RESUMEN

Ionotropic glutamate receptors (iGluRs) function as glutamate-activated ion channels in rapid synaptic transmission in animals. Arabidopsis thaliana possess 20 glutamate receptor-like genes (AtGLRs) in its genome which are involved in many functions including light signal transduction and calcium homeostasis. However, little is known about the physico-chemical, functional and structural properties of AtGLRs. In this study, glutamate receptor-like genes of A. thaliana have been studied in silico. Exon-intron structures revealed common origin of majority of these genes. The presence of several phosphorylation and myristoilation sites indicate the involvement of AtGLRs in various signaling processes. Gene ontology analysis showed the participation of AtGLRs in various biological processes including different stress responses. In two genes namely AT2G17260 and AT4G35290, presence of RAV1-A binding site motif in the promoter coupled with results from gene ontology annotation indicate their role in stomatal movement through abscisic acid signaling. Expression analysis showed differential expression of several tandemly arranged genes which indicates neo or sub-functionalization. Two genes namely AT5G48400 and AT5G48410 showed significantly more expression in response to Botrytis cinerea infection. Five of these genes have shown G-protein-coupled γ-aminobutyric acid (GABA) receptor activity indicating a possible interaction between AtGLRs and GABA. Structurally, all of them were similar while differences were found regarding electrostatic surfaces as well as surface hydrophobicity. Results of this study provide a comprehensive reference regarding AtGLRs for further analysis regarding the structure, function, and evolution of the glutamate receptors in plants.

Asunto(s)

Proteínas de Arabidopsis/genética , Simulación por Computador , Familia de Multigenes , Receptores de Glutamato/genética , Secuencia de Aminoácidos , Arabidopsis/genética , Arabidopsis/metabolismo , Arabidopsis/microbiología , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/clasificación , Botrytis/fisiología , Mapeo Cromosómico , Cromosomas de las Plantas/genética , Regulación de la Expresión Génica de las Plantas , Ontología de Genes , Modelos Moleculares , Filogenia , Conformación Proteica , Receptores de Glutamato/química , Receptores de Glutamato/clasificación , Homología de Secuencia de Aminoácido , Transducción de Señal/genética

RESUMEN

Ambient glutamate plays an important role in pathological conditions, such as stroke, but its role during normal activity is not clear. In addition, it is not clear how ambient glutamate acts on glutamate receptors with varying affinities or subcellular localizations. To address this, we studied "endbulb of Held" synapses, which are formed by auditory nerve fibers onto bushy cells (BCs) in the anteroventral cochlear nucleus. When ambient glutamate was increased by applying the glutamate reuptake inhibitor TFB-TBOA, BCs depolarized as a result of activation of N-methyl-D-aspartate receptors (NMDARs) and group I metabotropic glutamate receptors (mGluRs). Application of antagonists against NMDARs (in 0 Mg(2+)) or mGluRs caused hyperpolarization, indicating that these receptors were bound by a tonic source of glutamate. AMPA receptors did not show these effects, consistent with their lower glutamate affinity. We also evaluated the subcellular localization of the receptors activated by ambient glutamate. The mGluRs were not activated by synaptic stimulation and thus appear to be exclusively extrasynaptic. By contrast, NMDARs in both synaptic and extrasynaptic compartments were activated by ambient glutamate, as shown using the use-dependent antagonist MK-801. Levels of ambient glutamate appeared to be regulated in a spike-independent manner, and glia likely play a major role. These low levels of ambient glutamate likely have functional consequences, as even low concentrations of TBOA caused significant increases in BC spiking following synaptic stimulation. These results indicate that normal resting potential appears to be poised in the region of maximal sensitivity to small changes in ambient glutamate.

Asunto(s)

Potenciales de Acción/efectos de los fármacos , Núcleo Coclear/citología , Fármacos actuantes sobre Aminoácidos Excitadores/farmacología , Ácido Glutámico/farmacología , Receptores de Glutamato/metabolismo , Envejecimiento , Animales , Animales Recién Nacidos , Núcleo Coclear/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Interacciones Farmacológicas , Técnicas In Vitro , Ratones , Ratones Endogámicos CBA , Receptores de Glutamato/clasificación , Bloqueadores de los Canales de Sodio/farmacología , Tetrodotoxina/farmacología

RESUMEN

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 responses that contribute to plateau depolarizations. CONCLUSIONS: As it has been established in previous physiological studies in vivo, synaptic invasion over different latencies, spanning hundreds of milliseconds after a single stimulus strongly indicates convergent polysynaptic activation. Interconnected cortical neurons converging on the same SPNs may explain prolonged corticostriatal responses. Glutamate receptors participation in these responses is described as well as differences and similarities between dSPNs and iSPNs.

Asunto(s)

Corteza Cerebral/citología , Cuerpo Estriado/citología , Vías Nerviosas/fisiología , Neuronas/fisiología , Receptores de Glutamato/metabolismo , Sinapsis/metabolismo , Animales , Bicuculina/farmacología , Biofisica , Estimulación Eléctrica , Fármacos actuantes sobre Aminoácidos Excitadores/farmacología , Antagonistas de Receptores de GABA-A/farmacología , Proteínas Fluorescentes Verdes/genética , Proteínas Fluorescentes Verdes/metabolismo , Técnicas In Vitro , Ratones , Ratones Transgénicos , Técnicas de Placa-Clamp , Ratas , Ratas Wistar , Receptores de Dopamina D1/genética , Receptores de Dopamina D2/genética , Receptores de Glutamato/clasificación , Transmisión Sináptica/efectos de los fármacos , Transmisión Sináptica/fisiología

RESUMEN

Saccoglossus kowalevskii (the acorn worm) is a hemichordate belonging to the superphylum of deuterostome bilateral animals. Hemichordates are sister group to echinoderms, and closely related to chordates. S. kowalevskii has chordate like morphological traits and serves as an important model organism, helping developmental biologists to understand the evolution of the central nervous system (CNS). Despite being such an important model organism, the signalling system repertoire of the largest family of integral transmembrane receptor proteins, G protein-coupled receptors (GPCRs) is largely unknown in S. kowalevskii. Here, we identified 260 unique GPCRs and classified as many as 257 of them into five main mammalian GPCR families; Glutamate (23), Rhodopsin (212), Adhesion (18), Frizzled (3) and Secretin (1). Despite having a diffuse nervous system, the acorn worm contains well conserved orthologues for human Adhesion and Glutamate family members, with a similar N-terminal domain architecture. This is particularly true for genes involved in CNS development and regulation in vertebrates. The average sequence identity between the GPCR orthologues in human and S. kowalevskii is around 47%, and this is same as observed in couple of the closest vertebrate relatives, Ciona intestinalis (41%) and Branchiostoma floridae (~47%). The Rhodopsin family has fewer members than vertebrates and lacks clear homologues for 6 of the 13 subgroups, including olfactory, chemokine, prostaglandin, purine, melanocyte concentrating hormone receptors and MAS-related receptors. However, the peptide and somatostatin binding receptors have expanded locally in the acorn worm. Overall, this study is the first large scale analysis of a major signalling gene superfamily in the hemichordate lineage. The establishment of orthologue relationships with genes involved in neurotransmission and development of the CNS in vertebrates provides a foundation for understanding the evolution of signal transduction and allows for further investigation of the hemichordate neurobiology.

Asunto(s)

Cordados no Vertebrados/genética , Receptores Acoplados a Proteínas G/genética , Vertebrados/genética , Animales , Moléculas de Adhesión Celular/genética , Sistema Nervioso Central/embriología , Sistema Nervioso Central/metabolismo , Cordados no Vertebrados/metabolismo , Evolución Molecular , Humanos , Filogenia , Receptores Acoplados a Proteínas G/clasificación , Receptores Acoplados a Proteínas G/metabolismo , Receptores de Glutamato/clasificación , Receptores de Glutamato/genética , Rodopsina/genética , Rodopsina/metabolismo , Secretina/metabolismo , Vertebrados/metabolismo

RESUMEN

Glutamate is the most abundant excitatory neurotransmitter in the brain, and distinct classes of glutamate receptors coordinate synaptic transmission and spike generation upon various levels of neuronal activity. However, the mechanisms remain unclear. Here, we found that loss of synaptic AMPA receptors increased kainate receptor activity in cerebellar granule cells without changing NMDA receptors. The augmentation of kainate receptor-mediated currents in the absence of AMPA receptor activity is required for spike generation and is mediated by the increased expression of the GluK5 high-affinity kainate receptor subunit. Increase in GluK5 expression is sufficient to enhance kainate receptor activity by modulating receptor channel properties, but not localization. Furthermore, we demonstrate that the combined loss of the AMPA receptor auxiliary TARPγ-2 subunit and the GluK5 subunit leads to early mouse lethality. Our findings reveal mechanisms mediated by distinct classes of postsynaptic glutamate receptors for the homeostatic maintenance of the neuronal activity.

Asunto(s)

Potenciales Evocados/fisiología , Receptores AMPA/deficiencia , Receptores de Ácido Kaínico/fisiología , Potenciales Sinápticos/fisiología , Transmisión Sináptica/fisiología , Adaptación Fisiológica , Animales , Cerebelo/citología , Cerebelo/fisiología , Femenino , Técnicas In Vitro , Masculino , Ratones , Ratones Mutantes , Receptor Cross-Talk/fisiología , Receptores AMPA/fisiología , Receptores de Glutamato/clasificación , Receptores de Glutamato/fisiología , Receptores de N-Metil-D-Aspartato/fisiología , Transducción de Señal

RESUMEN

AvGluR1, a glutamate receptor ion channel from the primitive eukaryote Adineta vaga, is activated by alanine, cysteine, methionine, and phenylalanine, which produce lectin-sensitive desensitizing responses like those to glutamate, aspartate, and serine. AvGluR1 LBD crystal structures reveal an unusual scheme for binding dissimilar ligands that may be utilized by distantly related odorant/chemosensory receptors. Arginine residues in domain 2 coordinate the γ-carboxyl group of glutamate, whereas in the alanine, methionine, and serine complexes a chloride ion acts as a surrogate ligand, replacing the γ-carboxyl group. Removal of Cl(-) lowers affinity for these ligands but not for glutamate or aspartate nor for phenylalanine, which occludes the anion binding site and binds with low affinity. AvGluR1 LBD crystal structures and sedimentation analysis also provide insights into the evolutionary link between prokaryotic and eukaryotic iGluRs and reveal features unique to both classes, emphasizing the need for additional structure-based studies on iGluR-ligand interactions.

Asunto(s)

Cloruros/química , Proteínas del Helminto/química , Canales Iónicos/química , Receptores de Glutamato/química , Rotíferos/química , Secuencia de Aminoácidos , Aminoácidos/química , Aminoácidos/metabolismo , Animales , Sitios de Unión , Cloruros/metabolismo , Cristalografía por Rayos X , Escherichia coli/genética , Evolución Molecular , Proteínas del Helminto/clasificación , Proteínas del Helminto/genética , Canales Iónicos/clasificación , Canales Iónicos/genética , Cinética , Ligandos , Simulación de Dinámica Molecular , Datos de Secuencia Molecular , Filogenia , Unión Proteica , Estructura Secundaria de Proteína , Estructura Terciaria de Proteína , Receptores de Glutamato/clasificación , Receptores de Glutamato/genética , Proteínas Recombinantes/química , Proteínas Recombinantes/clasificación , Proteínas Recombinantes/genética , Alineación de Secuencia

RESUMEN

Neuronal ceroid lipofuscinoses (NCLs) are a group of hereditary childhood diseases characterized mainly by lipopigment accumulation and a multisystemic pattern of symptoms including mental retardation, seizures, motor impairment, and blindness. The mnd mouse, carrying a mutation in the Cln8 gene, has been proposed as a model of epilepsy with mental retardation (EPMR, ornorthern epilepsy). We recently showed neuronal hyperexcitability and seizure hypersusceptibility in mnd mice. To elucidate the cellular mechanisms related to hippocampal hyperexcitability, the glutamatergic transmission and the expression of postsynaptic glutamate receptors were investigated in hippocampus. A significant increase in either spontaneous or KCl-stimulated overflow of [³H]D-aspartate was found in mnd mice compared with controls. This increase was maintained after DL-threo-ß-benzyloxyaspartic acid (TBOA) treatment, suggesting a nonrelevant role for transporter-mediated release and supporting the involvement of exocytotic [³H]D-aspartate release. Accordingly, Ca²âº-dependent overflow induced by ionomycin was also increased in mnd mice. Levels of glutamate 1-3 AMPA receptor subunits were increased, and levels of the NR2A NMDA receptor subunit were decreased in the hippocampus of mnd mice, suggesting an adaptive response to glutamate overstimulation.

Asunto(s)

Ácido D-Aspártico/metabolismo , Regulación de la Expresión Génica/genética , Hipocampo/metabolismo , Receptores de Glutamato/metabolismo , Análisis de Varianza , Animales , Ácido Aspártico/farmacología , Astrocitos/efectos de los fármacos , Astrocitos/metabolismo , Ionóforos de Calcio/farmacología , Regulación de la Expresión Génica/efectos de los fármacos , Proteína Ácida Fibrilar de la Glía/metabolismo , Hipocampo/citología , Hipocampo/efectos de los fármacos , Ionomicina/farmacología , Masculino , Proteínas de la Membrana/genética , Ratones , Ratones Endogámicos C57BL , Ratones Mutantes , Cloruro de Potasio/farmacología , Receptores de Glutamato/clasificación , Receptores de Glutamato/genética , Sinaptosomas/metabolismo , Tritio/metabolismo

RESUMEN

Glutamate and gamma-aminobutyric acid (GABA) receptors are mainly expressed in central nervous system and play critical roles in neural signal transduction. It has been demonstrated that glutamate and GABA receptors are also found in pancreatic islets. Interestingly, almost all of glutamate and GABA receptor subunits are present in islets. Here, we summarize current progresses of these receptors in islets, focusing on there expressions, physiological implications, interactions, as well as a novel approach to investigate roles of the receptors in islets slice. All these investigations will potentially supply new understanding of working mechanism of these receptors in islet and also shed a new insight for neuroscientific research.

Asunto(s)

Islotes Pancreáticos/metabolismo , Receptores de GABA/fisiología , Receptores de Glutamato/fisiología , Animales , Humanos , Receptores de GABA/clasificación , Receptores de GABA/metabolismo , Receptores de Glutamato/clasificación , Receptores de Glutamato/metabolismo

RESUMEN

Intraperitoneal injection of CCK reduces food intake and triggers a behavioral pattern similar to natural satiation. Reduction of food intake by CCK is mediated by vagal afferents that innervate the stomach and small intestine. These afferents synapse in the hindbrain nucleus of the solitary tract (NTS) where gastrointestinal satiation signals are processed. Previously, we demonstrated that intraperitoneal (IP) administration of either competitive or noncompetitive N-methyl-d-aspartate (NMDA) receptor antagonists attenuates reduction of food intake by CCK. However, because vagal afferents themselves express NMDA receptors at both central and peripheral endings, our results did not speak to the question of whether NMDA receptors in the brain play an essential role in reduction of feeding by CCK. We hypothesized that activation of NMDA receptors in the NTS is necessary for reduction of food intake by CCK. To test this hypothesis, we measured food intake following IP CCK, subsequent to NMDA receptor antagonist injections into the fourth ventricle, directly into the NTS or subcutaneously. We found that either fourth-ventricle or NTS injection of the noncompetitive NMDA receptor antagonist MK-801 was sufficient to inhibit CCK-induced reduction of feeding, while the same antagonist doses injected subcutaneously did not. Similarly fourth ventricle injection of d-3-(2-carboxypiperazin-4-yl)-1-propenyl-1-phosphoric acid (d-CPPene), a competitive NMDA receptor antagonist, also blocked reduction of food intake following IP CCK. Finally, d-CPPene injected into the fourth ventricle attenuated CCK-induced expression of nuclear c-Fos immunoreactivity in the dorsal vagal complex. We conclude that activation of NMDA receptors in the hindbrain is necessary for the reduction of food intake by CCK. Hindbrain NMDA receptors could comprise a critical avenue for control and modulation of satiation signals to influence food intake and energy balance.

Asunto(s)

Colecistoquinina/farmacología , Ingestión de Alimentos/efectos de los fármacos , Receptores de Glutamato/metabolismo , Rombencéfalo/efectos de los fármacos , Animales , Maleato de Dizocilpina/administración & dosificación , Maleato de Dizocilpina/farmacología , Regulación de la Expresión Génica/fisiología , Genes fos/fisiología , Inyecciones Intraventriculares , Masculino , Piperazinas/administración & dosificación , Piperazinas/farmacología , Ratas , Ratas Sprague-Dawley , Receptores de Glutamato/clasificación , Rombencéfalo/fisiología , Saciedad

RESUMEN

Evidence has accumulated over the past years that dysregulation of glutamatergic neurotransmission maybe implicated in the pathophysiology of schizophrenia. Glutamate acts on two major classes of receptors: ionotropic receptors, which are ligand-gated ion channels, and metabotropic receptors (mGluRs), coupled to heterotrimeric G-proteins. Although several pharmacological evidences point to abnormal glutamatergic transmission in schizophrenia, changes in the expression of glutamatergic receptors in the prefrontal cortex of patients with schizophrenia remains equivocal. In the present work, we have investigated glutamatergic neurotransmission in schizophrenia by assessing the expression in Brodmann Area 10 of mGluR5, the AMPA receptor subunits GluR1 and GluR2, and Na(+)/K(+) ATPase-α1, a potential modulator of glutamate uptake in the brain. Semiquantitative analysis of the expression of these proteins from postmortem brains revealed a particularly prominent reduction of GluR1 and GluR2 expression in patients with schizophrenia vs the control group. Conversely, we observed an up-regulation in the levels of Na(+)/K(+) ATPase-α1 expression. Finally, no change in the protein levels of mGluR5 was observed in schizophrenia. Our findings support and expand the hypothesis of glutamatergic dysfunction in prefrontal cortex in the pathophysiology of schizophrenia.

Asunto(s)

Corteza Prefrontal/metabolismo , Receptores de Glutamato/metabolismo , Esquizofrenia/patología , ATPasa Intercambiadora de Sodio-Potasio/metabolismo , Adulto , Anciano , Anciano de 80 o más Años , Análisis de Varianza , Femenino , Humanos , Masculino , Persona de Mediana Edad , Cambios Post Mortem , Receptores de Glutamato/clasificación , Estadísticas no Paramétricas

RESUMEN

A growing body of evidence indicates that repeated exposure to cocaine leads to profound changes in glutamate transmission in limbic nuclei, particularly the nucleus accumbens. This review focuses on preclinical studies of cocaine-induced behavioral plasticity, including behavioral sensitization, self-administration, and the reinstatement of cocaine seeking. Behavioral, pharmacological, neurochemical, electrophysiological, biochemical, and molecular biological changes associated with cocaine-induced plasticity in glutamate systems are reviewed. The ultimate goal of these lines of research is to identify novel targets for the development of therapies for cocaine craving and addiction. Therefore, we also outline the progress and prospects of glutamate modulators for the treatment of cocaine addiction.

Asunto(s)

Trastornos Relacionados con Cocaína/fisiopatología , Cocaína/toxicidad , Ácido Glutámico/fisiología , Transmisión Sináptica/efectos de los fármacos , Adaptación Fisiológica/efectos de los fármacos , Animales , Conducta Animal/efectos de los fármacos , Conducta Animal/fisiología , Trastornos Relacionados con Cocaína/tratamiento farmacológico , Trastornos Relacionados con Cocaína/psicología , Dopamina/fisiología , Agonistas de Aminoácidos Excitadores/uso terapéutico , Antagonistas de Aminoácidos Excitadores/uso terapéutico , Humanos , Modelos Neurológicos , Plasticidad Neuronal/efectos de los fármacos , Plasticidad Neuronal/fisiología , Núcleo Accumbens/efectos de los fármacos , Núcleo Accumbens/fisiopatología , Ratas , Receptores de Glutamato/clasificación , Receptores de Glutamato/efectos de los fármacos , Receptores de Glutamato/fisiología , Refuerzo en Psicología , Transducción de Señal/efectos de los fármacos , Transducción de Señal/fisiología , Transmisión Sináptica/fisiología

RESUMEN

In the brain of vertebrates, glutamate receptor ion channels (iGluR) mediate fast neurotransmission at excitatory synapses. They exist as distinct subfamilies (AMPA, Kainate and NMDA) differing in their functional properties. Yet, all iGluR are tetramers sharing a common molecular architecture, and a common scheme applies for the general mechanisms of their activation, which are discussed in this review. The dissection of the molecular mechanisms responsible for the operation of iGluR explain how they match their physiological requirements and paves the way to new strategies for pharmacological regulations of these receptors. This could prove useful for the discovery of drugs of therapeutic interest, such as cognitive enhancers, pain killers or anti-psychotics.

Asunto(s)

Receptores de Glutamato/fisiología , Transmisión Sináptica/fisiología , Regulación Alostérica , Cationes , Fármacos del Sistema Nervioso Central/farmacología , Fármacos del Sistema Nervioso Central/uso terapéutico , Dimerización , Diseño de Fármacos , Agonistas de Aminoácidos Excitadores/farmacología , Ácido Glutámico/fisiología , Humanos , Activación del Canal Iónico/efectos de los fármacos , Activación del Canal Iónico/fisiología , Trastornos Mentales/tratamiento farmacológico , Modelos Moleculares , Enfermedades Neurodegenerativas/tratamiento farmacológico , Conformación Proteica , Subunidades de Proteína , Receptores de Glutamato/química , Receptores de Glutamato/clasificación , Receptores de Glutamato/efectos de los fármacos , Receptores Presinapticos/efectos de los fármacos , Receptores Presinapticos/fisiología , Especificidad por Sustrato , Transmisión Sináptica/efectos de los fármacos

RESUMEN

The role of amygdaloid glutamatergic receptors (GluRs) in maintenance of the sensory versus emotional component of neuropathic pain was studied by assessing monofilament-induced limb withdrawal response (sensory pain) and aversive place-conditioning behavior (emotional pain) following amygdaloid administration of various glutamatergic compounds in nerve-injured animals. The results indicate that endogenous activation of amygdaloid group I metabotropic GluRs, mGluR(1) and mGluR(5), and the NMDA-R contributes to maintenance of sensory and emotional components of neuropathic pain. The predominant effect by amygdaloid group I mGluRs was facilitation of emotional-like pain behavior.

Asunto(s)

Amígdala del Cerebelo/metabolismo , Emociones/fisiología , Dolor/etiología , Neuropatías Peroneas/complicaciones , Neuropatías Peroneas/patología , Receptores de Glutamato/metabolismo , Amígdala del Cerebelo/efectos de los fármacos , Animales , Emociones/efectos de los fármacos , Agonistas de Aminoácidos Excitadores/farmacología , Antagonistas de Aminoácidos Excitadores/farmacología , Hiperalgesia/etiología , Masculino , Dimensión del Dolor/métodos , Umbral del Dolor/efectos de los fármacos , Umbral del Dolor/fisiología , Ratas , Ratas Wistar , Receptores de Glutamato/clasificación

RESUMEN

Abstract The toxin ss-N-methylamino-L-alanine (BMAA) was proposed to contribute to the ALS/Parkinsonism-dementia complex of Guam (ALS/PDC) based on its presence in cycad seeds, which constituted a dietary item in afflicted populations, and its ability to induce a similar disease phenotype in primates. Although the role of BMAA in human neurodegenerative disease is still highly debated, it appears to injure cultured neurons via mechanisms involving overactivation of neuroexcitatory glutamate receptors. However, BMAA lacks the side-chain acidic group of glutamate and other excitatory amino acids, and in its place has an amino group. In past studies we found that toxic and excitatory effects of BMAA on cultured neurons were dependent upon the presence of bicarbonate in the medium, and suggested that formation of a carbamate adduct of the side-chain amino group might produce structures capable of activating glutamate receptors. Also, while BMAA is a weal agonist at NMDA-type glutamate receptors, we found low levels of BMAA to selectively damage vulnerable sub-populations of neurons, including motor neurons, via activation of AMPA/kainate receptors. Recent reports that BMAA is produced by cyanobacteria in diverse ecosystems and is present in brain and spinal cord tissues from sporadic ALS and Alzheimer's patients as well as brains of ALS/PDC patients provide strong motivation for further investigations of its toxic mechanisms and contributions to human disease.

Asunto(s)

Aminoácidos Diaminos/toxicidad , Aminoácidos Dicarboxílicos/toxicidad , Esclerosis Amiotrófica Lateral/inducido químicamente , Cianobacterias/química , Neurotoxinas/toxicidad , Enfermedad de Parkinson/etiología , Aminoácidos Diaminos/farmacología , Aminoácidos Dicarboxílicos/farmacología , Esclerosis Amiotrófica Lateral/patología , Animales , Bicarbonatos/metabolismo , Humanos , Neuronas Motoras/efectos de los fármacos , Receptores de Glutamato/clasificación , Receptores de Glutamato/metabolismo , Transducción de Señal/efectos de los fármacos

RESUMEN

BACKGROUND: The neurodevelopment of hippocampus and prefrontal cortex are known to influence different functions in normal and pathological conditions including cognition and sensorimotor functions. The neonatal lesion of the ventral hippocampus (VH) in rats has been established as an animal model of schizophrenia and is used to study postpubertal changes in behavior and neurobiology. In order to investigate whether early VH lesion in rats alters the expression of genes implicated in schizophrenia pre- and post-puberty, we studied the mRNA expression of neuropeptides (substance P, dynorphin and enkephalin), dopamine D1, dopamine D2, and NMDA (subunits NR1 and NR2A) receptors in this animal model. METHODS: Rat pups were lesioned at postnatal day 7 by injecting ibotenic acid into the VH bilaterally, and then sacrificed at age 35 (pre-puberty) and 65 (post-puberty) days. Another group of adult rats had the same lesion in the VH, to independently assess the effects of the lesion on the expression of genes, and then sacrificed at week 4 and 8 post lesion. Sham groups were injected with cerebrospinal fluid using the same procedure. Brains were removed and sectioned to study the mRNA expression using in situ hybridization (ISH). RESULTS: The main results are the postpubertal onset of increased NR1 mRNA expression in all cortical regions and decreased dopamine D2 receptor, substance P and enkephalin mRNA expression in the striatum only in rats lesioned as neonates. These changes were not observed in the adult group with VH lesion. CONCLUSIONS: Our results demonstrate that the postpubertal behavioral changes in this animal model (and possibly schizophrenia) are related to postpubertal onset of changes in the development of functions and interactions of the dopamine and glutamate receptors in the mesocortical system.

Asunto(s)

Lesiones Encefálicas/patología , Regulación del Desarrollo de la Expresión Génica/fisiología , Hipocampo/metabolismo , Neuropéptidos/genética , ARN Mensajero/metabolismo , Receptores Dopaminérgicos/genética , Receptores de Glutamato/genética , Factores de Edad , Análisis de Varianza , Animales , Animales Recién Nacidos , Lesiones Encefálicas/inducido químicamente , Dinorfinas/genética , Dinorfinas/metabolismo , Encefalinas/genética , Encefalinas/metabolismo , Femenino , Hipocampo/crecimiento & desarrollo , Ácido Iboténico , Masculino , Neuropéptidos/metabolismo , Embarazo , Ratas , Ratas Sprague-Dawley , Receptores Dopaminérgicos/metabolismo , Receptores de Glutamato/clasificación , Receptores de Glutamato/metabolismo , Receptores de N-Metil-D-Aspartato/genética , Receptores de N-Metil-D-Aspartato/metabolismo , Sustancia P/genética , Sustancia P/metabolismo

RESUMEN

Exposure to stress during gestation alters brain development resulting in permanent alterations that may increase susceptibility to subsequent cognitive or neuropsychiatric disorders. In this manuscript we examined the effects of prenatal stress on critical determinants of the glutamatergic synapse under basal conditions as well as in response to acute stress. The main finding of this work is that gestational stress altered the responsiveness of the glutamatergic system following a challenge at adulthood. In fact, while in control animals acute swim stress enhanced the phosphorylation levels of the NMDA receptor subunits NR-1(Ser896) and NR-2B(Ser1303) as well as the phosphorylation levels of alpha calcium/calmodulin-dependent protein kinase II (Thr286), a crucial sensor of calcium fluctuations, prenatal stress prevented or attenuated such activation. This dynamic modulation is restricted to prefrontal cortex since no changes were observed in the hippocampus, in line with the different maturational profile of these brain regions. Changes were also observed in the phosphorylation of the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate subunit GluR-1(Ser831) which, however, relied on the acute stress exposure and were independent of gestational stress. These effects point to a unique interference of chronic prenatal stress with the responsiveness of specific determinants of the glutamatergic synapse at adulthood in a region specific manner. The inability to mount an homeostatic glutamatergic response to subsequent stress at adulthood may impair the normal responses of the cell to challenging situations.

Asunto(s)

Ácido Glutámico/metabolismo , Corteza Prefrontal/metabolismo , Efectos Tardíos de la Exposición Prenatal/patología , Receptores de Glutamato/metabolismo , Estrés Psicológico/patología , Análisis de Varianza , Animales , Proteína Quinasa Tipo 2 Dependiente de Calcio Calmodulina/metabolismo , Femenino , Hipocampo/patología , Masculino , Fosforilación/fisiología , Embarazo , Ratas , Ratas Sprague-Dawley , Receptores de Glutamato/clasificación , Receptores de Glutamato/genética , Restricción Física/métodos , Serina/metabolismo , Factores Sexuales , Estrés Psicológico/etiología , Natación , Treonina/metabolismo

RESUMEN

Dlg (Discs Large) is a multidomain protein that interacts with glutamate receptors and potassium channels at Drosophila neuromuscular junctions (NMJs) and at mammalian central nervous system synapses. Dlg also localizes postsynaptically at cholinergic mammalian NMJs. We show here that alpha-amino-3-hydroxy-5-methylisoxazole-4-proprionate (AMPA) receptor subunits, together with glutamate, are present at the mammalian NMJ. Both AMPA and NMDA (N-methyl-D-aspartate) glutamate receptor subunits display overlapping postsynaptic localization patterns with Dlg at all NMJs examined in normal mice. Kir2 potassium channels also localize with Dlg and glutamate receptors at this synapse. Localization of the components of a glutamatergic system suggests novel mechanisms at mammalian neuromuscular synapses.

Asunto(s)

Unión Neuromuscular/metabolismo , Receptores de Glutamato/clasificación , Receptores de Glutamato/metabolismo , Membranas Sinápticas/metabolismo , Animales , Bungarotoxinas/metabolismo , Ácido Glutámico , Ratones , Ratones Endogámicos C57BL , Microscopía Confocal/métodos , Microscopía Fluorescente , Proteínas del Tejido Nervioso/metabolismo , Unión Neuromuscular/citología , Canales de Potasio/metabolismo , Proteínas Asociadas a SAP90-PSD95 , Canales de Sodio/metabolismo , Sinaptofisina/metabolismo

RESUMEN

The seizure-induced molecular and functional alterations of glutamatergic transmission in the hippocampus have been investigated. Daily repeated epileptic seizures were induced for 12 days by intraperitoneal administration of 4-aminopyridine (4-AP; 4.5 mg/kg) in adult Wistar rats. The seizure symptoms were evaluated on the Racine's scale. One day after the last injection, the brains were removed for in vitro electrophysiological experiments and immunohistochemical analysis. The glutamate receptor subunits NR1, NR2A, NR2B, GluR1, GluR1(flop), GluR2, and KA-2 were studied using the histoblotting method. The semi-quantitative analysis of subunit immunoreactivities in hippocampal layers was performed with densitometry. In the hippocampus, increase of GluR1, GluR1(flop) and NR2B immunostaining was observed in most of the areas and layers. The significant decrease of GluR2 staining intensity was observed in the CA1 and dentate gyrus. Calcium permeability of hippocampal neurons was tested by a cobalt uptake assay in hippocampal slices. The uptake of cobalt increased in the CA1 area and dentate gyrus, but not in the CA3 region following 4-AP treatment. Effects of AMPA and NMDA (N-methyl-d-aspartate) glutamate receptor antagonists (1-(4-aminophenyl)-4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine hydrochloride (GYKI 52466) and D-APV respectively) were measured in hippocampal slices using extracellular recording. Analysis of the population spikes revealed the reduced effectiveness of the AMPA receptor antagonist GYKI 52466, while the effect of the NMDA receptor antagonist d-(2R)-amino-5-phosphonovaleric acid was similar to controls. The results demonstrated that repeated convulsions induced structural and functional changes in AMPA receptor-mediated transmission, while NMDA and kainate receptor systems displayed only alterations in receptor subunit composition.

Asunto(s)

Regulación de la Expresión Génica/fisiología , Hipocampo/metabolismo , Hipocampo/fisiopatología , Receptores de Glutamato/metabolismo , Convulsiones/patología , 2-Amino-5-fosfonovalerato/farmacología , 4-Aminopiridina , Potenciales de Acción/efectos de los fármacos , Potenciales de Acción/fisiología , Animales , Benzodiazepinas/farmacología , Biofisica , Calcio/metabolismo , Cobalto/metabolismo , Estimulación Eléctrica , Antagonistas de Aminoácidos Excitadores/farmacología , Regulación de la Expresión Génica/efectos de los fármacos , Hipocampo/efectos de los fármacos , Hipocampo/patología , Técnicas In Vitro , Masculino , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Subunidades de Proteína/metabolismo , Ratas , Ratas Wistar , Receptores de Glutamato/clasificación , Convulsiones/inducido químicamente , Convulsiones/metabolismo , Convulsiones/fisiopatología , Transmisión Sináptica/efectos de los fármacos , Transmisión Sináptica/fisiología

RESUMEN

Glutamatergic signaling plays an important role in the behavioral and molecular plasticity observed in behavioral sensitization to cocaine. Redistribution of the glutamate receptors in the synaptosomal membrane fraction was investigated in the nucleus accumbens, dorsolateral striatum, and ventral tegmental area at 1 or 21 days of withdrawal in behaviorally sensitized rats. At 1 day of withdrawal, there were no changes in either tissue level or redistribution of glutamate receptors in nucleus accumbens core and shell and ventral tegmental area. At 21 days of withdrawal, there was a decrease in the expression of mGluR2/3 protein in core and shell, an increase in GluR1 and a decrease in Homer1b/c proteins in the nucleus accumbens core tissue. In dorsolateral striatum, the tissue level of NMDAR2B protein was increased. Moreover, there was an augmented presence of AMPA (GluR1, GluR2), NMDA (NMDAR1, 2A, 2B), and group 1 metabotropic glutamate receptor (mGluR5) proteins in the synaptosomal fraction in core and shell of the nucleus accumbens. There was also an increase in synaptosomal mGluR2/3 protein in nucleus accumbens core. The redistribution of glutamate receptors was selective for nucleus accumbens since no changes were observed in the dorsolateral striatum and ventral tegmental area. While the tissue level of the Homer1b/c protein was selectively reduced in nucleus accumbens core, that of PSD95, PICK1, and actin was not changed in any of the brain regions examined. However, the synaptosomal membrane fraction level of Homer1b/c and PSD95 was increased in nucleus accumbens core and shell, with no changes in PICK1, and a decrease in actin protein. These observations suggest that significant redistribution of glutamate receptors and postsynaptic scaffolding proteins into synaptosomal membrane fraction is associated with withdrawal from behavioral sensitization to cocaine.

Asunto(s)

Trastornos Relacionados con Cocaína/metabolismo , Cocaína/administración & dosificación , Inhibidores de Captación de Dopamina/administración & dosificación , Receptores de Glutamato/metabolismo , Síndrome de Abstinencia a Sustancias/metabolismo , Sinaptosomas/metabolismo , Actinas/metabolismo , Animales , Conducta Animal/efectos de los fármacos , Proteínas Portadoras/metabolismo , Trastornos Relacionados con Cocaína/patología , Cuerpo Estriado/efectos de los fármacos , Cuerpo Estriado/metabolismo , Cuerpo Estriado/ultraestructura , Homólogo 4 de la Proteína Discs Large , Regulación de la Expresión Génica/efectos de los fármacos , Proteínas de Andamiaje Homer , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Masculino , Proteínas de la Membrana/metabolismo , Núcleo Accumbens/efectos de los fármacos , Núcleo Accumbens/metabolismo , Núcleo Accumbens/ultraestructura , Ratas , Ratas Sprague-Dawley , Receptores de Glutamato/clasificación , Síndrome de Abstinencia a Sustancias/patología , Sinaptosomas/efectos de los fármacos , Factores de Tiempo , Área Tegmental Ventral/efectos de los fármacos , Área Tegmental Ventral/metabolismo , Área Tegmental Ventral/ultraestructura

RESUMEN

In this article, the beginnings of glutamate pharmacology are traced from the early doubts about 'non-specific' excitatory effects, through glutamate- and aspartate-preferring receptors, to NMDA, quisqualate/AMPA and kainate subtypes, and finally to the cloning of genes for these receptor subunits. The development of selective antagonists, crucial to the subtype classification, allowed the fundamental importance of glutamate receptors to synaptic activity throughout the CNS to be realised. The ability to be able to express and manipulate cloned receptor subunits is leading to huge advances in our understanding of these receptors. Similarly the tortuous path of the nomenclature is followed from naming with reference to exogenous agonists, through abortive early attempts at generic schemes, and back to the NC-IUPHAR system based on the natural agonist, the defining exogenous agonist and the gene names.

Asunto(s)

Clonación Molecular , Ácido Glutámico/farmacología , Receptores de Glutamato , Terminología como Asunto , Animales , Historia del Siglo XX , Historia del Siglo XXI , Humanos , Receptores de Glutamato/clasificación , Receptores de Glutamato/genética , Receptores de Glutamato/historia