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He, Kaiwen. "AMPA Receptor and synaptic plasticity." College Park, Md.: University of Maryland, 2009. http://hdl.handle.net/1903/9181.
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Thesis (Ph.D.) -- University of Maryland, College Park, 2009.Thesis research directed by: Dept. of Biology. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Voss, Oliver Paul. "AMPA receptor potentiators : mechanisms of neuroplasticity." Thesis, University of Edinburgh, 2007. http://hdl.handle.net/1842/25276.
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The AMPA receptor potentiator LY404187 is able to significantly increase the average length of neuritic processes in the neuroblastoma cell line SH-SY5Y only in the presence of s-AMPA, and this response is dependent on AMPA receptor activation. The compound also increases neurofilament protein levels as well as levels of the BDNF receptor Trk-B. The increase in neuritic length is blocked by addition of an antibody specific for BDNF indicating that this neurotrophin is required for the induction of neurite growth. The ability to induce morphological change in neuronal processes of the compound was then tested in a rodent model of lesions and sprouting. Unilateral ibotenic lesions of the entorhinal cortex in mice produce a progressive and substantial loss of synapses in the molecular layer of the dentate gyrus. Twice daily s.c. injections of LY404187 for 14 and 28 days post-lesion did not produce any significant change in synaptophysin immunoreactivity in the dentate gyrus. There was also no change in the volume of the lesion in the entorhinal cortex. In a secondary study the rate of neurogenesis in the dentate gyrus was also measured. Administration of LY404187 failed to induce a change in the number of BrdU +ve cells within the sub-granular zone of the dentate gyrus. Any long term structural of behavioural change caused by prolonged AMPA receptor potentiation is likely to be underpinned by changes in protein expression. The levels of key proteins involved in the intracellular response to AMPA receptor activation were measured by Western Blot and immunohistochemistry and levels of the neurotransmitters dopamine and serotonin were measured by HPLC. The effect of chronic administration to the AMPA receptor potentiator LY450108 on the rate of neurogenesis and the development of newly born neuron in the hippocampus was also investigated.
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Man, Hengye. "AMPA receptor trafficking and synaptic plasticity." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ58616.pdf.
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Fowler, Jill H. "AMPA receptors : role in brain injury." Thesis, University of Glasgow, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274788.
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LAMBOLEZ, BERTRAND. "Structure et fonction des recepteurs ampa." Paris 6, 1991. http://www.theses.fr/1991PA066542.
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Le recepteur ampa est un recepteur-canal dont l'agoniste naturel est le neurotransmetteur glutamate. Nous avons etudie le recepteur ampa exprime dans l'ovocyte de xenope a partir de l'adn complementaire d'une de ses sous-unites, glur1 ou a partir d'arn messagers de cerveau de rat. L'etude fonctionnelle de glur1 montre qu'il repond au kainate et a l'ampa et suggere que le recepteur ampa des neurones est un heteromere qui serait responsable des effets electrophysiologiques de l'ampa et du kainate, precedemment attribues a deux recepteurs distincts. Le recepteur ampa est autoinhibe par les agonistes de type ampa: quand on augmente la concentration d'agoniste, la reponse atteint un maximum avant de decroitre. Cette autoinhibition est reservee par des antagonistes competitifs, qui diminuent le taux d'occupation du recepteur par l'agoniste. La diminution de la reponse est interpretee comme une augmentation de la proportion de recepteurs desensibilises. Le recepteur ampa a donc des proprietes pharmacologiques dont l'originalite tient aux particularites de sa desensibilisation. Un modele de la desensibilisation de ce recepteur est propose
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Kuusinen, Arja. "Structure-function relations in AMPA receptors." Helsinki : University of Helsinki, 2000. http://ethesis.helsinki.fi/julkaisut/mat/bioti/vk/kuusinen/.
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Riva, Irene. "Biophysical properties of AMPA receptor complexes." Doctoral thesis, Humboldt-Universität zu Berlin, 2020. http://dx.doi.org/10.18452/21299.
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Die exzitatorische Neurotransmission im gesamten Zentralnervensystem (ZNS) der Wirbeltiere wird weitgehend durch die α-Amino-3-hydroxy-5-methyl-4-isoxazolpropionsäure-Rezeptoren (AMPARs) vermittelt. AMPARs sind Glutamat-gesteuerte Ionenkanäle, die sich an der postsynaptischen Membran befinden, wo sie den Kern makromolekularer Komplexe mit einer Reihe von Hilfsproteinen bilden, die die Rezeptorfunktion konzertiert regulieren. Die bekanntesten dieser Proteine sind die transmembranen AMPA-Rezeptor-Regulierungsproteine (TARPs). TARPs zeigen eine verwirrende Reihe von Effekten auf den Handel, die synaptische Verankerung, die Gate-Kinetik und die Pharmakologie von AMPARs. Über die strukturellen Merkmale des AMPAR-TARP-Komplexes wurde zunehmendes Wissen gesammelt. Die molekularen Mechanismen, die der TARP-Modulation der AMPARs zugrunde liegen, sind jedoch noch nicht vollständig aufgeklärt. In der vorliegenden Studie wurden die AMPAR-TARP-Interaktionen mit Hilfe der Elektrophysiologie in 293 Zellen der menschlichen embryonalen Niere (HEK) untersucht. Die Rolle der extrazellulären TARP-Schleifen, Loop1 (L1) und Loop2 (L2), bei der Modulation der AMPAR-Ansteuerung wurde analysiert. Es wurde ein Modell für die TARP-Modulation vorgeschlagen, das auf vorhergesagten zustandsabhängigen Wechselwirkungen von TARP L1 und L2 mit dem AMPAR basiert. Da die nativen AMPARs im Gehirn hauptsächlich aus heterotetrameren Zusammensetzungen von vier verschiedenen Untereinheiten (GluA1-4) bestehen, wurden außerdem verschiedene Zusammensetzungen von AMPAR-Untereinheiten getestet. Es wurden sowohl gemeinsame als auch von den Untereinheiten abhängige Mechanismen der AMPAR-Modulation durch TARPs beobachtet. Zusammenfassend liefern diese Experimente den Nachweis, dass TARP L1 und L2 nicht an der Assoziation von AMPAR-TARP-Komplexen beteiligt sind und die Modulation der AMPAR-Ansteuerung durch TARPs vollständig erklären können.Excitatory neurotransmission throughout the vertebrate central nervous system (CNS) is largely mediated by the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs). AMPARs are glutamate-gated ion channels located at the postsynaptic membrane, where they compose the hub of macromolecular complexes with a number of auxiliary proteins that concertedly regulate the receptor function. Among these proteins the most known ones are the transmembrane AMPA receptor regulatory proteins (TARPs). TARPs show a bewildering array of effects on the trafficking, synaptic anchoring, gating kinetics and pharmacology of AMPARs. Growing knowledge has been gathered about the structural features of the AMPAR-TARP complex. However, the molecular mechanisms underlying TARP modulation of AMPARs have not been fully revealed yet. Given that higher brain functions rely upon AMPAR activity and dysregulation of AMPARs has been associated to life-threatening CNS disorders, big efforts are being made to unravel the molecular machinery behind AMPAR regulation and to identify AMPAR auxiliary proteins as potential pharmacological targets. In the present study, AMPAR-TARP interactions were investigated using electrophysiology in human embryonic kidney (HEK) 293 cells. The role of TARP extracellular loops, Loop1 (L1) and Loop2 (L2), in the modulation of AMPAR gating was analysed. A model for TARP modulation has been proposed, based on predicted state-dependent interactions of TARP L1 and L2 with the AMPAR. Moreover, considering that native AMPARs in the brain mainly consist of heterotetrameric assemblies of four distinct subunits (GluA1-4), different AMPAR subunit compositions were tested. Common as well as subunit-dependent mechanisms of AMPAR modulation by TARPs have been observed. In summary, these experiments provided evidence that TARP L1 and L2 are not involved in association of AMPAR-TARP complexes and can entirely account for the modulation of AMPAR gating by TARPs.
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Dev, Kumlesh Kumar. "Regulation of AMPA receptors in rat CNS." Thesis, University of Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337228.
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Strehlow, Friederike Charlotte [Verfasser], and Nikolaj [Akademischer Betreuer] Klöcker. "Cornichon-Proteine - neue Untereinheiten der AMPA-Rezeptoren." Freiburg : Universität, 2012. http://d-nb.info/1123469946/34.
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Borchardt, Thilo. "Die Konstruktion von Mäusen mit veränderten AMPA-Rezeptoren." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=96489954X.
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Prescott, Christina Rapp. "Dual effects of kynurenic acid on AMPA receptors /." Connect to full text via ProQuest. IP filtered, 2005.
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Thesis (Ph.D. in Neuroscience) -- University of Colorado, 2005.Typescript. Includes bibliographical references (leaves 116-128). Free to UCDHSC affiliates. Online version available via ProQuest Digital Dissertations;
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Zonouzi, M. "Regulation of calcium-permeable AMPA receptors in glia." Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1302557/.
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AMPA receptors (AMPARs) mediate majority of excitatory synaptic transmission, and are involved in fast neuronal glial signaling in the central nervous system (CNS). These receptors are tetrameric assemblies that function as homomeric or heteromeric combinations of four AMPAR subunits (GluA1-4). Many key AMPAR properties are determined by the GluA2 subunit, the absence of which renders the AMPAR calcium permeable. Calcium permeable AMPARs (CP-AMPARs) are relatively widespread in the CNS being present in certain neurons and many glia. The calcium permeability of neuronal AMPARs is known to be relatively plastic, changing during development and following high frequency synaptic activity. It is clear that calcium permeable AMPARs play an important role in normal functions of Bergmann glia and oligodendrocyte precursor cells, however factors that regulate the CP-AMPAR in glial cells are still poorly understood. Little is known about the transmembrane auxiliary AMPA subunit (TARPs) present in glial cells. In Chapter 3 of this thesis, I consider the role of transmembrane AMPAR regulatory proteins (TARPs) in controlling AMPAR channel properties and trafficking. In particular, these experiments identify γ-5 as a novel TARP that occurs mainly in glial cells, and is present at high levels in Bergmann glia. Functionally, this TARP appears selective for long form AMPAR subunits (predominantly calcium permeable). My experiments also demonstrate that γ-5 co-localizes with a late endosome protein. Uniquely, γ-5 appears selective for the trafficking of GluA2, and is dependent on the protein SAP97 for trafficking and/or localisation. Oligodendrocyte precursor cells (OPCs), which are responsible for the formation of myelinating cells in the CNS, form a large proportion of the glial cells present in developing brain. OPCs are vulnerable to cell death in conditions such as periventricular white matter damage (hypoxic-ischemic white matter injury) in newborns. In Chapter 4, I have investigated factors that regulate calcium permeable AMPARs in OPCs, including mGluRs and purinergic receptors. Surprisingly I find that these receptors regulate calcium permeable AMPARs. This chapter identifies key mechanisms underlying this switch in AMPAR subtype, including the TARP γ-2 (Stargazin) that is involved in mGluR-induced ‘plasticity’ of AMPARs in OPCs. The experiments described in the final chapter, investigates the transmembrane AMPAR regulatory protein cornichon-3 (CNIH3). In this thesis I identified that the AMPAR regulatory protein cornichon-3 (CNIH3) is expressed at the cell surface in OPCs and that when over-expressed can influence their AMPAR channel properties.
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Rockett, Mark Peter. "The contribution of AMPA receptors to neuropathic pain." Thesis, University of Edinburgh, 2005. http://hdl.handle.net/1842/29971.
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This study was designed to investigate the role of AMPA, NMDA, mGlu group I and VPAC2 receptors (Rs) in the generation of neuropathic pain. Firstly, the behavioural reflex responses of naïve rats to intrathecal administration of low doses of these receptor agonists, singly or in combinations were investigated. Combinations of two or more agonists caused increased behavioural responses to thermal and mechanical stimuli. The combination of AMPA with mGluR group I and VPAC2R agonists, showed a synergistic effect whereas other combinations were less then additive. Expression of AMPA receptor GluR1 and GluR2 subunits in the superficial dorsal horn was studied using confocal immunofluorescence. In the chronic constriction injury (CCI) model of neuropathic pain both the number of GluR1-immunpositive cell bodies and the level of GluR1 expression in cells decreased significantly in lamina II of the dorsal horn, ipsilateral to the injury. In contrast, there was no change in GluR2 expression or the degree of colocalisation of GluR1 and GluR2 receptor subtypes within individual cells following CCI. The subcellular distribution of GluR1 subunits was also noted to change significantly as a result of CCI. GluR1 subunits were found to redistribute distally into neuronal processes in lamina II cells ipsilateral to CCI and also in response to acute intrathecal AMPA treatment. This redistribution may reflect an increase in the number of GluR1-containing receptors associated with synaptic sites. The relationship between the presynpatic marker protein, bassoon and GluR1-immunopositive cells was investigated showing a significant increase in the number of bassoon immunopositive puncta associated with each GluR1-immunopositive cell ipsilateral to nerve injury. These results suggest that AMPA receptors are important in the central sensitisation underlying neuropathic pain. However, it is clear that several receptors are involved in triggering maximal behavioural responses, and potential therapeutic interventions may be more effective if designed to target more than one receptor type. There is also evidence to suggest that AMPA receptors may have differing roles dependent upon their subtype composition, so subtype-specific antagonists may potentially be useful in treatment of neuropathic pain.
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Martins, Ana Caroline Vasconcelos. "Explicando Ab Initio a Intensidade de AtivaÃÃo e Antagonismo do Receptor GlutamatÃrgico GluR2." Universidade Federal do CearÃ, 2012. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=8286.
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CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel SuperiorA transmissÃo de impulsos nervosos à feita por meio das sinapses, envolvendo neurotransmissores e receptores. Os receptores ionotrÃpicos glutamatÃrgicos (GluRs) sÃo importantes canais iÃnicos do sistema nervoso central, encontrados em sinapses de excitaÃÃo rÃpida, e estÃo relacionados a funÃÃes cerebrais importantes como aprendizado e memÃria. AlÃm disso, os GluRs tambÃm estÃo associados com certas doenÃas neurolÃgicas e psiquiÃtricas, como por exemplo: a doenÃa de Alzheimer, o mal de Parkinson, a epilepsia, o acidente vascular cerebral, a esclerose lateral amiotrÃfica e a esquizofrenia. Neste trabalho, tiramos vantagem dos dados disponÃveis na literatura da co-cristalizaÃÃo dos seguintes agonistas glutamato (C5H9NO4) e AMPA (C7H10N2O4), do agonista parcial cainato (C10H15NO4) e do antagonista DNQX (C8H2N4O6) com o receptor GluR2 com resoluÃÃo de 1,9 Ã, 1,7 Ã, 1,9 à e 1,8 Ã, respectivamente, para estudar a interaÃÃo destes quatro ligantes com a GluR2 por meio de mÃtodos computacionais ab initio. Os hidrogÃnios ausentes dos dados de difraÃÃo de raios-X foram colocados atravÃs de um processo semi-clÃssico de minimizaÃÃo da energia total GluR2-ligante. A seguir, as simulaÃÃes foram feitas usando a Teoria do Funcional da Densidade (DFT), tanto ao nÃvel da aproximaÃÃo da densidade local (LDA), como da aproximaÃÃo do gradiente generalizado (GGA), para descriÃÃo dos efeitos de troca e correlaÃÃo. A utilizaÃÃo do mÃtodo de fragmentaÃÃo molecular com capas conjugadas (MFCC) tornou possÃvel analisar a interaÃÃo dos ligantes com cada um dos resÃduos prÃximos e pÃs-prÃximos do GluR2. Considerou-se tambÃm a relevÃncia da blindagem dos resÃduos pÃs-prÃximos que interagem com os ligantes, bem como se fez uma anÃlise da energia de interaÃÃo dos resÃduos (prÃximos e pÃs-prÃximos) considerados com os Ãtomos dos ligantes (resultados apresentados nos grÃficos BIRD), sem e com mediaÃÃo das molÃculas de Ãgua existentes no sÃtio de ligaÃÃo (o que permite se determinar ab initio a relevÃncia da Ãgua na energÃtica da interaÃÃo ligante-GluR2). Obteve-se a energia total de interaÃÃo GluR2-ligante em funÃÃo da distÃncia dos centroides dos ligantes aos resÃduos, o que permitiu correlacionÃ-la à intensidade de ativaÃÃo e antagonismo dos neurotransmissores em questÃo. Demonstrou-se que ela segue a ordem AMPA > glutamato > cainato > DNQX somente quando um raio do sÃtio de ligaÃÃo suficientemente grande à considerado, o que explica dados experimentais publicados sobre a ativaÃÃo e antagonismo do receptor glutamatÃrgico GluR2, sugerindo que os resÃduos pÃs-prÃximos podem ser importantes para determinar o funcionamento do receptor. Para o glutamato, os resultados obtidos indicam que os resÃduos atrativos mais relevantes sÃo: Arg485, Lys730 (mediado pela Ãgua W39), Ser654, Leu650 mediado por W69, e Lys656 mediado por W22; os resÃduos repulsivos mais relevantes para o glutamato sÃo Glu402 (pÃs-prÃximo) mediado por W36, Glu657 e Asp651 (pÃs-prÃximos). Para o AMPA os resÃduos atrativos mais relevantes sÃo: Arg485, Thr655 mediado por W134, Lys730 mediado por W137, Lys656 mediado por W138, Lys449 e Arg684 (pÃs-prÃximos); os resÃduos repulsivos mais relevantes para o AMPA sÃo Glu402 mediado por W3, Asp651 mediado por W96 e W139 (pÃs-prÃximo), e Glu657 (pÃs-prÃximo) mediado por W140. Para o cainato os resÃduos atrativos mais relevantes sÃo Arg485, Ser654, Thr655 e Arg684 (pÃs-prÃximo); os resÃduos repulsivos mais relevantes para o Cainato sÃo Glu402, Glu657 mediado por W78 (pÃs-prÃximo) e Asp651. Para o DNQX os resÃduos atrativos mais relevantes sÃo Arg485, Glu705 e Tyr450 mediado por W26 e W137; o resÃduo repulsivo mais relevante para o DNQX à Leu498. Uma plÃiade de perspectivas relacionadas aos resultados obtidos reluz e dentre elas podemos destacar a possibilidade do desenvolvimento de agonistas e antagonistas glutamatÃrgicos com especificidades voltadas à diminuiÃÃo de efeitos colaterais quando utilizados no tratamento de doenÃas relacionadas à neurotransmissÃo glutamatÃrgica.
The transmission of nerve impulses occurs through the synapses, involving neurotransmitters and receptors. The ionotropic glutamate receptors GluRs are important ionic channels of the central nervous system, founded in rapid excitation synapses, and related to important cerebral functions like learning and memory. Besides this, GluRs are also associated with important neurological and psychiatric diseases like Alzheimer, Parkinson, epilepsy, cerebral ischemia, amyotrophic lateral sclerosis, and schizophrenia. In this work, we take advantage of the available data in the literature of co-crystallization of the following full agonists glutamate (C5H9NO4) and AMPA (C7H10N2O4), the partial agonist kainate (C10H15NO4) and the antagonist DNQX (C8H2N4O6) with the GluR2 receptor with resolution of 1.9 Ã, 1.7 Ã, 1.9 Ã and 1.8 Ã, respectively to study the interaction of these four ligands with GluR2 by means of ab initio computational methods. The absent hydrogens in the GluR2-ligand X-ray diffraction data were inserted through a semi-classical total energy minimization process. Next, the simulations were performed within the scope of the Density Functional Theory (DFT), both in the local density approximation (LDA) as generalized gradient approximation (GGA) for the description of exchange-correlation effects. The use of the molecular fragmentation method with conjugated caps (MFCC) allowed to analyze the interaction between the ligands with each one close and next-closed GluR2 residues. It was also considered the relevance of the screening of the next-closed residues with interact with the ligands, and it was performed an analysis of the interaction energy between the focused residues (close and next-closed) with the atoms of the ligands (results depicted in the BIRD panels), without and with the mediation of water molecules existing in the binding pocket (which allows to determine ab initio the relevance of water in the GluR2-ligands energetic). It was obtained the GluR2-ligand total energy interaction as a function of the distance between the ligand centroid and the residues, which allowed to correlate it to the activation strength and antagonism of the ligands focused. It was demonstrated that it follows the order AMPA > glutamate > kainite > DNQX only when a large enough binding pocket radius is taken into account, explaining the experimental data published on the activation and antagonism of the glutamatergic receptor GluR2 and suggesting the next-closed residues can be important to determine the receptor functioning. For the glutamate, the obtained results point that the most important attractive residues are Arg485, Lys730 (water W39 mediated), Ser654, Leu650 (water W69 mediated), and Lys656 (water W22 mediated); the most important repulsive residues for the glutamate are Glu402 (next-closed water W36 mediated), Glu657 and Asp651 (nex-closed). For AMPA, the most important attractive residues are Arg485, Thr655 (water W134 mediated), Lys730 (water W137 mediated), Lys656 (water W138 mediated), Lys449 and Arg684 (next-closed); the most important repulsive residues for AMPA are Glu402 (water W3 mediated), Asp651 (next-closed, water W96 and W139 mediated), and Glu657 (next-closed, water W140 mediated). For kainate the most important attractive residues are Arg485, Ser654, Thr655 and Arg684 (next-closed); the most important repulsive residues for kainite are Glu402, Glu657 (next-closed, water W78 mediated) and Asp651. For DNQX, the most important attractive residues are Arg485, Glu705 and Tyr450 (water W26 and W137 mediated); the most important repulsive residue for DNQX is Leu498. A pleiade of perspectives related with the obtained results shines, among which one can highlight the possibility to develop glutamatergic agonists and antagonists with specificities related to decrease side effects when used in the treatment of maladies related with the glutamatergic neurotransmission.
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Hoy, Kevin Corcoran. "AMPA-receptor mediated plasticity within the rat spinal cord." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-3056.
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Dixon, Rebecca Mary. "Investigating AMPA Receptor Trafficking In Post-Ischaemic Hippocampal Neurons." Thesis, University of Bristol, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486070.
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Regulated AMPA receptor trafficking at excitatory synapses plays an important role in changes in synaptic strength such as long-term potentiati,on (LTP) and long-term depression (LTD). GluR2 is a key AMPA receptor subunit present in the majority of AMPA receptors in the adult rat hippocampus. In the absence of GluR2, AMPARs exhibit enhanced Ca2+ influx and decreased current at positive potentials due to an intracellular polyamine block. I investigated AMPA receptor trafficking in hippocampal neurons following oxygen-glucose deprivation (OGD), an in vitro model of ischaemia. I carried out whole-cell recordings from CA1 pyramidal neurons and measured the rectification index (RI: +40 mV EPSC/-70 mV EPSC) before and after DGD. My results show a 30 minute period of DGD results in a decrease in RI, suggesting replacement of GluR2containing AMPARs with GluR2-lacking AMPARs. To investigate direct changes in AMPAR subunit composition during OGD, surface biotinylation and Western blot analysis were carried out on dissociated hippocampal cultures. A 30 minute period ofOGD led to a reduction in surface GluR2 protein levels, but no change in surface GluRI, in support of the electrophysiology results. This data suggests a rapid switch in AMPAR subunit composition is occurring following DGD, which may be linked to the more prolonged expression of GluR2-lacking AMPARs that occurs 24-48 hours following ischaemia. To investigate the molecular mechanism for this trafficking event, I postsynaptically infused peptides that interfere with GluR2 C-terminal interactions with PDZ domain proteins, via the patch pipette. Infusion of pep2-EVKI, which selectively blocks the PICKI-GluR2 interaction, prevented the OGD-induced decrease in RI, whilst a control peptide, pep2SVKE, had no effect. Furthermore, expressing pep2-EVKI from Sindbis virus blocked the DGD-mediated decrease in surface GluR2 in dissociated hippocampal cultures. This shows PICKl is a crucial mediator of rapid AMPA receptor trafficking in post-ischaemic hippocampal neurons, and presents the GluR2-PICKl interaction as a potential therapeutic target for ischaemic stroke.
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Jackson, Hilary Louise. "AMPA receptor expression in a class of hippocampal interneurons." Thesis, University of Bristol, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.440015.
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Pinniger, Karen. "Mechanisms regulating AMPA receptor subunits during long-term plasticity." Thesis, University of Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.434738.
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Williams, S. L. "AMPA receptors in the development and treatment of epilepsy." Thesis, University College London (University of London), 2017. http://discovery.ucl.ac.uk/1547659/.
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In this thesis I have determined the effects of seizures on AMPA receptors and examined the effects of AMPA receptor modulation, by medium chain triglycerides and derivatives, on seizures. AMPA receptors play a central role in synaptic transmission in the brain and are critical for the generation of seizure activity. Recent work has indicated that prolonged seizures alter AMPA receptor transmission. Here I determined whether these changes occur in an acute in vitro seizure model, to aid exploration of the underlying mechanisms of these alterations. I demonstrated that, as observed in vivo, seizure activity changes the kinetics of AMPA receptor-mediated currents by increasing the proportion of GluA2-lacking, calcium permeable AMPA receptors. I next showed that this subunit switch is dependent on the activation of NMDA receptors and calcineurin. In a separate set of experiments I determined the effects of a range of novel AMPA receptor antagonists on synaptic transmission and seizure activity. Decanoic acid, a key component of the medium chain triglyceride ketogenic diet used in refractory epilepsy, has recently been shown to act as a non-competitive AMPA receptor antagonist. Here I showed that a range of structurally related compounds which also act as AMPA receptor antagonists are effective in in vitro models of seizure-like activity. I have further explored the mechanisms underlying decanoic acid's action. Decanoic acid is synergistic with the AMPA receptor antagonist, perampanel, and is not use-dependent. Moreover, I have shown that decanoic acid has an action at voltage-gated sodium channels to decrease the intrinsic excitability of neurons. Decanoic acid reduces the persistent sodium current, without altering the transient sodium current. Surprisingly, decanoic acid has minimal effect on in vivo status epilepticus (prolonged seizure activity) possibly because of rapid and extensive metabolism by the liver. Lastly, I undertook preliminary experiments in human neurons. Decanoic acid effectively reduces induced seizure-like activity in slices from surgically-resected human neocortical tissue. It inhibits AMPA receptor-mediated currents but does not alter intrinsic excitability, as in rat CA1, possibly due to regional differences in neuronal properties. My findings indicate that seizure activity rapidly changes the AMPA receptors expressed in the synapse and identify a range of compounds that target AMPA receptors, which are effective against seizure activity.
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Penn, Andrew Charles. "The role and regulation of AMPA receptor subunit variants." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611692.
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Needham, E. L. "AMPA receptors and auxiliary subunits in central synaptic transmission." Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1380162/.
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AMPA receptors (AMPARs) mediate the majority of fast excitatory synaptic transmission in the central nervous system (CNS). AMPARs are tetrameric assemblies of AMPAR subunits forming a functional ion channel gated by the binding of glutamate. The functional properties of AMPARs dictate key features of the excitatory postsynaptic current and they differ with receptor subunit composition (GluA1-4). The incorporation of GluA2 determines many key properties of AMPARs including their permeability to calcium. GluA2-lacking AMPARs are calcium permeable and their expression is tightly regulated. Transmembrane AMPAR regulatory proteins (TARPs) also play a vital role in the regulation of AMPAR properties. TARPs aid the trafficking of AMPARs to the neuronal surface and their synaptic targeting. They also regulate AMPAR channel properties and their gating. AMPARs are known to be dynamic at the neuronal surface. AMPAR density at the synapse changes with synaptic strength, as does their subunit composition. These regulated changes modify the AMPAR-mediated postsynaptic response. While these changes in synaptic AMPARs and synaptic strength are vital for functions such as learning and memory, the altered regulation of AMPARs is implicated in many pathophysiological states including many neurodegenerative diseases. By investigating the properties of AMPARs in central synaptic transmission, and in recombinant expression systems, I have examined the role of AMPARs in a specific disease, the expression of calcium-permeable AMPARs, and the role of TARPs in regulating AMPAR properties. The aim of this thesis was to investigate the function of AMPARs at intact synapses formed in vivo and in recombinant expression systems. My experiments have shown that excitatory and inhibitory synaptic transmission are both altered in the cerebellum of a mouse model of the most common progressive neurodegenerative disease of childhood, Batten disease. I have also shown that spinal motor neurons express a mixture of calcium permeable- and calcium impermeable AMPARs at the synapse. Additionally, my results suggest that the prototypical TARP, stargazin, appears to regulate a proportion of these AMPARs. Finally, I have considered the role of a protein related to the TARP family, γ-6, in the regulation of recombinant AMPAR properties. γ-6 was found to regulate AMPAR trafficking and pharmacology, but is unable to modify single-channel conductance.
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Yu, Chenlu [Verfasser], and Maximilian [Akademischer Betreuer] Ulbrich. "Stoichiometry of AMPA receptors measured by single molecule imaging." Freiburg : Universität, 2018. http://d-nb.info/1213244684/34.
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Pearce, Sarah Elizabeth. "The role of auxiliary subunits in AMPA receptor function." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10047515/.
Full textAbstract:
Glutamate receptors of the AMPA-subtype mediate the majority of fast excitatory neurotransmission in the central nervous system (CNS). These receptors are associated with auxiliary proteins that have been shown to affect AMPA receptor (AMPAR) properties. Transmembrane AMPAR Regulatory Proteins (TARPs) were the first identified AMPAR auxiliary subunits, and since then, further auxiliary subunits continue to be identified. In this thesis, I investigate the effects of a novel auxiliary protein candidate – FRRS1L – on AMPAR function, as well as the involvement of TARPs in mediating AMPAR plasticity in a model of ischaemic stroke. I show that when co-expressed with both homomeric GluA1 and heteromeric GluA1/GluA2 AMPAR subunits in tsA201 cells, FRRS1L slows recovery from receptor desensitization, without significant effect on other AMPAR properties. When the prototypical TARP stargazin is additionally co-expressed, the effect of FRRS1L is lost and the receptor properties appear as if only stargazin were associated. I examine the endogenous expression of FRRS1L in the CNS, and find that it is highly abundant in multiple brain regions including the hippocampus, cortex and cerebellum. In cultured hippocampal neurons, overexpressed FRRS1L does not influence mEPSC amplitude or frequency. In a model of ischaemic stroke, direct ASIC1-a activation through lowering of the pH (acidosis) is sufficient to drive AMPAR plasticity in cultured hippocampal neurons. This manifests as a decrease in the GluA2 subunit, resulting in an increase of CP-AMPARs in the membrane. I show that this change in AMPAR subunit expression following acidosis is likely accompanied by an increase in TARP γ-8 expression. Using various techniques, I explore the change in CPAMPAR expression and cell excitability. I show that following acidosis, there is an increase in Ca2+ entry into the cells, which is likely mediated through CPAMPARs.
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Yefimenko, Nosova Natalia. "Novel regulation of AMPA receptor function by interacting protein CPT1C." Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/396667.
Full textAbstract:
AMPA receptors (AMPARs) are responsible for the 90% of synaptic transmission and are involved in plasticity, developmental and neurological processes. Their function depends on the proteins interacting with the AMPAR complex, which determine their specific gating and trafficking properties and hence their specific roles. In addition to well-known interacting proteins of AMPARs, recent studies have described the CPT1C as an associated partner in the outer core of the AMPAR complex in the hippocampus, cortex and cerebellum.
CPT1C is a neuron specific homologue of the carnitine acyltransferase family of enzymes, which are involved in fatty acid oxidation at the mitochondria. Contrary to the rest of the CPT1 family, CPT1C localizes at the endoplasmic reticulum and apparently is not related with the functions that other CPT1s carry out. To elucidate the physiological role of CPT1C isoform different studies have been performed, showing that CPT1C is involved in energy homeostasis, control of body weight and motor function as well as behavioral learning mechanisms. Of note, CPT1C KO animals display impairments in spatial learning along with immature dendritic spines. Despite all these studies with CPT1C, including its interaction with AMPARs, it is unknown the CPT1C physiological relevance and role, particularly in the regulation of the AMPAR function and its implication in neurological diseases.
In this thesis we have described a novel role of CPT1C in AMPA receptor function regulation. More specifically, the results show that glutamate-evoked currents of the recombinant GluA1 receptors are increased when CPT1C is present and this effect is specific of the CPT1 isoform CPT1C, since CPT1A does not share the same pattern. The ER location of CPT1C seems to be crucial to modulate AMPAR surface expression since mislocalization of CPT1C avoids its AMPAR modulation. Co-localization studies confirmed that GluA1-CPT1C interaction happens at ER level but not at the cell surface.
On the other hand, no changes in current density have been found in cells expressing GluA2 subunit along with CPT1C indicating AMPA subunit specificity. Additionally, electrophysiological experiments have determined that GluA1 channel properties are no altered, thus indicating that the increased current is probably due to a rise in AMPAR number at the cell surface. Indeed, this hypothesis is corroborated by the findings from the immunofluorescence experiments, where surface expression of GluA1 is increased in the presence of CPT1C in heterologous systems and cortical neurons. In agreement with a putative role of CPT1C in determining the AMPAR content at synapse level, we have demonstrated that synaptic transmission is altered in CPT1C KO neurons.
In parallel, we have studied the molecular mechanisms of CPT1C effect on AMPARs. We have shown that the palmitoylable cysteine 585 of the GluA1 subunit is crucial for the CPT1C enhancement of AMPA receptors trafficking by using immunofluorescence and electrophysiological techniques. However, the palmitoylation state of this residue does not determine AMPAR-CPT1C interaction. We have found evidences for a supposed depalmitoylation activity by CPT1C studying the role of the C-terminus of CPT1C, which contains the residue His469 with catalytic activity. Specifically we have found that CPT1C H469A mutant form does not alter GluA1 induced whole-cell currents as the wild type CPT1C does indicating that the C-terminal catalytic domain plays a crucial role in GluA1 modulation. This is supported by the fact that Palmostatin B – a newly described palmitoyl thioesterase inhibitor – decreases the CPT1C effect on GluA1 induced currents, most likely by inhibiting its PTE activity.
In summary, this thesis unravels a novel regulation of AMPA receptor function by the interacting protein CPT1C, which modulates AMPA receptor trafficking and this effect depends on the catalytic domain of CPT1C C-terminal acting on the cysteine 585 of GluA1 AMPAR subunit.Los receptores de glutamato tipo AMPA son fundamentales en la transmisión excitatoria rápida que se da en el sistema nervioso central. A parte de su papel crucial en la comunicación neuronal, los receptores AMPA son responsables de ciertos tipos de plasticidad sináptica, siendo importantes en el desarrollo del sistema nervioso central además de estar involucrados en multitud de procesos patológicos y enfermedades neurodegenerativas. La función de los receptores AMPA depende principalmente de dos factores: la composición de las subunidades que lo conforman (el receptor propiamente dicho) y la presencia de proteínas que interactúan con el receptor y actúan como subunidades auxiliares. Estos dos factores establecen las características intrínsecas del canal así como las interacciones de los receptores AMPA con otras proteínas intracelulares que determinarán sus propiedades de tráfico (ensamblaje, exocitosis, endocitosis y anclaje sináptico) y en último término sus funciones en la neurona. Entre la gran cantidad de proteínas que interaccionan con los receptores AMPA, recientes estudios proteómicos han demostrado que la proteína CPT1C forma parte del conjunto macromolecular de los receptores AMPA en el tejido neuronal. El objetivo principal de esta tesis se ha focalizado en el estudio esta proteína (CPT1C) en el contexto de la función de los receptores AMPA debido a su interacción. Para ello se han utilizado técnicas electrofisiológicas, de inmunofluorescencia y de biología molecular y celular tanto en sistemas de expresión heterólogos como en cultivos de células neuronales. Los experimentos llevados al cabo durante la tesis han confirmado la interacción entre las dos proteínas y han atribuido un papel modulador de CPT1C en el trafico de los receptores AMPA. El efecto regulador de la CPT1C es dependiente de la composición del receptor, afectando de manera diferencial subtipos distintos de receptores AMPA. La proteína CPT1C aumenta el tráfico de los receptores AMPA a la superficie celular sin alterar sus propiedades biofísicas y sin interaccionar a nivel de membrana plasmática ambas proteínas. Además en esta tesis se han descrito los mecanismos implicados en la modulación de dichos receptores por parte de CPT1C, desentrañando un residuo cisteína concreto determinante para la modulación de los receptores AMPA por la CPT1C. Finalmente, los experimentos llevados a cabo en esta tesis nos indican que los efectos observados se deben a una posible depalmitoilación del receptor, lo cual lleva a un aumento de su capacidad de acumulación en la membrana. En resumen, los resultados obtenidos durante esta tesis demuestran que el número de receptores AMPA en las sinapsis está aumentado en presencia de CPT1C y este efecto es debido a la actividad catalítica de CPT1C.
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Yan, Yi. "The role of Akt in AMPA receptor insertion and LTP." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/31741.
Full textAbstract:
It has been widely accepted that long-term potentiation (LTP) in the hippocampal CA1
region mostly results from increased insertion of post-synaptic α-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid receptors (AMPARs). The previous
study in our lab has shown that activation of phosphatidylinositol 3-kinase (PI3K) by
selective stimulation of synaptic N-methyl-D-aspartate receptors (NMDARs) is required
for the increased cell surface expression of AMPARs and the consequent LTP. However,
the following signaling pathways still remain unknown. In the present study, the
involvement of Akt, the primary downstream protein kinase of PI3K, was examined with
a combination of electrophysiological, biochemical and molecular biological techniques.
The study found that Akt is required for the post-synaptic AMPAR insertion and LTP.
Furthermore, the threonine 840 (Thr840) on GluRl C-tail was identified as a novel Akt
phosphorylation site, suggesting a potential mechanism by which Akt contributes to
AMPAR incorporation and LTP.Medicine, Faculty of
Graduate
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Cēbers, Gvido. "Modulation of AMPA glutamate receptor functions in primary neuronal cultures /." Stockholm, 1999. http://diss.kib.ki.se/1999/91-628-3424-X/.
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Ripley, Beth Ann. "The role of postsynaptic AMPA receptors in stabilizing presynaptic inputs." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2008. http://wwwlib.umi.com/cr/ucsd/fullcit?p3307586.
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Thesis (Ph. D.)--University of California, San Diego, 2008.Title from first page of PDF file (viewed July 23, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 120-137).
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Gitelman, Julian. "Synaptic incorporation of GluA1-containing AMPA receptors during memory processes." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=110505.
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It is generally understood that modifications in synaptic strength are the basis for learning and memory and that the strength of a synapse is largely governed by the abundance and distribution of synaptic receptors, especially alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptors (AMPA receptors), which mediate most of the fast synaptic transmission in the brain. GluA1-containing AMPARs are incorporated into the synapse following activity and posttranslational modifications to the carboxyl-terminus affect which proteins interact with the receptor and determine whether the receptor is inserted or removed from the synapse. In vitro research has discovered that the phosphorylation of three serine residues contained on the carboxyl-terminus (Ser 818, Ser-831 and Ser-845) regulates GluA1 synaptic incorporation; however, in vivo research investigating the relative importance of these phosphorylation sites on long-term memory formation is currently limited to knock in studies.To block the interactions between these phosphorylation sites and their binding partners in an inducible, temporally sensitive manner, we infused interference peptides containing these residues during consolidation and reconsolidation. We hypothesized that if the synaptic incorporation of GluA1 containing AMPA receptors is required for memory formation, and if this incorporation required the residues contained on the interference peptide, we would see an impairment in long-term memory expression when the peptide was infused at the time of training, or at the time of retrieval.Infusing the interference peptide GluA1-CT, containing Ser-831 and Ser 845, 1 hour before auditory fear conditioning produced no impairment in memory expression 24 hours later. However, infusing the interference peptide GluA1-MPR, containing Ser-818, 1 hour before training did produce an impairment in memory expression 24 hours later. We did not observe an impairment in long-term memory expression when both peptides were infused 1 hour before memory reactivation.Il est généralement accepté que les modifications de la force synaptique sont à la base de l'apprentissage et la mémoire et que la force d'une synapse est largement régie par l'abondance et la distribution de récepteurs synaptiques, en particulier de récepteurs alpha-amino-3-hydroxy-5-méthyl-4- isoxazole propionate (récepteurs AMPA), qui interviennent dans la plupart des transmissions synaptiques rapides dans le cerveau. Les récepteurs AMPA contenant la sous-unité GluA1 sont incorporés dans la synapse suite à son activation et des modifications post-traductionnelles de l'extrémité carboxy-terminale influencent quelles protéines interagissent avec le récepteur et détermine si le récepteur est inséré ou retiré de la synapse. Des recherches in vitro ont découvert que la phosphorylation de trois résidus sérine contenus sur l'extrémité carboxy-terminale (Ser-818, Ser-831 et Ser-845) régie l'incorporation synaptique de GluA1; cependant, les recherches in vivo étudiant l'importance de ces sites de phosphorylation sur la formation de la mémoire à long terme est actuellement limitée à des études utilisant des « knock in ». Pour bloquer les interactions entre ces sites de phosphorylation et de leurs partenaires de liaison de manière inductible et temporellement sensibles, nous avons infusé des peptides d'interférence contenant ces résidus lors de la consolidation et la reconsolidation. Nous émettons l'hypothèse que si l'incorporation synaptique des récepteurs AMPA contenant GluA1 est nécessaire à la formation de la mémoire, et si cette incorporation exige les résidus contenus dans le peptide d'interférence, nous verrions une déficience dans l'expression de mémoire à long terme lorsque le peptide a été infusé au moment du conditionnement ou du rappel du souvenir.L'infusion du peptide d'interférence GluA1-CT, contenant les sérines Ser 831 et Ser-845, 1 heure avant le conditionnement de peur auditive n'a produit aucune altération dans l'expression de mémoire 24 heures plus tard. Cependant, l'infusion du peptide d'interférence GluA1-MPR, contenant la sérine Ser-818, 1 heure avant le conditionnement a produit une déficience dans l'expression de mémoire 24 heures plus tard. Nous n'avons pas observé d'altération dans l'expression de mémoire à long terme lorsque les deux peptides ont été infusés 1 heure avant la réactivation.
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Lam, Amy G. M. "Manipulation of metabotropic and AMPA glutamate receptors in the brain." Thesis, University of Glasgow, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300734.
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Nielsen, Thomas Aagaard. "Glutamate diffusion and AMPA receptor activation in the cerebellar glomerulus." Thesis, University College London (University of London), 2005. http://discovery.ucl.ac.uk/1445723/.
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Glutamate release onto a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) is the primary mechanism of fast synaptic transmission in the mammalian brain. Previous studies have revealed that at the cerebellar mossy-fibre to granule cell synapse, the AMPAR mediated synaptic current con sists of a fast-rising and a slow-rising component. The aim of this thesis is to examine the properties of release, diffusion and receptor activation underlying these two components. Two plausible mechanisms could underlie the slow-rising current: spillover of glutamate from neighbouring synaptic contacts and prolonged local release of glutamate via a narrow fusion pore. Using simulations of glutamate diffu sion and receptor activation, I show that lowering the diffusion coefficient of glutamate in the synaptic cleft (Dgjut), which is unknown but can be modulated with macromolecules, has different effects on currents mediated by these two mechanisms. Recordings of the effect of perfusion of dextran (43 kDa) are consis tent with the spillover model and also indicate that Dgiut is approximately 3-fold lower than in free solution. I show using simulations that linear diffusion cannot alone account for the acceleration of the decay of the synaptic current observed at this synapse in lower release probability, but that it can result from non-linear activation of AMPARs. Evidence is presented that diffusion is linear and only one vesicle is released per active zone. In addition, I have extended the diffusion-reaction model of the synapse to develop a framework for examining properties of synaptic AMPARs using glutamate uncaging. I demonstrate that certain kinetic properties of synap tic receptors can be measured using this technique and derive a kinetic model based on preliminary data. Together, these data fill shortcomings in our understanding of synaptic func tion. Based on the present results, I construct a model of synaptic transmission that explains previous observations.
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Kelly, L. "Regulation of calcium-permeable AMPA receptors at cerebellar interneuron synapses." Thesis, University College London (University of London), 2007. http://discovery.ucl.ac.uk/1444768/.
Full textAbstract:
Fast excitatory synaptic transmission in the central nervous system is mediated principally by glutamate, acting on AMPA receptors (AMPARs). The functional properties of these receptors reflect their subunit composition (GluR1-4) and dictate key features of the excitatory postsynaptic current, and thus the transmission process. Importantly, insertion or removal of AMPARs at the synapse underlies the expression of certain well-characterised forms of long-term synaptic plasticity. Recently, several additional forms of plasticity have been shown to involve the specific regulation of Ca2+-permeable (GluR2-lacking) AMPARs. At parallel fibre synapses onto cerebellar stellate cells, Ca2+ influx through AMPARs triggers an autoregulatory change in their subunit composition. In this thesis I have investigated factors that may trigger or influence this type of subunit change. I discovered that a switch in AMPAR subtype (from Ca2+-permeable to mainly Ca2+-iimpermeable AMPARs) occurs during development of stellate cells. This change is accompanied by a decrease in synaptic channel conductance. Activation of either mGluRs or GABABRs also results in switch in AMPAR subtype - a selective loss of synaptic Ca2+-permeable AMPARs, triggered by a rise in intracellular Ca2+. My experiments also reveal that both types of metabotropic receptor are tonically active, and therefore constitutively regulate subunit-specific synaptic targeting of AMPARs. My results identify a signalling mechanism likely to drive the dynamic switch in AMPAR Ca2+-permeability, and demonstrate that AMPAR subunit composition can be modified by postsynaptic actions of GABA, as well as glutamate.
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Shen, Guofu. "Bidirectional Regulation of AMPA and NMDA Receptors during Benzodiazepine Withdrawal." University of Toledo Health Science Campus / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=mco1242680312.
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Nettleton, Jilda Suzanne. "Summation of AMPA-mediated EPSPs in rat neocortical pyramidal neurons /." Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/10531.
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Benetti, Fernanda. "Desenvolvimento e validação de metodologia para determinação multirresíduo de glifosato e AMPA via CG-EM em amostras ambientais." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/75/75132/tde-20062011-111147/.
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O glifosato é o herbicida mais usado em todo o mundo. Sendo assim, é necessário que se tenham programas de monitoramento do seu uso, para garantir o bem estar da lavoura e da população. O seu metabólito principal é o ácido aminometilfosfônico (AMPA) que apesar de possuir baixa toxicidade, é mais persistente que o glifosato. O presente trabalho teve como objetivo desenvolver uma metodologia de análise para o glifosato e o AMPA por cromatografia gasosa acoplada à espectrometria de massas (CG/EM), a fim de avaliar possíveis contaminações em amostras ambientais nas imediações do Rio Monjolinho, em São Carlos. Para a faixa estudada (1,0 ug L-1 a 500 ug L-1, os limites de detecção e quantificação para o AMPA foram de 0,15 e 0,45 ug L-1 e para o glifosato, 0,67 e 2,02 ug L-1. As recuperações em água variaram entre 96,2 e 121% e para solo 70,1 a 119%. O método proposto apresentou boa linearidade, exatidão, seletividade e sensibilidade. A robustez foi avaliada de acordo com o teste de Youden. O procedimento de extração foi baseado em reações ácido-base e realizou-se etapa de clean-up para água e sedimento. Para os pontos amostrados, houve resíduo de AMPA em dois pontos (4,19 e 6,22 ug L-1). Os resultados encontrados para DBO foram altos, estando acima do limite estabelecido para um corpo d\'água Classe 3, de acordo com a CONAMA 357. Isso pode ter ocorrido devido à grande quantidade de esgoto despejado no leito do rio. Os valores de nitrogênio e fósforo também estão elevados, o que indica uma alta eutrofização do leito do rio. Vale ressaltar a necessidade de se ter uma legislação que estabeleça um limite máximo permitido para o AMPA, visto que ele é mais persistente no ambiente do que o glifosato.The glyphosate is the most widely used herbicide worldwide. Therefore, it is necessary to have programs for monitoring their use to ensure the welfare of the farming and population. Its main metabolite is the acid aminomethylphosphonic (AMPA) that despite having low toxicity, is more persistent than glyphosate. This study aimed to develop a methodology for analyzing glyphosate and AMPA by gas chromatography coupled to mass spectrometry (GC/MS) in order to assess possible contamination of samples environment in the vicinity of Monjolinho River in São Carlos. In the range studied (1.0 ug L-1 to 500 ug L-1, limits of detection and quantification were 0.15 and 0.45 ug L-1 for AMPA and 0.67 and 2.02 ug L-1 for glyphosate. The recoveries in water varied between 96.2 and 121% and for soil from 70.1 to 119%. The proposed method showed good linearity, accuracy, selectivity and sensitivity. The robustness was evaluated according to the Youden test. The extraction procedure was based on acid-base reactions and included a clean-up step for water and sediment. For the sampling sites, it was determined residual AMPA at two points (4.19 and 6.22 ug L-1). The results for BOD were high, being above the limit set for a waterbody Class 3, according to CONAMA 357. This may be due to large amount of sewage dumped into the river bed. The values of nitrogen and phosphorus are also high, which indicates a high eutrophication of the bed river. It is worth emphasizing the need of having a legislation that establishes a maximum allowed value for AMPA, whereas it is more persistent in environment than glyphosate.
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Renancio, Cédric. "Étude du trafic vésiculaire des récepteurs glutamatergiques de type AMPA : caractérisation d’une nouvelle protéine auxiliaire." Thesis, Bordeaux 2, 2013. http://www.theses.fr/2013BOR22139/document.
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Les récepteurs du glutamate de type AMPA (rAMPA) sont les acteurs principaux de la transmission synaptique excitatrice rapide. Leur abondance au niveau de la densité postsynaptique est essentielle pour l'établissement et le maintien de la fonction synaptique, et est le résultat d'un trafic hautement dynamique. De nombreuses études ont permis de caractériser les mécanismes de diffusion membranaire impliqués dans l’adressage des rAMPA jusqu’à la synapse. Le rôle majeur des protéines auxiliaires des rAMPA dans la modulation de cette étape de trafic a été démontré. Par ailleurs, il est suggéré que la localisation synaptique des rAMPA est aussi régulée lors des phases plus précoces du trafic intracellulaire, c’est-à-dire de l'appareil de Golgi vers la membrane plasmique via les vésicules post-Golgiennes. Cependant le trafic vésiculaire post-Golgien des rAMPA n'a jamais été visualisé et reste donc encore très mal compris. En collaboration avec l'équipe de Guus Smit (Amsterdam), j’ai participé à la caractérisation d’une nouvelle protéine auxiliaire des rAMPA, appelée Shisa6. Dans le cadre de ce projet, j’ai pu étudier le rôle de cette protéine sur la diffusion membranaire des rAMPA en utilisant une technique de suivi de particule unique (Quantum dot) développée au laboratoire. Mon projet de thèse principal a consisté à étudier le trafic vésiculaire post-Golgien des rAMPA par le développement d’une nouvelle méthode d’étude. En effet, l'échec dans la visualisation dynamique du trafic vésiculaire des récepteurs pourrait être expliqué par un faible rapport signal/bruit, conséquence d'une faible concentration vésiculaire en rAMPA combinée à un bruit de fond important dû aux marquages provenant du réticulum endoplasmique (RE) et de la membrane plasmique. Dans le but de surpasser cette difficulté, nous avons mis au point un outil ingénieux (système ARIAD) afin de bloquer les rAMPA dans le RE et contrôler, par l'ajout d'un ligand, leur sécrétion du RE jusqu'à la membrane plasmique. Grâce à cet outil, nous avons non seulement augmenté considérablement la concentration des rAMPA dans les vésicules post-Golgiennes, mais aussi éliminé le bruit de fond membranaire. Par la technique de FRAP nous avons pu éliminer le bruit de fond provenant du RE. Une telle approche, combinée à des techniques d'imagerie sur neurones vivants, nous a permis de visualiser pour la première fois le trafic vésiculaire post-Golgien des rAMPA et de l’étudierAMPA-type glutamate receptors (AMPAR) are the main actors of the fast excitatory synaptic transmission. Their abundance at the postsynaptic density is essential for the establishment and maintenance of synaptic function, and is the result of a highly dynamic trafficking. Many studies have characterized the membrane diffusion mechanisms involved in the AMPAR synaptic localization, and revealed the critical role of the AMPAR auxiliary proteins in the modulation of this trafficking. Furthermore, it is suggested that AMPAR synaptic localization is also regulated during the early steps of the intracellular trafficking, from the Golgi apparatus to the plasma membrane via the post-Golgi vesicles. However, the post-Golgi vesicular trafficking of AMPAR has never been visualized and therefore remains poorly understood. In collaboration with the Guus Smit team (Amsterdam), I participated in the caracterization of a novel AMPAR auxiliary protein called Shisa6. As part of this project, I studied the role of this protein on the AMPAR membrane diffusion, using a method of single particle tracking (Quantum dot) developed in the laboratory. My main thesis project was to study the post-Golgi vesicular trafficking of AMPAR through the development of a new experimental protocol. Indeed, the failure in the dynamic visualization of the receptor vesicular trafficking could be explained by a low signal/noise ratio resulting of a poor AMPAR vesicular concentration, combined with a high background noise due to receptors localized both in the endoplasmic reticulum (ER) and at the plasma membrane. In order to overcome this difficulty, we have used an ingenious tool (ARIAD system) so as to block AMPAR into the ER and, by adding a ligand, control their trafficking from the ER to the plasma membrane. Thanks to this tool we have not only significantly increased the AMPAR concentration in the post-Golgi vesicles, but also eliminated the plasma membrane background noise. The FRAP imaging technique was used in order to remove the ER background noise. Such methodological approach combined with imaging techniques in living neurons, allowed us to clearly visualize for the first time the post-Golgi vesicular trafficking of AMPAR, and to study the mechanisms involved in this trafficking
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Reng, Diana. "AMPA-([alpha]-amino-3-hydroxy-5-methyl-4-isoxazolpropionsäure) [AMPA-(Alpha-amino-3-hydroxy-5-methyl-4-isoxazolpropionsäure)] induzierte Exzitotoxizität im Innenohr der Taube (Columba livia)." [S.l.] : [s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=960082239.
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Hafner, Anne-Sophie. "Regulation of ampa receptor surface trafficking Through auxiliary protein interaction with psd-95." Thesis, Bordeaux 2, 2013. http://www.theses.fr/2013BOR22120/document.
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Les récepteurs du glutamate de type AMPA (rAMPA) sont les récepteurs ionotroniques responsables de la majeure partie des courants excitateurs rapides lors de la transmission synaptique dans le système nerveux central. Le nombre de rAMPA stabilisés à la synapse est responsable en partie de l’intensité de la transmission synaptique et de nombreux phénomènes de plasticité synaptique. Les rAMPA se répartissent en trois populations en équilibre dynamique: les récepteurs intracellulaires, les récepteurs extra-synaptiques, et les récepteurs synaptiques stabilisés au niveau de la densité post-synaptique. L’implication des protéines transmembranaires régulatrices des rAMPA (TARP) dans la stabilisation des rAMPA est établie, et repose au moins en partie sur la liaison de la protéine TARP γ-2 avec la protéine d’échafaudage PSD-95. Dans l’hippocampe, siège de nombreux phénomènes de plasticité, l’isoforme γ-8 est particulièrement enrichie. La TARP γ-8 a pour particularité de posséder un domaine C-terminal plus long que son homologue γ-2 et de s’exprimer au niveau synaptique et extra-synaptique. Mon travail de thèse à consisté à étudier les mécanismes moléculaires mis en jeu dans la régulation de la liaison des protéines TARP γ-2 et γ-8 avec la protéine PSD-95, ainsi que l’implication respective des deux isoformes dans la régulation de la mobilité latérale des rAMPA. Les résultats majeurs de cette étude sont : a) l’interaction entre γ-2 et PSD-95 est régulée par la longueur apparent du domaine C-terminal de γ-2 modulée par la phosphorylation; b) γ-8 lie PSD-95 dans les compartiments synaptiques et extra-synaptiques, toutefois cette interaction n’est pas corrélée avec une immobilisation des rAMPA. Ces résultats suggèrent que γ-2 et γ-8 jouent des rôles bien distincts dans l’adressage des rAMPA à la synapseAMPA type glutamate receptors (AMPARs) are ionotropic receptors responsible for most excitatory transmission in the central nervous system. The number of stabilized AMPARs in front of glutamate release sites determines in large part the strength of synaptic transmission and variation in this number is thought to underlie numerous forms of synaptic plasticity. AMPARs are present in three main subcellular pools between which they are in a dynamic equilibrium by processes of trafficking: intracellular receptors, extrasynaptic receptors, and synaptic receptors stabilized at the postsynaptic density (PSD). Transmembrane AMPAR regulatory proteins (TARPs) are known to be implicated in AMPAR stabilization at the synapse through the interaction of TARP γ-2/8 with the scaffolding protein PSD-95. In the hippocampus, a structure exhibiting various synaptic plasticity patterns, γ-8 is the most abundant TARP. This isoform is characterized by a longer C-terminal fragment than γ-2 and a synaptic and extrasynaptic localization. During my Ph.D, I studied the molecular mechanisms involved in the regulation of TARP γ-2 and γ-8 binding to PSD-95 and their respective roles in regulating AMPAR lateral mobility. The main results are: a) γ-2 interaction with PSD-95 is regulated by the apparent length of its C-terminus domain that is modulated by phosphorylation; b) γ-8 binds PSD-95 in synaptic and extrasynaptic compartment however this interaction is not correlated with AMPAR immobilization. Altogether, those results suggest that those two TARP isoforms have independent functional roles
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Jiang, Jianxiong Wooten Marie W. "Essential role for P62 in AMPA receptor trafficking and synaptic plasticity." Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SPRING/Biological_Sciences/Dissertation/Jiang_Jianxiong_41.pdf.
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Katchan, Ljudmila [Verfasser]. "Illuminating the function of AMPA receptors with fluorescent probes / Ljudmila Katchan." Berlin : Freie Universität Berlin, 2016. http://d-nb.info/112211110X/34.
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Fariba, Farnosh. "Modulation of the AMPA receptor by membrane cholesterol and neuroactive steroids." Thesis, University College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408144.
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Allison, Claire. "Investigations of regional changes in AMPA receptor characteristics during diazepam withdrawal." Thesis, University of Strathclyde, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249020.
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Ralph, G. Scott. "Investigating AMPA-receptor mediated neurotoxicity using novel neurone-specific adenoviral vectors." Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340079.
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Jones, Samantha Clair. "Pharmacological characterization of novel willardiine-derived AMPA and kainate receptor antagonists." Thesis, University of Bristol, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411016.
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Montgomery, Kyle. "Molecular factors that influence the binding of agonists to AMPA receptors /." Available to subscribers only, 2009. http://proquest.umi.com/pqdweb?did=1791777491&sid=6&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Thesis (Ph. D.)--Southern Illinois University Carbondale, 2009."Department of Pharmacology." Keywords: AMPA receptors, Ampakines, Guanine nucleotides, N-glycosylation, Tarps. Includes bibliographical references (p. 119-148). Also available online.
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Milstein, Aaron D. "Control of excitatory synaptic strength by auxiliary subunits of AMPA receptors." Diss., Search in ProQuest Dissertations & Theses. UC Only, 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3359580.
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Montgomery, Kyle Everett. "MOLECULAR FACTORS THAT INFLUENCE THE BINDING OF AGONISTS TO AMPA RECEPTORS." OpenSIUC, 2009. https://opensiuc.lib.siu.edu/dissertations/297.
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AMPA receptors mediate excitatory synaptic transmission throughout the central nervous system via activation by their natural agonist glutamate. Several other molecules have been recognized as receptor agonist or antagonist, and recently allosteric modulators have been developed that potentiate the currents generated by these receptors. The goal of this thesis has been to address specific and as yet unresolved questions regarding the binding interactions between the AMPA receptors and these classes of molecules. For instance AMPA receptors are seemingly converted to have lower affinity for agonist as they move towards synapses and we evaluate two hypotheses put forward to explain the molecular mechanisms responsible for this. Additionally, guanine nucleotides competitively inhibit AMPA receptors and a second goal has been to further characterize guanine nucleotide binding, and to create mutations that selectively diminish this so that the function of the inhibition can be evaluated. A third goal has been to characterize the molecular factors that influence the effects of the allosteric modulators in order to explain why their efficacy differs greatly between brain regions. Experiments pertaining to these three goals were carried out sequentially and are described below as Projects 1 (guanine nucleotide inhibition), Project 2 (agonist affinity), and Project 3 (allosteric modulators). Project 1. Guanine nucleotides competitively inhibit AMPA-Rs (AMPA receptors) and because this inhibition is ubiquitous among virtually all types of glutamate receptors from fish to mammals, it likely serves a physiological function. Evaluation of this would be greatly facilitated if nucleotide binding could be eliminated through mutations without altering other aspects of receptor function, or if compounds were discovered that selectively prevent nucleotide binding. It was previously reported that a lysine in the chick kainate binding protein (cKBP) is specifically involved in guanine nucleotide binding. Therefore we mutated the homologous lysine (K445) in AMPA-R subunit GluR1 plus 12 additional residues around the glutamate binding pocket with the expectation that this would reduce nucleotide binding even further. Nucleotide affinity was determined by measuring the displacement of [3H]fluorowillardiine. As expected, the guanine nucleotide affinity was decreased about five-fold in R1-K445A mutants and the agonist affinity was seemingly unchanged. However, when tested by electrophysiology, characteristics of the mutant such as desensitization and the EC50 for glutamate were found to be altered. None of the other mutations were more successful at decreasing nucleotide affinity selectively. Nonetheless, these studies have given new insight into the docking mode of guanine nucleotides. The loss of binding in R1-K445A was much larger for GTP and GDP than for GMP, and guanosine binding, which is much lower, was unaffected by the mutation. These data suggest that the first phosphate of GMP determines the higher affinity of the phosphorylated nucleotides, and that K445 stabilizes the binding of the second and third phosphates of GDP and GTP. This along with various other observations suggest that the guanine base docks deep within the agonist binding pocket and that bulky additions, such as the phosphates, are accommodated by projecting out of the cleft in the vicinity of lysine 445. However, the exact docking mode of guanine nucleotides would have to be determined by crystallography. Project 2. Agonist binding to AMPA-R in brain consists of a high and low affinity components with KDs of 9-28 nM and 190-700 nM. Previous studies have suggested that newly synthesized receptors have high affinity and are converted to lower affinity by a secondary process. Two particular processes have been implicated, namely the conversion of receptor glycosylation from immature to complex, and modulation by receptor associated proteins. Both hypotheses were evaluated in this project using homomeric receptors GluR1-4 expressed in HEK 293 cells. The role of glycosylation was tested mostly with GluR4 receptors because they are expressed in distinct populations that exhibit either immature or complex glycans and their binding consists of high and low affinity components similar to those previously seen in brain receptors. Cells were treated with castanospermine or deoxymannojirimycin to decrease the proportion of receptors with complex glycosylation, or with cycloheximide plus chloroquine to increase the number of receptors with complex glycosylation. Although 70% of receptors from cells treated with cyloheximide/chloroquine exhibited complex glycans compared to <5% with other treatments, the affinity decreased at most 2-fold. Also, the low affinity component was nearly 80% of the total binding in receptors that exhibited virtually no complex glycans. Taken together these data indicate that complex glycosylation is not the key factor that confers low affinity. To test the second hypothesis GluR1i or GluR2i were co-expressed with stargazin which associates to receptors in neurons and affects their kinetics and trafficking. Considering the affinities of the two components seen in brain, we expected stargazin to cause a 20-fold or greater decrease in binding affinity. This was not the case, however our results did suggest that stargazin caused the appearance of a low affinity component but this was small and remained largely masked by the more abundant high affinity component. Recently, experiments with brain membranes have revealed preliminary evidence that an associated protein of ~85kDa may cause receptors to have low affinity. This hypothesis is currently under investigation. Project 3. Ampakines are cognitive enhancers that potentiate AMPA receptor currents at excitatory synapses. The efficacy of these drugs varies substantially among neurons in different brain regions, being for example about three times larger in the hippocampus than in the thalamus. Binding assays have shown that these compounds also increase the affinity of receptors for agonists. Importantly, the efficacy of these drugs to increase synaptic responses and agonist binding exhibit a positive correlation. Indeed, we have found that the increase in agonist binding (Emax) induced by the prototypical ampakine CX546 is highly variable across eight brain regions and that there is a 3-fold difference between the hippocampus and the thalamus which is similar to the difference reported for physiological efficacy. Therefore, binding assays or receptor autoradiography can potentially be used to predict the physiological efficacy of these drugs in a particular brain region. An important goal of this project has been to identify factors that may be responsible for the regionally different efficacies. Ampakines show some preference for receptor subunits but various considerations suggest that other factors must be involved. In this project we evaluated the role of a novel class of proteins called TARPs (transmembrane AMPA receptor regulatory proteins) that have recently been discovered to be tightly associated with AMPA receptors and to regulate their kinetics. Four of these proteins, named lambda;2(stargazin),λ3,λ4,and λ8 are abundant in the brain, but they exhibit highly selective regional distribution. We determined the maximum increase in agonist binding (Emax ) caused by saturating CX546 in three different AMPA receptor subunits, GluR1i, GluR2i, and GluR4i without and with co-expression of the four TARPs. Without TARPs, both Glu2i and GluR4i showed an Emax value of 100% over baseline binding. Co-expression of TARPs increased the Emax in GluR2i and this was largest for λ3 and λ8 (~130%). However, TARPs decreased the Emax of CX546 in GluR4i and this was most notable with λ2 and λ4 (~72%). Agonist binding in GluR1i was increased by only 15% and it was not significantly changed by TARPs. The expression patterns of TARPs and AMPA-R subunits in the brain have been partially characterized in the literature. Thus, it was previously reported that GluR4i transcripts are abundant in the thalamus but minor in the hippocampus. Using western blots we confirmed that this is also true for protein content; in the thalamus expression of GluR1, GluR2, GluR3, and GluR4 was 4%, 33%, 40%, and 147% respectively, of that in the hippocampus. When considering the known expression patterns of TARP variants, the hippocampus can be described as being enriched in GluR2, λ3 and λ8 while GluR4, λ2 and λ4 are prevalent in the thalamus. In comparison between these specific subunit/TARP combinations, the Emax values for those representative of the hippocampus (GluR2i/λ3 or λ8) were ~2-times larger than the Emax values of thalamic combinations (R4i/λ2 or λ4). Thus we can conclude that the differences in the expression of both TARP variants and AMPA-R subunits are critical factors for determining the variable efficacy of ampakines across brain regions.
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Ni, Xianglian. "Developmental Regulation and Function of AMPA Receptor Subunits in Chicken Lumbar Motoneurons." ScholarWorks @ UVM, 2009. http://library.uvm.edu/dspace/bitstream/123456789/206/1/Ni%20Dissertation.pdf.
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Colombo, Sandro de Miranda. "Glifosato e ácido aminometilfosfônico: desenvolvimento de metodologias de análise por injeção sequencial e investigação sobre processos adsortivos e fisiológicos de interesse ambiental." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/46/46136/tde-31012012-151946/.
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Descreve-se o desenvolvimento de um método de análise por injeção sequencial para determinação de glifosato em formulações comerciais por voltametria de onda quadrada em eletrodo de gota de mercúrio. O glifosato foi derivatizado em modo estacionário com ácido nitroso para produção de N-nitroso glifosato, que é eletroativo. Os limites de detecção (LD) e quantificação (LQ) foram 0,7 e 2,4 mg L-1 (4 e 14 µmol L-1), respectivamente. O método foi aplicado a três formulações, obtendo resultados que diferiram do valor indicado pelo fabricante por -2,6, -0,8 e -28%. Em seguida descreve-se o desenvolvimento de um método de injeção seqüencial para a determinação fluorimétrica de glifosato, Esse método baseou-se em uma primeira etapa de conversão de glifosato a glicina por reação com hipoclorito de calcio, seguida por reação com o-ftaldialdeído na presença de 2-mercaptoetanol (OPA-MCE) em tampão borato (pH> 9) para produzir o composto fluorescente (2\'-hidroxietiltio)-2-N-alkilisoindol (excitação em 340 nm e emissão em 450 nm). O método apresentou resposta linear para concentrações entre 0,25 e 25,0 µmol L-1, com LD e LQ de 0,08 e 0,25 µmol L-1 (14 e 42 µg L-1), respectivamente, e frequência de amostragem de 18 análises por hora. O método foi aplicado para estudar as propriedades de adsorção / dessorção em um solo e em uma amostra de sedimento. Os dados das isotermas de adsorção e dessorção foram tratados pelas equações de Freundlich e Langmuir, que permitiram estimar uma capacidade de adsorção de 1384 ± 26 e 295 ± 30 mg kg-1 para as amostras de solo e sedimento, respectivamente. A determinação de glifosato e AMPA em amostras de água foi realizada por cromatografia por injeção sequencial com detecção fluorimétrica explorando as mesmas reações com hipoclorito e OPA-MCE. A solução transportadora com papel de fase móvel foi composta por mistura metanol: tampão fosfato 10 mmol L-1 (pH 6,8) na proporção 25:75 (v v-1). A frequência de amostragem foi de 6 análises por hora, com LD e LQ de 0,14 e 0,42 µmol L-1 para AMPA e 0,11 e 0,33 µmol L-1 para glifosato, respectivamente. Testes de adição e recuperação em amostras de águas naturais enriquecidas com 0,50 µmol L-1 desses compostos levaram a taxas de recuperação de 82 a 140% para AMPA e de 84 a 96% para glifosato. Investigou-se o efeito do herbicida em cultivos de duas espécies de microalgas marinhas - a Chlorophyta, Tetraselmis gracilis e a diatomácea, Phaeodactilum tricornutum. Para isso adicionou-se diferentes concentrações de glifosato (2 a 1000 mg L-1) a cultivos crescendo em fase exponencial. Doses de 2 e 50 mg L-1 provocaram leve aumento de crescimento algal quando comparados com o cultivo controle sem glifosato. O rendimento quântico da fotossíntese aumentou levemente em alguns dias no cultivo de P. tricornutum em concentrações baixas de glifosato. Na concentração de glifosato de 200 mg L-1 houve declínio do crescimento e acentuada queda do rendimento quântico da fluorescência da fotossíntese. Perfis dos aminoácidos aromáticos, tirosina, triptofano e fenilalanina apresentaram diferenças nas algas.We describe a development of a voltammetric method for determination of glyphosate in commercial formulations using sequential injection analysis to carry the sample to a flow cell adapted to the capillary of a mercury drop electrode. Glyphosate is batch-derivatized with nitrous acid in hydrochloric acid to produce N-nitroso glyphosate, which is electroactive. The limits of detection (LOD) and quantification (LOQ) were 0.7 and 2.4 mg L-1, respectively. The method was applied to three formulations, obtaining results that differed from the value indicated by the manufacturer by -2.6, -0.8 and -28%. Next, the thesis describes the development of a sequential injection method to automate the fluorimetric determination of glyphosate based on a first step of oxidation to glycine by hypochlorite, followed by reaction with o-phthaldialdehyde in presence of 2-mercaptoethanol (OPA-MCE) in borate buffer (pH>9) to produce a fluorescent 1-(2´-hydroxyethylthio)-2-N-alkylisoindole. The proposed method exhibited a linear response for glyphosate concentrations between 0.25 and 25.0 µmol L-1, with LOD and LOQ of 0.08 and 0.25 µmol L-1, respectively. The sampling rate of the method was 18 samples per hour. The method was applied to study adsorption/desorption properties in a soil and in a sediment sample. Adsorption and desorption isotherms were properly fitted by Freundlich and Langmuir equations, leading to adsorption capacities of 1384 ± 26 and 295 ± 30 mg kg-1 for the soil and sediment samples, respectively. Determination of glyphosate and AMPA in water samples was performed by sequential injection chromatography (SIC) with fluorimetric detection by exploiting the same reactions with hypochlorite and OPA-MCE. The carrier solution plays a role of mobile phase, being composed of 25:75 (v v-1) methanol : 10 mmol L-1 phosphate buffer (pH 6.8). The chromatographic step enhanced the method selectivity. The sampling throughput was 6 analyzes per hour with LOD and LOQ of 0.14 and 0.42 µmol L-1 for AMPA and 0.11 and 0.33 µmol L-1 for glyphosate, respectively. Recovery tests in natural water samples enriched with 0.50 µmol L-1 in the compounds led to recovery rates from 82 to 140% for AMPA and 84 to 96% for glyphosate. We investigated the effect of the herbicide on cultivation of two species of marine microalgae - the Chlorophyta, Tetraselmis gracilis and the diatomaceous Phaeodactilum tricornutum. To achieve this goal, different concentrations of glyphosate (2 to 1000 mg L-1) were added to cultures growing in exponential phase. Doses between 2 and 50 mg L-1 caused a slight increase in algal growth compared to the control culture without glyphosate. The quantum yield of photosynthesis increased slightly in some days in the cultivation of P. tricornutum at low concentrations of glyphosate. The glyphosate concentration of 200 mg L-1 decreases the cell growth and caused a marked decline in the fluorescence quantum yield of photosynthesis. Profiles of aromatic amino acids, tyrosine, tryptophan and phenylalanine differed in the algae
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Benetti, Fernanda. "Avaliação cromatográfica e estudos de sorção e de toxicidade em minhocas de deltametrina, glifosato e ácido aminometilfosfônico." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/75/75135/tde-18022016-143759/.
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No Brasil é sabido que o uso de insumos agrícolas para o melhoramento da produtividade é crescente. Dentre esses insumos, pode-se destacar o uso de pesticidas. Neste trabalho foi desenvolvida e validada metodologia para análise de deltametrina (um piretróide usado como inseticida) por CLAE/UV. Nessas amostras também foram avaliadas a presença de glifosato (uma glicina substituída usada como herbicida) e de seu metabólito, o AMPA, via CG/EM. Essas metodologias foram aplicadas para análise de amostras reais de água, solo e sedimento no município de São Carlos, a fim de avaliar a contaminação por esses xenobióticos. Para melhor elucidação do potencial contaminante e de lixiviação destes, avaliou-se sua interação com ácidos húmicos, além de estudos de adsorção em latossolo vermelho, onde se verificou a grande influência da matéria orgânica na retenção de xenobióticos no solo. A fim de propor um método de remediação de solos em casos de contaminação por derramamento de formulações comerciais, testes de toxicidade (mortalidade, biomassa e reprodução) envolvendo minhocas Eisenia foetida com adição de 3% de vermicomposto foram executados. Todo o trabalho foi desenvolvido respeitando os conceitos de Gestão de Qualidade contempladas na norma ISO 17025.In Brazil it is known that the use of agricultural inputs to improve productivity has been increasing. Among these inputs, we can highlight the use of pesticides. This work developed and validated a methodology for deltamethrin analysis (a pyrethroid used as insecticide) by HPLC/UV. These samples were evaluated in the presence of glyphosate (a substituted glycine used as herbicide) and its metabolite, AMPA, by GC/MS. These methodologies were applied to analyze real samples of water, soil and sediment in São Carlos in order to evaluate the contamination by these xenobiotics. To elucidate the potential contaminant and leaching of these, we also evaluated the interaction with humic acids, and adsorption studies were performed in red latosol where there was a great influence of organic matter on xenobiotics retention in the soil. So as to propose a method for remediation of soils in cases of contamination by shedding of commercial formulations in soil, three toxicity tests (mortality, biomass and reproduction) involving Eisenia foetida earthworms with the addition of 3% of hummus were performed. All the study was developed in compliance with the Quality Management concepts covered in ISO 17025.
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Procter, Mark James. "Ionotropic glutamate receptors and modulation of spinal nociceptive processing." Thesis, University of Bristol, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310687.
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