Haut PDF Kinase C substrates and synaptic plasticity in Aplysia

Kinase C substrates and synaptic plasticity in Aplysia

Kinase C substrates and synaptic plasticity in Aplysia

Understanding how memories are stored and retrieved has been the goal of work in several scientific disciplines, including neuroscience, neuropsychology, psychology, and cognitive scienc[r]

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Alternative Functions of Core Cell Cycle Regulators in Neuronal Migration, Neuronal Maturation, and Synaptic Plasticity

Alternative Functions of Core Cell Cycle Regulators in Neuronal Migration, Neuronal Maturation, and Synaptic Plasticity

Spiking dendrites with Plk2 Polo-like kinases (PLKs) are evolutionarily conserved serine-threonine kinases that contain conserved polo-boxes and play important roles during cell cycle progression and genotoxic stress (Barr et al., 2004). Comprised of four members (Plk1-4), substrate specificity is often dictated by PLK localization and recognition of phosphorylated substrates via polo-box domains (PBDs). The most extensively studied member of this family, Plk1, was originally identified in a yeast screen for mutants defective in cell division (Hartwell et al., 1973). Since that pioneering study, Plk1 has been shown to regulate almost every key step in G2 and mitosis, including mitotic entry, centrosome maturation, cohesin release from sister chromatids, chromosomal segregation, and cytokinesis (Petronczki et al., 2008). Consistent with its mitotic function, Plk1 is localized to centrosomes and kinetochores during mitosis and its expression increases during late S phase and persists into mitosis. Plk1 contributes to these various processes through phosphorylation of multiple targets, including Wee1 and Myt1 kinases (mitotic entry), Cdc25 (mitotic entry), Nlp1 (centrosomal maturation), γ-tubulins (centrosomal maturation), cohesin (sister chromatid separation), APC/C subunits (chromosomal
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Activity-Dependent p25 Generation Regulates Synaptic Plasticity and Aβ-Induced Cognitive Impairment

Activity-Dependent p25 Generation Regulates Synaptic Plasticity and Aβ-Induced Cognitive Impairment

In an effort to elaborate the mechanisms that lead to p25 generation, we first used calpeptin to inhibit calpain, which cleaves p35 to p25 following neurotoxic stimuli. NMDA treatment of acute hippocampal slices in the presence of calpeptin substantially reduced p25 levels, suggesting that calpain is required for activity-dependent p25 liberation (Figure 1D). Next, we blocked α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) and NMDA receptors (NMDARs), which mainly govern postsynaptic Ca 2+ influx under physiological conditions (Collingridge et al., 2004). Incubation with the NMDAR antagonist APV, but not the AMPAR antagonist CNQX, severely diminished NMDA-induced p25 generation (Figure 1D). In addition, inhibition of GluN2B, but not GluN2A (using ifenprodil and NVP-AAM077, respectively), also led to reduced p25 levels (Figure 1D). The Ca 2+ / calmodulin kinase CaMKIIα, which plays a prominent role in synaptic plasticity and memory formation, interacts with p35 in a Ca 2+ - and NMDAR-dependent manner (Dhavan et al., 2002). Prompted by these observations, we treated acute hippocampal slices with the specific CaMKIIα inhibitor, KN-62, and showed that this was sufficient to abolish NMDA- induced p25 generation (Figure 1D). Finally, immunoprecipitation (IP) experiments revealed that both CaMKIIα and GluN2B interact with p35 in a complex that also contains calpain 1 at the hippocampal postsynaptic density (PSD) (Figures 1E and S1B). Together, these results suggest a signaling cascade in which activation of NMDAR stimulates calpain- mediated p35 cleavage and the liberation of p25 from PSD (Figure S1C) in a GluN2B- and CaMKIIα-dependent manner.
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Neuronal AMP-activated protein kinase hyper-activation induces synaptic loss by an autophagy-mediated process

Neuronal AMP-activated protein kinase hyper-activation induces synaptic loss by an autophagy-mediated process

While physiological synapse elimination, known as synaptic pruning, occurs during adolescence in humans, synaptic loss in adults is associated with cognitive impairments and is an early hallmark of neurodegenera- tive diseases including Alzheimer ’s 3 . However, the exact cellular and molecular mechanisms that are responsible for synaptic loss remain poorly understood. Nonetheless, synaptic proteins elimination could be mediated through autophagy-dependent processes. For instance, AMPA receptors are degraded through autophagy after chemical long-term depression 36 . In addition, proper regulation of autophagy is necessary to preserve neuronal integrity. In particular, downregulation of Atg7, an enzyme required for autophagosome formation, significantly reduces spines elimination in primary neurons 37 . Further studies showed that Atg5 or Atg7 knockout in animal models leads to neurodegeneration 38 , 39 . Here, we extend on these pre- vious findings and demonstrate that post-synaptic pro- teins elimination, at least for PSD-95, GluN1, and GluA1, is mediated by an AMPK-driven autophagy-dependent process. However, how these post-synaptic components are targeted for lysosomal degradation remains to be established. It is possible that ubiquitination could be involved. Indeed, selective autophagy is a process that degrades K63-linked polyubiquitinated chained or monoubiquitinated substrates 40 , 41 . In this process, the polyubiquitin chain is recognized by adaptor proteins, such as p62, which act as bridges to link ubiquitin to autophagosomes 42 . Interestingly, PSD-95 was reported to undergo K63 polyubiquitination 43 , and the ubiquitination of GluA1 in response to AMPA was reported to mediate the endocytosis and lysosomal trafficking of GluA1- containing AMPA receptors 44 . Intriguingly, our results suggest that pre-synaptic proteins (SNAP25, synapsin, and Munc) are eliminated following AMPK hyper- activation by a process that is not dependent on ULK1-
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LTP inhibits LTD in the hippocampus via regulation of GSK3beta.: A role for GSK3beta in synaptic plasticity

LTP inhibits LTD in the hippocampus via regulation of GSK3beta.: A role for GSK3beta in synaptic plasticity

(approximately 1.25 mm 2 ) surrounding the stimulating electrode was then dissected and homogenised. Tetanic stimulation comprised delivering 100 stimuli at 100 Hz to three separate locations. GSK3β kinase assay after LTD – To measure GSK3  activity in hippocampal slices following electrode induced LTD (900 stimuli delivered at 3 Hz) microdissected areas of slices were solubilized and 30  g of the lysate was used for each assay as described (Li et al., 2003) with some modifications. Briefly, the kinase reaction occurred in a 50  l total volume containing 20 mM MOPS pH 7.4, 25 mM  -glycerol phosphate, 5 mM EGTA, 1 mM NA 3 VO 4 , 1 mM DTT, 15 mM MgCl 2 , 100  M cold ATP, 7.5  l phosphoglycogen synthase peptide-2 (1mg/ml stock solution, Upstate, USA), 30  g whole slice lysate (10  l in volume) or 10  l of water as negative control, and 2.5  Ci
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The role of GSK-3 in synaptic plasticity.

The role of GSK-3 in synaptic plasticity.

Kozlovsky N, Belmaker RH & Agam G (2002). GSK-3 and the neurodevelopmental hypothesis of schizophrenia. Eur Neuropsychopharmacol, 12: 13-25. Lee YI, Seo M, Kim Y, Kim SY, Kang UG, Kim YS & Juhnn YS (2005). Membrane depolarization induces the undulating phosphorylation/dephosphorylation of glycogen synthase kinase 3beta, and this dephosphorylation involves protein phosphatases 2A and 2B in SH-SY5Y human neuroblastoma cells. J Biol Chem, 280: 22044-52.

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Regulation of glutamatergic neurotransmission, synaptic plasticity, sleep and behavior by D2-GSK3B-FXR1

Regulation of glutamatergic neurotransmission, synaptic plasticity, sleep and behavior by D2-GSK3B-FXR1

10 β-Arrestin-2-AKT-GSK3β signaling downstream of D2 receptor Several studies indicated that apart from G protein-mediated signaling stimulation of D2 receptors result in modulation of AKT and GSK3 activity (Beaulieu et al., 2009). AKT is a major serine-threonine kinase which is involved in the regulation of synaptic plasticity, monoamine transporter trafficking, neuron morphology, and fate. Activated AKT phosphorylates other proteins including GSK3. The inhibitory phosphorylation of GSK3 occurs at N-terminal serine residues, GSK3α at Ser21 and GSK3 at ser9 by AKT (Cross et al., 1995). GSK3 is a highly conserved serine- threonine kinase, which exists under 2 isoforms GSK3α and  which are encoded by distinct gene loci. In contrast to several other kinases, GSK3 is constitutively active and can be negatively regulated through phosphorylation and complex formation. The first evidence for regulation of AKT and GSK3 by dopamine came from a pioneering study on DA transporter knockout (DAT-KO) mice. These animals exhibit impaired DA reuptake leading to a ~5 fold elevation of extracellular DA levels in the striatum (Gainetdinov et al., 1999; Giros et al., 1996). This state of hyperdopaminergia results, among other consequences, in a reduction of AKT phosphorylation/activity and activation of GSK3α and GSK3β (Beaulieu et al., 2004). The reverse effect was observed when DA was depleted in the striatum following administration of an inhibitor of DA synthesis (Beaulieu et al., 2004; Bychkov et al., 2007). Administration of DA receptor agonist amphetamine, methamphetamine or apomorphine to wild type mice also decreased AKT activity and resulted in increased GSK3α and GSK3β activity (Beaulieu et al., 2004; Bychkov et al., 2007; Chen et al., 2007b).
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Chronic Sodium Selenate Treatment Restores Deficits in Cognition and Synaptic Plasticity in a Murine Model of Tauopathy

Chronic Sodium Selenate Treatment Restores Deficits in Cognition and Synaptic Plasticity in a Murine Model of Tauopathy

tau proteins into neurofibrillary tangles (NFTs; Buée et al., 2010; Querfurth and LaFerla, 2010; Masters et al., 2015 ). The spatiotemporal progression of NFTs from the entorhinal cortex and the hippocampus to the isocortical areas has been reported to correlate well with cognitive deficits and disease progression. Thus, it is Tau pathology and not Aβ-mediated functional deterioration that turned out to correlate better with the severity of dementia ( Gomez-Isla et al., 1997; Braak et al., 1998; Nelson et al., 2012; Brier et al., 2016 ). In accordance with the lower correlation between Aβ-pathology and AD progression, attempts to delay or reverse AD pathology by either removing Aβ or reducing its production had so far not the expected outcome in clinical studies ( Lovestone and Manji, 2020; Sabbagh, 2020 ). It was therefore logical that tau has become the next main target for AD modifying strategies. Apart from the many ongoing Tau-targeting passive and active immunization studies, the diversity of mechanisms that contribute to Tau pathology (e.g., hyperphosphorylation, acetylation, N-glycosylation, and truncation) offers multiple targets for therapy development ( Congdon and Sigurdsson, 2018 ). Strategies that target early pathological Tau mechanisms such as Tau hyperphosphorylation and aggregation meet ideally the requirement to shift the time of therapeutic interventions to very early stages of AD. Not only the degree of hyperphosphorylation is decisive for Tau pathology but also the specific pattern of Tau hyperphosphorylation, i.e., which of the many phosphorylations sites of Tau ( Sergeant et al., 2008 ) are (hyper)phosphorylated under the particular pathological condition. These pathological Tau phosphorylation patterns are the result of an intricate balance between the activity of Tau kinases, such as glycogen synthase kinase-3β (GSK3β) as the major Tau kinase, and phosphatases with protein phosphatase 2A (PP2A) as the main representative ( Liu et al., 2005; Kremer et al., 2011; Martin et al., 2013 ). Thus, therapeutic reduction of Tau hyperphosphorylation and subsequent aggregation can be either achieved by inhibition of Tau kinases or activation of phosphatases. Suitable candidate therapeutic compounds should be easy-to-administer, free of toxic side-effects in a broad dose range and show excellent bioavailability and CNS penetrating properties.
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en fr Conditions for the emergence of corticostriatal synaptic plasticity Conditions pour l'apparition de plasticité synaptique corticostriatale

25 glutamine by the enzyme glutamine synthetase. However, during periods of high neuronal activity up to 50% of the intracellular glutamate in astrocytes following uptake may alternatively be deami- nated to form a-ketoglutarate and enter the TCA cycle (McKenna, 2007; Robinson and Jackson, 2016; Stobart and Anderson, 2013). Astrocytic glutamine is subsequently transported out of astro- cytes and into neurons, where it is used as a precursor for glutamate synthesis, forming a glutamate- glutamine cycle (Hertz et al., 1999; Kirischuk et al., 2012; Marx et al., 2015; Stobart and Anderson, 2013). The astrocytic glutamine transporters LAT2 (Na + -independent) and SNAT3 (Na-dependent) are capable of mediating glutamine release (Kirischuk et al., 2015). The [Na + ]i rise that occurs as a consequence of astrocytic glutamate influx has the potential to directly stimulate the release of glu- tamine from this pool via SNAT3 transport (Kirischuk et al., 2015). Because glutamate influx by EAATs is coupled to the influx of three Na + ions (Zerangue and Kavanaugh, 1996) whereas gluta- mine efflux via SNAT3 is coupled to the efflux of only one Na + (Chaudhry et al., 1995), there is potential for 3:1 amplification in the coupling of glutamate uptake to glutamine. Glutamine released from astrocytes is subsequently transported directly into presynaptic terminals where it is converted back to glutamate by glutaminases to support further glutamatergic neurotransmission (Billups et al., 2013). Thus, the astrocytic glutamine release mechanism is therefore a central process in the synapse ability to maintain a sustained level of neurotransmission. Glutamate can be also synthe- sized de novo from glucose in astrocytes via the Krebs cycle, followed by transamination or reduc- tive amination of α-oxoglutarate (Erecińska and Silver, 1990).
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Cellular and synaptic network defects in autism

Cellular and synaptic network defects in autism

developmental delays, intellectual disability [40] and up to 45% of patients also fulfill the diagnostic criteria for ASD [41]. Hamartin and tuberin form a complex that participates in the inhibition of the mammalian target of rapamycin (mTOR) [42]. mTOR is a biochemical energy sensor and a regulator of cell growth that plays an important role in stimulating protein synthesis at the synapse [43]. In line with these roles, Ehninger and colleagues observed a basal increase in activity of the mTOR signaling-pathway in Tsc2 heterozygous mutant mice [44] • . This in turn leads to abnormal neuronal plasticity and memory defects that are rescued by treating the Tsc2 mutant mice with rapamycin—an inhibitor for mTOR activity [44] • . Additionally, post-mitotic perturbation of Tsc1 levels leads to neuronal morphology alterations, such as an increase in soma and spine size, but a decrease in dendritic spine density [45]. Interestingly, recent work from Zoghbi and colleagues has provided evidence for the existence of shared binding partners (e.g. Homer3 and Actinin) between the Tsc1/Tsc2 protein complex and Shank3, indicating an intermolecular overlap between these two ASD relevant pathways [46] •• . Furthermore, the Tsc1/Tsc2 complex also overlaps with the Fragile X mental retardation 1 (FMR1) gene network at synaptic sites. Specifically, FMR1 was shown to interact with TSC2 transcripts and other autism associated genes [47] • . Nevertheless, recent results alert to the notion that the precise molecular changes occurring from the disruption of these pathways may not be trivial to predict. Specifically, Tsc2 mutant mice display defects that oppose those caused by FMR1 mutants in regards to mGluR-dependent synaptic plasticity [48] • . Moreover, the genetic cross of both mutant mice for Tsc2+/ and Fmr1/y rescued synaptic and behavioral impairments, further corroborating an apposition in molecular roles [48] • . This could suggest that Tsc2 and FMRP proteins/transcripts may be regulated through complex feedback and compensatory mechanism, or alternatively, that Tsc2/mTOR and FMR1 prime the regulation of distinct pools of synaptic proteins necessary for mGluR-dependent synaptic plasticity.
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Abnormal AMPAR-mediated synaptic plasticity, cognitive and autistic-like behaviors in a missense Fmr1 mutant mouse model of Fragile X syndrome

Abnormal AMPAR-mediated synaptic plasticity, cognitive and autistic-like behaviors in a missense Fmr1 mutant mouse model of Fragile X syndrome

310 mosmol/l). Sagittal hippocampal slices (350 mm) were then incubated in standard artificial cerebrospinal fluid (ACSF; 119 mM NaCl, 2.5 mM KCl, 1.3 mM MgCl 2 , 2.5 mM CaCl 2 , 10 mM glucose, 1 mM NaH 2 PO 4 , 26 mM NaHCO 3 ). Slices were allowed to recover at 35°C for 45 min, continuously oxygenized with carbogen, and then for 45 min at RT. Recordings were performed in ACSF continuously oxygenized with carbogen at 33-35°C in a submerged recording chamber perfused at low rate (1.8 ml/min). Glass microelectrodes (tip diameter 5–10 µm; resistance: 0.2–0.3W) were filled with ACSF. Field recordings were performed using MultiClamp 700B amplifier (Molecular Devices, Foster City, CA) and Clampfit software. Schaffer collaterals in the CA1 region were stimulated using a bipolar electrode and recorded in the stratum radiatum of the CA1. A baseline of 10 min was recorded in the current clamp mode with a single stimulation at 0.1Hz every 10 sec. LTP was induced by high-frequency stimulation (3 x 100Hz for 1 sec, 30 sec inter burst), and recorded at 0.1 Hz stimulation rate for 50 min. Analysis was performed using the Clampfit software (Molecular Device). Along the 0.1 Hz stimulations, fiber volley (FV) and synaptic response slopes were calculated and normalized to the baseline levels. Experiments were done blind to the genotype. To assess for synaptic changes, the EPSP/FV slope ratio was calculated and averaged for 1-min time periods. Quantification and statistical comparisons were computed by comparing the EPSP/FV ratios obtained at 40-50 min after induction to the baseline level.
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en fr AMP-activated protein kinase : Screening for novel membrane substrates and creatine kinase phosphorylation linked to specific subcellular compartment La protéine kinase activée par AMP : Criblage de nouveaux substrats membranaires et phosphorylation de la créatine kinase liée à une compartimentation subcellulaire

synthesis and translocation (Mayinger and Meyer, 1993). This may involve association of phospho-BCK with a putative ER ATP-transporter, which has not yet been identified in mammals, although ATP transport across the ER membranes has been shown (Hirschberg et al., 1998). These different functional advantages of ER-associated phospho-BCK will have to be tested in future experiments. For example, the energy-dependent process of Ca 2+ removal from the cytosol that is known to be promoted by BCK can be analyzed in AMPK knockout cells. In the absence of AMPK, BCK is no longer phosphorylated which should alter its translocation to and/or function at the ER under condition of energy stress and thus its contribution to Ca 2+ homeostasis. The Ca 2+ homeostasis should then be normalized again by transfection with S6D mutant. Finally, MCK phosphorylation by AMPK reported earlier study (Ponticos et al., 1998) should be confirmed, although the reported functional consequences as strong interaction between both proteins and MCK inhibition remain disputed. We suggest that, also in this case, phosphorylation by AMPK could rather induce a specific subcellular localization. Ser6 is conservatively replaced by threonine in MCK and, for example, thr6 is close to the interaction domain that mediates MCK binding to myosine and M-protein in the myofibrillar M-band (Hornemann et al., 2003; Hornemann et al., 2000).
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CD4+ T Cells Have a Permissive Effect on Enriched Environment-Induced Hippocampus Synaptic Plasticity

CD4+ T Cells Have a Permissive Effect on Enriched Environment-Induced Hippocampus Synaptic Plasticity

Patch Clamp Technique CA1 pyramidal neurons were patch-clamped in the whole- cell configuration. This technique allowed for recording of currents from the whole surface of a single neuron in the living slice while still connected with the rest of the neuronal network. Using pipettes (2–8 M ) filled with a cesium chloride (CsCl) solution supplemented with N-(2,6- Dimethylphenylcarbamoylmethyl)triethylammonium bromide (QX314, a sodium channel blocker to block action potentials) we recorded the glutamatergic excitatory post-synaptic currents (EPSCs) which were pharmacologically isolated using the GABA A receptor antagonist bicuculline (10 µM) in the bath solution. We recorded both spontaneous (without the sodium channel inhibitor tetrodotoxin TTX) and miniature (in the presence of 2 µM TTX) EPSCs. Three-minute-long recordings were used to determine the properties of the spontaneous events. 3–16 neurons were recorded in 2–5 mice in each group. The same mice were used both for patch-clamp and LTP experiments using two different electrophysiology setups simultaneously.
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CD4 + T Cells Have a Permissive Effect on Enriched Environment-Induced Hippocampus Synaptic Plasticity

CD4 + T Cells Have a Permissive Effect on Enriched Environment-Induced Hippocampus Synaptic Plasticity

Sequencing Libraries were sequenced on a Proton Ion PI TM Chip V3 (Thermo) generating 38 M reads for the choroid plexus. Single-end reads were processed with a custom analysis pipeline. The first step was removing the 3p adaptor “CTGTCTCTTATACACATCT” and the front adaptor sequence “AAGTCGCAGGGTTG” using cutadapt (version 1.2.1). We required, immediately after the front adaptor sequence, an 8-base pattern in accordance with the UMI design N4H4 (N = ATCG, H = ATC) followed by a stretch of “GGG”. Reads without those specifications were discarded from further analyses to avoid artifactual new molecule production due to creation of pseudo UMI sequences related to sequencing errors, especially indels that are frequent in Ion Torrent reads. Reads with a template sequence length under 50 bases were also discarded. This filtration process removed 32% and 34% of the total amount of reads. Mapping of the cDNA sequences was then done with STAR_2.4.0a versus mm10 mouse genome build using RNA-seq Encode recommendations. For molecule counting based on UMI counts, we used the Dropseq Core Computational Protocol version 1.0.1 (dropseq.jar) from McCarrol ( Macosko et al., 2015 ) using GTF gene model from Ensembl release GRCm38.83. The Digital Expression function of dropseq.jar was used with default parameters (edit distance = 1) to produce a matrix of molecule counts that were used in the subsequent statistical analysis.
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Area-specific alterations of synaptic plasticity in the 5XFAD mouse model of Alzheimer's disease: dissociation between somatosensory cortex and hippocampus

Area-specific alterations of synaptic plasticity in the 5XFAD mouse model of Alzheimer's disease: dissociation between somatosensory cortex and hippocampus

Drugs were directly applied in this superfusion. MEA was positioned on the platform of a Leica inverted microscope equipped with a CCD camera (CoolSnap, Roper Scientific, France). Images of the cortico-hippocampal slice on the MEA were captured in order to accurately map the synaptic signals recorded in the different areas of the brain slice. MEAs comprised 60 extracellular electrodes [24]. The inter-electrode distance was 200 µm. Each individual electrode from the array could be used either as a recording or as a stimulatory electrode. A nylon mesh was positioned above the slice to obtain a satisfactory electrical contact between the surface of the slice and the electrode array. Double stimulation was achieved with an external stimulator (STG-1004; Multi Channel Systems) by applying biphasic current pulses simultaneously to two electrodes of the array, one located in the Schaffer Collateral pathway of the hippocampus and the other one in the cortex. Stimulation intensity (60 to 300 µA) and duration (70 to 200 µs) were adapted to avoid multiphasic responses due to an excessive stimulation [25]. Field excitatory postsynaptic potentials (fEPSPs) and population spikes (pop spikes) could then be recorded by all the remaining electrodes of the array at the same time. Signals were recorded and analyzed (MC Rack; Multi Channel Systems). We verified that stimulating cortical afferents did not evoke any signal in the stratum radiatum of the CA1 area of the hippocampus and conversely that stimulating Schaffer collaterals pathway did not induce any signal in the cortical area recorded. In fact, both hippocampal and/or cortical stimulation could evoke some signals in the Alveus. Thus these signals were not taken into consideration for further analysis. Baseline synaptic signals were evoked using a 0.066 Hz frequency. Slices displaying epileptic-like activity were discarded. Short term plasticity was elicited by two stimulations with an interpulse duration varying from 25 to 500ms. Long-term potentiation (LTP) was induced using one or three repeated theta-burst stimulation (15 trains of 4 pulses at 100 Hz every 200 ms) with a 30 s interval when repeated. Some recordings were carried out in presence of 25 µM picrotoxin, a GABA A receptor blocker, in the perfusate. The magnitude of the effects on synaptic transmission was determined by measuring slopes of fEPSPs, which were modified in a similar way to fEPSP amplitudes, as reported by
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Synaptic and non-synaptic communication between neurons and oligodendrocyte precursor cells in the somatosensory cortex

Synaptic and non-synaptic communication between neurons and oligodendrocyte precursor cells in the somatosensory cortex

The identification of the channel mediating this inward current was achieved in 1995, with the report of a novel ATP-dependent inward rectifier potassium channel predominantly expressed [r]

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Lipids and synaptic functions

Lipids and synaptic functions

Lipids and synaptic functions Fanny Mochel 1,2,3 Abstract Synaptic functions have long been thought to be driven by proteins, especially the SNARE complex, contrasting with a relatively passive role for lipids constituting cell membranes. It is now clear that not only lipids, i.e. glycerophospholipids, sphingolipids and sterols, play a determinant role in the dynamics of synaptic membranes but they also actively contribute to the endocytosis and exocytosis of synaptic vesicles in conjunction with synaptic proteins. On the other hand, a growing number of inborn errors of metabolism affecting the nervous system have been related to defects in the synthesis and remodelling of fatty acids, phospholipids and sphingolipids. Alterations of the metabolism of these lipids would be expected to affect the dynamics of synaptic membranes and synaptic vesicles. Still, only few examples are currently documented. It remains to be determined to which extent the pathophysiology of disorders of complex lipids biosynthesis and remodelling share common pathogenic mechanisms with the more traditional synaptopathies.
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Myotonic dystrophy CTG expansion affects synaptic vesicle proteins, neurotransmission and mouse behaviour.: Synaptic dysfunction in myotonic dystrophy

Myotonic dystrophy CTG expansion affects synaptic vesicle proteins, neurotransmission and mouse behaviour.: Synaptic dysfunction in myotonic dystrophy

Electrophysiological profiling. Input/output (I/O) properties, Paired-Pulse Facilitation (PPF), Long Term Depression (LTD) and Long Term Potentiation (LTP) were assessed on male DMSXL homozygotes and wild-type controls, aged seven months (I/O, PPF and LTD) or four months (LTP). Mice were sacrificed by fast decapitation, without previous anesthesia. Brains were processed in oxygenated buffer and artificial cerebro-spinal fluid as previously described (Steidl et al., 2006). Extracellular field excitatory post-synaptic potentials (fEPSP) were measured with Multi-Electrode Arrays (MEA) technology (100 µm distant electrodes) on 350 µm thick hippocampal slices. One of the electrodes stimulated Schaeffer collaterals at the CA3/CA1 interface. The stimulus, consisting of a monopolar biphasic current pulse (negative for 60 µs and then positive for 60 µs), evoked responses (field potentials: fEPSP) in the CA1 region. I/O
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en fr Roles of astroglial cannabinoid type 1 receptors (CB1) in memory and synaptic plasticity Rôles du récepteur aux cannabinoïdes de type 1 des astrocytes dans la mémoire et la plasticité synaptique

coordinates: 1) CA1 stratum radiatum: A/P 1.5 mm, M/L 1.0 mm, DV 1.20 mm; CA3: A/P 2.5 mm, M/L 2.8, D/V 2.0 mm. The recording electrode (tip diameter = 1–2 mm, 4–6 MU) was filled with a 2% pontamine sky blue solution in 0.5M sodium acetate. At first the recording electrode was placed by hand until it reached the surface of the brain and then to the final depth using an automatic micropositioner (MIM100-2, M2E, France). The stimulation electrode was placed in the correct area using a micromanipulator (UNI-Z, M2E, France). Both electrodes were adjusted to find the area with maximum response. In vivo recordings of evoked field excitatory postsynaptic potentials (fEPSPs) were amplified 10 times by Axoclamp 900A amplifier (Molecular Devices, CA, USA) before being further amplified 100 times and filtered (low pass at 1 Hz and high-pass at 5000Hz) via a differential AC amplifier (model 1700; A-M Systems, Sequim, WA, USA). fEPSPs were digitized and collected on-line using a laboratory interface and software (CED 1401, SPIKE 2; Cambridge Electronic Design, UK). Test pulses were generated through an Isolated Constant Current Stimulator (DS3, Digitimer, UK) triggered by the SPIKE 2 output sequencer via CED 1401 and collected every 2 s at a 10 kHz sampling frequency and then averaged every 300 s. Test pulse intensities were typically between 50-250 mA with a duration of 500 ms. Basal stimulation intensity was adjusted to 30%–40% of the current intensity that evoked a maximum field response. All responses were expressed as percent from the average responses recorded during the 10 min before high-frequency stimulation (HFS). HFS was induced by applying 3 trains of 100 Hz (1 s each), separated by 20 s interval. fEPSP were then recorded for a period of 40 min. In the specific group of mice the following treatments were applied: 1) MK-801 (Abcam, United Kingdom; 3 mg/kg, i.p., dissolved in saline, approx. 60 min before HFS) or vehicle (saline, i.p., approx. 60 min before HFS) 2) D-serine (Ascent Scientific, United Kingdom; 50 mg/kg, i.p., dissolved in saline) approx. 2 hr before HFS or vehicle (saline, i.p.). At the end of each experiment, the positions of the electrodes were marked by iontophoretic infusion of the recording solution during 180 s at 20 mA and continuous current discharge over 20 s at +20 mA for recording and stimulation areas, respectively. Histological verification was performed ex vivo.
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HISTOCHEMISTRY AND ULTRASTRUCTURE OF THE CRYPT CELLS IN THE DIGESTIVE GLAND OF APLYSIA PUNCTATA (CUVIER, 1803)

HISTOCHEMISTRY AND ULTRASTRUCTURE OF THE CRYPT CELLS IN THE DIGESTIVE GLAND OF APLYSIA PUNCTATA (CUVIER, 1803)

1968; Schmekel & Wechsler, 1968a,b; Griebel, 1993; Kress et al, 1994) and many prosobranchs (Mason & Nott, 1981) are known to accumu- late inorganic salts under normal conditions. This process of bioaccumulation of mineral salts occurs in specialized cells of the digestive tubules, called crypt cells (calcium cells) which have different ultrastructural characteristics and functions in different molluscan species. To date, there is no available ultrastructural information for the sea hare Aplysia punctata from the Mediterranean. In this classic osmo- adjusting species (Nicol, 1967), calcium appears as a major factor in its biology, for the nervous system, toxic secretions released from purple and opaline glands against predators, muscles and eggs. If the mineral salt store hypothesis is true, it can be predicted that the digestive gland of A. punctata, would contain inorganic salts. This prediction has been tested by using histochemical methods for calcium and iron. The goal of this study is to analyse and identify the crypt cells and to provide preliminary information on their relationships. The morphology and functions of these cells are investigated in this ultrastructural analysis.
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