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Ibrahim Al-Osta, Mariusz Mucha, Daniel Pereda, Marta Piqué-Gili, Albert E Okorocha, Roisin Thomas, Nicholas A Hartell
Genetically encoded calcium indicators (GECIs) have gained widespread use for measurement of neuronal activity but their low expression levels in transgenic mice tend to limit sensitivity. We have developed a transgenic mouse line (SyG37) that expresses a ratiometric calcium sensor, SyGCaMP2-mCherry, that is expressed throughout the brain but targeted to presynaptic terminals. Within the CA1 and CA3 regions of hippocampus of male and female mice, SyGaMP2 fluorescence responds linearly up to 10 electrical stimuli at frequencies up to 100 Hz and it can detect responses to a single stimulus...
2018: Frontiers in Cellular Neuroscience
Tingting Zhang, Zhaochun Shi, Ya Wang, Ling Wang, Baofeng Zhang, Guiquan Chen, Qi Wan, Ling Chen
AIM: Loss-of-function mutation of Akt3 in humans has been associated with microcephaly and cognitive defects. Two Akt isoforms, Akt1 and Akt3, are highly expressed in hippocampal pyramidal cells. We explored the roles of Akt1 and Akt3, respectively, in spatial cognition and underlying mechanisms. METHODS: We used Akt1 knockout (Akt1-KO) and Akt3 knockout (Akt3-KO) mice to examine the influence of Akt1 and Akt3 deficiency on spatial memory, as well as induction and maintenance of hippocampal CA1 NMDA receptor-dependent and protein synthesis-dependent long-term potentiation (LTP)...
July 27, 2018: Acta Physiologica
Blanka R Szulc, Stephen T Hilton, Arnaud J Ruiz
We have synthesized a novel small molecule based on the pyrrolidinone-containing core structure of clausenamide, which is a candidate anti-dementia drug. The synthetic route yielded multi-gram quantities of an isomeric racemate mixture in a short number of steps. When tested in hippocampal slices from young adult rats the compound enhanced AMPA receptor-mediated signalling at mossy fibre synapses, and potentiated inward currents evoked by local application of l-glutamate onto CA3 pyramidal neurons. It facilitated the induction of mossy fibre LTP, but the magnitude of potentiation was smaller than that observed in untreated slices...
July 22, 2018: Molecular and Cellular Neurosciences
Chen Tian, Yuni Kay, Anastasiia Sadybekov, Sadhna Rao, Vsevolod Katritch, Bruce E Herring
The small GTPase Rac1 promotes actin polymerization and plays a critical and increasingly appreciated role in the development and plasticity of glutamatergic synapses. Growing evidence suggests that disruption of the Rac1 signaling pathway at glutamatergic synapses contributes to Autism Spectrum Disorder/intellectual disability (ASD/ID)-related behaviors seen in animal models of ASD/ID. Rac1 has also been proposed as a strong candidate of convergence for many factors implicated in the development of ASD/ID...
2018: Frontiers in Molecular Neuroscience
Gerhard Rammes, Franziska Seeser, Korinna Mattusch, Kaichuan Zhu, Laura Haas, Markus Kummer, Michael Heneka, Jochen Herms, Chris G Parsons
Aβ1-42 is well accepted to be a primary early pathogenic agent in Alzheimer's disease (AD). However, other amyloid peptides are now gaining considerable attention as potential key participants in AD due to their proposed higher neuronal toxicity. Impairment of the glutamatergic system is also widely accepted to be associated with pathomechanisms underlying AD. There is ample evidence that Aβ1-42 affects GLUN2B subunit containing N-methyl-D-aspartate receptor function and abolishes the induction of long term potentiation (LTP)...
July 14, 2018: Neuropharmacology
David M Bannerman, Thilo Borchardt, Vidar Jensen, Andrey Rozov, Nadia N Haj-Yasein, Nail Burnashev, Daniel Zamanillo, Thorsten Bus, Isabel Grube, Giselind Adelmann, J Nicholas P Rawlins, Rolf Sprengel
The GluA1 subunit of the L-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) plays a crucial, but highly selective, role in cognitive function. Here we analyzed AMPAR expression, AMPAR distribution and spatial learning in mice ( Gria1R/R ), expressing the "trafficking compromised" GluA1(Q600R) point mutation. Our analysis revealed somatic accumulation and reduction of GluA1(Q600R) and GluA2, but only slightly reduced CA1 synaptic localization in hippocampi of adult Gria1R/R mice...
2018: Frontiers in Molecular Neuroscience
Samantha Baron, Roberto A Barrero, Michael Black, Matthew I Bellgard, Elsie M S van Dalen, Josephus Fourie, Christine Maritz-Olivier
The widespread geographical distribution of Rhipicephalus decoloratus in southern Africa and its ability to transmit the pathogens causing redwater, gallsickness and spirochaetosis in cattle makes this hematophagous ectoparasite of economic importance. In South Africa, the most commonly used chemical acaricides to control tick populations are pyrethroids and amitraz. The current amitraz resistance mechanism described in R. microplus, from South Africa and Australia, involves mutations in the octopamine receptor, but it is unlikely that this will be the only contributing factor to mediate resistance...
June 18, 2018: International Journal for Parasitology, Drugs and Drug Resistance
G Antunes, F M Simoes-de-Souza
Historically, long-term potentiation (LTP) and long-term depression (LTD), the best-characterized forms of long-term synaptic plasticity, are viewed as experience-dependent and input-specific processes. However, cumulative experimental and theoretical data have demonstrated that LTP and LTD can promote compensatory alterations in non-stimulated synapses. In this work, we have developed a computational model of a tridimensional spiny dendritic segment to investigate the role of AMPA receptor (AMPAR) trafficking during synaptic plasticity at specific synapses and its consequences for the populations of AMPAR at nearby synapses...
July 9, 2018: Scientific Reports
Bo Am Seo, Taesup Cho, Daniel Z Lee, Joong-Jae Lee, Boyoung Lee, Seong-Wook Kim, Hee-Sup Shin, Myoung-Goo Kang
Mutations in the human LARGE gene result in severe intellectual disability and muscular dystrophy. How LARGE mutation leads to intellectual disability, however, is unclear. In our proteomic study, LARGE was found to be a component of the AMPA-type glutamate receptor (AMPA-R) protein complex, a main player for learning and memory in the brain. Here, our functional study of LARGE showed that LARGE at the Golgi apparatus (Golgi) negatively controlled AMPA-R trafficking from the Golgi to the plasma membrane, leading to down-regulated surface and synaptic AMPA-R targeting...
July 3, 2018: Proceedings of the National Academy of Sciences of the United States of America
Patricio Opazo, Silvia Viana da Silva, Mario Carta, Christelle Breillat, Steven J Coultrap, Dolors Grillo-Bosch, Matthieu Sainlos, Françoise Coussen, K Ulrich Bayer, Christophe Mulle, Daniel Choquet
Alzheimer's disease (AD) is emerging as a synaptopathology driven by metaplasticity. Indeed, reminiscent of metaplasticity, oligomeric forms of the amyloid-β peptide (oAβ) prevent induction of long-term potentiation (LTP) via the prior activation of GluN2B-containing NMDA receptors (NMDARs). However, the downstream Ca2+ -dependent signaling molecules that mediate aberrant metaplasticity are unknown. In this study, we show that oAβ promotes the activation of Ca2+ /calmodulin-dependent kinase II (CaMKII) via GluN2B-containing NMDARs...
June 12, 2018: Cell Reports
Daniel P Radin, Steven Johnson, Richard Purcell, Arnold S Lippa
Neurotrophin dysregulation has been implicated in a large number of neurodegenerative and neuropsychiatric diseases. Unfortunately, neurotrophins cannot cross the blood brain barrier thus, novel means of up regulating their expression are greatly needed. It has been demonstrated previously that neurotrophins are up regulated in response to increases in brain activity. Therefore, molecules that act as cognitive enhancers may provide a clinical means of up regulating neurotrophin expression. Ampakines are a class of molecules that act as positive allosteric modulators of AMPA-type glutamate receptors...
September 2018: Biomedicine & Pharmacotherapy, Biomédecine & Pharmacothérapie
Rodrigo Bainy Leal, Mark William Lopes, Douglas Affonso Formolo, Cristiane Ribeiro de Carvalho, Alexandre Ademar Hoeller, Alexandra Latini, Daniel Santos Sousa, Peter Wolf, Rui Daniel Prediger, Zuner Assis Bortolotto, Marcelo Neves Linhares, Kátia Lin, Roger Walz
Fear is a conscious state caused by exposure to real or imagined threats that trigger stress responses that affect the body and brain, particularly limbic structures. A sub-group of patients with mesial temporal lobe epilepsy related to hippocampus sclerosis (MTLE-HS) have seizures with fear, which is called ictal fear (IF), due to epileptic activity within the brain defensive survival circuit structures. Synaptic transmission efficacy can be bi-directionally modified through potentiation (long-term potentiation (LTP)) or depression (long-term depression (LTD)) as well as the phosphorylation state of Ser831 and Ser845 sites at the GluA1 subunit of the glutamate AMPA receptors, which has been characterized as a critical event for this synaptic plasticity...
June 7, 2018: Molecular Psychiatry
Xiaoxiu Tie, Shuo Li, Yilin Feng, Biqin Lai, Sheng Liu, Bin Jiang
In the visual cortex, sensory deprivation causes global augmentation of the amplitude of AMPA receptor-mediated miniature EPSCs in layer 2/3 pyramidal cells and enhancement of NMDA receptor-dependent long-term potentiation (LTP) in cells activated in layer 4, effects that are both rapidly reversed by light exposure. Layer 2/3 pyramidal cells receive both feedforward input from layer 4 and intra-cortical lateral input from the same layer, LTP is mainly induced by the former input. Whether feedforward excitatory synaptic strength is affected by visual deprivation and light exposure, how this synaptic strength correlates with the magnitude of LTP in this pathway, and the underlying mechanism have not been explored...
August 1, 2018: Neuroscience
Peter Helfer, Thomas R Shultz
In long-term potentiation (LTP), one of the most studied types of neural plasticity, synaptic strength is persistently increased in response to stimulation. Although a number of different proteins have been implicated in the sub-cellular molecular processes underlying induction and maintenance of LTP, the precise mechanisms remain unknown. A particular challenge is to demonstrate that a proposed molecular mechanism can provide the level of stability needed to maintain memories for months or longer, in spite of the fact that many of the participating molecules have much shorter life spans...
May 2018: PLoS Computational Biology
Mehdi Bhouri, Wade Morishita, Paul Temkin, Debanjan Goswami, Hiroshi Kawabe, Nils Brose, Thomas C Südhof, Ann Marie Craig, Tabrez J Siddiqui, Robert Malenka
Leucine-rich repeat transmembrane (LRRTM) proteins are synaptic cell adhesion molecules that influence synapse formation and function. They are genetically associated with neuropsychiatric disorders, and via their synaptic actions likely regulate the establishment and function of neural circuits in the mammalian brain. Here, we take advantage of the generation of a LRRTM1 and LRRTM2 double conditional knockout mouse ( LRRTM1,2 cKO) to examine the role of LRRTM1,2 at mature excitatory synapses in hippocampal CA1 pyramidal neurons...
June 5, 2018: Proceedings of the National Academy of Sciences of the United States of America
Liqi Tong, G Aleph Prieto, Carl W Cotman
BACKGROUND: Brain inflammation including increases in inflammatory cytokines such as IL-1β is widely believed to contribute to the pathophysiology of Alzheimer's disease. Although IL-1β-induced impairments in long-term potentiation (LTP) in acute hippocampal slices and memory functions in vivo have been well documented, the neuron-specific molecular mechanisms of IL-1β-mediated impairments of LTP and memory remain unclear. METHODS: This study uses an in vitro approach in primary hippocampal neurons to evaluate the effect of IL-1β on chemical LTP (cLTP)-induced structural plasticity and signaling...
April 30, 2018: Journal of Neuroinflammation
Roger L Papke, Can Peng, Ashok Kumar, Clare Stokes
Long-term potentiation (LTP) in the dentate gyrus was previously shown to be enhanced by nicotine, an effect dependent on both homomeric α7 and heteromeric α2β2 nicotinic acetylcholine receptors (nAChR). In our experiments, bath-applied nicotine produced no significant enhancement of LTP. The α7 nAChR silent agonist NS6740, a weak activator of α7 nAChR ion channels but an effective modulator of the cholinergic anti-inflammatory pathway, decreased LTP and, additionally, produced a substantial reduction in the baseline synaptic function prior to the high frequency stimulation used to induce LTP...
June 11, 2018: Neuroscience Letters
Achim Peters, Cordula Reisch, Dirk Langemann
In cognitive memory, long-term potentiation (LTP) has been shown to occur when presynaptic and postsynaptic activities are highly correlated and glucocorticoid concentrations are in an optimal (i.e., low normal) range. In all other conditions, LTP is attenuated or even long-term depression (LTD) occurs. In this paper, we focus on NMDA receptor (NMDA-R)-dependent LTP and LTD, two processes involving various molecular mechanisms. To understand which of these mechanisms are indispensable for explaining the experimental evidence reported in the literature, we here propose a parsimonious model of NMDA-R-dependent synaptic plasticity...
January 2018: ENeuro
Nengyin Sheng, Michael A Bemben, Javier Díaz-Alonso, Wucheng Tao, Yun Stone Shi, Roger A Nicoll
Long-term potentiation (LTP) is a persistent strengthening of synaptic transmission in the brain and is arguably the most compelling cellular and molecular model for learning and memory. Previous work found that both AMPA receptors and exogenously expressed kainate receptors are equally capable of expressing LTP, despite their limited homology and their association with distinct auxiliary subunits, indicating that LTP is far more promiscuous than previously thought. What might these two subtypes of glutamate receptor have in common? Using a single-cell molecular replacement strategy, we demonstrate that the AMPA receptor auxiliary subunit TARP γ-8, via its PDZ-binding motif, is indispensable for both basal synaptic transmission and LTP...
April 10, 2018: Proceedings of the National Academy of Sciences of the United States of America
Ya Wang, Tingting Chen, Zihao Yuan, Yajie Zhang, Baofeng Zhang, Liandong Zhao, Ling Chen
Statins by reducing farnesyl-pyrophosphate or farnesyl transferase inhibitors have been demonstrated to enhance spatial memory and long-term potentiation (LTP). The objective of this study was to investigate effects of the synthetic Ras inhibitor S-trans, trans-farnesylthiosalicylic acid (FTS) on spatial cognitive function in adult mice, synaptic plasticity in hippocampal CA1 regions, and NMDA receptor (NMDAr) activity of pyramidal cells. Here, we show that administering FTS (5 mg/kg, i.p.) enhanced spatial cognitive performance, as assessed via Morris water maze and Y-maze tests...
September 1, 2018: Neuropharmacology
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