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Excitatory glutamate receptors

Alice Filippini, Daniela Bonini, Luca La Via, Alessandro Barbon
Glutamate receptors play a key role in excitatory synaptic transmission and plasticity in the central nervous system (CNS). Their channel properties are largely dictated by the subunit composition of tetrameric receptors. Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and kainate channels are assembled from GluA1-4 AMPA or GluK1-5 kainate receptor subunits. However, their functional properties are highly modulated by a post-transcriptional mechanism called RNA editing. This process involves the enzymatic deamination of specific adenosines (A) into inosines (I) in pre-messenger RNA...
October 20, 2016: Molecular Neurobiology
Christoph T Schanzenbächer, Sivakumar Sambandan, Julian D Langer, Erin M Schuman
Homeostatic scaling adjusts the strength of synaptic connections up or down in response to large changes in input. To identify the landscape of proteomic changes that contribute to opposing forms of homeostatic plasticity, we examined the plasticity-induced changes in the newly synthesized proteome. Cultured rat hippocampal neurons underwent homeostatic up-scaling or down-scaling. We used BONCAT (bio-orthogonal non-canonical amino acid tagging) to metabolically label, capture, and identify newly synthesized proteins, detecting and analyzing 5,940 newly synthesized proteins using mass spectrometry and label-free quantitation...
October 19, 2016: Neuron
J Xu, B J Hartley, P Kurup, A Phillips, A Topol, M Xu, C Ononenyi, E Foscue, S-M Ho, T D Baguley, N Carty, C S Barros, U Müller, S Gupta, P Gochman, J Rapoport, J A Ellman, C Pittenger, B Aronow, A C Nairn, M W Nestor, P J Lombroso, K J Brennand
The brain-specific tyrosine phosphatase, STEP (STriatal-Enriched protein tyrosine Phosphatase) is an important regulator of synaptic function. STEP normally opposes synaptic strengthening by increasing N-methyl D-aspartate glutamate receptor (NMDAR) internalization through dephosphorylation of GluN2B and inactivation of the kinases extracellular signal-regulated kinase 1/2 and Fyn. Here we show that STEP61 is elevated in the cortex in the Nrg1(+/-) knockout mouse model of schizophrenia (SZ). Genetic reduction or pharmacological inhibition of STEP prevents the loss of NMDARs from synaptic membranes and reverses behavioral deficits in Nrg1(+/-) mice...
October 18, 2016: Molecular Psychiatry
Alexander W M Hooper, Suleiman A Igdoura
Microgliosis and astrogliosis are known to be exacerbating factors in the progression of the lysosomal storage disorder Sandhoff disease. We have also found evidence for excitotoxicity via glutamate receptors in Sandhoff disease. To view the interaction of these cascades, we measured cerebellar expression of markers for gliosis, apoptosis, and excitatory synapses over the disease course in a Sandhoff disease mouse model. We observe a 2-stage model, with initial activation of microgliosis as early as 60days of age, followed by a later onset of astrogliosis, caspase-mediated apoptosis, and reduction in GluR1 at approximately 100days of age...
October 15, 2016: Journal of Neuroimmunology
Maria Amalia Di Castro, Flavia Trettel, Giampaolo Milior, Laura Maggi, Davide Ragozzino, Cristina Limatola
Chemokines have several physio-pathological roles in the brain. Among them, the modulation of synaptic contacts and neurotransmission recently emerged as crucial activities during brain development, in adulthood, upon neuroinflammation and neurodegenerative diseases. CXCL16 is a chemokine normally expressed in the brain, where it exerts neuroprotective activity against glutamate-induced damages through cross communication with astrocytes and the involvement of the adenosine receptor type 3 (A3R) and the chemokine CCL2...
October 10, 2016: Scientific Reports
Daniel P Radin, Sheng Zhong, Richard Purcell, Arnold Lippa
Memory loss observed as a consequence of aging is paralleled by a down-regulation of AMPA-type glutamate receptors (AMPARs) that mediate fast excitatory synaptic transmission. Activation of these receptors enhances long-term potentiation (LTP), a neuronal process demonstrated to be crucial for memory storage and thought to be a cellular substrate of learning and memory. In the present studies, we determined that LTP was reduced in aged rats when compared to young rats and that acute treatment with CX1846, a novel AMPAR positive allosteric modulator, fifteen minutes prior to tetanic stimulation completely reversed the significant deficit in LTP observed in aged rats...
October 6, 2016: Biomedicine & Pharmacotherapy, Biomédecine & Pharmacothérapie
Bryan F Singer, Nancy Bubula, Magdalena M Przybycien-Szymanska, Dongdong Li, Paul Vezina
Drug-paired stimuli rapidly enlarge dendritic spines in the nucleus accumbens (NAcc). While increases in spine size and shape are supported by rearrangement of the actin cytoskeleton and facilitate the synaptic expression of AMPA-type glutamate receptors, it remains unclear whether drug-related stimuli can influence signaling pathways known to regulate these changes in spine morphology. These pathways were studied in rats trained on a discrimination learning paradigm using subcellular fractionation and protein immunoblotting to isolate proteins within dendritic spine compartments in the NAcc shell...
October 6, 2016: European Neuropsychopharmacology: the Journal of the European College of Neuropsychopharmacology
Luiz Luciano Falconi-Sobrinho, Tayllon Dos Anjos-Garcia, Daoud Hibrahim Elias Filho, Norberto Cysne Coimbra
The medial prefrontal cortex can influence unconditioned fear-induced defensive mechanisms organised by diencephalic neurons that are under tonic GABAergic inhibition. The posterior hypothalamus (PH) is involved with anxiety- and panic attack-like responses. To understand this cortical mediation, our study characterised anterior cingulate cortex (ACC)-PH pathways and investigated the effect of ACC local inactivation with lidocaine. We also investigated the involvement of PH ionotropic glutamate receptors in the defensive behaviours and fear-induced antinociception by microinjecting NBQX (an AMPA/kainate receptor antagonist) and LY235959 (a NMDA receptor antagonist) into the PH...
October 3, 2016: Neuropharmacology
Sudarat Nimitvilai, Chang You, Devinder S Arora, Maureen A McElvain, Bertha J Vandegrift, Mark S Brodie, John J Woodward
Drugs of abuse increase the activity of dopaminergic neurons of the ventral tegmental area (VTA), and output from the VTA is critical for both natural and drug-induced reward and reinforcement. Ethanol and the abused inhalant toluene both enhance VTA neuronal firing, but the mechanisms of this effect is not fully known. In this study, we used extracellular recordings to compare the actions of toluene and ethanol on DA VTA neurons. Both ethanol and toluene increased the firing rate of DA neurons, although toluene was ~100 times more potent than ethanol...
2016: Frontiers in Neuroscience
Devesh Mishra, Jose Ignacio Pena-Bravo, Kah-Chung Leong, Antonieta Lavin, Carmela M Reichel
World-wide methamphetamine (meth) use is increasing at a rapid rate; therefore, it has become increasingly important to understand the synaptic changes and neural mechanisms affected by drug exposure. In rodents, 6-h access to contingent meth results in an escalation of drug intake and impaired cognitive sequelae typically associated with changes within the corticostriatal circuitry. There is a dearth of knowledge regarding the underlying physiological changes within this circuit following meth self-administration...
October 5, 2016: Brain Structure & Function
Moritz Armbruster, Elizabeth Hanson, Chris G Dulla
: Excitatory amino acid transporters (EAATs) are abundantly expressed by astrocytes, rapidly remove glutamate from the extracellular environment, and restrict the temporal and spatial extent of glutamate signaling. Studies probing EAAT function suggest that their capacity to remove glutamate is large and does not saturate, even with substantial glutamate challenges. In contrast, we report that neuronal activity rapidly and reversibly modulates EAAT-dependent glutamate transport. To date, no physiological manipulation has shown changes in functional glutamate uptake in a nonpathological state...
October 5, 2016: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
Andrei Rozov, Nail Burnashev
Suppression of NMDA receptor (NMDAR)-mediated currents by intracellular Ca(2+) has been described as a negative feedback loop in NMDAR modulation. In the time scale of tenths of milliseconds the depth of the suppression does not depend on the Ca(2+) source. It may be caused by Ca(2+) influx through voltage-gated calcium channels, NMDAR channels or release from intracellular stores. However, NMDARs are often co-expressed in synapses with Ca(2+)-permeable AMPA receptors (AMPARs). Due to significant differences in activation kinetics between these two types of glutamate receptors (GluRs), Ca(2+) entry through AMPARs precedes full activation of NMDARs, and therefore, might have an impact on the amplitude of NMDAR-mediated currents...
September 28, 2016: Cell Calcium
Sana A Shaikh, Drew M Dolino, Garam Lee, Sudeshna Chatterjee, David M MacLean, Charlotte Flatebo, Christy F Landes, Vasanthi Jayaraman
Fast excitatory synaptic signaling in the mammalian brain is mediated by AMPA-type ionotropic glutamate receptors. In neurons, AMPA receptors co-assemble with auxiliary proteins, such as stargazin, which can markedly alter receptor trafficking and gating. Here, we used luminescence resonance energy transfer measurements to map distances between the full-length, functional AMPA receptor and stargazin expressed in HEK293 cells and to determine the ensemble structural changes in the receptor due to stargazin. In addition, we used single-molecule fluorescence resonance energy transfer to study the structural and conformational distribution of the receptor and how this distribution is affected by stargazin...
October 4, 2016: Cell Reports
M R Kapolowicz, L T Thompson
Tinnitus is a devastating auditory disorder impacting a growing number of people each year. The aims of the current experiment were to assess neuronal mechanisms involved in the initial plasticity after traumatic noise exposure that could contribute to the emergence of tinnitus and to test a potential pharmacological treatment to alter this early neural plasticity. Specifically, this study addressed rapid effects of acute noise trauma on amygdalo-hippocampal circuitry, characterizing biomarkers of both excitation and inhibition in these limbic regions, and compared them to expression of these same markers in primary auditory cortex shortly after acute noise trauma...
October 1, 2016: Hearing Research
Mikaela Therrien, Rishel Vohnoutka, Edward Boumil, Mary Guaraldi, Sangmook Lee, Thomas B Shea
The nervous system is composed of excitatory and inhibitory neurons. One major class of inhibitory neurons release the neurotransmitter γ-Aminobutyric acid (GABA). GABAergic inhibitory activity maintains the balance that is disrupted in conditions such as epilepsy. At least some GABAergic neurons are initially excitatory and undergo a developmental conversion to convert to inhibitory neurons. The mechanism(s) behind this conversion are thought to include a critical developmental increase in excitatory activity...
September 26, 2016: International Journal of Developmental Neuroscience
Shujia Zhu, Eric Gouaux
Ionotropic glutamate receptors (iGluRs) transduce signals derived from release of the excitatory neurotransmitter glutamate from pre-synaptic neurons into excitation of post-synaptic neurons on a millisecond time-scale. In recent years, the elucidation of full-length iGluR structures of NMDA, AMPA and kainate receptors by X-ray crystallography and single particle cryo-electron microscopy has greatly enhanced our understanding of the interrelationships between receptor architecture and gating mechanism. Here we briefly review full-length iGluR structures and discuss the similarities and differences between NMDA receptors and non-NMDA iGluRs...
September 20, 2016: Neuropharmacology
Adriana Pinto de Freitas, Danielle Dias Pinto Ferreira, Arlete Fernandes, Robertta Silva Martins, Vladimir Pedro Peralva Borges-Martins, Matheus Figueiredo Sathler, Maurício Dos-Santos-Pereira, Roberto Paes-de-Carvalho, Elizabeth Giestal-de-Araujo, Ricardo Augusto de Melo Reis, Regina Celia Cussa Kubrusly
l-Glutamate and l-aspartate are the main excitatory amino acids (EAAs) in the Central Nervous System (CNS) and their uptake regulation is critical for the maintenance of the excitatory balance. Excitatory amino acid transporters (EAATs) are widely distributed among central neurons and glial cells. GLAST and GLT1 are expressed in glial cells, whereas excitatory amino acid transporter 3/excitatory amino acid carrier 1 (EAAT3/EAAC1) is neuronal. Different signaling pathways regulate glutamate uptake by modifying the activity and expression of EAATs...
September 20, 2016: Neuroscience
Rui Wang, P Hemachandra Reddy
Excitatory glutamatergic neurotransmission via N-methyl-d-aspartate receptor (NMDAR) is critical for synaptic plasticity and survival of neurons. However, excessive NMDAR activity causes excitotoxicity and promotes cell death, underlying a potential mechanism of neurodegeneration occurred in Alzheimer's disease (AD). Studies indicate that the distinct outcomes of NMDAR-mediated responses are induced by regionalized receptor activities, followed by different downstream signaling pathways. The activation of synaptic NMDARs initiates plasticity and stimulates cell survival...
September 23, 2016: Journal of Alzheimer's Disease: JAD
Sarah L Chellappa, Giulia Gaggioni, Julien Q M Ly, Soterios Papachilleos, Chloé Borsu, Alexandre Brzozowski, Mario Rosanova, Simone Sarasso, André Luxen, Benita Middleton, Simon N Archer, Derk-Jan Dijk, Marcello Massimini, Pierre Maquet, Christophe Phillips, Rosalyn J Moran, Gilles Vandewalle
Several neuropsychiatric and neurological disorders have recently been characterized as dysfunctions arising from a 'final common pathway' of imbalanced excitation to inhibition within cortical networks. How the regulation of a cortical E/I ratio is affected by sleep and the circadian rhythm however, remains to be established. Here we addressed this issue through the analyses of TMS-evoked responses recorded over a 29 h sleep deprivation protocol conducted in young and healthy volunteers. Spectral analyses of TMS-evoked responses in frontal cortex revealed non-linear changes in gamma band evoked oscillations, compatible with an influence of circadian timing on inhibitory interneuron activity...
2016: Scientific Reports
Stylianos Kouvaros, Costas Papatheodoropoulos
The hippocampal synapses display a conspicuous ability for long-term plasticity, which is thought to contribute to learning and memory. Previous research has shown that long-term potentiation (LTP) greatly differs between the dorsal (DH) and ventral (VH) CA1 hippocampal synapses when induced by high-frequency stimulation. In this study, using rat hippocampal slices and more physiologically relevant activity patterns based on the frequency of the theta rhythm (i.e., theta-burst stimulation, TBS) we found that the DH compared with the VH displayed a higher ability for induction and stability of NMDA receptor-dependent LTP of the field excitatory postsynaptic potential...
September 20, 2016: Hippocampus
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