cahusac, Peter M B; Senok, Solomon S

    2006-03-15

    There is evidence that glutamate may participate as a transmitter at the junction between Merkel cells and the nerve terminals of slowly adapting type I (St I) units. We recorded extracellularly from the deep vibrissal nerve of an isolated rat vibrissa preparation in vitro. Five second trapezoid stimulus ramp deflections of the hair shaft were used to evoke responses. We bath-applied two compounds, which we planned would interfere with glutamatergic transmission. (2S)-2-Amino-2-[(1S,2S)-2-carboxycycloprop-1-yl]-3-(xanth-9-yl) propanoic acid (LY341495) was used at concentrations up to 100 microM to block all known metabotropic glutamate (mGlu) receptors. The racemic mixture (RS)-4-carboxy-3-hydroxyphenylglycine ((RS)-4C3HPG) was used up to 100 microM to block ionotropic and Group I metabotropic glutamate receptors, and as an agonist at Group II mGlu receptors. Unexpectedly, both compounds had rapid onset excitatory effects on mechanically-evoked responses. (RS)-4C3HPG increased responses, with a mean 146% of control (P < 0.05) in a concentration-dependent manner. LY341495 increased responses, with a mean 128% of control (P < 0.05). With (RS)-4C3HPG in particular, it was noted that the static component (the firing during the last 1 s plateau) was preferentially enhanced relative to the dynamic component (firing during the first 0.5 s). Rapid recovery was seen after wash. Slowly adapting type II units, which have no junctional transmission, were completely unaffected by these compounds up to 200 microM. These results suggest that mGlu receptors play a role in Merkel cell-neurite complex mechanotransduction, although other explanations are considered.

  11. Ca2+ activity at GABAB receptors constitutively promotes metabotropic glutamate signaling in the absence of GABA

    PubMed Central

    Tabata, Toshihide; Araishi, Kenji; Hashimoto, Kouichi; Hashimotodani, Yuki; van der Putten, Herman; Bettler, Bernhard; Kano, Masanobu

    2004-01-01

    Type B γ-aminobutyric acid receptor (GABABR) is a G protein-coupled receptor that regulates neurotransmitter release and neuronal excitability throughout the brain. In various neurons, GABABRs are concentrated at excitatory synapses. Although these receptors are assumed to respond to GABA spillover from neighboring inhibitory synapses, their function is not fully understood. Here we show a previously undescribed function of GABABR exerted independent of GABA. In cerebellar Purkinje cells, interaction of GABABR with extracellular Ca2+ (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}{\\mathrm{Ca}}_{{\\mathrm{o}}}^{2+}\\end{equation*}\\end{document}) leads to a constitutive increase in the glutamate sensitivity of metabotropic glutamate receptor 1 (mGluR1). mGluR1 sensitization is clearly mediated by GABABR because it is absent in GABABR1 subunit-knockout cells. However, the mGluR1 sensitization does not require Gi/o proteins that mediate the GABABR's classical functions. Moreover, coimmunoprecipitation reveals complex formation between GABABR and mGluR1 in the cerebellum. These findings demonstrate that GABABR can act as \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}{\\mathrm{Ca}}_{{\\mathrm{o}}}^{2+}\\end{equation*}\\end{document}-dependent cofactors to enhance neuronal metabotropic glutamate signaling. PMID:15550547

  12. Ionotropic glutamate receptors in the ventral tegmental area regulate cocaine-seeking behavior in rats.

    PubMed

    Sun, Wenlin; Akins, Chana K; Mattingly, Anne E; Rebec, George V

    2005-11-01

    Drug addiction is characterized by compulsive drug-seeking and drug-taking behavior and by a high rate of relapse even after long periods of abstinence. Although the mesocorticolimbic dopamine (DA) pathway is thought to play a critical role in drug craving and relapse, recent evidence also implicates glutamate, an amino acid known to activate DA neurons in the ventral tegmental area (VTA) via ionotropic receptors. To assess whether increased glutamate transmission in the VTA is involved in cocaine-primed drug-seeking behavior, we tested rats in a between-session reinstatement model. They were trained to press a lever for cocaine infusions (0.25 mg/infusion) accompanied by compound stimuli (light and tone) under a modified fixed-ratio 5 reinforcement schedule. Cocaine-primed reinstatement was conducted after lever pressing was extinguished in the absence of the conditioned stimuli. Blockade of ionotropic glutamate receptors in the VTA by local application of kynurenate (0.0, 1.0, 3.2, and 5.6 microg/side) dose-dependently decreased cocaine-primed reinstatement, whereas sucrose-primed reinstatement of sucrose-seeking behavior was unaffected. In addition, the minimum effective dose for decreasing cocaine-primed reinstatement was ineffective in the substantia nigra. Together, these data indicate that glutamatergic activation of the VTA is critical for cocaine-primed reinstatement. Because such activation can increase impulse flow in DA neurons and thus DA release in mesocorticolimbic targets, this glutamate-DA interaction in the VTA may underlie cocaine-primed relapse to cocaine-seeking behavior.

  13. Expression of group III metabotropic glutamate receptors in the reproductive system of male mice.

    PubMed

    Marciniak, Marcin; Chruścicka, Barbara; Lech, Tomasz; Burnat, Grzegorz; Pilc, Andrzej

    2016-03-01

    Although the presence of metabotropic glutamate (mGlu) receptors in the central nervous system is well documented, they have recently been found in peripheral and non-neuronal tissues. In the present study we investigated the expression of group III mGlu receptors in the reproductive system of male mice. Reverse transcription-polymerase chain reaction analysis revealed the presence of mGlu6, mGlu7 and mGlu8 (but not mGlu4) receptor transcripts in testes and epididymides from adult mice. In addition, expression of mGlu6 (Grm6) and mGlu8 receptor (Grm8) mRNA was detected in spermatozoa isolated from the vas deferens. The vas deferens was found to contain only mGlu7 receptor (Grm7) mRNA, which was particularly intense in 21-day-old male mice. In penile homogenates, only the mGlu7 receptor signal was detected. Genetic ablation of the mGlu7 receptor in males led to fertility disorders manifested by decreased insemination capability as well as deterioration of sperm parameters, particularly sperm motility, vitality, sperm membrane integrity and morphology, with a simultaneous increase in sperm concentration. These results indicate that constitutively expressed mGlu receptors in the male reproductive system may play an important role in ejaculation and/or erection processes, as well as in the formation and maturation of spermatozoa.

  14. Potentiation of mouse vagal afferent mechanosensitivity by ionotropic and metabotropic glutamate receptors

    PubMed Central

    Slattery, James A; Page, Amanda J; Dorian, Camilla L; Brierley, Stuart M; Blackshaw, L Ashley

    2006-01-01

    Glutamate acts at central synapses via ionotropic (iGluR – NMDA, AMPA and kainate) and metabotropic glutamate receptors (mGluRs). Group I mGluRs are excitatory whilst group II and III are inhibitory. Inhibitory mGluRs also modulate peripherally the mechanosensitivity of gastro-oesophageal vagal afferents. Here we determined the potential of excitatory GluRs to play an opposing role in modulating vagal afferent mechanosensitivity, and investigated expression of receptor subunit mRNA within the nodose ganglion. The responses of mouse gastro-oesophageal vagal afferents to graded mechanical stimuli were investigated before and during application of selective GluR ligands to their peripheral endings. Two types of vagal afferents were tested: tension receptors, which respond to circumferential tension, and mucosal receptors, which respond only to mucosal stroking. The selective iGluR agonists NMDA and AMPA concentration-dependently potentiated afferent responses. Their corresponding antagonists AP-5 and NBQX alone attenuated mechanosensory responses as did the non-selective antagonist kynurenate. The kainate selective agonist SYM-2081 had minor effects on mechanosensitivity, and the antagonist UBP 302 was ineffective. The mGluR5 antagonist MTEP concentration-dependently inhibited mechanosensitivity. Efficacy of agonists and antagonists differed on mucosal and tension receptors. We conclude that excitatory modulation of afferent mechanosensitivity occurs mainly via NMDA, AMPA and mGlu5 receptors, and the role of each differs according to afferent subtypes. PCR data indicated that all NMDA, kainate and AMPA receptor subunits plus mGluR5 are expressed, and are therefore candidates for the neuromodulation we observed. PMID:16945965

  15. Cbln1 and the δ2 glutamate receptor--an orphan ligand and an orphan receptor find their partners.

    PubMed

    Matsuda, Keiko; Yuzaki, Michisuke

    2012-03-01

    Cerebellin was originally discovered as a Purkinje cell-specific peptide more than two decades ago. Later, its precursor protein precerebellin (Cbln1) was found to be produced in cerebellar granule cells. It has become increasingly clear that although the cerebellin peptide may have certain functions, Cbln1 is an actual signaling molecule that belongs to the C1q family. However, the precise function of Cbln1 has been unresolved. Cbln1 is released from granule cells, and disruption of the cbln1 gene in mice causes a severe reduction in the number of synapses between Purkinje cells and parallel fibers (PFs; axons of granule cells) and results in cerebellar ataxia. The glutamate receptor δ2 (GluD2) is highly expressed on Purkinje cells' dendritic spines which make synapses with PFs. Although GluD2 was identified as a member of the ionotropic glutamate receptors more than 15 years ago, it has been referred to as an orphan receptor because its endogenous ligands are unclear. Interestingly, GluD2-null mice phenocopy cbln1-null mice precisely. Cbln1 and GluD2 have therefore been thought to participate in a common signaling pathway that is required for the formation of PF synapses. We recently established a direct ligand-receptor relationship between Cbln1 and GluD2. The Cbln1-GluD2 complex is located at the cleft of PF-Purkinje cell synapses and bidirectionally regulates both presynaptic and postsynaptic differentiation.

  16. Color development upon reaction of ferric ion with the toxin JSTX, a glutamate receptor blocker present in the venom gland of the spider Nephila clavata (Joro spider).

    PubMed

    Yoshioka, M; Narai, N; Pan-Hou, H; Shimazaki, K; Miwa, A; Kawai, N

    1988-01-01

    A spider toxin, JSTX, derived from Nephila clavata, which blocks glutamate receptor was found to react with Fe3+. Mechanism of the coloration may be chelate formation since the green color completely faded upon the addition of EDTA. The colored JSTX significantly lost its neurophysiological activity. This unique coloration may be useful for not only detecting specific blockers of the glutamate receptor in spider venom but also for characterizing the glutamate receptor.

  17. Extracellular Calcium Modulates Actions of Orthosteric and Allosteric Ligands on Metabotropic Glutamate Receptor 1α*

    PubMed Central

    Jiang, Jason Y.; Nagaraju, Mulpuri; Meyer, Rebecca C.; Zhang, Li; Hamelberg, Donald; Hall, Randy A.; Brown, Edward M.; Conn, P. Jeffrey; Yang, Jenny J.

    2014-01-01

    Metabotropic glutamate receptor 1α (mGluR1α), a member of the family C G protein-coupled receptors, is emerging as a potential drug target for various disorders, including chronic neuronal degenerative diseases. In addition to being activated by glutamate, mGluR1α is also modulated by extracellular Ca2+. However, the underlying mechanism is unknown. Moreover, it has long been challenging to develop receptor-specific agonists due to homologies within the mGluR family, and the Ca2+-binding site(s) on mGluR1α may provide an opportunity for receptor-selective targeting by therapeutics. In the present study, we show that our previously predicted Ca2+-binding site in the hinge region of mGluR1α is adjacent to the site where orthosteric agonists and antagonists bind on the extracellular domain of the receptor. Moreover, we found that extracellular Ca2+ enhanced mGluR1α-mediated intracellular Ca2+ responses evoked by the orthosteric agonist l-quisqualate. Conversely, extracellular Ca2+ diminished the inhibitory effect of the mGluR1α orthosteric antagonist (S)-α-methyl-4-carboxyphenylglycine. In addition, selective positive (Ro 67-4853) and negative (7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxylate ethyl ester) allosteric modulators of mGluR1α potentiated and inhibited responses to extracellular Ca2+, respectively, in a manner similar to their effects on the response of mGluR1α to glutamate. Mutations at residues predicted to be involved in Ca2+ binding, including E325I, had significant effects on the modulation of responses to the orthosteric agonist l-quisqualate and the allosteric modulator Ro 67-4853 by extracellular Ca2+. These studies reveal that binding of extracellular Ca2+ to the predicted Ca2+-binding site in the extracellular domain of mGluR1α modulates not only glutamate-evoked signaling but also the actions of both orthosteric ligands and allosteric modulators on mGluR1α. PMID:24280223

  18. Illuminating Phenylazopyridines To Photoswitch Metabotropic Glutamate Receptors: From the Flask to the Animals

    PubMed Central

    2016-01-01

    Phenylazopyridines are photoisomerizable compounds with high potential to control biological functions with light. We have obtained a series of phenylazopyridines with light dependent activity as negative allosteric modulators (NAM) of metabotropic glutamate receptor subtype 5 (mGlu5). Here we describe the factors needed to achieve an operational molecular photoisomerization and its effective translation into in vitro and in vivo receptor photoswitching, which includes zebrafish larva motility and the regulation of the antinociceptive effects in mice. The combination of light and some specific phenylazopyridine ligands displays atypical pharmacological profiles, including light-dependent receptor overactivation, which can be observed both in vitro and in vivo. Remarkably, the localized administration of light and a photoswitchable compound in the peripheral tissues of rodents or in the brain amygdalae results in an illumination-dependent analgesic effect. The results reveal a robust translation of the phenylazopyridine photoisomerization to a precise photoregulation of biological activity. PMID:28149957

  19. Illuminating Phenylazopyridines To Photoswitch Metabotropic Glutamate Receptors: From the Flask to the Animals.

    PubMed

    Gómez-Santacana, Xavier; Pittolo, Silvia; Rovira, Xavier; Lopez, Marc; Zussy, Charleine; Dalton, James A R; Faucherre, Adèle; Jopling, Chris; Pin, Jean-Philippe; Ciruela, Francisco; Goudet, Cyril; Giraldo, Jesús; Gorostiza, Pau; Llebaria, Amadeu

    2017-01-25

    Phenylazopyridines are photoisomerizable compounds with high potential to control biological functions with light. We have obtained a series of phenylazopyridines with light dependent activity as negative allosteric modulators (NAM) of metabotropic glutamate receptor subtype 5 (mGlu5). Here we describe the factors needed to achieve an operational molecular photoisomerization and its effective translation into in vitro and in vivo receptor photoswitching, which includes zebrafish larva motility and the regulation of the antinociceptive effects in mice. The combination of light and some specific phenylazopyridine ligands displays atypical pharmacological profiles, including light-dependent receptor overactivation, which can be observed both in vitro and in vivo. Remarkably, the localized administration of light and a photoswitchable compound in the peripheral tissues of rodents or in the brain amygdalae results in an illumination-dependent analgesic effect. The results reveal a robust translation of the phenylazopyridine photoisomerization to a precise photoregulation of biological activity.

  20. PET imaging of metabotropic glutamate receptor subtype 5 (mGluR5)

    PubMed Central

    Li, Dan; Shan, Hong; Conti, Peter; Li, Zibo

    2012-01-01

    Metabotropic glutamate receptors (mGluRs) belong to a family of G-protein coupled receptors involved in the modulation of fast excitatory transmission. In particular, the subtype-5 receptor (mGluR5) was found to be an attractive target for the treatment and diagnosis of variety of psychiatric and neurological disease including anxiety, depression, epilepsy, drug addiction, and Parkinson's disease. Positron emission tomography (PET) is a highly sensitive imaging technique that holds great potential for the diagnosis of a brain disorder. In the study published in the American Journal of Nuclear Medicine and Molecular Imaging, a 18F labelled PET probe was developed targeting mGluR5. This paper represents the efforts and challenges on the design and development of novel PET tracers for mGluR5 imaging. PMID:23133800

  1. EVALUATING THE NMDA-GLUTAMATE RECEPTOR AS A SITE OF ACTION FOR TOLUENE USING PATTERN ELICITED VISUAL EVOKED POTENTIALS.

    EPA Science Inventory

    In vitro studies have demonstrated that toluene disrupts the function of NMDA-glutamate receptors, as well as other channels. This has led to the hypothesis that effects on NMDA receptor function may contribute to toluene neurotoxicity, CNS depression, and altered visual evoked ...

  2. Influence of cooling rate on activity of ionotropic glutamate receptors in brain slices at hypothermia.

    PubMed

    Mokrushin, Anatoly A; Pavlinova, Larisa I; Borovikov, Sergey E

    2014-08-01

    Hypothermia is a known approach in the treatment of neurological pathologies. Mild hypothermia enhances the therapeutic window for application of medicines, while deep hypothermia is often accompanied by complications, including problems in the recovery of brain functions. The purpose of present study was to investigate the functioning of glutamate ionotropic receptors in brain slices cooled with different rates during mild, moderate and deep hypothermia. Using a system of gradual cooling combined with electrophysiological recordings in slices, we have shown that synaptic activity mediated by the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid and N-methyl-D-aspartate receptors in rat olfactory cortex was strongly dependent on the rate of lowering the temperature. High cooling rate caused a progressive decrease in glutamate receptor activity in brain slices during gradual cooling from mild to deep hypothermia. On the contrary, low cooling rate slightly changed the synaptic responses in deep hypothermia. The short-term potentiation may be induced in slices by electric tetanization at 16 °C in this case. Hence, low cooling rate promoted preservation of neuronal activity and plasticity in the brain tissue.

  3. Genetically encoding a light switch in an ionotropic glutamate receptor reveals subunit-specific interfaces

    PubMed Central

    Zhu, Shujia; Riou, Morgane; Yao, C. Andrea; Carvalho, Stéphanie; Rodriguez, Pamela C.; Bensaude, Olivier; Paoletti, Pierre; Ye, Shixin

    2014-01-01

    Reprogramming receptors to artificially respond to light has strong potential for molecular studies and interrogation of biological functions. Here, we design a light-controlled ionotropic glutamate receptor by genetically encoding a photoreactive unnatural amino acid (UAA). The photo–cross-linker p-azido-l-phenylalanine (AzF) was encoded in NMDA receptors (NMDARs), a class of glutamate-gated ion channels that play key roles in neuronal development and plasticity. AzF incorporation in the obligatory GluN1 subunit at the GluN1/GluN2B N-terminal domain (NTD) upper lobe dimer interface leads to an irreversible allosteric inhibition of channel activity upon UV illumination. In contrast, when pairing the UAA-containing GluN1 subunit with the GluN2A subunit, light-dependent inactivation is completely absent. By combining electrophysiological and biochemical analyses, we identify subunit-specific structural determinants at the GluN1/GluN2 NTD dimer interfaces that critically dictate UV-controlled inactivation. Our work reveals that the two major NMDAR subtypes differ in their ectodomain-subunit interactions, in particular their electrostatic contacts, resulting in GluN1 NTD coupling more tightly to the GluN2B NTD than to the GluN2A NTD. It also paves the way for engineering light-sensitive ligand-gated ion channels with subtype specificity through the genetic code expansion. PMID:24715733

  4. Postsynaptic actin regulates active zone spacing and glutamate receptor apposition at the Drosophila neuromuscular junction.

    PubMed

    Blunk, Aline D; Akbergenova, Yulia; Cho, Richard W; Lee, Jihye; Walldorf, Uwe; Xu, Ke; Zhong, Guisheng; Zhuang, Xiaowei; Littleton, J Troy

    2014-07-01

    Synaptic communication requires precise alignment of presynaptic active zones with postsynaptic receptors to enable rapid and efficient neurotransmitter release. How transsynaptic signaling between connected partners organizes this synaptic apparatus is poorly understood. To further define the mechanisms that mediate synapse assembly, we carried out a chemical mutagenesis screen in Drosophila to identify mutants defective in the alignment of active zones with postsynaptic glutamate receptor fields at the larval neuromuscular junction. From this screen we identified a mutation in Actin 57B that disrupted synaptic morphology and presynaptic active zone organization. Actin 57B, one of six actin genes in Drosophila, is expressed within the postsynaptic bodywall musculature. The isolated allele, act(E84K), harbors a point mutation in a highly conserved glutamate residue in subdomain 1 that binds members of the Calponin Homology protein family, including spectrin. Homozygous act(E84K) mutants show impaired alignment and spacing of presynaptic active zones, as well as defects in apposition of active zones to postsynaptic glutamate receptor fields. act(E84K) mutants have disrupted postsynaptic actin networks surrounding presynaptic boutons, with the formation of aberrant actin swirls previously observed following disruption of postsynaptic spectrin. Consistent with a disruption of the postsynaptic actin cytoskeleton, spectrin, adducin and the PSD-95 homolog Discs-Large are all mislocalized in act(E84K) mutants. Genetic interactions between act(E84K) and neurexin mutants suggest that the postsynaptic actin cytoskeleton may function together with the Neurexin-Neuroligin transsynaptic signaling complex to mediate normal synapse development and presynaptic active zone organization.

  5. Postsynaptic actin regulates active zone spacing and glutamate receptor apposition at the Drosophila neuromuscular junction

    PubMed Central

    Blunk, Aline D.; Akbergenova, Yulia; Cho, Richard W.; Lee, Jihye; Walldorf, Uwe; Xu, Ke; Zhong, Guisheng; Zhuang, Xiaowei; Littleton, J. Troy

    2014-01-01

    Synaptic communication requires precise alignment of presynaptic active zones with postsynaptic receptors to enable rapid and efficient neurotransmitter release. How transsynaptic signaling between connected partners organizes this synaptic apparatus is poorly understood. To further define the mechanisms that mediate synapse assembly, we carried out a chemical mutagenesis screen in Drosophila to identify mutants defective in the alignment of active zones with postsynaptic glutamate receptor fields at the larval neuromuscular junction. From this screen we identified a mutation in actin 57B that disrupted synaptic morphology and presynaptic active zone organization. Actin 57B, one of six actin genes in Drosophila, is expressed within the postsynaptic bodywall musculature. The isolated allele, actE84K, harbors a point mutation in a highly conserved glutamate residue in subdomain 1 that binds members of the Calponin Homology protein family, including spectrin. Homozygous actE84K mutants show impaired alignment and spacing of presynaptic active zones, as well as defects in apposition of active zones to postsynaptic glutamate receptor fields. actE84K mutants have disrupted postsynaptic actin networks surrounding presynaptic boutons, with the formation of aberrant actin swirls previously observed following disruption of postsynaptic spectrin. Consistent with a disruption of the postsynaptic actin cytoskeleton, spectrin, adducin and the PSD-95 homolog Disc-Large are all mislocalized in actE84K mutants. Genetic interactions between actE84K and neurexin mutants suggest that the postsynaptic actin cytoskeleton may function together with the Neurexin-Neuroligin transsynaptic signaling complex to mediate normal synapse development and presynaptic active zone organization. PMID:25066865

  6. A Genome Wide Association Study Links Glutamate Receptor Pathway to Sporadic Creutzfeldt-Jakob Disease Risk

    PubMed Central

    Sanchez-Juan, Pascual; Bishop, Matthew T.; Kovacs, Gabor G.; Calero, Miguel; Aulchenko, Yurii S.; Ladogana, Anna; Boyd, Alison; Lewis, Victoria; Ponto, Claudia; Calero, Olga; Poleggi, Anna; Carracedo, Ángel; van der Lee, Sven J.; Ströbel, Thomas; Rivadeneira, Fernando; Hofman, Albert; Haïk, Stéphane; Combarros, Onofre; Berciano, José; Uitterlinden, Andre G.; Collins, Steven J.; Budka, Herbert; Brandel, Jean-Philippe; Laplanche, Jean Louis; Pocchiari, Maurizio; Zerr, Inga; Knight, Richard S. G.; Will, Robert G.; van Duijn, Cornelia M.

    2015-01-01

    We performed a genome-wide association (GWA) study in 434 sporadic Creutzfeldt-Jakob disease (sCJD) patients and 1939 controls from the United Kingdom, Germany and The Netherlands. The findings were replicated in an independent sample of 1109 sCJD and 2264 controls provided by a multinational consortium. From the initial GWA analysis we selected 23 SNPs for further genotyping in 1109 sCJD cases from seven different countries. Five SNPs were significantly associated with sCJD after correction for multiple testing. Subsequently these five SNPs were genotyped in 2264 controls. The pooled analysis, including 1543 sCJD cases and 4203 controls, yielded two genome wide significant results: rs6107516 (p-value=7.62x10-9) a variant tagging the prion protein gene (PRNP); and rs6951643 (p-value=1.66x10-8) tagging the Glutamate Receptor Metabotropic 8 gene (GRM8). Next we analysed the data stratifying by country of origin combining samples from the pooled analysis with genotypes from the 1000 Genomes Project and imputed genotypes from the Rotterdam Study (Total n=12967). The meta-analysis of the results showed that rs6107516 (p-value=3.00x10-8) and rs6951643 (p-value=3.91x10-5) remained as the two most significantly associated SNPs. Rs6951643 is located in an intronic region of GRM8, a gene that was additionally tagged by a cluster of 12 SNPs within our top100 ranked results. GRM8 encodes for mGluR8, a protein which belongs to the metabotropic glutamate receptor family, recently shown to be involved in the transduction of cellular signals triggered by the prion protein. Pathway enrichment analyses performed with both Ingenuity Pathway Analysis and ALIGATOR postulates glutamate receptor signalling as one of the main pathways associated with sCJD. In summary, we have detected GRM8 as a novel, non-PRNP, genome-wide significant marker associated with heightened disease risk, providing additional evidence supporting a role of glutamate receptors in sCJD pathogenesis. PMID:25918841

  7. Ionotropic glutamate receptors and glutamate transporters are involved in necrotic neuronal cell death induced by oxygen-glucose deprivation of hippocampal slice cultures.

    PubMed

    Bonde, C; Noraberg, J; Noer, H; Zimmer, J

    2005-01-01

    Organotypic hippocampal slice cultures represent a feasible model for studies of cerebral ischemia and the role of ionotropic glutamate receptors in oxygen-glucose deprivation-induced neurodegeneration. New results and a review of existing data are presented in the first part of this paper. The role of glutamate transporters, with special reference to recent results on inhibition of glutamate transporters under normal and energy-failure (ischemia-like) conditions is reviewed in the last part of the paper. The experimental work is based on hippocampal slice cultures derived from 7 day old rats and grown for about 3 weeks. In such cultures we investigated the subfield neuronal susceptibility to oxygen-glucose deprivation, the type of induced cell death and the involvement of ionotropic glutamate receptors. Hippocampal slice cultures were also used in our studies on glutamate transporters reviewed in the last part of this paper. Neurodegeneration was monitored and/or shown by cellular uptake of propidium iodide, loss of immunocytochemical staining for microtubule-associated protein 2 and staining with Fluoro-Jade B. To distinguish between necrotic vs. apoptotic neuronal cell death we used immunocytochemical staining for active caspase-3 (apoptosis indicator) and Hoechst 33342 staining of nuclear chromatin. Our experimental studies on oxygen-glucose deprivation confirmed that CA1 pyramidal cells were the most susceptible to this ischemia-like condition. Judged by propidium iodide uptake, a selective CA1 lesion, with only minor affection on CA3, occurred in cultures exposed to oxygen-glucose deprivation for 30 min. Nuclear chromatin staining by Hoechst 33342 and staining for active caspase-3 showed that oxygen-glucose deprivation induced necrotic cell death only. Addition of 10 microM of the N-methyl-D-aspartate glutamate receptor antagonist MK-801, and 20 microM of the non-N-methyl-D-aspartate glutamate receptor antagonist 2,3-dihyroxy-6-nitro-7-sulfamoyl

  8. Control of cannabinoid CB1 receptor function on glutamate axon terminals by endogenous adenosine acting at A1 receptors.

    PubMed

    Hoffman, Alexander F; Laaris, Nora; Kawamura, Masahito; Masino, Susan A; Lupica, Carl R

    2010-01-13

    Marijuana is a widely used drug that impairs memory through interaction between its psychoactive constituent, Delta-9-tetrahydrocannabinol (Delta(9)-THC), and CB(1) receptors (CB1Rs) in the hippocampus. CB1Rs are located on Schaffer collateral (Sc) axon terminals in the hippocampus, where they inhibit glutamate release onto CA1 pyramidal neurons. This action is shared by adenosine A(1) receptors (A1Rs), which are also located on Sc terminals. Furthermore, A1Rs are tonically activated by endogenous adenosine (eADO), leading to suppressed glutamate release under basal conditions. Colocalization of A1Rs and CB1Rs, and their coupling to shared components of signal transduction, suggest that these receptors may interact. We examined the roles of A1Rs and eADO in regulating CB1R inhibition of glutamatergic synaptic transmission in the rodent hippocampus. We found that A1R activation by basal or experimentally increased levels of eADO reduced or eliminated CB1R inhibition of glutamate release, and that blockade of A1Rs with caffeine or other antagonists reversed this effect. The CB1R-A1R interaction was observed with the agonists WIN55,212-2 and Delta(9)-THC and during endocannabinoid-mediated depolarization-induced suppression of excitation. A1R control of CB1Rs was stronger in the C57BL/6J mouse hippocampus, in which eADO levels were higher than in Sprague Dawley rats, and the eADO modulation of CB1R effects was absent in A1R knock-out mice. Since eADO levels and A1R activation are regulated by homeostatic, metabolic, and pathological factors, these data identify a mechanism in which CB1R function can be controlled by the brain adenosine system. Additionally, our data imply that caffeine may potentiate the effects of marijuana on hippocampal function.

  9. Presynaptic CB(1) cannabinoid receptors control frontocortical serotonin and glutamate release--species differences.

    PubMed

    Ferreira, Samira G; Teixeira, Filipe M; Garção, Pedro; Agostinho, Paula; Ledent, Catherine; Cortes, Luísa; Mackie, Ken; Köfalvi, Attila

    2012-07-01

    Both the serotonergic and endocannabinoid systems modulate frontocortical glutamate release; thus they are well positioned to participate in the pathogenesis of psychiatric disorders. With the help of fluorescent and confocal microscopy, we localized the CB(1) cannabinoid receptor (CB(1)R) in VGLUT1- and 2- (i.e. glutamatergic) and serotonin transporter- (i.e. serotonergic) -positive fibers and nerve terminals in the mouse and rat frontal cortex. CB(1)R activation by the synthetic agonists, WIN55212-2 (1 μM) and R-methanandamide (1 μM) inhibited the simultaneously measured evoked Ca(2+)-dependent release of [(14)C]glutamate and [(3)H]serotonin from frontocortical nerve terminals of Wistar rats, in a fashion sensitive to the CB(1)R antagonists, O-2050 (1 μM) and LY320135 (5 μM). CB(1)R agonists also inhibited the evoked release of [(14)C]glutamate in C57BL/6J mice in a reversible fashion upon washout. Interestingly, the evoked release of [(14)C]glutamate and [(3)H]serotonin was significantly greater in the CB(1)R knockout CD-1 mice. Furthermore, CB(1)R binding experiments revealed similar frontocortical CB(1)R density in the rat and the CD-1 mouse. Still, the evoked release of [(3)H]serotonin was modulated by neither CB(1)R agonists nor antagonists in wild-type CD-1 or C57BL/6J mice. Altogether, this is the first study to demonstrate functional presynaptic CB(1)Rs in frontocortical glutamatergic and serotonergic terminals, revealing species differences.

  10. Voluntary wheel running modulates glutamate receptor subunit gene expression and stress hormone release in Lewis rats.

    PubMed

    Makatsori, A; Duncko, R; Schwendt, M; Moncek, F; Johansson, B B; Jezova, D

    2003-07-01

    Lewis rats that are known to be addiction-prone, develop compulsive running if they have access to running wheels. The present experiments were aimed 1) to evaluate the activation of stress systems following chronic and acute voluntary wheel running in Lewis rats by measurement of hormone release and gene expression of neuropeptides related to hypothalamic-pituitary-adrenocortical (HPA) axis activity and 2) to test the hypothesis that wheel running as a combined model of addictive behavior and stress exposure is associated with modulation of ionotropic glutamate receptor subunits in the ventral tegmental area. Voluntary running for three weeks but not for one night resulted in a rise in plasma corticosterone and adrenocorticotropic hormone (ACTH) levels (p<0.05) compared to those in control rats. Principal component analysis revealed the relation between POMC gene expression in the intermediate pituitary and running rate. Acute exposure of animals to voluntary wheel running induced a significant decrease in alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptor GluR1 subunit mRNA levels (p<0.01), while repeated voluntary physical activity increased levels of GluR1 mRNA in the ventral tegmentum (p<0.05). Neither acute nor chronic wheel running influenced N-methyl-D-aspartate (NMDA) receptor subunit NR1 mRNA levels in the ventral tegmental area. Thus, the present study revealed changes in AMPA receptor subunit gene expression in a reward-related brain structure as well as an activation of HPA axis in response to compulsive wheel running in Lewis rats. It may be suggested that hormones of HPA axis and glutamate receptors belong to the factors that substantiate higher vulnerability to addictive behavior.

  11. The glutamatergic compounds sarcosine and N-acetylcysteine ameliorate prepulse inhibition deficits in metabotropic glutamate 5 receptor knockout mice

    PubMed Central

    Stoker, Astrid; Markou, Athina

    2010-01-01

    Rationale Mice lacking metabotropic glutamate receptors 5 (mGluR5) exhibit reduced glutamatergic function and behavioral abnormalities, including deficits in prepulse inhibition (PPI) of the startle response that may be relevant to schizophrenia. Thus, these mice are an animal model that may be used for preclinical evaluation of potentially new classes of antipsychotic compounds. Recent clinical studies have suggested several compounds that modulate glutamatergic transmission through distinct mechanisms, such as potentiation of the N-methyl-d-aspartate (NMDA) receptor glycine site, activation of group II mGluR, and activation of glutamate-cysteine antiporters, as being efficacious in the treatment of schizophrenia. Objectives The aim of this work is to evaluate the effects of sarcosine (a selective inhibitor of the glycine transporter 1 [GlyT1]), LY379268 (a group II mGluR agonist), and N-acetylcysteine (a cysteine prodrug that indirectly activates cystine-glutamate antiporters to increase glutamate levels in the extrasynaptic space) on PPI deficits in mGluR5 knockout mice. Results Sarcosine and N-acetylcysteine, but not LY379268, ameliorated PPI deficits in mGluR5 knockout mice. The ability of N-acetylcysteine to restore PPI deficits was not blocked by the group II mGluR antagonist LY341495, indicating that the effects of N-acetylcysteine were not attributable to activation of group II mGluRs by glutamate. Conclusions These findings provide evidence that the interactions between mGluR5 and NMDA receptors are involved in the regulation of PPI and suggest that activation of glutamate receptors, other than group II receptors, by increased endogenous glutamate transmission, may ameliorate the behavioral abnormalities associated with mGluR5 deficiency. PMID:20217053

  12. LTP requires a reserve pool of glutamate receptors independent of subunit type.

    PubMed

    Granger, Adam J; Shi, Yun; Lu, Wei; Cerpas, Manuel; Nicoll, Roger A

    2013-01-24

    Long-term potentiation (LTP) of synaptic transmission is thought to be an important cellular mechanism underlying memory formation. A widely accepted model posits that LTP requires the cytoplasmic carboxyl tail (C-tail) of the AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptor subunit GluA1. To find the minimum necessary requirement of the GluA1 C-tail for LTP in mouse CA1 hippocampal pyramidal neurons, we used a single-cell molecular replacement strategy to replace all endogenous AMPA receptors with transfected subunits. In contrast to the prevailing model, we found no requirement of the GluA1 C-tail for LTP. In fact, replacement with the GluA2 subunit showed normal LTP, as did an artificially expressed kainate receptor not normally found at these synapses. The only conditions under which LTP was impaired were those with markedly decreased AMPA receptor surface expression, indicating a requirement for a reserve pool of receptors. These results demonstrate the synapse's remarkable flexibility to potentiate with a variety of glutamate receptor subtypes, requiring a fundamental change in our thinking with regard to the core molecular events underlying synaptic plasticity.

  13. Distinct combinations of variant ionotropic glutamate receptors mediate thermosensation and hygrosensation in Drosophila

    PubMed Central

    Knecht, Zachary A; Silbering, Ana F; Ni, Lina; Klein, Mason; Budelli, Gonzalo; Bell, Rati; Abuin, Liliane; Ferrer, Anggie J; Samuel, Aravinthan DT; Benton, Richard; Garrity, Paul A

    2016-01-01

    Ionotropic Receptors (IRs) are a large subfamily of variant ionotropic glutamate receptors present across Protostomia. While these receptors are most extensively studied for their roles in chemosensory detection, recent work has implicated two family members, IR21a and IR25a, in thermosensation in Drosophila. Here we characterize one of the most evolutionarily deeply conserved receptors, IR93a, and show that it is co-expressed and functions with IR21a and IR25a to mediate physiological and behavioral responses to cool temperatures. IR93a is also co-expressed with IR25a and a distinct receptor, IR40a, in a discrete population of sensory neurons in the sacculus, a multi-chambered pocket within the antenna. We demonstrate that this combination of receptors is required for neuronal responses to dry air and behavioral discrimination of humidity differences. Our results identify IR93a as a common component of molecularly and cellularly distinct IR pathways important for thermosensation and hygrosensation in insects. DOI: http://dx.doi.org/10.7554/eLife.17879.001 PMID:27656904

  14. Morphine in combination with metabotropic glutamate receptor antagonists on schedule-controlled responding and thermal nociception.

    PubMed

    Fischer, Bradford D; Zimmerman, Eric I; Picker, Mitchell J; Dykstra, Linda A

    2008-02-01

    The present study examined the interactive effects of morphine in combination with metabotropic glutamate (mGlu) receptor antagonists on schedule-controlled responding and thermal nociception. Drug interaction data were examined with isobolographic and dose-addition analysis. Morphine, the mGlu1 receptor antagonist JNJ16259685 [(3,4-dihydro-2H-pyrano-[2,3-b]quinolin-7-yl)-(cis-4-methoxycyclohexyl)-methanone], the mGlu5 receptor antagonist MPEP [2-methyl-6-(phenylethynyl)pyridine hydrochloride], and the mGlu2/3 receptor antagonist LY341495 [(2S)-2-amino-2-[(1S,2S-2-carboxycycloprop-1-yl]-3-(xanth-9-yl) propanoic acid] all decreased rates of schedule-controlled responding. JNJ16259685/morphine, MPEP/morphine, and LY341495/morphine mixtures produced additive effects on this endpoint. Morphine also produced dose-dependent antinociception in the assay of thermal nociception, whereas JNJ16259685, MPEP, and LY341495 failed to produce an effect. In this assay, JNJ16259685 and LY341495 potentiated the antinociceptive effects of morphine, whereas MPEP/morphine mixtures produced additive effects. These results suggest that an mGlu1 and an mGlu2/3 receptor antagonist, but not an mGlu5 receptor antagonist, selectively enhance the antinociceptive effects of morphine. In addition, these data confirm that the behavioral effects of drug mixtures depend on the endpoint under study.

  15. Protective role for type 4 metabotropic glutamate receptors against ischemic brain damage.

    PubMed

    Moyanova, Slavianka G; Mastroiacovo, Federica; Kortenska, Lidia V; Mitreva, Rumiana G; Fardone, Erminia; Santolini, Ines; Sobrado, Mónica; Battaglia, Giuseppe; Bruno, Valeria; Nicoletti, Ferdinando; Ngomba, Richard T

    2011-04-01

    We examined the influence of type 4 metabotropic glutamate (mGlu4) receptors on ischemic brain damage using the permanent middle cerebral artery occlusion (MCAO) model in mice and the endothelin-1 (Et-1) model of transient focal ischemia in rats. Mice lacking mGlu4 receptors showed a 25% to 30% increase in infarct volume after MCAO as compared with wild-type littermates. In normal mice, systemic injection of the selective mGlu4 receptor enhancer, N-phenyl-7-(hydroxyimino)cyclopropa[b]chromen-1a-caboxamide (PHCCC; 10  mg/kg, subcutaneous, administered once 30  minutes before MCAO), reduced the extent of ischemic brain damage by 35% to 45%. The drug was inactive in mGlu4 receptor knockout mice. In the Et-1 model, PHCCC administered only once 20  minutes after ischemia reduced the infarct volume to a larger extent in the caudate/putamen than in the cerebral cortex. Ischemic rats treated with PHCCC showed a faster recovery of neuronal function, as shown by electrocorticographic recording and by a battery of specific tests, which assess sensorimotor deficits. These data indicate that activation of mGlu4 receptors limit the development of brain damage after permanent or transient focal ischemia. These findings are promising because selective mGlu4 receptor enhancers are under clinical development for the treatment of Parkinson's disease and other central nervous system disorders.

  16. Activation of spinal group I metabotropic glutamate receptors in rats evokes local glutamate release and spontaneous nociceptive behaviors: effects of 2-methyl-6-(phenylethynyl)-pyridine pretreatment.

    PubMed

    Lorrain, Daniel S; Correa, Lucia; Anderson, Jeffery; Varney, Mark

    2002-07-26

    Intrathecal (i.t.) administration of the group I metabotropic glutamate receptor (mGluR) agonist (RS)-3,5-dihydroxyphenylglycine ((RS)-3,5-DHPG) to rats produces an immediate display of spontaneous nociceptive behaviors (SNBs) persisting for up to 10 h after injection (NeuroReport 7 (1996) 2743). The mechanisms underlying these behavioral effects are not entirely understood but may include enhanced release of glutamate within the dorsal horn of the spinal cord. The current experiments used microdialysis in awake moving animals to test: (1), whether i.t. (S)-3,5-DHPG increases the local release of glutamate at doses that also induce SNBs; and (2), whether the effects on glutamate release (as well as SNBs) can be blocked by pretreatment with the mGluR5 selective antagonist 2-methyl-6-(phenylethynyl)-pyridine (MPEP). Male Sprague-Dawley rats were implanted with a microdialysis probe inserted into the i.t. space of the spinal cord (J. Neurosci. Methods 62 (1995) 43) and then tested under i.t. drug conditions (0.01, 0.1 and 1 mM (S)-3,5-DHPG) following a 2-3 day recovery period. As predicted, local application of (S)-3,5-DHPG via the microdialysis probe increased the release of glutamate in a dose-dependent manner. Significant SNBs were also noted in the 0.1 and 1 mM groups in a manner paralleling the onset and duration of the glutamate response. Pretreatment with MPEP (55 mg/kg, intraperitoneally) blocked glutamate release to the 0.1 mM dose of (S)-3,5-DHPG, and also decreased the proportion of animals displaying SNBs in this dose group. No effects of MPEP were seen against the higher dose of (S)-3,5-DHPG (1 mM). These results suggest that stimulation of spinal mGluR5 leads to glutamate release within the spinal cord, a response that may in part account for the nociceptive behaviors evoked by i.t. (S)-3,5-DHPG.

  17. Deletion of glutamate delta-1 receptor in mouse leads to aberrant emotional and social behaviors.

    PubMed

    Yadav, Roopali; Gupta, Subhash C; Hillman, Brandon G; Bhatt, Jay M; Stairs, Dustin J; Dravid, Shashank M

    2012-01-01

    The delta family of ionotropic glutamate receptors consists of glutamate δ1 (GluD1) and glutamate δ2 (GluD2) receptors. While the role of GluD2 in the regulation of cerebellar physiology is well understood, the function of GluD1 in the central nervous system remains elusive. We demonstrate for the first time that deletion of GluD1 leads to abnormal emotional and social behaviors. We found that GluD1 knockout mice (GluD1 KO) were hyperactive, manifested lower anxiety-like behavior, depression-like behavior in a forced swim test and robust aggression in the resident-intruder test. Chronic lithium rescued the depression-like behavior in GluD1 KO. GluD1 KO mice also manifested deficits in social interaction. In the sociability test, GluD1 KO mice spent more time interacting with an inanimate object compared to a conspecific mouse. D-Cycloserine (DCS) administration was able to rescue social interaction deficits observed in GluD1 KO mice. At a molecular level synaptoneurosome preparations revealed lower GluA1 and GluA2 subunit expression in the prefrontal cortex and higher GluA1, GluK2 and PSD95 expression in the amygdala of GluD1 KO. Moreover, DCS normalized the lower GluA1 expression in prefrontal cortex of GluD1 KO. We propose that deletion of GluD1 leads to aberrant circuitry in prefrontal cortex and amygdala owing to its potential role in presynaptic differentiation and synapse formation. Furthermore, these findings are in agreement with the human genetic studies suggesting a strong association of GRID1 gene with several neuropsychiatric disorders including schizophrenia, bipolar disorder, autism spectrum disorders and major depressive disorder.

  18. [60]Fullerene derivative modulates adenosine and metabotropic glutamate receptors gene expression: a possible protective effect against hypoxia

    PubMed Central

    2014-01-01

    Background Glutamate, the main excitatory neurotransmitter, is involved in learning and memory processes but at higher concentration results excitotoxic causing degeneration and neuronal death. Adenosine is a nucleoside that exhibit neuroprotective effects by modulating of glutamate release. Hypoxic and related oxidative conditions, in which adenosine and metabotropic glutamate receptors are involved, have been demonstrated to contribute to neurodegenerative processes occurring in certain human pathologies. Results Human neuroblastoma cells (SH-SY5Y) were used to evaluate the long time (24, 48 and 72 hours) effects of a [60]fullerene hydrosoluble derivative (t3ss) as potential inhibitor of hypoxic insult. Low oxygen concentration (5% O2) caused cell death, which was avoided by t3ss exposure in a concentration dependent manner. In addition, gene expression analysis by real time PCR of adenosine A1, A2A and A2B and metabotropic glutamate 1 and 5 receptors revealed that t3ss significantly increased A1 and mGlu1 expression in hypoxic conditions. Moreover, t3ss prevented the hypoxia-induced increase in A2A mRNA expression. Conclusions As t3ss causes overexpression of adenosine A1 and metabotropic glutamate receptors which have been shown to be neuroprotective, our results point to a radical scavenger protective effect of t3ss through the enhancement of these neuroprotective receptors expression. Therefore, the utility of these nanoparticles as therapeutic target to avoid degeneration and cell death of neurodegenerative diseases is suggested. PMID:25123848

  19. Molecular Basis for Modulation of Metabotropic Glutamate Receptors and Their Drug Actions by Extracellular Ca2+

    PubMed Central

    Zou, Juan; Jiang, Jason Y.; Yang, Jenny J.

    2017-01-01

    Metabotropic glutamate receptors (mGluRs) associated with the slow phase of the glutamatergic signaling pathway in neurons of the central nervous system have gained importance as drug targets for chronic neurodegenerative diseases. While extracellular Ca2+ was reported to exhibit direct activation and modulation via an allosteric site, the identification of those binding sites was challenged by weak binding. Herein, we review the discovery of extracellular Ca2+ in regulation of mGluRs, summarize the recent developments in probing Ca2+ binding and its co-regulation of the receptor based on structural and biochemical analysis, and discuss the molecular basis for Ca2+ to regulate various classes of drug action as well as its importance as an allosteric modulator in mGluRs. PMID:28335551

  20. Synchronized oscillations in interneuron networks driven by metabotropic glutamate receptor activation

    NASA Astrophysics Data System (ADS)

    Whittington, Miles A.; Traub, Roger D.; Jefferys, John G. R.

    1995-02-01

    PARTIALLY synchronous 40-Hz oscillations of cortical neurons have been implicated in cognitive function. Specifically, coherence of these oscillations between different parts of the cortex may provide conjunctive properties1,2 to solve the 'binding problem' associating features detected by the cortex into unified perceived objects. Here we report an emergent 40-Hz oscillation in networks of inhibitory neurons connected by synapses using GABAA (γ-aminobutyric acid) receptors in slices of rat hippocampus and neocortex. These network inhibitory postsynaptic potential oscillations occur in response to the activation of metabotropic glutamate receptors. The oscillations can entrain pyramidal cell discharges. The oscillation frequency is determined both by the net excitation of interneurons and by the kinetics of the inhibitory postsynaptic potentials between them. We propose that interneuron network oscillations, in conjunction with intrinsic membrane resonances and long-loop (such as thalamocortical) interactions, contribute to 40-Hz rhythms in vivo.

  1. Enhancement of CA3 hippocampal network activity by activation of group II metabotropic glutamate receptors.

    PubMed

    Ster, Jeanne; Mateos, José María; Grewe, Benjamin Friedrich; Coiret, Guyllaume; Corti, Corrado; Corsi, Mauro; Helmchen, Fritjof; Gerber, Urs

    2011-06-14

    Impaired function or expression of group II metabotropic glutamate receptors (mGluRIIs) is observed in brain disorders such as schizophrenia. This class of receptor is thought to modulate activity of neuronal circuits primarily by inhibiting neurotransmitter release. Here, we characterize a postsynaptic excitatory response mediated by somato-dendritic mGluRIIs in hippocampal CA3 pyramidal cells and in stratum oriens interneurons. The specific mGluRII agonists DCG-IV or LCCG-1 induced an inward current blocked by the mGluRII antagonist LY341495. Experiments with transgenic mice revealed a significant reduction of the inward current in mGluR3(-/-) but not in mGluR2(-/-) mice. The excitatory response was associated with periods of synchronized activity at theta frequency. Furthermore, cholinergically induced network oscillations exhibited decreased frequency when mGluRIIs were blocked. Thus, our data indicate that hippocampal responses are modulated not only by presynaptic mGluRIIs that reduce glutamate release but also by postsynaptic mGluRIIs that depolarize neurons and enhance CA3 network activity.

  2. Clustered coding variants in the glutamate receptor complexes of individuals with schizophrenia and bipolar disorder.

    PubMed

    Frank, René A W; McRae, Allan F; Pocklington, Andrew J; van de Lagemaat, Louie N; Navarro, Pau; Croning, Mike D R; Komiyama, Noboru H; Bradley, Sophie J; Challiss, R A John; Armstrong, J Douglas; Finn, Robert D; Malloy, Mary P; MacLean, Alan W; Harris, Sarah E; Starr, John M; Bhaskar, Sanjeev S; Howard, Eleanor K; Hunt, Sarah E; Coffey, Alison J; Ranganath, Venkatesh; Deloukas, Panos; Rogers, Jane; Muir, Walter J; Deary, Ian J; Blackwood, Douglas H; Visscher, Peter M; Grant, Seth G N

    2011-04-29

    Current models of schizophrenia and bipolar disorder implicate multiple genes, however their biological relationships remain elusive. To test the genetic role of glutamate receptors and their interacting scaffold proteins, the exons of ten glutamatergic 'hub' genes in 1304 individuals were re-sequenced in case and control samples. No significant difference in the overall number of non-synonymous single nucleotide polymorphisms (nsSNPs) was observed between cases and controls. However, cluster analysis of nsSNPs identified two exons encoding the cysteine-rich domain and first transmembrane helix of GRM1 as a risk locus with five mutations highly enriched within these domains. A new splice variant lacking the transmembrane GPCR domain of GRM1 was discovered in the human brain and the GRM1 mutation cluster could perturb the regulation of this variant. The predicted effect on individuals harbouring multiple mutations distributed in their ten hub genes was also examined. Diseased individuals possessed an increased load of deleteriousness from multiple concurrent rare and common coding variants. Together, these data suggest a disease model in which the interplay of compound genetic coding variants, distributed among glutamate receptors and their interacting proteins, contribute to the pathogenesis of schizophrenia and bipolar disorders.

  3. Estrogen Receptor β Activation Rapidly Modulates Male Sexual Motivation through the Transactivation of Metabotropic Glutamate Receptor 1a

    PubMed Central

    Seredynski, Aurore L.; Balthazart, Jacques; Ball, Gregory F.

    2015-01-01

    In addition to the transcriptional activity of their liganded nuclear receptors, estrogens, such as estradiol (E2), modulate cell functions, and consequently physiology and behavior, within minutes through membrane-initiated events. The membrane-associated receptors (mERs) underlying the acute effects of estrogens on behavior have mostly been documented in females where active estrogens are thought to be of ovarian origin. We determined here, by acute intracerebroventricular injections of specific agonists and antagonists, the type(s) of mERs that modulate rapid effects of brain-derived estrogens on sexual motivation in male Japanese quail. Brain aromatase blockade acutely inhibited sexual motivation. Diarylpropionitrile (DPN), an estrogen receptor β (ERβ)-specific agonist, and to a lesser extent 17α-estradiol, possibly acting through ER-X, prevented this effect. In contrast, drugs targeting ERα (PPT and MPP), GPR30 (G1 and G15), and the Gq-mER (STX) did not affect sexual motivation. The mGluR1a antagonist LY367385 significantly inhibited sexual motivation but mGluR2/3 and mGluR5 antagonists were ineffective. LY367385 also blocked the behavioral restoration induced by E2 or DPN, providing functional evidence that ERβ interacts with metabotropic glutamate receptor 1a (mGluR1a) signaling to acutely regulate male sexual motivation. Together these results show that ERβ plays a key role in sexual behavior regulation and the recently uncovered cooperation between mERs and mGluRs is functional in males where it mediates the acute effects of estrogens produced centrally in response to social stimuli. The presence of an ER–mGluR interaction in birds suggests that this mechanism emerged relatively early in vertebrate history and is well conserved. SIGNIFICANCE STATEMENT The membrane-associated receptors underlying the acute effects of estrogens on behavior have mostly been documented in females, where active estrogens are thought to be of ovarian origin. Using acute

  4. Estrogen Receptor β Activation Rapidly Modulates Male Sexual Motivation through the Transactivation of Metabotropic Glutamate Receptor 1a.

    PubMed

    Seredynski, Aurore L; Balthazart, Jacques; Ball, Gregory F; Cornil, Charlotte A

    2015-09-23

    In addition to the transcriptional activity of their liganded nuclear receptors, estrogens, such as estradiol (E2), modulate cell functions, and consequently physiology and behavior, within minutes through membrane-initiated events. The membrane-associated receptors (mERs) underlying the acute effects of estrogens on behavior have mostly been documented in females where active estrogens are thought to be of ovarian origin. We determined here, by acute intracerebroventricular injections of specific agonists and antagonists, the type(s) of mERs that modulate rapid effects of brain-derived estrogens on sexual motivation in male Japanese quail. Brain aromatase blockade acutely inhibited sexual motivation. Diarylpropionitrile (DPN), an estrogen receptor β (ERβ)-specific agonist, and to a lesser extent 17α-estradiol, possibly acting through ER-X, prevented this effect. In contrast, drugs targeting ERα (PPT and MPP), GPR30 (G1 and G15), and the Gq-mER (STX) did not affect sexual motivation. The mGluR1a antagonist LY367385 significantly inhibited sexual motivation but mGluR2/3 and mGluR5 antagonists were ineffective. LY367385 also blocked the behavioral restoration induced by E2 or DPN, providing functional evidence that ERβ interacts with metabotropic glutamate receptor 1a (mGluR1a) signaling to acutely regulate male sexual motivation. Together these results show that ERβ plays a key role in sexual behavior regulation and the recently uncovered cooperation between mERs and mGluRs is functional in males where it mediates the acute effects of estrogens produced centrally in response to social stimuli. The presence of an ER-mGluR interaction in birds suggests that this mechanism emerged relatively early in vertebrate history and is well conserved. Significance statement: The membrane-associated receptors underlying the acute effects of estrogens on behavior have mostly been documented in females, where active estrogens are thought to be of ovarian origin. Using acute

  5. Anticonvulsant activity of artificial sweeteners: a structural link between sweet-taste receptor T1R3 and brain glutamate receptors.

    PubMed

    Talevi, Alan; Enrique, Andrea V; Bruno-Blanch, Luis E

    2012-06-15

    A virtual screening campaign based on application of a topological discriminant function capable of identifying novel anticonvulsant agents indicated several widely-used artificial sweeteners as potential anticonvulsant candidates. Acesulfame potassium, cyclamate and saccharin were tested in the Maximal Electroshock Seizure model (mice, ip), showing moderate anticonvulsant activity. We hypothesized a probable structural link between the receptor responsible of sweet taste and anticonvulsant molecular targets. Bioinformatic tools confirmed a highly significant sequence-similarity between taste-related protein T1R3 and several metabotropic glutamate receptors from different species, including glutamate receptors upregulated in epileptogenesis and certain types of epilepsy.

  6. Postsynaptic glutamate receptors regulate local BMP signaling at the Drosophila neuromuscular junction.

    PubMed

    Sulkowski, Mikolaj; Kim, Young-Jun; Serpe, Mihaela

    2014-01-01

    Effective communication between pre- and postsynaptic compartments is required for proper synapse development and function. At the Drosophila neuromuscular junction (NMJ), a retrograde BMP signal functions to promote synapse growth, stability and homeostasis and coordinates the growth of synaptic structures. Retrograde BMP signaling triggers accumulation of the pathway effector pMad in motoneuron nuclei and at synaptic termini. Nuclear pMad, in conjunction with transcription factors, modulates the expression of target genes and instructs synaptic growth; a role for synaptic pMad remains to be determined. Here, we report that pMad signals are selectively lost at NMJ synapses with reduced postsynaptic sensitivities. Despite this loss of synaptic pMad, nuclear pMad persisted in motoneuron nuclei, and expression of BMP target genes was unaffected, indicating a specific impairment in pMad production/maintenance at synaptic termini. During development, synaptic pMad accumulation followed the arrival and clustering of ionotropic glutamate receptors (iGluRs) at NMJ synapses. Synaptic pMad was lost at NMJ synapses developing at suboptimal levels of iGluRs and Neto, an auxiliary subunit required for functional iGluRs. Genetic manipulations of non-essential iGluR subunits revealed that synaptic pMad signals specifically correlated with the postsynaptic type-A glutamate receptors. Altering type-A receptor activities via protein kinase A (PKA) revealed that synaptic pMad depends on the activity and not the net levels of postsynaptic type-A receptors. Thus, synaptic pMad functions as a local sensor for NMJ synapse activity and has the potential to coordinate synaptic activity with a BMP retrograde signal required for synapse growth and homeostasis.

  7. Structure of metabotropic glutamate receptor C-terminal domains in contact with interacting proteins.

    PubMed

    Enz, Ralf

    2012-01-01

    Metabotropic glutamate receptors (mGluRs) regulate intracellular signal pathways that control several physiological tasks, including neuronal excitability, learning, and memory. This is achieved by the formation of synaptic signal complexes, in which mGluRs assemble with functionally related proteins such as enzymes, scaffolds, and cytoskeletal anchor proteins. Thus, mGluR associated proteins actively participate in the regulation of glutamatergic neurotransmission. Importantly, dysfunction of mGluRs and interacting proteins may lead to impaired signal transduction and finally result in neurological disorders, e.g., night blindness, addiction, epilepsy, schizophrenia, autism spectrum disorders and Parkinson's disease. In contrast to solved crystal structures of extracellular N-terminal domains of some mGluR types, only a few studies analyzed the conformation of intracellular receptor domains. Intracellular C-termini of most mGluR types are subject to alternative splicing and can be further modified by phosphorylation and SUMOylation. In this way, diverse interaction sites for intracellular proteins that bind to and regulate the glutamate receptors are generated. Indeed, most of the known mGluR binding partners interact with the receptors' C-terminal domains. Within the last years, different laboratories analyzed the structure of these domains and described the geometry of the contact surface between mGluR C-termini and interacting proteins. Here, I will review recent progress in the structure characterization of mGluR C-termini and provide an up-to-date summary of the geometry of these domains in contact with binding partners.

  8. Effects of ionotropic glutamate receptor antagonists on rat dural artery diameter in an intravital microscopy model

    PubMed Central

    Chan, KY; Gupta, S; de Vries, R; Danser, AHJ; Villalón, CM; Muñoz-Islas, E; Maassen Van Den Brink, A

    2010-01-01

    Background and purpose: During migraine, trigeminal nerves may release calcitonin gene-related peptide (CGRP), inducing cranial vasodilatation and central nociception; hence, trigeminal inhibition or blockade of craniovascular CGRP receptors may prevent this vasodilatation and abort migraine headache. Several preclinical studies have shown that glutamate receptor antagonists affect the pathophysiology of migraine. This study investigated whether antagonists of NMDA (ketamine and MK801), AMPA (GYKI52466) and kainate (LY466195) glutamate receptors affected dural vasodilatation induced by α-CGRP, capsaicin and periarterial electrical stimulation in rats, using intravital microscopy. Experimental approach: Male Sprague-Dawley rats were anaesthetized and the overlying bone was thinned to visualize the dural artery. Then, vasodilator responses to exogenous (i.v. α-CGRP) and endogenous (released by i.v. capsaicin and periarterial electrical stimulation) CGRP were elicited in the absence or presence of the above antagonists. Key results: α-CGRP, capsaicin and periarterial electrical stimulation increased dural artery diameter. Ketamine and MK801 inhibited the vasodilator responses to capsaicin and electrical stimulation, while only ketamine attenuated those to α-CGRP. In contrast, GYKI52466 only attenuated the vasodilatation to exogenous α-CGRP, while LY466195 did not affect the vasodilator responses to endogenous or exogenous CGRP. Conclusions and implications: Although GYKI52466 has not been tested clinically, our data suggest that it would not inhibit migraine via vascular mechanisms. Similarly, the antimigraine efficacy of LY466195 seems unrelated to vascular CGRP-mediated pathways and/or receptors. In contrast, the cranial vascular effects of ketamine and MK801 may represent a therapeutic mechanism, although the same mechanism might contribute, peripherally, to cardiovascular side effects. PMID:20590623

  9. The Notch ligand E3 ligase, Mind Bomb1, regulates glutamate receptor localization in Drosophila

    PubMed Central

    Sturgeon, Morgan; Davis, Dustin; Albers, Amanda; Beatty, Derek; Austin, Rik; Ferguson, Matt; Tounsel, Brittany; Liebl, Faith L. W.

    2015-01-01

    The postsynaptic density (PSD) is a protein-rich network important for the localization of postsynaptic glutamate receptors (GluRs) and for signaling downstream of these receptors. Although hundreds of PSD proteins have been identified, many are functionally uncharacterized. We conducted a reverse genetic screen for mutations that affected GluR localization using Drosophila genes that encode homologs of mammalian PSD proteins. 42.8% of the mutants analyzed exhibited a significant change in GluR localization at the third instar larval neuromuscular junction (NMJ), a model synapse that expresses homologs of AMPA receptors. We identified the E3 ubiquitin ligase, Mib1, which promotes Notch signaling, as a regulator of synaptic GluR localization. Mib1 positively regulates the localization of the GluR subunits GluRIIA, GluRIIB, and GluRIIC. Mutations in mib1 and ubiquitous expression of Mib1 that lacks its ubiquitin ligase activity result in the loss of synaptic GluRIIA-containing receptors. In contrast, overexpression of Mib1 in all tissues increases postsynaptic levels of GluRIIA. Cellular levels of Mib1 are also important for the structure of the presynaptic motor neuron. While deficient Mib1 signaling leads to overgrowth of the NMJ, ubiquitous overexpression of Mib1 results in a reduction in the number of presynaptic motor neuron boutons and branches. These synaptic changes may be secondary to attenuated glutamate release from the presynaptic motor neuron in mib1 mutants as mib1 mutants exhibit significant reductions in the vesicle-associated protein cysteine string protein and in the frequency of spontaneous neurotransmission. PMID:26596173

  10. The Notch ligand E3 ligase, Mind Bomb1, regulates glutamate receptor localization in Drosophila.

    PubMed

    Sturgeon, Morgan; Davis, Dustin; Albers, Amanda; Beatty, Derek; Austin, Rik; Ferguson, Matt; Tounsel, Brittany; Liebl, Faith L W

    2016-01-01

    The postsynaptic density (PSD) is a protein-rich network important for the localization of postsynaptic glutamate receptors (GluRs) and for signaling downstream of these receptors. Although hundreds of PSD proteins have been identified, many are functionally uncharacterized. We conducted a reverse genetic screen for mutations that affected GluR localization using Drosophila genes that encode homologs of mammalian PSD proteins. 42.8% of the mutants analyzed exhibited a significant change in GluR localization at the third instar larval neuromuscular junction (NMJ), a model synapse that expresses homologs of AMPA receptors. We identified the E3 ubiquitin ligase, Mib1, which promotes Notch signaling, as a regulator of synaptic GluR localization. Mib1 positively regulates the localization of the GluR subunits GluRIIA, GluRIIB, and GluRIIC. Mutations in mib1 and ubiquitous expression of Mib1 that lacks its ubiquitin ligase activity result in the loss of synaptic GluRIIA-containing receptors. In contrast, overexpression of Mib1 in all tissues increases postsynaptic levels of GluRIIA. Cellular levels of Mib1 are also important for the structure of the presynaptic motor neuron. While deficient Mib1 signaling leads to overgrowth of the NMJ, ubiquitous overexpression of Mib1 results in a reduction in the number of presynaptic motor neuron boutons and branches. These synaptic changes may be secondary to attenuated glutamate release from the presynaptic motor neuron in mib1 mutants as mib1 mutants exhibit significant reductions in the vesicle-associated protein cysteine string protein and in the frequency of spontaneous neurotransmission.

  11. Driving Cellular Plasticity and Survival Through the Signal Transduction Pathways of Metabotropic Glutamate Receptors

    PubMed Central

    Maiese, Kenneth; Chong, Zhao Zhong; Li, Faqi

    2008-01-01

    Metabotropic glutamate receptors (mGluRs) share a common molecular morphology with other G protein–linked receptors, but there expression throughout the mammalian nervous system places these receptors as essential mediators not only for the initial development of an organism, but also for the vital determination of a cell’s fate during many disorders in the nervous system that include amyotrophic lateral sclerosis, Parkinson’s disease, Alzheimer’s disease, Huntington’s disease, Multiple Sclerosis, epilepsy, trauma, and stroke. Given the ubiquitous distribution of these receptors, the mGluR system impacts upon neuronal, vascular, and glial cell function and is activated by a wide variety of stimuli that includes neurotransmitters, peptides, hormones, growth factors, ions, lipids, and light. Employing signal transduction pathways that can modulate both excitatory and inhibitory responses, the mGluR system drives a spectrum of cellular pathways that involve protein kinases, endonucleases, cellular acidity, energy metabolism, mitochondrial membrane potential, caspases, and specific mitogen-activated protein kinases. Ultimately these pathways can converge to regulate genomic DNA degradation, membrane phosphatidylserine (PS) residue exposure, and inflammatory microglial activation. As we continue to push the envelope for our understanding of this complex and critical family of metabotropic receptors, we should be able to reap enormous benefits for both clinical disease as well as our understanding of basic biology in the nervous system. PMID:16375723

  12. Place field stability requires the metabotropic glutamate receptor, mGlu5

    PubMed Central

    Zhang, Sijie; Manahan-Vaughan, Denise

    2014-01-01

    The metabotropic glutamate (mGlu) receptors are critically involved in enabling the persistency of forms of synaptic plasticity that are believed to underlie hippocampus-dependent memory. These receptors and in particular, mGlu5, are also required for hippocampus-dependent learning and memory. In the hippocampus, synaptic plasticity is one of the mechanisms by which spatial information may be represented. Another mechanism involves increased firing of place cells. Place cells increase their firing activity when an animal is in a specific spatial location. Inhibition of factors that are essential for synaptic plasticity, such as N-methyl-d-aspartate receptors or protein synthesis, also impair place cell activity. This raises the question as to whether mGlu receptors, that are so important for synaptic plasticity and spatial memory, are also important for place cell encoding. We examined location-dependent place cell firing i.e. place fields. We observed that antagonism of mGlu5, using 2-methyl-6-(phenylethynyl) pyridine (MPEP) had no effect on place field profiles in a familiar environment. However, in a novel environment mGlu5-antagonism affected long-term place field stability, reduced place cell firing and spatial information. These data strongly suggest a role for mGlu5 in the mechanisms underlying informational content and long-term stability of place fields, and add to evidence supporting the importance of these receptors for hippocampal function. PMID:24910241

  13. Two-photon brightness of azobenzene photoswitches designed for glutamate receptor optogenetics

    PubMed Central

    Carroll, Elizabeth C.; Berlin, Shai; Levitz, Joshua; Kienzler, Michael A.; Yuan, Zhe; Madsen, Dorte; Larsen, Delmar S.; Isacoff, Ehud Y.

    2015-01-01

    Mammalian neurotransmitter-gated receptors can be conjugated to photoswitchable tethered ligands (PTLs) to enable photoactivation, or photoantagonism, while preserving normal function at neuronal synapses. “MAG” PTLs for ionotropic and metabotropic glutamate receptors (GluRs) are based on an azobenzene photoswitch that is optimally switched into the liganding state by blue or near-UV light, wavelengths that penetrate poorly into the brain. To facilitate deep-tissue photoactivation with near-infrared light, we measured the efficacy of two-photon (2P) excitation for two MAG molecules using nonlinear spectroscopy. Based on quantitative characterization, we find a recently designed second generation PTL, l-MAG0460, to have a favorable 2P absorbance peak at 850 nm, enabling efficient 2P activation of the GluK2 kainate receptor, LiGluR. We also achieve 2P photoactivation of a metabotropic receptor, LimGluR3, with a new mGluR-specific PTL, d-MAG0460. 2P photoswitching is efficiently achieved using digital holography to shape illumination over single somata of cultured neurons. Simultaneous Ca2+-imaging reports on 2P photoswitching in multiple cells with high temporal resolution. The combination of electrophysiology or Ca2+ imaging with 2P activation by optical wavefront shaping should make second generation PTL-controlled receptors suitable for studies of intact neural circuits. PMID:25653339

  14. A profile of the behavioral changes produced by facilitation of AMPA-type glutamate receptors.

    PubMed

    Davis, C M; Moskovitz, B; Nguyen, M A; Tran, B B; Arai, A; Lynch, G; Granger, R

    1997-09-01

    A newly developed group of benzoylpiperidine drugs that enhance AMPA-receptor-gated currents ("ampakines") has been shown to improve memory encoding in rats across a variety of experimental paradigms. The present experiments were intended to i) provide a partial profile of the behavioral changes produced by ampakines, ii) test if two ampakines (BDP-12 and BDP-20) that differ significantly in their effects on AMPA receptor kinetics produce similar behavioral profiles, and iii) determine if physiological potency is reflected in behavioral potency. BDP-20 reduced two measures of exploratory activity in aged rats but increased speed of performance in a radial maze; the drug also caused substantially improved retention of spatial information. These results are similar to those obtained with BDP-12, an analog that differs from BDP-20 in its effects on ligand binding to the AMPA receptor and on the physiological responses of the receptors to glutamate. BDP-20 was approximately ten-fold more potent in behavioral effects than BDP-12, which agrees with the relative potencies of the two drugs as assessed with excised patches and excitatory synaptic responses. These findings indicate that ampakines, though differing in their effects on AMPA-receptor-mediated responses, have similar effects at the behavioral level.

  15. Allosteric Modulation of Metabotropic Glutamate Receptors: Structural Insights and Therapeutic Potential

    PubMed Central

    Gregory, Karen J.; Dong, Elizabeth N.; Meiler, Jens; Conn, P. Jeffrey

    2010-01-01

    Allosteric modulation of G protein-coupled receptors (GPCRs) represents a novel approach to the development of probes and therapeutics that is expected to enable subtype-specific regulation of central nervous system target receptors. The metabotropic glutamate receptors (mGlus) are class C GPCRs that play important neuromodulatory roles throughout the brain, as such they are attractive targets for therapeutic intervention for a number of psychiatric and neurological disorders including anxiety, depression, Fragile X Syndrome, Parkinson’s disease and schizophrenia. Over the last fifteen years, selective allosteric modulators have been identified for many members of the mGlu family. The vast majority of these allosteric modulators are thought to bind within the transmembrane-spanning domains of the receptors to enhance or inhibit functional responses. A combination of mutagenesis-based studies and pharmacological approaches are beginning to provide a better understanding of mGlu allosteric sites. Collectively, when mapped onto a homology model of the different mGlu subtypes based on the β2-adrenergic receptor, the previous mutagenesis studies suggest commonalities in the location of allosteric sites across different members of the mGlu family. In addition, there is evidence for multiple allosteric binding pockets within the transmembrane region that can interact to modulate one another. In the absence of a class C GPCR crystal structure, this approach has shown promise with respect to the interpretation of mutagenesis data and understanding structure-activity relationships of allosteric modulator pharmacophores. PMID:20637216

  16. A Toolkit for Orthogonal and in vivo Optical Manipulation of Ionotropic Glutamate Receptors

    PubMed Central

    Levitz, Joshua; Popescu, Andrei T.; Reiner, Andreas; Isacoff, Ehud Y.

    2016-01-01

    The ability to optically manipulate specific neuronal signaling proteins with genetic precision paves the way for the dissection of their roles in brain function, behavior, and disease. Chemical optogenetic control with photoswitchable tethered ligands (PTLs) enables rapid, reversible and reproducible activation or block of specific neurotransmitter-gated receptors and ion channels in specific cells. In this study, we further engineered and characterized the light-activated GluK2 kainate receptor, LiGluR, to develop a toolbox of LiGluR variants. Low-affinity LiGluRs allow for efficient optical control of GluK2 while removing activation by native glutamate, whereas variant RNA edited versions enable the synaptic role of receptors with high and low Ca2+ permeability to be assessed and spectral variant photoswitches provide flexibility in illumination. Importantly, we establish that LiGluR works efficiently in the cortex of awake, adult mice using standard optogenetic techniques, thus opening the door to probing the role of specific synaptic receptors and cellular signals in the neural circuit operations of the mammalian brain in normal conditions and in disease. The principals developed in this study are widely relevant to the engineering and in vivo use of optically controllable proteins, including other neurotransmitter receptors. PMID:26869877

  17. Metabotrobic Glutamate Receptor mGluR4 as a Novel Target for Parkinson’s Disease.

    DTIC Science & Technology

    1999-10-01

    Parkinson’s disease (PD) are associated with a loss of substantia nigra dopaminergic neurons involved in modulation of function of the basal ganglia (BG) . This report describes our progress in understanding the role of metabotropic glutamate receptors (mGluRs) as a novel target for the treatment of PD. Specifically, our aims are to localize mGluR4 in rat and monkey basal ganglia structures, to determine the role of this receptor vs. other subtypes in mediating the electrophysiological effects of glutamate in rat brain slices, and to determine the efficacy of drugs

  18. Glutamate transporter type 3 attenuates the activation of N-methyl-D-aspartate receptors co-expressed in Xenopus oocytes.

    PubMed

    Zuo, Zhiyi; Fang, Hongyu

    2005-06-01

    We studied the regulation of N-methy-D-aspartate receptor (NMDAR) current/activation by glutamate transporter type 3 (EAAT3), a neuronal EAAT in vivo, in the restricted extracellular space of a biological model. This model involved co-expressing EAAT3 and NMDAR (composed of NMDAR1-1a and NMDAR2A) in Xenopus oocytes. The NMDAR current was reduced in the co-expression oocytes but not in oocytes expressing NMDAR only when the flow of glutamate-containing superfusate was stopped. The degree of this current reduction was glutamate concentration-dependent. No reduction of NMDAR current was observed in Na+-free solution or when NMDA, a non-substrate for EAATs, was used as the agonist for NMDAR. In the continuous flow experiments, the dose-response curve of glutamate-induced current was shifted to the right-hand side in co-expression oocytes compared with oocytes expressing NMDAR alone. The degree of this shift depended on the abundance of EAAT3 in the co-expression oocytes. Thus, the glutamate concentrations sensed by NMDAR locally were lower than those in the superfusates. These results suggest that EAAT3 regulates the amplitude of NMDAR currents at pre-saturated concentrations of glutamate to EAAT3. Thus, EAATs, by rapidly regulating glutamate concentrations near NMDAR, modulate NMDAR current/activation.

  19. Metabotropic glutamate receptor signaling is required for NMDA receptor-dependent ocular dominance plasticity and LTD in visual cortex

    PubMed Central

    Sidorov, Michael S.; Kaplan, Eitan S.; Osterweil, Emily K.; Lindemann, Lothar; Bear, Mark F.

    2015-01-01

    A feature of early postnatal neocortical development is a transient peak in signaling via metabotropic glutamate receptor 5 (mGluR5). In visual cortex, this change coincides with increased sensitivity of excitatory synapses to monocular deprivation (MD). However, loss of visual responsiveness after MD occurs via mechanisms revealed by the study of long-term depression (LTD) of synaptic transmission, which in layer 4 is induced by acute activation of NMDA receptors (NMDARs) rather than mGluR5. Here we report that chronic postnatal down-regulation of mGluR5 signaling produces coordinated impairments in both NMDAR-dependent LTD in vitro and ocular dominance plasticity in vivo. The data suggest that ongoing mGluR5 signaling during a critical period of postnatal development establishes the biochemical conditions that are permissive for activity-dependent sculpting of excitatory synapses via the mechanism of NMDAR-dependent LTD. PMID:26417096

  20. Role of the NR2A/2B subunits of the N-methyl-D-aspartate receptor in glutamate-induced glutamic acid decarboxylase alteration in cortical GABAergic neurons in vitro.

    PubMed

    Monnerie, H; Hsu, F-C; Coulter, D A; Le Roux, P D

    2010-12-29

    The vulnerability of brain neuronal cell subpopulations to neurologic insults varies greatly. Among cells that survive a pathological insult, for example ischemia or brain trauma, some may undergo morphological and/or biochemical changes that may compromise brain function. The present study is a follow-up of our previous studies that investigated the effect of glutamate-induced excitotoxicity on the GABA synthesizing enzyme glutamic acid decarboxylase (GAD65/67)'s expression in surviving DIV 11 cortical GABAergic neurons in vitro [Monnerie and Le Roux, (2007) Exp Neurol 205:367-382, (2008) Exp Neurol 213:145-153]. An N-methyl-D-aspartate receptor (NMDAR)-mediated decrease in GAD expression was found following glutamate exposure. Here we examined which NMDAR subtype(s) mediated the glutamate-induced change in GAD protein levels. Western blotting techniques on cortical neuron cultures showed that glutamate's effect on GAD proteins was not altered by NR2B-containing diheteromeric (NR1/NR2B) receptor blockade. By contrast, blockade of triheteromeric (NR1/NR2A/NR2B) receptors fully protected against a decrease in GAD protein levels following glutamate exposure. When receptor location on the postsynaptic membrane was examined, extrasynaptic NMDAR stimulation was observed to be sufficient to decrease GAD protein levels similar to that observed after glutamate bath application. Blocking diheteromeric receptors prevented glutamate's effect on GAD proteins after extrasynaptic NMDAR stimulation. Finally, NR2B subunit examination with site-specific antibodies demonstrated a glutamate-induced, calpain-mediated alteration in NR2B expression. These results suggest that glutamate-induced excitotoxic NMDAR stimulation in cultured GABAergic cortical neurons depends upon subunit composition and receptor location (synaptic vs. extrasynaptic) on the neuronal membrane. Biochemical alterations in surviving cortical GABAergic neurons in various disease states may contribute to the altered

  1. Ionotropic Glutamate Receptors IR64a and IR8a Form a Functional Odorant Receptor Complex In Vivo in Drosophila

    PubMed Central

    Blais, Steven; Park, Jin-Yong; Min, Soohong; Neubert, Thomas A.

    2013-01-01

    Drosophila olfactory sensory neurons express either odorant receptors or ionotropic glutamate receptors (IRs). The sensory neurons that express IR64a, a member of the IR family, send axonal projections to either the DC4 or DP1m glomeruli in the antennal lobe. DC4 neurons respond specifically to acids/protons, whereas DP1m neurons respond to a broad spectrum of odorants. The molecular composition of IR64a-containing receptor complexes in either DC4 or DP1m neurons is not known, however. Here, we immunoprecipitated the IR64a protein from lysates of fly antennal tissue and identified IR8a as a receptor subunit physically associated with IR64a by mass spectrometry. IR8a mutants and flies in which IR8a was knocked down by RNAi in IR64a+ neurons exhibited defects in acid-evoked physiological and behavioral responses. Furthermore, we found that the loss of IR8a caused a significant reduction in IR64a protein levels. When expressed in Xenopus oocytes, IR64a and IR8a formed a functional ion channel that allowed ligand-evoked cation currents. These findings provide direct evidence that IR8a is a subunit that forms a functional olfactory receptor with IR64a in vivo to mediate odor detection. PMID:23804096

  2. Ionotropic glutamate receptors IR64a and IR8a form a functional odorant receptor complex in vivo in Drosophila.

    PubMed

    Ai, Minrong; Blais, Steven; Park, Jin-Yong; Min, Soohong; Neubert, Thomas A; Suh, Greg S B

    2013-06-26

    Drosophila olfactory sensory neurons express either odorant receptors or ionotropic glutamate receptors (IRs). The sensory neurons that express IR64a, a member of the IR family, send axonal projections to either the DC4 or DP1m glomeruli in the antennal lobe. DC4 neurons respond specifically to acids/protons, whereas DP1m neurons respond to a broad spectrum of odorants. The molecular composition of IR64a-containing receptor complexes in either DC4 or DP1m neurons is not known, however. Here, we immunoprecipitated the IR64a protein from lysates of fly antennal tissue and identified IR8a as a receptor subunit physically associated with IR64a by mass spectrometry. IR8a mutants and flies in which IR8a was knocked down by RNAi in IR64a+ neurons exhibited defects in acid-evoked physiological and behavioral responses. Furthermore, we found that the loss of IR8a caused a significant reduction in IR64a protein levels. When expressed in Xenopus oocytes, IR64a and IR8a formed a functional ion channel that allowed ligand-evoked cation currents. These findings provide direct evidence that IR8a is a subunit that forms a functional olfactory receptor with IR64a in vivo to mediate odor detection.

  3. Selective induction of metabotropic glutamate receptor 1- and metabotropic glutamate receptor 5-dependent chemical long-term potentiation at oriens/alveus interneuron synapses of mouse hippocampus.

    PubMed

    Le Vasseur, M; Ran, I; Lacaille, J-C

    2008-01-02

    Synaptic plasticity in inhibitory interneurons is essential to maintain a proper equilibrium between excitation and inhibition in hippocampal network. Recent studies showed that theta-burst-induced long-term potentiation (LTP) at excitatory synapses of oriens/alveus (O/A) interneurons in CA1 hippocampal region required the activation of metabotropic glutamate receptor (mGluR) 1. However these interneurons also express mGluR5 and the contribution of this receptor subtype in interneuron synaptic plasticity remains unexplored. We combined pharmacological and transgenic approaches to examine the relative contribution of mGluR1/5 in LTP at excitatory synapses on O/A interneurons. Bath-application of the selective mGluR1/5 agonist (s)-3,5-dihydroxyphenylglycine (DHPG) induced LTP of compound excitatory postsynaptic potentials. DHPG-induced LTP was not prevented by application of either mGluR1 or mGluR5 antagonists, was still present in mGluR1 knockout mice, but was blocked by co-application of both antagonists. These results indicate that LTP can be induced at O/A interneuron synapses by either mGluR1 or mGluR5 activation. As previously reported for mGluR1-dependent LTP, the mGluR5-dependent LTP was independent of N-methyl-d-aspartate receptors. Pairing DHPG application with postsynaptic depolarization induced mGluR1- and mGluR5-dependent LTP of minimally-evoked excitatory postsynaptic currents, which were composed of calcium-permeable AMPA receptor and presynaptically modulated by group II mGluRs, hence confirming that both forms of LTP occurred directly at interneuron excitatory synapses. These findings uncover a new mGluR5-dependent form of LTP at O/A interneuron synapses and indicate that activation of mGluR1 or mGluR5 is sufficient to induce LTP at these synapses. Thus, a rich repertoire of adaptive changes may take place at these interneuron synapses to regulate hippocampal feedback inhibition.

  4. Glutamate receptors modulate sodium-dependent and calcium-independent vitamin C bidirectional transport in cultured avian retinal cells.

    PubMed

    Portugal, Camila Cabral; Miya, Vivian Sayuri; Calaza, Karin da Costa; Santos, Rochelle Alberto Martins; Paes-de-Carvalho, Roberto

    2009-01-01

    Vitamin C is transported in the brain by sodium vitamin C co-transporter 2 (SVCT-2) for ascorbate and glucose transporters for dehydroascorbate. Here we have studied the expression of SVCT-2 and the uptake and release of [(14)C] ascorbate in chick retinal cells. SVCT-2 immunoreactivity was detected in rat and chick retina, specially in amacrine cells and in cells in the ganglion cell layer. Accordingly, SVCT-2 was expressed in cultured retinal neurons, but not in glial cells. [(14)C] ascorbate uptake was saturable and inhibited by sulfinpyrazone or sodium-free medium, but not by treatments that inhibit dehydroascorbate transport. Glutamate-stimulated vitamin C release was not inhibited by the glutamate transport inhibitor l-beta-threo-benzylaspartate, indicating that vitamin C release was not mediated by glutamate uptake. Also, ascorbate had no effect on [(3)H] D-aspartate release, ruling out a glutamate/ascorbate exchange mechanism. 2-Carboxy-3-carboxymethyl-4-isopropenylpyrrolidine (Kainate) or NMDA stimulated the release, effects blocked by their respective antagonists 6,7-initroquinoxaline-2,3-dione (DNQX) or (5R,2S)-(1)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate (MK-801). However, DNQX, but not MK-801 or 2-amino-5-phosphonopentanoic acid (APV), blocked the stimulation by glutamate. Interestingly, DNQX prevented the stimulation by NMDA, suggesting that the effect of NMDA was mediated by glutamate release and stimulation of non-NMDA receptors. The effect of glutamate was neither dependent on external calcium nor inhibited by 1,2-bis (2-aminophenoxy) ethane-N',N',N',N',-tetraacetic acid tetrakis (acetoxy-methyl ester) (BAPTA-AM), an internal calcium chelator, but was inhibited by sulfinpyrazone or by the absence of sodium. In conclusion, retinal cells take up and release vitamin C, probably through SVCT-2, and the release can be stimulated by NMDA or non-NMDA glutamate receptors.

  5. Enhancement of Glutamate Release by l-Fucose Changes Effects of Glutamate Receptor Antagonists on Long-Term Potentiation in the Rat Hippocampus

    PubMed Central

    Matthies, Henry; Schroeder, Helmut; Smalla, Karl-Heinz; Krug, Manfred

    2000-01-01

    In previous studies l-fucose has been shown to facilitate long-term memory formation and to enhance and prolong long-term potentiation (LTP). To search for possible presynaptic or postsynaptic mechanisms that are affected by l-fucose, we examined the effect of l-fucose on (1) inhibition of LTP induction via glutamate receptors by antagonists, (2) paired-pulse facilitation, and (3) presynaptic transmitter release. Coapplication of 0.2 mm l-fucose with the competitive N-methyl-d-aspartate (NMDA) receptor antagonist, d-2-amino-5-phosphonovalerate (AP5), or coapplication of 0.2 mml-fucose in the presence of an inhibitor for class I/II metabotropic glutamate receptors, (S)-α-methyl-4-carboxyphenylglycine (MCPG), reversed LTP blockade in the CA1-region of hippocampal slices. In contrast, l-fucose had no effect on the LTP blockade by the noncompetitive NMDA ion-channel blocker (5R,10S)-(+)-5-Methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5, 10-imine hydrogen maleate (MK-801). Paired-pulse facilitation, which is a primarily presynaptic phenomenon of short-term plasticity, was decreased in the presence of 0.2 mm l-fucose. Furthermore, l-fucose enhanced the K+-stimulated release of [3H]-d-aspartate from preloaded hippocampal slices in a concentration-dependent manner. These observations demonstrate an influence of l-fucose on transmitter release that in turn can increase transmitter availability at postsynaptic glutamate receptors. This effect of l-fucose may contribute to the LTP facilitation seen in vitro and in vivo as well as to improvement in memory formation. PMID:10940323

  6. Oligomers of Amyloid β Prevent Physiological Activation of the Cellular Prion Protein-Metabotropic Glutamate Receptor 5 Complex by Glutamate in Alzheimer Disease.

    PubMed

    Haas, Laura T; Strittmatter, Stephen M

    2016-08-12

    The dysfunction and loss of synapses in Alzheimer disease are central to dementia symptoms. We have recently demonstrated that pathological Amyloid β oligomer (Aβo) regulates the association between intracellular protein mediators and the synaptic receptor complex composed of cellular prion protein (PrP(C)) and metabotropic glutamate receptor 5 (mGluR5). Here we sought to determine whether Aβo alters the physiological signaling of the PrP(C)-mGluR5 complex upon glutamate activation. We provide evidence that acute exposure to Aβo as well as chronic expression of familial Alzheimer disease mutant transgenes in model mice prevents protein-protein interaction changes of the complex induced by the glutamate analog 3,5-dihydroxyphenylglycine. We further show that 3,5-dihydroxyphenylglycine triggers the phosphorylation and activation of protein-tyrosine kinase 2-β (PTK2B, also referred to as Pyk2) and of calcium/calmodulin-dependent protein kinase II in wild-type brain slices but not in Alzheimer disease transgenic brain slices or wild-type slices incubated with Aβo. This study further distinguishes two separate Aβo-dependent signaling cascades, one dependent on extracellular Ca(2+) and Fyn kinase activation and the other dependent on the release of Ca(2+) from intracellular stores. Thus, Aβo triggers multiple distinct PrP(C)-mGluR5-dependent events implicated in neurodegeneration and dementia. We propose that targeting the PrP(C)-mGluR5 complex will reverse aberrant Aβo-triggered states of the complex to allow physiological fluctuations of glutamate signaling.

  7. Ionotropic Glutamate Receptors Mediate Inducible Defense in the Water Flea Daphnia pulex

    PubMed Central

    Miyakawa, Hitoshi; Sato, Masanao; Colbourne, John K.; Iguchi, Taisen

    2015-01-01

    Phenotypic plasticity is the ability held in many organisms to produce different phenotypes with a given genome in response to environmental stimuli, such as temperature, nutrition and various biological interactions. It seems likely that environmental signals induce a variety of mechanistic responses that influence ontogenetic processes. Inducible defenses, in which prey animals alter their morphology, behavior and/or other traits to help protect against direct or latent predation threats, are among the most striking examples of phenotypic plasticity. The freshwater microcrustacean Daphnia pulex forms tooth-like defensive structures, “neckteeth,” in response to chemical cues or signals, referred to as “kairomones,” in this case released from phantom midge larvae, a predator of D. pulex. To identify factors involved in the reception and/or transmission of a kairomone, we used microarray analysis to identify genes up-regulated following a short period of exposure to the midge kairomone. In addition to identifying differentially expressed genes of unknown function, we also found significant up-regulation of genes encoding ionotropic glutamate receptors, which are known to be involved in neurotransmission in many animal species. Specific antagonists of these receptors strongly inhibit the formation of neckteeth in D. pulex, although agonists did not induce neckteeth by themselves, indicating that ionotropic glutamate receptors are necessary but not sufficient for early steps of neckteeth formation in D. pulex. Moreover, using co-exposure of D. pulex to antagonists and juvenile hormone (JH), which physiologically mediates neckteeth formation, we found evidence suggesting that the inhibitory effect of antagonists is not due to direct inhibition of JH synthesis/secretion. Our findings not only provide a candidate molecule required for the inducible defense response in D. pulex, but also will contribute to the understanding of complex mechanisms underlying the

  8. Differential distribution of group I metabotropic glutamate receptors in developing human cortex.

    PubMed

    Boer, Karin; Encha-Razavi, Ferechte; Sinico, Martine; Aronica, Eleonora

    2010-04-09

    Neuronal and glial cells in human cerebral cortex are enriched in group I metabotropic glutamate receptors (mGluRs). Developmental regulation of mGluRs has been shown in rodent brain and recent studies suggest an involvement of mGluR-mediated glutamate signaling in the proliferation and survival of neural progenitor cells. In the present study, we have investigated the expression and cell-specific distribution of group I mGluRs (mGluR1alpha and mGluR5) during prenatal human cortical development. mGluR5 was expressed in developing human cortex from the earliest stages tested (9 gestational weeks, GW), with strong expression in the ventricular/subventricular zones. mGluR1alpha immunoreactivity (IR) was observed in the cortical plate at 13GW and persisted throughout the prenatal development. Both receptors were expressed in pyramidal neurons in the first postnatal year. Group I mGluRs were also expressed by reelin-positive Cajal-Retzius cells present in the marginal zone/layer I of the developing cortex. mGluR5 IR in these cells was observed in the earliest developmental stages and persisted during the early postnatal period. In contrast, mGluR1alpha IR was detected in Cajal-Retzius cells during the late phase of prenatal development. These findings show a differential expression pattern of group I mGluR subtypes, suggesting a role for both receptors in the early stages of corticogenesis with, however, a different contribution to human cortical developmental events.

  9. Structure-activity relationship study of spider polyamine toxins as inhibitors of ionotropic glutamate receptors.

    PubMed

    Xiong, Xiao-Feng; Poulsen, Mette H; Hussein, Rama A; Nørager, Niels G; Strømgaard, Kristian

    2014-12-01

    The spider polyamine toxins Joro spider toxin-3 (JSTX-3) and Nephila polyamine toxins-1 and -8 (NPTX-1 and NPTX-8) are isolated from the venom of the orb-weaver spider Nephila clavata (Joro spider). They share a high degree of structural resemblance, their aromatic head groups being the only difference, and were recently found to be very potent open-channel blockers of ionotropic glutamate (iGlu) receptors. In this study we designed and synthesized a collection of 24 analogues of these toxins using a recently developed solid-phase synthetic methodology. Systematic variation in two regions of the toxins and subsequent evaluation of biological activity at AMPA and NMDA subtypes of iGlu receptors provided succinct information on structure-activity relationships. In particular, one set of analogues were found to display exquisite selectivity and potency for AMPA receptors relative to the natural products. Thus, this systematic SAR study has provided new pharmacological tools for studies of iGlu receptors.

  10. Cooperative Signaling between Homodimers of Metabotropic Glutamate Receptors 1 and 5

    PubMed Central

    Sevastyanova, Tatyana N.

    2014-01-01

    Metabotropic glutamate receptors (mGluRs) function as dimers. Recent work suggests that mGluR1 and mGluR5 may physically interact, but the nature and functional consequences of this relationship have not been addressed. In this study, the functional and pharmacological consequences of this interaction were investigated. Using heterologous expression of mGluR cDNA in rat sympathetic neurons from the superior cervical ganglion and inhibition of the native calcium currents as an assay for receptor activation, a functional interdependence between mGluR1 and mGluR5 was demonstrated. In neurons coexpressing these receptors, combining a selective mGluR1 competitive antagonist with either an mGluR1- or mGluR5-selective negative allosteric modulator (NAM) BAY36-7620 [(3aS,6aS)-hexahydro-5-methylene-6a-(2-naphthalenylmethyl)-1H-cyclopenta[c]furan-1-one] or MPEP [2-methyl-6-(phenylethynyl)pyridine hydrochloride], respectively, strongly occluded signaling by both receptors to an approximately equal degree. By contrast, in cells coexpressing mGluR1 and mGluR2, combining the same mGluR1 competitive inhibitor with an mGluR1 or mGluR2 NAM yielded partial and full inhibition of the response, respectively, as expected for independently acting receptors. In neurons expressing mGluR1 and mGluR5, the selective NAMs each strongly inhibited the response to glutamate, suggesting that these receptors do not interact as heterodimers, which would not be inhibited by selective NAMs. Finally, evidence for a similar mGluR1/mGluR5 functional dependence is shown in medium spiny striatal neurons. Together, these data demonstrate cooperative signaling between mGluR1 and mGluR5 in a manner inconsistent with heterodimerization, and thus suggest an interaction between homodimers. PMID:25113912

  11. GABAA and glutamate receptor involvement in dendrodendritic synaptic interactions from salamander olfactory bulb.

    PubMed

    Wellis, D P; Kauer, J S

    1993-09-01

    1. Whole-cell patch clamp and optical recording techniques were applied to the same in vitro salamander olfactory bulb preparations to study the postsynaptic responses of single mitral/tufted cells in the context of the surrounding neural activity in which they are embedded. Mitral/tufted cells were identified by intracellular filling with biocytin. 2. Single mitral/tufted cells were under a tonic GABAA receptor-mediated inhibitory influence as revealed by the recording of bicuculline methiodide (BMI)/picrotoxin-sensitive inhibitory postsynaptic currents (IPSCs) in symmetrical chloride conditions at a holding potential of -70 mV. Depolarizing voltage steps (100 ms) applied to single cells or electrical stimulation of the olfactory nerve or medial olfactory tract evoked a prolonged increase in the frequency of GABAergic IPSCs. 3. The frequency of spontaneous and driven IPSCs was reduced with application of the glutamate receptor antagonists 6-cyano-2,3-dihydroxy-7-nitro-quionoxaline (CNQX) or 2-amino-5-phosphonopentanoic acid (AP5) whereas olfactory nerve- or medial olfactory tract-driven IPSC frequency was enhanced with removal of bathing Mg2+, indicating that GABAergic interneurones were driven by mitral/tufted cells at both non-NMDA and NMDA receptors. 4. Olfactory nerve or medial olfactory tract stimulation evoked widely distributed changes in fluorescence in preparations stained with the voltage-sensitive dye RH414. The optical response predominantly consisted of a decrease in fluorescence, indicative of depolarization. The presence of the dye did not obviously affect mitral/tufted cell postsynaptic responses. 5. BMI enhanced the amplitude and duration of optical signals related to depolarization within the bulb and in regions central to the bulb. In the presence of BMI, depolarizing activity appeared to spread hundreds of micrometres into regions of the bulb not activated in control conditions showing explicitly that GABAA receptors in the bulb participate in

  12. Endogenous dopamine increases extracellular concentrations of glutamate and GABA in striatum of the freely moving rat: involvement of D1 and D2 dopamine receptors.

    PubMed

    Expósito, I; Del Arco, A; Segovia, G; Mora, F

    1999-07-01

    Interactions between endogenous dopamine, glutamate, GABA, and taurine were investigated in striatum of the freely moving rat by using microdialysis. Intrastriatal infusions of the selective dopamine uptake inhibitor nomifensine (NMF) were used to increase the endogenous extracellular dopamine. NMF produced a dose-related increase in extracellular dopamine and also increased extracellular concentrations of glutamate, GABA, and taurine. Extracellular increases of dopamine were significantly correlated with extracellular increases of glutamate and GABA, but not taurine. To investigate whether the increased extracellular dopamine produced by NMF was responsible for the concomitant increase of glutamate and GABA, D1, and D2 receptor antagonists were used. Dopamine receptor antagonists D1 (SCH23390) and D2 (sulpiride) significantly attenuated the increases of glutamate and GABA produced by NMF. These data suggest that endogenous dopamine, through both D1 and D2 dopamine receptors, plays a role in releasing glutamate and GABA in striatum of the freely moving rat.

  13. Central phencyclidine (PCP) receptor binding is glutamate dependent: evidence for a PCP/excitatory amino acid receptor (EAAR) complex

    SciTech Connect

    Loo, P.; Braunwalder, A.; Lehmann, J.; Williams, M.

    1986-03-01

    PCP and other dissociative anesthetica block the increase in neuronal firing rate evoked by the EAAR agonist, N-methyl-Daspartate. NMDA and other EAAs such as glutamate (glu) have not been previously shown to affect PCP ligand binding. In the present study, using once washed rat forebrain membranes, 10 ..mu..M-glu was found to increase the binding of (/sup 3/H)TCP, a PCP analog, to defined PCP recognition sites by 20%. Removal of glu and aspartate (asp) by extensive washing decreased TCP binding by 75-90%. In these membranes, 10 ..mu..M L-glu increased TCP binding 3-fold. This effect was stereospecific and evoked by other EAAs with the order of activity, L-glu > D-asp > L- asp > NMDA > D-glu > quisqualate. Kainate, GABA, NE, DA, 5-HT, 2-chloroadenosine, oxotremorine and histamine had no effect on TCP binding at concentrations up to 100 ..mu..M. The effects of L-glu were attenuated by the NMDA-type receptor antagonist, 2-amino-7--phosphonoheptanoate (AP7; 10 ..mu..M-1 mM). These findings indicate that EAAS facilitate TCP binding, possibly through NMDA-type receptors. The observed interaction between the PCP receptor and EAARs may reflect the existence of a macromolecular receptor complex similar to that demonstrated for the benzodiazepines and GABA.

  14. Ciproxifan, a histamine H3 receptor antagonist and inverse agonist, presynaptically inhibits glutamate release in rat hippocampus.

    PubMed

    Lu, Cheng-Wei; Lin, Tzu-Yu; Chang, Chia-Ying; Huang, Shu-Kuei; Wang, Su-Jane

    2017-03-15

    Ciproxifan is an H3 receptor antagonist and inverse agonist with antipsychotic effects in several preclinical models; its effect on glutamate release has been investigated in the rat hippocampus. In a synaptosomal preparation, ciproxifan reduced 4-aminopyridine (4-AP)-evoked Ca(2+)-dependent glutamate release and cytosolic Ca(2+) concentration elevation but did not affect the membrane potential. The inhibitory effect of ciproxifan on 4-AP-evoked glutamate release was prevented by the Gi/Go-protein inhibitor pertussis toxin and Cav2.2 (N-type) and Cav2.1 (P/Q-type) channel blocker ω-conotoxin MVIIC, but was not affected by the intracellular Ca(2+)-release inhibitors dantrolene and CGP37157. Furthermore, the phospholipase A2 (PLA2) inhibitor OBAA, prostaglandin E2 (PGE2), PGE2 subtype 2 (EP2) receptor antagonist PF04418948, and extracellular signal-regulated kinase (ERK) inhibitor FR180204 eliminated the inhibitory effect of ciproxifan on glutamate release. Ciproxifan reduced the 4-AP-evoked phosphorylation of ERK and synapsin I, a presynaptic target of ERK. The ciproxifan-mediated inhibition of glutamate release was prevented in synaptosomes from synapsin I-deficient mice. Moreover, ciproxifan reduced the frequency of miniature excitatory postsynaptic currents without affecting their amplitude in hippocampal slices. Our data suggest that ciproxifan, acting through the blockade of Gi/Go protein-coupled H3 receptors present on hippocampal nerve terminals, reduces voltage-dependent Ca(2+) entry by diminishing PLA2/PGE2/EP2 receptor pathway, which subsequently suppresses the ERK/synapsin I cascade to decrease the evoked glutamate release.

  15. Endogenous activation of kainate receptors regulates glutamate release and network activity in the developing hippocampus.

    PubMed

    Lauri, Sari E; Segerstråle, Mikael; Vesikansa, Aino; Maingret, Francois; Mulle, Christophe; Collingridge, Graham L; Isaac, John T R; Taira, Tomi

    2005-05-04

    Kainate receptors (KARs) are highly expressed throughout the neonatal brain, but their function during development is unclear. Here, we show that the maturation of the hippocampus is associated with a switch in the functional role of presynaptic KARs. In a developmental period restricted to the first postnatal week, endogenous L-glutamate tonically activates KARs at CA3 glutamatergic synapses to regulate release in an action potential-independent manner. At synapses onto pyramidal cells, KARs inhibit glutamate release via a G-protein and PKC-dependent mechanism. In contrast, at glutamatergic terminals onto CA3 interneurons, presynaptic KARs can facilitate release in a G-protein-independent mechanism. In both cell types, however, KAR activation strongly upregulates inhibitory transmission. We show that, through the interplay of these novel diverse mechanisms, KARs strongly regulate the characteristic synchronous network activity observed in the neonatal hippocampus. By virtue of this, KARs are likely to play a central role in the development of hippocampal synaptic circuits.

  16. Depletion of serotonin in the basolateral amygdala elevates glutamate receptors and facilitates fear-potentiated startle

    PubMed Central

    Tran, L; Lasher, B K; Young, K A; Keele, N B

    2013-01-01

    Our previous experiments demonstrated that systemic depletion of serotonin (5-hydroxytryptamine, 5-HT), similar to levels reported in patients with emotional disorders, enhanced glutamateric activity in the lateral nucleus of the amygdala (LA) and potentiated fear behaviors. However, the effects of isolated depletion of 5-HT in the LA, and the molecular mechanisms underlying enhanced glutamatergic activity are unknown. In the present study, we tested the hypothesis that depletion of 5-HT in the LA induces increased fear behavior, and concomitantly enhances glutamate receptor (GluR) expression. Bilateral infusions of 5,7-dihydroxytryptamine (4 μg per side) into the LA produced a regional reduction of serotonergic fibers, resulting in decreased 5-HT concentrations. The induction of low 5-HT in the LA elevated fear-potentiated startle, with a parallel increase in GluR1 mRNA and GluR1 protein expression. These findings suggest that low 5-HT concentrations in the LA may facilitate fear behavior through enhanced GluR-mediated mechanisms. Moreover, our data support a relationship between 5-HT and glutamate in psychopathologies. PMID:24002084

  17. Potentiation of acid-sensing ion channel activity by peripheral group I metabotropic glutamate receptor signaling.

    PubMed

    Gan, Xiong; Wu, Jing; Ren, Cuixia; Qiu, Chun-Yu; Li, Yan-Kun; Hu, Wang-Ping

    2016-05-01

    Glutamate activates peripheral group I metabotropic glutamate receptors (mGluRs) and contributes to inflammatory pain. However, it is still not clear the mechanisms are involved in group I mGluR-mediated peripheral sensitization. Herein, we report that group I mGluRs signaling sensitizes acid-sensing ion channels (ASICs) in dorsal root ganglion (DRG) neurons and contributes to acidosis-evoked pain. DHPG, a selective group I mGluR agonist, can potentiate the functional activity of ASICs, which mediated the proton-induced events. DHPG concentration-dependently increased proton-gated currents in DRG neurons. It shifted the proton concentration-response curve upwards, with a 47.3±7.0% increase of the maximal current response to proton. Group I mGluRs, especially mGluR5, mediated the potentiation of DHPG via an intracellular cascade. DHPG potentiation of proton-gated currents disappeared after inhibition of intracellular Gq/11 proteins, PLCβ, PKC or PICK1 signaling. Moreover, DHPG enhanced proton-evoked membrane excitability of rat DRG neurons and increased the amplitude of the depolarization and the number of spikes induced by acid stimuli. Finally, peripherally administration of DHPG dose-dependently exacerbated nociceptive responses to intraplantar injection of acetic acid in rats. Potentiation of ASIC activity by group I mGluR signaling in rat DRG neurons revealed a novel peripheral mechanism underlying group I mGluRs involvement in hyperalgesia.

  18. AMPA glutamate receptors are required for sensory-organ formation and morphogenesis in the basal chordate.

    PubMed

    Hirai, Shinobu; Hotta, Kohji; Kubo, Yoshihiro; Nishino, Atsuo; Okabe, Shigeo; Okamura, Yasushi; Okado, Haruo

    2017-04-11

    AMPA-type glutamate receptors (GluAs) mediate fast excitatory transmission in the vertebrate central nervous system (CNS), and their function has been extensively studied in the mature mammalian brain. However, GluA expression begins very early in developing embryos, suggesting that they may also have unidentified developmental roles. Here, we identify developmental roles for GluAs in the ascidian Ciona intestinalis Mammals express Ca(2+)-permeable GluAs (Ca-P GluAs) and Ca(2+)-impermeable GluAs (Ca-I GluAs) by combining subunits derived from four genes. In contrast, ascidians have a single gluA gene. Taking advantage of the simple genomic GluA organization in ascidians, we knocked down (KD) GluAs in Ciona and observed severe impairments in formation of the ocellus, a photoreceptive organ used during the swimming stage, and in resorption of the tail and body axis rotation during metamorphosis to the adult stage. These defects could be rescued by injection of KD-resistant GluAs. GluA KD phenotypes could also be reproduced by expressing a GluA mutant that dominantly inhibits glutamate-evoked currents. These results suggest that, in addition to their role in synaptic communication in mature animals, GluAs also have critical developmental functions.

  19. Properties of glutamate receptors of Alzheimer's disease brain transplanted to frog oocytes

    PubMed Central

    Bernareggi, Annalisa; Dueñas, Zulma; Reyes-Ruiz, Jorge Mauricio; Ruzzier, Fabio; Miledi, Ricardo

    2007-01-01

    It is known that Alzheimer's disease (AD) is a synaptic disease that involves various neurotransmitter systems, particularly those where synaptic transmission is mediated by acetylcholine or glutamate (Glu). Nevertheless, very little is known about the properties of neurotransmitter receptors of the AD human brain. We have shown previously that cell membranes, carrying neurotransmitter receptors from the human postmortem brain, can be transplanted to frog oocytes, and their receptors will still be functional. Taking advantage of this fact, we have now studied the properties of Glu receptors (GluRs) from the cerebral cortices of AD and non-AD brains and found that oocytes injected with AD membranes acquired GluRs that have essentially the same functional properties as those of oocytes injected with membranes from non-AD brains. However, the amplitudes of the currents elicited by Glu were always smaller in the oocytes injected with membranes from AD brains. Western blot analyses of the same membrane preparations used for the electrophysiological studies showed that AD membranes contained significantly fewer GluR2/3 subunit proteins. Furthermore, the corresponding mRNAs were also diminished in the AD brain. Therefore, the smaller amplitude of membrane currents elicited by Glu in oocytes injected with membranes from an AD brain is a consequence of a reduced number of GluRs in cell membranes transplanted from the AD brain. Thus, using the comparatively simple method of microtransplantation of receptors, it is now possible to determine the properties of neurotransmitter receptors of normal and diseased human brains. That knowledge may help to decipher the etiology of the diseases and also to develop new treatments. PMID:17301224

  20. GAS, a new glutamate-rich protein, interacts differentially with SRCs and is involved in oestrogen receptor function

    PubMed Central

    Liang, Jing; Zhang, Hua; Zhang, Yu; Zhang, Ying; Shang, Yongfeng

    2009-01-01

    Steroid receptor coactivators (SRCs) exert profound effects on animal development and physiology. Genetic ablation experiments indicate that various SRC proteins might have differential physiological roles; however, clear evidence of functional specificity has not yet been shown at the molecular level. Here we report the identification of a new SRC1 interacting protein, glutamate-rich coactivator interacting with SRC1 (GAS), which contains a central glutamate-rich region and has transactivation activity. Interestingly, GAS interacts only with SRC1, and not with glucocorticoid receptor interacting protein 1 (GRIP1) or amplified in breast cancer 1 (AIB1), the other two members of the SRC family. It interacts with oestrogen receptor-α (ERα) and participates in both oestrogen receptor-regulated gene transcription and oestrogen-stimulated G1/S cell-cycle transition. Our data thus indicate that GAS is a new transcription cofactor and that different SRCs are associated with distinct secondary cofactors. PMID:19039327

  1. Activation of Group II Metabotropic Glutamate Receptors Induces Depotentiation in Amygdala Slices and Reduces Fear-Potentiated Startle in Rats

    ERIC Educational Resources Information Center

    Lin, Chia-Ho; Lee, Chia-Ching; Huang, Ya-Chun; Wang, Su-Jane; Gean, Po-Wu

    2005-01-01

    There is a close correlation between long-term potentiation (LTP) in the synapses of lateral amygdala (LA) and fear conditioning in animals. We predict that reversal of LTP (depotentiation) in this area of the brain may ameliorate conditioned fear. Activation of group II metabotropic glutamate receptors (mGluR II) with DCG-IV induces…

  2. Identification of an ionotropic glutamate receptor AMPA1/GRIA1 polymorphism in crossbred beef cows differing in fertility

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A proposed functional polymorphism in the ionotropic glutamate receptor AMPA1 (GRIA1) has been reported to influence antral follicle numbers and fertility in cows. Repeat Breeder cows that fail to produce a calf in multiple seasons have been reported to have reduced numbers of small (1-3 mm) antral ...

  3. Excessive activation of ionotropic glutamate receptors induces apoptotic hair-cell death independent of afferent and efferent innervation

    PubMed Central

    Sheets, Lavinia

    2017-01-01

    Accumulation of excess glutamate plays a central role in eliciting the pathological events that follow intensely loud noise exposures and ischemia-reperfusion injury. Glutamate excitotoxicity has been characterized in cochlear nerve terminals, but much less is known about whether excess glutamate signaling also contributes to pathological changes in sensory hair cells. I therefore examined whether glutamate excitotoxicity damages hair cells in zebrafish larvae exposed to drugs that mimic excitotoxic trauma. Exposure to ionotropic glutamate receptor (iGluR) agonists, kainic acid (KA) or N-methyl-D-aspartate (NMDA), contributed to significant, progressive hair cell loss in zebrafish lateral-line organs. To examine whether hair-cell loss was a secondary effect of excitotoxic damage to innervating neurons, I exposed neurog1a morphants—fish whose hair-cell organs are devoid of afferent and efferent innervation—to KA or NMDA. Significant, dose-dependent hair-cell loss occurred in neurog1a morphants exposed to either agonist, and the loss was comparable to wild-type siblings. A survey of iGluR gene expression revealed AMPA-, Kainate-, and NMDA-type subunits are expressed in zebrafish hair cells. Finally, hair cells exposed to KA or NMDA appear to undergo apoptotic cell death. Cumulatively, these data reveal that excess glutamate signaling through iGluRs induces hair-cell death independent of damage to postsynaptic terminals. PMID:28112265

  4. Metabotropic glutamate receptor dependent long-term depression in the cortex

    PubMed Central

    Kang, Sukjae Joshua

    2016-01-01

    Metabotropic glutamate receptor (mGluR)-dependent long-term depression (LTD), a type of synaptic plasticity, is characterized by a reduction in the synaptic response, mainly at the excitatory synapses of the neurons. The hippocampus and the cerebellum have been the most extensively studied regions in mGluR-dependent LTD, and Group 1 mGluR has been reported to be mainly involved in this synaptic LTD at excitatory synapses. However, mGluR-dependent LTD in other brain regions may be involved in the specific behaviors or diseases. In this paper, we focus on five cortical regions and review the literature that implicates their contribution to the pathogenesis of several behaviors and specific conditions associated with mGluR-dependent LTD. PMID:27847432

  5. Maternal transmission disequilibrium of the glutamate receptor GRIK2 in schizophrenia.

    PubMed

    Bah, J; Quach, H; Ebstein, R P; Segman, R H; Melke, J; Jamain, S; Rietschel, M; Modai, I; Kanas, K; Karni, O; Lerer, B; Gourion, D; Krebs, M O; Etain, B; Schürhoff, F; Szöke, A; Leboyer, M; Bourgeron, T

    2004-08-26

    Schizophrenia is characterized by thought disorders, hallucinations and delusions. Genetic studies have shown a high linkage at chromosome 6q16-21. Among the genes located in this region is the glutamate receptor ionotropic kainate 2 gene (GRIK2 or GLUR6), a functional candidate for susceptibility to schizophrenia. In this study, transmission of GRIK2 was evaluated in 356 schizophrenic patients from three different clinical centers. Whereas paternal transmission shows equilibrium, we observed maternal transmission disequilibrium of GRIK2 in the largest population (p=0.03), which was still significant when all populations were added (p=0.05). These results are similar to the maternal GRIK2 transmission disequilibrium previously reported for autism, and support the presence of a susceptibility gene for schizophrenia at 6q16.

  6. Induction of an Olfactory Memory by the Activation of a Metabotropic Glutamate Receptor

    NASA Astrophysics Data System (ADS)

    Kaba, Hideto; Hayashi, Yasunori; Higuchi, Takashi; Nakanishi, Shigetada

    1994-07-01

    Female mice form an olfactory memory of male pheromones at mating; exposure to the pheromones of a strange male after that mating will block pregnancy. The formation of this memory is mediated by the accessory olfactory system, in which an increase in norepinephrine after mating reduces inhibitory transmission of γ-aminobutyric acid from the granule cells to the mitral cells. This study shows that the activation of mGluR2, a metabotropic glutamate receptor that suppresses the γ-aminobutyric acid inhibition of the mitral cells, permits the formation of a specific olfactory memory without the occurrence of mating by infusion of mGluR2 agonists into the female's accessory olfactory bulb. This memory faithfully reflects the memory formed at mating.

  7. Kismet Positively Regulates Glutamate Receptor Localization and Synaptic Transmission at the Drosophila Neuromuscular Junction

    PubMed Central

    Ghosh, Rupa; Vegesna, Srikar; Safi, Ramia; Bao, Hong; Zhang, Bing; Marenda, Daniel R.; Liebl, Faith L. W.

    2014-01-01

    The Drosophila neuromuscular junction (NMJ) is a glutamatergic synapse that is structurally and functionally similar to mammalian glutamatergic synapses. These synapses can, as a result of changes in activity, alter the strength of their connections via processes that require chromatin remodeling and changes in gene expression. The chromodomain helicase DNA binding (CHD) protein, Kismet (Kis), is expressed in both motor neuron nuclei and postsynaptic muscle nuclei of the Drosophila larvae. Here, we show that Kis is important for motor neuron synaptic morphology, the localization and clustering of postsynaptic glutamate receptors, larval motor behavior, and synaptic transmission. Our data suggest that Kis is part of the machinery that modulates the development and function of the NMJ. Kis is the homolog to human CHD7, which is mutated in CHARGE syndrome. Thus, our data suggest novel avenues of investigation for synaptic defects associated with CHARGE syndrome. PMID:25412171

  8. Metabotropic glutamate receptor agonists potentiate a slow afterdepolarization in CNS neurons

    NASA Technical Reports Server (NTRS)

    Zheng, F.; Gallagher, J. P.

    1992-01-01

    We have previously reported that, in the rat dorsolateral septal nucleus (DLSN), metabotropic glutamate receptor (met-GluR) agonists evoked a slow depolarization accompanied by an increase in membrane conductance and burst firing. We have speculated that the burst firing elicited by met-GluR agonists may be due to activation or enhancement of a non-specific cation current, which exists in some DLSN neurons. Now we report that a slow afterdepolarization (sADP) mediated by a non-specific cation current was potentiated by both 1S,3R-ACPD and quisqualate. In addition, met-GluR agonists unmask a sADP in DLSN neurons which did not show a sADP under control conditions. Our data suggest that a non-specific cation current can be potentiated by activation of the met-GluR.

  9. Enhanced pronociception by amygdaloid group I metabotropic glutamate receptors in nerve-injured animals.

    PubMed

    Ansah, Osei B; Gonçalves, Leonor; Almeida, Armando; Pertovaara, Antti

    2009-03-01

    Peripheral neuropathy has been associated with structural and functional changes of the amygdala, a key player in emotions. Here we study whether peripheral neuropathy influences pain regulation by the amygdala. For this purpose, we determined discharge rates of presumably pro- and antinociceptive pain-regulatory neurons in the rostral ventromedial medulla (RVM) following microinjection of various glutamatergic compounds into the central nucleus of the amygdala. RVM neurons were recorded in pentobarbitone-anesthetized rats with a peripheral nerve injury or sham-operation. In a separate behavioral experiment, we determined whether the influence of amygdaloid administration of a glutamatergic compound on affective pain-related behavior, as assessed by an aversive place-conditioning test, is changed by neuropathy. While glutamate or an NMDA receptor antagonist in the amygdala failed to induce marked changes in discharge rates of RVM cells, amygdaloid administration of DHPG, a group I metabotropic glutamate receptor (mGluR) agonist acting on mGluR(1) and mGluR(5), increased discharge rates of presumably pronociceptive RVM ON-cells in nerve-injured but not sham-operated animals. This pronociceptive effect of DHPG was reversed by MPEP (mGluR(5) antagonist) and CPCCOEt (mGluR(1) antagonist). CHPG, an mGluR(5) agonist, failed to influence ON-cell activity and DHPG failed to influence activity of presumably antinociceptive RVM OFF-cells. Amygdaloid administration of DHPG increased and that of CPCCOEt decreased affective pain-related behavior in nerve-injured animals. The results suggest that following nerve injury, the amygdaloid group I mGluR, particularly subtype mGluR(1), has an enhanced pronociceptive effect providing a potential mechanism for emotional enhancement of pain in peripheral neuropathy.

  10. Palmitoylation regulates glutamate receptor distributions in postsynaptic densities through control of PSD95 conformation and orientation

    PubMed Central

    Jeyifous, Okunola; Lin, Eric I.; Chen, Xiaobing; Antinone, Sarah E.; Mastro, Ryan; Drisdel, Renaldo; Reese, Thomas S.; Green, William N.

    2016-01-01

    Postsynaptic density protein 95 (PSD95) and synapse-associated protein 97 (SAP97) are homologous scaffold proteins with different N-terminal domains, possessing either a palmitoylation site (PSD95) or an L27 domain (SAP97). Here, we measured PSD95 and SAP97 conformation in vitro and in postsynaptic densities (PSDs) using FRET and EM, and examined how conformation regulated interactions with AMPA-type and NMDA-type glutamate receptors (AMPARs/NMDARs). Palmitoylation of PSD95 changed its conformation from a compact to an extended configuration. PSD95 associated with AMPARs (via transmembrane AMPAR regulatory protein subunits) or NMDARs [via glutamate ionotropic receptor NMDA-type subunit 2B (GluN2B) subunits] only in its palmitoylated and extended conformation. In contrast, in its extended conformation, SAP97 associates with NMDARs, but not with AMPARs. Within PSDs, PSD95 and SAP97 were largely in the extended conformation, but had different orientations. PSD95 oriented perpendicular to the PSD membrane, with its palmitoylated, N-terminal domain at the membrane. SAP97 oriented parallel to the PSD membrane, likely as a dimer through interactions of its N-terminal L27 domain. Changing PSD95 palmitoylation in PSDs altered PSD95 and AMPAR levels but did not affect NMDAR levels. These results indicate that in PSDs, PSD95 palmitoylation, conformation, and its interactions are dynamic when associated with AMPARs and more stable when associated with NMDARs. Altogether, our results are consistent with differential regulation of PSD95 palmitoylation in PSDs resulting from the clustering of palmitoylating and depalmitoylating enzymes into AMPAR nanodomains segregated away from NMDAR nanodomains. PMID:27956638

  11. Metabotropic Glutamate 2/3 Receptors and Epigenetic Modifications in Psychotic Disorders: A Review.

    PubMed

    Matrisciano, Francesco; Panaccione, Isabella; Grayson, Danis R; Nicoletti, Ferdinando; Guidotti, Alessandro

    2016-01-01

    Schizophrenia and Bipolar Disorder are chronic psychiatric disorders, both considered as "major psychosis"; they are thought to share some pathogenetic factors involving a dysfunctional gene x environment interaction. Alterations in the glutamatergic transmission have been suggested to be involved in the pathogenesis of psychosis. Our group developed an epigenetic model of schizophrenia originated by Prenatal Restraint Stress (PRS) paradigm in mice. PRS mice developed some behavioral alterations observed in schizophrenic patients and classic animal models of schizophrenia, i.e. deficits in social interaction, locomotor activity and prepulse inhibition. They also showed specific changes in promoter DNA methylation activity of genes related to schizophrenia such as reelin, BDNF and GAD67, and altered expression and function of mGlu2/3 receptors in the frontal cortex. Interestingly, behavioral and molecular alterations were reversed by treatment with mGlu2/3 agonists. Based on these findings, we speculate that pharmacological modulation of these receptors could have a great impact on early phase treatment of psychosis together with the possibility to modulate specific epigenetic key protein involved in the development of psychosis. In this review, we will discuss in more details the specific features of the PRS mice as a suitable epigenetic model for major psychosis. We will then focus on key proteins of chromatin remodeling machinery as potential target for new pharmacological treatment through the activation of metabotropic glutamate receptors.

  12. Actinin-4 Governs Dendritic Spine Dynamics and Promotes Their Remodeling by Metabotropic Glutamate Receptors*

    PubMed Central

    Kalinowska, Magdalena; Chávez, Andrés E.; Lutzu, Stefano; Castillo, Pablo E.; Bukauskas, Feliksas F.; Francesconi, Anna

    2015-01-01

    Dendritic spines are dynamic, actin-rich protrusions in neurons that undergo remodeling during neuronal development and activity-dependent plasticity within the central nervous system. Although group 1 metabotropic glutamate receptors (mGluRs) are critical for spine remodeling under physiopathological conditions, the molecular components linking receptor activity to structural plasticity remain unknown. Here we identify a Ca2+-sensitive actin-binding protein, α-actinin-4, as a novel group 1 mGluR-interacting partner that orchestrates spine dynamics and morphogenesis in primary neurons. Functional silencing of α-actinin-4 abolished spine elongation and turnover stimulated by group 1 mGluRs despite intact surface receptor expression and downstream ERK1/2 signaling. This function of α-actinin-4 in spine dynamics was underscored by gain-of-function phenotypes in untreated neurons. Here α-actinin-4 induced spine head enlargement, a morphological change requiring the C-terminal domain of α-actinin-4 that binds to CaMKII, an interaction we showed to be regulated by group 1 mGluR activation. Our data provide mechanistic insights into spine remodeling by metabotropic signaling and identify α-actinin-4 as a critical effector of structural plasticity within neurons. PMID:25944910

  13. Metabotropic Glutamate 2/3 Receptors and Epigenetic Modifications in Psychotic Disorders: A Review

    PubMed Central

    Matrisciano, Francesco; Panaccione, Isabella; Grayson, Danis R.; Nicoletti, Ferdinando; Guidotti, Alessandro

    2016-01-01

    Schizophrenia and Bipolar Disorder are chronic psychiatric disorders, both considered as “major psychosis”; they are thought to share some pathogenetic factors involving a dysfunctional gene x environment interaction. Alterations in the glutamatergic transmission have been suggested to be involved in the pathogenesis of psychosis. Our group developed an epigenetic model of schizophrenia originated by Prenatal Restraint Stress (PRS) paradigm in mice. PRS mice developed some behavioral alterations observed in schizophrenic patients and classic animal models of schizophrenia, i.e. deficits in social interaction, locomotor activity and prepulse inhibition. They also showed specific changes in promoter DNA methylation activity of genes related to schizophrenia such as reelin, BDNF and GAD67, and altered expression and function of mGlu2/3 receptors in the frontal cortex. Interestingly, behavioral and molecular alterations were reversed by treatment with mGlu2/3 agonists. Based on these findings, we speculate that pharmacological modulation of these receptors could have a great impact on early phase treatment of psychosis together with the possibility to modulate specific epigenetic key protein involved in the development of psychosis. In this review, we will discuss in more details the specific features of the PRS mice as a suitable epigenetic model for major psychosis. We will then focus on key proteins of chromatin remodeling machinery as potential target for new pharmacological treatment through the activation of metabotropic glutamate receptors. PMID:26813121

  14. Blockade of metabotropic glutamate receptor 5 activation inhibits mechanical hypersensitivity following abdominal surgery.

    PubMed

    Dolan, Sharron; Nolan, Andrea Mary

    2007-08-01

    This study used the metabotropic glutamate 5 (mGlu5) receptor subtype-selective antagonist 2-methyl-6-(phenylethynyl)pyridine (MPEP) to characterise the contribution of mGlu5 receptor activity to pain and hypersensitivity in an animal model of post-surgical pain. Adult female Wistar rats (200-250g) were anaesthetised with isoflurane (2%) and underwent a midline laparotomy with gentle manipulation of the viscera, and the effects of pre- (30min) or post- (5h) operative treatment with MPEP (1, 3 or 10mgkg(-1); i.p.) or drug-vehicle on hindpaw withdrawal latency (in seconds) to thermal stimulation (Hargreave's Test) and response threshold (in grams) to mechanical stimulation (using a dynamic plantar aesthesiometer) were measured. Animals that underwent surgery displayed significant hypersensitivity to mechanical stimulation of the hindpaws. Hypersensitivity was maximum at 6h post-surgery (44.5+/-2.4% decrease; p<0.01 vs. anaesthesia only controls) and persisted for 48h. Surgery had no effect on thermal withdrawal latency. Both pre-operative and post-operative administration of 10mgkg(-1)MPEP blocked mechanical hypersensitivity induced by surgery (p<0.01 vs. vehicle treatment). MPEP had no effect on acute nociceptive thresholds in naïve animals. These data suggest that activity at mGlu5 receptors contributes to development of pain and hypersensitivity following surgery.

  15. Super-resolution mapping of glutamate receptors in C. elegans by confocal correlated PALM

    PubMed Central

    Vangindertael, Jeroen; Beets, Isabel; Rocha, Susana; Dedecker, Peter; Schoofs, Liliane; Vanhoorelbeeke, Karen; Hofkens, Johan; Mizuno, Hideaki

    2015-01-01

    Photoactivated localization microscopy (PALM) is a super-resolution imaging technique based on the detection and subsequent localization of single fluorescent molecules. PALM is therefore a powerful tool in resolving structures and putative interactions of biomolecules at the ultimate analytical detection limit. However, its limited imaging depth restricts PALM mostly to in vitro applications. Considering the additional need for anatomical context when imaging a multicellular organism, these limitations render the use of PALM in whole animals difficult. Here we integrated PALM with confocal microscopy for correlated imaging of the C. elegans nervous system, a technique we termed confocal correlated PALM (ccPALM). The neurons, lying below several tissue layers, could be visualized up to 10 μm deep inside the animal. By ccPALM, we visualized ionotropic glutamate receptor distributions in C. elegans with an accuracy of 20 nm, revealing super-resolution structure of receptor clusters that we mapped onto annotated neurons in the animal. Pivotal to our results was the TIRF-independent detection of single molecules, achieved by genetic regulation of labeled receptor expression and localization to effectively reduce the background fluorescence. By correlating PALM with confocal microscopy, this platform enables dissecting biological structures with single molecule resolution in the physiologically relevant context of whole animals. PMID:26323790

  16. Metabotropic glutamate receptor 5 in Down's syndrome hippocampus during development: increased expression in astrocytes.

    PubMed

    Iyer, A M; van Scheppingen, J; Milenkovic, I; Anink, J J; Lim, D; Genazzani, A A; Adle-Biassette, H; Kovacs, G G; Aronica, E

    2014-01-01

    Metabotropic glutamate receptor 5 (mGluR5) is highly expressed throughout the forebrain and hippocampus. Several lines of evidence support the role of this receptor in brain development and developmental disorders, as well as in neurodegenerative disorders like Alzheimer's disease (AD). In the present study, the expression pattern of mGluR5 was investigated by immunocytochemistry in the developing hippocampus from patients with Down's syndrome (DS) and in adults with DS and AD. mGluR5 was expressed in developing human hippocampus from the earliest stages tested (9 gestational weeks), with strong expression in the ventricular/subventricular zones. We observed a consistent similar temporal and spatial neuronal pattern of expression in DS hippocampus. However, in DS we detected increased prenatal mGluR5 expression in white matter astrocytes, which persisted postnatally. In addition, in adult DS patients with widespread ADassociated neurodegeneration (DS-AD) increased mGluR5 expression was detected in astrocytes around amyloid plaque. In vitro data confirm the existence of a modulatory crosstalk between amyloid-β and mGluR5 in human astrocytes. These findings demonstrate a developmental regulation of mGluR5 in human hippocampus and suggest a role for this receptor in astrocytes during early development in DS hippocampus, as well as a potential contribution to the pathogenesis of ADassociated pathology.

  17. Role of glutamate receptors of central and basolateral amygdala nuclei on retrieval and reconsolidation of taste aversive memory.

    PubMed

    Garcia-Delatorre, Paola; Pérez-Sánchez, Consuelo; Guzmán-Ramos, Kioko; Bermúdez-Rattoni, Federico

    2014-05-01

    There are a number of experiments showing an important involvement of amygdala N-methyl-d-aspartate (NMDA) glutamate receptors on consolidation of conditioned taste aversion (CTA) memory. Interestingly, recent evidence has shown that α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) glutamate receptors are particularly involved in CTA retrieval. Memory reconsolidation has been proposed as a destabilization and re-stabilization process induced by memory reactivation. We have recently suggested that reconsolidation could be enabled in the absence of retrieval. Hence, we decided to analyze the participation of AMPA and NMDA receptors of the central (CeA) and basolateral amygdala (BLA) in CTA memory retrieval and reconsolidation. To do so, we tested whether administrations of an AMPA receptor blocker (NBQX) or an NMDA receptor blocker (APV) 15 min before a second acquisition trial could have effects on taste aversion. We found that administration of NBQX in the BLA blocked retrieval, whereas APV blocked reconsolidation in the BLA, and consolidation in the CeA. When we administered both NBQX and APV into the BLA before the second acquisition trial, results showed impairment of both retrieval and reconsolidation. These results further support the idea that reconsolidation is independent of retrieval, since retrieval blockade in the BLA did not impair memory reconsolidation. These results suggest that glutamate receptors have different participation on retrieval and reconsolidation of CTA and further support the hypothesis that these two processes could be independent.

  18. Metabotropic glutamate receptor 1 disrupts mammary acinar architecture and initiates malignant transformation of mammary epithelial cells

    PubMed Central

    Teh, Jessica L. F.; Shah, Raj; La Cava, Stephanie; Dolfi, Sonia C.; Mehta, Madhura S.; Kongara, Sameera; Price, Sandy; Ganesan, Shridar; Reuhl, Kenneth R.; Hirshfield, Kim M.

    2016-01-01

    Metabotropic glutamate receptor 1 (mGluR1/Grm1) is a member of the G-protein-coupled receptor superfamily, which was once thought to only participate in synaptic transmission and neuronal excitability, but has more recently been implicated in non-neuronal tissue functions. We previously described the oncogenic properties of Grm1 in cultured melanocytes in vitro and in spontaneous melanoma development with 100 % penetrance in vivo. Aberrant mGluR1 expression was detected in 60–80 % of human melanoma cell lines and biopsy samples. As most human cancers are of epithelial origin, we utilized immortalized mouse mammary epithelial cells (iMMECs) as a model system to study the transformative properties of Grm1. We introduced Grm1 into iMMECs and isolated several stable mGluR1-expressing clones. Phenotypic alterations in mammary acinar architecture were assessed using three-dimensional morphogenesis assays. We found that mGluR1-expressing iMMECs exhibited delayed lumen formation in association with decreased central acinar cell death, disrupted cell polarity, and a dramatic increase in the activation of the mitogen-activated protein kinase pathway. Orthotopic implantation of mGluR1-expressing iMMEC clones into mammary fat pads of immunodeficient nude mice resulted in mammary tumor formation in vivo. Persistent mGluR1 expression was required for the maintenance of the tumorigenic phenotypes in vitro and in vivo, as demonstrated by an inducible Grm1-silencing RNA system. Furthermore, mGluR1 was found be expressed in human breast cancer cell lines and breast tumor biopsies. Elevated levels of extracellular glutamate were observed in mGluR1-expressing breast cancer cell lines and concurrent treatment of MCF7 xenografts with glutamate release inhibitor, riluzole, and an AKT inhibitor led to suppression of tumor progression. Our results are likely relevant to human breast cancer, highlighting a putative role of mGluR1 in the pathophysiology of breast cancer and the potential

  19. Immunohistochemical Localization of AMPA Type Glutamate Receptor Subunits in the Striatum of Rhesus Monkey

    PubMed Central

    Deng, Yun-Ping; Shelby, Evan; Reiner, Anton J.

    2010-01-01

    Corticostriatal and thalamostriatal projections utilize glutamate as their neurotransmitter. Their influence on striatum is mediated, in part, by ionotropic AMPA-type glutamate receptors, which are heteromers composed of GluR1-4 subunits. While the cellular localization of AMPA-type subunits in the basal ganglia has been well characterized in rodents, the cellular localization of AMPA subunits in primate basal ganglia is not. We thus carried out immunohistochemical studies of GluR1-4 distribution in rhesus monkey basal ganglia in conjunction with characterization of each major neuron type. In striatum, about 65% of striatal neurons immunolabeled for GluR1, 75%-79% immunolabeled for GluR2 or GluR2/3, and only 2.5% possessed GluR4. All neurons the large size of cholinergic interneurons (mean diameter 26.1μm) were moderately labeled for GluR1, while all neurons in the size range of parvalbuminergic interneurons (mean diameter 13.8μm) were intensely rich in GluR1. Additionally, somewhat more than half of neurons in the size range of projection neurons (mean diameter 11.6μm) immunolabeled for GluR1, and about one third of these were very rich in GluR1. About half of neurons the size of cholinergic interneurons were immunolabeled for GluR2, and the remainder of the neurons that were immunolabeled for GluR2 coincided with projection neurons in size and shape (GluR2 diameter=10.7μm), indicating that the vast majority of striatal projection neurons possess immunodectible GluR2. Similar results were observed with GluR2/3 immunolabeling. Half of the neurons the size of cholinergic interneurons immunolabeled for GluR4 and seemingly all neurons in the size range of parvalbuminergic interneurons possessed GluR4. These results indicate that AMPA receptor subunit combinations for striatal projection neurons in rhesus monkey are similar to those for the corresponding neuron types in rodents, and thus their AMPA responses to glutamate likely to be similar to those demonstrated

  20. Pharmacological characterization of (4R)-alkyl glutamate analogues at the ionotropic glutamate receptors--focus on subtypes iGlu(5-7).

    PubMed

    Bunch, Lennart; Gefflaut, Thierry; Alaux, Sebastien; Sagot, Emanuelle; Nielsen, Birgitte; Pickering, Darryl S

    2009-05-01

    The kainic acid (kainate, KA) receptors belong to the class of ionotropic glutamate (iGlu) receptors in the central nervous system. Five subtypes have been identified, which have been termed KA(1,2) and iGlu(5-7). In the search for subtype selective ligands, alpha-amino-5-tert-butyl-3-hydroxy-4-isoxazolyl)propionic acid (ATPA), (4R)-methyl Glu (1a), and E-4-neopentylidene Glu (2f) have all previously been reported as selective agonists for the iGlu(5) receptor subtype. In this paper, we present the pharmacological evaluation of a five-compound series of (4R)-alkyl Glu analogs (1b-e,g) which may be envisaged as conformationally released designs of ATPA and 4-alkylidenes 2a-h. Most notable is the pharmacological profile for (4R)-isopentyl Glu (1g) which shows a 10-fold increase in binding affinity for the iGlu(5) receptor subtype (K(i)=20.5 nM) in comparison with its E-4-alkylidene structural isomer 2g. Furthermore, 1g displays high selectivity over other KA receptor subtypes (KA(1,2) and iGlu(6,7)), AMPA-, and NMDA receptors (2050 and >5000 fold, respectively).

  1. Activation of NOX2 by the stimulation of ionotropic and metabotropic glutamate receptors contributes to glutamate neurotoxicity in vivo through the production of reactive oxygen species and calpain activation.

    PubMed

    Guemez-Gamboa, Alicia; Estrada-Sánchez, Ana María; Montiel, Teresa; Páramo, Blanca; Massieu, Lourdes; Morán, Julio

    2011-11-01

    Prolonged activation of glutamate receptors leads to excitotoxicity. Several processes such as reactive oxygen species (ROS) production and activation of the calcium-dependent protease, calpain, contribute to glutamate-induced damage. It has been suggested that the ROS-producing enzyme, NADPH oxidase (NOX), plays a role in excitotoxicity. Studies have reported NOX activation after NMDA receptor stimulation during excitotoxic damage, but the role of non-NMDA and metabotropic receptors is unknown. We evaluated the roles of different glutamate receptor subtypes on NOX activation and neuronal death induced by the intrastriatal administration of glutamate in mice. In wild-type mice, NOX2 immunoreactivity in neurons and microglia was stimulated by glutamate administration, and it progressively increased as microglia became activated; calpain activity was also induced. By contrast, mice lacking NOX2 were less vulnerable to excitotoxicity, and there was reduced ROS production and protein nitrosylation, microglial reactivity, and calpain activation. These results suggest that NOX2 is stimulated by glutamate in neurons and reactive microglia through the activation of ionotropic and metabotropic receptors. Neuronal damage involves ROS production by NOX2, which, in turn, contributes to calpain activation.

  2. Protease activated receptor 1-induced glutamate release in cultured astrocytes is mediated by Bestrophin-1 channel but not by vesicular exocytosis

    PubMed Central

    2012-01-01

    Background Glutamate is the major transmitter that mediates the principal form of excitatory synaptic transmission in the brain. It has been well established that glutamate is released via Ca2+-dependent exocytosis of glutamate-containing vesicles in neurons. However, whether astrocytes exocytose to release glutamate under physiological condition is still unclear. Findings We report a novel form of glutamate release in astrocytes via the recently characterized Ca2+-activated anion channel, Bestrophin-1 (Best1) by Ca2+ dependent mechanism through the channel pore. We demonstrate that upon activation of protease activated receptor 1 (PAR1), an increase in intracellular Ca2+ concentration leads to an opening of Best1 channels and subsequent release of glutamate in cultured astrocytes. Conclusions These results provide strong molecular evidence for potential astrocyte-neuron interaction via Best1-mediated glutamate release. PMID:23062602

  3. Activation of presynaptic oxytocin receptors enhances glutamate release in the ventral hippocampus of prenatally restraint stressed rats.

    PubMed

    Mairesse, Jérôme; Gatta, Eleonora; Reynaert, Marie-Line; Marrocco, Jordan; Morley-Fletcher, Sara; Soichot, Marion; Deruyter, Lucie; Camp, Gilles Van; Bouwalerh, Hammou; Fagioli, Francesca; Pittaluga, Anna; Allorge, Delphine; Nicoletti, Ferdinando; Maccari, Stefania

    2015-12-01

    Oxytocin receptors are known to modulate synaptic transmission and network activity in the hippocampus, but their precise function has been only partially elucidated. Here, we have found that activation of presynaptic oxytocin receptor with the potent agonist, carbetocin, enhanced depolarization-evoked glutamate release in the ventral hippocampus with no effect on GABA release. This evidence paved the way for examining the effect of carbetocin treatment in "prenatally restraint stressed" (PRS) rats, i.e., the offspring of dams exposed to repeated episodes of restraint stress during pregnancy. Adult PRS rats exhibit an anxious/depressive-like phenotype associated with an abnormal glucocorticoid feedback regulation of the hypothalamus-pituitary-adrenal (HPA) axis, and, remarkably, with a reduced depolarization-evoked glutamate release in the ventral hippocampus. Chronic systemic treatment with carbetocin (1mg/kg, i.p., once a day for 2-3 weeks) in PRS rats corrected the defect in glutamate release, anxiety- and depressive-like behavior, and abnormalities in social behavior, in the HPA response to stress, and in the expression of stress-related genes in the hippocampus and amygdala. Of note, carbetocin treatment had no effect on these behavioral and neuroendocrine parameters in prenatally unstressed (control) rats, with the exception of a reduced expression of the oxytocin receptor gene in the amygdala. These findings disclose a novel function of oxytocin receptors in the hippocampus, and encourage the use of oxytocin receptor agonists in the treatment of stress-related psychiatric disorders in adult life.

  4. Glutamate controls the induction of GABA-mediated giant depolarizing potentials through AMPA receptors in neonatal rat hippocampal slices.

    PubMed

    Bolea, S; Avignone, E; Berretta, N; Sanchez-Andres, J V; Cherubini, E

    1999-05-01

    Glutamate controls the induction of GABA-mediated giant depolarizing potentials through AMPA receptors in neonatal rat hippocampal slices. Giant depolarizing potentials (GDPs) are generated by the interplay of the depolarizing action of GABA and glutamate. In this study, single and dual whole cell recordings (in current-clamp configuration) were performed from CA3 pyramidal cells in hippocampal slices obtained from postnatal (P) days P1- to P6-old rats to evaluate the role of ionotropic glutamate receptors in GDP generation. Superfusion of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) (10-40 microM) completely blocked GDPs. However, in the presence of CNQX, it was still possible to re-induce the appearance of GDPs with GABA (20 microM) or (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxadepropionate (AMPA) (5 microM). This effect was prevented by the more potent and selective AMPA receptor antagonist GYKI 53655 (50-100 microM). In the presence of GYKI 53655, both kainic or domoic acid (0.1-1 microM) were unable to induce GDPs. In contrast, bath application of D-(-)-2-amino-5-phosphonopentanoic acid (50 microM) or (+)-3-(2carboxy-piperazin-4-yl)-propyl-L-phosphonic acid (20 microM) produced only a 37 +/- 9% (SE) and 36 +/- 11% reduction in GDPs frequency, respectively. Cyclothiazide, a selective blocker of AMPA receptor desensitization, increased GDP frequency by 76 +/- 14%. Experiments were also performed with an intracellular solution containing KF to block GABAA receptor-mediated responses. In these conditions, a glutamatergic component of GDP was revealed. GDPs could still be recorded synchronous with those detected simultaneously with KCl-filled electrodes, although their amplitude was smaller. Similar results were found in pair recordings obtained from minislices containing only a small portion of the CA3 area. These data suggest that GDP generation requires activation of AMPA receptors by local release of glutamate from recurrent collaterals.

  5. The Metabotropic Glutamate 5 Receptor Modulates Extinction and Reinstatement of Methamphetamine-Seeking in Mice

    PubMed Central

    Chesworth, Rose; Brown, Robyn M.; Kim, Jee Hyun; Lawrence, Andrew J.

    2013-01-01

    Methamphetamine (METH) is a highly addictive psychostimulant with no therapeutics registered to assist addicts in discontinuing use. Glutamatergic dysfunction has been implicated in the development and maintenance of addiction. We sought to assess the involvement of the metabotropic glutamate 5 receptor (mGlu5) in behaviours relevant to METH addiction because this receptor has been implicated in the actions of other drugs of abuse, including alcohol, cocaine and opiates. mGlu5 knockout (KO) mice were tested in intravenous self-administration, conditioned place preference and locomotor sensitization. Self-administration of sucrose was used to assess the response of KO mice to a natural reward. Acquisition and maintenance of self-administration, as well as the motivation to self-administer METH was intact in mGlu5 KO mice. Importantly, mGlu5 KO mice required more extinction sessions to extinguish the operant response for METH, and exhibited an enhanced propensity to reinstate operant responding following exposure to drug-associated cues. This phenotype was not present when KO mice were tested in an equivalent paradigm assessing operant responding for sucrose. Development of conditioned place preference and locomotor sensitization were intact in KO mice; however, conditioned hyperactivity to the context previously paired with drug was elevated in KO mice. These data demonstrate a role for mGlu5 in the extinction and reinstatement of METH-seeking, and suggests a role for mGlu5 in regulating contextual salience. PMID:23861896

  6. Disruption of glutamate receptor-interacting protein in nucleus accumbens enhances vulnerability to cocaine relapse.

    PubMed

    Briand, Lisa A; Kimmey, Blake A; Ortinski, Pavel I; Huganir, Richard L; Pierce, R Christopher

    2014-02-01

    Trafficking and stabilization of AMPA receptors at synapses in response to cocaine exposure is thought to be critical for expression of cocaine addiction and relapse. Glutamate receptor-interacting protein (GRIP) is a neuronal scaffolding protein that stabilizes GluA2 AMPARs at synapses but its role in cocaine addiction has not been examined. The current study demonstrates that conditional deletion of GRIP within the nucleus accumbens potentiates cue-induced reinstatement of cocaine seeking without affecting operant learning, locomotor activity, or reinstatement of natural reward seeking. This is the first study to demonstrate a role for accumbal GRIP in behavior. Electrophysiological recordings revealed increased rectification of AMPAR-mediated currents in the nucleus accumbens and increased AMPAR sensitivity to the GluA2-lacking AMPAR antagonist, 1-naphthylacetyl spermine, indicative of an increased contribution of GluA2-lacking calcium-permeable AMPARs. In addition, accumbal GRIP deletion was associated with blunted long-term depression, similar to what is seen following cocaine self-administration. Taken together, these results indicate that GRIP may modulate addictive phenotypes through its regulation of synaptic AMPARs by controlling their subunit composition and susceptibility to LTD. These effects are associated with changes in vulnerability to cocaine relapse and highlight GRIP as a novel target for the development of cocaine addiction therapeutics.

  7. Group II Metabotropic Glutamate Receptors as Targets for Novel Antipsychotic Drugs

    PubMed Central

    Muguruza, Carolina; Meana, J. Javier; Callado, Luis F.

    2016-01-01

    Schizophrenia is a chronic psychiatric disorder which substantially impairs patients’ quality of life. Despite the extensive research in this field, the pathophysiology and etiology of schizophrenia remain unknown. Different neurotransmitter systems and functional networks have been found to be affected in the brain of patients with schizophrenia. In this context, postmortem brain studies as well as genetic assays have suggested alterations in Group II metabotropic glutamate receptors (mGluRs) in schizophrenia. Despite many years of drug research, several needs in the treatment of schizophrenia have not been addressed sufficiently. In fact, only 5–10% of patients with schizophrenia successfully achieve a full recovery after treatment. In recent years mGluRs have turned up as novel targets for the design of new antipsychotic medications for schizophrenia. Concretely, Group II mGluRs are of particular interest due to their regulatory role in neurotransmission modulating glutamatergic activity in brain synapses. Preclinical studies have demonstrated that orthosteric Group II mGluR agonists exhibit antipsychotic-like properties in animal models of schizophrenia. However, when these compounds have been tested in human clinical studies with schizophrenic patients results have been inconclusive. Nevertheless, it has been recently suggested that this apparent lack of efficacy in schizophrenic patients may be related to previous exposure to atypical antipsychotics. Moreover, the role of the functional heterocomplex formed by 5-HT2A and mGlu2 receptors in the clinical response to Group II mGluR agonists is currently under study. PMID:27242534

  8. NR2B subunit of the NMDA glutamate receptor regulates appetite in the parabrachial nucleus.

    PubMed

    Wu, Qi; Zheng, Ruimao; Srisai, Dollada; McKnight, G Stanley; Palmiter, Richard D

    2013-09-03

    Diphtheria toxin-mediated, acute ablation of hypothalamic neurons expressing agouti-related protein (AgRP) in adult mice leads to anorexia and starvation within 7 d that is caused by hyperactivity of neurons within the parabrachial nucleus (PBN). Because NMDA glutamate receptors are involved in various synaptic plasticity-based behavioral modifications, we hypothesized that modulation of the NR2A and NR2B subunits of the NMDA receptor in PBN neurons could contribute to the anorexia phenotype. We observed by Western blot analyses that ablation of AgRP neurons results in enhanced expression of NR2B along with a modest suppression of NR2A. Interestingly, systemic administration of LiCl in a critical time window before AgRP neuron ablation abolished the anorectic response. LiCl treatment suppressed NR2B levels in the PBN and ameliorated the local Fos induction that is associated with anorexia. This protective role of LiCl on feeding was blunted in vagotomized mice. Chronic infusion of RO25-6981, a selective NR2B inhibitor, into the PBN recapitulated the role of LiCl in maintaining feeding after AgRP neuron ablation. We suggest that the accumulation of NR2B subunits in the PBN contributes to aphagia in response to AgRP neuron ablation and may be involved in other forms of anorexia.

  9. Metabotropic glutamate receptor-mediated long-term depression: molecular mechanisms.

    PubMed

    Gladding, Clare M; Fitzjohn, Stephen M; Molnár, Elek

    2009-12-01

    The ability to modify synaptic transmission between neurons is a fundamental process of the nervous system that is involved in development, learning, and disease. Thus, synaptic plasticity is the ability to bidirectionally modify transmission, where long-term potentiation and long-term depression (LTD) represent the best characterized forms of plasticity. In the hippocampus, two main forms of LTD coexist that are mediated by activation of either N-methyl-d-aspartic acid receptors (NMDARs) or metabotropic glutamate receptors (mGluRs). Compared with NMDAR-LTD, mGluR-LTD is less well understood, but recent advances have started to delineate the underlying mechanisms. mGluR-LTD at CA3:CA1 synapses in the hippocampus can be induced either by synaptic stimulation or by bath application of the group I selective agonist (R,S)-3,5-dihydroxyphenylglycine. Multiple signaling mechanisms have been implicated in mGluR-LTD, illustrating the complexity of this form of plasticity. This review provides an overview of recent studies investigating the molecular mechanisms underlying hippocampal mGluR-LTD. It highlights the role of key molecular components and signaling pathways that are involved in the induction and expression of mGluR-LTD and considers how the different signaling pathways may work together to elicit a persistent reduction in synaptic transmission.

  10. Conformational Plasticity in the Transsynaptic Neurexin-Cerebellin-Glutamate Receptor Adhesion Complex

    SciTech Connect

    Cheng, Shouqiang; Seven, Alpay B.; Wang, Jing; Skiniotis, Georgios; Özkan, Engin

    2016-12-01

    Synaptic specificity is a defining property of neural networks. In the cerebellum, synapses between parallel fiber neurons and Purkinje cells are specified by the simultaneous interactions of secreted protein cerebellin with pre-synaptic neurexin and post-synaptic delta-type glutamate receptors (GluD). Here, we determined the crystal structures of the trimeric C1q-like domain of rat cerebellin-1, and the first complete ectodomain of a GluD, rat GluD2. Cerebellin binds to the LNS6 domain of α- and β-neurexin-1 through a high-affinity interaction that involves its highly flexible N-terminal domain. In contrast, we show that the interaction of cerebellin with isolated GluD2 ectodomain is low affinity, which is not simply an outcome of lost avidity when compared with binding with a tetrameric full-length receptor. Rather, high-affinity capture of cerebellin by post-synaptic terminals is likely controlled by long-distance regulation within this transsynaptic complex. Altogether, our results suggest unusual conformational flexibility within all components of the complex.

  11. Operant sensation seeking requires metabotropic glutamate receptor 5 (mGluR5).

    PubMed

    Olsen, Christopher M; Childs, Daniel S; Stanwood, Gregg D; Winder, Danny G

    2010-11-30

    Pharmacological and genetic studies have suggested that the metabotropic glutamate receptor 5 (mGluR5) is critically involved in mediating the reinforcing effects of drugs of abuse, but not food. The purpose of this study was to use mGluR5 knockout (KO), heterozygous (Het), and wildtype (WT) mice to determine if mGluR5 modulates operant sensation seeking (OSS), an operant task that uses varied sensory stimuli as a reinforcer. We found that mGluR5 KO mice had significantly reduced OSS responding relative to WT mice, while Het mice displayed a paradoxical increase in OSS responding. Neither KO nor Het mice exhibited altered operant responding for food as a reinforcer. Further, we assessed mGluR5 KO, Het and WT mice across a battery of cocaine locomotor, place preference and anxiety related tests. Although KO mice showed expected differences in some locomotor and anxiety measures, Het mice either exhibited no phenotype or an intermediate one. In total, these data demonstrate a key role for mGluR5 in OSS, indicating an important role for this receptor in reinforcement-based behavior.

  12. The metabotropic glutamate 5 receptor modulates extinction and reinstatement of methamphetamine-seeking in mice.

    PubMed

    Chesworth, Rose; Brown, Robyn M; Kim, Jee Hyun; Lawrence, Andrew J

    2013-01-01

    Methamphetamine (METH) is a highly addictive psychostimulant with no therapeutics registered to assist addicts in discontinuing use. Glutamatergic dysfunction has been implicated in the development and maintenance of addiction. We sought to assess the involvement of the metabotropic glutamate 5 receptor (mGlu5) in behaviours relevant to METH addiction because this receptor has been implicated in the actions of other drugs of abuse, including alcohol, cocaine and opiates. mGlu5 knockout (KO) mice were tested in intravenous self-administration, conditioned place preference and locomotor sensitization. Self-administration of sucrose was used to assess the response of KO mice to a natural reward. Acquisition and maintenance of self-administration, as well as the motivation to self-administer METH was intact in mGlu5 KO mice. Importantly, mGlu5 KO mice required more extinction sessions to extinguish the operant response for METH, and exhibited an enhanced propensity to reinstate operant responding following exposure to drug-associated cues. This phenotype was not present when KO mice were tested in an equivalent paradigm assessing operant responding for sucrose. Development of conditioned place preference and locomotor sensitization were intact in KO mice; however, conditioned hyperactivity to the context previously paired with drug was elevated in KO mice. These data demonstrate a role for mGlu5 in the extinction and reinstatement of METH-seeking, and suggests a role for mGlu5 in regulating contextual salience.

  13. The effects of development of a food-related operant reflex on the receptor binding of glutamate in the rat brain.

    PubMed

    Karpova, I V

    1999-01-01

    Receptor binding of glutamate was studied in the striatum, hippocampus, and cerebral cortex of rats with different abilities to acquire an operant food-related reflex in a Skinner box. The striatum of rapidly-learning rats and rats unable to learn showed significantly higher levels of glutamate binding than controls were not trained in the Skinner box (p < 0.05). Striatal receptor binding of glutamate in slow-learning rats was lower than that in rapidly-learning rats and rats which were unable to learn (p < 0.05). In the hippocampus, all groups of rats (rapidly-learning, slow-learning, and those unable to learn) showed increased receptor binding of glutamate as compared with controls (p < 0.05), in the cerebral cortex, there was a significant decrease in glutamate binding as compared with controls in all groups of animals subjected to training (p < 0.05).

  14. [The blocade of glutamate metabotropic 5-th tipe receptors prevents the locomotor behavior changes produced by intrastriatal picrotoxin microinjections in rats].

    PubMed

    Iakimovskiĭ, A F; Red'ka, Iu A; Iakubenko, A L

    2010-01-01

    It was demonstrated in chronic experiments in Wistar rats that only the first of daily multiple microinjections of glutamate metabotropic 5-th type receptor antagonist MTEP into the rostral region of neostriatum impaired the avoidance conditioning in a shuttle box. Within the next two weeks, MTEP was ineffective but being injected into the neostriatum simultaneously with picrotoxin prevented the impairment of avoidance conditioning in a shuttle-box and decreased the hyperactivity (open-field locomotor hyperactivity and choreic hyperkinesis) produced by this GABA-A receptor antagonist. The results do not suggest the involvement of striatal glutamate metabotropic 5-th type receptors in avoidance conditioning control but demonstrate that glutamate metabotropic system is involved in behavioral disorders mediated by inhibition of GABA-A receptors. In principle, it might be possible to treat the human hyperkinetic basal ganglia dysfunction (Huntington's horea), athetosis and similar disorders with glutamate metabotropic receptor antagonists.

  15. Cannabinoid Receptors Couple to NMDA Receptors to Reduce the Production of NO and the Mobilization of Zinc Induced by Glutamate

    PubMed Central

    Sánchez-Blázquez, Pilar; Rodríguez-Muñoz, María; Vicente-Sánchez, Ana

    2013-01-01

    Abstract Aims: Overactivation of glutamate N-methyl-D-aspartate receptor (NMDAR) increases the cytosolic concentrations of calcium and zinc, which significantly contributes to neural death. Since cannabinoids prevent the NMDAR-mediated increase in cytosolic calcium, we investigated whether they also control the rise of potentially toxic free zinc ions, as well as the processes implicated in this phenomenon. Results: The cannabinoid receptors type 1 (CNR1) and NMDARs are cross-regulated in different regions of the nervous system. Cannabinoids abrogated the stimulation of the nitric oxide-zinc pathway by NMDAR, an effect that required the histidine triad nucleotide-binding protein 1 (HINT1). Conversely, NMDAR antagonism reduced the analgesia promoted by the CNR1 agonist WIN55,212-2 and impaired its capacity to internalize CNR1s. At the cell surface, CNR1s co-immunoprecipitated with the NR1 subunits of NMDARs, an association that diminished after the administration of NMDA in vivo or as a consequence of neuropathic overactivation of NMDARs, both situations in which cannabinoids do not control NMDAR activity. Under these circumstances, inhibition of protein kinase A (PKA) restored the association between CNR1s and NR1 subunits, and cannabinoids regained control over NMDAR activity. Notably, CNR1 and NR1 associated poorly in HINT1−/− mice, in which there was little cross-regulation between these receptors. Innovation: The CNR1 can regulate NMDAR function when the receptor is coupled to HINT1. Thus, internalization of CNR1s drives the co-internalization of the NR1 subunits, neutralizing the overactivation of NMDARs. Conclusion: Cannabinoids require the HINT1 protein to counteract the toxic effects of NMDAR-mediated NO production and zinc release. This study situates the HINT1 protein at the forefront of cannabinoid protection against NMDAR-mediated brain damage. Antioxid. Redox Signal. 19, 1766–1782. PMID:23600761

  16. Double Dissociation of the Roles of Metabotropic Glutamate Receptor 5 and Oxytocin Receptor in Discrete Social Behaviors

    PubMed Central

    Mesic, Ivana; Guzman, Yomayra F; Guedea, Anita L; Jovasevic, Vladimir; Corcoran, Kevin A; Leaderbrand, Katherine; Nishimori, Katsuhiko; Contractor, Anis; Radulovic, Jelena

    2015-01-01

    Social interactions in vertebrates are complex phenomena based on affective and cognitive processes. Multiple brain regions and neurotransmitter systems are involved in the expression of social behaviors, but their individual roles in specific aspects of social interactions are not well understood. Here we investigated how Gq-protein-coupled metabotropic glutamate receptor 5 (mGluR5) and oxytocin receptor (Oxtr) affect social affiliation and social memory. We used conditional genetic approaches in which the genes coding for these receptors were knocked out in the lateral septum by infusion of recombinant adeno-associated viral vectors containing Cre recombinase (AAV-Cre). Social behavior was assessed 2 weeks later using a three-chamber paradigm for sociability and preference for social novelty. Septal deletion of mGluR5 abolished sociability while leaving preference for social novelty intact. In contrast, deletion of Oxtr did not affect sociability but significantly impaired preference for social novelty. Nonsocial behaviors or memories, including novel object recognition or fear conditioning, were not affected by these genetic manipulations. Immunohistochemical analyses of the distribution of mGluR5 and Oxtr revealed non-overlapping localization of these receptors within the lateral septum, suggesting that not only different neurotransmitters but also different neuronal types contribute to sociability versus preference for social novelty. Our findings identify highly specialized roles of lateral septal mGluR5 and Oxtr in the the regulation of discrete social behaviors, and suggest that deficits in social interactions, which accompany many mental illnesses, would benefit from comprehensive treatments targeting different components of social functioning. PMID:25824423

  17. Pharmacological and molecular characterization of the positive allosteric modulators of metabotropic glutamate receptor 2.

    PubMed

    Lundström, L; Bissantz, C; Beck, J; Dellenbach, M; Woltering, T J; Wichmann, J; Gatti, S

    2017-02-16

    The metabotropic glutamate receptor 2 (mGlu2) plays an important role in the presynaptic control of glutamate release and several mGlu2 positive allosteric modulators (PAMs) have been under assessment for their potential as antipsychotics. The binding mode of mGlu2 PAMs is better characterized in functional terms while few data are available on the relationship between allosteric and orthosteric binding sites. Pharmacological studies characterizing binding and effects of two different chemical series of mGlu2 PAMs are therefore carried out here using the radiolabeled mGlu2 agonist (3)[H]-LY354740 and mGlu2 PAM (3)[H]-2,2,2-TEMPS. A multidimensional approach to the PAM mechanism of action shows that mGlu2 PAMs increase the affinity of (3)[H]-LY354740 for the orthosteric site of mGlu2 as well as the number of (3)[H]-LY354740 binding sites. (3)[H]-2,2,2-TEMPS binding is also enhanced by the presence of LY354740. New residues in the allosteric rat mGlu2 binding pocket are identified to be crucial for the PAMs ligand binding, among these Tyr(3.40) and Asn(5.46). Also of remark, in the described experimental conditions S731A (Ser(5.42)) residue is important only for the mGlu2 PAM LY487379 and not for the compound PAM-1: an example of the structural differences among these mGlu2 PAMs. This study provides a summary of the information generated in the past decade on mGlu2 PAMs adding a detailed molecular investigation of PAM binding mode. Differences among mGlu2 PAM compounds are discussed as well as the mGlu2 regions interacting with mGlu2 PAM and NAM agents and residues driving mGlu2 PAM selectivity.

  18. Metabotropic glutamate receptor 5 positive allosteric modulators are neuroprotective in a mouse model of Huntington's disease

    PubMed Central

    Doria, JG; Silva, FR; Souza, JM; Vieira, LB; Carvalho, TG; Reis, HJ; Pereira, GS; Dobransky, T; Ribeiro, FM

    2013-01-01

    Background and Purpose Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by a polyglutamine expansion in the huntingtin protein. We have previously demonstrated that the cell signalling of the metabotropic glutamate receptor 5 (mGluR5) is altered in a mouse model of HD. Although mGluR5-dependent protective pathways are more activated in HD neurons, intracellular Ca2+ release is also more pronounced, which could contribute to excitotoxicity. In the present study, we aim to investigate whether mGluR5 positive allosteric modulators (PAMs) could activate protective pathways without triggering high levels of Ca2+ release and be neuroprotective in HD. Experimental Approach We performed a neuronal cell death assay to determine which drugs are neuroprotective, Western blot and Ca2+ release experiments to investigate the molecular mechanisms involved in this neuroprotection, and object recognition task to determine whether the tested drugs could ameliorate HD memory deficit. Key Results We find that mGluR5 PAMs can protect striatal neurons from the excitotoxic neuronal cell death promoted by elevated concentrations of glutamate and NMDA. mGluR5 PAMs are capable of activating Akt without triggering increased intracellular Ca2+ concentration ([Ca2+]i); and Akt blockage leads to loss of PAM-mediated neuroprotection. Importantly, PAMs' potential as drugs that may be used to treat neurodegenerative diseases is highlighted by the neuroprotection exerted by mGluR5 PAMs on striatal neurons from a mouse model of HD, BACHD. Moreover, mGluR5 PAMs can activate neuroprotective pathways more robustly in BACHD mice and ameliorate HD memory deficit. Conclusions and Implications mGluR5 PAMs are potential drugs that may be used to treat neurodegenerative diseases, especially HD. PMID:23489026

  19. Pharmacological and molecular characterization of the positive allosteric modulators of metabotropic glutamate receptor 2.

    PubMed

    Lundström, L; Bissantz, C; Beck, J; Dellenbach, M; Woltering, T J; Wichmann, J; Gatti, S

    2016-12-01

    The metabotropic glutamate receptor 2 (mGlu2) plays an important role in the presynaptic control of glutamate release and several mGlu2 positive allosteric modulators (PAMs) have been under assessment for their potential as antipsychotics. The binding mode of mGlu2 PAMs is better characterized in functional terms while few data are available on the relationship between allosteric and orthosteric binding sites. Pharmacological studies characterizing binding and effects of two different chemical series of mGlu2 PAMs are therefore carried out here using the radiolabeled mGlu2 agonist (3)[H]-LY354740 and mGlu2 PAM (3)[H]-2,2,2-TEMPS. A multidimensional approach to the PAM mechanism of action shows that mGlu2 PAMs increase the affinity of (3)[H]-LY354740 for the orthosteric site of mGlu2 as well as the number of (3)[H]-LY354740 binding sites. (3)[H]-2,2,2-TEMPS binding is also enhanced by the presence of LY354740. New residues in the allosteric rat mGlu2 binding pocket are identified to be crucial for the PAMs ligand binding, among these Tyr(3.40) and Asn(5.46). Also of remark, in the described experimental conditions S731A (Ser(5.42)) residue is important only for the mGlu2 PAM LY487379 and not for the compound PAM-1: an example of the structural differences among these mGlu2 PAMs. This study provides a summary of the information generated in the past decade on mGlu2 PAMs adding a detailed molecular investigation of PAM binding mode. Differences among mGlu2 PAM compounds are discussed as well as the mGlu2 regions interacting with mGlu2 PAM and NAM agents and residues driving mGlu2 PAM selectivity.

  20. Oral administration of MSG increases expression of glutamate receptors and transporters in the gastrointestinal tract of young piglets.

    PubMed

    Zhang, Jun; Yin, Yulong; Shu, Xu Gang; Li, Tiejun; Li, Fengna; Tan, Bie; Wu, Zhenlong; Wu, Guoyao

    2013-11-01

    Glutamate receptors and transporters, including T1R1 and T1R3 (taste receptor 1, subtypes 1 and 3), mGluRs (metabotropic glutamate receptors), EAAC-1 (excitatory amino acid carrier-1), GLAST-1 (glutamate-aspartate transporter-1), and GLT-1 (glutamate transporter-1), are expressed in the gastrointestinal tract. This study determined effects of oral administration of monosodium glutamate [MSG; 0, 0.06, 0.5, or 1 g/kg body weight (BW)/day] for 21 days on expression of glutamate receptors and transporters in the stomach and jejunum of sow-reared piglets. Both mRNA and protein levels for gastric T1R1, T1R3, mGluR1, mGluR4, EAAT1, EAAT2, EAAT3, and EAAT4 and mRNA levels for jejunal T1R1, T1R3, EAAT1, EAAT2, EAAT3 and EAAT4 were increased (P < 0.05) by MSG supplementation. Among all groups, mRNA levels for gastric EAAT1, EAAT2, EAAT3, and EAAT4 were highest (P < 0.05) in piglets receiving 1 g MSG/kg BW/day. EAAT1 and EAAT2 mRNA levels in the stomach and jejunum of piglets receiving 0.5 g MSG/kg BW/day, as well as jejunal EAAT3 and EAAT4 mRNA levels in piglets receiving 1 g MSG/kg BW/day, were higher (P < 0.05) than those in the control and in piglets receiving 0.06 g MSG/kg BW/day. Furthermore, protein levels for jejunal T1R1 and EAAT3 were higher (P < 0.05) in piglets receiving 1 g MSG/kg BW/day than those in the control and in piglets receiving 0.06 g MSG/kg BW/day. Collectively, these findings indicate that dietary MSG may beneficially stimulate glutamate signaling and sensing in the stomach and jejunum of young pigs, as well as their gastrointestinal function.

  1. Sequential expression of cyclooxygenase-2, glutamate receptor-2, and platelet activating factor receptor in rat hippocampal neurons after fluid percussion injury

    PubMed Central

    Li, Zhiqiang; Shu, Qingming; Li, Lingzhi; Ge, Maolin; Zhang, Yongliang

    2014-01-01

    Traumatic brain injury causes gene expression changes in different brain regions. Occurrence and development of traumatic brain injury are closely related, involving expression of three factors, namely cyclooxygenase-2, glutamate receptor-2, and platelet activating factor receptor. However, little is known about the correlation of these three factors and brain neuronal injury. In this study, primary cultured rat hippocampal neurons were subjected to fluid percussion injury according to Scott's method, with some modifications. RT-PCR and semi-quantitative immunocytochemical staining was used to measure the expression levels of cyclooxygenase-2, glutamate receptor-2, and platelet activating factor receptor. Our results found that cyclooxygenase-2 expression were firstly increased post-injury, and then decreased. Both mRNA and protein expression levels reached peaks at 8 and 12 hours post-injury, respectively. Similar sequential changes in glutamate receptor 2 were observed, with highest levels mRNA and protein expression at 8 and 12 hours post-injury respectively. On the contrary, the expressions of platelet activating factor receptor were firstly decreased post-injury, and then increased. Both mRNA and protein expression levels reached the lowest levels at 8 and 12 hours post-injury, respectively. Totally, our findings suggest that these three factors are involved in occurrence and development of hippocampal neuronal injury. PMID:25206921

  2. Pharmacological Blockade of Serotonin 5-HT7 Receptor Reverses Working Memory Deficits in Rats by Normalizing Cortical Glutamate Neurotransmission

    PubMed Central

    Bonaventure, Pascal; Aluisio, Leah; Shoblock, James; Boggs, Jamin D.; Fraser, Ian C.; Lord, Brian; Lovenberg, Timothy W.; Galici, Ruggero

    2011-01-01

    The role of 5-HT7 receptor has been demonstrated in various animal models of mood disorders; however its function in cognition remains largely speculative. This study evaluates the effects of SB-269970, a selective 5-HT7 antagonist, in a translational model of working memory deficit and investigates whether it modulates cortical glutamate and/or dopamine neurotransmission in rats. The effect of SB-269970 was evaluated in the delayed non-matching to position task alone or in combination with MK-801, a non-competitive NMDA receptor antagonist, and, in separate experiments, with scopolamine, a non-selective muscarinic antagonist. SB-269970 (10 mg/kg) significantly reversed the deficits induced by MK-801 (0.1 mg/kg) but augmented the deficit induced by scopolamine (0.06 mg/kg). The ability of SB-269970 to modulate MK-801-induced glutamate and dopamine extracellular levels was separately evaluated using biosensor technology and microdialysis in the prefrontal cortex of freely moving rats. SB-269970 normalized MK-801 -induced glutamate but not dopamine extracellular levels in the prefrontal cortex. Rat plasma and brain concentrations of MK-801 were not affected by co-administration of SB-269970, arguing for a pharmacodynamic rather than a pharmacokinetic mechanism. These results indicate that 5-HT7 receptor antagonists might reverse cognitive deficits associated with NMDA receptor hypofunction by selectively normalizing glutamatergic neurotransmission. PMID:21701689

  3. Symptomatic and neuroprotective effects following activation of nigral group III metabotropic glutamate receptors in rodent models of Parkinson's disease

    PubMed Central

    Austin, PJ; Betts, MJ; Broadstock, M; O'Neill, MJ; Mitchell, SN; Duty, S

    2010-01-01

    Background and purpose: Increased glutamatergic innervation of the substantia nigra pars reticulata (SNpr) and pars compacta (SNpc) may contribute to the motor deficits and neurodegeneration, respectively, in Parkinson's disease (PD). This study aimed to establish whether activation of pre-synaptic group III metabotropic glutamate (mGlu) receptors reduced glutamate release in the SN, and provided symptomatic or neuroprotective relief in animal models of PD. Experimental approach: Broad-spectrum group III mGlu receptor agonists, O-phospho-l-serine (l-SOP) and l-2-amino-4-phosphonobutyrate (l-AP4), were assessed for their ability to inhibit KCl-evoked [3H]-d-aspartate release in rat nigral prisms or inhibit KCl-evoked endogenous glutamate release in the SNpr in vivo using microdialysis. Reversal of akinesia in reserpine-treated rats was assessed following intranigral injection of l-SOP and l-AP4. Finally, the neuroprotective effect of 7 days' supra-nigral treatment with l-AP4 was examined in 6-hydroxydopamine (6-OHDA)-lesioned rats. Key results: l-SOP and l-AP4 inhibited [3H]-d-aspartate release by 33 and 44% respectively. These effects were blocked by the selective group III mGlu antagonist (RS)-α-cyclopropyl-4-phosphonophenylglycine (CPPG). l-SOP also reduced glutamate release in the SNpr in vivo by 48%. Injection of l-SOP and l-AP4 into the SNpr reversed reserpine-induced akinesia. Following administration above the SNpc, l-AP4 provided neurochemical, histological and functional protection against 6-OHDA lesion of the nigrostriatal tract. Pretreatment with CPPG inhibited these effects. Conclusions and implications: These findings highlight group III mGlu receptors in the SN as potential targets for providing both symptomatic and neuroprotective relief in PD, and indicate that inhibition of glutamate release in the SN may underlie these effects. PMID:20649576

  4. Neurophysiologic and antipsychotic profiles of TASP0433864, a novel positive allosteric modulator of metabotropic glutamate 2 receptor.

    PubMed

    Hiyoshi, Tetsuaki; Marumo, Toshiyuki; Hikichi, Hirohiko; Tomishima, Yasumitsu; Urabe, Hiroki; Tamita, Tomoko; Iida, Izumi; Yasuhara, Akito; Karasawa, Jun-ichi; Chaki, Shigeyuki

    2014-12-01

    Excess glutamatergic neurotransmission has been implicated in the pathophysiology of schizophrenia, and the activation of metabotropic glutamate 2 (mGlu2) receptor may exert antipsychotic effects by normalizing glutamate transmission. In the present study, we investigated the neurophysiologic and antipsychotic profiles of TASP0433864 [(2S)-2-[(4-tert-butylphenoxy)methyl]-5-methyl-2,3-dihydroimidazo[2,1-b][1,3]oxazole-6-carboxamide], a newly synthesized positive allosteric modulator (PAM) of mGlu2 receptor. TASP0433864 exhibited PAM activity at human and rat mGlu2 receptors with EC50 values of 199 and 206 nM, respectively, without exerting agonist activity at rat mGlu2 receptor. TASP0433864 produced a leftward and upward shift in the concentration-response curve of glutamate-increased guanosine 5'-O-(3-[(35)S]thio)triphosphate binding to mGlu2 receptor. In contrast, TASP0433864 had negligible activities for other mGlu receptors, including mGlu3 receptor, and did not have any affinity for other receptors or transporters. In hippocampal slices, TASP0433864 potentiated an inhibitory effect of DCG-IV [(2S,2'R,3'R)-2-(2',3'-dicarboxylcyclopropyl)glycine], a mGlu2/3 receptor agonist, on the field excitatory postsynaptic potentials in the dentate gyrus, indicating that TASP0433864 potentiates the mGlu2 receptor-mediated presynaptic inhibition of glutamate release. Moreover, TASP0433864 inhibited both MK-801 [(5S,10R)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate]- and ketamine-increased cortical γ band oscillation in the rat cortical electroencephalogram, which have been considered to reflect the excess activation of cortical pyramidal neurons. The inhibitory effect of TASP0433864 on cortical activation was also observed in the mouse 2-deoxy-glucose uptake study. In a behavioral study, TASP0433864 significantly inhibited both ketamine- and methamphetamine-increased locomotor activities in mice and rats, respectively. Collectively, these

  5. Changes in Synaptic Plasticity and Glutamate Receptors in Type 2 Diabetic KK-Ay Mice.

    PubMed

    Yin, Huajing; Wang, Weiping; Yu, Wenwen; Li, Jiang; Feng, Nan; Wang, Ling; Wang, Xiaoliang

    2017-03-18

    In the present study, the progressive alteration of cognition and the mechanisms of reduction in long-term potentiation (LTP) in spontaneous obese KK-Ay type 2 diabetic mice were investigated. In the study, 3-, 5-, and 7-month-old KK-Ay mice were used. The results indicated that KK-Ay mice showed cognitive deficits in the Morris water maze test beginning at the age of 3 months. LTP was significantly impaired in KK-Ay mice during whole study period (3 to 7 months). The above deficits were reversible at an early stage (3 to 5 months old) by diet intervention. Moreover, we found the underlying mechanisms of LTP impairment in KK-Ay mice might be attributed to abnormal phosphorylation or expression of postsynaptic glutamate receptor subunits instead of alteration of basal synaptic transmission. The expression levels of NR1, NR2A, and NR2B subunits of N-methyl-d-aspartate receptors were unchanged while the Tyr-dependent phosphorylation of both NR2A and NR2B subunits were significantly reduced in KK-Ay mice. The level of p-Src expression mediating this process was decreased, and the level of αCaMKII autophosphorylation was also reduced. Meanwhile, the GluR1 of α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors (AMPARs) was decreased, and GluR2 was significantly increased. These data suggest that deficits in synaptic plasticity in KK-Ay mice may arise from the abnormal phosphorylation of the NR2 subunits and the alteration of subunit composition of AMPARs. Diet intervention at an early stage of diabetes might alleviate the cognitive deficits and LTP reduction in KK-Ay mice.

  6. The metabotropic glutamate 5 receptor is necessary for extinction of cocaine‐associated cues

    PubMed Central

    Perry, Christina J; Reed, Felicia; Zbukvic, Isabel C; Kim, Jee Hyun

    2016-01-01

    Background and Purpose There is currently no medication approved specifically to treat cocaine addiction. Behavioural interventions such as cue exposure therapy (CET) rely heavily on new learning. Antagonism of the metabotropic glutamate 5 (mGlu5) receptor has emerged as a potential treatment, by reducing the reinforcing properties of cocaine. However, mGlu5 receptor activity is necessary for learning; therefore, such agents could interfere with behavioural treatments. We used a novel rodent model of CET to test the effects of mGlu5 negative and positive allosteric modulators (NAM and PAM) on behavioural therapy. Experimental Approach Rats were trained to press a lever for cocaine in the presence of a discrete cue [conditioned stimulus (CS)] and then extinguished in the absence of the CS. Following lever extinction, half the rats received CS extinction in the same chambers but with the levers withdrawn; the remaining rats received no CS extinction. Before this session, rats received a systemic administration of either vehicle or a mGlu5 NAM (MTEP, experiment 1) or PAM (CDPPB, experiment 2). Cue‐induced reinstatement was tested in a drug‐free session the following day. Key Results At reinstatement, rats that had received CS extinction showed reduced responding. This effect was attenuated by MTEP treatment before CS extinction. In contrast, administration of CDPPB (PAM) led to decreased reinstatement the following day, regardless of extinction condition. Conclusion and Implications These results suggest that mGlu5 receptor activity is both necessary and sufficient for efficient extinction of a cocaine‐associated CS. Therefore, mGlu5 PAMs could enhance the efficacy of CET. PMID:26784278

  7. Autosomal-Recessive Congenital Cerebellar Ataxia Is Caused by Mutations in Metabotropic Glutamate Receptor 1

    PubMed Central

    Guergueltcheva, Velina; Azmanov, Dimitar N.; Angelicheva, Dora; Smith, Katherine R.; Chamova, Teodora; Florez, Laura; Bynevelt, Michael; Nguyen, Thai; Cherninkova, Sylvia; Bojinova, Veneta; Kaprelyan, Ara; Angelova, Lyudmila; Morar, Bharti; Chandler, David; Kaneva, Radka; Bahlo, Melanie; Tournev, Ivailo; Kalaydjieva, Luba

    2012-01-01

    Autosomal-recessive congenital cerebellar ataxia was identified in Roma patients originating from a small subisolate with a known strong founder effect. Patients presented with global developmental delay, moderate to severe stance and gait ataxia, dysarthria, mild dysdiadochokinesia, dysmetria and tremors, intellectual deficit, and mild pyramidal signs. Brain imaging revealed progressive generalized cerebellar atrophy, and inferior vermian hypoplasia and/or a constitutionally small brain were observed in some patients. Exome sequencing, used for linkage analysis on extracted SNP genotypes and for mutation detection, identified two novel (i.e., not found in any database) variants located 7 bp apart within a unique 6q24 linkage region. Both mutations cosegregated with the disease in five affected families, in which all ten patients were homozygous. The mutated gene, GRM1, encodes metabotropic glutamate receptor mGluR1, which is highly expressed in cerebellar Purkinje cells and plays an important role in cerebellar development and synaptic plasticity. The two mutations affect a gene region critical for alternative splicing and the generation of receptor isoforms; they are a 3 bp exon 8 deletion and an intron 8 splicing mutation (c.2652_2654del and c.2660+2T>G, respectively [RefSeq accession number NM_000838.3]). The functional impact of the deletion is unclear and is overshadowed by the splicing defect. Although ataxia lymphoblastoid cell lines expressed GRM1 at levels comparable to those of control cells, the aberrant transcripts skipped exon 8 or ended in intron 8 and encoded various species of nonfunctional receptors either lacking the transmembrane domain and containing abnormal intracellular tails or completely missing the tail. The study implicates mGluR1 in human hereditary ataxia. It also illustrates the potential of the Roma founder populations for mutation identification by exome sequencing. PMID:22901947

  8. Molecular dynamics simulations of the ligand-binding domain of the ionotropic glutamate receptor GluR2.

    PubMed Central

    Arinaminpathy, Yalini; Sansom, Mark S P; Biggin, Philip C

    2002-01-01

    Ionotropic glutamate receptors are essential for fast synaptic nerve transmission. Recent x-ray structures for the ligand-binding (S1S2) region of the GluR2 alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)-sensitive receptor have suggested how differences in protein/ligand interactions may determine whether a ligand will behave as a full agonist. We have used multiple molecular dynamics simulations of 2-5 ns duration to explore the structural dynamics of GluR2 S1S2 in the presence and absence of glutamate and in a complex with kainate. Our studies indicate that not only is the degree of domain closure dependent upon interactions with the ligand, but also that protein/ligand interactions influence the motion of the S2 domain with respect to S1. Differences in domain mobility between the three states (apo-S1S2, glutamate-bound, and kainate-bound) are surprisingly clear-cut. We discuss how these changes in dynamics may provide an explanation relating the mechanism of transmission of the agonist-binding event to channel opening. We also show here how the glutamate may adopt an alternative mode of binding not seen in the x-ray structure, which involves a key threonine (T480) side chain flipping into a new conformation. This new conformation results in an altered pattern of hydrogen bonding at the agonist-binding site. PMID:11806910

  9. Developmental regulation of N-methyl-D-aspartate- and kainate-type glutamate receptor expression in the rat spinal cord

    NASA Technical Reports Server (NTRS)

    Stegenga, S. L.; Kalb, R. G.

    2001-01-01

    Spinal motor neurons undergo experience-dependent development during a critical period in early postnatal life. It has been suggested that the repertoire of glutamate receptor subunits differs between young and mature motor neurons and contributes to this activity-dependent development. In the present study we examined the expression patterns of N-methyl-D-aspartate- and kainate-type glutamate receptor subunits during the postnatal maturation of the spinal cord. Young motor neurons express much higher levels of the N-methyl-D-aspartate receptor subunit NR1 than do adult motor neurons. Although there are eight potential splice variants of NR1, only a subgroup is expressed by motor neurons. With respect to NR2 receptor subunits, young motor neurons express NR2A and C, while adult motor neurons express only NR2A. Young motor neurons express kainate receptor subunits GluR5, 6 and KA2 but we are unable to detect these or any other kainate receptor subunits in the adult spinal cord. Other spinal cord regions display a distinct pattern of developmental regulation of N-methyl-D-aspartate and kainate receptor subunit expression in comparison to motor neurons. Our findings indicate a precise spatio-temporal regulation of individual subunit expression in the developing spinal cord. Specific combinations of subunits in developing neurons influence their excitable properties and could participate in the emergence of adult neuronal form and function.

  10. Distribution of vesicular glutamate transporter 2 and glutamate receptor 1 mRNA in the central nervous system of the pigeon (Columba livia).

    PubMed

    Islam, Mohammad Rafiqul; Atoji, Yasuro

    2008-12-10

    Glutamate acts as the excitatory neurotransmitter in the central nervous system (CNS) and is mediated largely by the vesicular glutamate transporters (VGLUT1-3) and alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) types of glutamate receptors (GluR1-4) in mammals. In the present study, we determined the cDNA sequences of pigeon VGLUT2 and GluR1 and mapped the distribution of their mRNA in the pigeon CNS. The predicted amino acids of pigeon VGLUT2 and GluR1 showed a 93% identity to human VGLUT2 and GluR1 both. In situ hybridization autoradiograms showed VGLUT2 mRNA expression exclusively in the pallium of the telencephalon, and no expression in the subpallium. Within the diencephalon, VGLUT2 mRNA was more abundant in the thalamus than in the hypothalamus. Rich VGLUT2 mRNA expression was found in the optic tectum, nucleus mesencephalicus lateralis, pars dorsalis, nucleus isthmi, pars parvocellularis, isthmo-optic nucleus, pontine nuclei, and granular layer of the cerebellum. Moderate expression was noted in the cerebellar nuclei, vestibular nuclei, cochlear nuclei, inferior olivary nucleus, and gray matter of the spinal cord. GluR1 mRNA was expressed abundantly in the pallium and subpallium of the telencephalon, but it was poor in the diencephalon, midbrain, medulla, cerebellar cortex, and gray matter of the spinal cord. These results suggest that the cDNA sequences of VGLUT2 and GluR1 in the pigeon are comparable to those of VGLUT2 and GluR1 in mammals, respectively. The distribution of pigeon GluR1 mRNA resembles that of mammals, but the distribution of VGLUT2 mRNA resembles that of both VGLUT1 and VGLUT2 in mammals.

  11. Cannabinoid-glutamate interactions in the regulation of food intake in neonatal layer- type chicks: role of glutamate NMDA and AMPA receptors.

    PubMed

    Keyshams, Negar; Zendehdel, Morteza; Babapour, Vahab; Baghbanzadeh, Ali

    2016-06-01

    The involvement of the endocannabinoid system in the brain functions is likely the conclusion of its capability to interact with specific neurotransmitters in several brain regions. The present study was designed to examine the role of the glutamatergic system on cannabinoid-induced hyperphagia in chicken. In this survey 10 experiments designed to investigate interaction of cannabinoidergic and glutamatergic systems on feeding behavior in neonatal chickens. In experiment 1, chicken were intracerebroventricular (ICV) injected with saline, 2-AG (2-Arachidonoylglycerol, 5.28 nmol, CB1 receptors agonist), MK-801(NMDA receptor antagonist, 15 nmol) and co-administration of 2-AG + MK-801. In experiment 2, injection of saline, 2-AG (5.28 nmol), CNQX) AMPA/kainate receptor antagonist, 390 nmol) and their combination (2-AG + CNQX) was done. In Experiment 3, injections were saline, 2-AG (5.28 nmol), AIDA)mGluR1 antagonist, 2 nmol) and 2-AG + AIDA. Experiments 4 and 5 were similar to experiment 3, except birds injected with LY341495 (mGLUR2 glutamate antagonist, 150 nmol) and UBP1112 (mGLUR3 glutamate antagonist, 2 nmol) instead of AIDA. Experiments 6-10 followed the procedure similar to experiments 1-5, except chickens received ICV injection of CB65 (CB2 receptor agonist, 3 nmol), instead of 2-AG. Then the cumulative food intake measured until 120 min post injection. According to the results, ICV injection of 2-AG and CB65 significantly increased food intake (P < 0.001). Co-injection of 2-AG and MK-801 significantly amplified hyperphagic effect of CB1 receptors agonist(P < 0.001). Moreover, co-administration of CB65 plus CNQX significantly increased CB65- induced hyperphagia in FD3 neonatal layer-type chickens (P < 0.001). These results suggest there is an interaction between endocannabinoids and glutamatergic systems via NMDA and AMPA receptors in feeding behavior of neonatal layer-type chickens.

  12. Effects of lead exposure on hippocampal metabotropic glutamate receptor subtype 3 and 7 in developmental rats

    PubMed Central

    Xu, Jian; Yan, Huai C; Yang, Bo; Tong, Lu S; Zou, Yu X; Tian, Ying

    2009-01-01

    Background A complete explanation of the mechanisms by which Pb2+ exerts toxic effects on developmental central nervous system remains unknown. Glutamate is critical to the developing brain through various subtypes of ionotropic or metabotropic glutamate receptors (mGluRs). Ionotropic N-methyl-D-aspartate receptors have been considered as a principal target in lead-induced neurotoxicity. The relationship between mGluR3/mGluR7 and synaptic plasticity had been verified by many recent studies. The present study aimed to examine the role of mGluR3/mGluR7 in lead-induced neurotoxicity. Methods Twenty-four adult and female rats were randomly selected and placed on control or 0.2% lead acetate during gestation and lactation. Blood lead and hippocampal lead levels of pups were analyzed at weaning to evaluate the actual lead content at the end of the exposure. Impairments of short -term memory and long-term memory of pups were assessed by tests using Morris water maze and by detection of hippocampal ultrastructural alterations on electron microscopy. The impact of lead exposure on mGluR3 and mGluR7 mRNA expression in hippocampal tissue of pups were investigated by quantitative real-time polymerase chain reaction and its potential role in lead neurotoxicity were discussed. Results Lead levels of blood and hippocampi in the lead-exposed rats were significantly higher than those in the controls (P < 0.001). In tests using Morris Water Maze, the overall decrease in goal latency and swimming distance was taken to indicate that controls had shorter latencies and distance than lead-exposed rats (P = 0.001 and P < 0.001 by repeated-measures analysis of variance). On transmission electron microscopy neuronal ultrastructural alterations were observed and the results of real-time polymerase chain reaction showed that exposure to 0.2% lead acetate did not substantially change gene expression of mGluR3 and mGluR7 mRNA compared with controls. Conclusion Exposure to lead before and after

  13. Excitatory Mechanisms in the Suprachiasmatic Nucleus: The Role of AMPA/KA Glutamate Receptors

    PubMed Central

    Michel, Stephan; Itri, Jason; Colwell, Christopher S.

    2008-01-01

    A variety of evidence suggests that the effects of light on the mammalian circadian system are mediated by direct retinal ganglion cell projection to the suprachiasmatic nucleus (SCN). This synaptic connection is glutamatergic and the release of glutamate is detected by both N-methyl-d-asparate (NMDA) and amino-methyl proprionic acid/kainate (AMPA/KA) iontotropic glutamate receptors (GluRs). It is well established that NMDA GluRs play a critical role in mediating the effects of light on the circadian system; however, the role of AMPA/KA GluRs has received less attention. In the present study, we sought to better understand the contribution of AMPA/KA-mediated currents in the circadian system based in the SCN. First, whole cell patch-clamp electrophysiological techniques were utilized to measure spontaneous excitatory postsynaptic currents (sEPSCs) from SCN neurons. These currents were widespread in the SCN and not just restricted to the retino-recipient region. The sEPSC frequency and amplitude did not vary with the daily cycle. Similarly, currents evoked by the exogenous application of AMPA onto SCN neurons were widespread within the SCN and did not exhibit a diurnal rhythm in their magnitude. Fluorometric techniques were utilized to estimate AMPA-induced calcium (Ca2+) concentration changes in SCN neurons. The resulting data indicate that AMPA-evoked Ca2+ transients were widespread in the SCN and that there was a daily rhythm in the magnitude of AMPA-induced Ca2+ transients that peaked during the night. By itself, blocking AMPA/KA GluRs with a receptor blocker decreased the spontaneous firing of some SCN neurons as well as reduced resting Ca2+ levels, suggesting tonic glutamatergic excitation. Finally, immunohistochemical techniques were used to describe expression of the AMPA-preferring GluR subunits GluR1 and GluR2/3s within the SCN. Overall, our data suggest that glutamatergic synaptic transmission mediated by AMPA/KA GluRs play an important role throughout

  14. Undifferentiated embryonic stem cells express ionotropic glutamate receptor mRNAs

    PubMed Central

    Pachernegg, Svenja; Joshi, Illah; Muth-Köhne, Elke; Pahl, Steffen; Münster, Yvonne; Terhag, Jan; Karus, Michael; Werner, Markus; Ma-Högemeier, Zhan-Lu; Körber, Christoph; Grunwald, Thomas; Faissner, Andreas; Wiese, Stefan; Hollmann, Michael

    2013-01-01

    Ionotropic glutamate receptors (iGluRs) do not only mediate the majority of excitatory neurotransmission in the vertebrate CNS, but also modulate pre- and postnatal neurogenesis. Most of the studies on the developmental role of iGluRs are performed on neural progenitors and neural stem cells (NSCs). We took a step back in our study by examining the role of iGluRs in the earliest possible cell type, embryonic stem cells (ESCs), by looking at the mRNA expression of the major iGluR subfamilies in undifferentiated mouse ESCs. For that, we used two distinct murine ES cell lines, 46C ESCs and J1 ESCs. Regarding 46C ESCs, we found transcripts of kainate receptors (KARs) (GluK2 to GluK5), AMPA receptors (AMPARs) (GluA1, GluA3, and GluA4), and NMDA receptors (NMDARs) (GluN1, and GluN2A to GluN2D). Analysis of 46C-derived cells of later developmental stages, namely neuroepithelial precursor cells (NEPs) and NSCs, revealed that the mRNA expression of KARs is significantly upregulated in NEPs and, subsequently, downregulated in NSCs. However, we could not detect any protein expression of any of the KAR subunits present on the mRNA level either in ESCs, NEPs, or NSCs. Regarding AMPARs and NMDARs, GluN2A is weakly expressed at the protein level only in NSCs. Matching our findings for iGluRs, all three cell types were found to weakly express pre- and postsynaptic markers of glutamatergic synapses only at the mRNA level. Finally, we performed patch-clamp recordings of 46C ESCs and could not detect any current upon iGluR agonist application. Similar to 46C ESCs, J1 ESCs express KARs (GluK2 to GluK5), AMPARs (GluA3), and NMDARs (GluN1, and GluN2A to GluN2D) at the mRNA level, but these transcripts are not translated into receptor proteins either. Thus, we conclude that ESCs do not contain functional iGluRs, although they do express an almost complete set of iGluR subunit mRNAs. PMID:24348335

  15. Morphine and DAMGO produce an opposite effect on presynaptic glutamate release via different downstream pathways of μ opioid receptors in the basolateral amygdala.

    PubMed

    Yang, Jinhui; Yang, Hualan; Du, Xiaowei; Ma, Qianqian; Song, Jiaojiao; Chen, Ming; Dong, Yi; Ma, Lan; Zheng, Ping

    2014-11-01

    Increasing evidence demonstrates that different opioids, while acting μ opioid receptors, can activate distinct downstream responses, a phenomenon termed functional selectivity or biased agonism. The present study designed experiments to test whether the μ receptor agonist morphine and D-Ala(2), N-Me-Phe(4), Gly(5)-ol-enkephalin (DAMGO) had a different effect on presynaptic glutamate release in the basolateral amygdala (BLA) and whether this difference was due to their biased agonism at μ receptors. The results showed that DAMGO markedly decreased the frequency of sEPSCs in pyramidal cells of BLA. The concentration-dependence experiment showed that DAMGO dose-dependently decreased the frequency of sEPSCs. Morphine markedly increased the frequency of sEPSCs in pyramidal cells of BLA. The concentration-dependence experiment showed that morphine dose-dependently increased the frequency of sEPSCs. We also used PPF of EPSC as another indicator of presynaptic glutamate release to confirm the opposite effect of morphine and DAMGO on the glutamate release. Further mechanism studies showed that the opposite effect of morphine and DAMGO on the glutamate release was via the activation of μ receptors, but the downstream signaling pathways of μ receptors were different: DAMGO inhibited the glutamate release via μ receptor-Gi protein- PLA2-AA signaling pathway, whereas morphine promoted the glutamate release via μ receptor-Gi protein-PKC-ERK1/2-synapsin I signaling pathway.

  16. Chromosomal localization of glutamate receptor genes: relationship to familial amyotrophic lateral sclerosis and other neurological disorders of mice and humans.

    PubMed Central

    Gregor, P; Reeves, R H; Jabs, E W; Yang, X; Dackowski, W; Rochelle, J M; Brown, R H; Haines, J L; O'Hara, B F; Uhl, G R

    1993-01-01

    Receptors for the major excitatory neurotransmitter glutamate may play key roles in neurodegeneration. The mouse Glur-5 gene maps to chromosome 16 between App and Sod-1. The homologous human GLUR5 gene maps to the corresponding region of human chromosome 21, which contains the locus for familial amyotrophic lateral sclerosis. This location, and other features, render GLUR5 a possible candidate gene for familial amyotrophic lateral sclerosis. In addition, dosage imbalance of GLUR5 may have a role in the trisomy 21 (Down syndrome). Further characterization of the murine glutamate receptor family includes mapping of Glur-1 to the same region as neurological mutants spasmodic, shaker-2, tipsy, and vibrator on chromosome 11; Glur-2 near spastic on chromosome 3; Glur-6 near waltzer and Jackson circler on chromosome 10; and Glur-7 near clasper on chromosome 4. Images Fig. 3 PMID:8464923

  17. Stimulation of glutamate receptors in the ventral tegmental area is necessary for serotonin-2 receptor-induced increases in mesocortical dopamine release

    PubMed Central

    Pehek, E.A.; Hernan, A.E.

    2017-01-01

    Modulation of dopamine (DA) released by serotonin-2 (5-HT2) receptors has been implicated in the mechanism of action of antipsychotic drugs. The mesocortical DA system has been implicated particularly in the cognitive deficits observed in schizophrenia. Agonism at 5-HT2A receptors in the prefrontal cortex is associated with increases in cortical DA release. Evidence indicates that 5-HT2A receptors in the cortex regulate mesocortical DA release through stimulation of a “long-loop” feedback system from the PFC to the VTA and back. However, a causal role for VTA glutamate in the 5-HT2-induced increases in PFC DA has not been established. The present study does so by measuring 5-HT2 agonist-induced DA release in the cortex after infusions of glutamate antagonists into the VTA. Infusions of a combination of a NMDA (AP-5: 2-amino-5-phosphopentanoic acid) and an AMPA/kainate (CNQX: 6-cyano-7-nitroquinoxaline-2,3-dione) receptor antagonist into the VTA blocked the increases in cortical DA produced by administration of the 5-HT2 agonist DOI [(±)-2,5-Dimethoxy-4-iodoamphetamine] (2.5 mg/kg s.c.). These results demonstrate that stimulation of glutamate receptors in the VTA is necessary for 5-HT2 agonist-induced increases in cortical DA. PMID:25637799

  18. Relationship between Zinc (Zn2+) and Glutamate Receptors in the Processes Underlying Neurodegeneration

    PubMed Central

    Pochwat, Bartłomiej; Nowak, Gabriel; Szewczyk, Bernadeta

    2015-01-01

    The results from numerous studies have shown that an imbalance between particular neurotransmitters may lead to brain circuit dysfunction and development of many pathological states. The significance of glutamate pathways for the functioning of the nervous system is equivocal. On the one hand, glutamate transmission is necessary for neuroplasticity, synaptogenesis, or cell survival, but on the other hand an excessive and long-lasting increased level of glutamate in the synapse may lead to cell death. Under clinical conditions, hyperactivity of the glutamate system is associated with ischemia, epilepsy, and neurodegenerative diseases such as Alzheimer's, Huntington's, and many others. The achievement of glutamate activity in the physiological range requires efficient control by endogenous regulatory factors. Due to the fact that the free pool of ion Zn2+ is a cotransmitter in some glutamate neurons; the role of this element in the pathophysiology of a neurodegenerative diseases has been intensively studied. There is a lot of evidence for Zn2+ dyshomeostasis and glutamate system abnormalities in ischemic and neurodegenerative disorders. However, the precise interaction between Zn2+ regulative function and the glutamate system is still not fully understood. This review describes the relationship between Zn2+ and glutamate dependent signaling pathways under selected pathological central nervous system (CNS) conditions. PMID:26106488

  19. Localization of a gene for a glutamate binding subunit of a NMDA receptor (GRINA) to 8q24

    SciTech Connect

    Lewis, T.B.; DuPont, B.R.; Leach, R.

    1996-02-15

    This article reports on the localization of a gene for a glutamate binding subunit of an N-methyl-D-aspartate (NMDA) receptor, called GRINA, to human chromosome 8q24 using fluorescence in situ hybridization and radiation hybridization mapping. This gene mapped outside the critical region for benign familial neonatal convulsions (BFNC), a rare form of epilepsy; however, GRINA could be the causative genetic factor inducing idiopathic generalized epilepsy. Further studies need to be conducted. 15 refs., 2 figs.

  20. Cloning and characterization of glutamate receptors in Californian sea lions (Zalophus californianus).

    PubMed

    Gill, Santokh; Goldstein, Tracey; Situ, Donna; Zabka, Tanja S; Gulland, Frances M D; Mueller, Rudi W

    2010-05-06

    Domoic acid produced by marine algae has been shown to cause acute and chronic neurologic sequelae in Californian sea lions following acute or low-dose exposure. Histological findings in affected animals included a degenerative cardiomyopathy that was hypothesized to be caused by over-excitation of the glutamate receptors (GluRs) speculated to be present in the sea lion heart. Thus tissues from five sea lions without lesions associated with domoic acid toxicity and one animal with domoic acid-induced chronic neurologic sequelae and degenerative cardiomyopathy were examined for the presence of GluRs. Immunohistochemistry localized mGluR 2/3, mGluR 5, GluR 2/3 and NMDAR 1 in structures of the conducting system and blood vessels. NMDAR 1 and GluR 2/3 were the most widespread as immunoreactivity was observed within sea lion conducting system structures. PCR analysis, cloning and subsequent sequencing of the seal lion GluRs showed only 80% homology to those from rats, but more than 95% homologous to those from dogs. The cellular distribution and expression of subtypes of GluRs in the sea lion hearts suggests that exposure to domoic acid may induce cardiac damage and functional disturbances.

  1. Differential regulation of synaptic inputs to dentate hilar border interneurons by metabotropic glutamate receptors.

    PubMed

    Doherty, J; Dingledine, R

    1998-06-01

    Regulation of synaptic transmission by metabotropic glutamate receptors (mGluRs) was examined at two excitatory inputs to interneurons with cell bodies at the granule cell-hilus border in hippocampal slices taken from neonatal rats. Subgroup-selective mGluR agonists altered the reliability, or probability of transmitter release, of evoked minimal excitatory synaptic inputs and decreased the amplitudes of excitatory postsynaptic currents (EPSCs) evoked with conventional stimulation. The group II-selective agonist, (2S,1R',2R',3R')-2-(2, 3-dicarboxylcyclopropyl) glycine (DCG-IV; 1 microM), reversibly depressed the reliability of EPSCs evoked by stimulation of the dentate granule cell layer. However, DCG-IV had no significant effect on EPSCs evoked by CA3 stimulation in the majority (82%) of hilar border interneurons. Both the group III-selective agonist, -(+)-2-amino-4-phosphonobutyric acid (-AP4; 3 microM), and the group I-selective agonist, (RS)-3,5-dihydroxyphenylglycine (DHPG; 20 microM) reversibly depressed synaptic input to interneurons from both CA3 and the granule cell layer. We conclude that multiple pharmacologically distinct mGluRs presynaptically regulate synaptic transmission at two excitatory inputs to hilar border interneurons. Further, the degree of mGluR-meditated depression of excitatory drive is greater at synapses from dentate granule cells onto interneurons than at synapses from CA3 pyramidal cells.

  2. Metabotropic Glutamate Receptors 7 within the Nucleus Accumbens are Involved in Relief Learning in Rats

    PubMed Central

    Kahl, Evelyn; Fendt, Markus

    2016-01-01

    Relief learning is an appetitive association of a formally neutral cue with relief induced by the offset of an aversive stimulus. Since the nucleus accumbens mediates relief learning and accumbal metabotropic glutamate receptors 7 (mGluR7) modulate appetitive-like processes, we hypothesized that accumbal mGluR7 may be involved in the modulation of relief learning. Therefore, we injected the allosteric mGluR7 agonist AMN082 into the nucleus accumbens and tested the effects of these injections on acquisition and expression of relief memory, as well as on the reactivity to electric stimuli. AMN082 injections blocked acquisition but not expression of relief memory. In addition, accumbal AMN082 injections strongly reduced the locomotor reactivity to electric stimuli indicating antinociceptive effects. These antinociceptive effects might be causal for the blockade of relief learning after AMN082 injections. Taken together, the present study indicates that functional activation of accumbal mGluR7 has antinociceptive effects that interfere with relief learning. PMID:27296637

  3. Orphan Glutamate Receptor δ1 Subunit Required for High-Frequency Hearing▿

    PubMed Central

    Gao, Jiangang; Maison, Stéphane F.; Wu, Xudong; Hirose, Keiko; Jones, Sherri M.; Bayazitov, Ildar; Tian, Yong; Mittleman, Guy; Matthews, Douglas B.; Zakharenko, Stanislav S.; Liberman, M. Charles; Zuo, Jian

    2007-01-01

    The function of the orphan glutamate receptor delta subunits (GluRδ1 and GluRδ2) remains unclear. GluRδ2 is expressed exclusively in the Purkinje cells of the cerebellum, and GluRδ1 is prominently expressed in inner ear hair cells and neurons of the hippocampus. We found that mice lacking the GluRδ1 protein displayed significant cochlear threshold shifts for frequencies of >16 kHz. These deficits correlated with a substantial loss of type IV spiral ligament fibrocytes and a significant reduction of endolymphatic potential in high-frequency cochlear regions. Vulnerability to acoustic injury was significantly enhanced; however, the efferent innervation of hair cells and the classic efferent inhibition of outer hair cells were unaffected. Hippocampal and vestibular morphology and function were normal. Our findings show that the orphan GluRδ1 plays an essential role in high-frequency hearing and ionic homeostasis in the basal cochlea, and the locus encoding GluRδ1 represents a candidate gene for congenital or acquired high-frequency hearing loss in humans. PMID:17438141

  4. Metabotropic glutamate subtype 5 receptors modulate fear-conditioning induced enhancement of prepulse inhibition in rats.

    PubMed

    Zou, Dan; Huang, Juan; Wu, Xihong; Li, Liang

    2007-02-01

    Non-startling acoustic events presented shortly before an intense startling sound can inhibit the acoustic startle reflex. This phenomenon is called prepulse inhibition (PPI), and is widely used as a model of sensorimotor gating. The present study investigated whether PPI can be modulated by fear conditioning, whose acquisition can be blocked by the specific antagonist of metabotropic glutamate receptors subtype 5 (mGluR5), 2-methyl-6-(phenylethynyl)-pyridine (MPEP). The results show that a gap embedded in otherwise continuous noise sounds, which were delivered by two spatially separated loudspeakers, could inhibit the startle reflex induced by an intense sound that was presented 50 ms after the gap. The inhibitory effect depended on the duration of the gap, and was enhanced by fear conditioning that was introduced by temporally pairing the gap with footshock. Intraperitoneal injection of MPEP (0.5 or 5mg/kg) 30 min before fear conditioning blocked the enhancing effect of fear conditioning on PPI, but did not affect either the baseline startle magnitude or PPI if no fear conditioning was introduced. These results indicate that PPI is enhanced when the prepulse signifies an aversive event after fear conditioning. Also, mGlu5Rs play a role in preserving the fear-conditioning-induced enhancement of PPI.

  5. Metabotropic glutamate receptor type 5 in levodopa-induced motor complications.

    PubMed

    Ouattara, Bazoumana; Grégoire, Laurent; Morissette, Marc; Gasparini, Fabrizio; Vranesic, Ivo; Bilbe, Graeme; Johns, Donald R; Rajput, Alex; Hornykiewicz, Oleh; Rajput, Ali H; Gomez-Mancilla, Baltazar; Di Paolo, Thérèse

    2011-07-01

    Metabotropic glutamate receptors type 5 (mGluR5) are implicated in regulation of synaptic plasticity and learning, and were the focus of our investigation in human Parkinson's disease (PD) patients with dyskinesias and wearing-off, and in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) monkeys with dyskinesias. Using the selective mGluR5 ligand [(3)H]ABP688 autoradiography, we measured mGluR5 in brain slices from 11 normal and 14 PD patients and from MPTP monkeys, in relation to motor complications (dyskinesias and wearing-off) associated with treatment with l-dopa. In 16 monkeys with a bilateral MPTP lesion and four controls, [(3)H]ABP688 specific binding was elevated in the striatum of dyskinetic l-dopa-treated MPTP monkeys but not in MPTP monkeys without dyskinesias compared to controls. PD patients with motor complications (either dyskinesias or wearing-off) had higher [(3)H]ABP688 specific binding compared to those without motor complications and controls in putamen, external and internal globus pallidus. Elevated glutamatergic transmission as measured with increased mGluR5 specific binding was associated with motor complications and its antagonism could be targeted for their treatment.

  6. Dbo/Henji Modulates Synaptic dPAK to Gate Glutamate Receptor Abundance and Postsynaptic Response

    PubMed Central

    Wang, Manyu; Chen, Pei-Yi; Wang, Chien-Hsiang; Lai, Tzu-Ting; Tsai, Pei-I; Cheng, Ying-Ju; Kao, Hsiu-Hua; Chien, Cheng-Ting

    2016-01-01

    In response to environmental and physiological changes, the synapse manifests plasticity while simultaneously maintains homeostasis. Here, we analyzed mutant synapses of henji, also known as dbo, at the Drosophila neuromuscular junction (NMJ). In henji mutants, NMJ growth is defective with appearance of satellite boutons. Transmission electron microscopy analysis indicates that the synaptic membrane region is expanded. The postsynaptic density (PSD) houses glutamate receptors GluRIIA and GluRIIB, which have distinct transmission properties. In henji mutants, GluRIIA abundance is upregulated but that of GluRIIB is not. Electrophysiological results also support a GluR compositional shift towards a higher IIA/IIB ratio at henji NMJs. Strikingly, dPAK, a positive regulator for GluRIIA synaptic localization, accumulates at the henji PSD. Reducing the dpak gene dosage suppresses satellite boutons and GluRIIA accumulation at henji NMJs. In addition, dPAK associated with Henji through the Kelch repeats which is the domain essential for Henji localization and function at postsynapses. We propose that Henji acts at postsynapses to restrict both presynaptic bouton growth and postsynaptic GluRIIA abundance by modulating dPAK. PMID:27736876

  7. Mitochondria and NMDA Receptor-Dependent Toxicity of Berberine Sensitizes Neurons to Glutamate and Rotenone Injury

    PubMed Central

    Kysenius, Kai; Brunello, Cecilia A.; Huttunen, Henri J.

    2014-01-01

    The global incidence of metabolic and age-related diseases, including type 2 diabetes and Alzheimer's disease, is on the rise. In addition to traditional pharmacotherapy, drug candidates from complementary and alternative medicine are actively being pursued for further drug development. Berberine, a nutraceutical traditionally used as an antibiotic, has recently been proposed to act as a multi-target protective agent against type 2 diabetes, dyslipidemias, ischemic brain injury and neurodegenerative diseases, such as Parkinson's and Alzheimer's disease. However, the safety profile of berberine remains controversial, as isolated reports suggest risks with acute toxicity, bradycardia and exacerbation of neurodegeneration. We report that low micromolar berberine causes rapid mitochondria-dependent toxicity in primary neurons characterized by mitochondrial swelling, increased oxidative stress, decreased mitochondrial membrane potential and depletion of ATP content. Berberine does not induce caspase-3 activation and the resulting neurotoxicity remains unaffected by pan-caspase inhibitor treatment. Interestingly, inhibition of NMDA receptors by memantine and MK-801 completely blocked berberine-induced neurotoxicity. Additionally, subtoxic nanomolar concentrations of berberine were sufficient to sensitize neurons to glutamate excitotoxicity and rotenone injury. Our study highlights the need for further safety assessment of berberine, especially due to its tendency to accumulate in the CNS and the risk of potential neurotoxicity as a consequence of increasing bioavailability of berberine. PMID:25192195

  8. Glutamate Receptor Interacting Protein 1 Mediates Platelet Adhesion and Thrombus Formation

    PubMed Central

    Modjeski, Kristina L.; Ture, Sara K.; Field, David J.; Cameron, Scott J.; Morrell, Craig N.

    2016-01-01

    Thrombosis-associated pathologies, such as myocardial infarction and stroke, are major causes of morbidity and mortality worldwide. Because platelets are necessary for hemostasis and thrombosis, platelet directed therapies must balance inhibiting platelet function with bleeding risk. Glutamate receptor interacting protein 1 (GRIP1) is a large scaffolding protein that localizes and organizes interacting proteins in other cells, such as neurons. We have investigated the role of GRIP1 in platelet function to determine its role as a molecular scaffold in thrombus formation. Platelet-specific GRIP1-/- mice were used to determine the role of GRIP1 in platelets. GRIP1-/- mice had normal platelet counts, but a prolonged bleeding time and delayed thrombus formation in a FeCl3-induced vessel injury model. In vitro stimulation of WT and GRIP1-/- platelets with multiple agonists showed no difference in platelet activation. However, in vivo platelet rolling velocity after endothelial stimulation was significantly greater in GRIP1-/- platelets compared to WT platelets, indicating a potential platelet adhesion defect. Mass spectrometry analysis of GRIP1 platelet immunoprecipitation revealed enrichment of GRIP1 binding to GPIb-IX complex proteins. Western blots confirmed the mass spectrometry findings that GRIP1 interacts with GPIbα, GPIbβ, and 14-3-3. Additionally, in resting GRIP1-/- platelets, GPIbα and 14-3-3 have increased interaction compared to WT platelets. GRIP1 interactions with the GPIb-IX binding complex are necessary for normal platelet adhesion to a stimulated endothelium. PMID:27631377

  9. The influence of ionotropic and metabotropic glutamate receptor ligands on anxiety-like effect of amphetamine withdrawal in rats.

    PubMed

    Koltunowska, D; Gibula-Bruzda, E; Kotlinska, J H

    2013-08-01

    Chronic amphetamine use results in anxiety-like states after drug cessation. The aim of the study was to determine a role of ionotropic and metabotropic glutamate receptor ligands in amphetamine-evoked withdrawal anxiety in the elevated plus-maze test in rats. In our study memantine (8 and 12 mg/kg), a noncompetitive N-methyl-d-aspartate (NMDA) receptor antagonist did not reduce amphetamine withdrawal anxiety. Acamprosate (NMDA and metabotropic glutamate 5 receptor (mGluR5) antagonist) at the dose 200 and 400mg/kg showed anxiolytic-like effect, thus increasing the percent of time spent in open arms and a number of open arm entries. mGluR5 selective antagonist, MTEP (3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]pyridine hydrochloride) and mGluR2/3 agonist, LY354740 (1S,2S,5R,6S)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid), caused effects similar to acamprosate at doses 1.25-5mg/kg and 2.5-5mg/kg, respectively. None of the glutamate ligands influenced locomotor activity of rats when given to the saline-treated group. Taking into account the positive correlation between amphetamine withdrawal-induced anxiety and relapse to amphetamine taking, our results suggest that modulation of mGluRs may prevent relapse to amphetamine and might pose a new direction in amphetamine abuse therapy.

  10. Brain-derived neurotrophic factor and neurotrophin receptors modulate glutamate-induced phase shifts of the suprachiasmatic nucleus

    PubMed Central

    Michel, S.; Clark, J. P.; Ding, J. M.; Colwell, C. S.

    2008-01-01

    Light information reaches the suprachiasmatic nucleus (SCN) through a subpopulation of retinal ganglion cells. Previous work raised the possibility that brain-derived neurotrophic factor (BDNF) and its high-affinity tropomyosin-related receptor kinase may be important as modulators of this excitatory input into the SCN. In order to test this possibility, we used whole-cell patch-clamp methods to measure spontaneous excitatory currents in mouse SCN neurons. We found that the amplitude and frequency of these currents were increased by BDNF and decreased by the neurotrophin receptor inhibitor K252a. The neurotrophin also increased the magnitude of currents evoked by application of N-methyl-D-aspartate and amino-methyl proprionic acid. Next, we measured the rhythms in action potential discharge from the SCN brain slice preparation. We found that application of K252a dramatically reduced the magnitude of phase shifts of the electrical activity rhythm generated by the application of glutamate. By itself, BDNF caused phase shifts that resembled those produced by glutamate and were blocked by K252a. The results demonstrate that BDNF and neurotrophin receptors can enhance glutamatergic synaptic transmission within a subset of SCN neurons and potentiate glutamate-induced phase shifts of the circadian rhythm of neural activity in the SCN. PMID:16930436

  11. Ion permeation properties of the glutamate receptor channel in cultured embryonic Drosophila myotubes.

    PubMed Central

    Chang, H; Ciani, S; Kidokoro, Y

    1994-01-01

    Ion permeation properties of the glutamate receptor channel in cultured myotubes of Drosophila embryos were studied using the inside-out configuration of the patch-clamp technique. Lowering the NaCl concentration in the bath (intracellular solution), while maintaining that of the external solution constant, caused a shift of the reversal potential in the positive direction, thus indicating a higher permeability of the channel to Na+ than to Cl- (PCl/PNa < 0.04), and suggesting that the channel is cation selective. With 145 mM Na+ on both sides of the membrane, the single-channel current-voltage relation was almost linear in the voltage range between -80 and +80 mV, the conductance showing some variability in the range between 140 and 170 pS. All monovalent alkali cations tested, as well as NH4+, permeated the channel effectively. Using the Goldman-Hodgkin-Katz equation for the reversal potential, the permeability ratios with respect to Na+ were estimated to be: 1.32 for K+, 1.18 for NH4+, 1.15 for Rb+, 1.09 for Cs+, and 0.57 for Li+. Divalent cations, i.e. Mg2+ and Ca2+, in the external solution depressed not only the inward but also the outward Na+ currents, although reversal potential measurements indicated that both ions have considerably higher permeabilities than Na+ (PMg/PNa = 2.31; PCa/PNa = 9.55). The conductance-activity relation for Na+ was described by a hyperbolic curve. The maximal conductance was about 195 pS and the half-saturating activity 45 mM. This result suggests that Na+ ions bind to sites in the channel. All data were fitted by a model based on the Eyring's reaction rate theory, in which the receptor channel is a one-ion pore with three energy barriers and two internal sites. PMID:7519261

  12. Frequency of alcohol consumption in humans; the role of metabotropic glutamate receptors and downstream signaling pathways

    PubMed Central

    Meyers, J L; Salling, M C; Almli, L M; Ratanatharathorn, A; Uddin, M; Galea, S; Wildman, D E; Aiello, A E; Bradley, B; Ressler, K; Koenen, K C

    2015-01-01

    Rodent models implicate metabotropic glutamate receptors (mGluRs) and downstream signaling pathways in addictive behaviors through metaplasticity. One way mGluRs can influence synaptic plasticity is by regulating the local translation of AMPA receptor trafficking proteins via eukaryotic elongation factor 2 (eEF2). However, genetic variation in this pathway has not been examined with human alcohol use phenotypes. Among a sample of adults living in Detroit, Michigan (Detroit Neighborhood Health Study; n=788; 83% African American), 206 genetic variants across the mGluR–eEF2–AMPAR pathway (including GRM1, GRM5, HOMER1, HOMER2, EEF2K, MTOR, EIF4E, EEF2, CAMK2A, ARC, GRIA1 and GRIA4) were found to predict number of drinking days per month (corrected P-value <0.01) when considered as a set (set-based linear regression conducted in PLINK). In addition, a CpG site located in the 3′-untranslated region on the north shore of EEF2 (cg12255298) was hypermethylated in those who drank more frequently (P<0.05). Importantly, the association between several genetic variants within the mGluR–eEF2–AMPAR pathway and alcohol use behavior (i.e., consumption and alcohol-related problems) replicated in the Grady Trauma Project (GTP), an independent sample of adults living in Atlanta, Georgia (n=1034; 95% African American), including individual variants in GRM1, GRM5, EEF2, MTOR, GRIA1, GRIA4 and HOMER2 (P<0.05). Gene-based analyses conducted in the GTP indicated that GRM1 (empirical P<0.05) and EEF2 (empirical P<0.01) withstood multiple test corrections and predicted increased alcohol consumption and related problems. In conclusion, insights from rodent studies enabled the identification of novel human alcohol candidate genes within the mGluR–eEF2–AMPAR pathway. PMID:26101849

  13. Homeostatic Changes in GABA and Glutamate Receptors on Excitatory Cortical Neurons during Sleep Deprivation and Recovery

    PubMed Central

    del Cid-Pellitero, Esther; Plavski, Anton; Mainville, Lynda; Jones, Barbara E.

    2017-01-01

    Neuronal activity is regulated in a homeostatic manner through changes in inhibitory GABA and excitatory glutamate (Glu) AMPA (A) receptors (GluARs). Using immunofluorescent staining, we examined whether calcium/calmodulin-dependent protein kinase IIα (CaMKIIα)-labeled (+) excitatory neurons in the barrel cortex undergo such homeostatic regulation following enforced waking with associated cortical activation during the day when mice normally sleep the majority of the time. Sleep deprived mice were prevented from falling asleep by unilateral whisker stimulation and sleep recovery (SR) mice allowed to sleep freely following deprivation. In parallel with changes in c-Fos reflecting changes in activity, (β2-3 subunits of) GABAA Rs were increased on the membrane of CaMKIIα+ neurons with enforced waking and returned to baseline levels with SR in barrel cortex on sides both contra- and ipsilateral to the whisker stimulation. The GABAAR increase was correlated with increased gamma electroencephalographic (EEG) activity across conditions. On the other hand, (GluA1 subunits of) AMPA Rs were progressively removed from the membrane of CaMKIIα+ neurons by (Rab5+) early endosomes during enforced waking and returned to the membrane by (Rab11+) recycling endosomes during SR. The internalization of the GluA1Rs paralleled the expression of Arc, which mediates homeostatic regulation of AMPA receptors through an endocytic pathway. The reciprocal changes in GluA1Rs relative to GABAARs suggest homeostatic down-scaling during enforced waking and sensory stimulation and restorative up-scaling during recovery sleep. Such homeostatic changes with sleep-wake states and their associated cortical activities could stabilize excitability and activity in excitatory cortical neurons.

  14. Lack of effect of antipsychotic and antidepressant drugs on glutamate receptor mRNA levels in rat brains.

    PubMed

    Oretti, R G; Spurlock, G; Buckland, P R; McGuffin, P

    1994-08-15

    By employing multiprobe oligonucleotide solution hybridisation (MOSH) we have measured the levels of mRNA encoding the NMDA receptor subtypes (R1, R2A, R2B and R2C) and the non-NMDA glutamate receptor subtypes (GluR1, 2, 3, and 4) within rat brain following, 1-32 days of antipsychotic or antidepressant drug administration. The results suggest that the drugs studied do not significantly alter rat glutamatergic system mRNA levels when compared to controls.

  15. Distribution and functional properties of glutamate receptors in the leech central nervous system.

    PubMed

    Dierkes, P W; Hochstrate, P; Schlue, W R

    1996-06-01

    1. The effect of kainate and other glutamatergic agonists on the membrane potential (Em), the intracellular Na+ activity (aNai), and the intracellular free Ca2+ concentration ([Ca2+]i) of identified leech neurons and neuropile glial cells was measured with conventional and ion-sensitive microelectrodes, as well as with the use of the iontophoretically injected fluorescent indicators sodium-binding benzofuran isophthalate and Fura-2. 2. In Retzius neurons, AE, L, 8, and 101 motoneurons, and in the unclassified 50 neurons (Leydig cells) and AP neurons, as well as in neuropile glial cells, bath application of 100 microM kainate evoked a marked membrane depolarization and an increase in aNai and [Ca2+]i. The kainate-induced aNai increase persisted in solutions with high Mg2+ concentration in which synaptic transmission is blocked. 3. A membrane depolarization as well as an increase in aNai and [Ca2+]i was also evoked by L-glutamate, quisqualate, and L-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA). The agonist-induced [Ca2+]i increase was inhibited by 6,7-dinitroquinoxaline-2,3-dione (DNQX). 4. In Ca(2+)-free solution, the kainate-induced [Ca2+]i increase was abolished in the neurons and in neuropile glial cells, whereas membrane depolarization and aNai increase were unchanged. In Na(+)-free solution, kainate had no effect on Em, aNai, or [Ca2+]i in the neurons. 5. In the mechanosensory T, P, and N neurons, kainate induced considerably smaller membrane depolarizations than in the other neurons or in neuropile glial cells, and it had no significant effect on aNai or [Ca2+]i. 6. It is concluded that in leech segmental ganglia the majority of the neurons and the neuropile glial cells, but probably not the mechanosensory neurons, possess glutamate receptors of the AMPA-kainate type. In the neurons, the [Ca2+]i increase caused by glutamatergic agonists is due to Ca2+ influx through voltage-dependent Ca2+ channels that are activated by the agonist

  16. In vivo variation in metabotropic glutamate receptor subtype 5 binding using positron emission tomography and [11C]ABP688

    PubMed Central

    DeLorenzo, Christine; Kumar, J S Dileep; Mann, J John; Parsey, Ramin V

    2011-01-01

    The metabotropic glutamate receptor subtype 5 (mGluR5) has been implicated in the pathophysiology of mood and anxiety disorders. Recently, a positron emission tomography (PET) tracer exhibiting high selectivity and specificity for mGluR5, 3-(6-methyl-pyridin-2-ylethynyl)-cyclohex-2-enone-O-11C-methyl-oxime ([11C]ABP688), was developed. In this work, eight healthy adult male humans were imaged twice to assess within-subject [11C]ABP688 binding variability using PET. In seven of the eight subjects, significantly higher binding was observed during the second (retest) scan. This binding increase could not be definitively explained by differences in ligand injected mass or dose, or changes in metabolism between scans. In addition, this type of systematic binding increase was not observed in a [11C]ABP688 test–retest study performed by our group on anaesthetized baboons. It is therefore possible that the increased binding was because of physiological changes occurring between scans, such as changes in endogenous glutamate levels. If PET imaging with [11C]ABP688 could detect such differences, as preliminary evidence suggests, it could be used to help uncover the role of glutamate in the pathophysiology of brain disorders. However, regardless of its ability to detect endogenous glutamate differences, [11C]ABP688 binding variability could make accurate assessments of drug occupancy or group differences using this ligand difficult. PMID:21792244

  17. Morphine sensitization increases the extracellular level of glutamate in CA1 of rat hippocampus via μ-opioid receptor.

    PubMed

    Farahmandfar, Maryam; Karimian, Seyed Morteza; Zarrindast, Mohammad-Reza; Kadivar, Mehdi; Afrouzi, Hossein; Naghdi, Nasser

    2011-04-25

    Repeated administration of abuse drugs such as morphine elicits a progressive enhancement of drug-induced behavioral responses, a phenomenon termed behavioral sensitization. These changes in behavior may reflect plastic changes requiring regulation of glutamatergic system in the brain. In this study, we investigated the effect of morphine sensitization on extracellular glutamate concentration in the hippocampus, a brain region rich in glutamatergic neurons. Sensitization was induced by subcutaneous (s.c.) injection of morphine, once daily for 3 days followed by 5 days free of the opioid treatment. The results showed that extracellular glutamate concentration in the CA1 was decreased following administration of morphine in non-sensitized rats. However, morphine-induced behavioral sensitization significantly increased the extracellular glutamate concentration in this area. The enhancement of glutamate in morphine sensitized rats was prevented by administration of naloxone 30 min before each of three daily doses of morphine. These results suggest an adaptation of the glutamatergic neuronal transmission in the hippocampus after morphine sensitization and it is postulated that opioid receptors may play an important role in this effect.

  18. Inhibition of NMDA-type glutamate receptors induces arousal from torpor in hibernating arctic ground squirrels (Urocitellus parryii).

    PubMed

    Jinka, Tulasi R; Rasley, Brian T; Drew, Kelly L

    2012-09-01

    Hibernation is an adaptation to overcome periods of resource limitation often associated with extreme climatic conditions. The hibernation season consists of prolonged bouts of torpor that are interrupted by brief interbout arousals. Physiological mechanisms regulating spontaneous arousals are poorly understood, but may be related to a need for gluconeogenesis or elimination of metabolic wastes. Glutamate is derived from glutamine through the glutamate-glutamine cycle and from glucose via the pyruvate carboxylase pathway when nitrogen balance favors formation of glutamine. This study tests the hypothesis that activation of NMDA-type glutamate receptors (NMDAR) maintains torpor in arctic ground squirrel (arctic ground squirrel (AGS); Urocitellus parryii). Administration of NMDAR antagonists MK-801 (5 mg/kg, i.p.) that crosses the blood-brain barrier and AP5 (5 mg/kg, i.p.) that does not cross the blood-brain barrier induced arousal in AGS. Central administration of MK-801 (0.2, 2, 20 or 200 μg; icv) to hibernating AGS failed to induce arousal. Results suggest that activation of NMDAR at a peripheral or circumventricular site is necessary to maintain prolonged torpor and that a decrease in glutamate at these sites may contribute to spontaneous arousal in AGS.

  19. Low nanomolar serotonin inhibits the glutamate receptor/nitric oxide/cyclic GMP pathway in slices from adult rat cerebellum.

    PubMed

    Maura, G; Guadagnin, A; Raiteri, M

    1995-09-01

    The function of serotonin afferents to the cerebellum has been investigated by monitoring the effects of serotoninergic drugs on the production of cyclic GMP elicited in cerebellar slices by activation of ionotropic glutamate receptors. Exposure of adult rat cerebellar slices to N-methyl-D-aspartate (1 nM to 1 microM) or to (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA; 1 nM to 10 microM) elicited concentration-dependent and saturable rises in the levels of cyclic GMP. These responses were blocked by selective antagonists at the N-methyl-D-aspartate or AMPA receptors and by inhibiting nitric oxide synthase, but were insensitive to tetrodotoxin. When tested between 0.1 and 10 nM, serotonin, the serotonin1A receptor agonist (+/-)-8-hydroxy-2-(di-n-propylamino)tetralin and the serotonin2 receptor agonist (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane inhibited, concentration-dependently, the cyclic GMP responses evoked by near-maximal (0.1 microM) concentrations of N-methyl-D-aspartate or AMPA. The EC50 values (concentrations causing half-maximal effect) ranged between 0.7 and 2.1 nM. The actions of serotonin were totally abolished by methiothepin, a mixed-type serotonin receptor antagonist. Thus, the serotonergic cerebellar afferents may exert a potent inhibitory control on the excitatory transmission mediated by N-methyl-D-aspartate and AMPA receptors; the inhibition occurs through both serotonin1A and serotonin2 receptors. As the glutamate receptor-dependent cyclic GMP responses involve production of nitric oxide, a diffusible activator of guanylate cyclase, the above inhibitory serotonin receptors may have multiple localization.(ABSTRACT TRUNCATED AT 250 WORDS)

  20. NMR spectroscopy of the ligand binding core of ionotropic glutamate receptor 2 bound to 5-substituted willardiine partial agonists

    PubMed Central

    Fenwick, Michael K.; Oswald, Robert E.

    2008-01-01

    Glutamate receptors mediate neuronal intercommunication in the central nervous system by coupling extracellular neurotransmitter-receptor interactions to ion channel conductivity. To gain insight into structural and dynamical factors that underlie this coupling, solution NMR experiments were performed on the bi-lobed ligand-binding core of glutamate receptor 2 in complexes with a set of willardiine partial agonists. These agonists are valuable for studying structure-function relationships because their 5-position substituent size is correlated with ligand efficacy and extent of receptor desensitization whereas the substituent electronegativity is correlated with ligand potency. NMR results show that the protein backbone amide chemical shift deviations correlate mainly with efficacy and extent of desensitization. Pronounced deviations occur at specific residues in the ligand-binding site and in the two helical segments that join the lobes by a disulfide bond. Experiments detecting conformational exchange show that micro- to millisecond timescale motions also occur near the disulfide bond and vary largely with efficacy and extent of desensitization. These results thus identify regions displaying structural and dynamical dissimilarity arising from differences in ligand-protein interactions and lobe closure which may play a critical role in receptor response. Furthermore, measures of line broadening and conformational exchange for a portion of the ligand-binding site correlate with ligand EC50 data. These results do not have any correlate in the currently available crystal structures and thus provide a novel view of ligand-binding events that may be associated with agonist potency differences. PMID:18387631

  1. Modulation of dopamine and noradrenaline release and of intracellular Ca2+ concentration by presynaptic glutamate receptors in hippocampus.

    PubMed

    Malva, J O; Carvalho, A P; Carvalho, C M

    1994-12-01

    1. We studied the release of [3H]-dopamine and [3H]-noradrenaline (NA) from hippocampal synaptosomes induced by glutamate receptors and the associated Ca2+ influx through Ca2+ channels. The release of tritiated neurotransmitters was studied by use of superfusion system and the intracellular free Ca2+ concentration ([Ca2+]i) was determined by a fluorimetric assay with Indo-1 as a probe for Ca2+. 2. Presynaptic glutamate receptor activation induced Ca(2+)-dependent release of [3H]-dopamine and [3H]-NA from rat hippocampal synaptosomes. Thus, L-glutamate induced the release of both neurotransmitters in a dose-dependent manner (EC50 = 5.62 microM), and the effect of 100 microM L-glutamate was inhibited by 83.8% in the presence of 10 microM 6-cyano-7-nitroquinoxaline-2,3-dioxine (CNQX), but was not affected by 1 microM (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5,10-imine (MK-801). 3. Other glutamate receptor agonists also stimulated the Ca(2+)-dependent release of [3H]-dopamine and [3H]-NA as follows: N-methyl-D-aspartate (NMDA), at 200 microM, released 3.65 +/- 0.23% of the total 3H catecholamines, and this effect was inhibited by 81.2% in the presence of 1 microM MK-801; quisqualate (50 microM), S-alpha-amino-3-hydroxy-5-methyl-4-isoxazolopropionic acid (AMPA) (100 microM) or kainate (100 microM) released 1.57 +/- 0.26%, 1.93 +/- 0.17% and 2.09 +/- 0.22%, of the total 3H catecholamines, respectively. 4. The ionotropic glutamate receptor agonist, AMPA, induced an increase in the [Ca2+]i which was inhibited by 58.6% in the presence of 10 microM CNQX. In contrast, the increase in [Ca2+]i due to stimulation by glutamate was not sensitive to CNQX or MK-801.5. Nitrendipine, at I JAM, did not inhibit the neurotransmitter release induced by AMPA, but, both 0.5 micro M -conotoxin GVIA (w-CgTx) and 100 nM w-Aga IVA reduced catecholamine release to 49.03 +/- 3.79% and 46.06 +/- 10.51% of the control, respectively. In the presence of both toxins the release was

  2. Purification and biochemical characterization of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate-sensitive L-glutamate receptors of pig brain.

    PubMed Central

    Chang, Y C; Wu, T Y; Li, B F; Gao, L H; Liu, C I; Wu, C L

    1996-01-01

    Two preparations of glutamate receptors were purified from the synaptic junctions of pig brain by a combination of detergent solubilization, anion-exchange chromatography, wheat-germ agglutinin affinity chromatography and sedimentation through sucrose gradients. These preparations were enriched in specific L-[3H]glutamate binding activity (> 5000 pmol of glutamate binding sites/mg of protein), and the rank order of ligand affinity for binding to these preparations was: quisqualate > 6-cyano-7- nitroquinoxaline-2,3-dione > alpha-amino-3-hydroxy-5-methyl-4- isoxazolepropionic acid (AMPA) > L-glutamate > kainate > > N-methyl-D-aspartate approximately L-2-amino-4-phosphonobutyrate. SDS/PAGE analysis revealed that more than 80% of the protein in either of these preparations appeared as a single protein band of 106 kDa. Two-dimensional gel electrophoresis further revealed that these 106 kDa proteins consisted of a series of acidic proteins which were recognized by antibodies against rat AMPA receptor subunits. These 106 kDa proteins were also recognized by wheatgerm agglutinin and concanavalin A; in addition, peptide N-glycosidase F treatment of these preparations decreased their size to 99 kDa. Our results suggest that the putative glutamate receptors isolated here are likely to belong to the AMPA subtype of glutamate receptors in pig brain. Using the purification procedure reported here, 5 micrograms of AMPA receptor proteins can be isolated from 250 g of pig brain tissue. PMID:8870648

  3. Targeting glutamate receptors to tackle the pathogenesis, clinical symptoms and levodopa-induced dyskinesia associated with Parkinson's disease.

    PubMed

    Duty, Susan

    2012-12-01

    The appearance of levodopa-induced dyskinesia (LID) and ongoing degeneration of nigrostriatal dopaminergic neurons are two key features of Parkinson's disease (PD) that current treatments fail to address. Increased glutamate transmission contributes to the motor symptoms in PD, to the striatal plasticity that underpins LID and to the progression of neurodegeneration through excitotoxic mechanisms. Glutamate receptors have therefore long been considered as potential targets for pharmacological intervention in PD, with emphasis on either blocking activation of 2-amino-3-(5-methyl-3-oxo-1,2-oxazol-4-yl)propanoic acid (AMPA), N-methyl-D-aspartate (NMDA) or excitatory metabotropic glutamate (mGlu) 5 receptors or promoting the activation of group II/III mGlu receptors. Following a brief summary of the role of glutamate in PD and LID, this article explores the current status of pharmacological studies in pre-clinical rodent and primate models through to clinical trials, where applicable, that support the potential of glutamate-based therapeutic interventions. To date, AMPA antagonists have shown good efficacy against LID in rat and primate models, but the failure of perampanel to lessen LID in clinical trials casts doubt on the translational potential of this approach. In contrast, antagonists selective for NR2B-containing NMDA receptors were effective against LID in animal models and in small-scale clinical trials, though observed adverse cognitive effects need addressing. So far, mGlu5 antagonists or negative allosteric modulators (NAMs) look set to become the first introduced for tackling LID, with AFQ-056 reported to exhibit good efficacy in phase II clinical trials. NR2B antagonists and mGlu5 NAMs may subsequently prove to also be effective disease-modifying agents if their protective effects in rat and primate models of PD, respectively, are replicated in the next stages of investigation. Finally, group III mGlu4 agonists or positive allosteric modulators (PAMs

  4. Differential expression of group I metabotropic glutamate receptors in functionally distinct hippocampal interneurons.

    PubMed

    van Hooft, J A; Giuffrida, R; Blatow, M; Monyer, H

    2000-05-15

    Metabotropic glutamate receptors (mGluRs) have been proposed to be involved in oscillatory rhythmic activity in the hippocampus. However, the subtypes of mGluRs involved and their precise distribution in different populations of interneurons is unclear. In this study, we combined functional analysis of mGluR-mediated inward currents in CA1 oriens-alveus interneurons with anatomical and immunocytochemical identification of these interneurons and expression analysis of group I mGluR using single-cell reverse transcription-PCR (RT-PCR). Four major interneuron subtypes could be distinguished based on the mGluR-mediated inward current induced by the application of 100 microm trans-(1S,3R)-1-aminocyclopentane-1, 3-dicarboxylic acid (ACPD) under voltage-clamp conditions and the action potential firing pattern under current-clamp conditions. Type I interneurons responded with a large inward current of approximately 224 pA, were positive for somatostatin, and the majority expressed both mGluR1 and mGluR5. Type II interneurons responded with an inward current of approximately 80 pA, contained calbindin, and expressed mainly mGluR1. Type III interneurons responded with an inward current of approximately 60 pA. These interneurons were fast-spiking, contained parvalbumin, and expressed mainly mGluR5. Type IV interneurons did not respond with an inward current upon application of ACPD, yet they expressed group I mGluRs. Activation of group I mGluRs under current-clamp conditions increased spike frequency and resulted in rhythmic firing activity in type I and II, but not in type III and IV, interneurons. RT-PCR results suggest that activation of mGluR1 in the subsets of GABAergic interneurons, classified here as type I and II, may play an important role in mediating synchronous activity.

  5. Riluzole mediates anti-tumor properties in breast cancer cells independent of metabotropic glutamate receptor-1.

    PubMed

    Speyer, Cecilia L; Nassar, Mahdy A; Hachem, Ali H; Bukhsh, Miriam A; Jafry, Waris S; Khansa, Rafa M; Gorski, David H

    2016-06-01

    Riluzole, the only drug approved by the FDA for treating amyotrophic lateral sclerosis, inhibits melanoma proliferation through its inhibitory effect on glutamatergic signaling. We demonstrated that riluzole also inhibits the growth of triple-negative breast cancer (TNBC) and described a role for metabotropic glutamate receptor-1 (GRM1) in regulating TNBC cell growth and progression. However, the role of GRM1 in mediating riluzole's effects in breast cancer has not been fully elucidated. In this study, we seek to determine how much of riluzole's action in breast cancer is mediated through GRM1. We investigated anti-tumor properties of riluzole in TNBC and ER+ cells using cell growth, invasion, and soft-agar assays and compared riluzole activity with GRM1 levels. Using Lentiviral vectors expressing GRM1 or shGRM1, these studies were repeated in cells expressing high or low GRM1 levels where the gene was either silenced or overexpressed. Riluzole inhibited proliferation, invasion, and colony formation in both TNBC and ER+ cells. There was a trend between GRM1 expression in TNBC cells and their response to riluzole in both cell proliferation and invasion assays. However, silencing and overexpression studies had no effect on cell sensitivity to riluzole. Our results clearly suggest a GRM1-independent mechanism through which riluzole mediates its effects on breast cancer cells. Understanding the mechanism by which riluzole mediates breast cancer progression will be useful in identifying new therapeutic targets for treating TNBC and in facilitating stratification of patients in clinical trials using riluzole in conjunction with conventional therapy.

  6. Metabotropic Glutamate Receptor 5/Homer Interactions Underlie Stress Effects on Fear

    PubMed Central

    Tronson, Natalie C.; Guzman, Yomayra F.; Guedea, Anita L.; Huh, Kyu Hwan; Gao, Can; Schwarz, Martin K.; Radulovic, Jelena

    2010-01-01

    Background Glutamatergic transmission is one of the main components of the stress response, nevertheless, its role in the emotional stress sequelae is not known. Here, we investigated whether interactions between group I metabotropic glutamate receptors (mGluR1 and mGluR5) and Homer proteins mediate the delayed and persistent enhancement of fear induced by acute stress. Methods Antagonists and inverse agonists of mGluR1 and mGluR5 were injected into the hippocampus after immobilization stress and before contextual fear conditioning. mGluR5 was displaced from constitutive Homer scaffolds by viral transfection of Homer1a or injection of TAT decoy peptides. The effects of these manipulations on stress-enhanced fear were determined. Results We show that stress induces interactions between hippocampal mGluR5 and Homer1a, causes a sustained, ligand-independent mGluR5 activity, and enhances contextual fear. Consistent with this mechanism, enhancement of fear was abolished by delayed post-stress application of inverse agonists, but not antagonists, of mGluR5. The effect of stress was mimicked by virally transfected of Homer1a or injection of TAT-mGluR C-tail decoy peptides into the hippocampus. Conclusions Constitutive activation of mGluR5 is identified as a principal hippocampal mechanism underlying the delayed stress effects on emotion and memory. Inverse agonists, but not antagonists, of mGluR5 are therefore proposed as a preventive treatment option for acute- and posttraumatic stress disorders. PMID:21075228

  7. [Ligands of glutamate and dopamine receptors evenly labeled with hydrogen isotopes].

    PubMed

    Zolotarev, Iu A; Firstova, Iu Iu; Abaimov, D A; Dadaian, A K; Kosik, V S; Novikov, A V; Krasnov, N V; Vas'kovskiĭ, B V; Nazimov, I V; Kovalev, G I; Miasoedov, N F

    2009-01-01

    A reaction of high-temperature solid-phase catalytic isotope exchange (HSCIE) was studied for the preparation of tritium- and deuterium-labeled ligands of glutamate and dopamine receptors. Tritium-labeled (5S,10R)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclopenten-5,10-imine ([G-(3)H]MK-801) and R(+)-7-hydroxy-N,N-di-n-propyl-2-aminotetraline ([G-(3)H]-7-OH-DPAT) were obtained with a specific activity of 210 and 120 Ci/mol, respectively. The isotopomeric distribution of deuterium-labeled ligands was studied using time-of-flight mass-spectrometer MX 5310 (ESI-o-TOF) with electrospray and orthogonal ion injection. Mean deuterium incorporation per ligand molecule was 11.09 and 3.21 atoms for [G-(2)H]MK-801 and [G-(2)H]-7-OH-DPAT, respectively. The isotope label was shown to be distributed all over the ligand molecule. The radioreceptor binding of tritium-labeled ligands [G-(3)H]MK-801 and [G-(3)H]-7-OH-DPAT was analyzed using the brain structure of Vistar rats. It was demonstrated that [G-(3)H]MK-801 specifically binds to hippocampus membranes with K(d) 8.3 +/- 1.4 nM, B(max) being 3345 +/- 300 fmol/mg protein. The [G-(3)H]-7-OH-DPAT ligand specifically binds to rat striatum membranes with K(d) 10.01 +/- 0.91 nM and B(max) 125 +/- 4.5 fmol/mg protein. It was concluded that the HSCIE reaction can be used for the preparation of highly tritium-labeled (+)-MK-801 and 7-OH-DPAT with retention of their physiological activities.

  8. Negative Allosteric Modulators of Metabotropic Glutamate Receptors Subtype 5 in Addiction: a Therapeutic Window

    PubMed Central

    2016-01-01

    Background: Abundant evidence at the anatomical, electrophysiological, and molecular levels implicates metabotropic glutamate receptor subtype 5 (mGluR5) in addiction. Consistently, the effects of a wide range of doses of different mGluR5 negative allosteric modulators (NAMs) have been tested in various animal models of addiction. Here, these studies were subjected to a systematic review to find out if mGluR5 NAMs have a therapeutic potential that can be translated to the clinic. Methods: Literature on consumption/self-administration and reinstatement of drug seeking as outcomes of interest published up to April 2015 was retrieved via PubMed. The review focused on the effects of systemic (i.p., i.v., s.c.) administration of the mGluR5 NAMs 3-((2-Methyl-4-thiazolyl)ethynyl)pyridine (MTEP) and 2-Methyl-6-(phenylethynyl)pyridine (MPEP) on paradigms with cocaine, ethanol, nicotine, and food in rats. Results: MTEP and MPEP were found to reduce self-administration of cocaine, ethanol, and nicotine at doses ≥1mg/kg and 2.5mg/kg, respectively. Dose-response relationship resembled a sigmoidal curve, with low doses not reaching statistical significance and high doses reliably inhibiting self-administration of drugs of abuse. Importantly, self-administration of cocaine, ethanol, and nicotine, but not food, was reduced by MTEP and MPEP in the dose range of 1 to 2mg/kg and 2.5 to 3.2mg/kg, respectively. This dose range corresponds to approximately 50% to 80% mGluR5 occupancy. Interestingly, the limited data found in mice and monkeys showed a similar therapeutic window. Conclusion: Altogether, this review suggests a therapeutic window for mGluR5 NAMs that can be translated to the treatment of substance-related and addictive disorders. PMID:26802568

  9. Blocking metabotropic glutamate receptor subtype 5 relieves maladaptive chronic stress consequences.

    PubMed

    Peterlik, Daniel; Stangl, Christina; Bauer, Amelie; Bludau, Anna; Keller, Jana; Grabski, Dominik; Killian, Tobias; Schmidt, Dominic; Zajicek, Franziska; Jaeschke, Georg; Lindemann, Lothar; Reber, Stefan O; Flor, Peter J; Uschold-Schmidt, Nicole

    2017-01-01

    Etiology and pharmacotherapy of stress-related psychiatric conditions and somatoform disorders are areas of high unmet medical need. Stressors holding chronic plus psychosocial components thereby bear the highest health risk. Although the metabotropic glutamate receptor subtype 5 (mGlu5) is well studied in the context of acute stress-induced behaviors and physiology, virtually nothing is known about its potential involvement in chronic psychosocial stress. Using the mGlu5 negative allosteric modulator CTEP (2-chloro-4-[2-[2,5-dimethyl-1-[4-(trifluoromethoxy)phenyl]imidazol-4yl]ethynyl]pyridine), a close analogue of the clinically active drug basimglurant - but optimized for rodent studies, as well as mGlu5-deficient mice in combination with a mouse model of male subordination (termed CSC, chronic subordinate colony housing), we demonstrate that mGlu5 mediates multiple physiological, immunological, and behavioral consequences of chronic psychosocial stressor exposure. For instance, CTEP dose-dependently relieved hypothalamo-pituitary-adrenal axis dysfunctions, colonic inflammation as well as the CSC-induced increase in innate anxiety; genetic ablation of mGlu5 in mice largely reproduced the stress-protective effects of CTEP and additionally ameliorated CSC-induced physiological anxiety. Interestingly, CSC also induced an upregulation of mGlu5 in the hippocampus, a stress-regulating brain area. Taken together, our findings provide evidence that mGlu5 is an important mediator for a wide range of chronic psychosocial stress-induced alterations and a potentially valuable drug target for the treatment of chronic stress-related pathologies in man.

  10. PICK1 and phosphorylation of the glutamate receptor 2 (GluR2) AMPA receptor subunit regulates GluR2 recycling after NMDA receptor-induced internalization.

    PubMed

    Lin, Da-Ting; Huganir, Richard L

    2007-12-12

    Changes in surface trafficking of AMPA receptors play an important role in synaptic plasticity. Phosphorylation of the C terminus of the AMPA receptor (AMPAR) subunit glutamate receptor 2 (GluR2) and the binding of GluR2 to the PDZ [postsynaptic density-95/Discs large/zona occludens-1]-domain containing protein, protein interacting with protein kinase C (PICK1), have been proposed to play an important role in NMDA receptor dependent internalization of GluR2. However, the fate of internalized GluR2 after NMDA receptor (NMDAR) activation is still unclear. Both recycling and degradation of GluR2 after the activation of NMDAR have been reported. Here, we used a pH-sensitive green fluorescent protein variant, pHluorin, tagged to the N terminus of GluR2 (pH-GluR2) to study the dynamic internalization and recycling of GluR2 after NMDAR activation. Using fluorescence recovery after photobleach (FRAP), we directly demonstrate that internalized pH-GluR2 subunits recycle back to the cell surface after NMDAR activation. We further demonstrate that changing the phosphorylation state of the S880 residue at the C terminus of GluR2 does not affect NMDAR-dependent GluR2 internalization, but alters the recycling of GluR2 after NMDAR activation. In addition, mutation of the N-ethylmaleimide-sensitive fusion protein (NSF) binding site in the pH-GluR2 slows receptor recycling. Finally, neurons lacking PICK1 display normal NMDAR dependent GluR2 internalization compared with wild-type neurons, but demonstrate accelerated GluR2 recycling after NMDAR activation. These results indicate that phosphorylation of GluR2 S880 and NSF and PICK1 binding to GluR2 dynamically regulate GluR2 recycling.

  11. Unlocking the secrets of the δ2 glutamate receptor: A gatekeeper for synaptic plasticity in the cerebellum.

    PubMed

    Kohda, Kazuhisa; Kakegawa, Wataru; Yuzaki, Michisuke

    2013-11-01

    Long-term changes in synaptic transmission in the central nervous system, such as long-term potentiation and long-term depression (LTD), are believed to underlie learning and memory in vivo. Despite intensive research, the precise molecular mechanisms underlying these phenomena have remained unclear. LTD is most commonly caused by the endocytosis of postsynaptic AMPA-type glutamate receptors, triggered by activity-induced serine phosphorylation of the GluA2 subunit. Interestingly, cerebellar LTD, which occurs at synapses between parallel fibers (PFs; axons of granule cells) and Purkinje cells, is unique in requiring an additional type of glutamate receptor, the δ2 receptor (GluD2). Cbln1 was recently identified as a GluD2 ligand that regulates PF synapse formation and maintenance. However, how GluD2 induces downstream signaling in Purkinje cells to regulate LTD induction is unknown. We here present evidence that GluD2 reduces the tyrosine phosphorylation level of the GluA2 subunit via PTPMEG, a protein tyrosine phosphatase that binds to GluD2's C-terminus. We also found that the serine phosphorylation of GluA2, a crucial step for AMPA-receptor endocytosis, requires prior tyrosine dephosphorylation. Thus, GluD2 may serve as a gatekeeper for LTD induction by coordinating interactions between GluA2's 2 phosphorylation sites.

  12. The Extracellular-Regulated Kinase Effector Lk6 is Required for Glutamate Receptor Localization at the Drosophila Neuromuscular Junction

    PubMed Central

    Hussein, Nizar A.; Delaney, Taylor L.; Tounsel, Brittany L.; Liebl, Faith L.W.

    2016-01-01

    The proper localization and synthesis of postsynaptic glutamate receptors are essential for synaptic plasticity. Synaptic translation initiation is thought to occur via the target of rapamycin (TOR) and mitogen-activated protein kinase signal-integrating kinase (Mnk) signaling pathways, which is downstream of extracellular-regulated kinase (ERK). We used the model glutamatergic synapse, the Drosophila neuromuscular junction, to better understand the roles of the Mnk and TOR signaling pathways in synapse development. These synapses contain non-NMDA receptors that are most similar to AMPA receptors. Our data show that Lk6, the Drosophila homolog of Mnk1 and Mnk2, is required in either presynaptic neurons or postsynaptic muscle for the proper localization of the GluRIIA glutamate receptor subunit. Lk6 may signal through eukaryotic initiation factor (eIF) 4E to regulate the synaptic levels of GluRIIA as either interfering with eIF4E binding to eIF4G or expression of a nonphosphorylatable isoform of eIF4E resulted in a significant reduction in GluRIIA at the synapse. We also find that Lk6 and TOR may independently regulate synaptic levels of GluRIIA. PMID:27199570

  13. Status epilepticus decreases glutamate receptor 2 mRNA and protein expression in hippocampal pyramidal cells before neuronal death

    PubMed Central

    Grooms, Sonja Y.; Opitz, Thoralf; Bennett, Michael V. L.; Zukin, R. Suzanne

    2000-01-01

    Kainic acid (KA)-induced status epilepticus in adult rats leads to delayed, selective death of pyramidal neurons in the hippocampal CA1 and CA3. Death is preceded by down-regulation of glutamate receptor 2 (GluR2) mRNA and protein [the subunit that limits Ca2+ permeability of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors] in CA1 and CA3, as indicated by in situ hybridization, immunolabeling, and quantitative Western blotting. GluR1 mRNA and protein are unchanged or slightly increased before cell death. These changes could lead to formation of GluR2-lacking, Ca2+-permeable AMPA receptors and increased toxicity of endogenous glutamate. GluR2 immunolabeling is unchanged in granule cells of the dentate gyrus, which are resistant to seizure-induced death. Thus, formation of Ca2+-permeable AMPA receptors may be a critical mediator of delayed neurodegeneration after status epilepticus. PMID:10725374

  14. A-Kinase Anchoring Protein 79/150 Coordinates Metabotropic Glutamate Receptor Sensitization of Peripheral Sensory Neurons

    PubMed Central

    Szteyn, Kalina; Rowan, Matthew P.; Gomez, Ruben; Du, Junhui; Carlton, Susan M.; Jeske, Nathaniel A.

    2016-01-01

    Glutamate serves as the primary excitatory neurotransmitter in the nervous system. Previous studies have identified a role for glutamate and group I metabotropic receptors as targets for study in peripheral inflammatory pain. However, the coordination of signaling events that transpire from receptor activation to afferent neuronal sensitization has not been explored. Herein, we identify that scaffolding protein A-Kinase Anchoring Protein 79/150 (AKAP150) coordinates increased peripheral thermal sensitivity following group I metabotropic receptor (mGluR5) activation. In both acute and persistent models of thermal somatosensory behavior, we report that mGluR5 sensitization requires AKAP150 expression. Furthermore, electrophysiological approaches designed to record afferent neuronal activity reveal that mGluR5 sensitization also requires functional AKAP150 expression. In dissociated primary afferent neurons, mGluR5 activation increases TRPV1 responses in an AKAP dependent manner through a mechanism that induces AKAP association with TRPV1. Experimental results presented herein identify a mechanism of receptor-driven scaffolding association with ion channel targets. Importantly, this mechanism could prove significant in the search for therapeutic targets that repress episodes of acute pain from becoming chronic in nature. PMID:26172554

  15. Protection from neuronal damage induced by combined oxygen and glucose deprivation in organotypic hippocampal cultures by glutamate receptor antagonists.

    PubMed

    Strasser, U; Fischer, G

    1995-07-31

    Organotypic hippocampal cultures were exposed to defined periods (30 and 60 min) of combined oxygen and glucose deprivation, mimicking transient ischemic conditions. The involvement of different glutamate receptors in individual hippocampal subfields (CA1, CA3 and dentate gyrus) was studied using antagonists of NMDA (dizocilpine) and AMPA/kainate receptors (CNQX and GYKI 52466). Staining with the fluorescent dye propidium iodide (PI) allowed detection of damaged cells. For quantitative determination of neuronal damage, fluorescence intensity was measured after a 22 h recovery period and was related to maximal fluorescence intensity measured after fixation and PI restaining of the cultures at the end of the experiment. Dizocilpine (10 microM), CNQX (100 microM) and GYKI 52466 (100 microM) provided complete protection in CA1, CA3 and dentate gyrus following the moderate ischemic insult, when the antagonists were present permanently. This indicates that none of the ionotropic glutamate receptor subtypes dominated toxicity in the most sensitive subpopulation of neurons. When applied only during the recovery period protection with dizocilpine (10 microM) or CNQX (100 microM) was drastically reduced by about 60% in the most sensitive area (CA1), but only slightly by 15% in CA3. Therefore the onset of irreversible damage seems to occur earlier in CA1 than in CA3. Blockade of AMPA/kainate receptors by GYKI 52466 (100 microM) offered no neuroprotection if the compound was applied only during the recovery period.(ABSTRACT TRUNCATED AT 250 WORDS)

  16. Nerve injury-induced changes in Homer/glutamate receptor signaling contribute to the development and maintenance of neuropathic pain.

    PubMed

    Obara, Ilona; Goulding, Scott P; Hu, Jia-Hua; Klugmann, Matthias; Worley, Paul F; Szumlinski, Karen K

    2013-10-01

    While group 1 metabotropic glutamate receptors (mGluRs) and ionotropic N-methyl-d-aspartate (NMDA) receptors regulate nociception, the precise molecular mechanism(s) contributing to glutamate signaling in chronic pain remain unclear. Here we not only confirmed the key involvement of Homer proteins in neuropathic pain, but also distinguished between the functional roles for different Homer family members and isoforms. Chronic constriction injury (CCI) of the sciatic nerve induced long-lasting, time-dependent increases in the postsynaptic density expression of the constitutively expressed (CC) isoforms Homer1b/c and/or Homer2a/b in the spinal dorsal horn and supraspinal structures involved in nociception (prefrontal cortex, thalamus), that co-occurred with increases in their associated mGluRs, NR2 subunits of the NMDA receptor, and the activation of downstream kinases. Virus-mediated overexpression of Homer1c and Homer2b after spinal (intrathecal) virus injection exacerbated CCI-induced mechanical and cold hypersensitivity, however, Homer1 and Homer2 gene knockout (KO) mice displayed no changes in their neuropathic phenotype. In contrast, overexpression of the immediate early gene (IEG) Homer1a isoform reduced, while KO of Homer1a gene potentiated neuropathic pain hypersensitivity. Thus, nerve injury-induced increases in CC-Homers expression promote pain in pathological states, but IEG-Homer induction protects against both the development and maintenance of neuropathy. Additionally, exacerbated pain hypersensitivity in transgenic mice with reduced Homer binding to mGluR5 supports also an inhibitory role for Homer interactions with mGluR5 in mediating neuropathy. Such data indicate that nerve injury-induced changes in glutamate receptor/Homer signaling contribute in dynamic but distinct ways to neuropathic pain processing, which has relevance for the etiology of chronic pain symptoms and its treatment.

  17. The role of dorsomedial hypotalamus ionotropic glutamate receptors in the hypertensive and tachycardic responses evoked by Tityustoxin intracerebroventricular injection.

    PubMed

    Silva, F C; Guidine, Patrícia Alves Maia; Machado, Natalia Lima; Xavier, Carlos Henrique; de Menezes, R C; Moraes-Santos, Tasso; Moraes, Márcio Flávio; Chianca, Deoclécio Alves

    2015-03-01

    The scorpion envenoming syndrome is an important worldwide public health problem due to its high incidence and potential severity of symptoms. Some studies address the high sensitivity of the central nervous system to this toxin action. It is known that cardiorespiratory manifestations involve the activation of the autonomic nervous system. However, the origin of this modulation remains unclear. Considering the important participation of the dorsomedial hypotalamus (DMH) in the cardiovascular responses during emergencial situations, the aim of this work is to investigate the involvement of the DMH on cardiovascular responses induced by intracerebroventricular (icv) injection of Tityustoxin (TsTX, a α-type toxin extracted from the Tityus serrulatus scorpion venom). Urethane-anaesthetized male Wistar rats (n=30) were treated with PBS, muscimol or ionotropic glutamate receptor antagonists, bilaterally in DMH and later, with an icv injection of TsTX, or treated only with PBS in both regions. TsTX evoked a marked increase in mean arterial pressure and heart rate in all control rats. Interestingly, injection of muscimol, a GABAA receptor agonist, did not change the pressor and tachycardic responses evoked by TsTX. Remarkably, the injection ionotropic glutamate receptors antagonists in DMH abolished the pressor and the tachycardic response evoked by TsTX. Our data suggest that the central circuit recruited by TsTX, whose activation results in an array of physiological and behavioral alterations, depend on the activation of DMH ionotropic glutamate receptors. Moreover, our data provide new insights on the central mechanisms involved in the development of symptoms in the severe scorpion envenomation syndrome.

  18. Fragile X mental retardation protein regulates the levels of scaffold proteins and glutamate receptors in postsynaptic densities.

    PubMed

    Schütt, Janin; Falley, Katrin; Richter, Dietmar; Kreienkamp, Hans-Jürgen; Kindler, Stefan

    2009-09-18

    Functional absence of fragile X mental retardation protein (FMRP) causes the fragile X syndrome, a hereditary form of mental retardation characterized by a change in dendritic spine morphology. The RNA-binding protein FMRP has been implicated in regulating postsynaptic protein synthesis. Here we have analyzed whether the abundance of scaffold proteins and neurotransmitter receptor subunits in postsynaptic densities (PSDs) is altered in the neocortex and hippocampus of FMRP-deficient mice. Whereas the levels of several PSD components are unchanged, concentrations of Shank1 and SAPAP scaffold proteins and various glutamate receptor subunits are altered in both adult and juvenile knock-out mice. With the exception of slightly increased hippocampal SAPAP2 mRNA levels in adult animals, altered postsynaptic protein concentrations do not correlate with similar changes in total and synaptic levels of corresponding mRNAs. Thus, loss of FMRP in neurons appears to mainly affect the translation and not the abundance of particular brain transcripts. Semi-quantitative analysis of RNA levels in FMRP immunoprecipitates showed that in the mouse brain mRNAs encoding PSD components, such as Shank1, SAPAP1-3, PSD-95, and the glutamate receptor subunits NR1 and NR2B, are associated with FMRP. Luciferase reporter assays performed in primary cortical neurons from knock-out and wild-type mice indicate that FMRP silences translation of Shank1 mRNAs via their 3'-untranslated region. Activation of metabotropic glutamate receptors relieves translational suppression. As Shank1 controls dendritic spine morphology, our data suggest that dysregulation of Shank1 synthesis may significantly contribute to the abnormal spine development and function observed in brains of fragile X syndrome patients.

  19. Cocaine withdrawal impairs metabotropic glutamate receptor-dependent long-term depression in the nucleus accumbens.

    PubMed

    Huang, Chiung-Chun; Yeh, Che-Ming; Wu, Mei-Ying; Chang, Alice Y W; Chan, Julie Y H; Chan, Samuel H H; Hsu, Kuei-Sen

    2011-03-16

    Neuroadaptation in the nucleus accumbens (NAc), a central component of the mesolimbic dopamine (DA) system, has been implicated in the development of cocaine-induced psychomotor sensitization and relapse to cocaine seeking. However, little is known about the cellular and synaptic mechanisms underlying such adaptation. Using a mouse model of behavioral sensitization, we show that animals withdrawn from repeated cocaine exposure have a selective deficit in the ability to elicit metabotropic glutamate receptor (mGluR)-dependent long-term depression (LTD) in the shell of the NAc in response to bath application of the group I mGluR agonist (S)-3,5-dihydroxyphenylglycine (DHPG). Experiments conducted in the presence of the selective mGluR1 antagonists 7-(hydroxyimino)cyclopropachromen-carboxylate ethyl ester and (S)-(+)-α-amino-4-carboxy-2-methylbenzeneacetic acid, or the mGluR5 antagonist 2-methyl-6-(phenylethynyl)-pyridine, demonstrated that the impaired DHPG-LTD is likely attributable to a loss of mGluR5 function. Quantitative real-time reverse transcriptase-PCR and Western blot analysis revealed significant downregulation of mGluR5, but not mGluR1, mRNA and protein levels in the NAc shell. The inhibitory effect of repeated cocaine exposure on DHPG-LTD was selectively prevented when cocaine was coadministered with the selective D(1)-like DA receptor antagonist (R)-(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine. Furthermore, the levels of brain-derived neurotrophic factor (BDNF) protein in the NAc shell increased progressively after cocaine withdrawal, and the impairment of DHPG-LTD in the NAc shell was not found in slices from BDNF-knock-out mice after cocaine withdrawal. These results suggest that withdrawal from repeated cocaine exposure may result in increased BDNF levels in the NAc shell, which leads to a selective downregulation of mGluR5 and thereby impairs the induction of mGluR-dependent LTD.

  20. NR2B-NMDA receptor mediated modulation of the tyrosine phosphatase STEP regulates glutamate induced neuronal cell death

    PubMed Central

    Poddar, Ranjana; Deb, Ishani; Mukherjee, Saibal; Paul, Surojit

    2011-01-01

    The present study examines the role of a neuron-specific tyrosine phosphatase (STEP) in excitotoxic cell death. Our findings demonstrate that p38 MAPK, a stress-activated kinase that is known to play a role in the etiology of excitotoxic cell death is a substrate of STEP. Glutamate-mediated NMDA receptor stimulation leads to rapid but transient activation of p38 MAPK, which is primarily dependent on NR2A-NMDA receptor activation. Conversely, activation of NR2B-NMDA receptors leads to dephosphorylation and subsequent activation of STEP, which in turn leads to inactivation of p38 MAPK. Thus during transient NMDA receptor stimulation, increases in STEP activity appears to limit the duration of activation of p38 MAPK and improves neuronal survival. However, if NR2B-NMDA receptor stimulation is sustained, protective effects of STEP activation are lost, as these stimuli cause significant degradation of active STEP, leading to secondary activation of p38 MAP kinase. Consistent with this observation, a cell transducible TAT-STEP peptide that constitutively binds to p38 MAPK attenuated neuronal cell death caused by sustained NMDA receptor stimulation. The findings imply that the activation and levels of STEP are dependent on the duration and magnitude of NR2B-NMDA receptor stimulation and STEP serves as a modulator of NMDA receptor dependent neuronal injury, through its regulation of p38 MAPK. PMID:21029094

  1. Decreasing nicotinic receptor activity and the spatial learning impairment caused by the NMDA glutamate antagonist dizocilpine in rats

    PubMed Central

    Burke, Dennis A.; Heshmati, Pooneh; Kholdebarin, Ehsan; Levin, Edward D.

    2014-01-01

    Nicotinic systems have been shown by a variety of studies to be involved in cognitive function. Nicotinic receptors have an inherent property to become desensitized after activation. The relative role of nicotinic receptor activation vs. net receptor inactivation by desensitization in the cognitive effects of nicotinic drugs remains to be fully understood. In these studies, we tested the effects of the α7 nicotinic receptor antagonist methyllycaconitine (MLA), the α4β2 nicotinic receptor antagonist dihydro-β-erythroidine (DHβE), the nonspecific nicotinic channel blocker mecamylamine and the α4β2 nicotinic receptor desensitizing agent sazetidine-A on learning in a repeated acquisition test. Adult female Sprague-Dawley rats were trained on a repeated acquisition learning procedure in an 8-arm radial maze. MLA (1–4 mg/kg), DHβE (1–4 mg/kg), mecamylamine (0.125–0.5 mg/kg) or sazetidine-A (1 and 3 mg/kg) were administered in four different studies either alone or together with the NMDA glutamate antagonist dizocilpine (0.05 and 0.10 mg/kg). MLA significantly counteracted the learning impairment caused by dizocilpine. The overall choice accuracy impairment caused by dizocilpine was significantly attenuated by co-administration of DHβE. Low doses of the non-specific nicotinic antagonist mecamylamine also reduced dizocilpine-induced repeated acquisition impairment. Sazetidine-A reversed the accuracy impairment caused by dizocilpine. These studies provide evidence that a net decrease in nicotinic receptor activity can improve learning by attenuating learning impairment induced by NMDA glutamate blockade. This adds to evidence in cognitive tests that nicotinic antagonists can improve cognitive function. Further research characterizing the efficacy and mechanisms underlying nicotinic antagonist and desensitization induced cognitive improvement is warranted. PMID:25064338

  2. Glutamate Binding to the GluN2B Subunit Controls Surface Trafficking of N-Methyl-d-aspartate (NMDA) Receptors*♦

    PubMed Central

    She, Kevin; Ferreira, Joana S.; Carvalho, Ana Luisa; Craig, Ann Marie

    2012-01-01

    Trafficking of NMDA receptors to the surface of neurons and to synapses is critical for proper brain function and activity-dependent plasticity. Recent evidence suggests that surface trafficking of other ionotropic glutamate receptors requires ligand binding for exit from the endoplasmic reticulum. Here, we show that glutamate binding to GluN2 is required for trafficking of NMDA receptors to the cell surface. We expressed a panel of GluN2B ligand binding mutants in heterologous cells with GluN1 or in rat cultured neurons and found that surface expression correlates with glutamate efficacy. Such a correlation was found even in the presence of dominant negative dynamin to inhibit endocytosis and surface expression correlated with Golgi localization, indicating differences in forward trafficking. Co-expression of wild type GluN2B did not enhance surface expression of the mutants, suggesting that glutamate must bind to both GluN2 subunits in a tetramer and that surface expression is limited by the least avid of the two glutamate binding sites. Surface trafficking of a constitutively closed cleft GluN2B was indistinguishable from that of wild type, suggesting that glutamate concentrations are typically not limiting for forward trafficking. YFP-GluN2B expressed in hippocampal neurons from GluN2B−/− mice rescued synaptic accumulation at similar levels to wild type. Under these conditions, surface synaptic accumulation of YFP-GluN2B mutants also correlated with apparent glutamate affinity. Altogether, these results indicate that glutamate controls forward trafficking of NMDA receptors to the cell surface and to synapses and raise the intriguing idea that NMDA receptors may be functional at intracellular sites. PMID:22740692

  3. Stimulation of glutamate receptors in cultured hippocampal neurons causes Ca2+-dependent mitochondrial contraction

    PubMed Central

    Brustovetsky, Tatiana; Li, Viacheslav; Brustovetsky, Nickolay

    2009-01-01

    Cultured hippocampal neurons expressing mitochondrially targeted enhanced yellow fluorescent protein (mito-eYFP) were used to quantitatively examine mitochondrial remodeling in response to excitotoxic glutamate. Mitochondrial morphology was evaluated using laser spinning-disk confocal microscopy followed by calibrated image processing and 3D image rendering. Glutamate triggered an increase in cytosolic Ca2+ and mitochondrial depolarization accompanied by Ca2+-dependent morphological transformation of neuronal mitochondria from “thread-like” to rounded structures. The quantitative analysis of the mitochondrial remodeling revealed that exposure to glutamate resulted in a decrease in mitochondrial volume and surface area concurrent with an increase in sphericity of the organelles. NIM811, an inhibitor of the mitochondrial permeability transition, attenuated the glutamate-induced sustained increase in cytosolic Ca2+ and suppressed mitochondrial remodeling in the majority of affected neurons, but it did not rescue mitochondrial membrane potential. Shortening, fragmentation, and formation of circular mitochondria with decreased volume and surface area accompanied mitochondrial depolarization with FCCP. However, FCCP-induced morphological alterations appeared to be distinctly different from mitochondrial remodeling caused by glutamate. Moreover, FCCP prevented glutamate-induced mitochondrial remodeling suggesting an important role of Ca2+ influx into mitochondria in the morphological alterations. Consistent with this, in saponin-permeabilized neurons, Ca2+ caused mitochondrial remodeling which could be prevented by Ru360. PMID:19409612

  4. Habituation deficits induced by metabotropic glutamate receptors 2/3 receptor blockade in mice: reversal by antipsychotic drugs.

    PubMed

    Bespalov, Anton; Jongen-Rêlo, Ana-Lucia; van Gaalen, Marcel; Harich, Silke; Schoemaker, Hans; Gross, Gerhard

    2007-02-01

    Cortical metabotropic glutamate receptors (mGluRs) seem to be involved in habituation of simple stimulus-bound behaviors (e.g., habituation to acoustic startle or odor-elicited orienting response). Habituation deficits may contribute to the cognitive symptoms of schizophrenia. In the present study, male NMRI mice were injected with mGluR2/3 antagonist 2S-2-amino-2-(1S,2S-2-carboxycyclopropyl-1-yl)-3-(xanth-9-yl)propanoic acid (LY-341495) 30 min before being placed into novel arenas for automatic motor activity recording (2-h sessions). Administration of LY-341495 (1-10 mg/kg s.c.) dose-dependently prevented the habituation of the locomotor activity. Effects of LY-341495 (10 mg/kg) were fully and dose-dependently reversed by i.p. administration of haloperidol (0.03-0.3 mg/kg), clozapine (1-10 mg/kg), risperidone (0.01-0.1 mg/kg), olanzapine (0.3-3 mg/kg), aripiprazole (1-10 mg/kg), and sulpiride (3-30 mg/kg), each of which was given 15 min before the test. Effects of antipsychotic drugs were observed at the dose levels that did not affect spontaneous motor activity. LY-341495-induced delayed hyperactivity was also partially attenuated by lithium (50-200 mg/kg), amisulpride (1-10 mg/kg), and the selective dopamine D3 antagonist trans-N-[4-[2-(6-cyano-1,2,3,4-tetrahydroisoquinolin-2-yl)ethyl]cyclohexyl]-4-quinolinecarboxamide (SB-277011A; 3-30 mg/kg). Application of diazepam, imipramine, or several agonists and/or antagonists acting at various receptors that are thought to be relevant for antipsychotic treatment [e.g., 5-hydroxytryptamine (5-HT)(2A), 5-HT(3), and 5-HT(6) antagonists; 5-HT(1A) agonist; D4 antagonist; CB1 antagonist; ampakines; and glycine transporter inhibitor) had no appreciable effects. Thus, behavioral deficits induced by mGluR2/3 blockade (such as delayed motor hyperactivity) are selectively reversed by clinically used antipsychotic drugs.

  5. Dihydrothiazolopyridone Derivatives as a Novel Family of Positive Allosteric Modulators of the Metabotropic Glutamate 5 (mGlu5) Receptor

    PubMed Central

    Bartolomé-Nebreda, José Manuel; Conde-Ceide, Susana; Delgado, Francisca; Iturrino, Laura; Pastor, Joaquín; Pena, Miguel Ángel; Trabanco, Andrés A.; Tresadern, Gary; Wassvik, Carola M.; Stauffer, Shaun R.; Jadhav, Satyawan; Gogi, Kiran; Vinson, Paige N.; Noetzel, Meredith J.; Days, Emily; Weaver, C. David; Lindsley, Craig W.; Niswender, Colleen M.; Jones, Carrie K.; Conn, P. Jeffrey; Rombouts, Frederik; Lavreysen, Hilde; Macdonald, Gregor J.; Mackie, Claire; Steckler, Thomas

    2014-01-01

    Starting from a singleton chromanone high throughput screening (HTS) hit, we describe a focused medicinal chemistry optimization effort leading to the identification of a novel series of phenoxymethyl-dihydrothiazolopyridone derivatives as selective positive allosteric modulators (PAMs) of the metabotropic glutamate 5 (mGlu5) receptor. These dihydrothiazolopyridones potentiate receptor responses in recombinant systems. In vitro and in vivo drug metabolism and pharmacokinetic (DMPK) evaluation allowed us to select compound 16a for its assessment in a preclinical animal screen of possible antipsychotic activity. 16a was able to reverse amphetamine-induced hyperlocomotion in rats in a dose-dependent manner without showing any significant motor impairment or overt neurological side effects at comparable doses. Evolution of our medicinal chemistry program, structure activity, and properties relationships (SAR and SPR) analysis as well as a detailed profile for optimized mGlu5 receptor PAM 16a are described. PMID:23947773

  6. Metabotropic glutamate receptors, transmitter output and fatty acids: studies in rat brain slices.

    PubMed Central

    Lombardi, G.; Leonardi, P.; Moroni, F.

    1996-01-01

    1. The effects of (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD), a non-selective agonist of the metabotropic glutamate receptors (mGluRs), have been studied in rat cortical and striatal slices by measuring the depolarization-induced output of D-[3H]-aspartate (D-[3H]-Asp) and of [3H]-glutamate ([3H]-Glu), neosynthesized from [3H]-glutamine. 2. In cortical slices, 1S,3R-ACPD potentiated the depolarization-induced (KCl, 30 mM) output of both D-[3H]-Asp and [3H]-Glu. The potentiation, obtained at 300 microM 1S,3R-ACPD was 65 +/- 6% for D-[3H]-Asp and 56 +/- 10% for [3H]-Glu. Conversely, in striatal slices, 1S,3R-ACPD reduced the depolarization-induced transmitter output. The reduction, obtained at 300 microM of the agonist, was 60 +/- 8% for D-[3H]-Asp and 50 +/- 5% for neosynthesized [3H]-Glu. 3. Bovine serum albumin (BSA, 15 microM), which is able to bind locally produced fatty acids, completely eliminated the potentiating effect 1S,3R-ACPD had on D-[3H]-Asp output from cortical slices. Low concentrations of arachidonic acid (1-10 microM) or of oleic acid (1-10 microM) added to BSA-containing perfusion medium, restored this potentiating effect. BSA, however, had no effect on the inhibitory action of 1S,3R-ACPD in striatal slices. 4. Bromophenacyl bromide (100 microM), an inhibitor of phospholipase A2, and RG80267 (100 microM), an inhibitor of diacylglycerol lipase, have been shown to inhibit fatty acid production. These compounds prevented the potentiating effect of 1S,3R-ACPD on D-[3H]-Asp-output in cortical slices. 5. Indomethacin (100 microM), an inhibitor of cyclo-oxygenases, plus nordihydroguaiaretic acid (100 microM), an inhibitor of lipoxygenases, increased D-[3H]-Asp output in cortical slices perfused with BSA-containing medium. 6. These experiments suggest that the mGluR-mediated potentiation of transmitter output requires the availability of unsaturated fatty acids, such as arachidonic or oleic acids, in cortical slices. In contrast, the m

  7. Contribution of NMDA and non-NMDA receptors to in vivo glutamate-induced calpain activation in the rat striatum. Relation to neuronal damage.

    PubMed

    Del Río, Perla; Montiel, Teresa; Massieu, Lourdes

    2008-08-01

    Glutamate, the major excitatory neurotransmitter, can cause the death of neurons by a mechanism known as excitotoxicity. This is a calcium-dependent process and activation of the NMDA receptor subtype contributes mainly to neuronal damage, due to its high permeability to calcium. Activation of calpain, a calcium-dependent cysteine protease, has been implicated in necrotic excitotoxic neuronal death. We have investigated the contribution of NMDA and non-NMDA ionotropic receptors to calpain activation and neuronal death induced by the acute administration of glutamate into the rat striatum. Calpain activity was assessed by the cleavage of the cytoskeletal protein, alpha-spectrin. Caspase-3 activity was also studied because glutamate can also lead to apoptosis. Results show no caspase-3 activity, but a strong calpain activation involving both NMDA and non-NMDA receptors. Although neuronal damage is mediated mainly by the NMDA receptor subtype, it can not be attributed solely to calpain activity.

  8. Neuroprotective effects of R,R-tetrahydrochrysene against glutamate-induced cell death through anti-excitotoxic and antioxidant actions involving estrogen receptor-dependent and -independent pathways.

    PubMed

    Xia, Y; Xing, J Z; Krukoff, T L

    2009-08-18

    Glutamate-induced neural cell death is mediated by excitotoxicity and oxidative stress. Treatment of glutamate toxicity with estrogen and its related compounds for neuroprotection remains controversial. In this study, we examined the effects of selective estrogen receptor (ER) ligands on glutamate toxicity and found that R,R-tetrahydrochrysene (R,R-THC), an antagonist of ERbeta and agonist of ERalpha, has neuroprotective effects against glutamate-induced death in primary rat cortical cells and mouse N29/4 hypothalamic cells. The protective effect of R,R-THC was dose-dependent and was maintained even when added several hours after the initial glutamate exposure. R,R-THC blocked glutamate-induced depletion of intracellular glutathione, increased superoxide dismutase activity, and protected cells from hydrogen peroxide-induced death. R,R-THC also prevented glutamate-induced nuclear translocation of apoptotic inducing factor and release of mitochondrial cytochrome c. The protective effect of R,R-THC was blocked by methyl-piperidino-pyrazole (MPP; an ERalpha antagonist) in glutamate-treated cortical cells, and pretreatment with MK-801 (an NMDA receptor antagonist) but not CNQX (an AMPA/kainate receptor antagonist) increased cell survival. On the other hand, MPP did not block the protective effect of R,R-THC in glutamate-treated N29/4 cells, and neither MK-801 nor CNQX conferred protection. Activation of ERalpha and/or ERbeta with 17beta-estradiol (E2), propyl-pyrazole-triol or diarylpropionitrile did not provide effective neuroprotection, and pretreatment with ICI 182,780 did not inhibit the protective effect of R,R-THC in either type of cell. These results suggest that the use of ER agonists (including E2) has limited beneficial effects when both excitotoxicity and oxidative stress occur. In contrast to agonists of ERs, R,R-THC, which possesses anti-excitotoxic and antioxidant actions via ER-dependent and -independent pathways, provides significant neuroprotection.

  9. Combination of behaviorally sub-effective doses of glutamate NMDA and dopamine D1 receptor antagonists impairs executive function.

    PubMed

    Desai, Sagar J; Allman, Brian L; Rajakumar, Nagalingam

    2017-04-14

    Impairment of executive function is a core feature of schizophrenia. Preclinical studies indicate that injections of either N-methyl d-aspartate (NMDA) or dopamine D1 receptor blockers impair executive function. Despite the prevailing notion based on postmortem findings in schizophrenia that cortical areas have marked suppression of glutamate and dopamine, recent in vivo imaging studies suggest that abnormalities of these neurotransmitters in living patients may be quite subtle. Thus, we hypothesized that modest impairments in both glutamate and dopamine function can act synergistically to cause executive dysfunction. In the present study, we investigated the effect of combined administration of "behaviorally sub-effective" doses of NMDA and dopamine D1 receptor antagonists on executive function. An operant conditioning-based set-shifting task was used to assess behavioral flexibility in rats that were systemically injected with NMDA and dopamine D1 receptor antagonists individually or in combination prior to task performance. Separate injections of the NMDA receptor antagonist, MK-801, and the dopamine D1 receptor antagonist, SCH 23390, at low doses did not impair set-shifting; however, the combined administration of these same behaviorally sub-effective doses of the antagonists significantly impaired the performance during set-shifting without affecting learning, retrieval of the memory of the initial rule, latency of responses or the number of omissions. The combined treatment also produced an increased number of perseverative errors. Our results indicate that NMDA and D1 receptor blockade act synergistically to cause behavioral inflexibility, and as such, subtle abnormalities in glutamatergic and dopaminergic systems may act cooperatively to cause deficits in executive function.

  10. Short-term sleep deprivation impairs spatial working memory and modulates expression levels of ionotropic glutamate receptor subunits in hippocampus.

    PubMed

    Xie, Meilan; Yan, Jie; He, Chao; Yang, Li; Tan, Gang; Li, Chao; Hu, Zhian; Wang, Jiali

    2015-06-01

    Hippocampus-dependent learning memory is sensitive to sleep deprivation (SD). Although the ionotropic glutamate receptors play a vital role in synaptic plasticity and learning and memory, however, whether the expression of these receptor subunits is modulated by sleep loss remains unclear. In the present study, western blotting was performed by probing with specific antibodies against the ionotropic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunits GluA1, GluA2, GluA3, and against the N-methyl-d-aspartate (NMDA) glutamate receptor subunits GluN1, GluN2A, GluN2B. In hippocampus, down regulation of surface GluA1 and GluN2A surface expression were observed in both SD groups. However, surface expression level of GluA2, GluA3, GluN1 and GluN2B was significantly up-regulated in 8h-SD rats when compared to the 4h-SD rats. In parallel with the complex changes in AMPA and NMDA receptor subunit expressions, we found the 8h-SD impaired rat spatial working memory in 30-s-delay T-maze task, whereas no impairment of spatial learning was observed in 4h-SD rats. These results indicate that sleep loss alters the relative expression levels of the AMPA and NMDA receptors, thus affects the synaptic strength and capacity for plasticity and partially contributes to spatial memory impairment.

  11. Role of ionotropic glutamate receptors in long-term potentiation in rat hippocampal CA1 oriens-lacunosum moleculare interneurons.

    PubMed

    Oren, Iris; Nissen, Wiebke; Kullmann, Dimitri M; Somogyi, Peter; Lamsa, Karri P

    2009-01-28

    Some interneurons of the hippocampus exhibit NMDA receptor-independent long-term potentiation (LTP) that is induced by presynaptic glutamate release when the postsynaptic membrane potential is hyperpolarized. This "anti-Hebbian" form of LTP is prevented by postsynaptic depolarization or by blocking AMPA and kainate receptors. Although both AMPA and kainate receptors are expressed in hippocampal interneurons, their relative roles in anti-Hebbian LTP are not known. Because interneuron diversity potentially conceals simple rules underlying different forms of plasticity, we focus on glutamatergic synapses onto a subset of interneurons with dendrites in stratum oriens and a main ascending axon that projects to stratum lacunosum moleculare, the oriens-lacunosum moleculare (O-LM) cells. We show that anti-Hebbian LTP in O-LM interneurons has consistent induction and expression properties, and is prevented by selective inhibition of AMPA receptors. The majority of the ionotropic glutamatergic synaptic current in these cells is mediated by inwardly rectifying Ca(2+)-permeable AMPA receptors. Although GluR5-containing kainate receptors contribute to synaptic currents at high stimulus frequency, they are not required for LTP induction. Glutamatergic synapses on O-LM cells thus behave in a homogeneous manner and exhibit LTP dependent on Ca(2+)-permeable AMPA receptors.

  12. Glutamate requires NMDA receptors to modulate alpha2 adrenoceptor in medulla oblongata cultured cells of newborn rats.

    PubMed

    Marinho da Silva, Sergio; Carrettiero, Daniel C; Chadi, Débora R F

    2014-04-03

    α2 Adrenoceptors (α2-ARs) are important in regulating the central control of blood pressure in medulla oblongata. However, it is unclear how this receptor is modulated by different receptors, especially the glutamatergic. In the present study, we studied the influence of ionotropic glutamatergic receptors over the α2-ARs in cultured cells of the medulla oblongata of newborn rats. For this purpose, the protein level of the α2-ARs was assessed after administration to the cultured cells of glutamate (glu), the agonists NMDA and kainate (KA), the NMDA receptor antagonist MK801 and the KA receptor antagonist DNQX. Results indicate that the α2-AR protein levels were increased after the treatments with glu and NMDA, and the addition of MK801 to this treatment thwarted this increase. Notwithstanding the fact that KA did not alter the receptor protein level, the combined treatment of DNQX with glu prevented the α2-AR protein modulation. In conclusion, the present study suggests that ionotropic glutamatergic receptors could be related to the α2-AR protein regulation in the medulla oblongata.

  13. Type-1, but Not Type-5, Metabotropic Glutamate Receptors are Coupled to Polyphosphoinositide Hydrolysis in the Retina.

    PubMed

    Romano, Maria Rosaria; Di Menna, Luisa; Scarselli, Pamela; Mascio, Giada; Madonna, Michele; Notartomaso, Serena; Puliti, Aldamaria; Bruno, Valeria; Battaglia, Giuseppe; Nicoletti, Ferdinando

    2016-04-01

    mGlu1 and mGlu5 metabotropic glutamate receptors are expressed in the vertebrate retina, and are co-localized in some retinal neurons. It is believed that both receptors are coupled to polyphosphoinositide (PI) hydrolysis in the retina and their function may diverge in some cells because of a differential engagement of downstream signaling molecules. Here, we show that it is only the mGlu1 receptor that is coupled to PI hydrolysis in the retina. We used either bovine retinal slices or intact mouse retinas challenged with the mixed mGlu1/5 receptor agonist, DHPG. In both models, DHPG-stimulated PI hydrolysis was abrogated by the selective mGlu1 receptor antagonist, JNJ16259685, but was insensitive to the mGlu5 receptor antagonist, MPEP. In addition, the PI response to DHPG was unchanged in the retina of mGlu5(-/-) mice but was abolished in the retina of crv4 mice lacking mGlu1 receptors. Stimulation of the mitogen-activated protein kinase pathway by DHPG in intact mouse retinas were also entirely mediated by mGlu1 receptors. Our data provide the first example of a tissue in which a biochemically detectable PI response is mediated by mGlu1, but not mGlu5, receptors. Hence, bovine retinal slices might be used as a model for the functional screening of mGlu1 receptor ligands. In addition, the mGlu1 receptor caters the potential as a drug target in the experimental treatment of degenerative disorders of the retina.

  14. The conversion of glutamate by glutamine synthase in neocortical astrocytes from juvenile rat is important to limit glutamate spillover and peri/extrasynaptic activation of NMDA receptors.

    PubMed

    Trabelsi, Yosra; Amri, Mohamed; Becq, Hélène; Molinari, Florence; Aniksztejn, Laurent

    2017-02-01

    Glutamate transporters (EAATs) are important to maintain spatial and temporal specificity of synaptic transmission. Their efficiency to uptake and transport glutamate into the intracellular space depends on several parameters including the intracellular concentrations of Na(+) and glutamate, the elevations of which may slow down the cycling rate of EAATs. In astrocytes, glutamate is maintained at low concentration due to the presence of specific enzymes such as glutamine synthase (GS). GS inhibition results in cytosolic accumulation of glutamate suggesting that the conversion of glutamate by GS is important for EAATs operation. Here we recorded astrocytes from juvenile rat neocortical slices and analyzed the consequences of elevated intracellular glutamate concentrations and of GS inhibition on the time course of synaptically evoked transporter current (STC). In slices from rats treated with methionine sulfoximine (MSO), a GS inhibitor, STC evoked by short burst of high frequency stimulation (HFS; 100 Hz for 100 ms) but not by low frequency stimulation (LFS; 0.1 Hz) was twice slower than STC evoked from saline injected rats. Same results were obtained for astrocytes recorded with pipette containing 3-10 mM glutamate and compared with cells recorded with 0 or1 mM glutamate in the patch pipette. We also showed that HFS elicited significantly larger NMDAR-excitatory postsynaptic currents (EPSCs) with a stronger peri/extrasynaptic component in pyramidal cells from MSO-treated compared with saline treated rats. Taken together our data demonstrate that the conversion of glutamate by GS is fundamental to ensure an efficient clearance of glutamate by EAATs and to prevent glutamate spillover. GLIA 2017;65:401-415.

  15. Arctigenin reduces neuronal responses in the somatosensory cortex via the inhibition of non-NMDA glutamate receptors.

    PubMed

    Borbély, Sándor; Jócsák, Gergely; Moldován, Kinga; Sedlák, Éva; Preininger, Éva; Boldizsár, Imre; Tóth, Attila; Atlason, Palmi T; Molnár, Elek; Világi, Ildikó

    2016-07-01

    Lignans are biologically active phenolic compounds related to lignin, produced in different plants. Arctigenin, a dibenzylbutyrolactone-type lignan, has been used as a neuroprotective agent for the treatment of encephalitis. Previous studies of cultured rat cerebral cortical neurones raised the possibility that arctigenin inhibits kainate-induced excitotoxicity. The aims of the present study were: 1) to analyse the effect of arctigenin on normal synaptic activity in ex vivo brain slices, 2) to determine its receptor binding properties and test the effect of arctigenin on AMPA/kainate receptor activation and 3) to establish its effects on neuronal activity in vivo. Arctigenin inhibited glutamatergic transmission and reduced the evoked field responses. The inhibitory effect of arctigenin on the evoked field responses proved to be substantially dose dependent. Our results indicate that arctigenin exerts its effects under physiological conditions and not only on hyper-excited neurons. Furthermore, arctigenin can cross the blood-brain barrier and in the brain it interacts with kainate sensitive ionotropic glutamate receptors. These results indicate that arctigenin is a potentially useful new pharmacological tool for the inhibition of glutamate-evoked responses in the central nervous system in vivo.

  16. Growth hormone (GH) increases cognition and expression of ionotropic glutamate receptors (AMPA and NMDA) in transgenic zebrafish (Danio rerio).

    PubMed

    Studzinski, Ana Lupe Motta; Barros, Daniela Martí; Marins, Luis Fernando

    2015-11-01

    The growth hormone/insulin-like factor I (GH/IGF-I) somatotropic axis is responsible for somatic growth in vertebrates, and has important functions in the nervous system. Among these, learning and memory functions related to the neural expression of ionotropic glutamate receptors, mainly types AMPA (α-amino-3hydroxy-5methylisoxazole-4propionic) and NMDA (N-methyl-d-aspartate) can be highlighted. Studies on these mechanisms have been almost exclusively conducted on mammal models, with little information available on fish. Consequently, this study aimed at evaluating the effects of the somatotropic axis on learning and memory of a GH-transgenic zebrafish (Danio rerio) model (F0104 strain). Long-term memory (LTM) was tested in an inhibitory avoidance apparatus, and brain expression of igf-I and genes that code for the main subunits of the AMPA and NMDA receptors were evaluated. Results showed a significant increase in LTM for transgenic fish. Transgenic animals also showed a generalized pattern of increase in the expression of AMPA and NMDA genes, as well as a three-fold induction in igf-I expression in the brain. When analyzed together, these results indicate that GH, mediated by IGF-I, has important effects on the brain, with improvement in LTM as a result of increased glutamate receptors. The transgenic strain F0104 was shown to be an interesting model for elucidating the intricate mechanisms related to the effect of the somatotropic axis on learning and memory in vertebrates.

  17. The Role of Ionotropic Glutamate Receptors in Childhood Neurodevelopmental Disorders: Autism Spectrum Disorders and Fragile X Syndrome

    PubMed Central

    Uzunova, Genoveva; Hollander, Eric; Shepherd, Jason

    2014-01-01

    Autism spectrum disorder (ASD) and Fragile X syndrome (FXS) are relatively common childhood neurodevelopmental disorders with increasing incidence in recent years. They are currently accepted as disorders of the synapse with alterations in different forms of synaptic communication and neuronal network connectivity. The major excitatory neurotransmitter system in brain, the glutamatergic system, is implicated in learning and memory, synaptic plasticity, neuronal development. While much attention is attributed to the role of metabotropic glutamate receptors in ASD and FXS, studies indicate that the ionotropic glutamate receptors (iGluRs) and their regulatory proteins are also altered in several brain regions. Role of iGluRs in the neurobiology of ASD and FXS is supported by a weight of evidence that ranges from human genetics to in vitro cultured neurons. In this review we will discuss clinical, molecular, cellular and functional changes in NMDA, AMPA and kainate receptors and the synaptic proteins that regulate them in the context of ASD and FXS. We will also discuss the significance for the development of translational biomarkers and treatments for the core symptoms of ASD and FXS. PMID:24533017

  18. Persistent current oscillations produced by activation of metabotropic glutamate receptors in immature rat CA3 hippocampal neurons.

    PubMed

    Aniksztejn, L; Sciancalepore, M; Ben Ari, Y; Cherubini, E

    1995-04-01

    1. The single-electrode voltage-clamp technique was used to study the effects of the metabotropic glutamate receptors (mGluRs) agonist 1S,3R-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD, ACPD, 3-10 microM) on CA3 hippocampal neurons during the 1st 10 days of postnatal (P) life and in adulthood. 2. Repeated applications of 1S,3R-ACPD, in the presence of tetrodotoxin (TTX, 1 microM), tetraethylammonium chloride (TEACl 10 mM), and CsCl (2 mM), induced in immature but not in adult neurons periodic inward currents (PICs) that persisted for several hours after the last application of the agonist. 3. PICs, which were generated by nonspecific cationic currents, reversed polarity at 2.8 +/- 3 (SD) mV. They were reversibly blocked by kynurenic acid (1 mM), suggesting that they were mediated by glutamate acting on ionotropic receptors. They were also abolished in a nominally Ca(2+)-free medium. 4. PICs were irreversibly abolished by thapsigargin (10 microM) but were unaffected by ryanodine (10-40 microM). Caffeine (2 mM) also reversibly blocked PICs; this effect was independent from adenosine 3',5'-cyclic monophosphate (cAMP) accumulation, inhibition of voltage-dependent Ca2+ current, or blockade of adenosine receptors. 5. We suggest that, in neonatal slices, mGluRs-induced PICs are triggered by elevation of [Ca2+]i, after mobilization of Ca2+ from inositol 1,4,5-trisphosphate (InsP3)-sensitive stores. This will lead to a persistent, pulsatile release of glutamate from presynaptic nerve terminals, a phenomenon that is probably maintained via a calcium-induced-calcium release process.

  19. Neuroprotective role of Bacopa monnieri extract in epilepsy and effect of glucose supplementation during hypoxia: glutamate receptor gene expression.

    PubMed

    Paulose, C S; Chathu, Finla; Khan, S Reas; Krishnakumar, Amee

    2008-09-01

    The experiments were designed to study the glutamate gene expression during epilepsy in adult and hypoxic insult to brain during the neonatal period and the therapeutic role of neuroprotective supplements. We investigated the role of metabotropic glutamate-8 receptor (mGluR8) gene expression in cerebellum during epilepsy and neuroprotective role of Bacopa monnieri extract in epilepsy. We also studied the effect of NMDA receptor 1 (NMDAR1) gene expression during neonatal hypoxia and therapeutic role of glucose, oxygen and epinephrine supplementation. During epilepsy a significant down-regulation (P < 0.01) of mGluR8 gene expression was observed which was up-regulated (P < 0.05) near control level after B. monnieri treatment which is supported by Morris water maze experiment. In hypoxic neonates we observed up-regulation (P < 0.001) of the NMDAR1 gene expression whereas glucose and glucose + oxygen was able to significantly reverse (P < 0.001) the gene expression to near control level when compared to hypoxia and epinephrine treatment which was supported by open field test. Our results showed that B. monnieri treatment to epileptic rats significantly brought the reversal of the down-regulated mgluR8 gene expression toward control level. In neonatal rats, hypoxia induced expressional and functional changes in the NMDAR1 receptors of neuronal cells which is corrected by supplementation of glucose alone or glucose followed by oxygen during the resuscitation to prevent the glutamate related neuronal damage. Thus, the results suggest the clinical significance of corrective measures for epileptic and hypoxic management.

  20. Motor Alterations Induced by Chronic 4-Aminopyridine Infusion in the Spinal Cord In vivo: Role of Glutamate and GABA Receptors

    PubMed Central

    Lazo-Gómez, Rafael; Tapia, Ricardo

    2016-01-01

    Motor neuron (MN) degeneration is the pathological hallmark of MN diseases, a group of neurodegenerative disorders clinically manifested as muscle fasciculations and hyperreflexia, followed by paralysis, respiratory failure, and death. Ample evidence supports a role of glutamate-mediated excitotoxicity in motor death. In previous work we showed that stimulation of glutamate release from nerve endings by perfusion of the K+-channel blocker 4-aminopyridine (4-AP) in the rat hippocampus induces seizures and neurodegeneration, and that AMPA infusion in the spinal cord produces paralysis and MN death. On these bases, in this work we have tested the effect of the chronic infusion of 4-AP in the spinal cord, using implanted osmotic minipumps, on motor activity and on MN survival, and the mechanisms underlying this effect. 4-AP produced muscle fasciculations and motor deficits assessed in two motor tests, which start 2–3 h after the implant, which ameliorated spontaneously within 6–7 days, but no neurodegeneration. These effects were prevented by both AMPA and NMDA receptors blockers. The role of GABAA receptors was also explored, and we found that chronic infusion of bicuculline induced moderate MN degeneration and enhanced the hyperexcitation produced by 4-AP. Unexpectedly, the GABAAR agonist muscimol also induced motor deficits and failed to prevent the MN death induced by AMPA. We conclude that motor alterations induced by chronic 4-AP infusion in the spinal cord in vivo is due to ionotropic glutamate receptor overactivation and that blockade of GABAergic neurotransmission induces MN death under chronic conditions. These results shed light on the role of glutamatergic and GABAergic neurotransmission in the regulation of MN excitability in the spinal cord. PMID:27242406

  1. Intrathecal injection of glutamate receptor antagonists/agonist selectively attenuated rat pain-related behaviors induced by the venom of scorpion Buthus martensi Karsch.

    PubMed

    Liu, Tong; Pang, Xue-Yan; Bai, Zhan-Tao; Chai, Zhi-Fang; Jiang, Feng; Ji, Yong-Hua

    2007-12-15

    The present study investigated the involvement of spinal glutamate receptors in the induction and maintenance of the pain-related behaviors induced by the venom of scorpion Buthus martensi Karsch (BmK). (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5-10-imine hydrogen maleate (MK-801; 40nmol; a non-competitive NMDA receptor antagonist), 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 40nmol; a non-NMDA receptor antagonist), dl-amino-3-phosphonopropionic acid (dl-AP3; 100nmol; a group I metabotropic glutamate receptor antagonist) and 4-aminopyrrolidine-2,4-dicarboxylate (APDC; 100nmol; a group II metabotropic glutamate receptor agonist) were employed. On intrathecal injection of glutamate receptor antagonists/agonist before BmK venom administration by 10min, BmK venom-induced spontaneous nociceptive responses could be suppressed by all tested agents. Primary thermal hyperalgesia could be inhibited by MK-801 and dl-AP3, while bilateral mechanical hyperalgesia could be inhibited by CNQX and dl-AP3 and contralateral mechanical hyperalgesia could be inhibited by APDC. On intrathecal injection of glutamate receptor antagonists/agonist after BmK venom injection by 4.5h, primary thermal hyperalgesia could be partially reversed by all tested agents, while bilateral mechanical hyperalgesia could only be inhibited by APDC. The results suggest that the role of spinal glutamate receptors may be different on the various manifestations of BmK venom-induced pain-related behaviors.

  2. Ligand Bias at Metabotropic Glutamate 1a Receptors: Molecular Determinants That Distinguish β-Arrestin-Mediated from G Protein-Mediated Signaling

    PubMed Central

    Emery, Andrew C.; DiRaddo, John O.; Miller, Eric; Hathaway, Hannah A.; Pshenichkin, Sergey; Takoudjou, Guy Rodrigue; Grajkowska, Ewa; Yasuda, Robert P.; Wolfe, Barry B.

    2012-01-01

    The metabotropic glutamate 1a (mGlu1a) receptor is a G protein-coupled receptor linked with phosphoinositide (PI) hydrolysis and with β-arrestin-1-mediated sustained extracellular signal-regulated kinase (ERK) phosphorylation and cytoprotective signaling. Previously, we reported the existence of ligand bias at this receptor, inasmuch as glutamate induced both effects, whereas quisqualate induced only PI hydrolysis. In the current study, we showed that mGlu1 receptor agonists such as glutamate, aspartate, and l-cysteate were unbiased and activated both signaling pathways, whereas quisqualate and (S)-3,5-dihydroxyphenylglycine stimulated only PI hydrolysis. Competitive antagonists inhibited only PI hydrolysis and not the β-arrestin-dependent pathway, whereas a noncompetitive mGlu1 receptor antagonist blocked both pathways. Mutational analysis of the ligand binding domain of the mGlu1a receptor revealed that Thr188 residues were essential for PI hydrolysis but not for protective signaling, whereas Arg323 and Lys409 residues were required for β-arrestin-1-mediated sustained ERK phosphorylation and cytoprotective signaling but not for PI hydrolysis. Therefore, the mechanism of ligand bias appears to involve different modes of agonist interactions with the receptor ligand binding domain. Although some mGlu1a receptor agonists are biased toward PI hydrolysis, we identified two endogenous compounds, glutaric acid and succinic acid, as new mGlu1 receptor agonists that are fully biased toward β-arrestin-mediated protective signaling. Pharmacological studies indicated that, in producing the two effects, glutamate interacted in two distinct ways with mGlu1 receptors, inasmuch as competitive mGlu1 receptor antagonists that blocked PI hydrolysis did not inhibit cytoprotective signaling. Quisqualate, which is biased toward PI hydrolysis, failed to inhibit glutamate-induced protection, and glutaric acid, which is biased toward protection, did not interfere with glutamate

  3. Antagonism of metabotropic glutamate 1 receptors attenuates behavioral effects of cocaine and methamphetamine in squirrel monkeys.

    PubMed

    Achat-Mendes, Cindy; Platt, Donna M; Spealman, Roger D

    2012-10-01

    Within the group I family of metabotropic glutamate receptors (mGluRs), substantial evidence points to a role for mGluR5 mechanisms in cocaine's abuse-related behavioral effects, but less is understood about the contribution of mGluR1, which also belongs to the group I mGluR family. The selective mGluR1 antagonist JNJ16259685 [(3,4-dihydro-2H-pyrano-[2,3-b]quinolin-7-yl)-(cis-4-methoxycyclohexyl)-methanone] was used to investigate the role of mGluR1 in the behavioral effects of cocaine and methamphetamine. In drug discrimination experiments, squirrel monkeys were trained to discriminate cocaine from saline by using a two-lever, food-reinforced operant procedure. JNJ16259685 (0.56 mg/kg) pretreatments significantly attenuated cocaine's discriminative stimulus effects and the cocaine-like discriminative stimulus effects of methamphetamine. In monkeys trained to self-administer cocaine or methamphetamine under a second-order schedule of intravenous drug injection, JNJ16259685 (0.56 mg/kg) significantly reduced drug-reinforced responding, resulting in a downward displacement of dose-response functions. In reinstatement studies, intravenous priming with cocaine accompanied by restoration of a cocaine-paired stimulus reinstated extinguished cocaine-seeking behavior, which was significantly attenuated by JNJ16259685 (0.56 mg/kg). Finally, in experiments involving food rather than drug self-administration, cocaine and methamphetamine increased the rate of responding, and the rate-increasing effects of both psychostimulants were significantly attenuated by JNJ16259685 (0.3 mg/kg). At the doses tested, JNJ16259685 did not significantly suppress food-reinforced behavior (drug discrimination or fixed-interval schedule of food delivery), but did significantly reduce species-typical locomotor activity in observational studies. To the extent that the psychostimulant-antagonist effects of JNJ16259685 are independent of motor function suppression, further research is warranted to

  4. Association between the NMDA glutamate receptor GRIN2B gene and obsessive–compulsive disorder

    PubMed Central

    Alonso, Pino; Gratacós, Mónica; Segalàs, Cinto; Escaramís, Georgia; Real, Eva; Bayés, Mónica; Labad, Javier; López-Solà, Clara; Estivill, Xavier; Menchón, José M.

    2012-01-01

    Background Recent data from neuroimaging, genetic and clinical trials and animal models suggest a role for altered glutamatergic neurotransmission in the pathogenesis of obsessive–compulsive disorder (OCD). The aim of this study was to investigate whether variants in the GRIN2B gene, the gene encoding the NR2 subunit of the N-methyl-d-aspartate (NMDA) glutamate receptor, may contribute to genetic susceptibility to OCD or to different OCD subphenotypes. Methods Between 2003 and 2008, we performed a case–control association study in which we genotyped 10 tag single-nucleotide polymorphisms (SNPs) in the 3′ untranslated region (3′ UTR) of GRIN2B. We performed SNP association and haplotype analysis considering the OCD diagnosis and different OCD subphenotypes: early-onset OCD, comorbid tic disorders and OCD clinical symptom dimensions. Results We enrolled 225 patients with OCD and 279 controls recruited from the OCD Clinic at Bellvitge Hospital (Barcelona, Spain). No significant difference in the distribution of alleles or genotypes was detected between patients with OCD and controls. Nonetheless, on analyzing OCD subphenotypes, the rs1805476 SNP in male patients (95% confidence interval [CI] 1.37–4.22, p = 0.002) and a 4-SNP haplotype in the whole sample (rs1805476, rs1805501, rs1805502 and rs1805477; odds ratio 1.92, 95% CI 1.22–3.01; permutation p = 0.023) were significantly associated with the presence of contamination obsessions and cleaning compulsions. Limitations Study limitations included the risk of population stratification associated with the case–control design, use of psychiatrically unscreened blood donors as the control group, reduced sample size of participants with certain OCD subphenotypes and tested polymorphisms limited to 3′ UTR and exon 13 of GRIN2B. Conclusion Our results converge with recent data suggesting a possible contribution of glutamatergic variants to the genetic vulnerability to OCD or at least to certain OCD

  5. Presynaptic α4β2 nicotinic acetylcholine receptors increase glutamate release and serotonin neuron excitability in the dorsal raphe nucleus.

    PubMed

    Garduño, Julieta; Galindo-Charles, Luis; Jiménez-Rodríguez, Javier; Galarraga, Elvira; Tapia, Dagoberto; Mihailescu, Stefan; Hernandez-Lopez, Salvador

    2012-10-24

    Several behavioral effects of nicotine are mediated by changes in serotonin (5-HT) release in brain areas that receive serotonergic afferents from the dorsal raphe nucleus (DRN). In vitro experiments have demonstrated that nicotine increases the firing activity in the majority of DRN 5-HT neurons and that DRN contains nicotinic acetylcholine receptors (nAChRs) located at both somata and presynaptic elements. One of the most common presynaptic effects of nicotine is to increase glutamate release. Although DRN receives profuse glutamatergic afferents, the effect of nicotine on glutamate release in the DRN has not been studied in detail. Using whole-cell recording techniques, we investigated the effects of nicotine on the glutamatergic input to 5-HT DRN neurons in rat midbrain slices. Low nicotine concentrations, in the presence of bicuculline and tetrodotoxin (TTX), increased the frequency but did not change the amplitude of glutamate-induced EPSCs, recorded from identified 5-HT neurons. Nicotine-induced increase of glutamatergic EPSC frequency persisted 10-20 min after drug withdrawal. This nicotinic effect was mimicked by exogenous administration of acetylcholine (ACh) or inhibition of ACh metabolism. In addition, the nicotine-induced increase in EPSC frequency was abolished by blockade of α4β2 nAChRs, voltage-gated calcium channels, or intracellular calcium signaling but not by α7 nAChR antagonists. These data suggest that both nicotine and endogenous ACh can increase glutamate release through activation of presynaptic α4β2 but not α7 nAChRs in the DRN. The effect involves long-term changes in synaptic function, and it is dependent on voltage-gated calcium channels and presynaptic calcium stores.

  6. Pharmacology and Structural Analysis of Ligand Binding to the Orthosteric Site of Glutamate-Like GluD2 Receptors

    PubMed Central

    Kristensen, Anders S.; Hansen, Kasper B.; Naur, Peter; Olsen, Lars; Kurtkaya, Natalie L.; Dravid, Shashank M.; Kvist, Trine; Yi, Feng; Pøhlsgaard, Jacob; Clausen, Rasmus P.; Gajhede, Michael

    2016-01-01

    The GluD2 receptor is a fundamental component of postsynaptic sites in Purkinje neurons, and is required for normal cerebellar function. GluD2 and the closely related GluD1 are classified as members of the ionotropic glutamate receptor (iGluR) superfamily on the basis of sequence similarity, but do not bind l-glutamate. The amino acid neurotransmitter D-Ser is a GluD2 receptor ligand, and endogenous D-Ser signaling through GluD2 has recently been shown to regulate endocytosis of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid–type iGluRs during synaptic plasticity in the cerebellum, such as long-term depression. Here, we investigate the pharmacology of the orthosteric binding site in GluD2 by examining the activity of analogs of D-Ser and GluN1 glycine site competitive antagonists at GluD2 receptors containing the lurcher mutation (GluD2LC), which promotes spontaneous channel activation. We identify several compounds that modulate GluD2LC, including a halogenated alanine analog as well as the kynurenic acid analog 7-chloro-4-oxo-1H-quinoline-2-carboxylic acid (7-chlorokynurenic acid; 7-CKA). By correlating thermodynamic and structural data for 7-CKA binding to the isolated GluD2 ligand binding domain (GluD2-LBD), we find that binding 7-CKA to GluD2-LBD differs from D-Ser by inducing an intermediate cleft closure of the clamshell-shaped LBD. The GluD2 ligands identified here can potentially serve as a starting point for development of GluD2-selective ligands useful as tools in studies of the signaling role of the GluD2 receptor in the brain. PMID:26661043

  7. Regulation of Glutamate Release by α7 Nicotinic Receptors: Differential Role in Methamphetamine-Induced Damage to Dopaminergic and Serotonergic Terminals

    PubMed Central

    Northrop, Nicole A.; Smith, Laura P.; Eyerman, David J.

    2011-01-01

    Regulation of glutamate release is an important underlying mechanism in mediating excitotoxic events such as damage to dopamine (DA) and serotonin (5-HT) neurons observed after exposure to methamphetamine (Meth). One way to regulate glutamate release may be through the modulation of α7 nicotinic acetylcholine (nACh) receptors. Meth administration is known to increase acetylcholine release; however, it is unknown whether Meth increases glutamate release and causes long-term damage to both DA and 5-HT terminals through the activation of α7 nACh receptors. To test this hypothesis, the α7 nACh receptor antagonist, methyllycaconitine (MLA), was administered before the administration of repeated doses of Meth while simultaneously monitoring extracellular striatal glutamate with in vivo microdialysis. In addition, the subsequent long-term decreases in markers of dopaminergic and serotonergic terminals, including DA reuptake transporter (DAT), serotonin reuptake transporter (SERT), vesicular monoamine transporter-2, vesicular DA, and vesicular 5-HT content in the rat striatum, were measured. The results show that MLA pretreatment prevented Meth-induced increases in striatal glutamate and protected against the subsequent long-term decreases in striatal DAT and vesicular DA content without affecting the hyperthermia produced by Meth. In contrast, the Meth-induced decreases in striatal SERT immunoreactivity and vesicular 5-HT content were not affected by MLA. This suggests that the α7 nACh receptor differentially mediates glutamate-dependent damage to DA but not 5-HT terminals in a manner that is independent of hyperthermia. Furthermore, antagonism of α7 nACh receptors may be a possible therapeutic strategy for decreasing extracellular glutamate and preventing the excitotoxic damage observed in other DA-related neurodegenerative disorders. PMID:21159748

  8. Receptor to glutamate NMDA-type: the functional diversity of the nr1 isoforms and pharmacological properties.

    PubMed

    Flores-Soto, Mario Eduardo; Chaparro-Huerta, Verónica; Escoto-Delgadillo, Martha; Ureña-Guerrero, Mónica Elisa; Camins, Antoni; Beas-Zarate, Carlos

    2013-01-01

    Glutamic acid (Glu) is the major excitatory neurotransmitter in the central nervous system, and interacts with two classes of receptor: metabotropic and ionotropic receptors. Ionotropic receptors are divided according to the affinity of their specific agonists: Nmethyl- D-aspartate (NMDA), amino acid-3-hydroxy-5-methyl-4-isoxazole acid (AMPA) and kainic acid (KA). NMDA receptors (NMDA-R) are macromolecular structures that are formed by different combinations of subunits: NMDAR1 (NR1), NMDAR2 (NR2) and NMDAR3 (NR3). The study of this receptor has aroused great interest, partly due to its role in synaptic plasticity but mainly because of its permeability to the Ca(2+) ion. This review examines the molecular composition of NMDA-R and the variants of NR1 subunit editing in association with NR2 subunit dimers, which form the main components of this receptor. Their composition, structure, function and distinct temporal and spatial expression patterns demonstrate the versatility and diversity of functionally different isoforms of NR1 subunits and the various pharmacological properties of the NR2 subunit. Finally, the involvement of NMDA-R in the excitotoxicity phenomenon, as well as, its expression changes under these conditions as neuronal response are also discussed.

  9. N-Methyl-d-aspartate Modulation of Nucleus Accumbens Dopamine Release by Metabotropic Glutamate Receptors: Fast Cyclic Voltammetry Studies in Rat Brain Slices in Vitro.

    PubMed

    Yavas, Ersin; Young, Andrew M J

    2017-02-15

    The N-methyl-d-aspartate (NMDA) receptor antagonist, phencyclidine, induces behavioral changes in rodents mimicking symptoms of schizophrenia, possibly mediated through dysregulation of glutamatergic control of mesolimbic dopamine release. We tested the hypothesis that NMDA receptor activation modulates accumbens dopamine release, and that phencyclidine pretreatment altered this modulation. NMDA caused a receptor-specific, dose-dependent decrease in electrically stimulated dopamine release in nucleus accumbens brain slices. This decrease was unaffected by picrotoxin, making it unlikely to be mediated through GABAergic neurones, but was decreased by the metabotropic glutamate receptor antagonist, (RS)-α-methyl-4-sulfonophenylglycine, indicating that NMDA activates mechanisms controlled by these receptors to decrease stimulated dopamine release. The effect of NMDA was unchanged by in vivo pretreatment with phencyclidine (twice daily for 5 days), with a washout period of at least 7 days before experimentation, which supports the hypothesis that there is no enduring direct effect of PCP at NMDA receptors after this pretreatment procedure. We propose that NMDA depression of accumbal dopamine release is mediated by metabotropic glutamate receptors located pre- or perisynaptically, and suggest that NMDA evoked increased extrasynaptic spillover of glutamate is sufficient to activate these receptors that, in turn, inhibit dopamine release. Furthermore, we suggest that enduring functional changes brought about by subchronic phencyclidine pretreatment, modeling deficits in schizophrenia, are downstream effects consequent on chronic blockade of NMDA receptors, rather than direct effects on NMDA receptors themselves.

  10. Ameliorative effect of a hippocampal metabotropic glutamate- receptor agonist on histamine H1 receptor antagonist-induced memory deficit in rats.

    PubMed

    Masuoka, Takayoshi; Mikami, Azusa; Kamei, Chiaki

    2010-01-01

    This study was performed to investigate the ameliorative effects of metabotropic glutamate (mGlu)-receptor agonists on histamine H(1) receptor antagonist-induced spatial memory deficit and the decrease in hippocampal theta activity in rats. Intraperitoneal injection of pyrilamine (35 mg/kg) resulted in impaired reference and working memory in the radial maze task and decreased hippocampal theta amplitude and power. The working memory deficit and decreased hippocampal theta power induced by pyrilamine were ameliorated by intrahippocampal injection of (RS)-3,5-dihydroxyphenylglycine (DHPG) (1 and 10 microg/side), a group I mGlu-receptor agonist; however, intrahippocampal injection of (2R,4R)-4-aminopyrrolidine-2,4-dicarboxylate (APDC), a group II mGlu-receptor agonist, and L-(+)-2-amino-4-phosphonobutyric acid (L-AP4), a group III mGlu-receptor agonist, showed no significant effect on the pyrilamine-induced memory deficit and decreased hippocampal theta activity. These results indicate that the activation of hippocampal group I mGlu receptors, but not group II and III mGlu receptors, improve the histamine H(1) receptor antagonist-induced working memory deficit and decreased hippocampal theta activity.

  11. Distinct subsynaptic localization of type 1 metabotropic glutamate receptors at glutamatergic and GABAergic synapses in the rodent cerebellar cortex.

    PubMed

    Mansouri, Mahnaz; Kasugai, Yu; Fukazawa, Yugo; Bertaso, Federica; Raynaud, Fabrice; Perroy, Julie; Fagni, Laurent; Kaufmann, Walter A; Watanabe, Masahiko; Shigemoto, Ryuichi; Ferraguti, Francesco

    2015-01-01

    Type 1 metabotropic glutamate (mGlu1) receptors play a pivotal role in different forms of synaptic plasticity in the cerebellar cortex, e.g. long-term depression at glutamatergic synapses and rebound potentiation at GABAergic synapses. These various forms of plasticity might depend on the subsynaptic arrangement of the receptor in Purkinje cells that can be regulated by protein-protein interactions. This study investigated, by means of the freeze-fracture replica immunogold labelling method, the subcellular localization of mGlu1 receptors in the rodent cerebellum and whether Homer proteins regulate their subsynaptic distribution. We observed a widespread extrasynaptic localization of mGlu1 receptors and confirmed their peri-synaptic enrichment at glutamatergic synapses. Conversely, we detected mGlu1 receptors within the main body of GABAergic synapses onto Purkinje cell dendrites. Although Homer proteins are known to interact with the mGlu1 receptor C-terminus, we could not detect Homer3, the most abundant Homer protein in the cerebellar cortex, at GABAergic synapses by pre-embedding and post-embedding immunoelectron microscopy. We then hypothesized a critical role for Homer proteins in the peri-junctional localization of mGlu1 receptors at glutamatergic synapses. To disrupt Homer-associated protein complexes, mice were tail-vein injected with the membrane-permeable dominant-negative TAT-Homer1a. Freeze-fracture replica immunogold labelling analysis showed no significant alteration in the mGlu1 receptor distribution pattern at parallel fibre-Purkinje cell synapses, suggesting that other scaffolding proteins are involved in the peri-synaptic confinement. The identification of interactors that regulate the subsynaptic localization of the mGlu1 receptor at neurochemically distinct synapses may offer new insight into its trafficking and intracellular signalling.

  12. Glutamate receptor antagonism in inferior colliculus attenuates elevated startle response of high anxiety diazepam-withdrawn rats.

    PubMed

    Cabral, A; De Ross, J; Castilho, V M; Brandão, M L; Nobre, M J

    2009-07-07

    Rats segregated according to low (LA) or high (HA) anxiety levels have been used as an important tool in the study of fear and anxiety. Since the efficacy of an anxiolytic compound is a function of the animal's basal anxiety level, it is possible that chronic treatment with a benzodiazepine (Bzp) affects LA and HA animals differently. Based on these assumptions, this study aimed to provide some additional information on the influence of acute, chronic (18 days) and withdrawal effects (48 h) from diazepam (10 mg/kg), in rats with LA or HA levels, on startle response amplitude. For this purpose, the elevated plus-maze (EPM) test was used. In addition, the role of glutamate receptors of the central nucleus of the inferior colliculus (cIC), the most important mesencephalic tectum integrative structure of the auditory pathways and a brain region that is linked to the processing of auditory information of aversive nature, was also evaluated. Our results showed that, contrary to the results obtained in LA rats, long-term treatment with diazepam promoted anxiolytic and aversive effects in HA animals that were tested under chronic effects or withdrawal from this drug, respectively. In addition, since Bzp withdrawal may function as an unconditioned stressor, the negative affective states observed in HA rats could be a by-product of GABA-glutamate imbalance in brain systems that modulate unconditioned fear and anxiety behaviors, since the blockade of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) and N-methyl-D-aspartate (NMDA) glutamate receptors in the cIC clearly reduced the aversion promoted by diazepam withdrawal.

  13. Impaired expression and function of group II metabotropic glutamate receptors in pilocarpine-treated chronically epileptic rats

    PubMed Central

    Garrido-Sanabria, Emilio R.; Otalora, Luis F. Pacheco; Arshadmansab, Massoud F.; Herrera, Berenice; Francisco, Sebastian; Ermolinsky, Boris

    2008-01-01

    Group II metabotropic (mGlu II) receptor subtypes mGlu2 and mGlu3 are important modulators of synaptic plasticity and glutamate release in the brain. Accordingly, several pharmacological ligands have been designed to target these receptors for the treatment of neurological disorders characterized by anomalous glutamate regulation including epilepsy. In this study, we examine whether the expression level and function of mGlu2 and mGlu3 are altered in experimental epilepsy by using immunohistochemistry, Western blot analysis, RT-PCR and extracellular recordings. A down-regulation of mGlu2/3 protein expression at the mossy fiber pathway was associated with a significant reduction in mGlu2/3 protein expression in the hippocampus and cortex of chronically epileptic rats. Moreover, a reduction in mGlu2 and mGlu3 transcripts levels was noticed as early as 24h after pilocarpine-induced status epilepticus (SE) and persisted during subsequent “latent” and chronic periods. In addition, a significant impairment of mGlu II-mediated depression of field excitatory postsynaptic potentials at mossy fiber-CA3 synapses was detected in chronically epileptic rats. Application of mGlu II agonists (2S,2'R,3'R)-2-(2',3'-dicarboxycyclopropyl)glycine (DCG-IV) induced a significant reduction of the fEPSP amplitude in control rats, but not in chronic epileptic rats. These data indicate a long-lasting impairment of mGlu2/3 expression that may contribute to abnormal presynaptic plasticity, exaggerate glutamate release and hyperexcitability in temporal lobe epilepsy. PMID:18804094

  14. Impaired expression and function of group II metabotropic glutamate receptors in pilocarpine-treated chronically epileptic rats.

    PubMed

    Garrido-Sanabria, Emilio R; Otalora, Luis F Pacheco; Arshadmansab, Massoud F; Herrera, Berenice; Francisco, Sebastian; Ermolinsky, Boris S

    2008-11-13

    Group II metabotropic (mGlu II) receptor subtypes mGlu2 and mGlu3 are important modulators of synaptic plasticity and glutamate release in the brain. Accordingly, several pharmacological ligands have been designed to target these receptors for the treatment of neurological disorders characterized by anomalous glutamate regulation including epilepsy. In this study, we examine whether the expression level and function of mGlu2 and mGlu3 are altered in experimental epilepsy by using immunohistochemistry, Western blot analysis, RT-PCR and extracellular recordings. A down-regulation of mGlu2/3 protein expression at the mossy fiber pathway was associated with a significant reduction in mGlu2/3 protein expression in the hippocampus and cortex of chronically epileptic rats. Moreover, a reduction in mGlu2 and mGlu3 transcripts levels was noticed as early as 24 h after pilocarpine-induced status epilepticus (SE) and persisted during subsequent "latent" and chronic periods. In addition, a significant impairment of mGlu II-mediated depression of field excitatory postsynaptic potentials at mossy fiber-CA3 synapses was detected in chronically epileptic rats. Application of mGlu II agonists (2S,2'R,3'R)-2-(2',3'-dicarboxycyclopropyl)glycine (DCG-IV) induced a significant reduction of the fEPSP amplitude in control rats, but not in chronic epileptic rats. These data indicate a long-lasting impairment of mGlu2/3 expression that may contribute to abnormal presynaptic plasticity, exaggerate glutamate release and hyperexcitability in temporal lobe epilepsy.

  15. Involvement of the glutamate receptor AtGLR3.3 in plant defense signaling and resistance to Hyaloperonospora arabidopsidis.

    PubMed

    Manzoor, Hamid; Kelloniemi, Jani; Chiltz, Annick; Wendehenne, David; Pugin, Alain; Poinssot, Benoit; Garcia-Brugger, Angela

    2013-11-01

    Like their animal counterparts, plant glutamate receptor-like (GLR) homologs are intimately associated with Ca(2+) influx through plasma membrane and participate in various physiological processes. In pathogen-associated molecular patterns (PAMP)-/elicitor-mediated resistance, Ca(2+) fluxes are necessary for activating downstream signaling events related to plant defense. In this study, oligogalacturonides (OGs), which are endogenous elicitors derived from cell wall degradation, were used to investigate the role of Arabidopsis GLRs in defense signaling. Pharmacological investigations indicated that GLRs are partly involved in free cytosolic [Ca(2+)] ([Ca(2+)]cyt) variations, nitric oxide (NO) production, reactive oxygen species (ROS) production and expression of defense-related genes by OGs. In addition, wild-type Col-0 plants treated with the glutamate-receptor antagonist 6,7-dinitriquinoxaline-2,3-dione (DNQX) had a compromised resistance to Botrytis cinerea and Hyaloperonospora arabidopsidis. Moreover, we provide genetic evidence that AtGLR3.3 is a key component of resistance against H. arabidopsidis. In addition, some OGs-triggered immune events such as defense gene expression, NO and ROS production are also to different extents dependent on AtGLR3.3. Taken together, these data provide evidence for the involvement of GLRs in elicitor/pathogen-mediated plant defense signaling pathways in Arabidopsis thaliana.

  16. Purification and characterization of a human RNA adenosine deaminase for glutamate receptor B pre-mRNA editing.

    PubMed

    Yang, J H; Sklar, P; Axel, R; Maniatis, T

    1997-04-29

    The glutamate receptor subunit B (GluR-B) pre-mRNA is edited at two adenosine residues, resulting in amino acid changes that alter the electrophysiologic properties of the glutamate receptor. Previous studies showed that these amino acid changes are due to adenosine to inosine conversions in two codons resulting from adenosine deamination. Here, we describe the purification and characterization of an activity from human HeLa cells that efficiently and accurately edits GluR-B pre-mRNA at both of these sites. The purified activity contains a human homolog of the recently reported rat RED1 (rRED1) protein, a member of the family of double-stranded RNA-dependent deaminase proteins. Recombinant human RED1 (hRED1), but not recombinant dsRAD, another member of the family, efficiently edits both the Q/R and R/G sites of GluR-B RNA. We conclude that the GluR-B editing activity present in HeLa cell extracts and the recombinant hRED1 protein are indistinguishable.

  17. Long-Term Activation of Group I Metabotropic Glutamate Receptors Increases Functional TRPV1-Expressing Neurons in Mouse Dorsal Root Ganglia

    PubMed Central

    Masuoka, Takayoshi; Kudo, Makiko; Yoshida, Junko; Ishibashi, Takaharu; Muramatsu, Ikunobu; Kato, Nobuo; Imaizumi, Noriko; Nishio, Matomo

    2016-01-01

    Damaged tissues release glutamate and other chemical mediators for several hours. These chemical mediators contribute to modulation of pruritus and pain. Herein, we investigated the effects of long-term activation of excitatory glutamate receptors on functional expression of transient receptor potential vaniloid type 1 (TRPV1) in dorsal root ganglion (DRG) neurons and then on thermal pain behavior. In order to detect the TRPV1-mediated responses in cultured DRG neurons, we monitored intracellular calcium responses to capsaicin, a TRPV1 agonist, with Fura-2. Long-term (4 h) treatment with glutamate receptor agonists (glutamate, quisqualate or DHPG) increased the proportion of neurons responding to capsaicin through activation of metabotropic glutamate receptor mGluR1, and only partially through the activation of mGluR5; engagement of these receptors was evident in neurons responding to allylisothiocyanate (AITC), a transient receptor potential ankyrin type 1 (TRPA1) agonist. Increase in the proportion was suppressed by phospholipase C (PLC), protein kinase C, mitogen/extracellular signal-regulated kinase, p38 mitogen-activated protein kinase or transcription inhibitors. Whole-cell recording was performed to record TRPV1-mediated membrane current; TRPV1 current density significantly increased in the AITC-sensitive neurons after the quisqualate treatment. To elucidate the physiological significance of this phenomenon, a hot plate test was performed. Intraplantar injection of quisqualate or DHPG induced heat hyperalgesia that lasted for 4 h post injection. This chronic hyperalgesia was attenuated by treatment with either mGluR1 or mGluR5 antagonists. These results suggest that long-term activation of mGluR1/5 by peripherally released glutamate may increase the number of neurons expressing functional TRPV1 in DRG, which may be strongly associated with chronic hyperalgesia. PMID:27064319

  18. Long-Term Activation of Group I Metabotropic Glutamate Receptors Increases Functional TRPV1-Expressing Neurons in Mouse Dorsal Root Ganglia.

    PubMed

    Masuoka, Takayoshi; Kudo, Makiko; Yoshida, Junko; Ishibashi, Takaharu; Muramatsu, Ikunobu; Kato, Nobuo; Imaizumi, Noriko; Nishio, Matomo

    2016-01-01

    Damaged tissues release glutamate and other chemical mediators for several hours. These chemical mediators contribute to modulation of pruritus and pain. Herein, we investigated the effects of long-term activation of excitatory glutamate receptors on functional expression of transient receptor potential vaniloid type 1 (TRPV1) in dorsal root ganglion (DRG) neurons and then on thermal pain behavior. In order to detect the TRPV1-mediated responses in cultured DRG neurons, we monitored intracellular calcium responses to capsaicin, a TRPV1 agonist, with Fura-2. Long-term (4 h) treatment with glutamate receptor agonists (glutamate, quisqualate or DHPG) increased the proportion of neurons responding to capsaicin through activation of metabotropic glutamate receptor mGluR1, and only partially through the activation of mGluR5; engagement of these receptors was evident in neurons responding to allylisothiocyanate (AITC), a transient receptor potential ankyrin type 1 (TRPA1) agonist. Increase in the proportion was suppressed by phospholipase C (PLC), protein kinase C, mitogen/extracellular signal-regulated kinase, p38 mitogen-activated protein kinase or transcription inhibitors. Whole-cell recording was performed to record TRPV1-mediated membrane current; TRPV1 current density significantly increased in the AITC-sensitive neurons after the quisqualate treatment. To elucidate the physiological significance of this phenomenon, a hot plate test was performed. Intraplantar injection of quisqualate or DHPG induced heat hyperalgesia that lasted for 4 h post injection. This chronic hyperalgesia was attenuated by treatment with either mGluR1 or mGluR5 antagonists. These results suggest that long-term activation of mGluR1/5 by peripherally released glutamate may increase the number of neurons expressing functional TRPV1 in DRG, which may be strongly associated with chronic hyperalgesia.

  19. D2 dopamine receptor but not AMPA and kainate glutamate receptor genes show altered expression in response to long term treatment with trans- and cis-flupenthixol in the rat brain.

    PubMed

    Chen, A C; Gurling, H M

    1999-05-07

    Glutamate receptor function has been hypothesized as an important factor in both the aetiology and treatment of schizophrenia. We have used a multiprobe oligonucleotide solution hybridization (MOSH) technique to examine the regulation of gene expression of the GluR1-7, KA1, and KA2 glutamate receptor subunits in the left rat brain following treatment with the optical isomers of flupenthixol at a dose of 0.2 mg kg-1 day-1 over a period of 4, 12, 24 weeks in order to understand how specific glutamate receptor genes are involved in the treatment of schizophrenia. The GluR2/3 and GluR6/7 subunit immunoreactivity in the right brain following 4 and 24 weeks of drug treatment was also examined by Western blotting. Neither trans- nor cis-flupenthixol was found to alter the gene expression of any of the 9 non-NMDA glutamate receptor subunits. On the other hand, we found a nearly two-fold increase in gene expression of the D2 dopamine receptor in specific brain regions. These results suggest that non-NMDA types of glutamate receptor subunits, in contrast to NMDA receptors, are less likely to have a role in the action of antipsychotic drugs.

  20. Glutamate and Neurodegenerative Disease

    NASA Astrophysics Data System (ADS)

    Schaeffer, Eric; Duplantier, Allen

    As the main excitatory neurotransmitter in the mammalian central nervous system, glutamate is critically involved in most aspects of CNS function. Given this critical role, it is not surprising that glutamatergic dysfunction is associated with many CNS disorders. In this chapter, we review the literature that links aberrant glutamate neurotransmission with CNS pathology, with a focus on neurodegenerative diseases. The biology and pharmacology of the various glutamate receptor families are discussed, along with data which links these receptors with neurodegenerative conditions. In addition, we review progress that has been made in developing small molecule modulators of glutamate receptors and transporters, and describe how these compounds have helped us understand the complex pharmacology of glutamate in normal CNS function, as well as their potential for the treatment of neurodegenerative diseases.

  1. Computational analysis of negative and positive allosteric modulator binding and function in metabotropic glutamate receptor 5 (in)activation.

    PubMed

    Dalton, James A R; Gómez-Santacana, Xavier; Llebaria, Amadeu; Giraldo, Jesús

    2014-05-27

    Metabotropic glutamate receptors (mGluRs) are high-profile G-protein coupled receptors drug targets because of their involvement in several neurological disease states, and mGluR5 in particular is a subtype whose controlled allosteric modulation, both positive and negative, can potentially be useful for the treatment of schizophrenia and relief of chronic pain, respectively. Here we model mGluR5 with a collection of positive and negative allosteric modulators (PAMs and NAMs) in both active and inactive receptor states, in a manner that is consistent with experimental information, using a specialized protocol that includes homology to increase docking accuracy, and receptor relaxation to generate an individual induced fit with each allosteric modulator. Results implicate two residues in particular for NAM and PAM function: NAM interaction with W785 for receptor inactivation, and NAM/PAM H-bonding with S809 for receptor (in)activation. Models suggest the orientation of the H-bond between allosteric modulator and S809, controlled by PAM/NAM chemistry, influences the position of TM7, which in turn influences the shape of the allosteric site, and potentially the receptor state. NAM-bound and PAM-bound mGluR5 models also reveal that although PAMs and NAMs bind in the same pocket and share similar binding modes, they have distinct effects on the conformation of the receptor. Our models, together with the identification of a possible activation mechanism, may be useful in the rational design of new allosteric modulators for mGluR5.

  2. Tolerance to LSD and DOB induced shaking behaviour: differential adaptations of frontocortical 5-HT(2A) and glutamate receptor binding sites.

    PubMed

    Buchborn, Tobias; Schröder, Helmut; Dieterich, Daniela C; Grecksch, Gisela; Höllt, Volker

    2015-03-15

    Serotonergic hallucinogens, such as lysergic acid diethylamide (LSD) and dimethoxy-bromoamphetamine (DOB), provoke stereotype-like shaking behaviour in rodents, which is hypothesised to engage frontocortical glutamate receptor activation secondary to serotonin2A (5-HT2A) related glutamate release. Challenging this hypothesis, we here investigate whether tolerance to LSD and DOB correlates with frontocortical adaptations of 5-HT2A and/or overall-glutamate binding sites. LSD and DOB (0.025 and 0.25 mg/kg, i.p.) induce a ketanserin-sensitive (0.5 mg/kg, i.p., 30-min pretreatment) increase in shaking behaviour (including head twitches and wet dog shakes), which with repeated application (7× in 4 ds) is undermined by tolerance. Tolerance to DOB, as indexed by DOB-sensitive [(3)H]spiroperidol and DOB induced [(35)S]GTP-gamma-S binding, is accompanied by a frontocortical decrease in 5-HT2A binding sites and 5-HT2 signalling, respectively; glutamate-sensitive [(3)H]glutamate binding sites, in contrast, remain unchanged. As to LSD, 5-HT2 signalling and 5-HT2A binding, respectively, are not or only marginally affected, yet [(3)H]glutamate binding is significantly decreased. Correlation analysis interrelates tolerance to DOB to the reduced 5-HT2A (r=.80) as well as the unchanged [(3)H]glutamate binding sites (r=.84); tolerance to LSD, as opposed, shares variance with the reduction in [(3)H]glutamate binding sites only (r=.86). Given that DOB and LSD both induce tolerance, one correlating with 5-HT2A, the other with glutamate receptor adaptations, it might be inferred that tolerance can arise at either level. That is, if a hallucinogen (like LSD in our study) fails to induce 5-HT2A (down-)regulation, glutamate receptors (activated postsynaptic to 5-HT2A related glutamate release) might instead adapt and thus prevent further overstimulation of the cortex.

  3. Antiparkinsonian potential of targeting group III metabotropic glutamate receptor subtypes in the rodent substantia nigra pars reticulata

    PubMed Central

    Broadstock, M; Austin, PJ; Betts, MJ; Duty, S

    2012-01-01

    BACKGROUND AND PURPOSE Increased firing of the glutamatergic pathway between the subthalamic nucleus and substantia nigra pars reticulata (SNpr) contributes to the abnormal firing of motor circuits and subsequent motor deficits seen in Parkinson's disease. Broad spectrum agonist-induced activation of presynaptic group III metabotropic glutamate (mGlu) receptors within the SNpr reduced glutamate release and reversed akinesia in the reserpine-treated rat model of Parkinson's disease. Here, we have sought to identify which subtypes of group III mGlu receptor in the SNpr were responsible for these beneficial effects. EXPERIMENTAL APPROACH The ability of the mGlu4 positive allosteric modulator, N-phenyl-7-(hydroxyminocyclopropa[b]chromen-1a-carboxamide) (PHCCC), the mGlu7 allosteric agonist, N,N′-dibenzhydrylethane-1,2-diamine dihydrochloride (AMN082) and the mGlu8-selective agonist (S)-3,4-dicarboxyphenylglycine [(S)-3,4-DCPG] to inhibit KCl-evoked [3H]-D-aspartate release was examined in vitro in rat nigral prisms. Reversal of akinesia in reserpine-treated rats was also assessed following intranigral injection of these agents. KEY RESULTS PHCCC and AMN082 inhibited [3H]-D-aspartate release by 42% and 53%, respectively when given alongside a sub-threshold concentration of the broad spectrum group III agonist, L-2-amino-4-phosphonobutyrate (L-AP4; 1 µM). In contrast (S)-3,4-DCPG failed to inhibit [3H]-D-aspartate release. All three agents also reversed reserpine-induced akinesia although only the effects of PHCCC and AMN082 were inhibited by pre-treatment with the group III antagonist (RS)-α-cyclopropyl-4-phosphonophenylglycine (CPPG). CONCLUSIONS AND IMPLICATIONS These findings reveal that targeting SNpr mGlu4 or mGlu7 receptors, but not mGlu8 receptors, provided relief from akinesia in the reserpine-treated rat model of Parkinson's disease, most likely reflecting inhibition of excess glutamate release in this region. PMID:21627638

  4. Decreased glutamate receptor binding and NMDA R1 gene expression in hippocampus of pilocarpine-induced epileptic rats: neuroprotective role of Bacopa monnieri extract.

    PubMed

    Khan, Reas; Krishnakumar, Amee; Paulose, C S

    2008-01-01

    The potential for antiepileptic drugs to negatively impact cognitive abilities has generated renewed interest in herbal drugs and formulations in the treatment of epilepsy. Bacopa monnieri is one such widely used revitalizing herb that purportedly strengthens nervous function and also possesses memory-enhancing, antioxidative, antiepileptic, and anti-inflammatory properties. We investigated the neuroprotective role of B. monnieri extract in alteration of glutamate receptor binding and gene expression of NMDA R1 in hippocampus of temporal lobe epileptic rats. In association with pilocarpine-induced epilepsy, there was significant downregulation of NMDA R1 gene expression and glutamate receptor binding without any change in its affinity. B. monnieri treatment of epileptic rats significantly reversed the expression of NMDA R1 and glutamate receptor binding alterations to near-control levels. Also, in the epileptic rats, we measured a significant increase in the activity of glutamate dehydrogenase, which neared the control level after B. monnieri treatment. The therapeutic effect of B. monnieri was also observed in the Morris water maze experiment. These data together indicate the neuroprotective role of B. monnieri extract in glutamate-mediated excitotoxicity during seizures and cognitive damage occurring in association with pilocarpine-induced epilepsy.

  5. Presynaptic G protein-coupled receptors dynamically modify vesicle fusion, synaptic cleft glutamate concentrations and motor behavior

    PubMed Central

    Gerachshenko, Tatyana; Schwartz, Eric; Bleckert, Adam; Photowala, Huzefa; Seymour, Andrew; Alford, Simon

    2009-01-01

    Understanding how neuromodulators regulate behavior requires investigating their effects on functional neural systems, but also their underlying cellular mechanisms. Utilizing extensively characterized lamprey motor circuits, and the unique access to reticulospinal presynaptic terminals in the intact spinal cord that initiate these behaviours, we have investigated effects of presynaptic G protein-coupled receptors on locomotion from the systems level, to the molecular control of vesicle fusion. 5-HT inhibits neurotransmitter release via a Gβγ interaction with the SNARE complex that promotes kiss-and-run vesicle fusion. In the lamprey spinal cord we demonstrate that while presynaptic 5-HT receptors inhibit evoked neurotransmitter release from reticulospinal command neurons, their activation does not abolish locomotion, but rather modulates locomotor rhythms. Liberation of presynaptic Gβγ causes substantial inhibition of AMPA receptor-mediated synaptic responses, but leaves NMDA receptor-mediated components of neurotransmission largely intact. Because Gβγ binding to the SNARE complex is displaced by Ca2+-synaptotagmin binding, 5-HT-mediated inhibition displays Ca2+ sensitivity. We show that as Ca2+ accumulates presynaptically during physiological bouts of activity, 5-HT/Gβγ-mediated presynaptic inhibition is relieved leading to a frequency-dependent increase in synaptic concentrations of glutamate. This frequency dependent phenomenon mirrors a shift in the vesicle fusion mode and a recovery of AMPA receptor-mediated EPSCs from inhibition without a modification of NMDA receptor EPSCs. We conclude that activation of presynaptic 5-HT GPCRs state-dependently alters vesicle fusion properties to shift the weight of NMDA vs AMPA receptor-mediated responses at excitatory synapses. We have therefore identified a novel mechanism in which modification of vesicle fusion modes may profoundly alter locomotor behaviour. PMID:19692597

  6. Abnormalities in glutamate metabolism and excitotoxicity in the retinal diseases.

    PubMed

    Ishikawa, Makoto

    2013-01-01

    In the physiological condition, glutamate acts as an excitatory neurotransmitter in the retina. However, excessive glutamate can be toxic to retinal neurons by overstimulation of the glutamate receptors. Glutamate excess is primarily attributed to perturbation in the homeostasis of the glutamate metabolism. Major pathway of glutamate metabolism consists of glutamate uptake by glutamate transporters followed by enzymatic conversion of glutamate to nontoxic glutamine by glutamine synthetase. Glutamate metabolism requires energy supply, and the energy loss inhibits the functions of both glutamate transporters and glutamine synthetase. In this review, we describe the present knowledge concerning the retinal glutamate metabolism under the physiological and pathological conditions.

  7. Role of gamma-aminobutyric acid (GABA) and metabotropic glutamate receptors in nicotine reinforcement: potential pharmacotherapies for smoking cessation.

    PubMed

    Markou, Athina; Paterson, Neil E; Semenova, Svetlana

    2004-10-01

    Previous work indicated a role for GABA and glutamate in the reinforcing effects of drugs of abuse. The present studies assessed the effects of GABAergic and glutamatergic manipulations on the reinforcing effects of nicotine as assessed by intravenous nicotine self-administration. Male Wistar rats were allowed to self-administer either of two nicotine doses under a fixed ratio or a progressive ratio schedule of reinforcement. The effects of a glutamatergic compound on nicotine self-administration in male DBA/2J mice were also explored. Finally, to assess for nonspecific effects of the drug manipulations, the effects of all test compounds on responding maintained by a food reinforcer were investigated. The pharmacological manipulations used were: gamma-vinyl-GABA (vigabatrin or GVG), an irreversible inhibitor of GABA transaminase, the GABAB receptor agonists (-)baclofen and CGP44532, and the metabotropic glutamate receptor 5 (mGluR5) antagonist MPEP. GVG, CGP44532, and (-)baclofen dose-dependently decreased nicotine self-administration on the fixed-ratio schedule, but also decreased food-maintained responding. Furthermore, CGP44532 decreased breakpoints for nicotine and food at identical doses under the progressive-ratio schedule. MPEP dose-dependently decreased nicotine self-administration with no effect on food-maintained responding in rats. MPEP also decreased nicotine self-administration in the mice. These results demonstrate that activation of GABAB receptors or blockade of mGluR5 decreased nicotine self-administration. Although there was some selectivity for the effects of the GABAergic manipulations, there was clear selectivity of the effects of MPEP on nicotine- versus food-maintained responding. Thus, compounds that increase GABAergic neurotransmission and antagonists at mGluR5 have potential as anti-smoking medications for humans.

  8. Group I metabotropic glutamate receptor actions in oriens/alveus interneurons of rat hippocampal CA1 region.

    PubMed

    Gee, Christine E; Lacaille, Jean-Claude

    2004-03-12

    Group I metabotropic glutamate receptors (mGluRs) are important for hippocampal interneuron function. We used whole-cell recording and confocal imaging to characterize group I mGluR actions in CA1 oriens/alveus interneurons in slices. In tetrodotoxin and ionotropic glutamate receptor antagonists, the group I mGluR specific agonist DHPG increased intradendritic Ca(2+) levels and depolarized interneurons, whereas the group II mGluR specific agonist DCG-IV and the group III mGluR specific agonist L-AP4 did not. DHPG-induced depolarizing and Ca(2+) responses were antagonized by the group I mGluR antagonist 4CPG, but only Ca(2+) responses were significantly inhibited by the mGluR1 antagonist CPCCOEt. DHPG-induced depolarizing responses were not blocked by the inositol-1,4,5-trisphosphate (IP(3)) receptor inhibitor heparin, the protein kinase C (PKC) antagonists GF-109203X, or the inhibitor of phospholipase C (PLC) U73122. Thus, these responses to DHPG may not be transduced by the PLC-->IP(3)/diacylglycerol (DAG) pathway classically linked to group I mGluRs. DHPG-induced depolarizations were not blocked by intracellular GDP beta S or bath-application of N-ethylmaleimide (NEM), suggesting the involvement of a G protein-independent pathway. Our findings indicate that group I mGluRs induce a depolarization of oriens/alveus interneurons via a G protein-independent mechanism different from their classic signalling pathway. Since depolarizations are associated with intracellular Ca(2+) rises, these actions may be important for their synaptic plasticity and vulnerability to excitotoxicity.

  9. Structurally dissimilar antimanic agents modulate synaptic plasticity by regulating AMPA glutamate receptor subunit GluR1 synaptic expression.

    PubMed

    Du, Jing; Gray, Neil A; Falke, Cynthia; Yuan, Peixiong; Szabo, Steven; Manji, Husseini K

    2003-11-01

    A growing body of data from clinical and preclinical studies suggests that the glutamatergic system may represent a novel therapeutic target for severe recurrent mood disorders. Since synapse-specific glutamate receptor expression/localization is known to play critical roles in synaptic plasticity, we investigated the effects of mood stabilizers on AMPA receptor expression. Rats were treated chronically with lithium or valproate, hippocampal synaptosomes were isolated, and GluR1 levels were determined. Additionally, hippocampal neurons were prepared from E18 rat embryos and treated with lithium or valproate. Surface expression of GluR1 was determined using a biotinylation assay, and double-immunostaining with anti-GluR1 and anti-synaptotagmin antibodies was used to determine synaptic GluR1 levels. The AMPA receptor subunit GluR1 expression in hippocampal synaptosomes was significantly reduced by both chronic lithium and valproate. Overall, these studies show that AMPA receptor subunit GluR1 is a common target for two structurally highly dissimilar, but highly efficacious, mood stabilizers, lithium and valproate. These studies suggest that regulation of glutamatergically mediated synaptic plasticity may play a role in the treatment of mood disorders, and raise the possibility that agents more directly affecting synaptic GluR1 may represent novel therapies for this devastating illness.

  10. Activation of N-methyl-D-aspartate receptors by L-glutamate in cells dissociated from adult rat hippocampus.

    PubMed Central

    Gibb, A J; Colquhoun, D

    1992-01-01

    1. Single channel recording techniques were used to study the ion channel openings resulting from activation of N-methyl-D-aspartate (NMDA) receptors by the agonist glutamate. Patches were from cells acutely dissociated from adult rat hippocampus (CA1). Channel activity was studied at low glutamate concentrations (20-100 nM) with 1 microM-glycine, in the absence of extracellular divalent cations. 2. Channel openings were to two main conductance levels corresponding to 50 pS and 40 pS openings in extracellular solution with 1 mM-Ca2+. Around 80% of openings were to the large conductance level. The single channel conductances increased as extracellular Ca2+ was reduced. 3. Distributions of channel open times were described by three exponential components of 87 microseconds, 0.91 ms and 4.72 ms (relative areas of 51, 31 and 18%). Most long openings were to the large conductance level. 4. The channel closed time distribution was complex, requiring five exponential components to describe it adequately. Of these five components, at least three, with time constants of 68 microseconds, 0.72 ms and 7.6 ms (relative areas of 38, 12 and 17%) represent gaps within single activations of the receptor. The presence of a component with a mean of 7.6 ms is notable because gaps of this length have not previously been identified as being within single NMDA receptor channel activations. 5. Channel activations were identified as including gaps underlying at least the first three closed time components. Activations consisted of clusters of channel openings. Distributions of the length of these clusters had mean time constants of 88 microseconds, 3.4 ms and 32 ms (relative areas of 45, 25 and 30%). Long clusters contained short, intermediate and long duration openings as well as subconductance openings. The open probability within clusters averaged 0.62. Three components were evident in distributions of the number of openings per cluster. These had mean values of 1.22, 3.2 and 11

  11. Contribution of different classes of glutamate receptors in the corticostriatal polysynaptic responses from striatal direct and indirect projection neurons

    PubMed Central

    2013-01-01

    Background Previous work showed differences in the polysynaptic activation of GABAergic synapses during corticostriatal suprathreshold responses in direct and indirect striatal projection neurons (dSPNs and iSPNs). Here, we now show differences and similarities in the polysynaptic activation of cortical glutamatergic synapses on the same responses. Corticostriatal contacts have been extensively studied. However, several questions remain unanswered, e.g.: what are the differences and similarities in the responses to glutamate in dSPNs and iSPNs? Does glutamatergic synaptic activation exhibits a distribution of latencies over time in vitro? That would be a strong suggestion of polysynaptic cortical convergence. What is the role of kainate receptors in corticostriatal transmission? Current-clamp recordings were used to answer these questions. One hypothesis was: if prolonged synaptic activation distributed along time was present, then it would be mainly generated from the cortex, and not from the striatum. Results By isolating responses from AMPA-receptors out of the complex suprathreshold response of SPNs, it is shown that a single cortical stimulus induces early and late synaptic activation lasting hundreds of milliseconds. Prolonged responses depended on cortical stimulation because they could not be elicited using intrastriatal stimulation, even if GABAergic transmission was blocked. Thus, the results are not explained by differences in evoked inhibition. Moreover, inhibitory participation was larger after cortical than after intrastriatal stimulation. A strong activation of interneurons was obtained from the cortex, demonstrating that polysynaptic activation includes the striatum. Prolonged kainate (KA) receptor responses were also elicited from the cortex. Responses of dSPNs and iSPNs did not depend on the cortical area stimulated. In contrast to AMPA-receptors, responses from NMDA- and KA-receptors do not exhibit early and late responses, but generate slow

  12. Metabotropic glutamate receptors are involved in the detection of IMP and L-amino acids by mouse taste sensory cells.

    PubMed

    Pal Choudhuri, S; Delay, R J; Delay, E R

    2016-03-01

    G-protein-coupled receptors are thought to be involved in the detection of umami and L-amino acid taste. These include the heterodimer taste receptor type 1 member 1 (T1r1)+taste receptor type 1 member 3 (T1r3), taste and brain variants of mGluR4 and mGluR1, and calcium sensors. While several studies suggest T1r1+T1r3 is a broadly tuned lLamino acid receptor, little is known about the function of metabotropic glutamate receptors (mGluRs) in L-amino acid taste transduction. Calcium imaging of isolated taste sensory cells (TSCs) of T1r3-GFP and T1r3 knock-out (T1r3 KO) mice was performed using the ratiometric dye Fura 2 AM to investigate the role of different mGluRs in detecting various L-amino acids and inosine 5' monophosphate (IMP). Using agonists selective for various mGluRs such as (RS)-3,5-dihydroxyphenylglycine (DHPG) (an mGluR1 agonist) and L-(+)-2-amino-4-phosphonobutyric acid (l-AP4) (an mGluR4 agonist), we evaluated TSCs to determine if they might respond to these agonists, IMP, and three L-amino acids (monopotassium L-glutamate, L-serine and L-arginine). Additionally, we used selective antagonists against different mGluRs such as (RS)-L-aminoindan-1,5-dicarboxylic acid (AIDA) (an mGluR1 antagonist), and (RS)-α-methylserine-O-phosphate (MSOP) (an mGluR4 antagonist) to determine if they can block responses elicited by these L-amino acids and IMP. We found that L-amino acid- and IMP-responsive cells also responded to each agonist. Antagonists for mGluR4 and mGluR1 significantly blocked the responses elicited by IMP and each of the L-amino acids. Collectively, these data provide evidence for the involvement of taste and brain variants of mGluR1 and mGluR4 in L-amino acid and IMP taste responses in mice, and support the concept that multiple receptors contribute to IMP and L-amino acid taste.

  13. Pharmacology of postsynaptic metabotropic glutamate receptors in rat hippocampal CA1 pyramidal neurones.

    PubMed

    Davies, C H; Clarke, V R; Jane, D E; Collingridge, G L

    1995-09-01

    1. Activation of metabotropic glutamate receptors (mGluRs) in hippocampal CA1 pyramidal neurones leads to a depolarization, an increase in input resistance and a reduction in spike frequency adaptation (or accommodation). At least eight subtypes of mGluR have been identified which have been divided into three groups based on their biochemical, structural and pharmacological properties. It is unclear to which group the mGluRs which mediate these excitatory effects in hippocampal CA1 pyramidal neurones belong. We have attempted to address this question by using intracellular recording to test the effects of a range of mGluR agonists and antagonists, that exhibit different profiles of subtype specificity, on the excitability of CA1 pyramidal neurones in rat hippocampal slices. 2. (2S, 1'S,2'S)-2-(2'-carboxycyclopropyl)glycine (L-CCG1) caused a reduction in spike frequency adaptation and a depolarization (1-10 mV) associated with an increase in input resistance (10-30%) at concentrations (> or = 50 microM) that have been shown to activate mGluRs in groups I, II and III. Similar effects were observed with concentrations (50-100 microM) of (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid ((1S,3R)-ACPD) and (1S,3S)-ACPD that exhibit little or no activity at group III mGluRs but which activate groups I and II mGluRs. 3. Inhibition of the release of endogenous neurotransmitters through activation of GABAB receptors, by use of 200 microM (+/-)-baclofen, did not alter the effects of (1S,3R)-ACPD (50-100 microM), (1S,3S)-ACPD (100 microM) or L-CCG1 (100 microM). This suggests that mGluR agonists directly activate CA1 pyramidal neurones. 4. Like these broad spectrum mGluR agonists, the racemic mixture ((SR)-) or resolved (S)-isomer of the selective group I mGluR agonist 3,5-dihydroxyphenylglycine ((SR)-DHPG (50-100 microM) or (S)-DHPG (20-50 microM)) caused a reduction in spike frequency adaptation concomitant with postsynaptic depolarization and an increase in input

  14. Excitotoxic death induced by released glutamate in depolarized primary cultures of mouse cerebellar granule cells is dependent on GABAA receptors and niflumic acid-sensitive chloride channels.

    PubMed

    Babot, Zoila; Cristòfol, Rosa; Suñol, Cristina

    2005-01-01

    Excitotoxic neuronal death has been linked to neurological and neurodegenerative diseases. Several studies have sought to clarify the involvement of Cl(-) channels in neuronal excitotoxicity using either N-methyl-D-aspartic acid (NMDA) or alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate/kainic acid agonists. In this work we induced excitotoxic death in primary cultures of cerebellar granule cells by means of endogenously released glutamate. Excitotoxicity was provoked by exposure to high extracellular K(+) concentrations ([K(+)](o)) for 5 min. Under these conditions, a Ca(2+)-dependent release of glutamate was evoked. When extracellular glutamate concentration rose to between 2 and 4 microM, cell viability was significantly reduced by 30-40%. The NMDA receptor antagonists (MK-801 and D-2-amino-5-phosphonopentanoic acid) prevented cell death. Exposure to high [K(+)](o) produced a (36)Cl(-) influx which was significantly reduced by picrotoxinin. In addition, the GABA(A) receptor antagonists (bicuculline, picrotoxinin and SR 95531) protected cells from high [K(+)](o)-triggered excitotoxicity and reduced extracellular glutamate concentration. The Cl(-) channel blockers niflumic acid and 5-nitro-2-(3-phenylpropylamino)benzoic acid also exerted a neuroprotective effect and reduced extracellular glutamate concentration, even though they did not reduce high [K(+)](o)-induced (36)Cl(-) influx. Primary cultures of cerebellar granule cells also contain a population of GABAergic neurons that released GABA in response to high [K(+)](o). Chronic treatment of primary cultures with kainic acid abolished GABA release and rendered granule cells insensitive to high [K(+)](o) exposure, even though NMDA receptors were functional. Altogether, these results demonstrate that, under conditions of membrane depolarization, low micromolar concentrations of extracellular glutamate might induce an excitotoxic process through both NMDA and GABA(A) receptors and niflumic acid-sensitive Cl

  15. Tetrahydronaphthyridine and Dihydronaphthyridinone Ethers As Positive Allosteric Modulators of the Metabotropic Glutamate Receptor 5 (mGlu5)

    PubMed Central

    2015-01-01

    Positive allosteric modulators (PAMs) of metabotropic glutamate receptor 5 (mGlu5) represent a promising therapeutic strategy for the treatment of schizophrenia. Starting from an acetylene-based lead from high throughput screening, an evolved bicyclic dihydronaphthyridinone was identified. We describe further refinements leading to both dihydronaphthyridinone and tetrahydronaphthyridine mGlu5 PAMs containing an alkoxy-based linkage as an acetylene replacement. Exploration of several structural features including western pyridine ring isomers, positional amides, linker connectivity/position, and combinations thereof, reveal that these bicyclic modulators generally exhibit steep SAR and within specific subseries display a propensity for pharmacological mode switching at mGlu5 as well as antagonist activity at mGlu3. Structure–activity relationships within a dihydronaphthyridinone subseries uncovered 12c (VU0405372), a selective mGlu5 PAM with good in vitro potency, low glutamate fold-shift, acceptable DMPK properties, and in vivo efficacy in an amphetamine-based model of psychosis. PMID:24914612

  16. Metabotropic glutamate receptor 6 signaling enhances TRPM1 calcium channel function and increases melanin content in human melanocytes.

    PubMed

    Devi, Sulochana; Markandeya, Yogananda; Maddodi, Nityanand; Dhingra, Anuradha; Vardi, Noga; Balijepalli, Ravi C; Setaluri, Vijayasaradhi

    2013-05-01

    Mutations in TRPM1, a calcium channel expressed in retinal bipolar cells and epidermal melanocytes, cause complete congenital stationary night blindness with no discernible skin phenotype. In the retina, TRPM1 activity is negatively coupled to metabotropic glutamate receptor 6 (mGluR6) signaling through Gαo and TRPM1 mutations result in the loss of responsiveness of TRPM1 to mGluR6 signaling. Here, we show that human melanocytes express mGluR6, and treatment of melanocytes with L-AP4, a type III mGluR-selective agonist, enhances Ca(2+) uptake. Knockdown of TRPM1 or mGluR6 by shRNA abolished L-AP4-induced Ca(2+) influx and TRPM1 currents, showing that TRPM1 activity in melanocytes is positively coupled to mGluR6 signaling. Gαo protein is absent in melanocytes. However, forced expression of Gαo restored negative coupling of TRPM1 to mGluR6 signaling, but treatment with pertussis toxin, an inhibitor of Gi /Go proteins, did not affect basal or mGluR6-induced Ca(2+) uptake. Additionally, chronic stimulation of mGluR6 altered melanocyte morphology and increased melanin content. These data suggest differences in coupling of TRPM1 function to mGluR6 signaling explain different cellular responses to glutamate in the retina and the skin.

  17. EXPRESSION OF VESICULAR GLUTAMATE TRANSPORTERS IN TRANSIENT RECEPTOR POTENTIAL MELASTATIN 8 (TRPM8)-POSITIVE DENTAL AFFERENTS IN THE MOUSE

    PubMed Central

    Kim, Y. S.; Kim, T. H.; Mckemy, D. D.; Bae, Y. C.

    2017-01-01

    Transient receptor potential melastatin 8 (TRPM8) is activated by innocuous cool and noxious cold and plays a crucial role in cold-induced acute pain and pain hypersensitivity. To help understand the mechanism of TRPM8-mediated cold perception under normal and pathologic conditions, we used light microscopic immunohistochemistry and Western blot analysis in mice expressing a genetically encoded axonal tracer in TRPM8-positive (+) neurons. We investigated the coexpression of TRPM8 and vesicular glutamate transporter 1 (VGLUT1) and VGLUT2 in the trigeminal ganglion (TG) and the dental pulp before and after inducing pulpal inflammation. Many TRPM8+ neurons in the TG and axons in the dental pulp expressed VGLUT2, while none expressed VGLUT1. TRPM8+ axons were dense in the pulp horn and peripheral pulp and also frequently observed in the dentinal tubules. Following pulpal inflammation, the proportion of VGLUT2+ and of VGLUT2+/TRPM8+ neurons increased significantly, whereas that of TRPM8+ neurons remained unchanged. Our findings suggest the existence of VGLUT2 (but not VGLUT1)-mediated glutamate signaling in TRPM8+ neurons possibly underlying the cold-induced acute pain and hypersensitivity to cold following pulpal inflammation. PMID:26166724

  18. Metabotropic glutamate receptor 6 signaling enhances TRPM1 calcium channel function and increases melanin content in human melanocytes

    PubMed Central

    Devi, Sulochana; Markandeya, Yogananda; Maddodi, Nityanand; Dhingra, Anuradha; Vardi, Noga; Balijepalli, Ravi C; Setaluri, Vijayasaradhi

    2013-01-01

    SUMMARY Mutations in TRPM1, a calcium channel expressed in retinal bipolar cells and epidermal melanocytes, cause complete congenital stationary night blindness with no discernible skin phenotype. In the retina, TRPM1 activity is negatively coupled to metabotropic glutamate receptor 6 (mGluR6) signaling through Gαo and TRPM1 mutations result in the loss of responsiveness of TRPM1 to mGluR6 signaling. Here, we show that human melanocytes express mGluR6 and treatment of melanocytes with L-AP4, a type III mGluR-selective agonist, enhances Ca2+ uptake. Knockdown of TRPM1 or mGluR6 by shRNA abolished L-AP4-induced Ca2+ influx and TRPM1 currents showing that TRPM1 activity in melanocytes is positively coupled to mGluR6 signaling. Gαo protein is absent in melanocytes. However, forced expression of Gαo restored negative coupling of TRPM1 to mGluR6 signaling, but treatment with and pertussis toxin, an inhibitor of Gi/Go proteins, did not affect basal or mGluR6-induced Ca2+ uptake. Additionally, chronic stimulation of mGluR6 altered melanocyte morphology and increased melanin content. These data suggest differences in coupling of TRPM1 function to mGluR6 signaling explain different cellular responses to glutamate in the retina and the skin. PMID:23452348

  19. Activation of Metabotropic Glutamate Receptor Type 2/3 Supports the Involvement of the Hippocampal Mossy Fiber Pathway on Contextual Fear Memory Consolidation

    ERIC Educational Resources Information Center

    Daumas, Stephanie; Ceccom, Johnatan; Halley, Helene; Frances, Bernard; Lassalle, Jean-Michel

    2009-01-01

    Elucidating the functional properties of the dentate gyrus (DG), CA3, and CA1 areas is critical for understanding the role of the dorsal hippocampus in contextual fear memory processing. In order to specifically disrupt various hippocampal inputs, we used region-specific infusions of DCG-IV, the metabotropic glutamate receptor agonist, which…

  20. New positive allosteric modulators of the metabotropic glutamate receptor 2 (mGluR2): identification and synthesis of N-propyl-8-chloro-6-substituted isoquinolones.

    PubMed

    Trabanco, Andrés A; Duvey, Guillaume; Cid, José María; Macdonald, Gregor J; Cluzeau, Philippe; Nhem, Vanthea; Furnari, Rocco; Behaj, Nadia; Poulain, Géraldine; Finn, Terry; Lavreysen, Hilde; Poli, Sonia; Raux, Alexandre; Thollon, Yves; Poirier, Nicolas; D'Addona, David; Andrés, José Ignacio; Lutjens, Robert; Le Poul, Emmanuel; Imogai, Hassan; Rocher, Jean-Philippe

    2011-02-01

    A series of N-propyl-8-chloro-6-substituted isoquinolones was identified as positive allosteric modulators of metabotropic glutamate receptor 2 (mGluR2 PAM) via high throughput screening (HTS). The subsequent synthesis and initial SAR exploration that led to the identification of compound 28 is described.

  1. AMPA receptor activation, but not the accumulation of endogenous extracellular glutamate, induces paralysis and motor neuron death in rat spinal cord in vivo.

    PubMed

    Corona, Juan Carlos; Tapia, Ricardo

    2004-05-01

    The mechanisms of motor neuron (MN) degeneration in amyotrophic lateral sclerosis (ALS) are unknown, but glutamate-mediated excitotoxicity may be involved. To examine directly this idea in vivo, we have used microdialysis in the rat lumbar spinal cord and showed that four- to fivefold increases in the concentration of endogenous extracellular glutamate during at least 1 h, by perfusion with the glutamate transport inhibitor L-2,4-trans-pyrrolidine-dicarboxylate, elicited no motor alterations or MN damage. Stimulation of glutamate release with 4-aminopyridine induced transitory ipsilateral hindlimb muscular twitches but no MN damage. In contrast, perfusion of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) did not modify glutamate levels but produced intense muscular spasms, followed by ipsilateral permanent hindlimb paralysis and a remarkable loss of MNs. These effects of AMPA were prevented by co-perfusion with the AMPA receptor antagonist 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline. Perfusion with NMDA or kainate produced no motor effects or MN damage. Thus, the elevation of endogenous extracellular glutamate in vivo due to blockade of its transport is innocuous for spinal MNs. Because this resistance is observed under the same experimental conditions in which MNs are highly vulnerable to AMPA, these results indicate that excitotoxicity due to this mechanism might not be an important factor in the pathogenesis of ALS.

  2. Extraintestinal manifestations of celiac disease: 33-mer gliadin binding to glutamate receptor GRINA as a new explanation.

    PubMed

    Garcia-Quintanilla, Albert; Miranzo-Navarro, Domingo

    2016-05-01

    We propose a biochemical mechanism for celiac disease and non-celiac gluten sensitivity that may rationalize many of the extradigestive disorders not explained by the current immunogenetic model. Our hypothesis is based on the homology between the 33-mer gliadin peptide and a component of the NMDA glutamate receptor ion channel - the human GRINA protein - using BLASTP software. Based on this homology the 33-mer may act as a natural antagonist interfering with the normal interactions of GRINA and its partners. The theory is supported by numerous independent data from the literature, and provides a mechanistic link with otherwise unrelated disorders, such as cleft lip and palate, thyroid dysfunction, restless legs syndrome, depression, ataxia, hearing loss, fibromyalgia, dermatitis herpetiformis, schizophrenia, toxoplasmosis, anemia, osteopenia, Fabry disease, Barret's adenocarcinoma, neuroblastoma, urinary incontinence, recurrent miscarriage, cardiac anomalies, reduced risk of breast cancer, stiff person syndrome, etc. The hypothesis also anticipates better animal models, and has the potential to open new avenues of research.

  3. Positive allosteric modulators (PAMs) of metabotropic glutamate receptor 5 (mGluR5) attenuate microglial activation.

    PubMed

    Xue, Fengtian; Stoica, Bogdan A; Hanscom, Marie; Kabadi, Shruti V; Faden, Alan I

    2014-01-01

    Traumatic brain injury causes progressive neurodegeneration associated with chronic microglial activation. Recent studies show that neurodegeneration and neuroinflammation after traumatic brain injury can be inhibited as late as one month in animals by the activation of the metabotropic glutamate receptor 5 in microglia using (RS)-2-chloro-5- hydroxy-phenylglycine. However, the therapeutic potential of this agonist is limited due to its relatively weak potency and brain permeability. To address such concerns, we evaluated the anti-inflammatory activities of several positive allosteric modulators using various in vitro assays, and found that 3,3'-difluorobenzaldazine, 3-cyano-N-(1,3-diphenyl-1H-pyrazol- 5-yl)benzamide and 4-nitro-N-(1-(2-fluorophenyl)-3-phenyl-1H-pyrazol-5-yl)benzamide showed significantly improved potency which makes them potential lead compounds for further development of positive allosteric modulators for the treatment of traumatic brain injury.

  4. Glutamate regulates intracellular calcium and gene expression in oligodendrocyte progenitors through the activation of DL-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors.

    PubMed Central

    Pende, M; Holtzclaw, L A; Curtis, J L; Russell, J T; Gallo, V

    1994-01-01

    Oligodendrocytes and their progenitors (O-2A) express functional kainate- and DL-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-preferring glutamate receptors. The physiological consequences of activation of these receptors were studied in purified rat cortical O-2A progenitors and in the primary oligodendrocyte cell line CG-4. Changes in the mRNA levels of a set of immediate early genes were studied and were correlated to intracellular Ca2+ concentration, as measured by fura-2 Ca2+ imaging. Both in CG-4 and in cortical O-2A progenitors, basal mRNA levels of NGFI-A were much higher than c-fos, c-jun, or jun-b. Glutamate, kainate, and AMPA greatly increased NGFI-A mRNA and protein by activation of membrane receptors in a Ca(2+)-dependent fashion. Agonists at non-N-methyl-D-aspartate receptors promoted transmembrane Ca2+ influx through voltage-dependent channels as well as kainate and/or AMPA channels. The influx of Ca2+ ions occurring through glutamate-gated channels was sufficient by itself to increase the expression of NGFI-A mRNA. AMPA receptors were found to be directly involved in intracellular Ca2+ and NGFI-A mRNA regulation, because the effects of kainate were greatly enhanced by cyclothiazide, an allosteric modulator that selectively suppresses desensitization of AMPA but not kainate receptors. Our results indicate that glutamate acting at AMPA receptors regulates immediate early gene expression in cells of the oligodendrocyte lineage by increasing intracellular calcium. Consequently, modulation of these receptor channels may have immediate effects at the genomic level and regulate oligodendrocyte development at critical stages. Images PMID:8159727

  5. General synthesis of β-alanine-containing spider polyamine toxins and discovery of nephila polyamine toxins 1 and 8 as highly potent inhibitors of ionotropic glutamate receptors.

    PubMed

    Lucas, Simon; Poulsen, Mette H; Nørager, Niels G; Barslund, Anne F; Bach, Tinna B; Kristensen, Anders S; Strømgaard, Kristian

    2012-11-26

    Certain spiders contain large pools of polyamine toxins, which are putative pharmacological tools awaiting further discovery. Here we present a general synthesis strategy for this class of toxins and prepare five structurally varied polyamine toxins. Electrophysiological testing at three ionotropic glutamate receptor subtypes reveals that two of these, Nephila polyamine toxins 1 (NPTX-1) and 8 (NPTX-8), comprise intriguing pharmacological activities by having subnanomolar IC(50) values at kainate receptors.

  6. L-theanine protects the APP (Swedish mutation) transgenic SH-SY5Y cell against glutamate-induced excitotoxicity via inhibition of the NMDA receptor pathway.

    PubMed

    Di, X; Yan, J; Zhao, Y; Zhang, J; Shi, Z; Chang, Y; Zhao, B

    2010-07-14

    As a natural analogue of glutamate, l-theanine is the unique amino acid derivative in green tea. Although its underlining mechanisms are not yet clear, it has been suggested that l-theanine treatment may prove beneficial to patients with neurodegenerative diseases. In this study, we investigated the neuroprotective effect and its mechanism of l-theanine in an in vitro model of Alzheimer's disease by using the human APP (Swedish mutation) transgenic SH-SY5Y cell. Amyloid beta (Abeta) neurotoxicity was triggered by l-glutamate in this cell line. Additionally, l-theanine significantly attenuated l-glutamate-induced apoptosis at similar levels to those seen with the NMDA receptor inhibitor MK-801 in the stably expressing APP Swedish mutation SH-SY5Y cells which over-generated Abeta. Meanwhile, the activation of c-Jun N-terminal kinase and caspase-3 induced by l-glutamate was suppressed by l-theanine. We also found that cells treated with l-theanine showed decreased production of nitric oxide resulting from the down-regulated protein levels of inducible nitric oxide synthase (iNOS) and neuronal nitric oxide synthase (nNOS). These results indicate that the inhibition of the NMDA subtype of glutamate receptors and its related pathways is the crucial point of the neuroprotective effect of l-theanine in the cell model. Thus, our present study supports the notion that l-theanine may provide effective prophylaxis and treatment for Alzheimer's disease.

  7. Relief from detrimental consequences of chronic psychosocial stress in mice deficient for the metabotropic glutamate receptor subtype 7.

    PubMed

    Peterlik, Daniel; Stangl, Christina; Bludau, Anna; Grabski, Dominik; Strasser, Robert; Schmidt, Dominic; Flor, Peter J; Uschold-Schmidt, Nicole

    2016-05-14

    Chronic stress-related psychiatric conditions and comorbid somatic pathologies are an enormous public health concern in modern society. The etiology of these disorders is complex, with stressors holding a chronic and psychosocial component representing the most acknowledged risk factor. During the last decades, research on the metabotropic glutamate receptor (mGlu) system advanced dramatically and much attention was given to the role of the metabotropic glutamate receptor subtype 7 (mGlu7) in acute stress-related behavior and physiology. However, virtually nothing is known about the potential involvement of mGlu7 in chronic psychosocial stress-related conditions. Using the chronic subordinate colony housing (CSC, 19 days) in male mice, we addressed whether central mGlu7 is altered upon chronic psychosocial stressor exposure and whether genetic ablation of mGlu7 interferes with the multitude of chronic stress-induced alterations. CSC exposure resulted in a downregulation of mGlu7 mRNA transcript levels in the prefrontal cortex, a brain region relevant for stress-related behaviors and physiology. Interestingly, mGlu7 deficiency relieved multiple chronic stress-induced alterations including the CSC-induced anxiety-prone phenotype; mGlu7 ablation also ameliorated CSC-induced physiological and immunological consequences such as hypothalamo-pituitary-adrenal (HPA) axis dysfunctions and colonic inflammation, respectively. Together, our findings provide first evidence for the involvement of mGlu7 in a wide range of behavioral and physiological alterations in response to chronic psychosocial stressor exposure. Moreover, the stress-protective phenotype of genetic mGlu7 ablation suggests mGlu7 pharmacological blockade to be a relevant option for the treatment of chronic stress-related emotional and somatic dysfunctions.

  8. Developmental decline in modulation of glutamatergic synapses in layer IV of the barrel cortex by group II metabotropic glutamate receptors.

    PubMed

    Mateo, Z; Porter, J T

    2015-04-02

    Previously, we demonstrated that group II metabotropic glutamate receptors (mGluRs) reduce glutamate release from thalamocortical synapses during early postnatal development (P7-11). To further examine the role of group II mGluRs in the modulation of somatosensory circuitry, we determined whether group II mGluRs continue to modulate thalamocortical synapses until adulthood and whether these receptors also modulate intra-cortical synapses in the barrel cortex. To address these issues, we examined the effect of the group II mGluR agonists on thalamocortical excitatory postsynaptic currents (EPSCs) and intra-barrel EPSCs in slices from animals of different ages (P7-53). We found that the depression of thalamocortical EPSCs by group II mGluRs rapidly declined after the second postnatal week. In contrast, adenosine continued to depress thalamocortical EPSCs via a presynaptic mechanism in young adult mice (P30-50). Activation of group II mGluRs also reduced intra-barrel EPSCs through a postsynaptic mechanism in young mice (P7-11). Similar to the thalamocortical synapses, the group II mGluR modulation of intra-barrel excitatory synapses declined with development. In young adult animals (P30-50), group II mGluR stimulation had little effect on intra-barrel EPSCs but did hyperpolarize the neurons. Together our results demonstrate that group II mGluRs modulate barrel cortex circuitry by presynaptic and postsynaptic mechanisms depending on the source of the synapse and that this modulation declines with development.

  9. In vivo ketamine-induced changes in [11C]ABP688 binding to metabotropic glutamate receptors subtype 5

    PubMed Central

    DeLorenzo, Christine; DellaGioia, Nicole; Bloch, Michael; Sanacora, Gerard; Nabulsi, Nabeel; Abdallah, Chadi; Yang, Jie; Wen, Ruofeng; Mann, J. John; Krystal, John H.; Parsey, Ramin V.; Carson, Richard E.; Esterlis, Irina

    2014-01-01

    Background At subanesthetic doses, ketamine, an N-Methyl-D-aspartate (NMDA) glutamate receptor antagonist, increases glutamate release. Here, we imaged the acute effect of ketamine on brain metabotropic glutamatergic receptors subtype 5 (mGluR5) with a high affinity PET ligand [11C]ABP688 ((E)-3-((6-methylpyridin-2-yl)ethynyl)-cyclohex-2-enone-O-11C-methyl-oxime), a negative allosteric modulator of mGluR5. Methods Ten healthy nonsmoking human volunteers (34±13 years old) received two [11C]ABP688 PET scans on the same day – before (scan 1) and during i.v. ketamine administration (0.23mg/kg over 1min, then 0.58mg/kg over 1h; scan 2). PET data were acquired for 90 min immediately following [11C]ABP688 bolus injection. Input functions were obtained through arterial blood sampling with metabolite analysis. Results A significant reduction in [11C]ABP688 volume of distribution (VT) was observed in scan 2 relative to scan 1 of 21.3 ± 21.4%, on average, in the anterior cingulate, medial prefrontal cortex, orbital prefrontal cortex, ventral striatum, parietal lobe, dorsal putamen, dorsal caudate, amygdala, and hippocampus. There was a significant increase in measurements of dissociative state after ketamine initiation (p<0.05) that resolved after completion of the scan. Discussion This study provides first evidence that ketamine administration decreases [11C]ABP688 binding in vivo in human subjects. Results suggest that [11C]ABP688 binding is sensitive to ketamine-induced effects, although the high individual variation in ketamine response requires further examination. PMID:25156701

  10. Metabotropic Glutamate Receptor 5 Antagonism with Fenobam: Examination of Analgesic Tolerance and Side Effect Profile in Mice

    PubMed Central

    Montana, Michael C.; Conrardy, Beth A.; Cavallone, Laura F.; Kolber, Benedict J.; Rao, Leslie K.; Greco, Suellen C.; Gereau, Robert W.

    2011-01-01

    Background The metabotropic glutamate receptor 5 noncompetitive antagonist fenobam is analgesic in rodents. Future development of fenobam as an analgesic in humans will require a favorable long-term treatment profile and a lack of significant deleterious side effects. This study aimed to determine if tolerance to fenobam’s analgesic effects developed over 14 days and to assess for side effects in mice. Methods Mouse models of pain, locomotor behavior, and coordination were used. Fenobam or vehicle (n = 8 or 11 per group) was administered for 14 days and analgesic tolerance to fenobam was assessed using the formalin test. Histopathology examination and serum chemistry analysis post-14-day fenobam administration were also assessed (n = 12 or 9). The effects of fenobam on locomotor activity were assessed in the open field and elevated zero maze (n = 8 or 7). Coordination was assessed using ledge crossing and vertical pole descent tasks (n = 11 or 10). Results Tolerance to fenobam’s analgesic effect did not develop after 14 days. Chronic fenobam administration resulted in statistically significantly less weight gain compared to vehicle controls, but did not cause any physiologically or statistically significant hematological abnormalities, altered organ function, or abnormal histopathology of the liver, brain, or testes. Fenobam administration resulted in a metabotropic glutamate receptor 5-dependent increase in exploratory behavior but does not impair motor coordination at analgesic doses. Conclusions Analgesic tolerance to repeat fenobam dosing does not develop. Chronic dosing of up to 14-days is well tolerated. Fenobam represents a promising candidate for the treatment of human pain conditions. PMID:22037639

  11. Development of 1H-Pyrazolo[3,4-b]pyridines as Metabotropic Glutamate Receptor 5 Positive Allosteric Modulators.

    PubMed

    Hill, Matthew D; Fang, Haiquan; Brown, Jeffrey M; Molski, Thaddeus; Easton, Amy; Han, Xiaojun; Miller, Regina; Hill-Drzewi, Melissa; Gallagher, Lizbeth; Matchett, Michele; Gulianello, Michael; Balakrishnan, Anand; Bertekap, Robert L; Santone, Kenneth S; Whiterock, Valerie J; Zhuo, Xiaoliang; Bronson, Joanne J; Macor, John E; Degnan, Andrew P

    2016-12-08

    The metabotropic glutamate receptor 5 (mGluR5) is an attractive target for the treatment of schizophrenia due to its role in regulating glutamatergic signaling in association with the N-methyl-d-aspartate receptor (NMDAR). We describe the synthesis of 1H-pyrazolo[3,4-b]pyridines and their utility as mGluR5 positive allosteric modulators (PAMs) without inherent agonist activity. A facile and convergent synthetic route provided access to a structurally diverse set of analogues that contain neither the aryl-acetylene-aryl nor aryl-methyleneoxy-aryl elements, the predominant structural motifs described in the literature. Binding studies suggest that members of our new chemotype do not engage the receptor at the MPEP and CPPHA mGluR5 allosteric sites. SAR studies culminated in the first non-MPEP site PAM, 1H-pyrazolo[3,4-b]pyridine 31 (BMT-145027), to improve cognition in a preclinical rodent model of learning and memory.

  12. Effects of NMDA and non-NMDA ionotropic glutamate receptors in the medial preoptic area on body temperature in awake rats.

    PubMed

    Sengupta, Trina; Jaryal, Ashok Kumar; Mallick, Hruda Nanda

    2016-10-01

    Glutamate when microinjected at the medial preoptic area (mPOA) influences brain temperature (Tbr) and body temperature (Tb) in rats. Glutamate and its various receptors are present at the mPOA. The aim of this study was to identify the contribution of each of the ionotropic glutamatergic receptors at the mPOA on changes in Tbr and Tb in freely moving rats. Adult male Wistar rats (n=40) were implanted with bilateral guide cannula with indwelling styli above the mPOA. A telemetric transmitter was implanted at the peritoneum to record Tb and locomotor activity (LMA). A precalibrated thermocouple wire implanted near the hypothalamus was used to assess Tbr. Specific agonist for each ionotropic glutamate receptor was microinjected into the mPOA and its effects on temperature and LMA were measured in the rats. The rats were also microinjected with the respective ionotropic receptor antagonists, 15min prior to the microinjection of each agonist. Amongst amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), N-methyl-d-aspartate (NMDA) and kainic acid, AMPA increased Tb and LMA when injected at the mPOA. Specific antagonists for AMPA receptors was able to attenuate this increase (p<0.005). Pharmacological blockade of NMDA was able to lower Tbr only. Microinjection of kainic acid and its antagonist had no effect on the variables. The finding of the study suggests that activation of the AMPA receptors at the mPOA, leads to the rise in body temperature.

  13. The sorting receptor SorCS3 is a stronger regulator of glutamate receptor functions compared to GABAergic mechanisms in the hippocampus.

    PubMed

    Christiansen, Gitte B; Andersen, Katrine H; Riis, Sarah; Nykjaer, Anders; Bolcho, Ulrik; Jensen, Morten S; Holm, Mai Marie

    2017-03-01

    Correct function of glutamate receptors in the postsynaptic density is crucial to synaptic function and plasticity. SorCS3 (sortilin-related receptor CNS expressed 3) is a sorting receptor which previously has been shown to interact with the key postsynaptic proteins; PSD-95 and PICK1. In this study, we employed electrophysiological analyses of acute brain slices combined with immunohistochemistry to define the role of SorCS3 in hippocampal synapses in CA1 and the dentate gyrus. We analyzed a juvenile (P17-21) and a young adult (P55-65) group of animals from a Sorcs3 knockout mouse model. We show that the basal synaptic transmission is severely affected in SorCS3-deficient neurons in CA1, while only slightly reduced in the dentate gyrus. Specifically, input/output curves of CA1 synapses revealed a 20% reduction of fEPSP (field excitatory postsynaptic potential) slopes at the highest stimulation intensity in knockouts of the juvenile group, which developed to a 33% decrease in young adult animals. These impairments may be a result of changes in the postsynaptic AMPA receptors. Interestingly, repetitive afferent stimulation demonstrated that SorCS3-deficient slices respond with an enhanced synaptic facilitation and reduced synaptic depression. These changes also developed with age. A molecular mechanism underlying this relative increase during repetitive stimulations is compatible with enhanced mobility of postsynaptic AMPA receptors resulting in faster exchange of desensitized receptors in the postsynaptic density. The altered response during repetitive stimulation was characteristic for CA1 but not the dentate gyrus. Immunohistochemical analyses of parvalbumin positive neurons combined with paired-pulse tests of network inhibition and patch-clamp recordings only showed minute inhibitory changes in SorCS3-deficient slices. Our results suggest that SorCS3 serves an important role in the postsynaptic protein network, which is more pronounced in CA1 compared to the

  14. Group II metabotropic glutamate receptor type 2 allosteric potentiators prevent sodium lactate-induced panic-like response in panic-vulnerable rats

    PubMed Central

    Johnson, Philip L; Fitz, Stephanie D; Engleman, Eric A; Svensson, Kjell A; Schkeryantz, Jeffrey M; Shekhar, Anantha

    2015-01-01

    Rats with chronic inhibition of GABA synthesis by infusion of l-allyglycine, a glutamic acid decarboxylase inhibitor, into their dorsomedial/perifornical hypothalamus are anxious and exhibit panic-like cardio-respiratory responses to treatment with intravenous (i.v.) sodium lactate (NaLac) infusions, in a manner similar to what occurs in patients with panic disorder. We previously showed that either NMDA receptor antagonists or metabotropic glutamate receptor type 2/3 receptor agonists can block such a NaLac response, suggesting that a glutamate mechanism is contributing to this panic-like state. Using this animal model of panic, we tested the efficacy of CBiPES and THIIC, which are selective group II metabotropic glutamate type 2 receptor allosteric potentiators (at 10–30mg/kg i.p.), in preventing NaLac-induced panic-like behavioral and cardiovascular responses. The positive control was alprazolam (3mg/kg i.p.), a clinically effective anti-panic benzodiazepine. As predicted, panic-prone rats given a NaLac challenge displayed NaLac-induced panic-like cardiovascular (i.e. tachycardia and hypertensive) responses and “anxiety” (i.e. decreased social interaction time) and “flight” (i.e. increased locomotion) -associated behaviors; however, systemic injection of the panic-prone rats with CBiPES, THIIC or alprazolam prior to the NaLac dose blocked all NaLac-induced panic-like behaviors and cardiovascular responses. These data suggested that in a rat animal model, selective group II metabotropic glutamate type 2 receptor allosteric potentiators show an anti-panic efficacy similar to alprazolam. PMID:22914798

  15. Metabotropic Glutamate Receptors Induce a Form of LTP Controlled by Translation and Arc Signaling in the Hippocampus

    PubMed Central

    Wang, Hui; Ardiles, Alvaro O.; Yang, Sunggu; Tran, Trinh; Posada-Duque, Rafael; Valdivia, Gonzalo; Baek, Min; Chuang, Yang-An; Palacios, Adrian G.; Gallagher, Michela; Worley, Paul

    2016-01-01

    Activity-dependent bidirectional modifications of excitatory synaptic strength are essential for learning and storage on new memories. Research on bidirectional synaptic plasticity has largely focused on long-term potentiation (LTP) and long-term depression (LTD) mechanisms that rely on the activation of NMDA receptors. In principle, metabotropic glutamate receptors (mGluRs) are also suitable to convert synaptic activity into intracellular signals for synaptic modification. Indeed, dysfunction of a form of LTD that depends on Type I mGluRs (mGluR-LTD), but not NMDARs, has been implicated in learning deficits in aging and mouse models of several neurological conditions, including Fragile X syndrome and Alzheimer's disease. To determine whether mGluR activation can also induce LTP in the absence of NMDAR activation, we examined in hippocampal slices from rats and mice, an NMDAR-independent form of LTP previously characterized as dependent on voltage-gated Ca2+ channels. We found that this form of LTP requires activation of Type I mGluRs and, like mGluR-LTD but unlike NMDAR-dependent plasticity, depends crucially on protein synthesis controlled by fragile X mental retardation protein and on Arc signaling. Based on these observations, we propose the coexistence of two distinct activity-dependent systems of bidirectional synaptic plasticity: one that is based on the activity of NMDARs and the other one based on the activation of mGluRs. SIGNIFICANCE STATEMENT Bidirectional changes of synaptic strength are crucial for the encoding of new memories. Currently, the only activity-dependent mechanism known to support such bidirectional changes are long-term potentiation (LTP) and long-term depression (LTD) forms that relay on the activation of NMDA receptors. Metabotropic glutamate receptors (mGluRs) are, in principle, also suitable to trigger bidirectional synaptic modifications. However, only the mGluR-dependent form of LTD has been characterized. Here we report that an

  16. Involvement of metabotropic glutamate receptor 5 in the inhibition of methamphetamine-associated contextual memory after prolonged extinction training.

    PubMed

    Huang, Chien-Hsuan; Yu, Yang-Jung; Chang, Chih-Hua; Gean, Po-Wu

    2016-04-01

    Addiction is thought to be a memory process between perception and environmental cues and addicted patients often relapse when they come into contact with the drug-related context once again. Here, we used a conditioned place preference protocol to seek a more effective extinction methodology of methamphetamine (METH) memory and delineate its underlying mechanism. Conditioning METH for 3 days in mice markedly increased the time spent in the METH-paired compartment. Then the mice were conditioned with saline for 6 days, from day 6 to day 11, a procedure termed extinction training. However, METH memory returned after a priming injection of METH. We prolonged extinction duration from 6 to 10 days and found that this extensive extinction (EE) training prevented priming effect. At the molecular level, we discovered that prolonged extinction training reversed the METH-conditioned place preference-induced increase in surface expression of GluA2 and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)/NMDA ratio in the basolateral amygdala. In addition, we found that extinction with metabotropic glutamate receptor 5 (mGluR5) activation had similar results to EE: reduced relapse after extinction, decreased synaptic AMPA receptors AMPARs and the AMPA/NMDA ratio. On the contrary, EE with mGluR5 inhibition suppressed the results of EE. These data indicate that EE training-elicited inhibition of METH-primed reinstatement is mediated by the mGluR5. Conditioning mice with methamphetamine place preference (METH CPP) increases surface expression of AMPA receptors (AMPARs) in the basolateral amygdala. We found prolongation of extinction duration from 6 to 10 days prevented priming effect. At the molecular level, we discovered that extensive extinction (EE) reversed the METH CPP-induced increase in surface expression of GluA2 and AMPA/NMDA ratio. In addition, we found that extinction with the metabotropic glutamate receptor 5 (mGluR5) activation had similar results to EE

  17. Blockade of the N-Methyl-D-Aspartate Glutamate Receptor Ameliorates Lipopolysaccharide-Induced Renal Insufficiency

    PubMed Central

    Huang, Ho-Shiang; Ma, Ming-Chieh

    2015-01-01

    N-methyl-D-aspartate (NMDA) receptor activation in rat kidney reduces renal perfusion and ultrafiltration. Hypoperfusion-induced ischemia is the most frequent cause of functional insufficiency in the endotoxemic kidney. Here, we used non-hypotensive rat model of lipopolysaccharide-induced endotoxemia to examine whether NMDA receptor hyperfunction contributes to acute kidney injury. Lipopolysaccharide-induced renal damage via increased enzymuria and hemodynamic impairments were ameliorated by co-treatment with the NMDA receptor blocker, MK-801. The NMDA receptor NR1 subunit in the rat kidney mainly co-localized with serine racemase, an enzyme responsible for synthesizing the NMDA receptor co-agonist, D-serine. The NMDA receptor hyperfunction in lipopolysaccharide-treated kidneys was demonstrated by NR1 and serine racemase upregulation, particularly in renal tubules, and by increased D-serine levels. Lipopolysaccharide also induced cell damage in cultured tubular cell lines and primary rat proximal tubular cells. This damage was mitigated by MK-801 and by small interfering RNA targeting NR1. Lipopolysaccharide increased cytokine release in tubular cell lines via toll-like receptor 4. The release of interleukin-1β from these cells are the most abundant. An interleukin-1 receptor antagonist not only attenuated cell death but also abolished lipopolysaccharide-induced NR1 and serine racemase upregulation and increases in D-serine secretion, suggesting that interleukin-1β-mediated NMDA receptor hyperfunction participates in lipopolysaccharide-induced tubular damage. The results of this study indicate NMDA receptor hyperfunction via cytokine effect participates in lipopolysaccharide-induced renal insufficiency. Blockade of NMDA receptors may represent a promising therapeutic strategy for the treatment of sepsis-associated renal failure. PMID:26133372

  18. The calcium-sensitive Sigma-1 receptor prevents cannabinoids from provoking glutamate NMDA receptor hypofunction: implications in antinociception and psychotic diseases.

    PubMed

    Sánchez-Blázquez, Pilar; Rodríguez-Muñoz, María; Herrero-Labrador, Raquel; Burgueño, Javier; Zamanillo, Daniel; Garzón, Javier

    2014-12-01

    Through the cannabinoid receptor 1 (CB1), the endocannabinoid system plays a physiological role in maintaining the activity of glutamate N-methyl-D-aspartate (NMDA) receptor within harmless limits. The influence of cannabinoids must be proportional to the stimulus in order to prevent NMDAR overactivation or exaggerated hypofunction that may precipitate symptoms of psychosis. In this framework, the recently reported association of CB1s with NMDARs, which mediates the reduction of cannabinoid analgesia promoted by NMDAR antagonism, could also support the precipitation of schizophrenia brought about by the abuse of smoked cannabis, mostly among vulnerable individuals. Accordingly, we have investigated this possibility using neuroprotection and analgesia as reporters of the CB1-NMDAR connection. We found that the Sigma 1 receptor (σ1R) acts as a safety switch, releasing NMDARs from the influence of CB1s and thereby avoiding glutamate hypofunction. In σ1R(-/-) mice the activity of NMDARs increases and cannot be regulated by cannabinoids, and NMDAR antagonism produces no effect on cannabinoid analgesia. In wild-type mice, ligands of the σ1R did not affect the CB1-NMDAR regulatory association, however, experimental NMDAR hypofunction enabled σ1R antagonists to release NMDARs from the negative control of CB1s. Of the σ1R antagonists tested, their order of activity was: S1RA > BD1047 ≫ NE100 = BD1063, although SKF10047, PRE-084 and (+)pentazocine were inactive yet able to abolish the effect of S1RA in this paradigm. Thus, the σ1R controls the extent of CB1-NMDAR interaction and its failure might constitute a vulnerability factor for cannabis abuse, potentially precipitating schizophrenia that might otherwise be induced later in time by the endogenous system.

  19. Translational Pharmacology of the Metabotropic Glutamate 2 Receptor-Preferring Agonist LY2812223 in the Animal and Human Brain.

    PubMed

    Felder, Christian C; Schober, Douglas A; Tu, Yuan; Quets, Anne; Xiao, Hongling; Watt, Marla; Siuda, Ed; Nisenbaum, Eric; Xiang, Chuanxi; Heinz, Beverly; Prieto, Lourdes; McKinzie, David L; Monn, James A

    2017-04-01

    LY2812223 [(1R,2S,4R,5R,6R)-2-amino-4-(1H-1,2,4-triazol-3-ylsulfanyl)bicyclo[3.1.0]hexane-2,6-dicarboxylic acid] was identified via structure-activity studies arising from the potent metabotropic glutamate mGlu2/3 receptor agonist LY354740 [(+)-2-aminobicyclo[3.1.0] hexane-2,6-dicarboxylic acid] as an mGlu2-preferring agonist. This pharmacology was determined using stably transfected cells containing either the human mGlu2 or mGlu3 receptor. We extended the pharmacological evaluation of LY2812223 to native brain tissues derived from relevant species used for preclinical drug development as well as human postmortem brain tissue. This analysis was conducted to ensure pharmacological translation from animals to human subjects in subsequent clinical studies. A guanosine 5'-O-(3-[(35)S]thio)triphosphate (GTPγS) functional binding assay, a method for measuring Gi-coupled signaling that is inherent to the group 2 mGlu receptors, was used to evaluate LY2812223 pharmacology of native mGlu receptors in mouse, rat, nonhuman primate, and human cortical brain tissue samples. In native tissue membranes, LY2812223 unexpectedly acted as a partial agonist across all species tested. Activity of LY2812223 was lost in cortical membranes collected from mGlu2 knockout mice, but not those from mGlu3 knockout mice, providing additional support for mGlu2-preferring activity. Other signal transduction assays were used for comparison with the GTP binding assay (cAMP, calcium mobilization, and dynamic mass redistribution). In ectopic cell line-based assays, LY2812223 displayed near maximal agonist responses at the mGlu2 receptor across all assay formats, while it showed no functional agonist activity at the mGlu3 receptor except in the cAMP assay. In native brain slices or membranes that express both mGlu2 and mGlu3 receptors, LY2812223 displayed unexpected partial agonist activity, which may suggest a functional interplay between these receptor subtypes in the brain.

  20. The Amino Acid Transporter JhI-21 Coevolves with Glutamate Receptors, Impacts NMJ Physiology, and Influences Locomotor Activity in Drosophila Larvae.

    PubMed

    Ziegler, Anna B; Augustin, Hrvoje; Clark, Nathan L; Berthelot-Grosjean, Martine; Simonnet, Mégane M; Steinert, Joern R; Geillon, Flore; Manière, Gérard; Featherstone, David E; Grosjean, Yael

    2016-01-25

    Changes in synaptic physiology underlie neuronal network plasticity and behavioral phenomena, which are adjusted during development. The Drosophila larval glutamatergic neuromuscular junction (NMJ) represents a powerful synaptic model to investigate factors impacting these processes. Amino acids such as glutamate have been shown to regulate Drosophila NMJ physiology by modulating the clustering of postsynaptic glutamate receptors and thereby regulating the strength of signal transmission from the motor neuron to the muscle cell. To identify amino acid transporters impacting glutmatergic signal transmission, we used Evolutionary Rate Covariation (ERC), a recently developed bioinformatic tool. Our screen identified ten proteins co-evolving with NMJ glutamate receptors. We selected one candidate transporter, the SLC7 (Solute Carrier) transporter family member JhI-21 (Juvenile hormone Inducible-21), which is expressed in Drosophila larval motor neurons. We show that JhI-21 suppresses postsynaptic muscle glutamate receptor abundance, and that JhI-21 expression in motor neurons regulates larval crawling behavior in a developmental stage-specific manner.

  1. Synaptic fusion pore structure and AMPA receptor activation according to Brownian simulation of glutamate diffusion.

    PubMed

    Ventriglia, Francesco; Maio, Vito Di

    2003-03-01

    The rising phase of fast, AMPA-mediated Excitatory Post Synaptic Currents (EPSCs) has a primary role in the computational ability of neurons. The structure and radial expansion velocity of the fusion pore between the vesicle and the presynaptic membrane could be important factors in determining the time course of the EPSC. We have used a Brownian simulation model for glutamate neurotransmitter diffusion to test two hypotheses on the fusion pore structure, namely, the proteinaceous pore and the purely lipidic pore. Three more hypotheses on the radial expansion velocity were also tested. The rising phases of the EPSC, computed under various conditions, were compared with experimental data from the literature. Our present results show that a proteinaceous fusion pore should produce a more marked foot at the beginning of the rising phase of the EPSC. They also confirm the hypothesis that the structure of the fusion pore and its radial expansion velocity play significant roles in shaping the fast EPSC time course.

  2. Activation of metabotropic glutamate receptors regulates ribosomes of cochlear nucleus neurons.

    PubMed

    Carzoli, Kathryn L; Hyson, Richard L

    2014-01-01

    The brain stem auditory system of the chick is an advantageous model for examining changes that occur as a result of deafness. Elimination of acoustic input through cochlear ablation results in the eventual death of approximately 30% of neurons in the chick cochlear nucleus, nucleus magnocellularis (NM). One early change following deafness is an alteration in NM ribosomes, evidenced both by a decrease in protein synthesis and reduction in antigenicity for Y10B, a monoclonal antibody that recognizes a ribosomal epitope. Previous studies have shown that mGluR activation is necessary to maintain Y10B antigenicity and NM viability. What is still unclear, however, is whether or not mGluR activation is sufficient to prevent deafness-induced changes in these neurons, or if other activity-dependent factors are also necessary. The current study investigated the ability of mGluR activation to regulate cochlear nucleus ribosomes in the absence of auditory nerve input. In vitro methods were employed to periodically pressure eject glutamate or mGluR agonists over neurons on one side of a slice preparation leaving the opposite side of the same slice untreated. Immunohistochemistry was then performed using Y10B in order to assess ribosomal changes. Application of glutamate and both group I and II selective mGluR agonists effectively rescued ribosomal antigenicity on the treated side of the slice in comparison to ribosomes on the untreated side. These findings suggest that administration of mGluR agonists is sufficient to reduce the early interruption of normal ribosomal integrity that is typically seen following loss of auditory nerve activity.

  3. Modulation of intracellular calcium mobilization and GABAergic currents through subtype-specific metabotropic glutamate receptors in neonatal rat hippocampus.

    PubMed

    Taketo, M; Matsuda, H

    2010-01-15

    Group I metabotropic glutamate receptors (mGluRs) are coupled to phosphoinositide hydrolysis, and are thought to modulate neuronal excitability, by mobilizing intracellular Ca(2+). Difference in Ca(2+) mobilization among subclasses of the receptors has been reported, and regarded as a possible cause of variant neuronal modifications. In hippocampal interneurons, several subclasses of mGluRs including mGluR1 and mGluR5 have been immunohistochemically identified. The subclass-specific physiological effects of mGluRs on neuronal transmission in hippocampus, however, have not been fully elucidated. In the present study, effects of group I mGluR agonist, (S)-3,5-dihydroxyphenylglycine (DHPG) on intracellular calcium concentration were examined in hippocampal interneurons. Application of DHPG increased fluorescence ratio in neonatal CA3 stratum oriens/alveus interneurons. The DHPG-induced calcium mobilization was markedly inhibited by mGluR1-specific antagonist, cyclopropan[b]chromen-1a-carboxylate (CPCCOEt). Inhibition of the calcium elevation by mGluR5-specific antagonist, 6-methyl-2-(phenylazo)-3-pyrindol (MPEP), was weaker than that of CPCCOEt. The fluorescence ratio was not significantly changed by application of mGluR5-specific agonist, (RS)-2-chloro-5-hydroxyphenylglycine (CHPG). DHPG induced calcium responses in CA1 interneurons as in CA3, and the responses were partially inhibited by MPEP treatment. Effects of group I mGluR agonist and antagonist were also investigated, on GABA(A) receptor-mediated spontaneous inhibitory postsynaptic currents (sIPSCs) in CA3 pyramidal neurons. The GABAergic sIPSCs were facilitated by DHPG perfusion, and the potentiation was reduced by CPCCOEt, and less distinctly by MPEP. The sIPSCs were not significantly potentiated by CHPG application. These results indicate that mGluR1 is functional in hippocampal interneurons, and DHPG exerts its effect mainly through this receptor at early developmental period.

  4. Molecular determinants of agonist selectivity in glutamate-gated chloride channels which likely explain the agonist selectivity of the vertebrate glycine and GABAA-ρ receptors.

    PubMed

    Blarre, Thomas; Bertrand, Hugues-Olivier; Acher, Francine C; Kehoe, JacSue

    2014-01-01

    Orthologous Cys-loop glutamate-gated chloride channels (GluClR's) have been cloned and described electrophysiologically and pharmacologically in arthropods and nematodes (both members of the invertebrate ecdysozoan superphylum). Recently, GluClR's from Aplysia californica (a mollusc from the lophotrochozoan superphylum) have been cloned and similarly studied. In spite of sharing a common function, the ecdysozoan and lophotrochozoan receptors have been shown by phylogenetic analyses to have evolved independently. The recent crystallization of the GluClR from C. elegans revealed the binding pocket of the nematode receptor. An alignment of the protein sequences of the nematode and molluscan GluClRs showed that the Aplysia receptor does not contain all of the residues defining the binding mode of the ecdysozoan receptor. That the two receptors have slightly different binding modes is not surprising since earlier electrophysiological and pharmacological experiments had suggested that they were differentially responsive to certain agonists. Knowledge of the structure of the C. elegans GluClR has permitted us to generate a homology model of the binding pocket of the Aplysia receptor. We have analyzed the differences between the two binding modes and evaluated the relative significance of their non-common residues. We have compared the GluClRs electrophysiologically and pharmacologically and we have used site-directed mutagenesis on both receptor types to test predictions made from the model. Finally, we propose an explanation derived from the model for why the nematode receptors are gated only by glutamate, whereas the molluscan receptors can also be activated by β-alanine, GABA and taurine. Like the Aplysia receptor, the vertebrate glycine and GABAA-ρ receptors also respond to these other agonists. An alignment of the sequences of the molluscan and vertebrate receptors shows that the reasons we have given for the ability of the other agonists to activate the Aplysia

  5. Protection by imidazol(ine) drugs and agmatine of glutamate-induced neurotoxicity in cultured cerebellar granule cells through blockade of NMDA receptor

    PubMed Central

    Olmos, Gabriel; DeGregorio-Rocasolano, Nuria; Regalado, M Paz; Gasull, Teresa; Boronat, M Assumpció; Trullas, Ramón; Villarroel, Alvaro; Lerma, Juan; García-Sevilla, Jesús A

    1999-01-01

    This study was designed to assess the potential neuroprotective effect of several imidazol(ine) drugs and agmatine on glutamate-induced necrosis and on apoptosis induced by low extracellular K+ in cultured cerebellar granule cells.Exposure (30 min) of energy deprived cells to L-glutamate (1–100 μM) caused a concentration-dependent neurotoxicity, as determined 24 h later by a decrease in the ability of the cells to metabolize 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT) into a reduced formazan product. L-glutamate-induced neurotoxicity (EC50=5 μM) was blocked by the specific NMDA receptor antagonist MK-801 (dizocilpine).Imidazol(ine) drugs and agmatine fully prevented neurotoxicity induced by 20 μM (EC100) L-glutamate with the rank order (EC50 in μM): antazoline (13)>cirazoline (44)>LSL 61122 [2-styryl-2-imidazoline] (54)>LSL 60101 [2-(2-benzofuranyl) imidazole] (75)>idazoxan (90)>LSL 60129 [2-(1,4-benzodioxan-6-yl)-4,5-dihydroimidazole] (101)>RX821002 (2-methoxy idazoxan) (106)>agmatine (196). No neuroprotective effect of these drugs was observed in a model of apoptotic neuronal cell death (reduction of extracellular K+) which does not involve stimulation of NMDA receptors.Imidazol(ine) drugs and agmatine fully inhibited [3H]-(+)-MK-801 binding to the phencyclidine site of NMDA receptors in rat brain. The profile of drug potency protecting against L-glutamate neurotoxicity correlated well (r=0.90) with the potency of the same compounds competing against [3H]-(+)-MK-801 binding.In