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Sample records for glutamate synaptic transmission

  1. Peripherally restricted viral challenge elevates extracellular glutamate and enhances synaptic transmission in the hippocampus.

    PubMed

    Hunsberger, Holly C; Wang, Desheng; Petrisko, Tiffany J; Alhowail, Ahmad; Setti, Sharay E; Suppiramaniam, Vishnu; Konat, Gregory W; Reed, Miranda N

    2016-07-01

    Peripheral infections increase the propensity and severity of seizures in susceptible populations. We have previously shown that intraperitoneal injection of a viral mimic, polyinosinic-polycytidylic acid (PIC), elicits hypersusceptibility of mice to kainic acid (KA)-induced seizures. This study was undertaken to determine whether this seizure hypersusceptibility entails alterations in glutamate signaling. Female C57BL/6 mice were intraperitoneally injected with PIC, and after 24 h, glutamate homeostasis in the hippocampus was monitored using the enzyme-based microelectrode arrays. PIC challenge robustly increased the level of resting extracellular glutamate. While pre-synaptic potassium-evoked glutamate release was not affected, glutamate uptake was profoundly impaired and non-vesicular glutamate release was augmented, indicating functional alterations of astrocytes. Electrophysiological examination of hippocampal slices from PIC-challenged mice revealed a several fold increase in the basal synaptic transmission as compared to control slices. PIC challenge also increased the probability of pre-synaptic glutamate release as seen from a reduction of paired-pulse facilitation and synaptic plasticity as seen from an enhancement of long-term potentiation. Altogether, our results implicate a dysregulation of astrocytic glutamate metabolism and an alteration of excitatory synaptic transmission as the underlying mechanism for the development of hippocampal hyperexcitability, and consequently seizure hypersusceptibility following peripheral PIC challenge. Peripheral infections/inflammations enhance seizure susceptibility. Here, we explored the effect of peritoneal inflammation induced by a viral mimic on glutamate homeostasis and glutamatergic neurotransmission in the mouse hippocampus. We found that peritoneal inflammation elevated extracellular glutamate concentration and enhanced the probability of pre-synaptic glutamate release resulting in hyperexcitability of

  2. A computational model to investigate astrocytic glutamate uptake influence on synaptic transmission and neuronal spiking.

    PubMed

    Allam, Sushmita L; Ghaderi, Viviane S; Bouteiller, Jean-Marie C; Legendre, Arnaud; Ambert, Nicolas; Greget, Renaud; Bischoff, Serge; Baudry, Michel; Berger, Theodore W

    2012-01-01

    Over the past decades, our view of astrocytes has switched from passive support cells to active processing elements in the brain. The current view is that astrocytes shape neuronal communication and also play an important role in many neurodegenerative diseases. Despite the growing awareness of the importance of astrocytes, the exact mechanisms underlying neuron-astrocyte communication and the physiological consequences of astrocytic-neuronal interactions remain largely unclear. In this work, we define a modeling framework that will permit to address unanswered questions regarding the role of astrocytes. Our computational model of a detailed glutamatergic synapse facilitates the analysis of neural system responses to various stimuli and conditions that are otherwise difficult to obtain experimentally, in particular the readouts at the sub-cellular level. In this paper, we extend a detailed glutamatergic synaptic model, to include astrocytic glutamate transporters. We demonstrate how these glial transporters, responsible for the majority of glutamate uptake, modulate synaptic transmission mediated by ionotropic AMPA and NMDA receptors at glutamatergic synapses. Furthermore, we investigate how these local signaling effects at the synaptic level are translated into varying spatio-temporal patterns of neuron firing. Paired pulse stimulation results reveal that the effect of astrocytic glutamate uptake is more apparent when the input inter-spike interval is sufficiently long to allow the receptors to recover from desensitization. These results suggest an important functional role of astrocytes in spike timing dependent processes and demand further investigation of the molecular basis of certain neurological diseases specifically related to alterations in astrocytic glutamate uptake, such as epilepsy. PMID:23060782

  3. Increased Gene Dosage of Ube3a Results in Autism Traits and Decreased Glutamate Synaptic Transmission in Mice

    PubMed Central

    Smith, Stephen E. P.; Zhou, Yu-Dong; Zhang, Guangping; Jin, Zhe; Stoppel, David C.; Anderson, Matthew P.

    2012-01-01

    People with autism spectrum disorder are characterized by impaired social interaction, reduced communication, and increased repetitive behaviors. The disorder has a substantial genetic component, and recent studies have revealed frequent genome copy number variations (CNVs) in some individuals. A common CNV that occurs in 1 to 3% of those with autism—maternal 15q11-13 duplication (dup15) and triplication (isodicentric extranumerary chromosome, idic15)—affects several genes that have been suggested to underlie autism behavioral traits. To test this, we tripled the dosage of one of these genes, the ubiquitin protein ligase Ube3a, which is expressed solely from the maternal allele in mature neurons, and reconstituted the three core autism traits in mice: defective social interaction, impaired communication, and increased repetitive stereotypic behavior. The penetrance of these autism traits depended on Ube3a gene copy number. In animals with increased Ube3a gene dosage, glutamatergic, but not GABAergic, synaptic transmission was suppressed as a result of reduced presynaptic release probability, synaptic glutamate concentration, and postsynaptic action potential coupling. These results suggest that Ube3a gene dosage may contribute to the autism traits of individuals with maternal 15q11-13 duplication and support the idea that increased E3A ubiquitin ligase gene dosage results in reduced excitatory synaptic transmission. PMID:21974935

  4. Presynaptic group I metabotropic glutamate receptors modulate synaptic transmission in the rat superior colliculus via 4-AP sensitive K+ channels

    PubMed Central

    White, Anne-Marie; Kylänpää, Risto A; Christie, Louisa A; McIntosh, Simon J; Irving, Andrew J; Platt, Bettina

    2003-01-01

    Group I metabotropic glutamate receptors (mGluRs) are thought to be important modulators of neuronal function in the superior colliculus (SC). Here, we investigated the pharmacology and signalling mechanisms underlying group I mGluR-mediated inhibition of neuronal excitability and synaptic transmission in the rat SC slice. The group I agonist (RS)-3,5-dihydroxyphenylglycine (DHPG) potently depressed synaptically evoked excitatory postsynaptic potentials (EPSPs), currents (EPSCs), and action potentials in a dose-dependent manner (IC50: 6.3 μM). This was strongly reduced by the broad-spectrum antagonist (+)-alpha-methyl-4-carboxyphenylglycine (MCPG, 1 mM, ∼95% reduction), by the mGluR1 antagonist LY367385 (100 μM, ∼80% reduction) but not by the mGluR5 antagonist 6-methyl-2-(phenylethynyl)-pyridine (MPEP, 1–100 μM). The putative mGluR5-specific agonist (RS)-2-chloro-5-hydroxyphenylglycine (CHPG, 500 μM) also inhibited EPSPs. Interestingly, CHPG's actions were not blocked by MPEP, but LY367385 (100 μM) reduced the effect of CHPG by 50%. Inhibition induced by DHPG was independent of phospholipase C (PLC)/protein kinase C pathways, and did not require intact intracellular Ca2+ stores. It was not abolished but enhanced by the GABAA antagonist bicuculline (5 μM), suggesting that DHPG's action was not due to facilitated inhibition or changes in neuronal network activity. The K+ channel antagonist 4-aminopyridine (4-AP, 50–100 μM) converted the inhibitory effect of DHPG into facilitation. Paired-pulse depression was strongly reduced by DHPG, an effect that was also prevented by 4-AP. Our data indicate that group I agonists regulate transmitter release, presumably via an autoreceptor in the SC. This receptor may be involved in adaptation to repetitive stimulation via a non-PLC mediated pathway. PMID:14623765

  5. Regulation of synaptic transmission in the mossy fibre-granule cell pathway of rat cerebellum by metabotropic glutamate receptors.

    PubMed

    Vetter, P; Garthwaite, J; Batchelor, A M

    1999-06-01

    The role of metabotropic glutamate receptors (mGluRs) in the mossy fibre-granule cell pathway in rat cerebellum was studied using slice preparations and electrophysiological techniques. Application of the group I selective agonist (S)-3,5-dihydroxyphenylglycine (DHPG) evoked, in a concentration-dependent manner (EC50 = 33 microM), a depolarising/hyperpolarising complex response from granule cells which was preferentially inhibited by the group I selective antagonist (S)-4-carboxyphenylglycine (4CPG). The group III selective agonist L-amino-4-phosphonobutyrate (AP4) evoked a hyperpolarising response (EC50 = 10 microM) which was inhibited by the group II/III selective antagonist (S)-alpha-methyl-4-phosphonophenylglycine (MPPG). The group II agonist (2S,2'R,3'R)-2-(2',3'-dicarboxylcyclopropyl)glycine (DCG-IV) elicited no measurable voltage change. The amplitude of the synaptically-mediated mossy fibre response in granule cells was unaffected during application of AP4, was reduced by DHPG and was enhanced by DCG-IV (EC50 = 80 nM). These effects were inhibited by the group selective antagonists 4CPG and (2S,1'S,2'S,3'R)-2-(2'-carboxy-3'-phenylcyclopropyl)glycine (PCCG-4), respectively. Further investigation using patch-clamp recording revealed that DCG-IV potently inhibited spontaneous GABAergic currents. We conclude that group I and III (but not group II) mGluRs are functionally expressed by granule cells, whereas unexpectedly group II or III mGluRs do not appear to be present presynaptically on mossy fibre terminals. Group II mGluRs are located on Golgi cell terminals; when activated these receptors cause disinhibition, a function which may be important for gating information transfer from the mossy fibres to the granule cells. PMID:10465684

  6. Activation of Phosphatidylinositol-Linked Dopamine Receptors Induces a Facilitation of Glutamate-Mediated Synaptic Transmission in the Lateral Entorhinal Cortex

    PubMed Central

    Glovaci, Iulia; Chapman, C. Andrew

    2015-01-01

    The lateral entorhinal cortex receives strong inputs from midbrain dopamine neurons that can modulate its sensory and mnemonic function. We have previously demonstrated that 1 µM dopamine facilitates synaptic transmission in layer II entorhinal cortex cells via activation of D1-like receptors, increased cAMP-PKA activity, and a resulting enhancement of AMPA-receptor mediated currents. The present study assessed the contribution of phosphatidylinositol (PI)-linked D1 receptors to the dopaminergic facilitation of transmission in layer II of the rat entorhinal cortex, and the involvement of phospholipase C activity and release of calcium from internal stores. Whole-cell patch-clamp recordings of glutamate-mediated evoked excitatory postsynaptic currents were obtained from pyramidal and fan cells. Activation of D1-like receptors using SKF38393, SKF83959, or 1 µM dopamine induced a reversible facilitation of EPSCs which was abolished by loading cells with either the phospholipase C inhibitor U-73122 or the Ca2+ chelator BAPTA. Neither the L-type voltage-gated Ca2+ channel blocker nifedipine, nor the L/N-type channel blocker cilnidipine, blocked the facilitation of synaptic currents. However, the facilitation was blocked by blocking Ca2+ release from internal stores via inositol 1,4,5-trisphosphate (InsP3) receptors or ryanodine receptors. Follow-up studies demonstrated that inhibiting CaMKII activity with KN-93 failed to block the facilitation, but that application of the protein kinase C inhibitor PKC(19-36) completely blocked the dopamine-induced facilitation. Overall, in addition to our previous report indicating a role for the cAMP-PKA pathway in dopamine-induced facilitation of synaptic transmission, we demonstrate here that the dopaminergic facilitation of synaptic responses in layer II entorhinal neurons also relies on a signaling cascade dependent on PI-linked D1 receptors, PLC, release of Ca2+ from internal stores, and PKC activation which is likely dependent

  7. Functional analysis of glutamate transporters in excitatory synaptic transmission of GLAST1 and GLAST1/EAAC1 deficient mice.

    PubMed

    Stoffel, Wilhelm; Körner, Rafael; Wachtmann, Dagmar; Keller, Bernhard U

    2004-09-28

    The high affinity, Na(+)-dependent, electrogenic glial L-glutamate transporters GLAST1 and GLT1, and two neuronal EAAC1 and EAAT4, regulate the neurotransmitter concentration in excitatory synapses of the central nervous system. We dissected the function of the individual transporters in the monogenic null allelic mouse lines, glast1(-/-) and eaac1(-/-), and the derived double mutant glast(-/-)eaac1(-/-). Unexpectedly, the biochemical analysis and the behavioral phenotypes of these null allelic mouse lines were inconspicuous. Inhibition studies of the Na(+)-dependent glutamate transport by plasma membrane vesicles and by isolated astrocytes of wt and glast1(-/-) mouse brains indicated the pivotal compensatory role of GLT1 in the absence particularly of GLAST1 and GLAST1 and EAAC1 mutant mice. In electrophysiological studies, the decay rate of excitatory postsynaptic currents (EPSCs) of Purkinje cells (PC) after selective activation of parallel and climbing fibers proved to be similar in wt and eaac1(-/-), but was significantly prolonged in glast1(-/-) PCs. Bath application of the glutamate uptake blocker SYM2081 prolonged EPSC decay profiles in both wt and double mutant glast1(-/-)eaac1(-/-) PCs by 286% and 229%, respectively, indicating a prominent role of compensatory glutamate transport in shaping glast1(-/-)eaac1(-/-) EPSCs. PMID:15363892

  8. Metabotropic glutamate receptors modulate synaptic transmission in the perforant path: pharmacology and localization of two distinct receptors.

    PubMed

    Dietrich, D; Beck, H; Kral, T; Clusmann, H; Elger, C E; Schramm, J

    1997-09-01

    Metabotropic glutamate receptors (mGluRs) have emerged as an interesting family of eight different receptor subtypes that can be divided into three groups according to their pharmacology and sequence similarity. In the present study, the specific mGluR agonists (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid ((1S,3R)-ACPD) and L(+)-2-amino-4-phosphonobutyric acid (L-AP4) depressed field excitatory postsynaptic potentials (fEPSPs) in the rat dentate gyrus evoked by perforant path stimulation in a concentration-dependent, rapid and reversible manner (EC50: L-AP4 5.9 +/- 1.6 microM, (1S,3R)-ACPD 80 +/- 34 microM). In a 'paired-pulse' stimulation protocol, the first fEPSP showed a stronger reduction, resulting in 'paired-pulse' facilitation. The effects of L-AP4 but not of (1S,3R)-ACPD could be antagonized by the group III mGluR antagonists (S)-2-amino-2-methyl-4-phosphonobutanoic acid (MAP4) and (RS)-alpha-methyl-4-phosphonophenylglycine (MPPG). Moreover, (1S,3R)-ACPD was still potently depressing fEPSPs after preperfusion of near saturating concentrations of L-AP4. Together, the results suggest that both substances act on different mGluRs. The effects of (1S,3R)-ACPD could not be further differentiated by selective group I or group II mGluR agonists. Although (2S,1'S,2'S)-2-carboxycyclopropylglycine (L-CCG-I) blocked fEPSPs at concentrations > 1 microM, these effects, as well as L-AP4 effects, were potently antagonized by MAP4. This suggests that mGluR8 might be responsible for the actions of L-AP4 and L-CCG-I. The two different mGluRs showed a distinct distribution when fEPSPs were recorded simultaneously in the outer and middle molecular layer (OML/MML): The L-AP4 sensitive receptor, possibly mGluR8, seems to be located in the OML while (1S,3R)-ACPD showed its main effect in the MML. PMID:9367251

  9. Synaptic Glutamate Spillover Due to Impaired Glutamate Uptake Mediates Heroin Relapse

    PubMed Central

    Scofield, Michael D.; Boger, Heather; Hensley, Megan; Kalivas, Peter W.

    2014-01-01

    Reducing the enduring vulnerability to relapse is a therapeutic goal in treating drug addiction. Studies with animal models of drug addiction show a marked increase in extrasynaptic glutamate in the core subcompartment of the nucleus accumbens (NAcore) during reinstated drug seeking. However, the synaptic mechanisms linking drug-induced changes in extrasynaptic glutamate to relapse are poorly understood. Here, we discovered impaired glutamate elimination in rats extinguished from heroin self-administration that leads to spillover of synaptically released glutamate into the nonsynaptic extracellular space in NAcore and investigated whether restoration of glutamate transport prevented reinstated heroin seeking. Through multiple functional assays of glutamate uptake and analyzing NMDA receptor-mediated currents, we show that heroin self-administration produced long-lasting downregulation of glutamate uptake and surface expression of the transporter GLT-1. This downregulation was associated with spillover of synaptic glutamate to extrasynaptic NMDA receptors within the NAcore. Ceftriaxone restored glutamate uptake and prevented synaptic glutamate spillover and cue-induced heroin seeking. Ceftriaxone-induced inhibition of reinstated heroin seeking was blocked by morpholino-antisense targeting GLT-1 synthesis. These data reveal that the synaptic glutamate spillover in the NAcore results from reduced glutamate transport and is a critical pathophysiological mechanism underling reinstated drug seeking in rats extinguished from heroin self-administration. PMID:24741055

  10. SYNAPTIC VESICLE PROTEIN TRAFFICKING AT THE GLUTAMATE SYNAPSE

    PubMed Central

    Santos, Magda S.; Li, Haiyan; Voglmaier, Susan M.

    2009-01-01

    Expression of the integral and associated proteins of synaptic vesicles is subject to regulation over time, by region, and in response to activity. The process by which changes in protein levels and isoforms result in different properties of neurotransmitter release involves protein trafficking to the synaptic vesicle. How newly synthesized proteins are incorporated into synaptic vesicles at the presynaptic bouton is poorly understood. During synaptogenesis, synaptic vesicle proteins sort through the secretory pathway and are transported down the axon in precursor vesicles that undergo maturation to form synaptic vesicles. Changes in protein content of synaptic vesicles could involve the formation of new vesicles that either mix with the previous complement of vesicles or replace them, presumably by their degradation or inactivation. Alternatively, new proteins could individually incorporate into existing synaptic vesicles, changing their functional properties. Glutamatergic vesicles likely express many of the same integral membrane proteins and share certain common mechanisms of biogenesis, recycling, and degradation with other synaptic vesicles. However, glutamatergic vesicles are defined by their ability to package glutamate for release, a property conferred by the expression of a vesicular glutamate transporter (VGLUT). VGLUTs are subject to regional, developmental, and activity-dependent changes in expression. In addition, VGLUT isoforms differ in their trafficking, which may target them to different pathways during biogenesis or after recycling, which may in turn sort them to different vesicle pools. Emerging data indicate that differences in the association of VGLUTs and other synaptic vesicle proteins with endocytic adaptors may influence their trafficking. These observations indicate that independent regulation of synaptic vesicle protein trafficking has the potential to influence synaptic vesicle protein composition, the maintenance of synaptic vesicle

  11. Mapping Auditory Synaptic Circuits with Photostimulation of Caged Glutamate.

    PubMed

    Sturm, Joshua J; Nguyen, Tuan; Kandler, Karl

    2016-01-01

    Photostimulation of neurons with caged glutamate is a viable tool for mapping the strength and spatial distribution of synaptic networks in living brain slices. In photostimulation experiments, synaptic connectivity is assessed by eliciting action potentials in putative presynaptic neurons via focal photolysis of caged glutamate, while measuring postsynaptic responses via intracellular recordings. Two approaches are commonly used for delivering light to small, defined areas in the slice preparation; an optical fiber-based method and a laser-scanning-based method. In this chapter, we outline the technical bases for using photostimulation of caged glutamate to map synaptic circuits, and discuss the advantages and disadvantages of using fiber-based vs. laser-based systems. PMID:27259947

  12. Synaptic adhesion molecule IgSF11 regulates synaptic transmission and plasticity

    PubMed Central

    Shin, Hyewon; van Riesen, Christoph; Whitcomb, Daniel; Warburton, Julia M.; Jo, Jihoon; Kim, Doyoun; Kim, Sun Gyun; Um, Seung Min; Kwon, Seok-kyu; Kim, Myoung-Hwan; Roh, Junyeop Daniel; Woo, Jooyeon; Jun, Heejung; Lee, Dongmin; Mah, Won; Kim, Hyun; Kaang, Bong-Kiun; Cho, Kwangwook; Rhee, Jeong-Seop; Choquet, Daniel; Kim, Eunjoon

    2016-01-01

    Summary Synaptic adhesion molecules regulate synapse development and plasticity through mechanisms including trans-synaptic adhesion and recruitment of diverse synaptic proteins. We report here that the immunoglobulin superfamily member 11 (IgSF11), a homophilic adhesion molecule preferentially expressed in the brain, is a novel and dual-binding partner of the postsynaptic scaffolding protein PSD-95 and AMPAR glutamate receptors (AMPARs). IgSF11 requires PSD-95 binding for its excitatory synaptic localization. In addition, IgSF11 stabilizes synaptic AMPARs, as shown by IgSF11 knockdown-induced suppression of AMPAR-mediated synaptic transmission and increased surface mobility of AMPARs, measured by high-throughput, single-molecule tracking. IgSF11 deletion in mice leads to suppression of AMPAR-mediated synaptic transmission in the dentate gyrus and long-term potentiation in the CA1 region of the hippocampus. IgSF11 does not regulate the functional characteristics of AMPARs, including desensitization, deactivation, or recovery. These results suggest that IgSF11 regulates excitatory synaptic transmission and plasticity through its tripartite interactions with PSD-95 and AMPARs. PMID:26595655

  13. Synaptic Transmission Correlates of General Mental Ability

    ERIC Educational Resources Information Center

    McRorie, Margaret; Cooper, Colin

    2004-01-01

    Nerve conduction velocity (NCV) and efficiency of synaptic transmission are two possible biological mechanisms that may underpin intelligence. Direct assessments of NCV, without synaptic transmission, show few substantial or reliable correlations with cognitive abilities ["Intelligence" 16 (1992) 273]. We therefore assessed the latencies of…

  14. Optical measurement of synaptic glutamate spillover and reuptake by linker optimized glutamate-sensitive fluorescent reporters

    PubMed Central

    Hires, Samuel Andrew; Zhu, Yongling; Tsien, Roger Y.

    2008-01-01

    Genetically encoded sensors of glutamate concentration are based on FRET between cyan and yellow fluorescent proteins bracketing a bacterial glutamate-binding protein. Such sensors have yet to find quantitative applications in neurons, because of poor response amplitude in physiological buffers or when expressed on the neuronal cell surface. We have improved our glutamate-sensing fluorescent reporter (GluSnFR) by systematic optimization of linker sequences and glutamate affinities. Using SuperGluSnFR, which exhibits a 6.2-fold increase in response magnitude over the original GluSnFR, we demonstrate quantitative optical measurements of the time course of synaptic glutamate release, spillover, and reuptake in cultured hippocampal neurons with centisecond temporal and spine-sized spatial resolution. During burst firing, functionally significant spillover persists for hundreds of milliseconds. These glutamate levels appear sufficient to prime NMDA receptors, potentially affecting dendritic spike initiation and computation. Stimulation frequency-dependent modulation of spillover suggests a mechanism for nonsynaptic neuronal communication. PMID:18332427

  15. Ionotropic glutamate receptor GluA4 and T-type calcium channel Cav 3.1 subunits control key aspects of synaptic transmission at the mouse L5B-POm giant synapse.

    PubMed

    Seol, Min; Kuner, Thomas

    2015-12-01

    The properties and molecular determinants of synaptic transmission at giant synapses connecting layer 5B (L5B) neurons of the somatosensory cortex (S1) with relay neurons of the posteriomedial nucleus (POm) of the thalamus have not been investigated in mice. We addressed this by using direct electrical stimulation of fluorescently labelled single corticothalamic terminals combined with molecular perturbations and whole-cell recordings from POm relay neurons. Consistent with their function as drivers, we found large-amplitude excitatory postsynaptic currents (EPSCs) and multiple postsynaptic action potentials triggered by a single presynaptic action potential. To study the molecular basis of these two features, ionotropic glutamate receptors and low voltage-gated T-type calcium channels were probed by virus-mediated genetic perturbation. Loss of GluA4 almost abolished the EPSC amplitude, strongly delaying the onset of action potential generation, but maintaining the number of action potentials generated per presynaptic action potential. In contrast, knockdown of the Cav 3.1 subunit abrogated the driver function of the synapse at a typical resting membrane potential of -70 mV. However, when depolarizing the membrane potential to -60 mV, the synapse relayed single action potentials. Hence, GluA4 subunits are required to produce an EPSC sufficiently large to trigger postsynaptic action potentials within a defined time window after the presynaptic action potential, while Cav 3.1 expression is essential to establish the driver function of L5B-POm synapses at hyperpolarized membrane potentials. PMID:26390982

  16. Cytosolic tail sequences and subunit interactions are critical for synaptic localization of glutamate receptors.

    PubMed

    Chang, Howard Chia-Hao; Rongo, Christopher

    2005-05-01

    AMPA-type glutamate receptors mediate excitatory synaptic transmission in the nervous system. The receptor subunit composition and subcellular localization play an important role in regulating synaptic strength. GLR-1 and GLR-2 are the Caenorhabditis elegans subunits most closely related to the mammalian AMPA-type receptors. These subunits are expressed in overlapping sets of interneurons, and contain type-I PDZ binding motifs in their carboxy-terminal cytosolic tail sequences. We report that GLR-1 and GLR-2 may form a heteromeric complex, the localization of which depends on either GLR-1 or GLR-2 tail sequences. Subunit interactions alone can mediate synaptic localization as endogenous GLR-1, or GLR-2 subunits can rescue the localization defects of subunits lacking tail sequences. Moreover, GLR-2 cytosolic tail sequences are sufficient to confer synaptic localization on a heterologous reporter containing a single-transmembrane domain. The localization of this GLR-2 reporter requires both a PDZ-binding motif in the GLR-2 tail sequence, and sequences outside of this motif. The PDZ protein LIN-10 regulates the localization of the reporter through the sequences outside of the PDZ-binding motif. Our results suggest that multiple synaptic localization signals reside in the cytosolic tail sequence of the receptor subunits, and that channel assembly can rescue the synaptic localization defects of individual mutant subunits as long as there are also wild-type subunits in the receptor complex. PMID:15840655

  17. Astroglial Metabolic Networks Sustain Hippocampal Synaptic Transmission

    NASA Astrophysics Data System (ADS)

    Rouach, Nathalie; Koulakoff, Annette; Abudara, Veronica; Willecke, Klaus; Giaume, Christian

    2008-12-01

    Astrocytes provide metabolic substrates to neurons in an activity-dependent manner. However, the molecular mechanisms involved in this function, as well as its role in synaptic transmission, remain unclear. Here, we show that the gap-junction subunit proteins connexin 43 and 30 allow intercellular trafficking of glucose and its metabolites through astroglial networks. This trafficking is regulated by glutamatergic synaptic activity mediated by AMPA receptors. In the absence of extracellular glucose, the delivery of glucose or lactate to astrocytes sustains glutamatergic synaptic transmission and epileptiform activity only when they are connected by gap junctions. These results indicate that astroglial gap junctions provide an activity-dependent intercellular pathway for the delivery of energetic metabolites from blood vessels to distal neurons.

  18. Vesicular glutamate transporter 1 orchestrates recruitment of other synaptic vesicle cargo proteins during synaptic vesicle recycling.

    PubMed

    Pan, Ping-Yue; Marrs, Julia; Ryan, Timothy A

    2015-09-11

    A long standing question in synaptic physiology is how neurotransmitter-filled vesicles are rebuilt after exocytosis. Among the first steps in this process is the endocytic retrieval of the transmembrane proteins that are enriched in synaptic vesicles (SVs). At least six types of transmembrane proteins must be recovered, but the rules for how this multiple cargo selection is accomplished are poorly understood. Among these SV cargos is the vesicular glutamate transporter (vGlut). We show here that vGlut1 has a strong influence on the kinetics of retrieval of half of the known SV cargos and that specifically impairing the endocytosis of vGlut1 in turn slows down other SV cargos, demonstrating that cargo retrieval is a collective cargo-driven process. Finally, we demonstrate that different cargos can be retrieved in the same synapse with different kinetics, suggesting that additional post-endocytic sorting steps likely occur in the nerve terminal. PMID:26224632

  19. Lateral regulation of synaptic transmission by astrocytes.

    PubMed

    Covelo, A; Araque, A

    2016-05-26

    Fifteen years ago the concept of the "tripartite synapse" was proposed to conceptualize the functional view that astrocytes are integral elements of synapses. The signaling exchange between astrocytes and neurons within the tripartite synapse results in the synaptic regulation of synaptic transmission and plasticity through an autocrine form of communication. However, recent evidence indicates that the astrocyte synaptic regulation is not restricted to the active tripartite synapse but can be manifested through astrocyte signaling at synapses relatively distant from active synapses, a process termed lateral astrocyte synaptic regulation. This phenomenon resembles the classical heterosynaptic modulation but is mechanistically different because it involves astrocytes and its properties critically depend on the morphological and functional features of astrocytes. Therefore, the functional concept of the tripartite synapse as a fundamental unit must be expanded to include the interaction between tripartite synapses. Through lateral synaptic regulation, astrocytes serve as an active processing bridge for synaptic interaction and crosstalk between synapses with no direct neuronal connectivity, supporting the idea that neural network function results from the coordinated activity of astrocytes and neurons. PMID:25732135

  20. Localization of Presynaptic Plasticity Mechanisms Enables Functional Independence of Synaptic and Ectopic Transmission in the Cerebellum

    PubMed Central

    Dobson, Katharine L.; Bellamy, Tomas C.

    2015-01-01

    In the cerebellar molecular layer parallel fibre terminals release glutamate from both the active zone and from extrasynaptic “ectopic” sites. Ectopic release mediates transmission to the Bergmann glia that ensheathe the synapse, activating Ca2+-permeable AMPA receptors and glutamate transporters. Parallel fibre terminals exhibit several forms of presynaptic plasticity, including cAMP-dependent long-term potentiation and endocannabinoid-dependent long-term depression, but it is not known whether these presynaptic forms of long-term plasticity also influence ectopic transmission to Bergmann glia. Stimulation of parallel fibre inputs at 16 Hz evoked LTP of synaptic transmission, but LTD of ectopic transmission. Pharmacological activation of adenylyl cyclase by forskolin caused LTP at Purkinje neurons, but only transient potentiation at Bergmann glia, reinforcing the concept that ectopic sites lack the capacity to express sustained cAMP-dependent potentiation. Activation of mGluR1 caused depression of synaptic transmission via retrograde endocannabinoid signalling but had no significant effect at ectopic sites. In contrast, activation of NMDA receptors suppressed both synaptic and ectopic transmission. The results suggest that the signalling mechanisms for presynaptic LTP and retrograde depression by endocannabinoids are restricted to the active zone at parallel fibre synapses, allowing independent modulation of synaptic transmission to Purkinje neurons and ectopic transmission to Bergmann glia. PMID:26171253

  1. Changes in hippocampal synaptic functions and protein expression in monosodium glutamate-treated obese mice during development of glucose intolerance.

    PubMed

    Sasaki-Hamada, Sachie; Hojo, Yuki; Koyama, Hajime; Otsuka, Hayuma; Oka, Jun-Ichiro

    2015-05-01

    Glucose is the sole neural fuel for the brain and is essential for cognitive function. Abnormalities in glucose tolerance may be associated with impairments in cognitive function. Experimental obese model mice can be generated by an intraperitoneal injection of monosodium glutamate (MSG; 2 mg/g) once a day for 5 days from 1 day after birth. MSG-treated mice have been shown to develop glucose intolerance and exhibit chronic neuroendocrine dysfunction associated with marked cognitive malfunctions at 28-29  weeks old. Although hippocampal synaptic plasticity is impaired in MSG-treated mice, changes in synaptic transmission remain unknown. Here, we investigated whether glucose intolerance influenced cognitive function, synaptic properties and protein expression in the hippocampus. We demonstrated that MSG-treated mice developed glucose intolerance due to an impairment in the effectiveness of insulin actions, and showed cognitive impairments in the Y-maze test. Moreover, long-term potentiation (LTP) at Schaffer collateral-CA1 pyramidal synapses in hippocampal slices was impaired, and the relationship between the slope of extracellular field excitatory postsynaptic potential and stimulus intensity of synaptic transmission was weaker in MSG-treated mice. The protein levels of vesicular glutamate transporter 1 and GluA1 glutamate receptor subunits decreased in the CA1 region of MSG-treated mice. These results suggest that deficits in glutamatergic presynapses as well as postsynapses lead to impaired synaptic plasticity in MSG-treated mice during the development of glucose intolerance, though it remains unknown whether impaired LTP is due to altered inhibitory transmission. It may be important to examine changes in glucose tolerance in order to prevent cognitive malfunctions associated with diabetes. PMID:25851080

  2. Simulation of Postsynaptic Glutamate Receptors Reveals Critical Features of Glutamatergic Transmission

    PubMed Central

    Greget, Renaud; Pernot, Fabien; Bouteiller, Jean-Marie C.; Ghaderi, Viviane; Allam, Sushmita; Keller, Anne Florence; Ambert, Nicolas; Legendre, Arnaud; Sarmis, Merdan; Haeberle, Olivier; Faupel, Michel; Bischoff, Serge; Berger, Theodore W.; Baudry, Michel

    2011-01-01

    Activation of several subtypes of glutamate receptors contributes to changes in postsynaptic calcium concentration at hippocampal synapses, resulting in various types of changes in synaptic strength. Thus, while activation of NMDA receptors has been shown to be critical for long-term potentiation (LTP) and long term depression (LTD) of synaptic transmission, activation of metabotropic glutamate receptors (mGluRs) has been linked to either LTP or LTD. While it is generally admitted that dynamic changes in postsynaptic calcium concentration represent the critical elements to determine the direction and amplitude of the changes in synaptic strength, it has been difficult to quantitatively estimate the relative contribution of the different types of glutamate receptors to these changes under different experimental conditions. Here we present a detailed model of a postsynaptic glutamatergic synapse that incorporates ionotropic and mGluR type I receptors, and we use this model to determine the role of the different receptors to the dynamics of postsynaptic calcium with different patterns of presynaptic activation. Our modeling framework includes glutamate vesicular release and diffusion in the cleft and a glutamate transporter that modulates extracellular glutamate concentration. Our results indicate that the contribution of mGluRs to changes in postsynaptic calcium concentration is minimal under basal stimulation conditions and becomes apparent only at high frequency of stimulation. Furthermore, the location of mGluRs in the postsynaptic membrane is also a critical factor, as activation of distant receptors contributes significantly less to calcium dynamics than more centrally located ones. These results confirm the important role of glutamate transporters and of the localization of mGluRs in postsynaptic sites in their signaling properties, and further strengthen the notion that mGluR activation significantly contributes to postsynaptic calcium dynamics only following

  3. Effect of VGLUT inhibitors on glutamatergic synaptic transmission in the rodent hippocampus and prefrontal cortex.

    PubMed

    Neale, S A; Copeland, C S; Salt, T E

    2014-07-01

    Vesicular glutamate transporters (VGLUTs) are known to be important in the uptake of glutamate into vesicles in the presynaptic terminal; thereby playing a role in synaptic function. VGLUT dysfunction has also been suggested in neurological and psychiatric disorders such as epilepsy and schizophrenia. A number of compounds have been identified as VGLUT inhibitors; however, little is known as to how these compounds affect synaptic transmission. We therefore investigated the effects of structurally unrelated VGLUT inhibitors on synaptic transmission in the rodent hippocampus and prefrontal cortex. In the CA1 and dentate gyrus regions of the in vitro slice preparation of mouse hippocampus, AMPA receptor-mediated field excitatory postsynaptic potentials (fEPSPs) were evoked in response to Schaffer collateral/commissural pathway stimulation. Application of the VGLUT inhibitors Rose Bengal (RB), Congo Red (CR) or Chicago Sky Blue 6B (CB) resulted in a concentration-related reduction of fEPSP amplitudes. RB (30μM) or CB (300μM) also depressed NMDA receptor-mediated responses in the CA1 region. The naturally occurring kynurenine Xanthurenic Acid (XA) is reported to be a VGLUT inhibitor. We found XA attenuated both AMPA and NMDA receptor-mediated synaptic transmission. The potency order of the VGLUT inhibitors was consistent with literature Ki values for VGLUT inhibition. Impaired glutamatergic neurotransmission is believed to contribute to schizophrenia, and VGLUTs have also been implicated in this disease. We therefore investigated the effect of VGLUT inhibition in the prefrontal cortex. Application of the VGLUT inhibitors RB or CB resulted in a concentration-dependent reduction in the amplitude of glutamate receptor-mediated fEPSPs recorded in layer V/VI in response to stimulation in the forceps minor. We conclude that VGLUT inhibitors can modulate glutamatergic synaptic transmission in the PFC and hippocampus. This could be important in the pathophysiology of nervous

  4. Metabotropic glutamate receptors depress glutamate-mediated synaptic input to rat midbrain dopamine neurones in vitro.

    PubMed

    Wigmore, M A; Lacey, M G

    1998-02-01

    1. Glutamate (AMPA receptor-mediated) excitatory postsynaptic potentials (e.p.s.ps.), evoked by electrical stimulation rostral to the recording site, were examined by intracellular microelectrode recording from dopamine neurones in parasagittal slices of rat ventral midbrain. 2. The e.p.s.p. was depressed by the group III metabotropic glutamate (mGlu) receptor agonist L-2-amino-4-phosphonobutyric acid (L-AP4; 0.01-30 microM) by up to 60% with an EC50 of 0.82 microM. The depression induced by L-AP4 (3 microM) was reversed by the group III preferring mGlu receptor antagonist, alpha-methyl-4-phosphonophenylglycine (MPPG; 250 microM). 3. The group I and II mGlu agonist, 1S,3R-aminocyclopentanedicarboxylic acid (ACPD; 3-30 microM) also depressed the e.p.s.p. in a concentration-dependent manner. The effect of ACPD (10 microM) was reversed by (+)-alpha-methyl-4-carboxyphenylglycine (MCPG; 1 mM; 4 cells). This effect of ACPD was also partially antagonized (by 50.3+/-15.7%, 4 cells) by MPPG (250 microM). 4. The selective agonist at group I mGlu receptors, dihydroxyphenylglycine (DHPG; 100 microM), decreased e.p.s.p. amplitude by 27.1+/-8.2% (7 cells), as did the group II mGlu receptor-selective agonist (1S,1R,2'R,3'R)-2-(2,3-dicarboxycyclopropyl)glycine (DCG-IV; 1 microM) by 26.7+/-4.3% (5 cells). 5. DHPG (10-100 microM) caused a depolarization of the recorded cell, as did ACPD (3-30 microM), whereas no such postsynaptic effect of either L-AP4 or DCG-IV was observed. 6. These results provide evidence for the presence of presynaptic inhibitory metabotropic glutamate autoreceptors from the mGlu receptor groups II and III on descending glutamatergic inputs to midbrain dopamine neurones. Group I mGlu receptors mediate a postsynaptic depolarization, and can also depress glutamatergic transmission, but may not necessarily be localized presynaptically. These sites represent novel drug targets for treatment of schizophrenia and movement disorders of basal ganglia origin. PMID

  5. Metabotropic glutamate receptors depress glutamate-mediated synaptic input to rat midbrain dopamine neurones in vitro

    PubMed Central

    Wigmore, Mark A; Lacey, Michael G

    1998-01-01

    Glutamate (AMPA receptor-mediated) excitatory postsynaptic potentials (e.p.s.ps.), evoked by electrical stimulation rostral to the recording site, were examined by intracellular microelectrode recording from dopamine neurones in parasagittal slices of rat ventral midbrain. The e.p.s.p. was depressed by the group III metabotropic glutamate (mGlu) receptor agonist L-2-amino-4-phosphonobutyric acid (L-AP4; 0.01–30 μM) by up to 60% with an EC50 of 0.82 μM. The depression induced by L-AP4 (3 μM) was reversed by the group III preferring mGlu receptor antagonist, α-methyl-4-phosphonophenylglycine (MPPG; 250 μM). The group I and II mGlu agonist, 1S,3R-aminocyclopentanedicarboxylic acid (ACPD; 3–30 μM) also depressed the e.p.s.p. in a concentration-dependent manner. The effect of ACPD (10 μM) was reversed by (+)-α-methyl-4-carboxyphenylglycine (MCPG; 1 mM; 4 cells). This effect of ACPD was also partially antagonized (by 50.3±15.7%, 4 cells) by MPPG (250 μM). The selective agonist at group I mGlu receptors, dihydroxyphenylglycine (DHPG; 100 μM), decreased e.p.s.p. amplitude by 27.1±8.2% (7 cells), as did the group II mGlu receptor-selective agonist (1S,1′R,2′R,3′R)-2-(2,3-dicarboxycyclopropyl)glycine (DCG-IV; 1 μM) by 26.7±4.3% (5 cells). DHPG (10–100 μM) caused a depolarization of the recorded cell, as did ACPD (3–30 μM), whereas no such postsynaptic effect of either L-AP4 or DCG-IV was observed. These results provide evidence for the presence of presynaptic inhibitory metabotropic glutamate autoreceptors from the mGlu receptor groups II and III on descending glutamatergic inputs to midbrain dopamine neurones. Group I mGlu receptors mediate a postsynaptic depolarization, and can also depress glutamatergic transmission, but may not necessarily be localized presynaptically. These sites represent novel drug targets for treatment of schizophrenia and movement disorders of basal ganglia origin. PMID:9517386

  6. Extracellular ATP hydrolysis inhibits synaptic transmission by increasing ph buffering in the synaptic cleft.

    PubMed

    Vroman, Rozan; Klaassen, Lauw J; Howlett, Marcus H C; Cenedese, Valentina; Klooster, Jan; Sjoerdsma, Trijntje; Kamermans, Maarten

    2014-05-01

    Neuronal computations strongly depend on inhibitory interactions. One such example occurs at the first retinal synapse, where horizontal cells inhibit photoreceptors. This interaction generates the center/surround organization of bipolar cell receptive fields and is crucial for contrast enhancement. Despite its essential role in vision, the underlying synaptic mechanism has puzzled the neuroscience community for decades. Two competing hypotheses are currently considered: an ephaptic and a proton-mediated mechanism. Here we show that horizontal cells feed back to photoreceptors via an unexpected synthesis of the two. The first one is a very fast ephaptic mechanism that has no synaptic delay, making it one of the fastest inhibitory synapses known. The second one is a relatively slow (τ≈200 ms), highly intriguing mechanism. It depends on ATP release via Pannexin 1 channels located on horizontal cell dendrites invaginating the cone synaptic terminal. The ecto-ATPase NTPDase1 hydrolyses extracellular ATP to AMP, phosphate groups, and protons. The phosphate groups and protons form a pH buffer with a pKa of 7.2, which keeps the pH in the synaptic cleft relatively acidic. This inhibits the cone Ca²⁺ channels and consequently reduces the glutamate release by the cones. When horizontal cells hyperpolarize, the pannexin 1 channels decrease their conductance, the ATP release decreases, and the formation of the pH buffer reduces. The resulting alkalization in the synaptic cleft consequently increases cone glutamate release. Surprisingly, the hydrolysis of ATP instead of ATP itself mediates the synaptic modulation. Our results not only solve longstanding issues regarding horizontal cell to photoreceptor feedback, they also demonstrate a new form of synaptic modulation. Because pannexin 1 channels and ecto-ATPases are strongly expressed in the nervous system and pannexin 1 function is implicated in synaptic plasticity, we anticipate that this novel form of synaptic

  7. Extracellular ATP Hydrolysis Inhibits Synaptic Transmission by Increasing pH Buffering in the Synaptic Cleft

    PubMed Central

    Vroman, Rozan; Klaassen, Lauw J.; Howlett, Marcus H.C.; Cenedese, Valentina; Klooster, Jan; Sjoerdsma, Trijntje; Kamermans, Maarten

    2014-01-01

    Neuronal computations strongly depend on inhibitory interactions. One such example occurs at the first retinal synapse, where horizontal cells inhibit photoreceptors. This interaction generates the center/surround organization of bipolar cell receptive fields and is crucial for contrast enhancement. Despite its essential role in vision, the underlying synaptic mechanism has puzzled the neuroscience community for decades. Two competing hypotheses are currently considered: an ephaptic and a proton-mediated mechanism. Here we show that horizontal cells feed back to photoreceptors via an unexpected synthesis of the two. The first one is a very fast ephaptic mechanism that has no synaptic delay, making it one of the fastest inhibitory synapses known. The second one is a relatively slow (τ≈200 ms), highly intriguing mechanism. It depends on ATP release via Pannexin 1 channels located on horizontal cell dendrites invaginating the cone synaptic terminal. The ecto-ATPase NTPDase1 hydrolyses extracellular ATP to AMP, phosphate groups, and protons. The phosphate groups and protons form a pH buffer with a pKa of 7.2, which keeps the pH in the synaptic cleft relatively acidic. This inhibits the cone Ca2+ channels and consequently reduces the glutamate release by the cones. When horizontal cells hyperpolarize, the pannexin 1 channels decrease their conductance, the ATP release decreases, and the formation of the pH buffer reduces. The resulting alkalization in the synaptic cleft consequently increases cone glutamate release. Surprisingly, the hydrolysis of ATP instead of ATP itself mediates the synaptic modulation. Our results not only solve longstanding issues regarding horizontal cell to photoreceptor feedback, they also demonstrate a new form of synaptic modulation. Because pannexin 1 channels and ecto-ATPases are strongly expressed in the nervous system and pannexin 1 function is implicated in synaptic plasticity, we anticipate that this novel form of synaptic modulation

  8. Muscarinic regulation of dopamine and glutamate transmission in the nucleus accumbens

    PubMed Central

    Shin, Jung Hoon; Adrover, Martín F.; Wess, Jürgen; Alvarez, Veronica A.

    2015-01-01

    Cholinergic transmission in the striatum functions as a key modulator of dopamine (DA) transmission and synaptic plasticity, both of which are required for reward and motor learning. Acetylcholine (ACh) can elicit striatal DA release through activation of nicotinic ACh receptors (nAChRs) on DA axonal projections. However, it remains controversial how muscarinic ACh receptors (mAChRs) modulate striatal DA release, with studies reporting both potentiation and depression of striatal DA transmission by mAChR agonists. This study investigates the mAChR-mediated regulation of release from three types of midbrain neurons that project to striatum: DA, DA/glutamate, and glutamate neurons. We found that M5 mAChRs potentiate DA and glutamate release only from DA and DA/glutamate projections from the midbrain. We also show that M2/M4 mAChRs depress the nAChR-dependent mechanism of DA release in the striatum. These results suggest that M5 receptors on DA neuron terminals enhance DA release, whereas M2/M4 autoreceptors on cholinergic terminals inhibit ACh release and subsequent nAChR-dependent DA release. Our findings clarify the mechanisms of mAChR-dependent modulation of DA and glutamate transmission in the striatum. PMID:26080439

  9. Activation of synaptic group II metabotropic glutamate receptors induces long-term depression at GABAergic synapses in CNS neurons.

    PubMed

    Tang, Zheng-Quan; Liu, Yu-Wei; Shi, Wei; Dinh, Emilie Hoang; Hamlet, William R; Curry, Rebecca J; Lu, Yong

    2013-10-01

    Metabotropic glutamate receptor (mGluR)-dependent homosynaptic long-term depression (LTD) has been studied extensively at glutamatergic synapses in the CNS. However, much less is known about heterosynaptic long-term plasticity induced by mGluRs at inhibitory synapses. Here we report that pharmacological or synaptic activation of group II mGluRs (mGluR II) induces LTD at GABAergic synapses without affecting the excitatory glutamatergic transmission in neurons of the chicken cochlear nucleus. Coefficient of variation and failure rate analysis suggested that the LTD was expressed presynaptically. The LTD requires presynaptic spike activity, but does not require the activation of NMDA receptors. The classic cAMP-dependent protein kinase A signaling is involved in the transduction pathway. Remarkably, blocking mGluR II increased spontaneous GABA release, indicating the presence of tonic activation of mGluR II by ambient glutamate. Furthermore, synaptically released glutamate induced by electrical stimulations that concurrently activated both the glutamatergic and GABAergic pathways resulted in significant and constant suppression of GABA release at various stimulus frequencies (3.3, 100, and 300 Hz). Strikingly, low-frequency stimulation (1 Hz, 15 min) of the glutamatergic synapses induced heterosynaptic LTD of GABAergic transmission, and the LTD was blocked by mGluR II antagonist, indicating that synaptic activation of mGluR II induced the LTD. This novel form of long-term plasticity in the avian auditory brainstem may play a role in the development as well as in temporal processing in the sound localization circuit. PMID:24089501

  10. Coupling of energy metabolism and synaptic transmission at the transcriptional level: Role of nuclear respiratory factor 1 in regulating both cytochrome c oxidase and NMDA glutamate receptor subunit genes

    PubMed Central

    Dhar, Shilpa S.; Wong-Riley, Margaret T. T.

    2009-01-01

    Neuronal activity and energy metabolism are tightly coupled processes. Regions high in neuronal activity, especially of the glutamatergic type, have high levels of cytochrome c oxidase (COX). Perturbations in neuronal activity affect the expressions of COX and glutamatergic N-methyl-D-aspartate receptor subunit 1 (NR1). The present study sought to test our hypothesis that the coupling extends to the transcriptional level, whereby NR1 and possibly other NR subunits and COX are co-regulated by the same transcription factor, nuclear respiratory factor 1 (NRF-1), which regulates all COX subunit genes. By means of multiple approaches, including in silico analysis, electrophoretic mobility shift and supershift assays, in vivo chromatin immunoprecipitation, promoter mutations, and real-time quantitative PCR, NRF-1 was found to functionally bind to the promoters of Grin 1 (NR1), Grin 2b (NR2b) and COX subunit genes, but not of Grin2a and Grin3a genes. These transcripts were up-regulated by KCl and down-regulated by TTX in cultured primary neurons. However, silencing of NRF-1 with small interference RNA blocked the up-regulation of Grin1, Grin2b, and COX induced by KCl, and over-expression of NRF-1 rescued these transcripts that were suppressed by TTX. NRF-1 binding sites on Grin1 and Grin2b genes are also highly conserved among mice, rats, and humans. Thus, NRF-1 is an essential transcription factor critical in the co-regulation of NR1, NR2b, and COX, and coupling exists at the transcriptional level to ensure coordinated expressions of proteins important for synaptic transmission and energy metabolism. PMID:19144849

  11. Age-dependent enhancement of inhibitory synaptic transmission in CA1 pyramidal neurons via GluR5 kainate receptors.

    PubMed

    Xu, Changqing; Cui, Changhai; Alkon, Daniel L

    2009-08-01

    Changes in hippocampal synaptic networks during aging may contribute to age-dependent compromise of cognitive functions such as learning and memory. Previous studies have demonstrated that GABAergic synaptic transmission exhibits age-dependent changes. To better understand such age-dependent changes of GABAergic synaptic inhibition, we performed whole-cell recordings from pyramidal cells in the CA1 area of acute hippocampal slices on aged (24-26 months old) and young (2-4 months old) Brown-Norway rats. We found that the frequency and amplitude of spontaneous inhibitory postsynaptic current (IPSCs) were significantly increased in aged rats, but the frequency and amplitude of mIPSCs were decreased. Furthermore, the regulation of GABAergic synaptic transmission by GluR5 containing kainate receptors was enhanced in aged rats, which was revealed by using LY382884 (a GluR5 kainate receptor antagonist) and ATPA (a GluR5 kainate receptor agonist). Moreover, we demonstrated that vesicular glutamate transporters are involved in the kainate receptor dependent regulation of sIPSCs. Taken together, these results suggest that GABAergic synaptic transmission is potentiated in aged rats, and GluR5 containing kainate receptors regulate the inhibitory synaptic transmission through endogenous glutamate. These alterations of GABAergic input with aging could contribute to age-dependent cognitive decline. PMID:19123252

  12. Glial glutamate transporter and glutamine synthetase regulate GABAergic synaptic strength in the spinal dorsal horn.

    PubMed

    Jiang, Enshe; Yan, Xisheng; Weng, Han-Rong

    2012-05-01

    Decreased GABAergic synaptic strength ('disinhibition') in the spinal dorsal horn is a crucial mechanism contributing to the development and maintenance of pathological pain. However, mechanisms leading to disinhibition in the spinal dorsal horn remain elusive. We investigated the role of glial glutamate transporters (GLT-1 and GLAST) and glutamine synthetase in maintaining GABAergic synaptic activity in the spinal dorsal horn. Electrically evoked GABAergic inhibitory post-synaptic currents (eIPSCs), spontaneous IPSCs (sIPSCs) and miniature IPSCs were recorded in superficial spinal dorsal horn neurons of spinal slices from young adult rats. We used (2S,3S)-3-[3-[4-(trifluoromethyl)benzoylamino]benzyloxy]aspartate (TFB-TBOA), to block both GLT-1 and GLAST and dihydrokainic acid to block only GLT-1. We found that blockade of both GLAST and GLT-1 and blockade of only GLT-1 in the spinal dorsal horn decreased the amplitude of GABAergic eIPSCs, as well as both the amplitude and frequency of GABAergic sIPSCs or miniature IPSCs. Pharmacological inhibition of glial glutamine synthetase had similar effects on both GABAergic eIPSCs and sIPSCs. We provided evidence demonstrating that the reduction in GABAergic strength induced by the inhibition of glial glutamate transporters is due to insufficient GABA synthesis through the glutamate-glutamine cycle between astrocytes and neurons. Thus, our results indicate that deficient glial glutamate transporters and glutamine synthetase significantly attenuate GABAergic synaptic strength in the spinal dorsal horn, which may be a crucial synaptic mechanism underlying glial-neuronal interactions caused by dysfunctional astrocytes in pathological pain conditions. PMID:22339645

  13. Astroglial glutamate transporter deficiency increases synaptic excitability and leads to pathological repetitive behaviors in mice.

    PubMed

    Aida, Tomomi; Yoshida, Junichi; Nomura, Masatoshi; Tanimura, Asami; Iino, Yusuke; Soma, Miho; Bai, Ning; Ito, Yukiko; Cui, Wanpeng; Aizawa, Hidenori; Yanagisawa, Michiko; Nagai, Terumi; Takata, Norio; Tanaka, Kenji F; Takayanagi, Ryoichi; Kano, Masanobu; Götz, Magdalena; Hirase, Hajime; Tanaka, Kohichi

    2015-06-01

    An increase in the ratio of cellular excitation to inhibition (E/I ratio) has been proposed to underlie the pathogenesis of neuropsychiatric disorders, such as autism spectrum disorders (ASD), obsessive-compulsive disorder (OCD), and Tourette's syndrome (TS). A proper E/I ratio is achieved via factors expressed in neuron and glia. In astrocytes, the glutamate transporter GLT1 is critical for regulating an E/I ratio. However, the role of GLT1 dysfunction in the pathogenesis of neuropsychiatric disorders remains unknown because mice with a complete deficiency of GLT1 exhibited seizures and premature death. Here, we show that astrocyte-specific GLT1 inducible knockout (GLAST(CreERT2/+)/GLT1(flox/flox), iKO) mice exhibit pathological repetitive behaviors including excessive and injurious levels of self-grooming and tic-like head shakes. Electrophysiological studies reveal that excitatory transmission at corticostriatal synapse is normal in a basal state but is increased after repetitive stimulation. Furthermore, treatment with an N-methyl-D-aspartate (NMDA) receptor antagonist memantine ameliorated the pathological repetitive behaviors in iKO mice. These results suggest that astroglial GLT1 has a critical role in controlling the synaptic efficacy at corticostriatal synapses and its dysfunction causes pathological repetitive behaviors. PMID:25662838

  14. Astroglial Glutamate Transporter Deficiency Increases Synaptic Excitability and Leads to Pathological Repetitive Behaviors in Mice

    PubMed Central

    Aida, Tomomi; Yoshida, Junichi; Nomura, Masatoshi; Tanimura, Asami; Iino, Yusuke; Soma, Miho; Bai, Ning; Ito, Yukiko; Cui, Wanpeng; Aizawa, Hidenori; Yanagisawa, Michiko; Nagai, Terumi; Takata, Norio; Tanaka, Kenji F; Takayanagi, Ryoichi; Kano, Masanobu; Götz, Magdalena; Hirase, Hajime; Tanaka, Kohichi

    2015-01-01

    An increase in the ratio of cellular excitation to inhibition (E/I ratio) has been proposed to underlie the pathogenesis of neuropsychiatric disorders, such as autism spectrum disorders (ASD), obsessive-compulsive disorder (OCD), and Tourette's syndrome (TS). A proper E/I ratio is achieved via factors expressed in neuron and glia. In astrocytes, the glutamate transporter GLT1 is critical for regulating an E/I ratio. However, the role of GLT1 dysfunction in the pathogenesis of neuropsychiatric disorders remains unknown because mice with a complete deficiency of GLT1 exhibited seizures and premature death. Here, we show that astrocyte-specific GLT1 inducible knockout (GLASTCreERT2/+/GLT1flox/flox, iKO) mice exhibit pathological repetitive behaviors including excessive and injurious levels of self-grooming and tic-like head shakes. Electrophysiological studies reveal that excitatory transmission at corticostriatal synapse is normal in a basal state but is increased after repetitive stimulation. Furthermore, treatment with an N-methyl-D-aspartate (NMDA) receptor antagonist memantine ameliorated the pathological repetitive behaviors in iKO mice. These results suggest that astroglial GLT1 has a critical role in controlling the synaptic efficacy at corticostriatal synapses and its dysfunction causes pathological repetitive behaviors. PMID:25662838

  15. Impaired circadian photosensitivity in mice lacking glutamate transmission from retinal melanopsin cells.

    PubMed

    Gompf, Heinrich S; Fuller, Patrick M; Hattar, Samer; Saper, Clifford B; Lu, Jun

    2015-02-01

    Intrinsically photoreceptive retinal ganglion cells (ipRGCs) contain the photopigment melanopsin and convey retinal light inputs to the circadian system via the retinohypothalamic tract (RHT) projection to the suprachiasmatic nucleus (SCN). The principal neurotransmitter of this projection is glutamate, and ipRGCs use the vesicular glutamate transporter 2 (VGLUT2) to package glutamate into synaptic vesicles. However, these neurons contain other potential neurotransmitters, such as pituitary adenylate cyclase activating polypeptide (PACAP). To test the role of glutamate in mediating ipRGC light inputs into the SCN, we crossed mice in which Cre-recombinase expression is driven by the melanopsin promotor (Opn4(Cre/+)) with mice in which the second exon of VGLUT2 is flanked by loxP sites (VGLUT2(fl/fl)), producing ipRGCs that are unable to package glutamate into synaptic vesicles. Such mice had free-running circadian rhythms that did not entrain to a 12:12 light-dark (12:12 LD) cycle, nor did they show a phase delay after a 45-min light pulse administered at circadian time (CT) 14. A small subset of the mice did appear to entrain to the 12:12 LD cycle with a positive phase angle to lights-off; a similar entrainment pattern could be achieved in free-running mice if they were exposed to a 12:12 LD cycle with light of a greater intensity. Glutamate transmission from the ipRGCs is necessary for normal light entrainment of the SCN at moderate (0.35 W/m(2)) light levels, but residual transmission (possibly by PACAP in ipRGCs or by other RGCs) can weakly entrain animals, particularly at very high (6.53 W/m(2)) light levels, although it may be less effective at suppressing locomotor activity (light masking). PMID:25512304

  16. Synaptic unreliability facilitates information transmission in balanced cortical populations

    NASA Astrophysics Data System (ADS)

    Gatys, Leon A.; Ecker, Alexander S.; Tchumatchenko, Tatjana; Bethge, Matthias

    2015-06-01

    Synaptic unreliability is one of the major sources of biophysical noise in the brain. In the context of neural information processing, it is a central question how neural systems can afford this unreliability. Here we examine how synaptic noise affects signal transmission in cortical circuits, where excitation and inhibition are thought to be tightly balanced. Surprisingly, we find that in this balanced state synaptic response variability actually facilitates information transmission, rather than impairing it. In particular, the transmission of fast-varying signals benefits from synaptic noise, as it instantaneously increases the amount of information shared between presynaptic signal and postsynaptic current. Furthermore we show that the beneficial effect of noise is based on a very general mechanism which contrary to stochastic resonance does not reach an optimum at a finite noise level.

  17. Metabotropic glutamate receptors depress vagal and aortic baroreceptor signal transmission in the NTS.

    PubMed

    Liu, Z; Chen, C Y; Bonham, A C

    1998-11-01

    We sought to determine whether metabotropic glutamate receptors contribute to frequency-dependent depression of vagal and aortic baroreceptor signal transmission in the nucleus of the solitary tract (NTS) in vivo. In alpha-chloralose-anesthetized rabbits, we determined the number of extracellular action potentials synaptically evoked by low (1 Hz)- or high-frequency vagal (3-20 Hz) or aortic depressor nerve (ADN) (6-80 Hz) stimulation and postsynaptically evoked by the ionotropic glutamate receptor agonist alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA). The metabotropic glutamate receptor agonist (2S,1'S, 2'S)-2-(carboxycyclopropyl)glycine (L-CCG-I) attenuated NTS responses monosynaptically evoked by 1-Hz vagus stimulation by 34% (n = 25; P = 0.011), while augmenting AMPA-evoked responses by 64% (n = 17; P = 0.026). The metabotropic glutamate receptor antagonist alpha-methyl-4-phosphonophenylglycine (MPPG) did not affect NTS responses to low-frequency vagal stimulation (n = 11) or AMPA (n = 10) but augmented responses to high-frequency stimulation by 50% (n = 25; P = 0.0001). MPPG also augmented NTS responses to high-frequency ADN stimulation by 35% (n = 9; P = 0.048) but did not affect responses to low-frequency stimulation (n = 9) or AMPA (n = 7). The results suggest that metabotropic glutamate receptors, presumably at presynaptic sites, contribute to frequency-dependent depression of vagal and aortic baroreceptor signal transmission in NTS. PMID:9815076

  18. GluN3A promotes NMDA spiking by enhancing synaptic transmission in Huntington's disease models.

    PubMed

    Mahfooz, Kashif; Marco, Sonia; Martínez-Turrillas, Rebeca; Raja, Mathan K; Pérez-Otaño, Isabel; Wesseling, John F

    2016-09-01

    Age-inappropriate expression of juvenile NMDA receptors (NMDARs) containing GluN3A subunits has been linked to synapse loss and death of spiny projection neurons of the striatum (SPNs) in Huntington's disease (HD). Here we show that suppressing GluN3A expression prevents a multivariate synaptic transmission phenotype that precedes morphological signs at early prodromal stages. We start by confirming that afferent fiber stimulation elicits larger synaptic responses mediated by both AMPA receptors and NMDARs in SPNs in the YAC128 mouse model of HD. We then show that the enhancement mediated by both is fully prevented by suppressing GluN3A expression. Strong fiber-stimulation unexpectedly elicited robust NMDAR-mediated electrogenic events (termed "upstates" or "NMDA spikes"), and the effective threshold for induction was more than 2-fold lower in YAC128 SPNs because of the enhanced synaptic transmission. The threshold could be restored to control levels by suppressing GluN3A expression or by applying the weak NMDAR blocker memantine. However, the threshold was not affected by preventing glutamate spillover from synaptic clefts. Instead, long-lasting NMDAR responses interpreted previously as activation of extrasynaptic receptors by spilled-over glutamate were caused by NMDA spikes occurring in voltage clamp mode as escape potentials. Together, the results implicate GluN3A reactivation in a broad spectrum of early-stage synaptic transmission deficits in YAC128 mice; question the current concept that NMDAR mislocalization is the pathological trigger in HD; and introduce NMDA spikes as a new candidate mechanism for coupling NMDARs to neurodegeneration. PMID:27072890

  19. Synaptic transmission at retinal ribbon synapses

    PubMed Central

    Heidelberger, Ruth; Thoreson, Wallace B.; Witkovsky, Paul

    2006-01-01

    The molecular organization of ribbon synapses in photoreceptors and ON bipolar cells is reviewed in relation to the process of neurotransmitter release. The interactions between ribbon synapse-associated proteins, synaptic vesicle fusion machinery and the voltage-gated calcium channels that gate transmitter release at ribbon synapses are discussed in relation to the process of synaptic vesicle exocytosis. We describe structural and mechanistic specializations that permit the ON bipolar cell to release transmitter at a much higher rate than the photoreceptor does, under in vivo conditions. We also consider the modulation of exocytosis at photoreceptor synapses, with an emphasis on the regulation of calcium channels. PMID:16027025

  20. Metabotropic Glutamate Receptor–Mediated Use–Dependent Down-Regulation of Synaptic Excitability Involves the Fragile X Mental Retardation Protein

    PubMed Central

    Repicky, Sarah; Broadie, Kendal

    2009-01-01

    Loss of the mRNA-binding protein FMRP results in the most common inherited form of both mental retardation and autism spectrum disorders: fragile X syndrome (FXS). The leading FXS hypothesis proposes that metabotropic glutamate receptor (mGluR) signaling at the synapse controls FMRP function in the regulation of local protein translation to modulate synaptic transmission strength. In this study, we use the Drosophila FXS disease model to test the relationship between Drosophila FMRP (dFMRP) and the sole Drosophila mGluR (dmGluRA) in regulation of synaptic function, using two-electrode voltage-clamp recording at the glutamatergic neuromuscular junction (NMJ). Null dmGluRA mutants show minimal changes in basal synapse properties but pronounced defects during sustained high-frequency stimulation (HFS). The double null dfmr1;dmGluRA mutant shows repression of enhanced augmentation and delayed onset of premature long-term facilitation (LTF) and strongly reduces grossly elevated post-tetanic potentiation (PTP) phenotypes present in dmGluRA-null animals. Null dfmr1 mutants show features of synaptic hyperexcitability, including multiple transmission events in response to a single stimulus and cyclic modulation of transmission amplitude during prolonged HFS. The double null dfmr1;dmGluRA mutant shows amelioration of these defects but does not fully restore wildtype properties in dfmr1-null animals. These data suggest that dmGluRA functions in a negative feedback loop in which excess glutamate released during high-frequency transmission binds the glutamate receptor to dampen synaptic excitability, and dFMRP functions to suppress the translation of proteins regulating this synaptic excitability. Removal of the translational regulator partially compensates for loss of the receptor and, similarly, loss of the receptor weakly compensates for loss of the translational regulator. PMID:19036865

  1. Distinctive PSA-NCAM and NCAM Hallmarks in Glutamate-Induced Dendritic Atrophy and Synaptic Disassembly

    PubMed Central

    Podestá, María Fernanda; Yam, Patricia; Codagnone, Martín Gabriel; Uccelli, Nonthué Alejandra; Colman, David; Reinés, Analía

    2014-01-01

    Dendritic and synapse remodeling are forms of structural plasticity that play a critical role in normal hippocampal function. Neural cell adhesion molecule (NCAM) and its polysialylated form (PSA-NCAM) participate in neurite outgrowth and synapse formation and plasticity. However, it remains unclear whether they contribute to dendritic retraction and synaptic disassembly. Cultured hippocampal neurons exposed to glutamate (5 µM) showed a reduced MAP-2 (+) area in the absence of neuronal death 24 h after the insult. Concomitantly, synapse loss, revealed by decreased synaptophysin and post-synaptic density-95 cluster number and area, together with changes in NCAM and PSA-NCAM levels were found. Dendritic atrophy and PSA-NCAM reduction proved NMDA-receptor dependent. Live-imaging experiments evidenced dendritic atrophy 4 h after the insult; this effect was preceded by smaller NCAM clusters (1 h) and decreased surface and total PSA-NCAM levels (3 h). Simultaneously, total NCAM cluster number and area remained unchanged. The subsequent synapse disassembly (6 h) was accompanied by reductions in total NCAM cluster number and area. A PSA mimetic peptide prevented both the dendritic atrophy and the subsequent synaptic changes (6 h) but had no effect on the earliest synaptic remodeling (3 h). Thus, NCAM-synaptic reorganization and PSA-NCAM level decrease precede glutamate-induced dendritic atrophy, whereas the NCAM level reduction is a delayed event related to synapse loss. Consequently, distinctive stages in PSA-NCAM/NCAM balance seem to accompany glutamate-induced dendritic atrophy and synapse loss. PMID:25279838

  2. LGI1 acts presynaptically to regulate excitatory synaptic transmission during early postnatal development.

    PubMed

    Boillot, Morgane; Lee, Chun-Yao; Allene, Camille; Leguern, Eric; Baulac, Stéphanie; Rouach, Nathalie

    2016-01-01

    The secreted leucine-rich glioma inactivated 1 (LGI1) protein is an important actor for human seizures of both genetic and autoimmune etiology: mutations in LGI1 cause inherited temporal lobe epilepsy, while LGI1 is involved in antibody-mediated encephalitis. Remarkably, Lgi1-deficient (Lgi1(-/-)) mice recapitulate the epileptic disorder and display early-onset spontaneous seizures. To understand how Lgi1-deficiency leads to seizures during postnatal development, we here investigated the early functional and structural defects occurring before seizure onset in Lgi1(-/-) mice. We found an increased excitatory synaptic transmission in hippocampal slices from Lgi1(-/-) mice. No structural alteration in the morphology of pyramidal cell dendrites and synapses was observed at this stage, indicating that Lgi1-deficiency is unlikely to trigger early developmental abnormalities. Consistent with the presynaptic subcellular localization of the protein, Lgi1-deficiency caused presynaptic defects, with no alteration in postsynaptic AMPA receptor activity in Lgi1-/- pyramidal cells before seizure onset. Presynaptic dysfunction led to increased synaptic glutamate levels, which were associated with hyperexcitable neuronal networks. Altogether, these data show that Lgi1 acts presynaptically as a negative modulator of excitatory synaptic transmission during early postnatal development. We therefore here reveal that increased presynaptic glutamate release is a key early event resulting from Lgi1-deficiency, which likely contributes to epileptogenesis. PMID:26878798

  3. LGI1 acts presynaptically to regulate excitatory synaptic transmission during early postnatal development

    PubMed Central

    Boillot, Morgane; Lee, Chun-Yao; Allene, Camille; Leguern, Eric; Baulac, Stéphanie; Rouach, Nathalie

    2016-01-01

    The secreted leucine-rich glioma inactivated 1 (LGI1) protein is an important actor for human seizures of both genetic and autoimmune etiology: mutations in LGI1 cause inherited temporal lobe epilepsy, while LGI1 is involved in antibody-mediated encephalitis. Remarkably, Lgi1-deficient (Lgi1−/−) mice recapitulate the epileptic disorder and display early-onset spontaneous seizures. To understand how Lgi1-deficiency leads to seizures during postnatal development, we here investigated the early functional and structural defects occurring before seizure onset in Lgi1−/− mice. We found an increased excitatory synaptic transmission in hippocampal slices from Lgi1−/− mice. No structural alteration in the morphology of pyramidal cell dendrites and synapses was observed at this stage, indicating that Lgi1-deficiency is unlikely to trigger early developmental abnormalities. Consistent with the presynaptic subcellular localization of the protein, Lgi1-deficiency caused presynaptic defects, with no alteration in postsynaptic AMPA receptor activity in Lgi1−/− pyramidal cells before seizure onset. Presynaptic dysfunction led to increased synaptic glutamate levels, which were associated with hyperexcitable neuronal networks. Altogether, these data show that Lgi1 acts presynaptically as a negative modulator of excitatory synaptic transmission during early postnatal development. We therefore here reveal that increased presynaptic glutamate release is a key early event resulting from Lgi1-deficiency, which likely contributes to epileptogenesis. PMID:26878798

  4. Synaptic modulation of excitatory synaptic transmission by nicotinic acetylcholine receptors in spinal ventral horn neurons.

    PubMed

    Mine, N; Taniguchi, W; Nishio, N; Izumi, N; Miyazaki, N; Yamada, H; Nakatsuka, T; Yoshida, M

    2015-04-01

    Nicotinic acetylcholine receptors (nAChRs) are distributed widely in the central nervous system and play important roles in higher brain functions, including learning, memory, and recognition. However, functions of the cholinergic system in spinal motoneurons remain poorly understood. In this study, we investigated the actions of presynaptic and postsynaptic nAChRs in spinal ventral horn neurons by performing whole-cell patch-clamp recordings on lumbar slices from male rats. The application of nicotine or acetylcholine generated slow inward currents and increased the frequency and amplitude of spontaneous excitatory postsynaptic currents (sEPSCs). Slow inward currents by acetylcholine or nicotine were not inhibited by tetrodotoxin (TTX) or glutamate receptor antagonists. In the presence of TTX, the frequency and amplitude of miniature excitatory postsynaptic currents (mEPSCs) were also increased by acetylcholine or nicotine. A selective α4β2 nicotinic receptor antagonist, dihydro-β-erythroidine hydrobromide (DhβE), significantly decreased nicotine-induced inward currents without affecting the enhancement of sEPSCs and mEPSCs. In addition, a selective α7 nicotinic receptor antagonist, methyllycaconitine, did not affect either nicotine-induced inward currents or the enhancement of sEPSCs and mEPSCs. These results suggest that α4β2 AChRs are localized at postsynaptic sites in the spinal ventral horn, non-α4β2 and non-α7 nAChRs are located presynaptically, and nAChRs enhance excitatory synaptic transmission in the spinal ventral horn. PMID:25613686

  5. Decreased glial and synaptic glutamate uptake in the striatum of HIV-1 gp120 transgenic mice.

    PubMed

    Melendez, Roberto I; Roman, Cristina; Capo-Velez, Coral M; Lasalde-Dominicci, Jose A

    2016-06-01

    The mechanisms leading to the neurocognitive deficits in humans with immunodeficiency virus type 1 (HIV-1) are not well resolved. A number of cell culture models have demonstrated that the HIV-envelope glycoprotein 120 (gp120) decreases the reuptake of glutamate, which is necessary for learning, memory, and synaptic plasticity. However, the impact of brain HIV-1 gp120 on glutamate uptake systems in vivo remains unknown. Notably, alterations in brain glutamate uptake systems are implicated in a number of neurodegenerative and neurocognitive disorders. We characterized the kinetic properties of system XAG (sodium-dependent) and systems xc- (sodium-independent) [3H]-L-glutamate uptake in the striatum and hippocampus of HIV-1 gp120 transgenic mice, an established model of HIV neuropathology. We determined the kinetic constant Vmax (maximal velocity) and Km (affinity) of both systems XAG and xc- using subcellular preparations derived from neurons and glial cells. We show significant (30-35 %) reductions in the Vmax of systems XAG and xc- in both neuronal and glial preparations derived from the striatum, but not from the hippocampus of gp120 mice relative to wild-type (WT) controls. Moreover, immunoblot analysis showed that the protein expression of glutamate transporter subtype-1 (GLT-1), the predominant brain glutamate transporter, was significantly reduced in the striatum but not in the hippocampus of gp120 mice. These extensive and region-specific deficits of glutamate uptake likely contribute to the development and/or severity of HIV-associated neurocognitive disorders. Understanding the role of striatal glutamate uptake systems in HIV-1 gp120 may advance the development of new therapeutic strategies to prevent neuronal damage and improve cognitive function in HIV patients. PMID:26567011

  6. Local synaptic release of glutamate from neurons in the rat hypothalamic arcuate nucleus.

    PubMed Central

    Belousov, A B; van den Pol, A N

    1997-01-01

    1. The hypothalamic arcuate nucleus (ARC) contains neuroendocrine neurons that regulate endocrine secretions by releasing substances which control anterior pituitary hormonal release into the portal blood stream. Many neuroactive substances have been identified in the ARC, but the existence of excitatory neurons in the ARC and the identity of an excitatory transmitter have not been investigated physiologically. 2. In the present experiments using whole-cell current- and voltage-clamp recording of neurons from cultures and slices of the ARC, we demonstrate for the first time that some of the neurons in the ARC secrete glutamate as their transmitter. 3. Using microdrop stimulation of presynaptic neurons in ARC slices, we found that local axons from these glutamatergic neurons make local synaptic contact with other neurons in the ARC and that all evoked excitatory postsynaptic potentials could be blocked by the selective ionotropic glutamate receptor antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 10 microM) and D,L-2-amino-5-phosphonovalerate (AP5; 100 microM). To determine the identity of ARC neurons postsynaptic to local glutamatergic neurons, we used antidromic stimulation to reveal that many of these cells were neuroendocrine neurons by virtue of their maintaining axon terminals in the median eminence. 4. In ARC cultures, postsynaptic potentials, both excitatory and inhibitory, were virtually eliminated by the glutamate receptor antagonists AP5 and CNQX, underlining the functional importance of glutamate within this part of the neuroendocrine brain. 5. GABA was secreted by a subset of ARC neurons from local axons. The GABAA receptor antagonist bicuculline released glutamatergic neurons from chronic inhibition mediated by synaptically released GABA, resulting in further depolarization and an increase in the amplitude and frequency of glutamate-mediated excitatory postsynaptic potentials. Images Figure 1 PMID:9130170

  7. Melatonin receptor activation increases glutamatergic synaptic transmission in the rat medial lateral habenula.

    PubMed

    Evely, Katherine M; Hudson, Randall L; Dubocovich, Margarita L; Haj-Dahmane, Samir

    2016-05-01

    Melatonin (MLT) is secreted from the pineal gland and mediates its physiological effects through activation of two G protein-coupled receptors, MT1 and MT2 . These receptors are expressed in several brain areas, including the habenular complex, a pair of nuclei that relay information from forebrain to midbrain and modulate a plethora of behaviors, including sleep, mood, and pain. However, so far, the precise mechanisms by which MLT control the function of habenula neurons remain unknown. Using whole cell recordings from male rat brain slices, we examined the effects of MLT on the excitability of medial lateral habenula (MLHb) neurons. We found that MLT had no significant effects on the intrinsic excitability of MLHb neurons, but profoundly increased the amplitude of glutamate-mediated evoked excitatory post-synaptic currents (EPSC). The increase in strength of glutamate synapses onto MLHb neurons was mediated by an increase in glutamate release. The MLT-induced increase in glutamatergic synaptic transmission was blocked by the competitive MT1 /MT2 receptor antagonist luzindole (LUZ). These results unravel a potential cellular mechanism by which MLT receptor activation enhances the excitability of MLHb neurons. The MLT-mediated control of glutamatergic inputs to the MLHb may play a key role in the modulation of various behaviors controlled by the habenular complex. PMID:26799638

  8. Vesicular Monoamine and Glutamate Transporters Select Distinct Synaptic Vesicle Recycling Pathways

    PubMed Central

    Onoa, Bibiana; Li, Haiyan; Gagnon-Bartsch, Johann A.; Elias, Laura A. B.; Edwards, Robert H.

    2011-01-01

    Previous work has characterized the properties of neurotransmitter release at excitatory and inhibitory synapses, but we know remarkably little about the properties of monoamine release because these neuromodulators do not generally produce a fast ionotropic response. Since dopamine and serotonin neurons can also release glutamate in vitro and in vivo, we have used the vesicular monoamine transporter VMAT2 and the vesicular glutamate transporter VGLUT1 to compare the localization and recycling of synaptic vesicles that store, respectively, monoamines and glutamate. First, VMAT2 segregates partially from VGLUT1 in the boutons of midbrain dopamine neurons, indicating the potential for distinct release sites. Second, endocytosis after stimulation is slower for VMAT2 than VGLUT1. During the stimulus, however, the endocytosis of VMAT2 (but not VGLUT1) accelerates dramatically in midbrain dopamine but not hippocampal neurons, indicating a novel, cell-specific mechanism to sustain high rates of release. On the other hand, we find that in both midbrain dopamine and hippocampal neurons, a substantially smaller proportion of VMAT2 than VGLUT1 is available for evoked release, and VMAT2 shows considerably more dispersion along the axon after exocytosis than VGLUT1. Even when expressed in the same neuron, the two vesicular transporters thus target to distinct populations of synaptic vesicles, presumably due to their selection of distinct recycling pathways. PMID:20534840

  9. Neuronal excitability: voltage-dependent currents and synaptic transmission.

    PubMed

    Rutecki, P A

    1992-04-01

    Neuronal membrane excitability and the synaptic connections among neurons produce behavior and cognition. The intracellular compartment of neurons is negatively charged relative to the extracellular space, and this charge, as well as current flow, is produced by ions. From the perspective of charged ions, the lipid bilayer of the neuronal membrane acts as a capacitor, and transmembrane glycoprotein pores or channels act as resistors. The open and closed states of ionic channels determine the membrane potential. At equilibrium, the lowest resistance or greatest permeability is for potassium, and the resting membrane potential is close to the equilibrium potential for potassium. When a channel is opened, permeable ions diffuse down their electrochemical gradients and the membrane potential is changed. Channels are gated (opened or closed) by voltage, neurotransmitters, and second messengers. The neuron integrates synaptic potentials produced by transmitter-gated channel activity and either generates a subthreshold potential, or a suprathreshold depolarization that generates an action potential or a burst of action potentials. Action potential generation is mediated by a large, brief sodium influx that is followed by activation of a voltage-dependent potassium eflux. The pattern of action potential firing is dependent on the interaction of a repertoire of voltage-dependent ion conductances. The action potential is the main signaling mechanism to activate synaptic transmission at axon terminals. Synaptic transmission is graded depending on the amount of calcium entering the presynaptic terminal. The number of action potentials, or the shape of the action potential, will determine the amount of calcium entering the terminal and the efficacy of synaptic transmission. Presynaptic ion channels may also be controlled by neurotransmitters or modulators and affect synaptic transmission by altering the amount of calcium influx. PMID:1375602

  10. Defective Glycinergic Synaptic Transmission in Zebrafish Motility Mutants

    PubMed Central

    Hirata, Hiromi; Carta, Eloisa; Yamanaka, Iori; Harvey, Robert J.; Kuwada, John Y.

    2009-01-01

    Glycine is a major inhibitory neurotransmitter in the spinal cord and brainstem. Recently, in vivo analysis of glycinergic synaptic transmission has been pursued in zebrafish using molecular genetics. An ENU mutagenesis screen identified two behavioral mutants that are defective in glycinergic synaptic transmission. Zebrafish bandoneon (beo) mutants have a defect in glrbb, one of the duplicated glycine receptor (GlyR) β subunit genes. These mutants exhibit a loss of glycinergic synaptic transmission due to a lack of synaptic aggregation of GlyRs. Due to the consequent loss of reciprocal inhibition of motor circuits between the two sides of the spinal cord, motor neurons activate simultaneously on both sides resulting in bilateral contraction of axial muscles of beo mutants, eliciting the so-called ‘accordion’ phenotype. Similar defects in GlyR subunit genes have been observed in several mammals and are the basis for human hyperekplexia/startle disease. By contrast, zebrafish shocked (sho) mutants have a defect in slc6a9, encoding GlyT1, a glycine transporter that is expressed by astroglial cells surrounding the glycinergic synapse in the hindbrain and spinal cord. GlyT1 mediates rapid uptake of glycine from the synaptic cleft, terminating synaptic transmission. In zebrafish sho mutants, there appears to be elevated extracellular glycine resulting in persistent inhibition of postsynaptic neurons and subsequent reduced motility, causing the ‘twitch-once’ phenotype. We review current knowledge regarding zebrafish ‘accordion’ and ‘twitch-once’ mutants, including beo and sho, and report the identification of a new α2 subunit that revises the phylogeny of zebrafish GlyRs. PMID:20161699

  11. Progesterone Regulation of Synaptic Transmission and Plasticity in Rodent Hippocampus

    ERIC Educational Resources Information Center

    Foy, Michael R.; Akopian, Garnik; Thompson, Richard F.

    2008-01-01

    Ovarian hormones influence memory formation by eliciting changes in neural activity. The effects of various concentrations of progesterone (P4) on synaptic transmission and plasticity associated with long-term potentiation (LTP) and long-term depression (LTD) were studied using in vitro hippocampal slices. Extracellular studies show that the…

  12. Group I Metabotropic Glutamate Receptor-Mediated Gene Transcription and Implications for Synaptic Plasticity and Diseases

    PubMed Central

    Wang, Hansen; Zhuo, Min

    2012-01-01

    Stimulation of group I metabotropic glutamate receptors (mGluRs) initiates a wide variety of signaling pathways. Group I mGluR activation can regulate gene expression at both translational and transcriptional levels, and induces translation or transcription-dependent synaptic plastic changes in neurons. The group I mGluR-mediated translation-dependent neural plasticity has been well reviewed. In this review, we will highlight group I mGluR-induced gene transcription and its role in synaptic plasticity. The signaling pathways (PKA, CaMKs, and MAPKs) which have been shown to link group I mGluRs to gene transcription, the relevant transcription factors (CREB and NF-κB), and target proteins (FMRP and ARC) will be documented. The significance and future direction for characterizing group I mGluR-mediated gene transcription in fragile X syndrome, schizophrenia, drug addiction, and other neurological disorders will also be discussed. PMID:23125836

  13. Classical Conditioning of the Rabbit Eyelid Response Increases Glutamate Receptor Binding in Hippocampal Synaptic Membranes

    NASA Astrophysics Data System (ADS)

    Mamounas, Laura A.; Thompson, Richard F.; Lynch, Gary; Baudry, Michel

    1984-04-01

    Hippocampal pyramidal neurons exhibit a rapid within-trial increase in firing frequency during classical conditioning of the rabbit eyelid response. It has been proposed that the cellular mechanisms responsible for hippocampal long-term potentiation (LTP) may also mediate this learning-dependent increase in neuronal activity. The induction of LTP in rat hippocampal slices results in an increase in the number of [3H]glutamate-binding sites in the potentiated region. The present study investigates the kinetics of [3H]glutamate binding to hippocampal synaptic membranes after eyelid conditioning in the rabbit. We report that the regional distribution of [3H]glutamate binding across the layers of rabbit hippocampus is compatible with a dendritic localization. The pharmacological and ionic properties of the binding suggest that it is associated with an excitatory amino acid receptor. After eyelid conditioning, the maximal number of hippocampal [3H]glutamate-binding sites is increased in animals receiving paired presentations of the tone conditioned stimulus and corneal air-puff unconditioned stimulus relative to that found in naive or unpaired control animals. These results strengthen the hypothesis that an LTP-like mechanism underlies the increase in hippocampal firing frequency during rabbit eyelid conditioning.

  14. Role of synaptic and nonsynaptic glutamate receptors in ischaemia induced neurotoxicity.

    PubMed

    Brassai, A; Suvanjeiev, R-G; Bán, E-Gy; Lakatos, M

    2015-03-01

    In acute ischaemic brain injury and chronic neurodegeneration, the first step leading to excitotoxicity and cell death is the excessive release of Glu and the prolonged activation of Glu receptors, followed by intracellular calcium overload. There is apparent agreement that glutamatergic transmission via synaptic NMDA receptors (composed of GluN2A subunits) is neuroprotective, whereas transmission via non-synaptic NMDA receptors (composed of GluN2B subunits) is excitotoxic. Extrasynaptic NMDARs activate cell death pathways and may play a key role in Glu-induced excitotoxic neurodegeneration and apoptosis. Accordingly, the function of protective pathways may be impaired by the concomitant blockade of GluN2A-containing receptors. In contrast, the selective inhibition of non-synaptic GluN2B-containing NMDARs may be beneficial in neuroprotection because it can prevent neuronal cell death and thus maintain protective pathways. PMID:25540918

  15. CPG2 Recruits Endophilin B2 to the Cytoskeleton for Activity-Dependent Endocytosis of Synaptic Glutamate Receptors.

    PubMed

    Loebrich, Sven; Benoit, Marc Robert; Konopka, Jaclyn Aleksandra; Cottrell, Jeffrey Richard; Gibson, Joanne; Nedivi, Elly

    2016-02-01

    Internalization of glutamate receptors at the postsynaptic membrane via clathrin-mediated endocytosis (CME) is a key mechanism for regulating synaptic strength. A role for the F-actin cytoskeleton in CME is well established, and recently, PKA-dependent association of candidate plasticity gene 2 (CPG2) with the spine-cytoskeleton has been shown to mediate synaptic glutamate receptor internalization. Yet, how the endocytic machinery is physically coupled to the actin cytoskeleton to facilitate glutamate receptor internalization has not been demonstrated. Moreover, there has been no distinction of endocytic-machinery components that are specific to activity-dependent versus constitutive glutamate receptor internalization. Here, we show that CPG2, through a direct physical interaction, recruits endophilin B2 (EndoB2) to F-actin, thus anchoring the endocytic machinery to the spine cytoskeleton and facilitating glutamate receptor internalization. Regulation of CPG2 binding to the actin cytoskeleton by protein kinase A directly impacts recruitment of EndoB2 and clathrin. Specific disruption of EndoB2 or the CPG2-EndoB2 interaction impairs activity-dependent, but not constitutive, internalization of both NMDA- and AMPA-type glutamate receptors. These results demonstrate that, through direct interactions with F-actin and EndoB2, CPG2 physically bridges the spine cytoskeleton and the endocytic machinery, and this tripartite association is critical specifically for activity-dependent CME of synaptic glutamate receptors. PMID:26776730

  16. Synaptic function is modulated by LRRK2 and glutamate release is increased in cortical neurons of G2019S LRRK2 knock-in mice

    PubMed Central

    Beccano-Kelly, Dayne A.; Kuhlmann, Naila; Tatarnikov, Igor; Volta, Mattia; Munsie, Lise N.; Chou, Patrick; Cao, Li-Ping; Han, Heather; Tapia, Lucia; Farrer, Matthew J.; Milnerwood, Austen J.

    2014-01-01

    Mutations in Leucine-Rich Repeat Kinase-2 (LRRK2) result in familial Parkinson's disease and the G2019S mutation alone accounts for up to 30% in some ethnicities. Despite this, the function of LRRK2 is largely undetermined although evidence suggests roles in phosphorylation, protein interactions, autophagy and endocytosis. Emerging reports link loss of LRRK2 to altered synaptic transmission, but the effects of the G2019S mutation upon synaptic release in mammalian neurons are unknown. To assess wild type and mutant LRRK2 in established neuronal networks, we conducted immunocytochemical, electrophysiological and biochemical characterization of >3 week old cortical cultures of LRRK2 knock-out, wild-type overexpressing and G2019S knock-in mice. Synaptic release and synapse numbers were grossly normal in LRRK2 knock-out cells, but discretely reduced glutamatergic activity and reduced synaptic protein levels were observed. Conversely, synapse density was modestly but significantly increased in wild-type LRRK2 overexpressing cultures although event frequency was not. In knock-in cultures, glutamate release was markedly elevated, in the absence of any change to synapse density, indicating that physiological levels of G2019S LRRK2 elevate probability of release. Several pre-synaptic regulatory proteins shown by others to interact with LRRK2 were expressed at normal levels in knock-in cultures; however, synapsin 1 phosphorylation was significantly reduced. Thus, perturbations to the pre-synaptic release machinery and elevated synaptic transmission are early neuronal effects of LRRK2 G2019S. Furthermore, the comparison of knock-in and overexpressing cultures suggests that one copy of the G2019S mutation has a more pronounced effect than an ~3-fold increase in LRRK2 protein. Mutant-induced increases in transmission may convey additional stressors to neuronal physiology that may eventually contribute to the pathogenesis of Parkinson's disease. PMID:25309331

  17. proBDNF negatively regulates neuronal remodeling, synaptic transmission, and synaptic plasticity in hippocampus.

    PubMed

    Yang, Jianmin; Harte-Hargrove, Lauren C; Siao, Chia-Jen; Marinic, Tina; Clarke, Roshelle; Ma, Qian; Jing, Deqiang; Lafrancois, John J; Bath, Kevin G; Mark, Willie; Ballon, Douglas; Lee, Francis S; Scharfman, Helen E; Hempstead, Barbara L

    2014-05-01

    Experience-dependent plasticity shapes postnatal development of neural circuits, but the mechanisms that refine dendritic arbors, remodel spines, and impair synaptic activity are poorly understood. Mature brain-derived neurotrophic factor (BDNF) modulates neuronal morphology and synaptic plasticity, including long-term potentiation (LTP) via TrkB activation. BDNF is initially translated as proBDNF, which binds p75(NTR). In vitro, recombinant proBDNF modulates neuronal structure and alters hippocampal long-term plasticity, but the actions of endogenously expressed proBDNF are unclear. Therefore, we generated a cleavage-resistant probdnf knockin mouse. Our results demonstrate that proBDNF negatively regulates hippocampal dendritic complexity and spine density through p75(NTR). Hippocampal slices from probdnf mice exhibit depressed synaptic transmission, impaired LTP, and enhanced long-term depression (LTD) in area CA1. These results suggest that proBDNF acts in vivo as a biologically active factor that regulates hippocampal structure, synaptic transmission, and plasticity, effects that are distinct from those of mature BDNF. PMID:24746813

  18. Glutamate-induced long-term potentiation of the frequency of miniature synaptic currents in cultured hippocampal neurons

    NASA Astrophysics Data System (ADS)

    Malgaroli, Antonio; Tsien, Richard W.

    1992-05-01

    Glutamate application at synapses between hippocampal neurons in culture produces long-term potentiation of the frequency of spontaneous miniature synaptic currents, together with long-term potentiation of evoked synaptic currents. The mini frequency potentiation is initiated postsynaptically and requires activity of NMDA receptors. Although the frequency of unitary quanta! responses increases strongly, their amplitude remains little changed with potentiation. Tests of postsynaptic responsiveness rule out recruitment of latent glutamate receptor clusters. Thus, postsynaptic induction can lead to enhancement of presynaptic transmitter release. The sustained potentiation of mini frequency is expressed even in the absence of Ca2+ entry into presynaptic terminals.

  19. Synaptic transmission deficits in Caenorhabditis elegans synaptobrevin mutants.

    PubMed

    Nonet, M L; Saifee, O; Zhao, H; Rand, J B; Wei, L

    1998-01-01

    Synaptobrevins are vesicle-associated proteins implicated in neurotransmitter release by both biochemical studies and perturbation experiments that use botulinum toxins. To test these models in vivo, we have isolated and characterized the first synaptobrevin mutants in metazoans and show that neurotransmission is severely disrupted in mutant animals. Mutants lacking snb-1 die just after completing embryogenesis. The dying animals retain some capability for movement, although they are extremely uncoordinated and incapable of feeding. We also have isolated and characterized several hypomorphic snb-1 mutants. Although fully viable, these mutants exhibit a variety of behavioral abnormalities that are consistent with a general defect in the efficacy of synaptic transmission. The viable mutants are resistant to the acetylcholinesterase inhibitor aldicarb, indicating that cholinergic transmission is impaired. Extracellular recordings from pharyngeal muscle also demonstrate severe defects in synaptic transmission in the mutants. The molecular lesions in the hypomorphic alleles reside on the hydrophobic face of a proposed amphipathic-helical region implicated biochemically in interacting with the t-SNAREs syntaxin and SNAP-25. Finally, we demonstrate that double mutants lacking both the v-SNAREs synaptotagmin and snb-1 are phenotypically similar to snb-1 mutants and less severe than syntaxin mutants. Our work demonstrates that synaptobrevin is essential for viability and is required for functional synaptic transmission. However, our analysis also suggests that transmitter release is not completely eliminated by removal of either one or both v-SNAREs. PMID:9412487

  20. A role for vesicular glutamate transporter 1 in synaptic vesicle clustering and mobility.

    PubMed

    Siksou, Léa; Silm, Kätlin; Biesemann, Christoph; Nehring, Ralf B; Wojcik, Sonja M; Triller, Antoine; El Mestikawy, Salah; Marty, Serge; Herzog, Etienne

    2013-05-01

    Synaptic vesicles (SVs) from excitatory synapses carry vesicular glutamate transporters (VGLUTs) that fill the vesicles with neurotransmitter. Although the essential function of VGLUTs as glutamate transporters has been well established, the evidence for additional cell-biological functions is more controversial. Both VGLUT1 and VGLUT2 disruptions in mice result in a reduced number of SVs away from release sites, flattening of SVs, and the appearance of tubular structures. Therefore, we analysed the morphology, biochemical composition and trafficking of SVs at synapses of VGLUT1(-/-) mice in order to test for a function of VGLUTs in the formation or clustering of SVs. Analyses with high-pressure freezing immobilisation and electron tomography pointed to a role of VGLUT1 transport function in the tonicity of excitatory SVs, explaining the aldehyde-induced flattening of SVs observed in VGLUT1(-/-) synapses. We confirmed the steep reduction in the number of SVs previously observed in VGLUT1(-/-) presynaptic terminals, but did not observe accumulation of endocytotic intermediates. Furthermore, SV proteins of adult VGLUT1(-/-) mouse brain tissue were expressed at normal levels in all subcellular fractions, suggesting that they were not displaced to another organelle. We thus assessed the mobility of the recently documented superpool of SVs. Synaptobrevin2-enhanced green fluorescent protein time lapse experiments revealed an oversized superpool of SVs in VGLUT1(-/-) neurons. Our results support the idea that, beyond glutamate loading, VGLUT1 enhances the tonicity of excitatory SVs and stabilises SVs at presynaptic terminals. PMID:23581566

  1. Immunohistochemical evidence for synaptic release of glutamate from orexin terminals in the locus coeruleus

    PubMed Central

    Henny, Pablo; Brischoux, Frédéric; Mainville, Lynda; Stroh, Thomas; Jones, Barbara E.

    2010-01-01

    Orexin (Orx or hypocretin) is critically important for maintaining wakefulness, since in its absence, narcolepsy with cataplexy occurs. In this role, Orx-containing neurons can exert their influence upon multiple targets through the brain by release of Orx but possibly also by release of other neurotransmitters. Indeed, evidence was previously presented to suggest that Orx terminals could utilize glutamate (Glu) in addition to Orx as a neurotransmitter. Using fluorescence and confocal laser scanning microscopy, we investigated whether Orx varicosities contain the presynaptic markers for synaptic release of Glu or GABA and come into contact with postsynaptic markers for excitatory synapses within the locus coeruleus of the rat brain. We found that a proportion of the Orx+ varicosities were immunostained for the vesicular transporter for Glu, VGluT2. None were immunostained for VGluT1 or VGluT3 or for the vesicular transporter for GABA, VGAT. Among the Orx+ varicosities, 4% of all and 28% of large varicosities contained VGluT2. A similar proportion of the large Orx+ varicosities contained synaptophysin, a presynaptic marker for synaptic vesicles. Orx+ varicosities also contacted elements immunostained for PSD-95, a postsynaptic marker for glutamatergic synapses. We thus conclude that synaptic release of Glu occurs from Orx terminals within the locus coeruleus and can thus be important for the engagement of noradrenergic neurons in stimulating and maintaining arousal. PMID:20540992

  2. Amyloid-β1-42 Disrupts Synaptic Plasticity by Altering Glutamate Recycling at the Synapse.

    PubMed

    Varga, Edina; Juhász, Gábor; Bozsó, Zsolt; Penke, Botond; Fülöp, Lívia; Szegedi, Viktor

    2015-01-01

    Alzheimer's disease (AD) is the most prevalent form of neurodegenerative disorders characterized by neuritic plaques containing amyloid-β peptide (Aβ) and neurofibrillary tangles. Evidence has been reported that Aβ(1-42) plays an essential pathogenic role in decreased spine density, impairment of synaptic plasticity, and neuronal loss with disruption of memory-related synapse function, all associated with AD. Experimentally, Aβ(1-42) oligomers perturb hippocampal long-term potentiation (LTP), an electrophysiological correlate of learning and memory. Aβ was also reported to perturb synaptic glutamate (Glu)-recycling by inhibiting excitatory-amino-acid-transporters. Elevated level of extracellular Glu leads to activation of perisynaptic receptors, including NR2B subunit containing NMDARs. These receptors were shown to induce impaired LTP and enhanced long-term depression and proapoptotic pathways, all central features of AD. In the present study, we investigated the role of Glu-recycling on Aβ(1-42)-induced LTP deficit in the CA1. We found that Aβ-induced LTP damage, which was mimicked by the Glu-reuptake inhibitor TBOA, could be rescued by blocking the NR2B subunit of NMDA receptors. Furthermore, decreasing the level of extracellular Glu using a Glu scavenger also restores TBOA or Aβ induces LTP damage. Overall, these results suggest that reducing ambient Glu in the brain can be protective against Aβ-induced synaptic disruption. PMID:25547631

  3. Solubilization, partial purification, and reconstitution of glutamate- and N-methyl-D-aspartate-activated cation channels from brain synaptic membranes

    SciTech Connect

    Ly, A.M.; Michaelis, E.K. )

    1991-04-30

    L-Glutamate-activated cation channel proteins from rat brain synaptic membranes were solubilized, partially purified, and reconstituted into liposomes. Optimal conditions for solubilization and reconstitution included treatment of the membranes with nonionic detergents in the presence of neutral phospholipids plus glycerol. Quench-flow procedures were developed to characterize the rapid kinetics of ion flux induced by receptor agonists. ({sup 14}C)Methylamine, a cation that permeates through the open channel of both vertebrate and invertebrate glutamate receptors, was used to measure the activity of glutamate receptor-ion channel complexes in reconstituted liposomes. L-Glutamate caused an increase in the rate of ({sup 14}C)methylamine influx into liposomes reconstituted with either solubilized membrane proteins or partially purified glutamate-binding proteins. Of the major glutamate receptor agonists, only N-methyl-D-aspartate activated cation fluxes in liposomes reconstituted with glutamate-binding proteins. In liposomes reconstituted with glutamate-binding proteins, N-methyl-D-aspartate- or glutamate-induced influx of NA{sup +} led to a transient increase in the influx of the lipid-permeable anion probe S{sup 14}CN{sup {minus}}. These results indicate the functional reconstitution of N-methyl-D-aspartate-sensitive glutamate receptors and the role of the {approximately}69-kDa protein in the function of these ion channels.

  4. MPTP-meditated hippocampal dopamine deprivation modulates synaptic transmission and activity-dependent synaptic plasticity

    SciTech Connect

    Zhu Guoqi; Chen Ying; Huang Yuying; Li Qinglin; Behnisch, Thomas

    2011-08-01

    Parkinson's disease (PD)-like symptoms including learning deficits are inducible by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Therefore, it is possible that MPTP may disturb hippocampal memory processing by modulation of dopamine (DA)- and activity-dependent synaptic plasticity. We demonstrate here that intraperitoneal (i.p.) MPTP injection reduces the number of tyrosine hydroxylase (TH)-positive neurons in the substantia nigra (SN) within 7 days. Subsequently, the TH expression level in SN and hippocampus and the amount of DA and its metabolite DOPAC in striatum and hippocampus decrease. DA depletion does not alter basal synaptic transmission and changes pair-pulse facilitation (PPF) of field excitatory postsynaptic potentials (fEPSPs) only at the 30 ms inter-pulse interval. In addition, the induction of long-term potentiation (LTP) is impaired whereas the duration of long-term depression (LTD) becomes prolonged. Since both LTP and LTD depend critically on activation of NMDA and DA receptors, we also tested the effect of DA depletion on NMDA receptor-mediated synaptic transmission. Seven days after MPTP injection, the NMDA receptor-mediated fEPSPs are decreased by about 23%. Blocking the NMDA receptor-mediated fEPSP does not mimic the MPTP-LTP. Only co-application of D1/D5 and NMDA receptor antagonists during tetanization resembled the time course of fEPSP potentiation as observed 7 days after i.p. MPTP injection. Together, our data demonstrate that MPTP-induced degeneration of DA neurons and the subsequent hippocampal DA depletion alter NMDA receptor-mediated synaptic transmission and activity-dependent synaptic plasticity. - Highlights: > I.p. MPTP-injection mediates death of dopaminergic neurons. > I.p. MPTP-injection depletes DA and DOPAC in striatum and hippocampus. > I.p. MPTP-injection does not alter basal synaptic transmission. > Reduction of LTP and enhancement of LTD after i.p. MPTP-injection. > Attenuation of NMDA-receptors mediated f

  5. Functional contributions of synaptically localized NR2B subunits of the NMDA receptor to synaptic transmission and long-term potentiation in the adult mouse CNS

    PubMed Central

    Miwa, Hideki; Fukaya, Masahiro; Watabe, Ayako M; Watanabe, Masahiko; Manabe, Toshiya

    2008-01-01

    The NMDA-type glutamate receptor is a heteromeric complex composed of the NR1 and at least one of the NR2 subunits. Switching from the NR2B to the NR2A subunit is thought to underlie functional alteration of the NMDA receptor during synaptic maturation, and it is generally believed that it results in preferential localization of NR2A subunits on the synaptic site and that of NR2B subunits on the extracellular site in the mature brain. It has also been proposed that activation of the NR2A and NR2B subunits results in long-term potentiation (LTP) and long-term depression (LTD), respectively. Furthermore, recent reports suggest that synaptic and extrasynaptic receptors may have distinct roles in synaptic plasticity as well as in gene expression associated with neuronal death. Here, we have investigated whether NR2B subunit-containing receptors are present and functional at mature synapses in the lateral nucleus of the amygdala (LA) and the CA1 region of the hippocampus, comparing their properties between the two brain regions. We have found, in contrast to the above hypotheses, that the NR2B subunit significantly contributes to synaptic transmission as well as LTP induction. Furthermore, its contribution is greater in the LA than in the CA1 region, and biophysical properties of NMDA receptors and the NR2B/NR2A ratio are different between the two brain regions. These results indicate that NR2B subunit-containing NMDA receptors accumulate on the synaptic site and are responsible for the unique properties of synaptic function and plasticity in the amygdala. PMID:18372311

  6. Presynaptic clathrin levels are a limiting factor for synaptic transmission.

    PubMed

    López-Murcia, Francisco J; Royle, Stephen J; Llobet, Artur

    2014-06-18

    To maintain communication, neurons must recycle their synaptic vesicles with high efficiency. This process places a huge burden on the clathrin-mediated endocytic machinery, but the consequences of this are poorly understood. We found that the amount of clathrin in a presynaptic terminal is not fixed. During stimulation, clathrin moves out of synapses as a function of stimulus strength and neurotransmitter release probability, which, together with membrane coat formation, transiently reduces the available pool of free clathrin triskelia. Correlative functional and morphological experiments in cholinergic autapses established by superior cervical ganglion neurons in culture show that presynaptic terminal function is compromised if clathrin levels fall by 20% after clathrin heavy chain knock down using RNAi. Synaptic transmission is depressed due to a reduction of cytoplasmic and readily releasable pools of vesicles. However, synaptic depression reverts after dialysis of exogenous clathrin, thus compensating RNAi-induced depletion. Lowering clathrin levels also reduces quantal size, which occurs concomitantly with a decrease in the size of synaptic vesicles. Large dense-core vesicles are unaffected by clathrin knock down. Together, our results show that clathrin levels are a dynamic property of presynaptic terminals that can influence short-term plasticity in a stimulus-dependent manner. PMID:24948816

  7. M-type potassium channels modulate Schaffer collateral-CA1 glutamatergic synaptic transmission.

    PubMed

    Sun, Jianli; Kapur, Jaideep

    2012-08-15

    Previous studies have suggested that muscarinic receptor activation modulates glutamatergic transmission. M-type potassium channels mediate the effects of muscarinic activation in the hippocampus, and it has been proposed that they modulate glutamatergic synaptic transmission. We tested whether M1 muscarinic receptor activation enhances glutamatergic synaptic transmission via the inhibition of the M-type potassium channels that are present in Schaffer collateral axons and terminals. Miniature excitatory postsynaptic currents (mEPSCs) were recorded from CA1 pyramidal neurons. The M1 receptor agonist, NcN-A-343, increased the frequency of mEPSCs, but did not alter their amplitude. The M-channel blocker XE991 and its analogue linopirdine also increased the frequency of mEPSCs. Flupirtine, which opens M-channels, had the opposite effect. XE991 did not enhance mEPSCs frequency in a calcium-free external medium. Blocking P/Q- and N-type calcium channels abolished the effect of XE991 on mEPSCs. These data suggested that the inhibition of M-channels increases presynaptic calcium-dependent glutamate release in CA1 pyramidal neurons. The effects of these agents on the membrane potentials of presynaptic CA3 pyramidal neurons were studied using current clamp recordings; activation of M1 receptors and blocking M-channels depolarized neurons and increased burst firing. The input resistance of CA3 neurons was increased by the application of McN-A-343 and XE991; these effects were consistent with the closure of M-channels. Muscarinic activation inhibits M-channels in CA3 pyramidal neurons and its efferents – Schaffer collateral, which causes the depolarization, activates voltage-gated calcium channels, and ultimately elevates the intracellular calcium concentration to increase the release of glutamate on CA1 pyramidal neurons. PMID:22674722

  8. Role of Spinophilin in Group I Metabotropic Glutamate Receptor Endocytosis, Signaling, and Synaptic Plasticity.

    PubMed

    Di Sebastiano, Andrea R; Fahim, Sandra; Dunn, Henry A; Walther, Cornelia; Ribeiro, Fabiola M; Cregan, Sean P; Angers, Stephane; Schmid, Susanne; Ferguson, Stephen S G

    2016-08-19

    Activation of Group I metabotropic glutamate receptors (mGluRs) activates signaling cascades, resulting in calcium release from intracellular stores, ERK1/2 activation, and long term changes in synaptic activity that are implicated in learning, memory, and neurodegenerative diseases. As such, elucidating the molecular mechanisms underlying Group I mGluR signaling is important for understanding physiological responses initiated by the activation of these receptors. In the current study, we identify the multifunctional scaffolding protein spinophilin as a novel Group I mGluR-interacting protein. We demonstrate that spinophilin interacts with the C-terminal tail and second intracellular loop of Group I mGluRs. Furthermore, we show that interaction of spinophilin with Group I mGluRs attenuates receptor endocytosis and phosphorylation of ERK1/2, an effect that is dependent upon the interaction of spinophilin with the C-terminal PDZ binding motif encoded by Group I mGluRs. Spinophilin knock-out results in enhanced mGluR5 endocytosis as well as increased ERK1/2, AKT, and Ca(2+) signaling in primary cortical neurons. In addition, the loss of spinophilin expression results in impaired mGluR5-stimulated LTD. Our results indicate that spinophilin plays an important role in regulating the activity of Group I mGluRs as well as their influence on synaptic activity. PMID:27358397

  9. Calmodulin activity regulates group I metabotropic glutamate receptor-mediated signal transduction and synaptic depression.

    PubMed

    Sethna, Ferzin; Zhang, Ming; Kaphzan, Hanoch; Klann, Eric; Autio, Dawn; Cox, Charles L; Wang, Hongbing

    2016-05-01

    Group I metabotropic glutamate receptors (mGluR), including mGluR1 and mGluR 5 (mGluR1/5), are coupled to Gq and modulate activity-dependent synaptic plasticity. Direct activation of mGluR1/5 causes protein translation-dependent long-term depression (LTD). Although it has been established that intracellular Ca(2+) and the Gq-regulated signaling molecules are required for mGluR1/5 LTD, whether and how Ca(2+) regulates Gq signaling and upregulation of protein expression remain unknown. Through pharmacological inhibition, we tested the function of the Ca(2+) sensor calmodulin (CaM) in intracellular signaling triggered by the activation of mGluR1/5. CaM inhibitor N-[4-aminobutyl]-5-chloro-2-naphthalenesulfonamide hydrochloride (W13) suppressed the mGluR1/5-stimulated activation of extracellular signal-regulated kinase 1/2 (ERK1/2) and p70-S6 kinase 1 (S6K1) in hippocampal neurons. W13 also blocked the mGluR1/5 agonist-induced synaptic depression in hippocampal slices and in anesthetized mice. Consistent with the function of CaM, inhibiting the downstream targets Ca(2+) /CaM-dependent protein kinases (CaMK) blocked ERK1/2 and S6K1 activation. Furthermore, disruption of the CaM-CaMK-ERK1/2 signaling cascade suppressed the mGluR1/5-stimulated upregulation of Arc expression. Altogether, our data suggest CaM as a new Gq signaling component for coupling Ca(2+) and protein upregulation and regulating mGluR1/5-mediated synaptic modification. PMID:26864654

  10. Relationship between Increase in Astrocytic GLT-1 Glutamate Transport and Late-LTP

    ERIC Educational Resources Information Center

    Pita-Almenar, Juan D.; Zou, Shengwei; Colbert, Costa M.; Eskin, Arnold

    2012-01-01

    Na[superscript +]-dependent high-affinity glutamate transporters have important roles in the maintenance of basal levels of glutamate and clearance of glutamate during synaptic transmission. Interestingly, several studies have shown that basal glutamate transport displays plasticity. Glutamate uptake increases in hippocampal slices during early…

  11. Cellular and molecular mechanisms of chemical synaptic transmission.

    PubMed

    Millhorn, D E; Bayliss, D A; Erickson, J T; Gallman, E A; Szymeczek, C L; Czyzyk-Krzeska, M; Dean, J B

    1989-12-01

    During the last decade much progress has been made in understanding the cellular and molecular mechanisms by which nerve cells communicate with each other and nonneural (e.g., muscle) target tissue. This review is intended to provide the reader with an account of this work. We begin with an historical overview of research on cell-to-cell communication and then discuss recent developments that, in some instances, have led to dramatic changes in the concept of synaptic transmission. For instance, the finding that single neurons often contain multiple messengers (i.e., neurotransmitters) invalidated the long-held theory (i.e., Dale's Law) that individual neurons contain and release one and only one type of neurotransmitter. Moreover, the last decade witnessed the inclusion of an entire group of compounds, the neuropeptides, as messenger molecules. Enormous progress has also been made in elucidating postsynaptic receptor complexes and biochemical intermediaries involved in synaptic transmission. Here the development of recombinant DNA technology has made it possible to clone and determine the molecular structure for a number of receptors. This information has been used to gain insight into how these receptors function either as a ligand-gated channel or as a G protein-linked ligand recognition molecule. Perhaps the most progress made during this era was in understanding the molecular linkage of G protein-linked receptors to intramembranous and cytoplasmic macromolecules involved in signal amplification and transduction. We conclude with a brief discussion of how synaptic transmission leads to immediate alterations in the electrical activity and, in some cases, to a change in phenotype by altering gene expression. These alterations in cellular behavior are believed to be mediated by phosphoproteins, the final biochemical product of signal transduction. PMID:2575357

  12. Glutamate Receptor Dynamics in Dendritic Microdomains

    PubMed Central

    Newpher, Thomas M.; Ehlers, Michael D.

    2008-01-01

    Among diverse factors regulating excitatory synaptic transmission, the abundance of postsynaptic glutamate receptors figures prominently in molecular memory and learning-related synaptic plasticity. To allow for both long-term maintenance of synaptic transmission and acute changes in synaptic strength, the relative rates of glutamate receptor insertion and removal must be tightly regulated. Interactions with scaffolding proteins control the targeting and signaling properties of glutamate receptors within the postsynaptic membrane. In addition, extrasynaptic receptor populations control the equilibrium of receptor exchange at synapses and activate distinct signaling pathways involved in plasticity. Here, we review recent findings that have shaped our current understanding of receptor mobility between synaptic and extrasynaptic compartments at glutamatergic synapses, focusing on AMPA and NMDA receptors. We also examine the cooperative relationship between intracellular trafficking and surface diffusion of glutamate receptors that underlies the expression of learning-related synaptic plasticity. PMID:18498731

  13. Quercetin Targets Cysteine String Protein (CSPα) and Impairs Synaptic Transmission

    PubMed Central

    Xu, Fenglian; Proft, Juliane; Gibbs, Sarah; Winkfein, Bob; Johnson, Jadah N.; Syed, Naweed; Braun, Janice E. A.

    2010-01-01

    Background Cysteine string protein (CSPα) is a synaptic vesicle protein that displays unique anti-neurodegenerative properties. CSPα is a member of the conserved J protein family, also called the Hsp40 (heat shock protein of 40 kDa) protein family, whose importance in protein folding has been recognized for many years. Deletion of the CSPα in mice results in knockout mice that are normal for the first 2–3 weeks of life followed by an unexplained presynaptic neurodegeneration and premature death. How CSPα prevents neurodegeneration is currently not known. As a neuroprotective synaptic vesicle protein, CSPα represents a promising therapeutic target for the prevention of neurodegenerative disorders. Methodology/Principal Findings Here, we demonstrate that the flavonoid quercetin promotes formation of stable CSPα-CSPα dimers and that quercetin-induced dimerization is dependent on the unique cysteine string region. Furthermore, in primary cultures of Lymnaea neurons, quercetin induction of CSPα dimers correlates with an inhibition of synapse formation and synaptic transmission suggesting that quercetin interfers with CSPα function. Quercetin's action on CSPα is concentration dependent and does not promote dimerization of other synaptic proteins or other J protein family members and reduces the assembly of CSPα:Hsc70 units (70kDa heat shock cognate protein). Conclusions/Significance Quercetin is a plant derived flavonoid and popular nutritional supplement proposed to prevent memory loss and altitude sickness among other ailments, although its precise mechanism(s) of action has been unclear. In view of the therapeutic promise of upregulation of CSPα and the undesired consequences of CSPα dysfunction, our data establish an essential proof of principle that pharmaceutical agents can selectively target the neuroprotective J protein CSPα. PMID:20548785

  14. Dynamic regulation of glycine–GABA co-transmission at spinal inhibitory synapses by neuronal glutamate transporter

    PubMed Central

    Ishibashi, Hitoshi; Yamaguchi, Junya; Nakahata, Yoshihisa; Nabekura, Junichi

    2013-01-01

    Fast inhibitory neurotransmission in the central nervous system is mediated by γ-aminobutyric acid (GABA) and glycine, which are accumulated into synaptic vesicles by a common vesicular inhibitory amino acid transporter (VIAAT) and are then co-released. However, the mechanisms that control the packaging of GABA + glycine into synaptic vesicles are not fully understood. In this study, we demonstrate the dynamic control of the GABA–glycine co-transmission by the neuronal glutamate transporter, using paired whole-cell patch recording from monosynaptically coupled cultured spinal cord neurons derived from VIAAT-Venus transgenic rats. Short step depolarization of presynaptic neurons evoked unitary (cell-to-cell) inhibitory postsynaptic currents (IPSCs). Under normal conditions, the fractional contribution of postsynaptic GABA or glycine receptors to the unitary IPSCs did not change during a 1 h recording. Intracellular loading of GABA or glycine via a patch pipette enhanced the respective components of inhibitory transmission, indicating the importance of the cytoplasmic concentration of inhibitory transmitters. Raised extracellular glutamate levels increased the amplitude of GABAergic IPSCs but reduced glycine release by enhancing glutamate uptake. Similar effects were observed when presynaptic neurons were intracellularly perfused with glutamate. Interestingly, high-frequency trains of stimulation decreased glycinergic IPSCs more than GABAergic IPSCs, and repetitive stimulation occasionally failed to evoke glycinergic but not GABAergic IPSCs. The present results suggest that the enhancement of GABA release by glutamate uptake may be advantageous for rapid vesicular refilling of the inhibitory transmitter at mixed GABA/glycinergic synapses and thus may help prevent hyperexcitability. PMID:23690564

  15. Porcupine controls hippocampal AMPAR levels, composition and synaptic transmission

    PubMed Central

    Erlenhardt, Nadine; Yu, Hong; Abiraman, Kavitha; Yamasaki, Tokiwa; Wadiche, Jacques I.; Tomita, Susumu; Bredt, David S.

    2016-01-01

    SUMMARY AMPAR (AMPAR) complexes contain auxiliary subunits that modulate receptor trafficking and gating. In addition to the transmembrane AMPAR regulatory proteins (TARPs) and cornichons (CNIH-2/3), recent proteomic studies identified a diverse array of additional AMPAR-associated transmembrane and secreted partners. We systematically surveyed these and found that PORCN and ABHD6 increase GluA1 levels in transfected cells. Knockdown of PORCN in rat hippocampal neurons, which express it in high amounts, selectively reduces levels of all tested AMPAR complex components. Regulation of AMPARs is independent of PORCN’s membrane-associated O-acyl transferase activity. PORCN knockdown in hippocampal neurons decreases AMPAR currents and accelerates desensitization, and leads to depletion of TARP γ-8 from AMPAR complexes. Conditional PORCN knockout mice also exhibit specific changes in AMPAR expression and gating that reduce basal synaptic transmission, but leave long-term potentiation intact. These studies define additional roles for PORCN in controlling synaptic transmission by regulating the level and composition of hippocampal AMPAR complexes. PMID:26776514

  16. Modulation of GABA-mediated synaptic transmission by endogenous zinc in the immature rat hippocampus in vitro.

    PubMed Central

    Xie, X; Hider, R C; Smart, T G

    1994-01-01

    response to ionophoretically applied GABA was either unaffected or slightly enhanced by Zn2+. 7. Under conditions favouring the activation of non-NMDA receptors, excitatory synaptic transmission was unaffected by CP94 but was depressed by Zn2+. Responses to ionophoretically applied glutamate were not inhibited by Zn2+, indicating that Zn2+ affects excitatory synaptic transmission via a presynaptic mechanism. 8. We conclude that the naturally occurring large synaptic potentials in young CA3 neurones are apparently induced by endogenous Zn2+ which can promote or synchronize the release of GABA in the immature hippocampus. PMID:7965838

  17. Changes in Synaptic Transmission and Long-term Potentiation Induction as a Possible Mechanism for Learning Disability in an Animal Model of Multiple Sclerosis

    PubMed Central

    2016-01-01

    Purpose: Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system. It has been shown that memory deficits is common in patients with MS. Recent studies using experimental autoimmune encephalomyelitis (EAE) as an animal model of MS have shown that indicated that EAE causes hippocampal-dependent impairment in learning and memory. Thus far, there have been no in vivo electrophysiological reports describing synaptic transmission in EAE animals. The aim of the present work is to evaluate the synaptic changes in the CA1 region of the hippocampus of EAE rats. Methods: To evaluate changes in synaptic transmission in the CA1 region of the hippocampus of EAE rats, field excitatory postsynaptic potentials (fEPSPs) from the stratum radiatum of CA1 neurons, were recorded following Schaffer collateral stimulation. Results: The results showed that EAE causes deficits in synaptic transmission and long-term potentiation (LTP) in the hippocampus. In addition, paired-pulse index with a 120 msec interstimulus interval was decreased in the EAE group. These findings indicate that EAE might induce suppression in synaptic transmission and LTP by increasing the inhibitory effect of GABAB receptors on the glutamate-mediated EPSP. Conclusions: In conclusion, influence of inflammation-triggered mechanisms on synaptic transmission may explain the negative effect of EAE on learning abilities in rats. PMID:27032554

  18. First effects of rising amyloid-β in transgenic mouse brain: synaptic transmission and gene expression

    PubMed Central

    Cummings, Damian M.; Liu, Wenfei; Portelius, Erik; Bayram, Sevinç; Yasvoina, Marina; Ho, Sui-Hin; Smits, Hélène; Ali, Shabinah S.; Steinberg, Rivka; Pegasiou, Chrysia-Maria; James, Owain T.; Matarin, Mar; Richardson, Jill C.; Zetterberg, Henrik; Blennow, Kaj; Hardy, John A.; Salih, Dervis A.

    2015-01-01

    Detecting and treating Alzheimer’s disease, before cognitive deficits occur, has become the health challenge of our time. The earliest known event in Alzheimer’s disease is rising amyloid-β. Previous studies have suggested that effects on synaptic transmission may precede plaque deposition. Here we report how relative levels of different soluble amyloid-β peptides in hippocampus, preceding plaque deposition, relate to synaptic and genomic changes. Immunoprecipitation-mass spectrometry was used to measure the early rise of different amyloid-β peptides in a mouse model of increasing amyloid-β (‘TASTPM’, transgenic for familial Alzheimer’s disease genes APP/PSEN1). In the third postnatal week, several amyloid-β peptides were above the limit of detection, including amyloid-β40, amyloid-β38 and amyloid-β42 with an intensity ratio of 6:3:2, respectively. By 2 months amyloid-β levels had only increased by 50% and although the ratio of the different peptides remained constant, the first changes in synaptic currents, compared to wild-type mice could be detected with patch-clamp recordings. Between 2 and 4 months old, levels of amyloid-β40 rose by ∼7-fold, but amyloid-β42 rose by 25-fold, increasing the amyloid-β42:amyloid-β40 ratio to 1:1. Only at 4 months did plaque deposition become detectable and only in some mice; however, synaptic changes were evident in all hippocampal fields. These changes included increased glutamate release probability (P < 0.001, n = 7–9; consistent with the proposed physiological effect of amyloid-β) and loss of spontaneous action potential-mediated activity in the cornu ammonis 1 (CA1) and dentate gyrus regions of the hippocampus (P < 0.001, n = 7). Hence synaptic changes occur when the amyloid-β levels and amyloid-β42:amyloid-β40 ratio are still low compared to those necessary for plaque deposition. Genome-wide microarray analysis revealed changes in gene expression at 2–4 months including synaptic genes being

  19. First effects of rising amyloid-β in transgenic mouse brain: synaptic transmission and gene expression.

    PubMed

    Cummings, Damian M; Liu, Wenfei; Portelius, Erik; Bayram, Sevinç; Yasvoina, Marina; Ho, Sui-Hin; Smits, Hélène; Ali, Shabinah S; Steinberg, Rivka; Pegasiou, Chrysia-Maria; James, Owain T; Matarin, Mar; Richardson, Jill C; Zetterberg, Henrik; Blennow, Kaj; Hardy, John A; Salih, Dervis A; Edwards, Frances A

    2015-07-01

    Detecting and treating Alzheimer's disease, before cognitive deficits occur, has become the health challenge of our time. The earliest known event in Alzheimer's disease is rising amyloid-β. Previous studies have suggested that effects on synaptic transmission may precede plaque deposition. Here we report how relative levels of different soluble amyloid-β peptides in hippocampus, preceding plaque deposition, relate to synaptic and genomic changes. Immunoprecipitation-mass spectrometry was used to measure the early rise of different amyloid-β peptides in a mouse model of increasing amyloid-β ('TASTPM', transgenic for familial Alzheimer's disease genes APP/PSEN1). In the third postnatal week, several amyloid-β peptides were above the limit of detection, including amyloid-β40, amyloid-β38 and amyloid-β42 with an intensity ratio of 6:3:2, respectively. By 2 months amyloid-β levels had only increased by 50% and although the ratio of the different peptides remained constant, the first changes in synaptic currents, compared to wild-type mice could be detected with patch-clamp recordings. Between 2 and 4 months old, levels of amyloid-β40 rose by ∼7-fold, but amyloid-β42 rose by 25-fold, increasing the amyloid-β42:amyloid-β40 ratio to 1:1. Only at 4 months did plaque deposition become detectable and only in some mice; however, synaptic changes were evident in all hippocampal fields. These changes included increased glutamate release probability (P < 0.001, n = 7-9; consistent with the proposed physiological effect of amyloid-β) and loss of spontaneous action potential-mediated activity in the cornu ammonis 1 (CA1) and dentate gyrus regions of the hippocampus (P < 0.001, n = 7). Hence synaptic changes occur when the amyloid-β levels and amyloid-β42:amyloid-β40 ratio are still low compared to those necessary for plaque deposition. Genome-wide microarray analysis revealed changes in gene expression at 2-4 months including synaptic genes being strongly

  20. Chronic activation of CB2 cannabinoid receptors in the hippocampus increases excitatory synaptic transmission

    PubMed Central

    Kim, Jimok; Li, Yong

    2015-01-01

    The roles of CB1 cannabinoid receptors in regulating neuronal activity have been extensively characterized. Although early studies show that CB1 receptors are present in the nervous system and CB2 cannabinoid receptors are in the immune system, recent evidence indicates that CB2 receptors are also expressed in the brain. Activation or blockade of CB2 receptors in vivo induces neuropsychiatric effects, but the cellular mechanisms of CB2 receptor function are unclear. The aim of this study is to determine how activation of CB2 receptors present in the hippocampus regulates synaptic function. Here, we show that when organotypic cultures of rodent hippocampal slices were treated with a CB2 receptor agonist (JWH133 or GP1a) for 7–10 days, quantal glutamate release became more frequent and spine density was increased via extracellular signal-regulated kinases. Chronic intraperitoneal injection of JWH133 into mice also increased excitatory synaptic transmission. These effects were blocked by a CB2 receptor antagonist (SR144528) or absent from hippocampal slices of CB2 receptor knock-out mice. This study reveals a novel cellular function of CB2 cannabinoid receptors in the hippocampus and provides insights into how cannabinoid receptor subtypes diversify the roles of cannabinoids in the brain. PMID:25504573

  1. Statistical analysis of synaptic transmission: model discrimination and confidence limits.

    PubMed Central

    Stricker, C; Redman, S; Daley, D

    1994-01-01

    Procedures for discriminating between competing statistical models of synaptic transmission, and for providing confidence limits on the parameters of these models, have been developed. These procedures were tested against simulated data and were used to analyze the fluctuations in synaptic currents evoked in hippocampal neurones. All models were fitted to data using the Expectation-Maximization algorithm and a maximum likelihood criterion. Competing models were evaluated using the log-likelihood ratio (Wilks statistic). When the competing models were not nested, Monte Carlo sampling of the model used as the null hypothesis (H0) provided density functions against which H0 and the alternate model (H1) were tested. The statistic for the log-likelihood ratio was determined from the fit of H0 and H1 to these probability densities. This statistic was used to determine the significance level at which H0 could be rejected for the original data. When the competing models were nested, log-likelihood ratios and the chi 2 statistic were used to determine the confidence level for rejection. Once the model that provided the best statistical fit to the data was identified, many estimates for the model parameters were calculated by resampling the original data. Bootstrap techniques were then used to obtain the confidence limits of these parameters. PMID:7948672

  2. Synaptic connections of amacrine cells containing vesicular glutamate transporter 3 in baboon retinas

    PubMed Central

    MARSHAK, DAVID W.; CHUANG, ALICE Z.; DOLINO, DREW M.; JACOBY, ROY A.; LIU, WEILEY S.; LONG, YE; SHERMAN, MICHAEL B.; SUH, JAE M.; VILA, ALEJANDRO; MILLS, STEPHEN L.

    2016-01-01

    The goals of these experiments were to describe the morphology and synaptic connections of amacrine cells in the baboon retina that contain immunoreactive vesicular glutamate transporter 3 (vGluT3). These amacrine cells had the morphology characteristic of knotty bistratified type 1 cells, and their dendrites formed two plexuses on either side of the center of the inner plexiform layer. The primary dendrites received large synapses from amacrine cells, and the higher-order dendrites were both pre- and postsynaptic to other amacrine cells. Based on light microscopic immunolabeling results, these include AII cells and starburst cells, but not the polyaxonal amacrine cells tracer-coupled to ON parasol ganglion cells. The vGluT3 cells received input from ON bipolar cells at ribbon synapses and made synapses onto OFF bipolar cells, including the diffuse DB3a type. Many synapses from vGluT3 cells onto retinal ganglion cells were observed in both plexuses. At synapses where vGluT3 cells were presynaptic, two types of postsynaptic densities were observed; there were relatively thin ones characteristic of inhibitory synapses and relatively thick ones characteristic of excitatory synapses. In the light microscopic experiments with Neurobiotin-injected ganglion cells, vGluT3 cells made contacts with midget and parasol ganglion cells, including both ON and OFF types. Puncta containing immunoreactive gephyrin, an inhibitory synapse marker, were found at appositions between vGluT3 cells and each of the four types of labeled ganglion cells. The vGluT3 cells did not have detectable levels of immunoreactive γ-aminobutyric acid (GABA) or immunoreactive glycine transporter 1. Thus, the vGluT3 cells would be expected to have ON responses to light and make synapses onto neurons in both the ON and the OFF pathways. Taken with previous results, these findings suggest that vGluT3 cells release glycine at some of their output synapses and glutamate at others. PMID:26241195

  3. Overexpression of Swedish mutant APP in aged astrocytes attenuates excitatory synaptic transmission.

    PubMed

    Katsurabayashi, Shutaro; Kawano, Hiroyuki; Ii, Miyuki; Nakano, Sachiko; Tatsumi, Chihiro; Kubota, Kaori; Takasaki, Kotaro; Mishima, Kenichi; Fujiwara, Michihiro; Iwasaki, Katsunori

    2016-01-01

    Amyloid precursor protein (APP), a type I transmembrane protein, has different aspects, namely, performs essential physiological functions and produces β-amyloid peptide (Aβ). Overexpression of neuronal APP is responsible for synaptic dysfunction. In the central nervous system, astrocytes - a major glial cell type - have an important role in the regulation of synaptic transmission. Although APP is expressed in astrocytes, it remains unclear whether astrocytic overexpression of mutant APP affects synaptic transmission. In this study, the effect of astrocytic overexpression of a mutant APP on the excitatory synaptic transmission was investigated using coculture system of the transgenic (Tg) cortical astrocytes that express the human APP695 polypeptide with the double mutation K670N + M671L found in a large Swedish family with early onset Alzheimer's disease, and wild-type hippocampal neuron. Significant secretion of Aβ 1-40 and 1-42 was observed in cultured cortical astrocytes from the Tg2576 transgenic mouse that genetically overexpresses Swedish mutant APP. Under the condition, Tg astrocytes did not affect excitatory synaptic transmission of cocultured wild-type neurons. However, aged Tg astrocytes cultured for 9 weeks elicited a significant decrease in excitatory synaptic transmission in cocultured neurons. Moreover, a reduction in the number of readily releasable synaptic vesicles accompanied a decrease in the number of excitatory synapses in neurons cocultured with aged Tg astrocytes. These observations indicate that astrocytic expression of the mutant APP is involved in the downregulation of synaptic transmission with age. PMID:26733247

  4. ANKS1B Gene Product AIDA-1 Controls Hippocampal Synaptic Transmission by Regulating GluN2B Subunit Localization

    PubMed Central

    Tindi, Jaafar O.; Chávez, Andrés E.; Cvejic, Svetlana; Calvo-Ochoa, Erika; Castillo, Pablo E.

    2015-01-01

    NMDA receptors (NMDARs) are key mediators of glutamatergic transmission and synaptic plasticity, and their dysregulation has been linked to diverse neuropsychiatric and neurodegenerative disorders. While normal NMDAR function requires regulated expression and trafficking of its different subunits, the molecular mechanisms underlying these processes are not fully understood. Here we report that the amyloid precursor protein intracellular domain associated-1 protein (AIDA-1), which associates with NMDARs and is encoded by ANKS1B, a gene recently linked to schizophrenia, regulates synaptic NMDAR subunit composition. Forebrain-specific AIDA-1 conditional knock-out (cKO) mice exhibit reduced GluN2B-mediated and increased GluN2A-mediated synaptic transmission, and biochemical analyses show AIDA-1 cKO mice have low GluN2B and high GluN2A protein levels at isolated hippocampal synaptic junctions compared with controls. These results are corroborated by immunocytochemical and electrophysiological analyses in primary neuronal cultures following acute lentiviral shRNA-mediated knockdown of AIDA-1. Moreover, hippocampal NMDAR-dependent but not metabotropic glutamate receptor-dependent plasticity is impaired in AIDA-1 cKO mice, further supporting a role for AIDA-1 in synaptic NMDAR function. We also demonstrate that AIDA-1 preferentially associates with GluN2B and with the adaptor protein Ca2+/calmodulin-dependent serine protein kinase and kinesin KIF17, which regulate the transport of GluN2B-containing NMDARs from the endoplasmic reticulum (ER) to synapses. Consistent with this function, GluN2B accumulates in ER-enriched fractions in AIDA-1 cKO mice. These findings suggest that AIDA-1 regulates NMDAR subunit composition at synapses by facilitating transport of GluN2B from the ER to synapses, which is critical for NMDAR plasticity. Our work provides an explanation for how AIDA-1 dysfunction might contribute to neuropsychiatric conditions, such as schizophrenia. PMID:26085624

  5. Transgenic Expression of Glud1 (Glutamate Dehydrogenase 1) in Neurons: In Vivo Model of Enhanced Glutamate Release, Altered Synaptic Plasticity, and Selective Neuronal Vulnerability

    PubMed Central

    Bao, Xiaodong; Pal, Ranu; Hascup, Kevin N.; Wang, Yongfu; Wang, Wen-Tung; Xu, Wenhao; Hui, Dongwei; Agbas, Abdulbaki; Wang, Xinkun; Michaelis, Mary L.; Choi, In-Young; Belousov, Andrei B.; Gerhardt, Greg A.; Michaelis, Elias K.

    2010-01-01

    The effects of lifelong, moderate excess release of glutamate (Glu) in the CNS have not been previously characterized. We created a transgenic (Tg) mouse model of lifelong excess synaptic Glu release in the CNS by introducing the gene for glutamate dehydrogenase 1 (Glud1) under the control of the neuron-specific enolase promoter. Glud1 is, potentially, an important enzyme in the pathway of Glu synthesis in nerve terminals. Increased levels of GLUD protein and activity in CNS neurons of hemizygous Tg mice were associated with increases in the in vivo release of Glu after neuronal depolarization in striatum and in the frequency and amplitude of miniature EPSCs in the CA1 region of the hippocampus. Despite overexpression of Glud1 in all neurons of the CNS, the Tg mice suffered neuronal losses in select brain regions (e.g., the CA1 but not the CA3 region). In vulnerable regions, Tg mice had decreases in MAP2A labeling of dendrites and in synaptophysin labeling of presynaptic terminals; the decreases in neuronal numbers and dendrite and presynaptic terminal labeling increased with advancing age. In addition, the Tg mice exhibited decreases in long-term potentiation of synaptic activity and in spine density in dendrites of CA1 neurons. Behaviorally, the Tg mice were significantly more resistant than wild-type mice to induction and duration of anesthesia produced by anesthetics that suppress Glu neurotransmission. The Glud1 mouse might be a useful model for the effects of lifelong excess synaptic Glu release on CNS neurons and for age-associated neurodegenerative processes. PMID:19890003

  6. Synaptic transmission changes in fear memory circuits underlie key features of an animal model of schizophrenia.

    PubMed

    Pollard, Marie; Varin, Christophe; Hrupka, Brian; Pemberton, Darrel J; Steckler, Thomas; Shaban, Hamdy

    2012-02-01

    Non-competitive antagonists of the N-methyl-d-aspartate receptor (NMDA) such as phencyclidine (PCP) elicit schizophrenia-like symptoms in healthy individuals. Similarly, PCP dosing in rats produces typical behavioral phenotypes that mimic human schizophrenia symptoms. Although schizophrenic behavioral phenotypes of the PCP model have been extensively studied, the underlying alterations of intrinsic neuronal properties and synaptic transmission in relevant limbic brain microcircuits remain elusive. Acute brain slice electrophysiology and immunostaining of inhibitory neurons were used to identify neuronal circuit alterations of the amygdala and hippocampus associated with changes in extinction of fear learning in rats following PCP treatment. Subchronic PCP application led to impaired long-term potentiation (LTP) and marked increases in the ratio of NMDA to 2-amino-3(5-methyl-3-oxo-1,2-oxazol-4-yl)propionic acid (AMPA) receptor-mediated currents at lateral amygdala (LA) principal neurons without alterations in parvalbumin (PV) as well as non-PV, glutamic acid decarboxylase 67 (GAD 67) immunopositive neurons. In addition, LTP was impaired at the Schaffer collateral to CA1 hippocampal pathway coincident with a reduction in colocalized PV and GAD67 immunopositive neurons in the CA3 hippocampal area. These effects occurred without changes in spontaneous events or intrinsic membrane properties of principal cells in the LA. The impairment of LTP at both amygdalar and hippocampal microcircuits, which play a key role in processing relevant survival information such as fear and extinction memory concurred with a disruption of extinction learning of fear conditioned responses. Our results show that subchronic PCP administration in rats impairs synaptic functioning in the amygdala and hippocampus as well as processing of fear-related memories. PMID:22085880

  7. A Myosin Va Mutant Mouse with Disruptions in Glutamate Synaptic Development and Mature Plasticity in Visual Cortex

    PubMed Central

    Yoshii, Akira; Zhao, Jianping; Pandian, Swarna; van Zundert, Brigitte; Constantine-Paton, Martha

    2013-01-01

    MyosinVa (MyoVa) mediates F-actin-based vesicular transport toward the plasma membrane and is found at neuronal postsynaptic densities (PSDs), but the role of MyoVa in synaptic development and function is largely unknown. Here, in studies using the dominant negative MyoVa neurological mutant mouse Flailer, we find that MyoVa plays an essential role in activity-dependent delivery of PSD-95 and other critical PSD molecules to synapses and in endocytosis of AMPA-type glutamate receptors (AMPAR) in the dendrites of CNS neurons. MyoVa is known to carry a complex containing the major scaffolding proteins of the mature PSD, PSD-95, SAPAP1/GKAP, Shank and Homer, to dendritic spine synapses. In Flailer, neurons show abnormal dendritic shaft localization of PSD-95, stargazin, dynamin3, AMPA glutamate receptors (AMPARs) and abnormal spine morphology. Flailer neurons also have abnormally high AMPAR miniature current frequencies and spontaneous AMPAR currents that are more frequent and larger than in WT while numbers of NMDAR containing synapses remain normal. The AMPAR abnormalities are consistent with a severely disrupted developmental regulation of long-term depression that we find in cortical Flailer neurons. Thus MyoVa plays a fundamentally important role both in localizing mature glutamate synapses to spines and in organizing the synapse for normal function. For this reason Flailer mice will be valuable in further dissecting the role of MyoVa in normal synaptic and circuit refinement and also in studies of neurological and neuropsychiatric diseases where disruptions of normal glutamate synapses are frequently observed. PMID:23658184

  8. Mutation of the Dyslexia-Associated Gene Dcdc2 Enhances Glutamatergic Synaptic Transmission Between Layer 4 Neurons in Mouse Neocortex.

    PubMed

    Che, Alicia; Truong, Dongnhu T; Fitch, R Holly; LoTurco, Joseph J

    2016-09-01

    Variants in DCDC2 have been associated with reading disability in humans, and targeted mutation of Dcdc2 in mice causes impairments in both learning and sensory processing. In this study, we sought to determine whether Dcdc2 mutation affects functional synaptic circuitry in neocortex. We found mutation in Dcdc2 resulted in elevated spontaneous and evoked glutamate release from neurons in somatosensory cortex. The probability of release was decreased to wild-type level by acute application of N-methyl-d-aspartate receptor (NMDAR) antagonists when postsynaptic NMDARs were blocked by intracellular MK-801, and could not be explained by elevated ambient glutamate, suggesting altered, nonpostsynaptic NMDAR activation in the mutants. In addition, we determined that the increased excitatory transmission was present at layer 4-layer 4 but not thalamocortical connections in Dcdc2 mutants, and larger evoked synaptic release appeared to enhance the NMDAR-mediated effect. These results demonstrate an NMDAR activation-gated, increased functional excitatory connectivity between layer 4 lateral connections in somatosensory neocortex of the mutants, providing support for potential changes in cortical connectivity and activation resulting from mutation of dyslexia candidate gene Dcdc2. PMID:26250775

  9. The quantal component of synaptic transmission from sensory hair cells to the vestibular calyx.

    PubMed

    Highstein, Stephen M; Mann, Mary Anne; Holstein, Gay R; Rabbitt, Richard D

    2015-06-01

    Spontaneous and stimulus-evoked excitatory postsynaptic currents (EPSCs) were recorded in calyx nerve terminals from the turtle vestibular lagena to quantify key attributes of quantal transmission at this synapse. On average, EPSC events had a magnitude of ∼ 42 pA, a rise time constant of τ(0) ∼ 229 μs, decayed to baseline with a time constant of τ(R) ∼ 690 μs, and carried ∼ 46 fC of charge. Individual EPSCs varied in magnitude and decay time constant. Variability in the EPSC decay time constant was hair cell dependent and due in part to a slow protraction of the EPSC in some cases. Variability in EPSC size was well described by an integer summation of unitary quanta, with each quanta of glutamate gating a unitary postsynaptic current of ∼ 23 pA. The unitary charge was ∼ 26 fC for EPSCs with a simple exponential decay and increased to ∼ 48 fC for EPSCs exhibiting a slow protraction. The EPSC magnitude and the number of simultaneous unitary quanta within each event increased with presynaptic stimulus intensity. During tonic hair cell depolarization, both the EPSC magnitude and event rate exhibited adaptive run down over time. Present data from a reptilian calyx are remarkably similar to noncalyceal vestibular synaptic terminals in diverse species, indicating that the skewed EPSC size distribution and multiquantal release might be an ancestral property of inner ear ribbon synapses. PMID:25878150

  10. The quantal component of synaptic transmission from sensory hair cells to the vestibular calyx

    PubMed Central

    Highstein, Stephen M.; Mann, Mary Anne; Holstein, Gay R.

    2015-01-01

    Spontaneous and stimulus-evoked excitatory postsynaptic currents (EPSCs) were recorded in calyx nerve terminals from the turtle vestibular lagena to quantify key attributes of quantal transmission at this synapse. On average, EPSC events had a magnitude of ∼42 pA, a rise time constant of τ0 ∼229 μs, decayed to baseline with a time constant of τR ∼690 μs, and carried ∼46 fC of charge. Individual EPSCs varied in magnitude and decay time constant. Variability in the EPSC decay time constant was hair cell dependent and due in part to a slow protraction of the EPSC in some cases. Variability in EPSC size was well described by an integer summation of unitary quanta, with each quanta of glutamate gating a unitary postsynaptic current of ∼23 pA. The unitary charge was ∼26 fC for EPSCs with a simple exponential decay and increased to ∼48 fC for EPSCs exhibiting a slow protraction. The EPSC magnitude and the number of simultaneous unitary quanta within each event increased with presynaptic stimulus intensity. During tonic hair cell depolarization, both the EPSC magnitude and event rate exhibited adaptive run down over time. Present data from a reptilian calyx are remarkably similar to noncalyceal vestibular synaptic terminals in diverse species, indicating that the skewed EPSC size distribution and multiquantal release might be an ancestral property of inner ear ribbon synapses. PMID:25878150

  11. Individual synaptic vesicles from the electroplaque of Torpedo californica, a classic cholinergic synapse, also contain transporters for glutamate and ATP

    PubMed Central

    Li, Huinan; Harlow, Mark L.

    2014-01-01

    Abstract The type of neurotransmitter secreted by a neuron is a product of the vesicular transporters present on its synaptic vesicle membranes and the available transmitters in the local cytosolic environment where the synaptic vesicles reside. Synaptic vesicles isolated from electroplaques of the marine ray, Torpedo californica, have served as model vesicles for cholinergic neurotransmission. Many lines of evidence support the idea that in addition to acetylcholine, additional neurotransmitters and/or neuromodulators are also released from cholinergic synapses. We identified the types of vesicular neurotransmitter transporters present at the electroplaque using immunoblot and immunofluoresence techniques with antibodies against the vesicle acetylcholine transporter (VAChT), the vesicular glutamate transporters (VGLUT1, 2, and 3), and the vesicular nucleotide transporter (VNUT). We found that VAChT, VNUT, VGLUT 1 and 2, but not 3 were present by immunoblot, and confirmed that the antibodies were specific to proteins of the axons and terminals of the electroplaque. We used a single‐vesicle imaging technique to determine whether these neurotransmitter transporters were present on the same or different populations of synaptic vesicles. We found that greater than 85% of vesicles that labeled for VAChT colabeled with VGLUT1 or VGLUT2, and approximately 70% colabeled with VNUT. Based upon confidence intervals, at least 52% of cholinergic vesicles isolated are likely to contain all four transporters. The presence of multiple types of neurotransmitter transporters – and potentially neurotransmitters – in individual synaptic vesicles raises fundamental questions about the role of cotransmitter release and neurotransmitter synergy at cholinergic synapses. PMID:24744885

  12. Synaptic transmission and the susceptibility of HIV infection to anti-viral drugs

    NASA Astrophysics Data System (ADS)

    Komarova, Natalia L.; Levy, David N.; Wodarz, Dominik

    2013-07-01

    Cell-to-cell viral transmission via virological synapses has been argued to reduce susceptibility of the virus population to anti-viral drugs through multiple infection of cells, contributing to low-level viral persistence during therapy. Using a mathematical framework, we examine the role of synaptic transmission in treatment susceptibility. A key factor is the relative probability of individual virions to infect a cell during free-virus and synaptic transmission, a currently unknown quantity. If this infection probability is higher for free-virus transmission, then treatment susceptibility is lowest if one virus is transferred per synapse, and multiple infection of cells increases susceptibility. In the opposite case, treatment susceptibility is minimized for an intermediate number of virions transferred per synapse. Hence, multiple infection via synapses does not simply lower treatment susceptibility. Without further experimental investigations, one cannot conclude that synaptic transmission provides an additional mechanism for the virus to persist at low levels during anti-viral therapy.

  13. Differential Roles of Postsynaptic Density-93 Isoforms in Regulating Synaptic Transmission

    PubMed Central

    Krüger, Juliane M.; Favaro, Plinio D.; Liu, Mingna; Kitlińska, Agata; Huang, Xiaojie; Raabe, Monika; Akad, Derya S.; Liu, Yanling; Urlaub, Henning; Dong, Yan; Xu, Weifeng

    2013-01-01

    In the postsynaptic density of glutamatergic synapses, the discs large (DLG)-membrane-associated guanylate kinase (MAGUK) family of scaffolding proteins coordinates a multiplicity of signaling pathways to maintain and regulate synaptic transmission. Postsynaptic density-93 (PSD-93) is the most variable paralog in this family; it exists in six different N-terminal isoforms. Probably because of the structural and functional variability of these isoforms, the synaptic role of PSD-93 remains controversial. To accurately characterize the synaptic role of PSD-93, we quantified the expression of all six isoforms in the mouse hippocampus and examined them individually in hippocampal synapses. Using molecular manipulations, including overexpression, gene knockdown, PSD-93 knock-out mice combined with biochemical assays, and slice electrophysiology both in rat and mice, we demonstrate that PSD-93 is required at different developmental synaptic states to maintain the strength of excitatory synaptic transmission. This strength is differentially regulated by the six isoforms of PSD-93, including regulations of α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor-active and inactive synapses, and activity-dependent modulations. Collectively, these results demonstrate that alternative combinations of N-terminal PSD-93 isoforms and DLG-MAGUK paralogs can fine-tune signaling scaffolds to adjust synaptic needs to regulate synaptic transmission. PMID:24068818

  14. A novel synaptic plasticity rule explains homeostasis of neuromuscular transmission

    PubMed Central

    Ouanounou, Gilles; Baux, Gérard; Bal, Thierry

    2016-01-01

    Excitability differs among muscle fibers and undergoes continuous changes during development and growth, yet the neuromuscular synapse maintains a remarkable fidelity of execution. Here we show in two evolutionarily distant vertebrates (Xenopus laevis cell culture and mouse nerve-muscle ex-vivo) that the skeletal muscle cell constantly senses, through two identified calcium signals, synaptic events and their efficacy in eliciting spikes. These sensors trigger retrograde signal(s) that control presynaptic neurotransmitter release, resulting in synaptic potentiation or depression. In the absence of spikes, synaptic events trigger potentiation. Once the synapse is sufficiently strong to initiate spiking, the occurrence of these spikes activates a negative retrograde feedback. These opposing signals dynamically balance the synapse in order to continuously adjust neurotransmitter release to a level matching current muscle cell excitability. DOI: http://dx.doi.org/10.7554/eLife.12190.001 PMID:27138195

  15. Salvia miltiorrhiza Bunge Blocks Ethanol-Induced Synaptic Dysfunction through Regulation of NMDA Receptor-Dependent Synaptic Transmission

    PubMed Central

    Park, Hye Jin; Lee, Seungheon; Jung, Ji Wook; Lee, Young Choon; Choi, Seong-Min; Kim, Dong Hyun

    2016-01-01

    Consumption of high doses of ethanol can lead to amnesia, which often manifests as a blackout. These blackouts experienced by ethanol consumers may be a major cause of the social problems associated with excess ethanol consumption. However, there is currently no established treatment for preventing these ethanol-induced blackouts. In this study, we tested the ethanol extract of the roots of Salvia miltiorrhiza (SM) for its ability to mitigate ethanol-induced behavioral and synaptic deficits. To test behavioral deficits, an object recognition test was conducted in mouse. In this test, ethanol (1 g/kg, i.p.) impaired object recognition memory, but SM (200 mg/kg) prevented this impairment. To evaluate synaptic deficits, NMDA receptor-mediated excitatory postsynaptic potential (EPSP) and long-term potentiation (LTP) in the mouse hippocampal slices were tested, as they are known to be vulnerable to ethanol and are associated with ethanol-induced amnesia. SM (10 and 100 μg/ml) significantly ameliorated ethanol-induced long-term potentiation and NMDA receptor-mediated EPSP deficits in the hippocampal slices. Therefore, these results suggest that SM prevents ethanol-induced amnesia by protecting the hippocampus from NMDA receptor-mediated synaptic transmission and synaptic plasticity deficits induced by ethanol. PMID:27257009

  16. Salvia miltiorrhiza Bunge Blocks Ethanol-Induced Synaptic Dysfunction through Regulation of NMDA Receptor-Dependent Synaptic Transmission.

    PubMed

    Park, Hye Jin; Lee, Seungheon; Jung, Ji Wook; Lee, Young Choon; Choi, Seong-Min; Kim, Dong Hyun

    2016-07-01

    Consumption of high doses of ethanol can lead to amnesia, which often manifests as a blackout. These blackouts experienced by ethanol consumers may be a major cause of the social problems associated with excess ethanol consumption. However, there is currently no established treatment for preventing these ethanol-induced blackouts. In this study, we tested the ethanol extract of the roots of Salvia miltiorrhiza (SM) for its ability to mitigate ethanol-induced behavioral and synaptic deficits. To test behavioral deficits, an object recognition test was conducted in mouse. In this test, ethanol (1 g/kg, i.p.) impaired object recognition memory, but SM (200 mg/kg) prevented this impairment. To evaluate synaptic deficits, NMDA receptor-mediated excitatory postsynaptic potential (EPSP) and long-term potentiation (LTP) in the mouse hippocampal slices were tested, as they are known to be vulnerable to ethanol and are associated with ethanol-induced amnesia. SM (10 and 100 μg/ml) significantly ameliorated ethanol-induced long-term potentiation and NMDA receptor-mediated EPSP deficits in the hippocampal slices. Therefore, these results suggest that SM prevents ethanol-induced amnesia by protecting the hippocampus from NMDA receptor-mediated synaptic transmission and synaptic plasticity deficits induced by ethanol. PMID:27257009

  17. High-Throughput All-Optical Analysis of Synaptic Transmission and Synaptic Vesicle Recycling in Caenorhabditis elegans

    PubMed Central

    Wabnig, Sebastian; Liewald, Jana Fiona; Yu, Szi-chieh; Gottschalk, Alexander

    2015-01-01

    Synaptic vesicles (SVs) undergo a cycle of biogenesis and membrane fusion to release transmitter, followed by recycling. How exocytosis and endocytosis are coupled is intensively investigated. We describe an all-optical method for identification of neurotransmission genes that can directly distinguish SV recycling factors in C. elegans, by motoneuron photostimulation and muscular RCaMP Ca2+ imaging. We verified our approach on mutants affecting synaptic transmission. Mutation of genes affecting SV recycling (unc-26 synaptojanin, unc-41 stonin, unc-57 endophilin, itsn-1 intersectin, snt-1 synaptotagmin) showed a distinct ‘signature’ of muscle Ca2+ dynamics, induced by cholinergic motoneuron photostimulation, i.e. faster rise, and earlier decrease of the signal, reflecting increased synaptic fatigue during ongoing photostimulation. To facilitate high throughput, we measured (3–5 times) ~1000 nematodes for each gene. We explored if this method enables RNAi screening for SV recycling genes. Previous screens for synaptic function genes, based on behavioral or pharmacological assays, allowed no distinction of the stage of the SV cycle in which a protein might act. We generated a strain enabling RNAi specifically only in cholinergic neurons, thus resulting in healthier animals and avoiding lethal phenotypes resulting from knockdown elsewhere. RNAi of control genes resulted in Ca2+ measurements that were consistent with results obtained in the respective genomic mutants, albeit to a weaker extent in most cases, and could further be confirmed by opto-electrophysiological measurements for mutants of some of the genes, including synaptojanin. We screened 95 genes that were previously implicated in cholinergic transmission, and several controls. We identified genes that clustered together with known SV recycling genes, exhibiting a similar signature of their Ca2+ dynamics. Five of these genes (C27B7.7, erp-1, inx-8, inx-10, spp-10) were further assessed in respective

  18. Wnt signaling pathway improves central inhibitory synaptic transmission in a mouse model of Duchenne muscular dystrophy.

    PubMed

    Fuenzalida, Marco; Espinoza, Claudia; Pérez, Miguel Ángel; Tapia-Rojas, Cheril; Cuitino, Loreto; Brandan, Enrique; Inestrosa, Nibaldo C

    2016-02-01

    The dystrophin-associated glycoprotein complex (DGC) that connects the cytoskeleton, plasma membrane and the extracellular matrix has been related to the maintenance and stabilization of channels and synaptic receptors, which are both essential for synaptogenesis and synaptic transmission. The dystrophin-deficient (mdx) mouse model of Duchenne muscular dystrophy (DMD) exhibits a significant reduction in hippocampal GABA efficacy, which may underlie the altered synaptic function and abnormal hippocampal long-term plasticity exhibited by mdx mice. Emerging studies have implicated Wnt signaling in the modulation of synaptic efficacy, neuronal plasticity and cognitive function. We report here that the activation of the non-canonical Wnt-5a pathway and Andrographolide, improves hippocampal mdx GABAergic efficacy by increasing the number of inhibitory synapses and GABA(A) receptors or GABA release. These results indicate that Wnt signaling modulates GABA synaptic efficacy and could be a promising novel target for DMD cognitive therapy. PMID:26626079

  19. Munc18-1 mutations that strongly impair SNARE-complex binding support normal synaptic transmission

    PubMed Central

    Meijer, Marieke; Burkhardt, Pawel; de Wit, Heidi; Toonen, Ruud F; Fasshauer, Dirk; Verhage, Matthijs

    2012-01-01

    Synaptic transmission depends critically on the Sec1p/Munc18 protein Munc18-1, but it is unclear whether Munc18-1 primarily operates as a integral part of the fusion machinery or has a more upstream role in fusion complex assembly. Here, we show that point mutations in Munc18-1 that interfere with binding to the free Syntaxin1a N-terminus and strongly impair binding to assembled SNARE complexes all support normal docking, priming and fusion of synaptic vesicles, and normal synaptic plasticity in munc18-1 null mutant neurons. These data support a prevailing role of Munc18-1 before/during SNARE-complex assembly, while its continued association to assembled SNARE complexes is dispensable for synaptic transmission. PMID:22446389

  20. Connexin 30 sets synaptic strength by controlling astroglial synapse invasion.

    PubMed

    Pannasch, Ulrike; Freche, Dominik; Dallérac, Glenn; Ghézali, Grégory; Escartin, Carole; Ezan, Pascal; Cohen-Salmon, Martine; Benchenane, Karim; Abudara, Veronica; Dufour, Amandine; Lübke, Joachim H R; Déglon, Nicole; Knott, Graham; Holcman, David; Rouach, Nathalie

    2014-04-01

    Astrocytes play active roles in brain physiology by dynamic interactions with neurons. Connexin 30, one of the two main astroglial gap-junction subunits, is thought to be involved in behavioral and basic cognitive processes. However, the underlying cellular and molecular mechanisms are unknown. We show here in mice that connexin 30 controls hippocampal excitatory synaptic transmission through modulation of astroglial glutamate transport, which directly alters synaptic glutamate levels. Unexpectedly, we found that connexin 30 regulated cell adhesion and migration and that connexin 30 modulation of glutamate transport, occurring independently of its channel function, was mediated by morphological changes controlling insertion of astroglial processes into synaptic clefts. By setting excitatory synaptic strength, connexin 30 plays an important role in long-term synaptic plasticity and in hippocampus-based contextual memory. Taken together, these results establish connexin 30 as a critical regulator of synaptic strength by controlling the synaptic location of astroglial processes. PMID:24584052

  1. Archaerhodopsin Selectively and Reversibly Silences Synaptic Transmission through Altered pH.

    PubMed

    El-Gaby, Mohamady; Zhang, Yu; Wolf, Konstantin; Schwiening, Christof J; Paulsen, Ole; Shipton, Olivia A

    2016-08-23

    Tools that allow acute and selective silencing of synaptic transmission in vivo would be invaluable for understanding the synaptic basis of specific behaviors. Here, we show that presynaptic expression of the proton pump archaerhodopsin enables robust, selective, and reversible optogenetic synaptic silencing with rapid onset and offset. Two-photon fluorescence imaging revealed that this effect is accompanied by a transient increase in pH restricted to archaerhodopsin-expressing boutons. Crucially, clamping intracellular pH abolished synaptic silencing without affecting the archaerhodopsin-mediated hyperpolarizing current, indicating that changes in pH mediate the synaptic silencing effect. To verify the utility of this technique, we used trial-limited, archaerhodopsin-mediated silencing to uncover a requirement for CA3-CA1 synapses whose afferents originate from the left CA3, but not those from the right CA3, for performance on a long-term memory task. These results highlight optogenetic, pH-mediated silencing of synaptic transmission as a spatiotemporally selective approach to dissecting synaptic function in behaving animals. PMID:27524609

  2. Age-Dependent Glutamate Induction of Synaptic Plasticity in Cultured Hippocampal Neurons

    ERIC Educational Resources Information Center

    Ivenshitz, Miriam; Segal, Menahem; Sapoznik, Stav

    2006-01-01

    A common denominator for the induction of morphological and functional plasticity in cultured hippocampal neurons involves the activation of excitatory synapses. We now demonstrate massive morphological plasticity in mature cultured hippocampal neurons caused by a brief exposure to glutamate. This plasticity involves a slow, 70%-80% increase in…

  3. Src, a Molecular Switch Governing Gain Control of Synaptic Transmission Mediated by N-methyl-D-Aspartate Receptors

    NASA Astrophysics Data System (ADS)

    Yu, Xian-Min; Salter, Michael W.

    1999-07-01

    The N-methyl-D-aspartate (NMDA) receptor is a principal subtype of glutamate receptor mediating fast excitatory transmission at synapses in the dorsal horn of the spinal cord and other regions of the central nervous system. NMDA receptors are crucial for the lasting enhancement of synaptic transmission that occurs both physiologically and in pathological conditions such as chronic pain. Over the past several years, evidence has accumulated indicating that the activity of NMDA receptors is regulated by the protein tyrosine kinase, Src. Recently it has been discovered that, by means of up-regulating NMDA receptor function, activation of Src mediates the induction of the lasting enhancement of excitatory transmission known as long-term potentiation in the CA1 region of the hippocampus. Also, Src has been found to amplify the up-regulation of NMDA receptor function that is produced by raising the intracellular concentration of sodium. Sodium concentration increases in neuronal dendrites during high levels of firing activity, which is precisely when Src becomes activated. Therefore, we propose that the boost in NMDA receptor function produced by the coincidence of activating Src and raising intracellular sodium may be important in physiological and pathophysiological enhancement of excitatory transmission in the dorsal horn of the spinal cord and elsewhere in the central nervous system.

  4. NMDA receptors activated by subventricular zone astrocytic glutamate are critical for neuroblast survival prior to entering a synaptic network

    PubMed Central

    Platel, Jean-Claude; Dave, Kathleen A.; Gordon, Valerie; Lacar, Benjamin; Rubio, Maria E.; Bordey, Angélique

    2010-01-01

    SUMMARY Even before integrating into existing circuitry, adult-born neurons express receptors for neurotransmitters, but the intercellular mechanisms and their impact on neurogenesis remain largely unexplored. Here, we show that neuroblasts born in the postnatal subventricular zone (SVZ) acquire NMDA receptors (NMDARs) during their migration to the olfactory bulb. Along their route, neuroblasts are ensheathed by astrocyte-like cells expressing vesicular glutamate release machinery. Increasing calcium in these specialized astrocytes induced NMDAR-activity in neuroblasts and blocking astrocytic vesicular release eliminated spontaneous NMDAR-activity. Single-cell knockout of NMDARs using neonatal electroporation resulted in neuroblast apoptosis at the time of NMDAR acquisition. This cumulated in a 40% loss of neuroblasts along their migratory route demonstrating that NMDAR acquisition is critical for neuroblast survival, prior to entering a synaptic network. In addition, our findings suggest an unexpected mechanism where SVZ astrocytes use glutamate signaling through NMDARs to control the number of adult-born neurons reaching their final destination. PMID:20346761

  5. Coordinated activation of distinct Ca(2+) sources and metabotropic glutamate receptors encodes Hebbian synaptic plasticity.

    PubMed

    Tigaret, Cezar M; Olivo, Valeria; Sadowski, Josef H L P; Ashby, Michael C; Mellor, Jack R

    2016-01-01

    At glutamatergic synapses, induction of associative synaptic plasticity requires time-correlated presynaptic and postsynaptic spikes to activate postsynaptic NMDA receptors (NMDARs). The magnitudes of the ensuing Ca2+ transients within dendritic spines are thought to determine the amplitude and direction of synaptic change. In contrast, we show that at mature hippocampal Schaffer collateral synapses the magnitudes of Ca2+ transients during plasticity induction do not match this rule. Indeed, LTP induced by time-correlated pre- and postsynaptic spikes instead requires the sequential activation of NMDARs followed by voltage-sensitive Ca2+ channels within dendritic spines. Furthermore, LTP requires inhibition of SK channels by mGluR1, which removes a negative feedback loop that constitutively regulates NMDARs. Therefore, rather than being controlled simply by the magnitude of the postsynaptic calcium rise, LTP induction requires the coordinated activation of distinct sources of Ca2+ and mGluR1-dependent facilitation of NMDAR function. PMID:26758963

  6. Coordinated activation of distinct Ca2+ sources and metabotropic glutamate receptors encodes Hebbian synaptic plasticity

    PubMed Central

    Tigaret, Cezar M.; Olivo, Valeria; Sadowski, Josef H.L.P.; Ashby, Michael C.; Mellor, Jack R.

    2016-01-01

    At glutamatergic synapses, induction of associative synaptic plasticity requires time-correlated presynaptic and postsynaptic spikes to activate postsynaptic NMDA receptors (NMDARs). The magnitudes of the ensuing Ca2+ transients within dendritic spines are thought to determine the amplitude and direction of synaptic change. In contrast, we show that at mature hippocampal Schaffer collateral synapses the magnitudes of Ca2+ transients during plasticity induction do not match this rule. Indeed, LTP induced by time-correlated pre- and postsynaptic spikes instead requires the sequential activation of NMDARs followed by voltage-sensitive Ca2+ channels within dendritic spines. Furthermore, LTP requires inhibition of SK channels by mGluR1, which removes a negative feedback loop that constitutively regulates NMDARs. Therefore, rather than being controlled simply by the magnitude of the postsynaptic calcium rise, LTP induction requires the coordinated activation of distinct sources of Ca2+ and mGluR1-dependent facilitation of NMDAR function. PMID:26758963

  7. Computational quest for understanding the role of astrocyte signaling in synaptic transmission and plasticity

    PubMed Central

    De Pittà, Maurizio; Volman, Vladislav; Berry, Hugues; Parpura, Vladimir; Volterra, Andrea; Ben-Jacob, Eshel

    2012-01-01

    The complexity of the signaling network that underlies astrocyte-synapse interactions may seem discouraging when tackled from a theoretical perspective. Computational modeling is challenged by the fact that many details remain hitherto unknown and conventional approaches to describe synaptic function are unsuitable to explain experimental observations when astrocytic signaling is taken into account. Supported by experimental evidence is the possibility that astrocytes perform genuine information processing by means of their calcium signaling and are players in the physiological setting of the basal tone of synaptic transmission. Here we consider the plausibility of this scenario from a theoretical perspective, focusing on the modulation of synaptic release probability by the astrocyte and its implications on synaptic plasticity. The analysis of the signaling pathways underlying such modulation refines our notion of tripartite synapse and has profound implications on our understanding of brain function. PMID:23267326

  8. Use-dependent inhibition of synaptic transmission by the secretion of intravesicularly accumulated antipsychotic drugs.

    PubMed

    Tischbirek, Carsten H; Wenzel, Eva M; Zheng, Fang; Huth, Tobias; Amato, Davide; Trapp, Stefan; Denker, Annette; Welzel, Oliver; Lueke, Katharina; Svetlitchny, Alexei; Rauh, Manfred; Deusser, Janina; Schwab, Annemarie; Rizzoli, Silvio O; Henkel, Andreas W; Müller, Christian P; Alzheimer, Christian; Kornhuber, Johannes; Groemer, Teja W

    2012-06-01

    Antipsychotic drugs are effective for the treatment of schizophrenia. However, the functional consequences and subcellular sites of their accumulation in nervous tissue have remained elusive. Here, we investigated the role of the weak-base antipsychotics haloperidol, chlorpromazine, clozapine, and risperidone in synaptic vesicle recycling. Using multiple live-cell microscopic approaches and electron microscopy of rat hippocampal neurons as well as in vivo microdialysis experiments in chronically treated rats, we demonstrate the accumulation of the antipsychotic drugs in synaptic vesicles and their release upon neuronal activity, leading to a significant increase in extracellular drug concentrations. The secreted drugs exerted an autoinhibitory effect on vesicular exocytosis, which was promoted by the inhibition of voltage-gated sodium channels and depended on the stimulation intensity. Taken together, these results indicate that accumulated antipsychotic drugs recycle with synaptic vesicles and have a use-dependent, autoinhibitory effect on synaptic transmission. PMID:22681688

  9. PSD-95 regulates synaptic transmission and plasticity in rat cerebral cortex

    PubMed Central

    Béïque, Jean-Claude; Andrade, Rodrigo

    2003-01-01

    PSD-95 is one of the most abundant proteins found in the postsynaptic density of excitatory synapses. However, the precise functional role played by PSD-95 in regulating synaptic transmission and plasticity remains undefined. To address this issue, we have overexpressed PSD-95 in cortical pyramidal neurons in organotypic brain slices using particle-mediated gene transfer and assessed the consequences on synaptic transmission and plasticity. The AMPA receptor/NMDA receptor (AMPAR/NMDAR) ratio of evoked EPSCs recorded at +40 mV was greater in PSD-95-transfected pyramidal neurons than in controls. This difference could not be accounted for by a change in rectification of AMPAR-mediated synaptic currents since the current-voltage curves obtained in controls and in PSD-95-transfected neurons were indistinguishable. However, the amplitude of AMPAR-mediated evoked EPSCs was larger in PSD-95-transfected neurons compared to matched controls. Paired-pulse ratio analysis suggested that overexpression of PSD-95 did not alter presynaptic release probability. Transfection of PSD-95 was further accompanied by an increase in the frequency, but not amplitude, of AMPAR-mediated mEPSCs. Together, these results indicate that transfection of PSD-95 increased AMPAR-mediated synaptic transmission. Furthermore, they suggest that this phenomenon reflects an increased number of synapses expressing AMPARs rather than an increased number or function of these receptors at individual synapses. We tested the consequences of these changes on synaptic plasticity and found that PSD-95 transfection greatly enhanced the probability of observing long-term depression. These results thus identify a physiological role for PSD-95 and demonstrate that this protein can play a decisive role in controlling synaptic strength and activity-dependent synaptic plasticity. PMID:12563010

  10. MicroRNAs in Schizophrenia: Implications for Synaptic Plasticity and Dopamine-Glutamate Interaction at the Postsynaptic Density. New Avenues for Antipsychotic Treatment Under a Theranostic Perspective.

    PubMed

    de Bartolomeis, Andrea; Iasevoli, Felice; Tomasetti, Carmine; Buonaguro, Elisabetta F

    2015-12-01

    Despite dopamine-glutamate aberrant interaction that has long been considered a relevant landmark of psychosis pathophysiology, several aspects of these two neurotransmitters reciprocal interaction remain to be defined. The emerging role of postsynaptic density (PSD) proteins at glutamate synapse as a molecular "lego" making a functional hub where different signals converge may add a new piece of information to understand how dopamine-glutamate interaction may work with regard to schizophrenia pathophysiology and treatment. More recently, compelling evidence suggests a relevant role for microRNA (miRNA) as a new class of dopamine and glutamate modulators with regulatory functions in the reciprocal interaction of these two neurotransmitters. Here, we aimed at addressing the following issues: (i) Do miRNAs have a role in schizophrenia pathophysiology in the context of dopamine-glutamate aberrant interaction? (ii) If miRNAs are relevant for dopamine-glutamate interaction, at what level this modulation takes place? (iii) Finally, will this knowledge open the door to innovative diagnostic and therapeutic tools? The biogenesis of miRNAs and their role in synaptic plasticity with relevance to schizophrenia will be considered in the context of dopamine-glutamate interaction, with special focus on miRNA interaction with PSD elements. From this framework, implications both for biomarkers identification and potential innovative interventions will be considered. PMID:25394379

  11. Cannabinoid 1 and transient receptor potential vanilloid 1 receptors discretely modulate evoked glutamate separately from spontaneous glutamate transmission.

    PubMed

    Fawley, Jessica A; Hofmann, Mackenzie E; Andresen, Michael C

    2014-06-11

    Action potentials trigger synaptic terminals to synchronously release vesicles, but some vesicles release spontaneously. G-protein-coupled receptors (GPCRs) can modulate both of these processes. At cranial primary afferent terminals, the GPCR cannabinoid 1 (CB1) is often coexpressed with transient receptor potential vanilloid 1 (TRPV1), a nonselective cation channel present on most afferents. Here we tested whether CB1 activation modulates synchronous, action potential-evoked (eEPSCs) and/or spontaneous (sEPSCs) EPSCs at solitary tract nucleus neurons. In rat horizontal brainstem slices, activation of solitary tract (ST) primary afferents generated ST-eEPSCs that were rapidly and reversibly inhibited from most afferents by activation of CB1 with arachidonyl-2'-chloroethylamide (ACEA) or WIN 55,212-2 [R-(+)-(2,3-dihydro-5-methyl-3-[(4-morpholinyl)methyl]pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl)(1-naphthalenyl) methanone monomethanesulfonate]. The CB1 antagonist/inverse agonist AM251 [N-1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-1-piperidinyl-1H-pyrazole-3-carboxamide] blocked these responses. Despite profound depression of ST-eEPSCs during CB1 activation, sEPSCs in these same neurons were unaltered. Changes in temperature changed sEPSC frequency only from TRPV1(+) afferents (i.e., thermal sEPSC responses only occurred in TRPV1(+) afferents). CB1 activation failed to alter these thermal sEPSC responses. However, the endogenous arachidonate metabolite N-arachidonyldopamine (NADA) promiscuously activated both CB1 and TRPV1 receptors. NADA inhibited ST-eEPSCs while simultaneously increasing sEPSC frequency, and thermally triggered sEPSC increases in neurons with TRPV1(+) afferents. We found no evidence for CB1/TRPV1 interactions suggesting independent regulation of two separate vesicle pools. Together, these data demonstrate that action potential-evoked synchronous glutamate release is modulated separately from TRPV1-mediated glutamate release despite coexistence

  12. Slow GABAA mediated synaptic transmission in rat visual cortex

    PubMed Central

    Sceniak, Michael P; MacIver, M Bruce

    2008-01-01

    Background Previous reports of inhibition in the neocortex suggest that inhibition is mediated predominantly through GABAA receptors exhibiting fast kinetics. Within the hippocampus, it has been shown that GABAA responses can take the form of either fast or slow response kinetics. Our findings indicate, for the first time, that the neocortex displays synaptic responses with slow GABAA receptor mediated inhibitory postsynaptic currents (IPSCs). These IPSCs are kinetically and pharmacologically similar to responses found in the hippocampus, although the anatomical specificity of evoked responses is unique from hippocampus. Spontaneous slow GABAA IPSCs were recorded from both pyramidal and inhibitory neurons in rat visual cortex. Results GABAA slow IPSCs were significantly different from fast responses with respect to rise times and decay time constants, but not amplitudes. Spontaneously occurring GABAA slow IPSCs were nearly 100 times less frequent than fast sIPSCs and both were completely abolished by the chloride channel blocker, picrotoxin. The GABAA subunit-specific antagonist, furosemide, depressed spontaneous and evoked GABAA fast IPSCs, but not slow GABAA-mediated IPSCs. Anatomical specificity was evident using minimal stimulation: IPSCs with slow kinetics were evoked predominantly through stimulation of layer 1/2 apical dendritic zones of layer 4 pyramidal neurons and across their basal dendrites, while GABAA fast IPSCs were evoked through stimulation throughout the dendritic arborization. Many evoked IPSCs were also composed of a combination of fast and slow IPSC components. Conclusion GABAA slow IPSCs displayed durations that were approximately 4 fold longer than typical GABAA fast IPSCs, but shorter than GABAB-mediated inhibition. The anatomical and pharmacological specificity of evoked slow IPSCs suggests a unique origin of synaptic input. Incorporating GABAA slow IPSCs into computational models of cortical function will help improve our understanding of

  13. Numb deficiency in cerebellar Purkinje cells impairs synaptic expression of metabotropic glutamate receptor and motor coordination.

    PubMed

    Zhou, Liang; Yang, Dong; Wang, De-Juan; Xie, Ya-Jun; Zhou, Jia-Huan; Zhou, Lin; Huang, Hao; Han, Shuo; Shao, Chong-Yu; Li, Hua-Shun; Zhu, J Julius; Qiu, Meng-Sheng; De Zeeuw, Chris I; Shen, Ying

    2015-12-15

    Protein Numb, first identified as a cell-fate determinant in Drosophila, has been shown to promote the development of neurites in mammals and to be cotransported with endocytic receptors in clathrin-coated vesicles in vitro. Nevertheless, its function in mature neurons has not yet been elucidated. Here we show that cerebellar Purkinje cells (PCs) express high levels of Numb during adulthood and that conditional deletion of Numb in PCs is sufficient to impair motor coordination despite maintenance of a normal cerebellar cyto-architecture. Numb proved to be critical for internalization and recycling of metabotropic glutamate 1 receptor (mGlu1) in PCs. A significant decrease of mGlu1 and an inhibition of long-term depression at the parallel fiber-PC synapse were observed in conditional Numb knockout mice. Indeed, the trafficking of mGlu1 induced by agonists was inhibited significantly in these mutants, but the expression of ionotropic glutamate receptor subunits and of mGlu1-associated proteins was not affected by the loss of Numb. Moreover, transient and persistent forms of mGlu1 plasticity were robustly induced in mutant PCs, suggesting that they do not require mGlu1 trafficking. Together, our data demonstrate that Numb is a regulator for constitutive expression and dynamic transport of mGlu1. PMID:26621723

  14. Purines released from astrocytes inhibit excitatory synaptic transmission in the ventral horn of the spinal cord

    PubMed Central

    Carlsen, Eva Meier; Perrier, Jean-François

    2014-01-01

    Spinal neuronal networks are essential for motor function. They are involved in the integration of sensory inputs and the generation of rhythmic motor outputs. They continuously adapt their activity to the internal state of the organism and to the environment. This plasticity can be provided by different neuromodulators. These substances are usually thought of being released by dedicated neurons. However, in other networks from the central nervous system synaptic transmission is also modulated by transmitters released from astrocytes. The star-shaped glial cell responds to neurotransmitters by releasing gliotransmitters, which in turn modulate synaptic transmission. Here we investigated if astrocytes present in the ventral horn of the spinal cord modulate synaptic transmission. We evoked synaptic inputs in ventral horn neurons recorded in a slice preparation from the spinal cord of neonatal mice. Neurons responded to electrical stimulation by monosynaptic EPSCs (excitatory monosynaptic postsynaptic currents). We used mice expressing the enhanced green fluorescent protein under the promoter of the glial fibrillary acidic protein to identify astrocytes. Chelating calcium with BAPTA in a single neighboring astrocyte increased the amplitude of synaptic currents. In contrast, when we selectively stimulated astrocytes by activating PAR-1 receptors with the peptide TFLLR, the amplitude of EPSCs evoked by a paired stimulation protocol was reduced. The paired-pulse ratio was increased, suggesting an inhibition occurring at the presynaptic side of synapses. In the presence of blockers for extracellular ectonucleotidases, TFLLR did not induce presynaptic inhibition. Puffing adenosine reproduced the effect of TFLLR and blocking adenosine A1 receptors with 8-Cyclopentyl-1,3-dipropylxanthine prevented it. Altogether our results show that ventral horn astrocytes are responsible for a tonic and a phasic inhibition of excitatory synaptic transmission by releasing ATP, which gets

  15. Postsynaptic mGluR5 promotes evoked AMPAR-mediated synaptic transmission onto neocortical layer 2/3 pyramidal neurons during development

    PubMed Central

    Loerwald, Kristofer W.; Patel, Ankur B.; Huber, Kimberly M.

    2014-01-01

    Both short- and long-term roles for the group I metabotropic glutamate receptor number 5 (mGluR5) have been examined for the regulation of cortical glutamatergic synapses. However, how mGluR5 sculpts neocortical networks during development still remains unclear. Using a single cell deletion strategy, we examined how mGluR5 regulates glutamatergic synaptic pathways in neocortical layer 2/3 (L2/3) during development. Electrophysiological measurements were made in acutely prepared slices to obtain a functional understanding of the effects stemming from loss of mGluR5 in vivo. Loss of postsynaptic mGluR5 results in an increase in the frequency of action potential-independent synaptic events but, paradoxically, results in a decrease in evoked transmission in two separate synaptic pathways providing input to the same pyramidal neurons. Synaptic transmission through α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, but not N-methyl-d-aspartate (NMDA) receptors, is specifically decreased. In the local L2/3 pathway, the decrease in evoked transmission appears to be largely due to a decrease in cell-to-cell connectivity and not in the strength of individual cell-to-cell connections. This decrease in evoked transmission correlates with a decrease in the total dendritic length in a region of the dendritic arbor that likely receives substantial input from these two pathways, thereby suggesting a morphological correlate to functional alterations. These changes are accompanied by an increase in intrinsic membrane excitability. Our data indicate that total mGluR5 function, incorporating both short- and long-term processes, promotes the strengthening of AMPA receptor-mediated transmission in multiple neocortical pathways. PMID:25392167

  16. MATERNAL HYPOTHYROXENEMIA LEADS TO PERSISTENT DEFICITS IN HIPPOCAMPAL SYNAPTIC TRANSMISSION AND LEARNING IN OFFSPRING.

    EPA Science Inventory

    MATERNAL HYPOTHYROXINEMIA LEADS TO PERSISTENT DEFICITS IN HIPPOCAMPAL SYNAPTIC TRANSMISSION AND LEARNING IN RAT OFFSPRING. M.E. Gilbert1 and Li Sui2, Neurotoxicology Division, 1US EPA and 2National Research Council, Research Triangle Pk, NC 27711.
    While severe hypothyroidis...

  17. The Chemokine MIP-1α/CCL3 impairs mouse hippocampal synaptic transmission, plasticity and memory

    PubMed Central

    Marciniak, Elodie; Faivre, Emilie; Dutar, Patrick; Alves Pires, Claire; Demeyer, Dominique; Caillierez, Raphaëlle; Laloux, Charlotte; Buée, Luc; Blum, David; Humez, Sandrine

    2015-01-01

    Chemokines are signaling molecules playing an important role in immune regulations. They are also thought to regulate brain development, neurogenesis and neuroendocrine functions. While chemokine upsurge has been associated with conditions characterized with cognitive impairments, their ability to modulate synaptic plasticity remains ill-defined. In the present study, we specifically evaluated the effects of MIP1-α/CCL3 towards hippocampal synaptic transmission, plasticity and spatial memory. We found that CCL3 (50 ng/ml) significantly reduced basal synaptic transmission at the Schaffer collateral-CA1 synapse without affecting NMDAR-mediated field potentials. This effect was ascribed to post-synaptic regulations, as CCL3 did not impact paired-pulse facilitation. While CCL3 did not modulate long-term depression (LTD), it significantly impaired long-term potentiation (LTP), an effect abolished by Maraviroc, a CCR5 specific antagonist. In addition, sub-chronic intracerebroventricular (icv) injections of CCL3 also impair LTP. In accordance with these electrophysiological findings, we demonstrated that the icv injection of CCL3 in mouse significantly impaired spatial memory abilities and long-term memory measured using the two-step Y-maze and passive avoidance tasks. These effects of CCL3 on memory were inhibited by Maraviroc. Altogether, these data suggest that the chemokine CCL3 is an hippocampal neuromodulator able to regulate synaptic plasticity mechanisms involved in learning and memory functions. PMID:26511387

  18. [EFFECT OF HYPOXIA ON SYNAPTIC TRANSMISSION BETWEEN RETINAL GANGLION CELLS AND SUPERIOR COLLICULUS NEURONS IN COCULTURE].

    PubMed

    Dumanska, G V; Rikhalsky, O V; Veselovsky, N S

    2015-01-01

    In this study we conducted a series of experiments to characterize the effect and define the mechanisms of hypoxia on synaptic transmission between retinal ganglion cells and superior colliculus (SC) neurons. Application of hypoxic solution leads to a long lasting potentiation (LTP) NMDA-mediated synaptic transmission. Analysis of the oxygen deficiency effect on the spontaneous and miniature postsynaptic currents (sPSC and mPSC respectively) revealed an increase in the frequency of their occurrence and the appearance of the second peak in the mPSC histogram distribution. The assessment of quantum and binomial parameters reflects the complex pre- and postsynaptic changes during the potentiation, independent of the release probability. Most likely this LTP can be caused by an increase in the total number of active synapses. Glutamatergic synaptic transmission mediated by non-NMDA activation receptor-channel complexes, responded to application of deoxygenated solution by the brief depression, which is the result of presynaptic dysfunction and associates with decrease in release probability and number of active zones. GABAergic synaptic transmission mediated by activation GABA(A)-receptor-channel complexes, responded to hypoxic action by long term depression (LTD). Analysis of sPSC and mPSC showed a significant decrease in the frequency of their occurrence and significant (P = 0.05) decrease in the quantum over a period of oxygen deficiency. In general, the effect of hypoxia-induced LTD of GABAergic synaptic transmission is based on complex changes of presynaptic (independent on the release probability) and postsynaptic (reduction sensitivity of receptors in postsynaptic membrane) mechanisms. PMID:27025053

  19. Enhanced synaptic transmission at the squid giant synapse by artificial seawater based on physically modified saline

    PubMed Central

    Choi, Soonwook; Yu, Eunah; Rabello, Guilherme; Merlo, Suelen; Zemmar, Ajmal; Walton, Kerry D.; Moreno, Herman; Moreira, Jorge E.; Sugimori, Mutsuyuki; Llinás, Rodolfo R.

    2014-01-01

    Superfusion of the squid giant synapse with artificial seawater (ASW) based on isotonic saline containing oxygen nanobubbles (RNS60 ASW) generates an enhancement of synaptic transmission. This was determined by examining the postsynaptic response to single and repetitive presynaptic spike activation, spontaneous transmitter release, and presynaptic voltage clamp studies. In the presence of RNS60 ASW single presynaptic stimulation elicited larger postsynaptic potentials (PSP) and more robust recovery from high frequency stimulation than in control ASW. Analysis of postsynaptic noise revealed an increase in spontaneous transmitter release with modified noise kinetics in RNS60 ASW. Presynaptic voltage clamp demonstrated an increased EPSP, without an increase in presynaptic ICa++ amplitude during RNS60 ASW superfusion. Synaptic release enhancement reached stable maxima within 5–10 min of RNS60 ASW superfusion and was maintained for the entire recording time, up to 1 h. Electronmicroscopic morphometry indicated a decrease in synaptic vesicle density and the number at active zones with an increase in the number of clathrin-coated vesicles (CCV) and large endosome-like vesicles near junctional sites. Block of mitochondrial ATP synthesis by presynaptic injection of oligomycin reduced spontaneous release and prevented the synaptic noise increase seen in RNS60 ASW. After ATP block the number of vesicles at the active zone and CCV was reduced, with an increase in large vesicles. The possibility that RNS60 ASW acts by increasing mitochondrial ATP synthesis was tested by direct determination of ATP levels in both presynaptic and postsynaptic structures. This was implemented using luciferin/luciferase photon emission, which demonstrated a marked increase in ATP synthesis following RNS60 administration. It is concluded that RNS60 positively modulates synaptic transmission by up-regulating ATP synthesis, thus leading to synaptic transmission enhancement. PMID:24575037

  20. Enhanced synaptic transmission at the squid giant synapse by artificial seawater based on physically modified saline.

    PubMed

    Choi, Soonwook; Yu, Eunah; Rabello, Guilherme; Merlo, Suelen; Zemmar, Ajmal; Walton, Kerry D; Moreno, Herman; Moreira, Jorge E; Sugimori, Mutsuyuki; Llinás, Rodolfo R

    2014-01-01

    Superfusion of the squid giant synapse with artificial seawater (ASW) based on isotonic saline containing oxygen nanobubbles (RNS60 ASW) generates an enhancement of synaptic transmission. This was determined by examining the postsynaptic response to single and repetitive presynaptic spike activation, spontaneous transmitter release, and presynaptic voltage clamp studies. In the presence of RNS60 ASW single presynaptic stimulation elicited larger postsynaptic potentials (PSP) and more robust recovery from high frequency stimulation than in control ASW. Analysis of postsynaptic noise revealed an increase in spontaneous transmitter release with modified noise kinetics in RNS60 ASW. Presynaptic voltage clamp demonstrated an increased EPSP, without an increase in presynaptic ICa(++) amplitude during RNS60 ASW superfusion. Synaptic release enhancement reached stable maxima within 5-10 min of RNS60 ASW superfusion and was maintained for the entire recording time, up to 1 h. Electronmicroscopic morphometry indicated a decrease in synaptic vesicle density and the number at active zones with an increase in the number of clathrin-coated vesicles (CCV) and large endosome-like vesicles near junctional sites. Block of mitochondrial ATP synthesis by presynaptic injection of oligomycin reduced spontaneous release and prevented the synaptic noise increase seen in RNS60 ASW. After ATP block the number of vesicles at the active zone and CCV was reduced, with an increase in large vesicles. The possibility that RNS60 ASW acts by increasing mitochondrial ATP synthesis was tested by direct determination of ATP levels in both presynaptic and postsynaptic structures. This was implemented using luciferin/luciferase photon emission, which demonstrated a marked increase in ATP synthesis following RNS60 administration. It is concluded that RNS60 positively modulates synaptic transmission by up-regulating ATP synthesis, thus leading to synaptic transmission enhancement. PMID:24575037

  1. Reactive oxygen species enhance excitatory synaptic transmission in rat spinal dorsal horn neurons by activating TRPA1 and TRPV1 channels.

    PubMed

    Nishio, N; Taniguchi, W; Sugimura, Y K; Takiguchi, N; Yamanaka, M; Kiyoyuki, Yasukuni; Yamada, H; Miyazaki, N; Yoshida, M; Nakatsuka, T

    2013-09-01

    Central neuropathic pain (CNP) in the spinal cord, such as chronic pain after spinal cord injury (SCI), is an incurable ailment. However, little is known about the spinal cord mechanisms underlying CNP. Recently, reactive oxygen species (ROS) have been recognized to play an important role in CNP of the spinal cord. However, it is unclear how ROS affect synaptic transmission in the dorsal horn of the spinal cord. To clarify how ROS impact on synaptic transmission, we investigated the effects of ROS on synaptic transmission in rat spinal cord substantia gelatinosa (SG) neurons using whole-cell patch-clamp recordings. Administration of tert-butyl hydroperoxide (t-BOOH), an ROS donor, into the spinal cord markedly increased the frequency and amplitude of spontaneous excitatory postsynaptic currents (sEPSCs) in SG neurons. This t-BOOH-induced enhancement was not suppressed by the Na(+) channel blocker tetrodotoxin. However, in the presence of a non-N-methyl-D-aspartate glutamate receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione, t-BOOH did not generate any sEPSCs. Furthermore, in the presence of a transient receptor potential ankyrin 1 (TRPA1) channel antagonist (HC-030031) or a transient receptor potential vanilloid 1 (TRPV1) channel antagonist (capsazepine or AMG9810), the t-BOOH-induced increase in the frequency of sEPSCs was inhibited. These results indicate that ROS enhance the spontaneous release of glutamate from presynaptic terminals onto SG neurons through TRPA1 and TRPV1 channel activation. Excessive activation of these ion channels by ROS may induce central sensitization in the spinal cord and result in chronic pain such as that following SCI. PMID:23707800

  2. Apolipoprotein E*4 (APOE*4) Genotype Is Associated with Altered Levels of Glutamate Signaling Proteins and Synaptic Coexpression Networks in the Prefrontal Cortex in Mild to Moderate Alzheimer Disease.

    PubMed

    Sweet, Robert A; MacDonald, Matthew L; Kirkwood, Caitlin M; Ding, Ying; Schempf, Tadhg; Jones-Laughner, Jackie; Kofler, Julia; Ikonomovic, Milos D; Lopez, Oscar L; Garver, Megan E; Fitz, Nicholas F; Koldamova, Radosveta; Yates, Nathan A

    2016-07-01

    It has been hypothesized that Alzheimer disease (AD) is primarily a disorder of the synapse. However, assessment of the synaptic proteome in AD subjects has been limited to a small number of proteins and often included subjects with end-stage pathology. Protein from prefrontal cortex gray matter of 59 AD subjects with mild to moderate dementia and 12 normal elderly subjects was assayed using targeted mass spectrometry to quantify 191 synaptically expressed proteins. The profile of synaptic protein expression clustered AD subjects into two groups. One of these was characterized by reduced expression of glutamate receptor proteins, significantly increased synaptic protein network coexpression, and associated withApolipoprotein E*4 (APOE*4) carrier status. The second group, by contrast, showed few differences from control subjects. A subset of AD subjects had altered prefrontal cortex synaptic proteostasis for glutamate receptors and their signaling partners. Efforts to therapeutically target glutamate receptors in AD may have outcomes dependent on APOE*4 genotype. PMID:27103636

  3. From synaptically localized to volume transmission by nitric oxide.

    PubMed

    Garthwaite, John

    2016-01-01

    Nitric oxide (NO) functions widely as a transmitter/diffusible second messenger in the central nervous system, exerting physiological effects in target cells by binding to specialized guanylyl cyclase-coupled receptors, resulting in cGMP generation. Despite having many context-dependent physiological roles and being implicated in numerous disease states, there has been a lack of clarity about the ways that NO operates at the cellular and subcellular levels. Recently, several approaches have been used to try to gain a more concrete, quantitative understanding of this unique signalling pathway. These approaches have included analysing the kinetics of NO receptor function, real-time imaging of cellular NO signal transduction in target cells, and the use of ultrasensitive detector cells to record NO as it is being generated from native sources in brain tissue. The current picture is that, when formed in a synapse, NO is likely to act only very locally, probably mostly within the confines of that synapse, and to exist only in picomolar concentrations. Nevertheless, closely neighbouring synapses may also be within reach, raising the possibility of synaptic crosstalk. By engaging its enzyme-coupled receptors, the low NO concentrations are able to stimulate physiological (submicromolar) increases in cGMP concentration in an activity-dependent manner. When many NO-emitting neurones or synapses are active simultaneously in a tissue region, NO can act more like a volume transmitter to influence, and perhaps coordinate, the behaviour of cells within that region, irrespective of their identity and anatomical connectivity. PMID:26486504

  4. Autism-associated mutations in ProSAP2/Shank3 impair synaptic transmission and neurexin-neuroligin-mediated transsynaptic signaling.

    PubMed

    Arons, Magali H; Thynne, Charlotte J; Grabrucker, Andreas M; Li, Dong; Schoen, Michael; Cheyne, Juliette E; Boeckers, Tobias M; Montgomery, Johanna M; Garner, Craig C

    2012-10-24

    Mutations in several postsynaptic proteins have recently been implicated in the molecular pathogenesis of autism and autism spectrum disorders (ASDs), including Neuroligins, Neurexins, and members of the ProSAP/Shank family, thereby suggesting that these genetic forms of autism may share common synaptic mechanisms. Initial studies of ASD-associated mutations in ProSAP2/Shank3 support a role for this protein in glutamate receptor function and spine morphology, but these synaptic phenotypes are not universally penetrant, indicating that other core facets of ProSAP2/Shank3 function must underlie synaptic deficits in patients with ASDs. In the present study, we have examined whether the ability of ProSAP2/Shank3 to interact with the cytoplasmic tail of Neuroligins functions to coordinate pre/postsynaptic signaling through the Neurexin-Neuroligin signaling complex in hippocampal neurons of Rattus norvegicus. Indeed, we find that synaptic levels of ProSAP2/Shank3 regulate AMPA and NMDA receptor-mediated synaptic transmission and induce widespread changes in the levels of presynaptic and postsynaptic proteins via Neurexin-Neuroligin transsynaptic signaling. ASD-associated mutations in ProSAP2/Shank3 disrupt not only postsynaptic AMPA and NMDA receptor signaling but also interfere with the ability of ProSAP2/Shank3 to signal across the synapse to alter presynaptic structure and function. These data indicate that ASD-associated mutations in a subset of synaptic proteins may target core cellular pathways that coordinate the functional matching and maturation of excitatory synapses in the CNS. PMID:23100419

  5. Effects of prostaglandin E2 on synaptic transmission in the rat spinal trigeminal subnucleus caudalis.

    PubMed

    Mizutani, Yuka; Ohi, Yoshiaki; Kimura, Satoko; Miyazawa, Ken; Goto, Shigemi; Haji, Akira

    2015-11-01

    The spinal trigeminal subnucleus caudalis (Vc) receives preferentially nociceptive afferent signals from the orofacial area. Nociceptive stimuli to the orofacial area induce cyclooxygenase both peripherally and centrally, which can synthesize a major prostanoid prostaglandin E2 (PGE2) that implicates in diverse physiological functions. To clarify the roles of centrally-synthesized PGE2 in nociception, effects of exogenous PGE2 on synaptic transmission in the Vc neurons were investigated in the rat brainstem slice. Spontaneously occurring excitatory and inhibitory postsynaptic currents (sEPSCs and sIPSCs) were recorded, respectively, under pharmacological blockade of inhibitory and excitatory transmission by whole-cell patch-clamp mode. Perfusion of PGE2 (1-5 μM) increased the frequency of sIPSCs in a concentration-dependent manner but had no significant effect on the amplitude. Similarly to the effects on sIPSCs, PGE2 increased the sEPSC frequency without any effect on the amplitude. These facilitatory effects of PGE2 on spontaneous synaptic transmissions were blocked by an EP1 antagonist SC19220 but not by an EP4 antagonist AH23848. Electrical stimulation of the trigeminal tract evoked short latency EPSCs (eEPSCs) in the Vc neurons. PGE2 (5 μM) was ineffective on the eEPSCs. The present study demonstrated that PGE2 facilitated spontaneous synaptic transmissions in the Vc neurons through activating the presynaptic EP1 receptors but had no effect on the trigeminal tract-mediated excitatory transmission. These results suggest that centrally-synthesized PGE2 modifies the synaptic transmission in the Vc region, thereby contributing to the processing of nociceptive signals originated from the orofacial area. PMID:26320551

  6. Calcium channel blockade attenuates abnormal synaptic transmission in the dentate gyrus elicited by entorhinal amyloidopathy.

    PubMed

    Gholami Pourbadie, Hamid; Naderi, Nima; Janahmadi, Mahyar; Mehranfard, Nasrin; Motamedi, Fereshteh

    2016-10-01

    Entorhinal-hippocampal network is one of the earliest circuits which is affected by Alzheimer's disease (AD). There are numerous data providing the evidence of synaptic deficit in the dentate gyrus (DG) of AD animal model. However, there is little known about how entorhinal cortex (EC) amyloidophaty affects each excitatory and/or inhibitory transmission in the early stage of AD. On the other hand, it is believed that calcium dyshomeostasis has a critical role in the etiology of AD. Here, the effect of the EC amyloid pathogenesis on excitatory or inhibitory post synaptic currents (EPSC and IPSC, respectively) in the DG granule cells and then the possible neuroprotective action of L-type calcium channel blockers (CCBs), nimodipine and isradipine, were examined. The amyloid beta (Aβ) 1-42 was injected bilaterally into the EC of male rats and one week later, synaptic currents in the DG granule cells were assessed by whole cell patch clamp. EPSCs were evoked by stimulating the perforant pathway. Voltage clamp recording showed profound decrease of evoked EPSC amplitude and paired pulse facilitation in the DG granule cells of Aβ treated rats. Furthermore, AMPA/NMDA ratio was significantly decreased in the Aβ treated animals. On the other hand, amplitude of IPSC currents was significantly increased in the DG granule cells of these animals. These modifications of synaptic currents were partially reversed by daily intracerebroventricular administration of isradipine or nimodipine. In conclusion, our results suggest that Aβ in the EC triggers decreased excitatory transmission in the DG with substantial decrement in AMPA currents, leading to a prominent activity of inhibitory circuits and increased inhibition of granule cells which may contribute to the development of AD-related neurological deficits in AD and treatment by CCBs could preserve normal synaptic transmission against Aβ toxicity. PMID:27240164

  7. Nitric oxide regulates synaptic transmission between spiny projection neurons

    PubMed Central

    Sagi, Yotam; Heiman, Myriam; Peterson, Jayms D.; Musatov, Sergei; Scarduzio, Mariangela; Logan, Stephen M.; Kaplitt, Michael G.; Surmeier, Dalton J.; Heintz, Nathaniel; Greengard, Paul

    2014-01-01

    Recurrent axon collaterals are a major means of communication between spiny projection neurons (SPNs) in the striatum and profoundly affect the function of the basal ganglia. However, little is known about the molecular and cellular mechanisms that underlie this communication. We show that intrastriatal nitric oxide (NO) signaling elevates the expression of the vesicular GABA transporter (VGAT) within recurrent collaterals of SPNs. Down-regulation of striatal NO signaling resulted in an attenuation of GABAergic signaling in SPN local collaterals, down-regulation of VGAT expression in local processes of SPNs, and impaired motor behavior. PKG1 and cAMP response element-binding protein are involved in the signal transduction that transcriptionally regulates VGAT by NO. These data suggest that transcriptional control of the vesicular GABA transporter by NO regulates GABA transmission and action selection. PMID:25413364

  8. Statistical models of synaptic transmission evaluated using the expectation-maximization algorithm.

    PubMed Central

    Stricker, C; Redman, S

    1994-01-01

    Amplitude fluctuations of evoked synaptic responses can be used to extract information on the probabilities of release at the active sites, and on the amplitudes of the synaptic responses generated by transmission at each active site. The parameters that describe this process must be obtained from an incomplete data set represented by the probability density of the evoked synaptic response. In this paper, the equations required to calculate these parameters using the Expectation-Maximization algorithm and the maximum likelihood criterion have been derived for a variety of statistical models of synaptic transmission. These models are ones where the probabilities associated with the different discrete amplitudes in the evoked responses are a) unconstrained, b) binomial, and c) compound binomial. The discrete amplitudes may be separated by equal (quantal) or unequal amounts, with or without quantal variance. Alternative models have been considered where the variance associated with the discrete amplitudes is sufficiently large such that no quantal amplitudes can be detected. These models involve the sum of a normal distribution (to represent failures) and a unimodal distribution (to represent the evoked responses). The implementation of the algorithm is described in each case, and its accuracy and convergence have been demonstrated. PMID:7948679

  9. Opioid Peptides Inhibit Excitatory But Not Inhibitory Synaptic Transmission in the Rat Dorsal Motor Nucleus of the Vagus

    PubMed Central

    Browning, Kirsteen N.; Kalyuzhny, Alexander E.; Travagli, R. Alberto

    2011-01-01

    Opioid peptides produce gastrointestinal inhibition and increase feeding when applied to the brainstem. The present studies were designed to determine the actions of opioid peptides on synaptic transmission within the dorsal motor nucleus of the vagus (DMV) and the localization of μ-opioid receptors. Whole-cell recordings were made from identified gastrointestinal-projecting DMV neurons in thin brainstem slices of the rat. Electrical stimulation of the nucleus of the tractus solitarius evoked EPSCs and IPSCs. In all neurons tested, methionine (Met)-enkephalin (0.003–30 μm) inhibited the peak amplitude of the EPSCs. The effect was prevented by naloxone (1 μm) as well as by naloxonazine (0.2 μm). An increase in the ratio of the evoked paired pulses indicated that the inhibition was attributable to actions at presynaptic receptors. This presynaptic inhibitory action was mimicked by [d-Ala2, N-Me-Phe4, Gly5-ol]-enkephalin (0.1 μm) and the analgesic dipeptide kyotorphin (10 μm) but not by cyclic[d-Pen2, d-Pen5]-enkephalin (1 μm) and trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]benzeneacetamide methanesulfonate (1 μm). In contrast, the amplitude of evoked IPSCs was not altered either by Met-enkephalin or by any of the opioid receptor-selective agonists. Immunohistochemical studies revealed that nerve terminals apposing DMV neurons showed immunoreactivity to μ-opioid receptors colocalized with glutamate immunoreactivity but not glutamic acid decarboxylase immunoreactivity. These results suggest that within the DMV, μ-opioid receptors are present on the nerve terminals of excitatory but not inhibitory inputs to GI motoneurons. Such specificity may imply that the central inhibitory action of opioid peptides on gastrointestinal function targets selected pathways. PMID:11943802

  10. Synaptic and circuit mechanisms promoting broadband transmission of olfactory stimulus dynamics.

    PubMed

    Nagel, Katherine I; Hong, Elizabeth J; Wilson, Rachel I

    2015-01-01

    Sensory stimuli fluctuate on many timescales. However, short-term plasticity causes synapses to act as temporal filters, limiting the range of frequencies that they can transmit. How synapses in vivo might transmit a range of frequencies in spite of short-term plasticity is poorly understood. The first synapse in the Drosophila olfactory system exhibits short-term depression, but can transmit broadband signals. Here we describe two mechanisms that broaden the frequency characteristics of this synapse. First, two distinct excitatory postsynaptic currents transmit signals on different timescales. Second, presynaptic inhibition dynamically updates synaptic properties to promote accurate transmission of signals across a wide range of frequencies. Inhibition is transient, but grows slowly, and simulations reveal that these two features of inhibition promote broadband synaptic transmission. Dynamic inhibition is often thought to restrict the temporal patterns that a neuron responds to, but our results illustrate a different idea: inhibition can expand the bandwidth of neural coding. PMID:25485755

  11. Synaptic and circuit mechanisms promoting broadband transmission of olfactory stimulus dynamics

    PubMed Central

    Nagel, Katherine I.; Hong, Elizabeth J.; Wilson, Rachel I.

    2014-01-01

    Sensory stimuli fluctuate on many timescales. However, short-term plasticity causes synapses to act as temporal filters, limiting the range of frequencies they can transmit. How synapses in vivo might transmit a range of frequencies in spite of short-term plasticity is poorly understood. The first synapse in the Drosophila olfactory system exhibits short-term depression, and yet can transmit broadband signals. Here we describe two mechanisms that broaden the frequency characteristics of this synapse. First, two distinct excitatory postsynaptic currents transmit signals on different timescales. Second, presynaptic inhibition dynamically updates synaptic properties to promote accurate transmission of signals across a wide range of frequencies. Inhibition is transient but grows slowly, and simulations show that these two features of inhibition promote broadband synaptic transmission. Dynamic inhibition is often thought to restrict the temporal patterns that a neuron responds to, but our results illustrate a different idea: inhibition can expand the bandwidth of neural coding. PMID:25485755

  12. Postsynaptic conversion of silent synapses during LTP affects synaptic gain and transmission dynamics.

    PubMed

    Poncer, J C; Malinow, R

    2001-10-01

    Synaptic transmission relies on both the gain and the dynamics of synapses. Activity-dependent changes in synaptic gain are well-documented at excitatory synapses and may represent a substrate for information storage in the brain. Here we examine the mechanisms of changes in transmission dynamics at excitatory synapses. We show that paired-pulse ratios (PPRs) of AMPAR and NMDAR EPSCs onto dentate gyrus granule cells are often different; this difference is reduced during LTP, reflecting PPR changes of AMPAR but not NMDAR EPSCs. Presynaptic manipulations, however, produce parallel changes in AMPAR and NMDAR EPSCs. LTP at these synapses reflects a reduction in the proportion of silent synapses lacking functional AMPARs. Changes in PPR during LTP therefore reflect the initial difference between PPRs of silent and functional synapses. Functional conversion of silent synapses permits postsynaptic sampling from additional release sites and thereby affects the dynamics and gain of signals conveyed between neurons. PMID:11544481

  13. Astrocytes contribute to the effects of etomidate on synaptic transmission in rat primary somatosensory cortex.

    PubMed

    Yang, Hao; Wang, Yuan; Zhang, Yu; Zhang, You; Xu, Mao-Sheng; Yuan, Jie; Yu, Tian

    2016-07-01

    Little is known about the mechanisms of unconsciousness induced by general anesthetics. Previous studies have shown that the primary somatosensory cortex (S1) is a sensitive region to a variety of intravenous general anesthetics. Etomidate is a widely used intravenous anesthetic that can influence synaptic transmission. Recently, there are some evidences suggesting that astrocytes, a type of glia cell, also contribute to information transmission in the brain, and modulate synaptic function by releasing neuroactive substances. However, it is unknown whether astrocytes influence the effects of etomidate on information transmission in S1 pyramidal neurons. In the present study, the role of astrocytes in etomidate-induced unconsciousness was investigated by using the whole-cell patch clamp technique. We observed etomidate at clinically relevant concentrations inhibited the spontaneous postsynaptic currents (sPSCs) of rat S1 pyramidal neurons in a concentration-dependent manner, and the EC50 value of etomidate for inhibiting sPSCs from the concentration-effect curve was 6.9μM. Furthermore, in the presence of fluorocitrate, a glia-selective metabolism inhibitor that blocks the aconitase enzyme, both the amplitude and frequency of sPSCs in rat S1 pyramidal neurons were reduced, and the inhibitory effects of etomidate on sPSCs amplitude was strengthened without affecting the effects of etomidate on frequency. From these data, we deduce that etomidate suppresses synaptic activity via presynaptic and postsynaptic components. Furthermore, astrocytes participate in synaptic transmission and influence the effects of etomidate on postsynaptic receptors. This study provides new insight into the role of astrocytes in etomidate-induced unconsciousness. PMID:27045115

  14. Regulation of Synaptic Transmission by RAB-3 and RAB-27 in Caenorhabditis elegans

    PubMed Central

    Mahoney, Timothy R.; Liu, Qiang; Itoh, Takashi; Luo, Shuo; Hadwiger, Gayla; Vincent, Rose; Wang, Zhao-Wen; Fukuda, Mitsunori

    2006-01-01

    Rab small GTPases are involved in the transport of vesicles between different membranous organelles. RAB-3 is an exocytic Rab that plays a modulatory role in synaptic transmission. Unexpectedly, mutations in the Caenorhabditis elegans RAB-3 exchange factor homologue, aex-3, cause a more severe synaptic transmission defect as well as a defecation defect not seen in rab-3 mutants. We hypothesized that AEX-3 may regulate a second Rab that regulates these processes with RAB-3. We found that AEX-3 regulates another exocytic Rab, RAB-27. Here, we show that C. elegans RAB-27 is localized to synapse-rich regions pan-neuronally and is also expressed in intestinal cells. We identify aex-6 alleles as containing mutations in rab-27. Interestingly, aex-6 mutants exhibit the same defecation defect as aex-3 mutants. aex-6; rab-3 double mutants have behavioral and pharmacological defects similar to aex-3 mutants. In addition, we demonstrate that RBF-1 (rabphilin) is an effector of RAB-27. Therefore, our work demonstrates that AEX-3 regulates both RAB-3 and RAB-27, that both RAB-3 and RAB-27 regulate synaptic transmission, and that RAB-27 potentially acts through its effector RBF-1 to promote soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) function. PMID:16571673

  15. Effects of Modafinil on Behavioral Learning and Hippocampal Synaptic Transmission in Rats

    PubMed Central

    Chen, Chong; Wang, Hai-Xia; Li, Chu-Hua; Huang, Jun-Ni; Xiao, Peng

    2015-01-01

    Purpose: Modafinil is a wake-promoting agent that has been proposed to improve cognitive performance at the preclinical and clinical levels. Since there is insufficient evidence for modafinil to be regarded as a cognitive enhancer, the aim of this study was to investigate the effects of chronic modafinil administration on behavioral learning in healthy adult rats. Methods: Y-maze training was used to assess learning performance, and the whole-cell patch clamp technique was used to assess synaptic transmission in pyramidal neurons of the hippocampal CA1 region of rats. Results: Intraperitoneal administration of modafinil at 200 mg/kg or 300 mg/kg significantly improved learning performance. Furthermore, perfusion with 1mM modafinil enhanced the frequency and amplitude of spontaneous postsynaptic currents and spontaneous excitatory postsynaptic currents in CA1 pyramidal neurons in hippocampal slices. However, the frequency and amplitude of spontaneous inhibitory postsynaptic currents in CA1 pyramidal neurons were inhibited by treatment with 1mM modafinil. Conclusions: These results indicate that modafinil improves learning and memory in rats possibly by enhancing glutamatergic excitatory synaptic transmission and inhibiting GABAergic (gamma-aminobutyric acid-ergic) inhibitory synaptic transmission. PMID:26739176

  16. Adult Onset-hypothyroidism has Minimal Effects on Synaptic Transmission in the Hippocampus of Rats Independent of Hypothermia

    EPA Science Inventory

    Introduction: Thyroid hormones (TH) influence central nervous system (CNS) function during development and in adulthood. The hippocampus, a brain area critical for learning and memory is sensitive to TH insufficiency. Synaptic transmission in the hippocampus is impaired following...

  17. Dysfunctional Astrocytic and Synaptic Regulation of Hypothalamic Glutamatergic Transmission in a Mouse Model of Early-Life Adversity: Relevance to Neurosteroids and Programming of the Stress Response

    PubMed Central

    Gunn, Benjamin G.; Cunningham, Linda; Cooper, Michelle A.; Corteen, Nicole L.; Seifi, Mohsen; Swinny, Jerome D.; Lambert, Jeremy J.

    2013-01-01

    Adverse early-life experiences, such as poor maternal care, program an abnormal stress response that may involve an altered balance between excitatory and inhibitory signals. Here, we explored how early-life stress (ELS) affects excitatory and inhibitory transmission in corticotrophin-releasing factor (CRF)-expressing dorsal-medial (mpd) neurons of the neonatal mouse hypothalamus. We report that ELS associates with enhanced excitatory glutamatergic transmission that is manifested as an increased frequency of synaptic events and increased extrasynaptic conductance, with the latter associated with dysfunctional astrocytic regulation of glutamate levels. The neurosteroid 5α-pregnan-3α-ol-20-one (5α3α-THPROG) is an endogenous, positive modulator of GABAA receptors (GABAARs) that is abundant during brain development and rises rapidly during acute stress, thereby enhancing inhibition to curtail stress-induced activation of the hypothalamic-pituitary-adrenocortical axis. In control mpd neurons, 5α3α-THPROG potently suppressed neuronal discharge, but this action was greatly compromised by prior ELS exposure. This neurosteroid insensitivity did not primarily result from perturbations of GABAergic inhibition, but rather arose functionally from the increased excitatory drive onto mpd neurons. Previous reports indicated that mice (dams) lacking the GABAAR δ subunit (δ0/0) exhibit altered maternal behavior. Intriguingly, δ0/0 offspring showed some hallmarks of abnormal maternal care that were further exacerbated by ELS. Moreover, in common with ELS, mpd neurons of δ0/0 pups exhibited increased synaptic and extrasynaptic glutamatergic transmission and consequently a blunted neurosteroid suppression of neuronal firing. This study reveals that increased synaptic and tonic glutamatergic transmission may be a common maladaptation to ELS, leading to enhanced excitation of CRF-releasing neurons, and identifies neurosteroids as putative early regulators of the stress

  18. Short-term plasticity and modulation of synaptic transmission at mammalian inhibitory cholinergic olivocochlear synapses

    PubMed Central

    Katz, Eleonora; Elgoyhen, Ana Belén

    2014-01-01

    The organ of Corti, the mammalian sensory epithelium of the inner ear, has two types of mechanoreceptor cells, inner hair cells (IHCs) and outer hair cells (OHCs). In this sensory epithelium, vibrations produced by sound waves are transformed into electrical signals. When depolarized by incoming sounds, IHCs release glutamate and activate auditory nerve fibers innervating them and OHCs, by virtue of their electromotile property, increase the amplification and fine tuning of sound signals. The medial olivocochlear (MOC) system, an efferent feedback system, inhibits OHC activity and thereby reduces the sensitivity and sharp tuning of cochlear afferent fibers. During neonatal development, IHCs fire Ca2+ action potentials which evoke glutamate release promoting activity in the immature auditory system in the absence of sensory stimuli. During this period, MOC fibers also innervate IHCs and are thought to modulate their firing rate. Both the MOC-OHC and the MOC-IHC synapses are cholinergic, fast and inhibitory and mediated by the α9α10 nicotinic cholinergic receptor (nAChR) coupled to the activation of calcium-activated potassium channels that hyperpolarize the hair cells. In this review we discuss the biophysical, functional and molecular data which demonstrate that at the synapses between MOC efferent fibers and cochlear hair cells, modulation of transmitter release as well as short term synaptic plasticity mechanisms, operating both at the presynaptic terminal and at the postsynaptic hair-cell, determine the efficacy of these synapses and shape the hair cell response pattern. PMID:25520631

  19. Modes of glutamate receptor gating

    PubMed Central

    Popescu, Gabriela K

    2012-01-01

    Abstract The time course of excitatory synaptic currents, the major means of fast communication between neurons of the central nervous system, is encoded in the dynamic behaviour of post-synaptic glutamate-activated channels. First-pass attempts to explain the glutamate-elicited currents with mathematical models produced reaction mechanisms that included only the most basic functionally defined states: resting vs. liganded, closed vs. open, responsive vs. desensitized. In contrast, single-molecule observations afforded by the patch-clamp technique revealed an unanticipated kinetic multiplicity of transitions: from microseconds-lasting flickers to minutes-long modes. How these kinetically defined events impact the shape of the synaptic response, how they relate to rearrangements in receptor structure, and whether and how they are physiologically controlled represent currently active research directions. Modal gating, which refers to the slowest, least frequently observed ion-channel transitions, has been demonstrated for representatives of all ion channel families. However, reaction schemes have been largely confined to the short- and medium-range time scales. For glutamate receptors as well, modal gating has only recently come under rigorous scrutiny. This article reviews the evidence for modal gating of glutamate receptors and the still developing hypotheses about the mechanism(s) by which modal shifts occur and the ways in which they may impact the time course of synaptic transmission. PMID:22106181

  20. Alcohol-seeking behavior is associated with increased glutamate transmission in basolateral amygdala and nucleus accumbens as measured by glutamate-oxidase coated biosensors

    PubMed Central

    Gass, Justin T.; Sinclair, Courtney M.; Cleva, Richard M.; Widholm, John J.; Olive, M. Foster

    2010-01-01

    Relapse is one of the most problematic aspects in the treatment of alcoholism and is often triggered by alcohol-associated environmental cues. Evidence indicates that glutamate neurotransmission plays a critical role in cue-induced relapse-like behavior, as inhibition of glutamate neurotransmission can prevent reinstatement of alcohol-seeking behavior. However, few studies have examined specific changes in extracellular glutamate levels in discrete brain regions produced by exposure to alcohol-associated cues. The purpose of this study was to use glutamate oxidase (GluOx)-coated biosensors to monitor changes in extracellular glutamate in specific brain regions during cue-induced reinstatement of alcohol-seeking behavior. Male Wistar rats were implanted with indwelling jugular vein catheters and intracerebral guide cannula aimed at the basolateral amygdala (BLA) or nucleus accumbens (NAc) core, and then trained to self-administer alcohol intravenously. A separate group of animals was trained to self-administer food pellets. Each reinforcer was accompanied by the presentation of a light/tone stimulus. Following stabilization of responding for alcohol or food reinforcement and subsequent extinction training, animals were implanted with precalibrated biosensors and then underwent a 1 hr cue-induced reinstatement testing period. As determined by GluOx-coated biosensors, extracellular levels of glutamate were increased in the BLA and NAc core during cue-induced reinstatement of alcohol-seeking behavior. The cumulative change in extracellular glutamate in both regions was significantly greater for cue-induced reinstatement of alcohol-seeking behavior versus that of food-seeking behavior. These results indicate that increases in glutamate transmission in the BLA and NAc core may be a neurochemical substrate of cue-evoked alcohol-seeking behavior. PMID:21054692

  1. Taurine-Induced Long-Lasting Enhancement of Synaptic Transmission in Mice: Role of Transporters

    PubMed Central

    Sergeeva, O A; Chepkova, A N; Doreulee, N; Eriksson, K S; Poelchen, W; Mönnighoff, I; Heller-Stilb, B; Warskulat, U; Häussinger, D; Haas, H L

    2003-01-01

    Taurine, a major osmolyte in the brain evokes a long-lasting enhancement (LLETAU) of synaptic transmission in hippocampal and cortico-striatal slices. Hippocampal LLETAU was abolished by the GABA uptake blocker nipecotic acid (NPA) but not by the taurine-uptake inhibitor guanidinoethyl sulphonate (GES). Striatal LLETAU was sensitive to GES but not to NPA. Semiquantitative PCR analysis and immunohistochemistry revealed that taurine transporter expression is significantly higher in the striatum than in the hippocampus. Taurine transporter-deficient mice displayed very low taurine levels in both structures and a low ability to develop LLETAU in the striatum, but not in the hippocampus. The different mechanisms of taurine-induced synaptic plasticity may reflect the different vulnerabilities of these brain regions under pathological conditions that are accompanied by osmotic changes such as hepatic encephalopathy. PMID:12824447

  2. Thrombin regulation of synaptic transmission and plasticity: implications for health and disease

    PubMed Central

    Ben Shimon, Marina; Lenz, Maximilian; Ikenberg, Benno; Becker, Denise; Shavit Stein, Efrat; Chapman, Joab; Tanne, David; Pick, Chaim G.; Blatt, Ilan; Neufeld, Miri; Vlachos, Andreas; Maggio, Nicola

    2015-01-01

    Thrombin, a serine protease involved in the blood coagulation cascade has been shown to affect neural function following blood-brain barrier breakdown. However, several lines of evidence exist that thrombin is also expressed in the brain under physiological conditions, suggesting an involvement of thrombin in the regulation of normal brain functions. Here, we review ours’ as well as others’ recent work on the role of thrombin in synaptic transmission and plasticity through direct or indirect activation of Protease-Activated Receptor-1 (PAR1). These studies propose a novel role of thrombin in synaptic plasticity, both in physiology as well as in neurological diseases associated with increased brain thrombin/PAR1 levels. PMID:25954157

  3. Developmental Exposure to Perchlorate Alters Synaptic Transmission in Hippocampus of the Adult Rat

    PubMed Central

    Gilbert, Mary E.; Sui, Li

    2008-01-01

    Background Perchlorate is an environmental contaminant that blocks iodine uptake into the thyroid gland and reduces thyroid hormones. This action of perchlorate raises significant concern over its effects on brain development. Objectives The purpose of this study was to evaluate neurologic function in rats after developmental exposure to perchlorate. Methods Pregnant rats were exposed to 0, 30, 300, or 1,000 ppm perchlorate in drinking water from gestational day 6 until weaning. Adult male offspring were evaluated on a series of behavioral tasks and neurophysiologic measures of synaptic function in the hippocampus. Results At the highest perchlorate dose, triiodothyronine (T3) and thyroxine (T4) were reduced in pups on postnatal day 21. T4 in dams was reduced relative to controls by 16%, 28%, and 60% in the 30-, 300-, and 1,000-ppm dose groups, respectively. Reductions in T4 were associated with increases in thyroid-stimulating hormone in the high-dose group. No changes were seen in serum T3. Perchlorate did not impair motor activity, spatial learning, or fear conditioning. However, significant reductions in baseline synaptic transmission were observed in hippocampal field potentials at all dose levels. Reductions in inhibitory function were evident at 300 and 1,000 ppm, and augmentations in long-term potentiation were observed in the population spike measure at the highest dose. Conclusions Dose-dependent deficits in hippocampal synaptic function were detectable with relatively minor perturbations of the thyroid axis, indicative of an irreversible impairment in synaptic transmission in response to developmental exposure to perchlorate. PMID:18560531

  4. Interactions of Human Autoantibodies with Hippocampal GABAergic Synaptic Transmission – Analyzing Antibody-Induced Effects ex vivo

    PubMed Central

    Haselmann, Holger; Röpke, Luise; Werner, Christian; Kunze, Albrecht; Geis, Christian

    2015-01-01

    Autoantibodies (aAB) to the presynaptic located enzyme glutamate decarboxylase 65 (GAD65) are a characteristic attribute for a variety of autoimmune diseases of the central nervous system including subtypes of limbic encephalitis, stiff person-syndrome, cerebellar ataxia, and Batten’s disease. Clinical signs of hyperexcitability and improvement of disease symptoms upon immunotherapy in some of these disorders suggest a possible pathogenic role of associated aAB. Recent experimental studies report inconsistent results regarding a direct pathogenic influence of anti-GAD65 aAB affecting inhibitory synaptic transmission in central GABAergic pathways. We here provide a method for direct evaluation of aAB-induced pathomechanisms in the intact hippocampal network. Purified patient IgG fractions containing aAB to GAD65 together with fixable lipophilic styryl dyes (FMdyes) are stereotactically injected into the hilus and the dentate gyrus in anesthetized mice. Twenty-four hours after intrahippocampal injection, acute hippocampal slices are prepared and transferred to a patch-clamp recording setup equipped with a fluorescence light source. Intraneural incorporated FMdyes show correct injection site for patch-clamp recording. Whole-cell patch-clamp recordings are performed from granule cells in the dentate gyrus and extracellular stimulation is applied in the border area of the dentate gyrus-hilus region to stimulate GABAergic afferents arising from parvalbumin positive basket cells. GABA-A receptor mediated inhibitory postsynaptic currents (IPSC) and miniature IPSC are recorded after blocking glutamatergic transmission. This approach allows investigation of potential aAB-induced effects on GABA-A receptor signaling ex vivo in an intact neuronal network. This offers several advantages compared to experimental procedures used in previous studies by in vitro AB preincubation of primary neurons or slice preparations. Furthermore, this method requires only small amounts of

  5. Mice lacking brain/kidney phosphate-activated glutaminase (GLS1) have impaired glutamatergic synaptic transmission, altered breathing, disorganized goal-directed behavior and die shortly after birth

    PubMed Central

    Masson, Justine; Darmon, Michèle; Conjard, Agnès; Chuhma, Nao; Ropert, Nicole; Thoby-Brisson, Muriel; Foutz, Arthur S.; Parrot, Sandrine; Miller, Gretchen M.; Jorisch, Renée; Polan, Jonathan; Hamon, Michel; Hen, René; Rayport, Stephen

    2009-01-01

    Neurotransmitter glutamate has been thought to derive mainly from glutamine via the action of glutaminase type 1 (GLS1). To address the importance of this pathway in glutamatergic transmission, we knocked out GLS1 in mice. The insertion of a STOP cassette by homologous recombination produced a null allele that blocked transcription, encoded no immunoreactive protein and abolished GLS1 enzymatic activity. Null mutants were slightly smaller, were deficient in goal-directed behavior, hypoventilated and died in the first post-natal day. No gross or microscopic defects were detected in peripheral organs or in the central nervous system. In cultured neurons from the null mutants, miniature EPSC amplitude and duration were normal; however, the amplitude of evoked EPSCs decayed more rapidly with sustained 10 Hz stimulation, consistent with an observed reduction in depolarization-evoked glutamate release. Because of this activity-dependent impairment in glutamatergic transmission, we surmised that respiratory networks, which require temporal summation of synaptic input, would be particularly affected. We found that the amplitude of inspirations was decreased in vivo, chemosensitivity to CO2 was severely altered, and the frequency of pacemaker activity recorded in the respiratory generator in the Pre-Bötzinger complex, a glutamatergic brainstem network that can be isolated in vitro, was increased. Our results show that while alternate pathways to GLS1 glutamate synthesis support baseline glutamatergic transmission, the GLS1 pathway is essential for maintaining the function of active synapses, and so the mutation is associated with impaired respiratory function, abnormal goal-directed behavior and neonatal demise. PMID:16641247

  6. Bidirectional regulation of synaptic transmission by BRAG1/IQSEC2 and its requirement in long-term depression

    PubMed Central

    Brown, Joshua C.; Petersen, Amber; Zhong, Ling; Himelright, Miranda L.; Murphy, Jessica A.; Walikonis, Randall S.; Gerges, Nashaat Z.

    2016-01-01

    Dysfunction of the proteins regulating synaptic function can cause synaptic plasticity imbalance that underlies neurological disorders such as intellectual disability. A study found that four distinct mutations within BRAG1, an Arf-GEF synaptic protein, each led to X-chromosome-linked intellectual disability (XLID). Although the physiological functions of BRAG1 are poorly understood, each of these mutations reduces BRAG1's Arf-GEF activity. Here we show that BRAG1 is required for the activity-dependent removal of AMPA receptors in rat hippocampal pyramidal neurons. Moreover, we show that BRAG1 bidirectionally regulates synaptic transmission. On one hand, BRAG1 is required for the maintenance of synaptic transmission. On the other hand, BRAG1 expression enhances synaptic transmission, independently of BRAG1 Arf-GEF activity or neuronal activity, but dependently on its C-terminus interactions. This study demonstrates a dual role of BRAG1 in synaptic function and highlights the functional relevance of reduced BRAG1 Arf-GEF activity as seen in the XLID-associated human mutations. PMID:27009485

  7. Graphene Oxide Nanosheets Disrupt Lipid Composition, Ca(2+) Homeostasis, and Synaptic Transmission in Primary Cortical Neurons.

    PubMed

    Bramini, Mattia; Sacchetti, Silvio; Armirotti, Andrea; Rocchi, Anna; Vázquez, Ester; León Castellanos, Verónica; Bandiera, Tiziano; Cesca, Fabrizia; Benfenati, Fabio

    2016-07-26

    Graphene has the potential to make a very significant impact on society, with important applications in the biomedical field. The possibility to engineer graphene-based medical devices at the neuronal interface is of particular interest, making it imperative to determine the biocompatibility of graphene materials with neuronal cells. Here we conducted a comprehensive analysis of the effects of chronic and acute exposure of rat primary cortical neurons to few-layer pristine graphene (GR) and monolayer graphene oxide (GO) flakes. By combining a range of cell biology, microscopy, electrophysiology, and "omics" approaches we characterized the graphene-neuron interaction from the first steps of membrane contact and internalization to the long-term effects on cell viability, synaptic transmission, and cell metabolism. GR/GO flakes are found in contact with the neuronal membrane, free in the cytoplasm, and internalized through the endolysosomal pathway, with no significant impact on neuron viability. However, GO exposure selectively caused the inhibition of excitatory transmission, paralleled by a reduction in the number of excitatory synaptic contacts, and a concomitant enhancement of the inhibitory activity. This was accompanied by induction of autophagy, altered Ca(2+) dynamics, and a downregulation of some of the main players in the regulation of Ca(2+) homeostasis in both excitatory and inhibitory neurons. Our results show that, although graphene exposure does not impact neuron viability, it does nevertheless have important effects on neuronal transmission and network functionality, thus warranting caution when planning to employ this material for neurobiological applications. PMID:27359048

  8. Novel nootropic dipeptide Noopept increases inhibitory synaptic transmission in CA1 pyramidal cells.

    PubMed

    Kondratenko, Rodion V; Derevyagin, Vladimir I; Skrebitsky, Vladimir G

    2010-05-31

    Effects of newly synthesized nootropic and anxiolytic dipeptide Noopept on inhibitory synaptic transmission in hippocampal CA1 pyramidal cells were investigated using patch-clamp technique in whole-cell configuration. Bath application of Noopept (1 microM) significantly increased the frequency of spike-dependant spontaneous IPSCs whereas spike-independent mIPSCs remained unchanged. It was suggested that Noopept mediates its effect due to the activation of inhibitory interneurons terminating on CA1 pyramidal cells. Results of current clamp recording of inhibitory interneurons residing in stratum radiatum confirmed this suggestion. PMID:20382202

  9. Mice deficient for prion protein exhibit normal neuronal excitability and synaptic transmission in the hippocampus.

    PubMed Central

    Lledo, P M; Tremblay, P; DeArmond, S J; Prusiner, S B; Nicoll, R A

    1996-01-01

    We recorded in the CA1 region from hippocampal slices of prion protein (PrP) gene knockout mice to investigate whether the loss of the normal form of prion protein (PrPC) affects neuronal excitability as well as synaptic transmission in the central nervous system. No deficit in synaptic inhibition was found using field potential recordings because (i) responses induced by stimulation in stratum radiatum consisted of a single population spike in PrP gene knockout mice similar to that recorded from control mice and (ii) the plot of field excitatory postsynaptic potential slope versus the population spike amplitude showed no difference between the two groups of mice. Intracellular recordings also failed to detect any difference in cell excitability and the reversal potential for inhibitory postsynaptic potentials. Analysis of the kinetics of inhibitory postsynaptic current revealed no modification. Finally, we examined whether synaptic plasticity was altered and found no difference in long-term potentiation between control and PrP gene knockout mice. On the basis of our findings, we propose that the loss of the normal form of prion protein does not alter the physiology of the CA1 region of the hippocampus. PMID:8637886

  10. Enhancement of synaptic transmission induced by BDNF in cultured cortical neurons

    NASA Astrophysics Data System (ADS)

    He, Jun; Gong, Hui; Zeng, Shaoqun; Li, Yanling; Luo, Qingming

    2005-03-01

    Brain-derived neurotrophic factor (BDNF), like other neurotrophins, has long-term effects on neuronal survival and differentiation; furthermore, BDNF has been reported to exert an acute potentiation of synaptic activity and are critically involved in long-term potentiation (LTP). We found that BDNF rapidly induced potentiation of synaptic activity and an increase in the intracellular Ca2+ concentration in cultured cortical neurons. Within minutes of BDNF application to cultured cortical neurons, spontaneous firing rate was dramatically increased as were the frequency and amplitude of excitatory spontaneous postsynaptic currents (EPSCs). Fura-2 recordings showed that BDNF acutely elicited an increase in intracellular calcium concentration ([Ca2+]c). This effect was partially dependent on [Ca2+]o; The BDNF-induced increase in [Ca2+]c can not be completely blocked by Ca2+-free solution. It was completely blocked by K252a and partially blocked by Cd2+ and TTX. The results demonstrate that BDNF can enhances synaptic transmission and that this effect is accompanied by a rise in [Ca2+]c that requires two route: the release of Ca2+ from intracellular calcium stores and influx of extracellular Ca2+ through voltage-dependent Ca2+ channels in cultured cortical neurons.

  11. Mice Deficient for Prion Protein Exhibit Normal Neuronal Excitability and Synaptic Transmission in the Hippocampus

    NASA Astrophysics Data System (ADS)

    Lledo, Pierre-Marie; Tremblay, Patrick; Dearmond, Stephen J.; Prusiner, Stanley B.; Nicoll, Roger A.

    1996-03-01

    We recorded in the CA1 region from hippocampal slices of prion protein (PrP) gene knockout mice to investigate whether the loss of the normal form of prion protein (PrPC) affects neuronal excitability as well as synaptic transmission in the central nervous system. No deficit in synaptic inhibition was found using field potential recordings because (i) responses induced by stimulation in stratum radiatum consisted of a single population spike in PrP gene knockout mice similar to that recorded from control mice and (ii) the plot of field excitatory postsynaptic potential slope versus the population spike amplitude showed no difference between the two groups of mice. Intracellular recordings also failed to detect any difference in cell excitability and the reversal potential for inhibitory postsynaptic potentials. Analysis of the kinetics of inhibitory postsynaptic current revealed no modification. Finally, we examined whether synaptic plasticity was altered and found no difference in long-term potentiation between control and PrP gene knockout mice. On the basis of our findings, we propose that the loss of the normal form of prion protein does not alter the physiology of the CA1 region of the hippocampus.

  12. A TRPV Channel in Drosophila Motor Neurons Regulates Presynaptic Resting Ca2+ Levels, Synapse Growth, and Synaptic Transmission

    PubMed Central

    Wong, Ching-On; Chen, Kuchuan; Lin, Yong Qi; Chao, Yufang; Duraine, Lita; Lu, Zhongmin; Yoon, Wan Hee; Sullivan, Jeremy M.; Broadhead, Geoffrey T.; Sumner, Charlotte J.; Lloyd, Thomas E.; Macleod, Gregory T.; Bellen, Hugo J.; Venkatachalam, Kartik

    2014-01-01

    SUMMARY Presynaptic resting Ca2+ influences synaptic vesicle (SV) release probability. Here, we report that a TRPV channel, Inactive (Iav), maintains presynaptic resting [Ca2+] by promoting Ca2+ release from the endoplasmic reticulum in Drosophila motor neurons, and is required for both synapse development and neurotransmission. We find that Iav activates the Ca2+/calmodulin-dependent protein phosphatase, calcineurin, which is essential for presynaptic microtubule stabilization at the neuromuscular junction. Thus, loss of Iav induces destabilization of presynaptic microtubules resulting in diminished synaptic growth. Interestingly, expression of human TRPV1 in Iav-deficient motor neurons rescues these defects. We also show that the absence of Iav causes lower SV release probability and diminished synaptic transmission, whereas Iav overexpression elevates these synaptic parameters. Together, our findings indicate that Iav acts as a key regulator of synaptic development and function by influencing presynaptic resting [Ca2+]. PMID:25451193

  13. Roles of N-Type and Q-Type Ca2+ Channels in Supporting Hippocampal Synaptic Transmission

    NASA Astrophysics Data System (ADS)

    Wheeler, David B.; Randall, Andrew; Tsien, Richard W.

    1994-04-01

    Several types of calcium channels found in the central nervous system are possible participants in triggering neurotransmitter release. Synaptic transmission between hippocampal CA3 and CA1 neurons was mediated by N-type calcium channels, together with calcium channels whose pharmacology differs from that of L- and P-type channels but resembles that of the Q-type channel encoded by the α1A subunit gene. Blockade of either population of channels strongly increased enhancement of synaptic transmission with repetitive stimuli. Even after complete blockade of N-type channels, transmission was strongly modulated by stimulation of neurotransmitter receptors or protein kinase C. These findings suggest a role for α1A subunits in synaptic transmission and support the idea that neurotransmitter release may depend on multiple types of calcium channels under physiological conditions.

  14. NR2B-dependent cyclophilin D translocation suppresses the recovery of synaptic transmission after oxygen-glucose deprivation.

    PubMed

    Zhang, Zhihua; Wang, Yongfu; Yan, Shijun; Du, Fang; Yan, Shirley Shidu

    2015-10-01

    N-methyl d-aspartate receptor (NMDA) subunit 2B (NR2B)-containing NMDA receptors and mitochondrial protein cyclophilin D (CypD) are well characterized in mediating neuronal death after ischemia, respectively. However, whether and how NR2B and CypD work together in mediating synaptic injury after ischemia remains elusive. Using an ex vivo ischemia model of oxygen-glucose deprivation (OGD) in hippocampal slices, we identified a NR2B-dependent mechanism for CypD translocation onto the mitochondrial inner membrane. CypD depletion (CypD null mice) prevented OGD-induced impairment in synaptic transmission recovery. Overexpression of neuronal CypD mice (CypD+) exacerbated OGD-induced loss of synaptic transmission. Inhibition of CypD-dependent mitochondrial permeability transition pore (mPTP) opening by cyclosporine A (CSA) attenuated ischemia-induced synaptic perturbation in CypD+ and non-transgenic (non-Tg) mice. The treatment of antioxidant EUK134 to suppress mitochondrial oxidative stress rescued CypD-mediated synaptic dysfunction following OGD in CypD+ slices. Furthermore, OGD provoked the interaction of CypD with P53, which was enhanced in slices overexpressing CypD but was diminished in CypD-null slices. Inhibition of p53 using a specific inhibitor of p53 (pifithrin-μ) attenuated the CypD/p53 interaction following OGD, along with a restored synaptic transmission in both non-Tg and CypD+ hippocampal slices. Our results indicate that OGD-induced CypD translocation potentiates CypD/P53 interaction in a NR2B dependent manner, promoting oxidative stress and loss of synaptic transmission. We also evaluate a new ex vivo chronic OGD-induced ischemia model for studying the effect of oxidative stress on synaptic damage. PMID:26232180

  15. Defective synaptic transmission and structure in the dentate gyrus and selective fear memory impairment in the Rsk2 mutant mouse model of Coffin-Lowry syndrome.

    PubMed

    Morice, Elise; Farley, Séverine; Poirier, Roseline; Dallerac, Glenn; Chagneau, Carine; Pannetier, Solange; Hanauer, André; Davis, Sabrina; Vaillend, Cyrille; Laroche, Serge

    2013-10-01

    The Coffin-Lowry syndrome (CLS) is a syndromic form of intellectual disability caused by loss-of-function of the RSK2 serine/threonine kinase encoded by the rsk2 gene. Rsk2 knockout mice, a murine model of CLS, exhibit spatial learning and memory impairments, yet the underlying neural mechanisms are unknown. In the current study, we examined the performance of Rsk2 knockout mice in cued, trace and contextual fear memory paradigms and identified selective deficits in the consolidation and reconsolidation of hippocampal-dependent fear memories as task difficulty and hippocampal demand increase. Electrophysiological, biochemical and electron microscopy analyses were carried out in the dentate gyrus of the hippocampus to explore potential alterations in neuronal functions and structure. In vivo and in vitro electrophysiology revealed impaired synaptic transmission, decreased network excitability and reduced AMPA and NMDA conductance in Rsk2 knockout mice. In the absence of RSK2, standard measures of short-term and long-term potentiation (LTP) were normal, however LTP-induced CREB phosphorylation and expression of the transcription factors EGR1/ZIF268 were reduced and that of the scaffolding protein SHANK3 was blocked, indicating impaired activity-dependent gene regulation. At the structural level, the density of perforated and non-perforated synapses and of multiple spine boutons was not altered, however, a clear enlargement of spine neck width and post-synaptic densities indicates altered synapse ultrastructure. These findings show that RSK2 loss-of-function is associated in the dentate gyrus with multi-level alterations that encompass modifications of glutamate receptor channel properties, synaptic transmission, plasticity-associated gene expression and spine morphology, providing novel insights into the mechanisms contributing to cognitive impairments in CLS. PMID:23742761

  16. Changes in synaptic plasticity and expression of glutamate receptor subunits in the CA1 and CA3 areas of the hippocampus after transient global ischemia.

    PubMed

    Han, Xin-Jia; Shi, Zhong-Shan; Xia, Luo-Xing; Zhu, Li-Hui; Zeng, Ling; Nie, Jun-Hua; Xu, Zao-Cheng; Ruan, Yi-Wen

    2016-07-01

    Excess glutamate release from the presynaptic membrane has been thought to be the major cause of ischemic neuronal death. Although both CA1 and CA3 pyramidal neurons receive presynaptic glutamate input, transient cerebral ischemia induces CA1 neurons to die while CA3 neurons remain relatively intact. This suggests that changes in the properties of pyramidal cells may be the main cause related to ischemic neuronal death. Our previous studies have shown that the densities of dendritic spines and asymmetric synapses in the CA1 area are increased at 12h and 24h after ischemia. In the present study, we investigated changes in synaptic structures in the CA3 area and compared the expression of glutamate receptors in the CA1 and CA3 hippocampal regions of rats after ischemia. Our results demonstrated that the NR2B/NR2A ratio became larger after ischemia although the expression of both the NR2B subunit (activation of apoptotic pathway) and NR2A subunit (activation of survival pathway) decreased in the CA1 area from 6h to 48h after reperfusion. Furthermore, expression of the GluR2 subunit (calcium impermeable) of the AMPA receptor class significantly decreased while the GluR1 subunit (calcium permeable) remained unchanged at the same examined reperfusion times, which subsequently caused an increase in the GluR1/GluR2 ratio. Despite these notable differences in subunit expression, there were no obvious changes in the density of synapses or expression of NMDAR and AMPAR subunits in the CA3 area after ischemia. These results suggest that delayed CA1 neuronal death may be related to the dramatic fluctuation in the synaptic structure and relative upregulation of NR2B and GluR1 subunits induced by transient global ischemia. PMID:27090818

  17. Synchronous and asynchronous modes of synaptic transmission utilize different calcium sources.

    PubMed

    Wen, Hua; Hubbard, Jeffrey M; Rakela, Benjamin; Linhoff, Michael W; Mandel, Gail; Brehm, Paul

    2013-01-01

    Asynchronous transmission plays a prominent role at certain synapses but lacks the mechanistic insights of its synchronous counterpart. The current view posits that triggering of asynchronous release during repetitive stimulation involves expansion of the same calcium domains underlying synchronous transmission. In this study, live imaging and paired patch clamp recording at the zebrafish neuromuscular synapse reveal contributions by spatially distinct calcium sources. Synchronous release is tied to calcium entry into synaptic boutons via P/Q type calcium channels, whereas asynchronous release is boosted by a propagating intracellular calcium source initiated at off-synaptic locations in the axon and axonal branch points. This secondary calcium source fully accounts for the persistence following termination of the stimulus and sensitivity to slow calcium buffers reported for asynchronous release. The neuromuscular junction and CNS neurons share these features, raising the possibility that secondary calcium sources are common among synapses with prominent asynchronous release. DOI: http://dx.doi.org/10.7554/eLife.01206.001. PMID:24368731

  18. Depression of Serotonin Synaptic Transmission by the Dopamine Precursor L-DOPA.

    PubMed

    Gantz, Stephanie C; Levitt, Erica S; Llamosas, Nerea; Neve, Kim A; Williams, John T

    2015-08-11

    Imbalance between the dopamine and serotonin (5-HT) neurotransmitter systems has been implicated in the comorbidity of Parkinson's disease (PD) and psychiatric disorders. L-DOPA, the leading treatment of PD, facilitates the production and release of dopamine. This study assessed the action of L-DOPA on monoamine synaptic transmission in mouse brain slices. Application of L-DOPA augmented the D2-receptor-mediated inhibitory postsynaptic current (IPSC) in dopamine neurons of the substantia nigra. This augmentation was largely due to dopamine release from 5-HT terminals. Selective optogenetic stimulation of 5-HT terminals evoked dopamine release, producing D2-receptor-mediated IPSCs following treatment with L-DOPA. In the dorsal raphe, L-DOPA produced a long-lasting depression of the 5-HT1A-receptor-mediated IPSC in 5-HT neurons. When D2 receptors were expressed in the dorsal raphe, application of L-DOPA resulted in a D2-receptor-mediated IPSC. Thus, treatment with L-DOPA caused ectopic dopamine release from 5-HT terminals and a loss of 5-HT-mediated synaptic transmission. PMID:26235617

  19. TLR3 deficiency impairs spinal cord synaptic transmission, central sensitization, and pruritus in mice

    PubMed Central

    Liu, Tong; Berta, Temugin; Xu, Zhen-Zhong; Park, Chul-Kyu; Zhang, Ling; Lü, Ning; Liu, Qin; Liu, Yang; Gao, Yong-Jing; Liu, Yen-Chin; Ma, Qiufu; Dong, Xinzhong; Ji, Ru-Rong

    2012-01-01

    Itch, also known as pruritus, is a common, intractable symptom of several skin diseases, such as atopic dermatitis and xerosis. TLRs mediate innate immunity and regulate neuropathic pain, but their roles in pruritus are elusive. Here, we report that scratching behaviors induced by histamine-dependent and -independent pruritogens are markedly reduced in mice lacking the Tlr3 gene. TLR3 is expressed mainly by small-sized primary sensory neurons in dorsal root ganglions (DRGs) that coexpress the itch signaling pathway components transient receptor potential subtype V1 and gastrin-releasing peptide. Notably, we found that treatment with a TLR3 agonist induces inward currents and action potentials in DRG neurons and elicited scratching in WT mice but not Tlr3–/– mice. Furthermore, excitatory synaptic transmission in spinal cord slices and long-term potentiation in the intact spinal cord were impaired in Tlr3–/– mice but not Tlr7–/– mice. Consequently, central sensitization–driven pain hypersensitivity, but not acute pain, was impaired in Tlr3–/– mice. In addition, TLR3 knockdown in DRGs also attenuated pruritus in WT mice. Finally, chronic itch in a dry skin condition was substantially reduced in Tlr3–/– mice. Our findings demonstrate a critical role of TLR3 in regulating sensory neuronal excitability, spinal cord synaptic transmission, and central sensitization. TLR3 may serve as a new target for developing anti-itch treatment. PMID:22565312

  20. Cationic influences upon synaptic transmission at the hair cell-afferent fiber synapse of the frog

    NASA Technical Reports Server (NTRS)

    Cochran, S. L.

    1995-01-01

    The concentrations of inorganic cations (K+, Na+, and Ca2+) bathing the isolated frog labyrinth were varied in order to assess their role in influencing and mediating synaptic transmission at the hair cell-afferent fiber synapse. Experiments employed intracellular recordings of synaptic activity from VIIIth nerve afferents. Recordings were digitized continuously at 50 kHz, and excitatory postsynaptic potentials were detected and parameters quantified by computer algorithms. Particular attention was focused on cationic effects upon excitatory postsynaptic potential frequency of occurrence and excitatory postsynaptic potential amplitude, in order to discriminate between pre- and postsynaptic actions. Because the small size of afferents preclude long term stable recordings, alterations in cationic concentrations were applied transiently and their peak effects on synaptic activity were assessed. Increases in extracellular K+ concentration of a few millimolar produced a large increase in the frequency of occurrence of excitatory postsynaptic potentials with little change in amplitude, indicating that release of transmitter from the hair cell is tightly coupled to its membrane potential. Increasing extracellular Na+ concentration resulted in an increase in excitatory postsynaptic potential amplitude with no significant change in excitatory postsynaptic potential frequency of occurrence, suggesting that the transmitter-gated subsynaptic channel conducts Na+ ions. Decreases in extracellular Ca2+ concentration had little effect upon excitatory postsynaptic potential frequency, but increased excitatory postsynaptic potential frequency and amplitude. These findings suggest that at higher concentrations Ca2+ act presynaptically to prevent transmitter release and postsynaptically to prevent Na+ influx during the generation of the excitatory postsynaptic potential. The influences of these ions on synaptic activity at this synapse are remarkably similar to those reported at the

  1. GSG1L suppresses AMPA receptor-mediated synaptic transmission and uniquely modulates AMPA receptor kinetics in hippocampal neurons

    PubMed Central

    Gu, Xinglong; Mao, Xia; Lussier, Marc P.; Hutchison, Mary Anne; Zhou, Liang; Hamra, F. Kent; Roche, Katherine W.; Lu, Wei

    2016-01-01

    Regulation of AMPA receptor (AMPAR)-mediated synaptic transmission is a key mechanism for synaptic plasticity. In the brain, AMPARs assemble with a number of auxiliary subunits, including TARPs, CNIHs and CKAMP44, which are important for AMPAR forward trafficking to synapses. Here we report that the membrane protein GSG1L negatively regulates AMPAR-mediated synaptic transmission. Overexpression of GSG1L strongly suppresses, and GSG1L knockout (KO) enhances, AMPAR-mediated synaptic transmission. GSG1L-dependent regulation of AMPAR synaptic transmission relies on the first extracellular loop domain and its carboxyl-terminus. GSG1L also speeds up AMPAR deactivation and desensitization in hippocampal CA1 neurons, in contrast to the effects of TARPs and CNIHs. Furthermore, GSG1L association with AMPARs inhibits CNIH2-induced slowing of the receptors in heterologous cells. Finally, GSG1L KO rats have deficits in LTP and show behavioural abnormalities in object recognition tests. These data demonstrate that GSG1L represents a new class of auxiliary subunit with distinct functional properties for AMPARs. PMID:26932439

  2. Extracellular Ca2+ depletion contributes to fast activity-dependent modulation of synaptic transmission in the brain.

    PubMed

    Rusakov, D A; Fine, A

    2003-01-23

    Synaptic activation is associated with rapid changes in intracellular Ca(2+), while the extracellular Ca(2+) level is generally assumed to be constant. Here, using a novel optical method to measure changes in extracellular Ca(2+) at high spatial and temporal resolution, we find that brief trains of synaptic transmission in hippocampal area CA1 induce transient depletion of extracellular Ca(2+). We show that this depletion, which depends on postsynaptic NMDA receptor activation, decreases the Ca(2+) available to enter individual presynaptic boutons of CA3 pyramidal cells. This in turn reduces the probability of consecutive synaptic releases at CA3-CA1 synapses and therefore contributes to short-term paired-pulse depression of minimal responses. This activity-dependent depletion of extracellular Ca(2+) represents a novel form of fast retrograde synaptic signaling that can modulate glutamatergic information transfer in the brain. PMID:12546823

  3. Extracellular Ca2+ Depletion Contributes to Fast Activity-Dependent Modulation of Synaptic Transmission in the Brain

    PubMed Central

    Rusakov, D.A.; Fine, A.

    2012-01-01

    Summary Synaptic activation is associated with rapid changes in intracellular Ca2+, while the extracellular Ca2+ level is generally assumed to be constant. Here, using a novel optical method to measure changes in extracellular Ca2+ at high spatial and temporal resolution, we find that brief trains of synaptic transmission in hippocampal area CA1 induce transient depletion of extracellular Ca2+. We show that this depletion, which depends on postsynaptic NMDA receptor activation, decreases the Ca2+ available to enter individual presynaptic boutons of CA3 pyramidal cells. This in turn reduces the probability of consecutive synaptic releases at CA3–CA1 synapses and therefore contributes to short-term paired-pulse depression of minimal responses. This activity-dependent depletion of extracellular Ca2+ represents a novel form of fast retrograde synaptic signaling that can modulate glutamatergic information transfer in the brain. PMID:12546823

  4. Synaptic Vesicle Proteins and Active Zone Plasticity

    PubMed Central

    Kittel, Robert J.; Heckmann, Manfred

    2016-01-01

    Neurotransmitter is released from synaptic vesicles at the highly specialized presynaptic active zone (AZ). The complex molecular architecture of AZs mediates the speed, precision and plasticity of synaptic transmission. Importantly, structural and functional properties of AZs vary significantly, even for a given connection. Thus, there appear to be distinct AZ states, which fundamentally influence neuronal communication by controlling the positioning and release of synaptic vesicles. Vice versa, recent evidence has revealed that synaptic vesicle components also modulate organizational states of the AZ. The protein-rich cytomatrix at the active zone (CAZ) provides a structural platform for molecular interactions guiding vesicle exocytosis. Studies in Drosophila have now demonstrated that the vesicle proteins Synaptotagmin-1 (Syt1) and Rab3 also regulate glutamate release by shaping differentiation of the CAZ ultrastructure. We review these unexpected findings and discuss mechanistic interpretations of the reciprocal relationship between synaptic vesicles and AZ states, which has heretofore received little attention. PMID:27148040

  5. Smaller Dendritic Spines, Weaker Synaptic Transmission, but Enhanced Spatial Learning in Mice Lacking Shank1

    PubMed Central

    Hung, Albert Y.; Futai, Kensuke; Sala, Carlo; Valtschanoff, Juli G.; Ryu, Jubin; Woodworth, Mollie A.; Kidd, Fleur L.; Sung, Clifford C.; Miyakawa, Tsuyoshi; Bear, Mark F.; Weinberg, Richard J.; Sheng, Morgan

    2009-01-01

    Experience-dependent changes in the structure of dendritic spines may contribute to learning and memory. Encoded by three genes, the Shank family of postsynaptic scaffold proteins are abundant and enriched in the postsynaptic density (PSD) of central excitatory synapses. When expressed in cultured hippocampal neurons, Shank promotes the maturation and enlargement of dendritic spines. Recently, Shank3 has been genetically implicated in human autism, suggesting an important role for Shank proteins in normal cognitive development. Here, we report the phenotype of Shank1 knock-out mice. Shank1 mutants showed altered PSD protein composition; reduced size of dendritic spines; smaller, thinner PSDs; and weaker basal synaptic transmission. Standard measures of synaptic plasticity were normal. Behaviorally, they had increased anxiety-related behavior and impaired contextual fear memory. Remarkably, Shank1-deficient mice displayed enhanced performance in a spatial learning task; however, their long-term memory retention in this task was impaired. These results affirm the importance of Shank1 for synapse structure and function in vivo, and they highlight a differential role for Shank1 in specific cognitive processes, a feature that may be relevant to human autism spectrum disorders. PMID:18272690

  6. LAMP5 Fine-Tunes GABAergic Synaptic Transmission in Defined Circuits of the Mouse Brain

    PubMed Central

    Tiveron, Marie-Catherine; Beurrier, Corinne; Céni, Claire; Andriambao, Naly; Combes, Alexis; Koehl, Muriel; Maurice, Nicolas; Gatti, Evelina; Abrous, Dhoher Nora; Kerkerian-Le Goff, Lydia; Pierre, Philippe; Cremer, Harold

    2016-01-01

    LAMP5 is member of the LAMP family of membrane proteins. In contrast to the canonical members of this protein family, LAMP1 and LAMP2, which show widespread expression in many tissues, LAMP 5 is brain specific in mice. In C. elegans, the LAMP5 ortholog UNC-46 has been suggested to act a trafficking chaperone, essential for the correct targeting of the nematode vesicular GABA-transporter UNC-47. We show here that in the mouse brain LAMP5 is expressed in subpopulations of GABAergic forebrain neurons in the striato-nigral system and the olfactory bulb. The protein was present at synaptic terminals, overlapping with the mammalian vesicular GABA-transporter VGAT. In LAMP5-deficient mice localization of the transporter was unaffected arguing against a conserved role in VGAT trafficking. Electrophysiological analyses in mutants showed alterations in short term synaptic plasticity suggesting that LAMP5 is involved in controlling the dynamics of evoked GABAergic transmission. At the behavioral level, LAMP5 mutant mice showed decreased anxiety and deficits in olfactory discrimination. Altogether, this work implicates LAMP5 function in GABAergic neurotransmission in defined neuronal subpopulations. PMID:27272053

  7. The neurotoxin 1-methyl-4-phenylpyridinium (MPP(+)) alters hippocampal excitatory synaptic transmission by modulation of the GABAergic system.

    PubMed

    Huang, YuYing; Chen, JunFang; Chen, Ying; Zhuang, YingHan; Sun, Mu; Behnisch, Thomas

    2015-01-01

    The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induces Parkinson's disease-like symptoms following administration to mice, monkeys, and humans. A common view is that MPTP is metabolized to 1-methyl-4-phenylpyridinium ion (MPP(+)) to induce its neurodegenerative effects on dopaminergic neurons in the substantia nigra (SN). Moreover, the hippocampus contains dopaminergic fibers, which are projecting from the ventral tegmental area, SN and pars compacta and contain the whole machinery required for dopamine synthesis making them sensitive to MPTP and MPP(+). Here, we present data showing that acute bath-application of MPP(+) elicited a dose-dependent facilitation followed by a depression of synaptic transmission of hippocampal Schaffer collaterals-CA1 synapses in mice. The effects of MPP(+) were not mediated by D1/D5- and D2-like receptor activation. Inhibition of the dopamine transporters did not prevent but increased the depression of excitatory post-synaptic field potentials. In the search for a possible mechanism, we observed that MPP(+) reduced the appearance of polyspikes in population spikes recorded in str. pyramidale and increased the frequency of miniature inhibitory post-synaptic currents. The acute effect of MPP(+) on synaptic transmission was attenuated by co-application of a GABAA receptor antagonist. Taking these data together, we suggest that MPP(+) affects hippocampal synaptic transmission by enhancing some aspects of the hippocampal GABAergic system. PMID:26300734

  8. A transducible nuclear/nucleolar protein, mLLP, regulates neuronal morphogenesis and synaptic transmission

    PubMed Central

    Yu, Nam-Kyung; Kim, Hyoung F.; Shim, Jaehoon; Kim, Somi; Kim, Dae Won; Kwak, Chuljung; Sim, Su-Eon; Choi, Jun-Hyeok; Ahn, Seohee; Yoo, Juyoun; Choi, Sun-Lim; Jang, Deok-Jin; Lim, Chae-Seok; Lee, Yong-Seok; Kang, Chulhun; Choi, Soo Young; Kaang, Bong-Kiun

    2016-01-01

    Cell-permeable proteins are emerging as unconventional regulators of signal transduction and providing a potential for therapeutic applications. However, only a few of them are identified and studied in detail. We identify a novel cell-permeable protein, mouse LLP homolog (mLLP), and uncover its roles in regulating neural development. We found that mLLP is strongly expressed in developing nervous system and that mLLP knockdown or overexpression during maturation of cultured neurons affected the neuronal growth and synaptic transmission. Interestingly, extracellular addition of mLLP protein enhanced dendritic arborization, demonstrating the non-cell-autonomous effect of mLLP. Moreover, mLLP interacts with CCCTC-binding factor (CTCF) as well as transcriptional machineries and modulates gene expression involved in neuronal growth. Together, these results illustrate the characteristics and roles of previously unknown cell-permeable protein mLLP in modulating neural development. PMID:26961175

  9. Mitochondrial reactive oxygen species regulate the strength of inhibitory GABA-mediated synaptic transmission

    PubMed Central

    Accardi, Michael V.; Daniels, Bryan A.; Brown, Patricia M.G.E.; Fritschy, Jean-Marc; Tyagarajan, Shiva K.; Bowie, Derek

    2016-01-01

    Neuronal communication imposes a heavy metabolic burden in maintaining ionic gradients essential for action potential firing and synaptic signaling. Although cellular metabolism is known to regulate excitatory neurotransmission, it is still unclear whether the brain’s energy supply affects inhibitory signaling. Here we show that mitochondrial-derived reactive oxygen species (mROS) regulate the strength of postsynaptic GABAA receptors at inhibitory synapses of cerebellar stellate cells. Inhibition is strengthened through a mechanism that selectively recruits α3-containing GABAA receptors into synapses with no discernible effect on resident α1-containing receptors. Since mROS promotes the emergence of postsynaptic events with unique kinetic properties, we conclude that newly-recruited α3-containing GABAA receptors are activated by neurotransmitter released onto discrete postsynaptic sites. Although traditionally associated with oxidative stress in neurodegenerative disease, our data identifies mROS as a putative homeostatic signaling molecule coupling cellular metabolism to the strength of inhibitory transmission. PMID:24430741

  10. High-frequency electroacupuncture evidently reinforces hippocampal synaptic transmission in Alzheimer's disease rats

    PubMed Central

    Li, Wei; Kong, Li-hong; Wang, Hui; Shen, Feng; Wang, Ya-wen; Zhou, Hua; Sun, Guo-jie

    2016-01-01

    The frequency range of electroacupuncture in treatment of Alzheimer's disease in rats is commonly 2–5 Hz (low frequency) and 50–100 Hz (high frequency). We established a rat model of Alzheimer's disease by injecting β-amyloid 1–42 (Aβ1–42) into the bilateral hippocampal dentate gyrus to verify which frequency may be better suited in treatment. Electroacupuncture at 2 Hz or 50 Hz was used to stimulate Baihui (DU20) and Shenshu (BL23) acupoints. The water maze test and electrophysiological studies demonstrated that spatial memory ability was apparently improved, and the ranges of long-term potentiation and long-term depression were increased in Alzheimer's disease rats after electroacupuncture treatment. Moreover, the effects of electroacupuncture at 50 Hz were better than that at 2 Hz. These findings suggest that high-frequency electroacupuncture may enhance hippocampal synaptic transmission and potentially improve memory disorders in Alzheimer's disease rats. PMID:27335565

  11. A transducible nuclear/nucleolar protein, mLLP, regulates neuronal morphogenesis and synaptic transmission.

    PubMed

    Yu, Nam-Kyung; Kim, Hyoung F; Shim, Jaehoon; Kim, Somi; Kim, Dae Won; Kwak, Chuljung; Sim, Su-Eon; Choi, Jun-Hyeok; Ahn, Seohee; Yoo, Juyoun; Choi, Sun-Lim; Jang, Deok-Jin; Lim, Chae-Seok; Lee, Yong-Seok; Kang, Chulhun; Choi, Soo Young; Kaang, Bong-Kiun

    2016-01-01

    Cell-permeable proteins are emerging as unconventional regulators of signal transduction and providing a potential for therapeutic applications. However, only a few of them are identified and studied in detail. We identify a novel cell-permeable protein, mouse LLP homolog (mLLP), and uncover its roles in regulating neural development. We found that mLLP is strongly expressed in developing nervous system and that mLLP knockdown or overexpression during maturation of cultured neurons affected the neuronal growth and synaptic transmission. Interestingly, extracellular addition of mLLP protein enhanced dendritic arborization, demonstrating the non-cell-autonomous effect of mLLP. Moreover, mLLP interacts with CCCTC-binding factor (CTCF) as well as transcriptional machineries and modulates gene expression involved in neuronal growth. Together, these results illustrate the characteristics and roles of previously unknown cell-permeable protein mLLP in modulating neural development. PMID:26961175

  12. Synaptic transmission from rods to rod-dominated bipolar cells in the tiger salamander retina.

    PubMed

    Yang, X L; Wu, S M

    1993-06-11

    Synaptic transmission between photoreceptors and bipolar cells was studied in dark-adapted tiger salamander retinas. Based on the relative light sensitivity, bipolar cells, either depolarizing (DBC) or hyperpolarizing (HBC), fell into two groups: one receives inputs primarily from rods (rod-dominated bipolar cells, DBCR and HBCR) and the other receives inputs primarily from cones (cone-dominated bipolar cells, DBCC and HBCC). The input-output relations of the rod-DBCR and rod-HBCR synapses were determined by plotting the voltage responses of the rod and DBCR (or HBCR) to dim 500-nm light steps, which polarizes only the rods but not the cones. The slope gains of both synapses were the highest near the dark rod voltage (-2.5 for the rod-DBCR synapse and 4.0 for the rod-HBCR synapse), and they (the absolute values) became progressively smaller at more hyperpolarized rod voltages. PMID:8186975

  13. Mitochondrial reactive oxygen species regulate the strength of inhibitory GABA-mediated synaptic transmission

    NASA Astrophysics Data System (ADS)

    Accardi, Michael V.; Daniels, Bryan A.; Brown, Patricia M. G. E.; Fritschy, Jean-Marc; Tyagarajan, Shiva K.; Bowie, Derek

    2014-01-01

    Neuronal communication imposes a heavy metabolic burden in maintaining ionic gradients essential for action potential firing and synaptic signalling. Although cellular metabolism is known to regulate excitatory neurotransmission, it is still unclear whether the brain’s energy supply affects inhibitory signalling. Here we show that mitochondrial-derived reactive oxygen species (mROS) regulate the strength of postsynaptic GABAA receptors at inhibitory synapses of cerebellar stellate cells. Inhibition is strengthened through a mechanism that selectively recruits α3-containing GABAA receptors into synapses with no discernible effect on resident α1-containing receptors. Since mROS promotes the emergence of postsynaptic events with unique kinetic properties, we conclude that newly recruited α3-containing GABAA receptors are activated by neurotransmitter released onto discrete postsynaptic sites. Although traditionally associated with oxidative stress in neurodegenerative disease, our data identify mROS as a putative homeostatic signalling molecule coupling cellular metabolism to the strength of inhibitory transmission.

  14. Organization of synaptic transmission in the mammalian solitary complex, studied in vitro.

    PubMed Central

    Champagnat, J; Denavit-Saubié, M; Grant, K; Shen, K F

    1986-01-01

    1. Synaptic transmission and neuronal morphology were studied in the nucleus tractus solitarius and in the dorsal vagal motor nucleus (solitary complex), in coronal brain-stem slices of rat or cat, superfused in vitro. 2. Electrical stimulation of afferent fibres of the solitary tract evoked two different types of post-synaptic response recorded intracellularly in different solitary complex neurones. Labelling with horseradish peroxidase showed that these two sorts of orthodromically evoked responses were correlated with different post-synaptic neuronal morphologies. 3. The majority of recorded neurones (n = 93) showed a prolonged reduction in excitability following the initial solitary-tract-evoked excitatory post-synaptic potential (e.p.s.p.). A smaller number of neurones (n = 53) showed a prolonged increase in excitability following solitary tract stimulation. In no case did the solitary tract stimulation induce a burst of action potentials at high frequency. 4. The time-to-peak and the half-width of the initial solitary-tract-evoked e.p.s.p. were shorter in neurones with prolonged increased excitability than in those with prolonged reduced excitability. In neurones with prolonged reduced excitability, this e.p.s.p. was followed by a hyperpolarization lasting 60-100 ms. The latency of this inhibitory post-synaptic potential (i.p.s.p.) was 3-5 ms longer than that of the initial e.p.s.p. and its reversal potential was 10 mV more negative than the reversal potential of the response measured following application of gamma-aminobutyric acid or glycine. In neurones with prolonged increased excitability, at a membrane potential of -40 to -50 mV, the initial solitary tract e.p.s.p. was followed by a prolonged depolarization lasting 100-400 ms. 5. Background synaptic activity was high in neurones with prolonged increased excitability, consisting of unitary e.p.s.p.s with an amplitude of more than 0.8 mV. This activity was increased for a period of 300-800 ms following

  15. Propagation of Epileptiform Activity Can Be Independent of Synaptic Transmission, Gap Junctions, or Diffusion and Is Consistent with Electrical Field Transmission

    PubMed Central

    Zhang, Mingming; Ladas, Thomas P.; Qiu, Chen; Shivacharan, Rajat S.; Gonzalez-Reyes, Luis E.

    2014-01-01

    The propagation of activity in neural tissue is generally associated with synaptic transmission, but epileptiform activity in the hippocampus can propagate with or without synaptic transmission at a speed of ∼0.1 m/s. This suggests an underlying common nonsynaptic mechanism for propagation. To study this mechanism, we developed a novel unfolded hippocampus preparation, from CD1 mice of either sex, which preserves the transverse and longitudinal connections and recorded activity with a penetrating microelectrode array. Experiments using synaptic transmission and gap junction blockers indicated that longitudinal propagation is independent of chemical or electrical synaptic transmission. Propagation speeds of 0.1 m/s are not compatible with ionic diffusion or pure axonal conduction. The only other means of communication between neurons is through electric fields. Computer simulations revealed that activity can indeed propagate from cell to cell solely through field effects. These results point to an unexpected propagation mechanism for neural activity in the hippocampus involving endogenous field effect transmission. PMID:24453330

  16. New tools for targeted disruption of cholinergic synaptic transmission in Drosophila melanogaster.

    PubMed

    Mejia, Monica; Heghinian, Mari D; Marí, Frank; Godenschwege, Tanja A

    2013-01-01

    Nicotinic acetylcholine receptors (nAChRs) are pentameric ligand-gated ion channels. The α7 subtype of nAChRs is involved in neurological pathologies such as Parkinson's disease, Alzheimer's disease, addiction, epilepsy and autism spectrum disorders. The Drosophila melanogaster α7 (Dα7) has the closest sequence homology to the vertebrate α7 subunit and it can form homopentameric receptors just as the vertebrate counterpart. The Dα7 subunits are essential for the function of the Giant Fiber circuit, which mediates the escape response of the fly. To further characterize the receptor function, we generated different missense mutations in the Dα7 nAChR's ligand binding domain. We characterized the effects of targeted expression of two UAS-constructs carrying a single mutation, D197A and Y195T, as well as a UAS-construct carrying a triple D77T, L117Q, I196P mutation in a Dα7 null mutant and in a wild type background. Expression of the triple mutation was able to restore the function of the circuit in Dα7 null mutants and had no disruptive effects when expressed in wild type. In contrast, both single mutations severely disrupted the synaptic transmission of Dα7-dependent but not glutamatergic or gap junction dependent synapses in wild type background, and did not or only partially rescued the synaptic defects of the null mutant. These observations are consistent with the formation of hybrid receptors, consisting of D197A or Y195T subunits and wild type Dα7 subunits, in which the binding of acetylcholine or acetylcholine-induced conformational changes of the Dα7 receptor are altered and causes inhibition of cholinergic responses. Thus targeted expression of D197A or Y195T can be used to selectively disrupt synaptic transmission of Dα7-dependent synapses in neuronal circuits. Hence, these constructs can be used as tools to study learning and memory or addiction associated behaviors by allowing the manipulation of neuronal processing in the circuits without

  17. TRPV1 receptors augment basal synaptic transmission in CA1 and CA3 pyramidal neurons in epilepsy.

    PubMed

    Saffarzadeh, F; Eslamizade, M J; Mousavi, S M M; Abraki, S B; Hadjighassem, M R; Gorji, A

    2016-02-01

    Temporal lobe epilepsy in human and animals is attributed to alterations in brain function especially hippocampus formation. Changes in synaptic activity might be causally related to the alterations during epileptogenesis. Transient receptor potential vanilloid 1 (TRPV1) as one of the non-selective ion channels has been shown to be involved in synaptic transmission. However, the potential role of TRPV1 receptors in synaptic function in the epileptic brain needs to be elucidated. In the present study, we used quantitative real-time PCR (qRT-PCR), western blotting, and immunohistochemistry to assess hippocampal TRPV1 mRNA expression, protein content, and distribution. Moreover, the effects of pharmacologic activation and inhibition of TRPV1 receptors on the slope of evoked field excitatory postsynaptic potentials (fEPSPs) were analyzed in CA1 and CA3 pyramidal neurons, after 3months of pilocarpine-induced status epilepticus (SE). SE induced an upregulation of TRPV1 mRNA and protein content in the whole hippocampal extract, as well as its distribution in both CA1 and CA3 regions. Activation and inhibition of TRPV1 receptors (via capsaicin 1μM and capsazepine 10μM, respectively) did not influence basal synaptic transmission in CA1 and CA3 regions of control slices, however, capsaicin increased and capsazepine decreased synaptic transmission in both regions in tissues from epileptic animals. Taken together, these findings suggest that a higher expression of TRPV1 in the epileptic condition is accompanied by alterations in basal synaptic transmission. PMID:26621124

  18. DAMGO depresses inhibitory synaptic transmission via different downstream pathways of μ opioid receptors in ventral tegmental area and periaqueductal gray.

    PubMed

    Zhang, W; Yang, H L; Song, J J; Chen, M; Dong, Y; Lai, B; Yu, Y G; Ma, L; Zheng, P

    2015-08-20

    Opioid-induced rewarding and motorstimulant effects are mediated by an increased activity of the ventral tegmental area (VTA) dopamine (DA) neurons. The excitatory mechanism of opioids on VTA-DA neurons has been proposed to be due to the depression of GABAergic synaptic transmission in VTA-DA neurons. However, how opioids depress GABAergic synaptic transmission in VTA-DA neurons remain to be studied. In the present study, we explored the mechanism of the inhibitory effect of [D-Ala(2), N-Me-Phe(4), Gly(5)-ol]-enkephalin (DAMGO) on GABAergic synaptic transmission in VTA-DA neurons using multiple approaches and techniques. Our results showed that (1) DAMGO inhibits GABAergic inputs in VTA-DA neurons at presynaptic sites; (2) effect of DAMGO on GABAergic inputs in VTA-DA neurons is inhibited by potassium channel blocker 4-aminopyridine (4-AP) and Gi protein inhibitor N-ethylmaleimide (NEM); (3) phospholipase A2 (PLA2) does not mediate the effect of DAMGO on GABAergic inputs in VTA-DA neurons, but mediates it in the periaqueductal gray (PAG); (4) multiple downstream signaling molecules of μ receptors do not mediate the effect of DAMGO on GABAergic inputs in VTA-DA neurons. These results suggest that DAMGO depresses inhibitory synaptic transmission via μ receptor-Gi protein-Kv channel pathway in VTA-DA neurons, but via μ receptor-PLA2 pathway in PAG neurons. PMID:26047721

  19. Bidirectional regulation of synaptic plasticity in the basolateral amygdala induced by the D1-like family of dopamine receptors and group II metabotropic glutamate receptors

    PubMed Central

    Li, Chenchen; Rainnie, Donald G

    2014-01-01

    Competing mechanisms of long-term potentiation (LTP) and long-term depression (LTD) in principal neurons of the basolateral amygdala (BLA) are thought to underlie the acquisition and consolidation of fear memories, and their subsequent extinction. However, no study to date has examined the locus of action and/or the cellular mechanism(s) by which these processes interact. Here, we report that synaptic plasticity in the cortical pathway onto BLA principal neurons is frequency-dependent and shows a transition from LTD to LTP at stimulation frequencies of ∼10 Hz. At the crossover point from LTD to LTP induction we show that concurrent activation of D1 and group II metabotropic glutamate (mGluR2/3) receptors act to nullify any net change in synaptic strength. Significantly, blockade of either D1 or mGluR2/3 receptors unmasked 10 Hz stimulation-induced LTD and LTP, respectively. Significantly, prior activation of presynaptic D1 receptors caused a time-dependent attenuation of mGluR2/3-induced depotentiation of previously induced LTP. Furthermore, studies with cell type-specific postsynaptic transgene expression of designer receptors activated by designer drugs (DREADDs) suggest that the interaction results via bidirectional modulation of adenylate cyclase activity in presynaptic glutamatergic terminals. The results of our study raise the possibility that the temporal sequence of activation of either presynaptic D1 receptors or mGluR2/3 receptors may critically regulate the direction of synaptic plasticity in afferent pathways onto BLA principal neurons. Hence, the interaction of these two neurotransmitter systems may represent an important mechanism for bidirectional metaplasticity in BLA circuits and thus modulate the acquisition and extinction of fear memory. PMID:25107924

  20. Bidirectional regulation of synaptic plasticity in the basolateral amygdala induced by the D1-like family of dopamine receptors and group II metabotropic glutamate receptors.

    PubMed

    Li, Chenchen; Rainnie, Donald G

    2014-10-01

    Competing mechanisms of long-term potentiation (LTP) and long-term depression (LTD) in principal neurons of the basolateral amygdala (BLA) are thought to underlie the acquisition and consolidation of fear memories, and their subsequent extinction. However, no study to date has examined the locus of action and/or the cellular mechanism(s) by which these processes interact. Here, we report that synaptic plasticity in the cortical pathway onto BLA principal neurons is frequency-dependent and shows a transition from LTD to LTP at stimulation frequencies of ∼10 Hz. At the crossover point from LTD to LTP induction we show that concurrent activation of D1 and group II metabotropic glutamate (mGluR2/3) receptors act to nullify any net change in synaptic strength. Significantly, blockade of either D1 or mGluR2/3 receptors unmasked 10 Hz stimulation-induced LTD and LTP, respectively. Significantly, prior activation of presynaptic D1 receptors caused a time-dependent attenuation of mGluR2/3-induced depotentiation of previously induced LTP. Furthermore, studies with cell type-specific postsynaptic transgene expression of designer receptors activated by designer drugs (DREADDs) suggest that the interaction results via bidirectional modulation of adenylate cyclase activity in presynaptic glutamatergic terminals. The results of our study raise the possibility that the temporal sequence of activation of either presynaptic D1 receptors or mGluR2/3 receptors may critically regulate the direction of synaptic plasticity in afferent pathways onto BLA principal neurons. Hence, the interaction of these two neurotransmitter systems may represent an important mechanism for bidirectional metaplasticity in BLA circuits and thus modulate the acquisition and extinction of fear memory. PMID:25107924

  1. D1R/GluN1 complexes in the striatum integrate dopamine and glutamate signalling to control synaptic plasticity and cocaine-induced responses.

    PubMed

    Cahill, E; Pascoli, V; Trifilieff, P; Savoldi, D; Kappès, V; Lüscher, C; Caboche, J; Vanhoutte, P

    2014-12-01

    Convergent dopamine and glutamate signalling onto the extracellular signal-regulated kinase (ERK) pathway in medium spiny neurons (MSNs) of the striatum controls psychostimulant-initiated adaptive processes underlying long-lasting behavioural changes. We hypothesised that the physical proximity of dopamine D1 (D1R) and glutamate NMDA (NMDAR) receptors, achieved through the formation of D1R/NMDAR complexes, may act as a molecular bridge that controls the synergistic action of dopamine and glutamate on striatal plasticity and behavioural responses to drugs of abuse. We found that concomitant stimulation of D1R and NMDAR drove complex formation between endogenous D1R and the GluN1 subunit of NMDAR. Conversely, preventing D1R/GluN1 association with a cell-permeable peptide (TAT-GluN1C1) left individual D1R and NMDAR-dependent signalling intact, but prevented D1R-mediated facilitation of NMDAR-calcium influx and subsequent ERK activation. Electrophysiological recordings in striatal slices from mice revealed that D1R/GluN1 complexes control the D1R-dependent enhancement of NMDAR currents and long-term potentiation in D1R-MSN. Finally, intra-striatal delivery of TAT-GluN1C1 did not affect acute responses to cocaine but reduced behavioural sensitization. Our findings uncover D1R/GluN1 complexes as a major substrate for the dopamine-glutamate interaction in MSN that is usurped by addictive drugs to elicit persistent behavioural alterations. They also identify D1R/GluN1 complexes as molecular targets with a therapeutic potential for the vast spectrum of psychiatric diseases associated with an imbalance between dopamine and glutamate transmission. PMID:25070539

  2. Syncrip/hnRNP Q influences synaptic transmission and regulates BMP signaling at the Drosophila neuromuscular synapse

    PubMed Central

    Halstead, James M.; Lin, Yong Qi; Durraine, Lita; Hamilton, Russell S.; Ball, Graeme; Neely, Greg G.; Bellen, Hugo J.; Davis, Ilan

    2014-01-01

    ABSTRACT Synaptic plasticity involves the modulation of synaptic connections in response to neuronal activity via multiple pathways. One mechanism modulates synaptic transmission by retrograde signals from the post-synapse that influence the probability of vesicle release in the pre-synapse. Despite its importance, very few factors required for the expression of retrograde signals, and proper synaptic transmission, have been identified. Here, we identify the conserved RNA binding protein Syncrip as a new factor that modulates the efficiency of vesicle release from the motoneuron and is required for correct synapse structure. We show that syncrip is required genetically and its protein product is detected only in the muscle and not in the motoneuron itself. This unexpected non-autonomy is at least partly explained by the fact that Syncrip modulates retrograde BMP signals from the muscle back to the motoneuron. We show that Syncrip influences the levels of the Bone Morphogenic Protein ligand Glass Bottom Boat from the post-synapse and regulates the pre-synapse. Our results highlight the RNA-binding protein Syncrip as a novel regulator of synaptic output. Given its known role in regulating translation, we propose that Syncrip is important for maintaining a balance between the strength of presynaptic vesicle release and postsynaptic translation. PMID:25171887

  3. Expression and plasticity of glutamate receptors in the supraoptic nucleus of the hypothalamus.

    PubMed

    Pak, C Wook; Currás-Collazo, Margarita C

    2002-01-15

    Magnocellular neuroendocrine cells (MNCs) of the supraoptic nucleus of the hypothalamus (SON) produce and release the hormones vasopressin (VP) and oxytocin (OT) in response to a variety of stimuli to regulate body water and salt, parturition and lactation. Hormone release is influenced by the pattern of neuronal firing of these MNCs, which, in turn, is governed by intrinsic conductances and synaptic inputs, including those mediated by the neurotransmitter glutamate. Functional and molecular evidence has confirmed the expression of AMPA-, NMDA-, and metabotropic-type glutamate receptors in the SON, that together may orchestrate the effects of glutamatergic transmission on neuroendocrine function. However, the specific roles of the different subtypes of glutamate receptors is not yet clear. As with other central neurons, the subunit composition of glutamate receptors on MNCs will likely determine their properties and may potentially help define the differential properties of VP- and OT-producing MNCs. Possible functions of glutamate receptors on SON MNCs include altering excitatory synaptic transmission of osmotic information, neuronal firing, hormone production and release, and calcium signaling. Of interest are the anatomical, molecular, and functional changes at glutamatergic synapses in the SON that occur in response to pertinent physiological stimuli or development. These types of plasticity may include changes in glutamatergic synaptic density, glutamate receptor levels, or glutamate receptor subunit expression, all of which can affect the efficiency of synaptic transmission. PMID:11810712

  4. Potentiation of synaptic transmission in Rat anterior cingulate cortex by chronic itch.

    PubMed

    Zhang, Ting-Ting; Shen, Feng-Yan; Ma, Li-Qing; Wen, Wen; Wang, Bin; Peng, Yuan-Zhi; Wang, Zhi-Ru; Zhao, Xuan

    2016-01-01

    Itch and pain share similar mechanisms. It has been well documented that the anterior cingulate cortex (ACC) is important for pain-related perception. ACC has also been approved to be a potential pruritus-associated brain region. However, the mechanism of sensitization in pruriceptive neurons in the ACC is not clear. In current study, a chronic itch model was established by diphenylcyclopropenone (DCP) application. We found that both the frequency and amplitude of miniature excitatory postsynaptic currents in the ACC were enhanced after the formation of chronic itch. The paired-pulse ratio in ACC neurons recorded from the DCP group were smaller than those recorded in control group at the 50-ms interval. We also observe a significant increase in the AMPA/NMDA ratio in the DCP group. Moreover, an increased inward rectification of AMPARs in ACC pyramidal neurons was observed in the DCP group. Interestingly, the calculated ratio of silent synapses was significantly reduced in the DCP group compared with controls. Taken together, we conclude that a potentiation of synaptic transmission in the ACC can be induced by chronic itch, and unsilencing silent synapses, which probably involved recruitment of AMPARS, contributed to the potentiation of postsynaptic transmission. PMID:27472923

  5. Stochastic resonance in the synaptic transmission between hair cells and vestibular primary afferents in development.

    PubMed

    Flores, A; Manilla, S; Huidobro, N; De la Torre-Valdovinos, B; Kristeva, R; Mendez-Balbuena, I; Galindo, F; Treviño, M; Manjarrez, E

    2016-05-13

    The stochastic resonance (SR) is a phenomenon of nonlinear systems in which the addition of an intermediate level of noise improves the response of such system. Although SR has been studied in isolated hair cells and in the bullfrog sacculus, the occurrence of this phenomenon in the vestibular system in development is unknown. The purpose of the present study was to explore for the existence of SR via natural mechanical-stimulation in the hair cell-vestibular primary afferent transmission. In vitro experiments were performed on the posterior semicircular canal of the chicken inner ear during development. Our experiments showed that the signal-to-noise ratio of the afferent multiunit activity from E15 to P5 stages of development exhibited the SR phenomenon, which was characterized by an inverted U-like response as a function of the input noise level. The inverted U-like graphs of SR acquired their higher amplitude after the post-hatching stage of development. Blockage of the synaptic transmission with selective antagonists of the NMDA and AMPA/Kainate receptors abolished the SR of the afferent multiunit activity. Furthermore, computer simulations on a model of the hair cell - primary afferent synapse qualitatively reproduced this SR behavior and provided a possible explanation of how and where the SR could occur. These results demonstrate that a particular level of mechanical noise on the semicircular canals can improve the performance of the vestibular system in their peripheral sensory processing even during embryonic stages of development. PMID:26926966

  6. Recording long-term potentiation of synaptic transmission by three-dimensional multi-electrode arrays

    PubMed Central

    Kopanitsa, Maksym V; Afinowi, Nurudeen O; Grant, Seth GN

    2006-01-01

    Background Multi-electrode arrays (MEAs) have become popular tools for recording spontaneous and evoked electrical activity of excitable tissues. The majority of previous studies of synaptic transmission in brain slices employed MEAs with planar electrodes that had limited ability to detect signals coming from deeper, healthier layers of the slice. To overcome this limitation, we used three-dimensional (3D) MEAs with tip-shaped electrodes to probe plasticity of field excitatory synaptic potentials (fEPSPs) in the CA1 area of hippocampal slices of 129S5/SvEvBrd and C57BL/6J-TyrC-Brd mice. Results Using 3D MEAs, we were able to record larger fEPSPs compared to signals measured by planar MEAs. Several stimulation protocols were used to induce long-term potentiation (LTP) of synaptic responses in the CA1 area recorded following excitation of Schäffer collateral/commissural fibres. Either two trains of high frequency tetanic stimulation or three trains of theta-burst stimulation caused a persistent, pathway specific enhancement of fEPSPs that remained significantly elevated for at least 60 min. A third LTP induction protocol that comprised 150 pulses delivered at 5 Hz, evoked moderate LTP if excitation strength was increased to 1.5× of the baseline stimulus. In all cases, we observed a clear spatial plasticity gradient with maximum LTP levels detected in proximal apical dendrites of pyramidal neurones. No significant differences in the manifestation of LTP were observed between 129S5/SvEvBrd and C57BL/6J-TyrC-Brd mice with the three protocols used. All forms of plasticity were sensitive to inhibition of N-methyl-D-aspartate (NMDA) receptors. Conclusion Principal features of LTP (magnitude, pathway specificity, NMDA receptor dependence) recorded in the hippocampal slices using MEAs were very similar to those seen in conventional glass electrode experiments. Advantages of using MEAs are the ability to record from different regions of the slice and the ease of conducting

  7. De Novo Mutations in Synaptic Transmission Genes Including DNM1 Cause Epileptic Encephalopathies

    PubMed Central

    Appenzeller, Silke; Balling, Rudi; Barisic, Nina; Baulac, Stéphanie; Caglayan, Hande; Craiu, Dana; De Jonghe, Peter; Depienne, Christel; Dimova, Petia; Djémié, Tania; Gormley, Padhraig; Guerrini, Renzo; Helbig, Ingo; Hjalgrim, Helle; Hoffman-Zacharska, Dorota; Jähn, Johanna; Klein, Karl Martin; Koeleman, Bobby; Komarek, Vladimir; Krause, Roland; Kuhlenbäumer, Gregor; Leguern, Eric; Lehesjoki, Anna-Elina; Lemke, Johannes R.; Lerche, Holger; Linnankivi, Tarja; Marini, Carla; May, Patrick; Møller, Rikke S.; Muhle, Hiltrud; Pal, Deb; Palotie, Aarno; Pendziwiat, Manuela; Robbiano, Angela; Roelens, Filip; Rosenow, Felix; Selmer, Kaja; Serratosa, Jose M.; Sisodiya, Sanjay; Stephani, Ulrich; Sterbova, Katalin; Striano, Pasquale; Suls, Arvid; Talvik, Tiina; von Spiczak, Sarah; Weber, Yvonne; Weckhuysen, Sarah; Zara, Federico; Abou-Khalil, Bassel; Alldredge, Brian K.; Andermann, Eva; Andermann, Frederick; Amron, Dina; Bautista, Jocelyn F.; Berkovic, Samuel F.; Bluvstein, Judith; Boro, Alex; Cascino, Gregory; Consalvo, Damian; Crumrine, Patricia; Devinsky, Orrin; Dlugos, Dennis; Epstein, Michael P.; Fiol, Miguel; Fountain, Nathan B.; French, Jacqueline; Friedman, Daniel; Geller, Eric B.; Glauser, Tracy; Glynn, Simon; Haas, Kevin; Haut, Sheryl R.; Hayward, Jean; Helmers, Sandra L.; Joshi, Sucheta; Kanner, Andres; Kirsch, Heidi E.; Knowlton, Robert C.; Kossoff, Eric H.; Kuperman, Rachel; Kuzniecky, Ruben; Lowenstein, Daniel H.; McGuire, Shannon M.; Motika, Paul V.; Novotny, Edward J.; Ottman, Ruth; Paolicchi, Juliann M.; Parent, Jack; Park, Kristen; Poduri, Annapurna; Sadleir, Lynette; Scheffer, Ingrid E.; Shellhaas, Renée A.; Sherr, Elliott; Shih, Jerry J.; Singh, Rani; Sirven, Joseph; Smith, Michael C.; Sullivan, Joe; Thio, Liu Lin; Venkat, Anu; Vining, Eileen P.G.; Von Allmen, Gretchen K.; Weisenberg, Judith L.; Widdess-Walsh, Peter; Winawer, Melodie R.; Allen, Andrew S.; Berkovic, Samuel F.; Cossette, Patrick; Delanty, Norman; Dlugos, Dennis; Eichler, Evan E.; Epstein, Michael P.; Glauser, Tracy; Goldstein, David B.; Han, Yujun; Heinzen, Erin L.; Johnson, Michael R.; Kuzniecky, Ruben; Lowenstein, Daniel H.; Marson, Anthony G.; Mefford, Heather C.; Nieh, Sahar Esmaeeli; O’Brien, Terence J.; Ottman, Ruth; Petrou, Stephen; Petrovski, Slavé; Poduri, Annapurna; Ruzzo, Elizabeth K.; Scheffer, Ingrid E.; Sherr, Elliott

    2014-01-01

    Emerging evidence indicates that epileptic encephalopathies are genetically highly heterogeneous, underscoring the need for large cohorts of well-characterized individuals to further define the genetic landscape. Through a collaboration between two consortia (EuroEPINOMICS and Epi4K/EPGP), we analyzed exome-sequencing data of 356 trios with the “classical” epileptic encephalopathies, infantile spasms and Lennox Gastaut syndrome, including 264 trios previously analyzed by the Epi4K/EPGP consortium. In this expanded cohort, we find 429 de novo mutations, including de novo mutations in DNM1 in five individuals and de novo mutations in GABBR2, FASN, and RYR3 in two individuals each. Unlike previous studies, this cohort is sufficiently large to show a significant excess of de novo mutations in epileptic encephalopathy probands compared to the general population using a likelihood analysis (p = 8.2 × 10−4), supporting a prominent role for de novo mutations in epileptic encephalopathies. We bring statistical evidence that mutations in DNM1 cause epileptic encephalopathy, find suggestive evidence for a role of three additional genes, and show that at least 12% of analyzed individuals have an identifiable causal de novo mutation. Strikingly, 75% of mutations in these probands are predicted to disrupt a protein involved in regulating synaptic transmission, and there is a significant enrichment of de novo mutations in genes in this pathway in the entire cohort as well. These findings emphasize an important role for synaptic dysregulation in epileptic encephalopathies, above and beyond that caused by ion channel dysfunction. PMID:25262651

  8. Vibrodissociation of Neurons from Rodent Brain Slices to Study Synaptic Transmission and Image Presynaptic Terminals

    PubMed Central

    Jun, Sang Beom; Cuzon Carlson, Verginia; Ikeda, Stephen; Lovinger, David

    2011-01-01

    Mechanical dissociation of neurons from the central nervous system has the advantage that presynaptic boutons remain attached to the isolated neuron of interest. This allows for examination of synaptic transmission under conditions where the extracellular and postsynaptic intracellular environments can be well controlled. A vibration-based technique without the use of proteases, known as vibrodissociation, is the most popular technique for mechanical isolation. A micropipette, with the tip fire-polished to the shape of a small ball, is placed into a brain slice made from a P1-P21 rodent. The micropipette is vibrated parallel to the slice surface and lowered through the slice thickness resulting in the liberation of isolated neurons. The isolated neurons are ready for study within a few minutes of vibrodissociation. This technique has advantages over the use of primary neuronal cultures, brain slices and enzymatically isolated neurons including: rapid production of viable, relatively mature neurons suitable for electrophysiological and imaging studies; superior control of the extracellular environment free from the influence of neighboring cells; suitability for well-controlled pharmacological experiments using rapid drug application and total cell superfusion; and improved space-clamp in whole-cell recordings relative to neurons in slice or cell culture preparations. This preparation can be used to examine synaptic physiology, pharmacology, modulation and plasticity. Real-time imaging of both pre- and postsynaptic elements in the living cells and boutons is also possible using vibrodissociated neurons. Characterization of the molecular constituents of pre- and postsynaptic elements can also be achieved with immunological and imaging-based approaches. PMID:21654624

  9. Brain-derived neurotrophic factor and nerve growth factor potentiate excitatory synaptic transmission in the rat visual cortex.

    PubMed Central

    Carmignoto, G; Pizzorusso, T; Tia, S; Vicini, S

    1997-01-01

    1. The effect of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) on excitatory synaptic transmission in the developing visual cortex was studied by whole-cell patch-clamp recordings from rat brain slices. 2. Both neurotrophins induced a rapid increase in the amplitude of impulse-evoked excitatory postsynaptic currents (EPSCs). BDNF also increased the frequency of spontaneous EPSCs. 3. Analysis of the currents revealed that alpha-amino-3-hydroxy-5-methyl-isoxazole propionic acid (AMPA) and N-methyl-D-aspartate (NMDA) receptor-mediated components contributing to the EPSC peak amplitude were equally potentiated by the neurotrophins. 4. When synaptic transmission was studied by minimal stimulation of intracortical afferents, neurotrophins induced a decrease in the occurrence of release failures. 5. A number of neurones were insensitive to the effects of the neurotrophins, possibly related to the considerable heterogeneity of neuronal types and to the uneven distribution of neurotrophin receptors in the visual cortex. 6. The probability of neurotransmitter release represents a rapidly modifiable synaptic feature by which neurotrophins can potentiate the efficacy of excitatory synaptic transmission in the visual cortex. PMID:9023775

  10. Alteration of AMPA Receptor-Mediated Synaptic Transmission by Alexa Fluor 488 and 594 in Cerebellar Stellate Cells.

    PubMed

    Maroteaux, Matthieu; Liu, Siqiong June

    2016-01-01

    The fluorescent dyes, Alexa Fluor 488 and 594 are commonly used to visualize dendritic structures and the localization of synapses, both of which are critical for the spatial and temporal integration of synaptic inputs. However, the effect of the dyes on synaptic transmission is not known. Here we investigated whether Alexa Fluor dyes alter the properties of synaptic currents mediated by two subtypes of AMPA receptors (AMPARs) at cerebellar stellate cell synapses. In naive mice, GluA2-lacking AMPAR-mediated synaptic currents displayed an inwardly rectifying current-voltage (I-V) relationship due to blockade by cytoplasmic spermine at depolarized potentials. We found that the inclusion of 100 µm Alexa Fluor dye, but not 10 µm, in the pipette solution led to a gradual increase in the amplitude of EPSCs at +40 mV and a change in the I-V relationship from inwardly rectifying to more linear. In mice exposed to an acute stress, AMPARs switched to GluA2-containing receptors, and 100 µm Alexa Fluor 594 did not alter the I-V relationship of synaptic currents. Therefore, a high concentration of Alexa Fluor dye changed the I-V relationship of EPSCs at GluA2-lacking AMPAR synapses. PMID:27280156

  11. Alteration of AMPA Receptor-Mediated Synaptic Transmission by Alexa Fluor 488 and 594 in Cerebellar Stellate Cells123

    PubMed Central

    2016-01-01

    Abstract The fluorescent dyes, Alexa Fluor 488 and 594 are commonly used to visualize dendritic structures and the localization of synapses, both of which are critical for the spatial and temporal integration of synaptic inputs. However, the effect of the dyes on synaptic transmission is not known. Here we investigated whether Alexa Fluor dyes alter the properties of synaptic currents mediated by two subtypes of AMPA receptors (AMPARs) at cerebellar stellate cell synapses. In naive mice, GluA2-lacking AMPAR-mediated synaptic currents displayed an inwardly rectifying current–voltage (I–V) relationship due to blockade by cytoplasmic spermine at depolarized potentials. We found that the inclusion of 100 µm Alexa Fluor dye, but not 10 µm, in the pipette solution led to a gradual increase in the amplitude of EPSCs at +40 mV and a change in the I–V relationship from inwardly rectifying to more linear. In mice exposed to an acute stress, AMPARs switched to GluA2-containing receptors, and 100 µm Alexa Fluor 594 did not alter the I–V relationship of synaptic currents. Therefore, a high concentration of Alexa Fluor dye changed the I–V relationship of EPSCs at GluA2-lacking AMPAR synapses. PMID:27280156

  12. The C(2)B Ca(2+)-binding motif of synaptotagmin is required for synaptic transmission in vivo.

    PubMed

    Mackler, J M; Drummond, J A; Loewen, C A; Robinson, I M; Reist, N E

    2002-07-18

    Synaptotagmin is a synaptic vesicle protein that is postulated to be the Ca(2+) sensor for fast, evoked neurotransmitter release. Deleting the gene for synaptotagmin (syt(null)) strongly suppresses synaptic transmission in every species examined, showing that synaptotagmin is central in the synaptic vesicle cycle. The cytoplasmic region of synaptotagmin contains two C(2) domains, C(2)A and C(2)B. Five, highly conserved, acidic residues in both the C(2)A and C(2)B domains of synaptotagmin coordinate the binding of Ca(2+) ions, and biochemical studies have characterized several in vitro Ca(2+)-dependent interactions between synaptotagmin and other nerve terminal molecules. But there has been no direct evidence that any of the Ca(2+)-binding sites within synaptotagmin are required in vivo. Here we show that mutating two of the Ca(2+)-binding aspartate residues in the C(2)B domain (D(416,418)N in Drosophila) decreased evoked transmitter release by >95%, and decreased the apparent Ca(2+) affinity of evoked transmitter release. These studies show that the Ca(2+)-binding motif of the C(2)B domain of synaptotagmin is essential for synaptic transmission. PMID:12110842

  13. Physiological consequences of selective suppression of synaptic transmission in developing cerebral cortical networks in vitro: differential effects on intrinsically generated bioelectric discharges in a living 'model' system for slow-wave sleep activity.

    PubMed

    Corner, Michael A; Baker, Robert E; van Pelt, Jaap

    2008-10-01

    Within the context of an updated thorough review of the literature concerning activity-dependent cerebro-cortical development, a survey is made of recent experiments which utilize spontaneous spike-trains as the dependent variable in rodent neocortex cultures when synaptic transmission is interfered with during early ontogeny. Emphasis is placed on the complexity of homeostatic adaptations to reduced as well as intensified firing. Two kinds of adaptation are distinguished: (i) rapid recovery (within several hours) towards baseline levels despite sustained blockade of excitatory synaptic transmission, and (ii) the generation of essentially normal firing patterns in cultures assayed in control medium following development in the presence of excitatory receptor blockers. The former category of homeostatic responses is strongly dependent on the type of preparation, with isolated organotypic explants showing greatly limited plasticity in comparison with co-cultures of matching contralateral pieces of cortical tissue. In such co-cultures, compensatory excitatory drive manifests itself even when all three known types of ionotropic glutamate receptors are chronically blocked, and is then mediated by (muscarinic) cholinergic mechanisms which normally do not contribute measurably to spontaneous activity. The rapid return of high levels of spontaneous firing during sustained selective glutamatergic receptor blockade appears to protect neuronal cultures treated in this way from becoming hyperexcitable. In particular, quasi-epileptiform paroxysmal bursting upon return to control medium, such as appears in preparations where bioelectric activity has been totally suppressed during network formation, fails to appear in chronically receptor blocked cultures. On the contrary, desensitization of blocked glutamate receptors, as a physiological compensation for the up-regulation of non-blocked receptors, could be demonstrated for both the AMPA and the NMDA glutamate receptor sub

  14. Systemic Hypoxia and the Depression of Synaptic Transmission in Rat Hippocampus after Carotid Artery Occlusion

    PubMed Central

    Fowler, J C; Gervitz, L M; Hamilton, M E; Walker, J A

    2003-01-01

    The relationship between step reductions in inspired oxygen and the amplitude of evoked field excitatory postsynaptic potentials (fEPSPs) recorded from hippocampal CA1 neurons was examined in anaesthetized rats with a unilateral common carotid artery occlusion. The amplitudes of fEPSPs recorded from the hippocampus ipsilateral to the occlusion were significantly more depressed with hypoxia than were the fEPSPs recorded from the contralateral hippocampus. The adenosine A1-selective antagonist, 8-cyclopentyl-1,3-dimethylxanthine (8-CPT), blunted the hypoxic depression of the fEPSP. Tissue partial pressure of oxygen (Ptiss,O2) was measured in the ipsilateral and contralateral hippocampus using glass Clark-style microelectrodes. Ptiss,O2 fell to similar levels as a function of inspired oxygen in the ipsilateral and contralateral hippocampus, and in the ipsilateral hippocampus after administration of 8-CPT. Hippocampal blood flow (HBF) was measured using laser Doppler flowmetry. A decline in HBF was associated with systemic hypoxia in both hippocampi. HBF, as a function of inspired oxygen, fell significantly more in the ipsilateral than in the contralateral hippocampus. We conclude that endogenous adenosine acting at the neuronal A1 receptor plays a major role in the depression of synaptic transmission during hypoxic ischaemia. The greater susceptibility of the fEPSP in the ipsilateral hippocampus to systemic hypoxia cannot be explained entirely by differences in Ptiss,O2 or HBF between the two hemispheres. PMID:12807994

  15. Xyloside primed glycosaminoglycans alter hair bundle micromechanical coupling and synaptic transmission: Pharmacokinetics

    NASA Astrophysics Data System (ADS)

    Holman, Holly A.; Tran, Vy M.; Nguyen, Lynn Y.; Arungundram, Sailaja; Kalita, Mausam; Kuberan, Balagurunathan; Rabbitt, Richard D.

    2015-12-01

    Glycosaminoglycans (GAGs) are ubiquitous in the inner ear, and disorders altering their structure or production often result in debilitating hearing and balance deficits. The specific mechanisms responsible for loss of hair-cell function are not well understood. We recently reported that introduction of a novel BODIPY conjugated xyloside (BX) into the endolymph primes fluorescent GAGs in vivo [6, 15]. Confocal and two-photon fluorescence imaging revealed rapid turnover and assembly of a glycocalyx enveloping the kinocilia and extending into the cupula, a structure that presumably serves as a mechanical link between the hair bundle and the cupula. Extracellular fluorescence was also observed around the basolateral surface of hair cells and surrounding afferent nerve projections into the crista. Single unit afferent recordings during mechanical hair bundle stimulation revealed temporary interruption of synaptic transmission following BX administration followed by recovery, demonstrating an essential role for GAGs in function of the hair cell synapse. In the present work we present a pharmacokinetic model to quantify the time course of BX primed GAG production and turnover in the ear.

  16. Xyloside primed glycosaminoglycans alter hair bundle micromechanical coupling and synaptic transmission: Pharmacokinetics

    SciTech Connect

    Holman, Holly A.; Nguyen, Lynn Y.; Tran, Vy M.; Arungundram, Sailaja; Kalita, Mausam; Kuberan, Balagurunathan; Rabbitt, Richard D.

    2015-12-31

    Glycosaminoglycans (GAGs) are ubiquitous in the inner ear, and disorders altering their structure or production often result in debilitating hearing and balance deficits. The specific mechanisms responsible for loss of hair-cell function are not well understood. We recently reported that introduction of a novel BODIPY conjugated xyloside (BX) into the endolymph primes fluorescent GAGs in vivo [6, 15]. Confocal and two-photon fluorescence imaging revealed rapid turnover and assembly of a glycocalyx enveloping the kinocilia and extending into the cupula, a structure that presumably serves as a mechanical link between the hair bundle and the cupula. Extracellular fluorescence was also observed around the basolateral surface of hair cells and surrounding afferent nerve projections into the crista. Single unit afferent recordings during mechanical hair bundle stimulation revealed temporary interruption of synaptic transmission following BX administration followed by recovery, demonstrating an essential role for GAGs in function of the hair cell synapse. In the present work we present a pharmacokinetic model to quantify the time course of BX primed GAG production and turnover in the ear.

  17. Structural elements that underlie Doc2β function during asynchronous synaptic transmission.

    PubMed

    Xue, Renhao; Gaffaney, Jon D; Chapman, Edwin R

    2015-08-01

    Double C2-like domain-containing proteins alpha and beta (Doc2α and Doc2β) are tandem C2-domain proteins proposed to function as Ca(2+) sensors for asynchronous neurotransmitter release. Here, we systematically analyze each of the negatively charged residues that mediate binding of Ca(2+) to the β isoform. The Ca(2+) ligands in the C2A domain were dispensable for Ca(2+)-dependent translocation to the plasma membrane, with one exception: neutralization of D220 resulted in constitutive translocation. In contrast, three of the five Ca(2+) ligands in the C2B domain are required for translocation. Importantly, translocation was correlated with the ability of the mutants to enhance asynchronous release when overexpressed in neurons. Finally, replacement of specific Ca(2+)/lipid-binding loops of synaptotagmin 1, a Ca(2+) sensor for synchronous release, with corresponding loops from Doc2β, resulted in chimeras that yielded slower kinetics in vitro and slower excitatory postsynaptic current decays in neurons. Together, these data reveal the key determinants of Doc2β that underlie its function during the slow phase of synaptic transmission. PMID:26195798

  18. Structural elements that underlie Doc2β function during asynchronous synaptic transmission

    PubMed Central

    Xue, Renhao; Gaffaney, Jon D.; Chapman, Edwin R.

    2015-01-01

    Double C2-like domain-containing proteins alpha and beta (Doc2α and Doc2β) are tandem C2-domain proteins proposed to function as Ca2+ sensors for asynchronous neurotransmitter release. Here, we systematically analyze each of the negatively charged residues that mediate binding of Ca2+ to the β isoform. The Ca2+ ligands in the C2A domain were dispensable for Ca2+-dependent translocation to the plasma membrane, with one exception: neutralization of D220 resulted in constitutive translocation. In contrast, three of the five Ca2+ ligands in the C2B domain are required for translocation. Importantly, translocation was correlated with the ability of the mutants to enhance asynchronous release when overexpressed in neurons. Finally, replacement of specific Ca2+/lipid-binding loops of synaptotagmin 1, a Ca2+ sensor for synchronous release, with corresponding loops from Doc2β, resulted in chimeras that yielded slower kinetics in vitro and slower excitatory postsynaptic current decays in neurons. Together, these data reveal the key determinants of Doc2β that underlie its function during the slow phase of synaptic transmission. PMID:26195798

  19. Acute lipopolysaccharide exposure facilitates epileptiform activity via enhanced excitatory synaptic transmission and neuronal excitability in vitro

    PubMed Central

    Gao, Fei; Liu, Zhiqiang; Ren, Wei; Jiang, Wen

    2014-01-01

    Growing evidence indicates brain inflammation has been involved in the genesis of seizures. However, the direct effect of acute inflammation on neuronal circuits is not well known. Lipopolysaccharide (LPS) has been used extensively to stimulate brain inflammatory responses both in vivo and in vitro. Here, we observed the contribution of inflammation induced by 10 μg/mL LPS to the excitability of neuronal circuits in acute hippocampal slices. When slices were incubated with LPS for 30 minutes, significant increased concentration of tumor necrosis factor α and interleukin 1β were detected by enzyme-linked immunosorbent assay. In electrophysiological recordings, we found that frequency of epileptiform discharges and spikes per burst increased 30 minutes after LPS application. LPS enhanced evoked excitatory postsynaptic currents but did not modify evoked inhibitory postsynaptic currents. In addition, exposure to LPS enhanced the excitability of CA1 pyramidal neurons, as demonstrated by a decrease in rheobase and an increase in action potential frequency elicited by depolarizing current injection. Our observations suggest that acute inflammation induced by LPS facilitates epileptiform activity in vitro and that enhancement of excitatory synaptic transmission and neuronal excitability may contribute to this facilitation. These results may provide new clues for treating seizures associated with brain inflammatory disease. PMID:25170268

  20. Raised Intracellular Calcium Contributes to Ischemia-Induced Depression of Evoked Synaptic Transmission

    PubMed Central

    Jalini, Shirin; Ye, Hui; Tonkikh, Alexander A.; Charlton, Milton P.; Carlen, Peter L.

    2016-01-01

    Oxygen-glucose deprivation (OGD) leads to depression of evoked synaptic transmission, for which the mechanisms remain unclear. We hypothesized that increased presynaptic [Ca2+]i during transient OGD contributes to the depression of evoked field excitatory postsynaptic potentials (fEPSPs). Additionally, we hypothesized that increased buffering of intracellular calcium would shorten electrophysiological recovery after transient ischemia. Mouse hippocampal slices were exposed to 2 to 8 min of OGD. fEPSPs evoked by Schaffer collateral stimulation were recorded in the stratum radiatum, and whole cell current or voltage clamp recordings were performed in CA1 neurons. Transient ischemia led to increased presynaptic [Ca2+]i, (shown by calcium imaging), increased spontaneous miniature EPSP/Cs, and depressed evoked fEPSPs, partially mediated by adenosine. Buffering of intracellular Ca2+ during OGD by membrane-permeant chelators (BAPTA-AM or EGTA-AM) partially prevented fEPSP depression and promoted faster electrophysiological recovery when the OGD challenge was stopped. The blocker of BK channels, charybdotoxin (ChTX), also prevented fEPSP depression, but did not accelerate post-ischemic recovery. These results suggest that OGD leads to elevated presynaptic [Ca2+]i, which reduces evoked transmitter release; this effect can be reversed by increased intracellular Ca2+ buffering which also speeds recovery. PMID:26934214

  1. Orexin-A modulates excitatory synaptic transmission and neuronal excitability in the spinal cord substantia gelatinosa.

    PubMed

    Jeon, Younghoon; Park, Ki Bum; Pervin, Rokeya; Kim, Tae Wan; Youn, Dong-ho

    2015-09-14

    Although intrathecal orexin-A has been known to be antinociceptive in various pain models, the role of orexin-A in antinociception is not well characterized. In the present study, we examined whether orexin-A modulates primary afferent fiber-mediated or spontaneous excitatory synaptic transmission using transverse spinal cord slices with attached dorsal root. Bath-application of orexin-A (100nM) reduced the amplitude of excitatory postsynaptic currents (EPSCs) evoked by electrical stimulation of Aδ- or C-primary afferent fibers. The magnitude of reduction was much larger for EPSCs evoked by polysynaptic C-fibers than polysynaptic Aδ-fibers, whereas it was similar in EPSCs evoked by monosynaptic Aδ- or C-fibers. SB674042, an orexin-1 receptor antagonist, but not EMPA, an orexin-2 receptor antagonist, significantly inhibited the orexin-A-induced reduction in EPSC amplitude from mono- or polysynaptic Aδ-fibers, as well as from mono- or polysynaptic C-fibers. Furthermore, orexin-A significantly increased the frequency of spontaneous EPSCs but not the amplitude. This increase was almost completely blocked by both SB674042 and EMPA. On the other hand, orexin-A produced membrane oscillations and inward currents in the SG neurons that were partially or completely inhibited by SB674042 or EMPA, respectively. Thus, this study suggests that the spinal actions of orexin-A underlie orexin-A-induced antinociceptive effects via different subtypes of orexin receptors. PMID:26254164

  2. Regulation of Synaptic Transmission at the Caenorhabditis elegans M4 Neuromuscular Junction by an Antagonistic Relationship Between Two Calcium Channels

    PubMed Central

    Steciuk, Mark; Cheong, Mi Cheong; Waite, Christopher; You, Young-Jai; Avery, Leon

    2014-01-01

    In wild-type Caenorhabditis elegans, the synapse from motor neuron M4 to pharyngeal terminal bulb (TB) muscles is silent, and the muscles are instead excited by gap junction connections from adjacent muscles. An eat-5 innexin mutant lacking this electrical connection has few TB contractions and is unable to grow well on certain foods. We showed previously that this defect can be overcome by activation of the M4 → TB synapse. To identify genes that negatively regulate synaptic transmission, we isolated new suppressors of eat-5. To our surprise, these suppressors included null mutations in NPQR-type calcium channel subunit genes unc-2 and unc-36. Our results are consistent with the hypothesis that Ca2+ entry through the NPQR-type channel inhibits synaptic transmission by activating the calcium-activated K+ channel SLO-1, thus antagonizing the EGL-19 L-type calcium channel. PMID:25378475

  3. Glutamatergic Transmission: A Matter of Three

    PubMed Central

    Martínez-Lozada, Zila; Ortega, Arturo

    2015-01-01

    Glutamatergic transmission in the vertebrate brain requires the involvement of glia cells, in a continuous molecular dialogue. Glial glutamate receptors and transporters are key molecules that sense synaptic activity and by these means modify their physiology in the short and long term. Posttranslational modifications that regulate protein-protein interactions and modulate transmitter removal are triggered in glial cells by neuronal released glutamate. Moreover, glutamate signaling cascades in these cells are linked to transcriptional and translational control and are critically involved in the control of the so-called glutamate/glutamine shuttle and by these means in glutamatergic neurotransmission. In this contribution, we summarize our current understanding of the biochemical consequences of glutamate synaptic activity in their surrounding partners and dissect the molecular mechanisms that allow neurons to take control of glia physiology to ensure proper glutamate-mediated neuronal communication. PMID:26345375

  4. Cross-synaptic synchrony and transmission of signal and noise across the mouse retina.

    PubMed

    Grimes, William N; Hoon, Mrinalini; Briggman, Kevin L; Wong, Rachel O; Rieke, Fred

    2014-01-01

    Cross-synaptic synchrony--correlations in transmitter release across output synapses of a single neuron--is a key determinant of how signal and noise traverse neural circuits. The anatomical connectivity between rod bipolar and A17 amacrine cells in the mammalian retina, specifically that neighboring A17s often receive input from many of the same rod bipolar cells, provides a rare technical opportunity to measure cross-synaptic synchrony under physiological conditions. This approach reveals that synchronization of rod bipolar cell synapses is near perfect in the dark and decreases with increasing light level. Strong synaptic synchronization in the dark minimizes intrinsic synaptic noise and allows rod bipolar cells to faithfully transmit upstream signal and noise to downstream neurons. Desynchronization in steady light lowers the sensitivity of the rod bipolar output to upstream voltage fluctuations. This work reveals how cross-synaptic synchrony shapes retinal responses to physiological light inputs and, more generally, signaling in complex neural networks. PMID:25180102

  5. The Role of cGMP on Adenosine A1 Receptor-mediated Inhibition of Synaptic Transmission at the Hippocampus

    PubMed Central

    Pinto, Isa; Serpa, André; Sebastião, Ana M.; Cascalheira, José F.

    2016-01-01

    Both adenosine A1 receptor and cGMP inhibit synaptic transmission at the hippocampus and recently it was found that A1 receptor increased cGMP levels in hippocampus, but the role of cGMP on A1 receptor-mediated inhibition of synaptic transmission remains to be established. In the present work we investigated if blocking the NOS/sGC/cGMP/PKG pathway using nitric oxide synthase (NOS), protein kinase G (PKG), and soluble guanylyl cyclase (sGC) inhibitors modify the A1 receptor effect on synaptic transmission. Neurotransmission was evaluated by measuring the slope of field excitatory postsynaptic potentials (fEPSPs) evoked by electrical stimulation at hippocampal slices. N6-cyclopentyladenosine (CPA, 15 nM), a selective A1 receptor agonist, reversibly decreased the fEPSPs by 54 ± 5%. Incubation of the slices with an inhibitor of NOS (L-NAME, 200 μM) decreased the CPA effect on fEPSPs by 57 ± 9% in female rats. In males, ODQ (10 μM), an sGC inhibitor, decreased the CPA inhibitory effect on fEPSPs by 23 ± 6%, but only when adenosine deaminase (ADA,1 U/ml) was present; similar results were found in females, where ODQ decreased CPA-induced inhibition of fEPSP slope by 23 ± 7%. In male rats, the presence of the PKG inhibitor (KT5823, 1 nM) decreased the CPA effect by 45.0 ± 9%; similar results were obtained in females, where KT5823 caused a 32 ± 9% decrease on the CPA effect. In conclusion, the results suggest that the inhibitory action of adenosine A1 receptors on synaptic transmission at hippocampus is, in part, mediated by the NOS/sGC/cGMP/PKG pathway. PMID:27148059

  6. 5-HT2 receptors mediate functional modulation of GABAa receptors and inhibitory synaptic transmissions in human iPS-derived neurons

    PubMed Central

    Wang, Haitao; Hu, Lingli; Liu, Chunhua; Su, Zhenghui; Wang, Lihui; Pan, Guangjin; Guo, Yiping; He, Jufang

    2016-01-01

    Neural progenitors differentiated from induced pluripotent stem cells (iPS) hold potentials for treating neurological diseases. Serotonin has potent effects on neuronal functions through multiple receptors, underlying a variety of neural disorders. Glutamate and GABA receptors have been proven functional in neurons differentiated from iPS, however, little is known about 5-HT receptor-mediated modulation in such neuronal networks. In the present study, human iPS were differentiated into cells possessing featured physiological properties of cortical neurons. Whole-cell patch-clamp recording was used to examine the involvement of 5-HT2 receptors in functional modulation of GABAergic synaptic transmission. We found that serotonin and DOI (a selective agonist of 5-HT2A/C receptor) reversibly reduced GABA-activated currents, and this 5-HT2A/C receptor mediated inhibition required G protein, PLC, PKC, and Ca2+ signaling. Serotonin increased the frequency of miniature inhibitory postsynaptic currents (mIPSCs), which could be mimicked by α-methylserotonin, a 5-HT2 receptor agonist. In contrast, DOI reduced both frequency and amplitude of mIPSCs. These findings suggested that in iPS-derived human neurons serotonin postsynaptically reduced GABAa receptor function through 5-HT2A/C receptors, but presynaptically other 5-HT2 receptors counteracted the action of 5-HT2A/C receptors. Functional expression of serotonin receptors in human iPS-derived neurons provides a pre-requisite for their normal behaviors after grafting. PMID:26837719

  7. Blockade of presynaptic 4-aminopyridine-sensitive potassium channels increases initial neurotransmitter release probability, reinstates synaptic transmission altered by GABAB receptor activation in rat midbrain periaqueductal gray.

    PubMed

    Li, Guangying; Liu, Zhi-Liang; Zhang, Wei-Ning; Yang, Kun

    2016-01-01

    The activation of γ-aminobutyric acid receptor subtype B (GABAB) receptors in the midbrain ventrolateral periaqueductal gray (vlPAG) induces both postsynaptic and presynaptic inhibition. Whereas the postsynaptic inhibition is mediated by G protein-coupled inwardly rectifying K channels, the presynaptic inhibition of neurotransmitter release is primarily mediated by voltage-gated calcium channels. Using whole-cell recordings from acute rat PAG slices, we report here that the bath application of 4-aminopyridine, a voltage-gated K channel blocker, increases the initial GABA and glutamate release probability (P) and reinstates P depressed by presynaptic GABAB receptor activation at inhibitory and excitatory synapses, respectively. However, Ba, which blocks G protein-coupled inwardly rectifying K channels, does not produce similar effects. Our data suggest that the blockade of presynaptic 4-aminopyridine-sensitive K channels in vlPAG facilitates neurotransmitter release and reinstates synaptic transmission that has been altered by presynaptic GABAB receptor activation. Because vlPAG is involved in the descending pain control system, the present results may have potential therapeutic applications. PMID:26575285

  8. Dynamic effects of TNF-α on synaptic transmission in mice over time following sciatic nerve chronic constriction injury

    PubMed Central

    Zhang, Hongmei; Zhang, Haijun

    2013-01-01

    Nerve injury-induced central sensitization can manifest as an increase in excitatory synaptic transmission and/or as a decrease in inhibitory synaptic transmission in spinal dorsal horn neurons. Cytokines such as tumor necrosis factor-α (TNF-α) are induced in the spinal cord under various injury conditions and contribute to neuropathic pain. In this study we examined the effect of TNF-α in modulating excitatory and inhibitory synaptic input to spinal substantia gelatinosa (SG) neurons over time in mice following chronic constriction injury (CCI) of the sciatic nerve. Whole cell patch-clamp studies from SG neurons showed that TNF-α enhanced overall excitability of the spinal cord early in time following nerve injury 3 days after CCI compared with that in sham control mice. In contrast, the effects of TNF were blunted 14 days after CCI in nerve-injured mice compared with sham surgery mice. Immunohistochemical staining showed that the expression of TNF-α receptor 1 (TNFR1) was increased at 3 days but decreased at 14 days following CCI in the ipsilateral vs. the contralateral spinal cord dorsal horn. These results suggest that TNF-α acting at TNFR1 is important in the development of neuropathic pain by facilitating excitatory synaptic signaling in the acute phases after nerve injury but has a reduced effect on spinal neuron signaling in the later phases of nerve injury-induced pain. Failure of the facilatory effects of TNF-α on excitatory synaptic signaling in the dorsal horn to resolve following nerve injury may be an important component in the transition between acute and chronic pain conditions. PMID:23864372

  9. Dentate gyrus–CA3 glutamate release/NMDA transmission mediates behavioral despair and antidepressant-like responses to leptin

    PubMed Central

    Wang, Xuezhen; Zhang, Di; Lu, Xin-Yun

    2014-01-01

    Compelling evidence supports the important role of the glutamatergic system in the pathophysiology of major depression and also as a target for rapid-acting antidepressants. However, the functional role of glutamate release/transmission in behavioral processes related to depression and antidepressant efficacy remains to be elucidated. In this study, glutamate release and behavioral responses to tail suspension, a procedure commonly used for inducing behavioral despair, were simultaneously monitored in real time. The onset of tail suspension stress evoked a rapid increase in glutamate release in hippocampal field CA3, which declined gradually after its offset. Blockade of NMDA receptors by intra-CA3 infusion of MK-801, a non-competitive NMDA receptor antagonist, reversed behavioral despair. The CA3 was innervated by granule neurons expressing the leptin receptor (LepRb) in the dentate gyrus (DG), representing a subpopulation of granule neurons that were devoid of stress-induced activation. Leptin treatment dampened tail suspension-evoked glutamate release in CA3. On the other hand, intra-CA3 infusion of NMDA blocked the antidepressant-like effect of leptin in reversing behavioral despair in both the tail suspension and forced swim tests, which involved activation of Akt signaling in DG. Together, these results suggest that the DG-CA3 glutamatergic pathway is critical for mediating behavioral despair and antidepressant-like responses to leptin. PMID:25092243

  10. Retrograde Endocannabinoid Signaling Reduces GABAergic Synaptic Transmission to Gonadotropin-Releasing Hormone Neurons

    PubMed Central

    Farkas, Imre; Kalló, Imre; Deli, Levente; Vida, Barbara; Hrabovszky, Erik; Fekete, Csaba; Moenter, Suzanne M.; Watanabe, Masahiko; Liposits, Zsolt

    2010-01-01

    Cannabinoids suppress fertility via reducing hypothalamic GnRH output. γ-Aminobutyric acid (GABA)A receptor (GABAA-R)-mediated transmission is a major input to GnRH cells that can be excitatory. We hypothesized that cannabinoids act via inhibiting GABAergic input. We performed loose-patch electrophysiological studies of acute slices from adult male GnRH-green fluorescent protein transgenic mice. Bath application of type 1 cannabinoid receptor (CB1) agonist WIN55,212 decreased GnRH neuron firing rate. This action was detectable in presence of the glutamate receptor antagonist kynurenic acid but disappeared when bicuculline was also present, indicating GABAA-R involvement. In immunocytochemical experiments, CB1-immunoreactive axons formed contacts with GnRH neurons and a subset established symmetric synapses characteristic of GABAergic neurotransmission. Functional studies were continued with whole-cell patch-clamp electrophysiology in presence of tetrodotoxin. WIN55,212 decreased the frequency of GABAA-R-mediated miniature postsynaptic currents (mPSCs) (reflecting spontaneous vesicle fusion), which was prevented with the CB1 antagonist AM251, indicating collectively that activation of presynaptic CB1 inhibits GABA release. AM251 alone increased mPSC frequency, providing evidence that endocannabinoids tonically inhibit GABAA-R drive onto GnRH neurons. Increased mPSC frequency was absent when diacylglycerol lipase was blocked intracellularly with tetrahydrolipstatin, showing that tonic inhibition is caused by 2-arachidonoylglycerol production of GnRH neurons. CdCl2 in extracellular solution can maintain both action potentials and spontaneous vesicle fusion. Under these conditions, when endocannabinoid-mediated blockade of spontaneous vesicle fusion was blocked with AM251, GnRH neuron firing increased, revealing an endogenous endocannabinoid brake on GnRH neuron firing. Retrograde endocannabinoid signaling may represent an important mechanism under physiological and

  11. Environmental enrichment rescues the effects of early life inflammation on markers of synaptic transmission and plasticity.

    PubMed

    Kentner, Amanda C; Khoury, Antoine; Lima Queiroz, Erika; MacRae, Molly

    2016-10-01

    Environmental enrichment (EE) has been successful at rescuing the brain from a variety of early-life psychogenic stressors. However, its ability to reverse the behavioral and neural alterations induced by a prenatal maternal infection model of schizophrenia is less clear. Moreover, the specific interactions between the components (i.e. social enhancement, novelty, physical activity) of EE that lead to its success as a supportive intervention have not been adequately identified. In the current study, standard housed female Sprague-Dawley rats were administered either the inflammatory endotoxin lipopolysaccharide (LPS; 100μg/kg) or pyrogen-free saline (equivolume) on gestational day 15. On postnatal day 50, offspring were randomized into one of three conditions: EE (group housed in a large multi-level cage with novel toys, tubes and ramps), Colony Nesting (CN; socially-housed in a larger style cage), or Standard Care (SC; pair-housed in standard cages). Six weeks later we scored social engagement and performance in the object-in-place task. Afterwards hippocampus and prefrontal cortex (n=7-9) were collected and evaluated for excitatory amino acid transporter (EAAT) 1-3, brain-derived neurotrophic factor (BDNF), and neurotrophic tyrosine kinase, receptor type 2 (TrkB) gene expression (normalized to GAPDH) using qPCR methods. Overall, we show that gestational inflammation downregulates genes critical to synaptic transmission and plasticity, which may underlie the pathogenesis of neurodevelopmental disorders such as schizophrenia and autism. Additionally, we observed disruptions in both social engagement and spatial discrimination. Importantly, behavioral and neurophysiological effects were rescued in an experience dependent manner. Given the evidence that schizophrenia and autism may be associated with infection during pregnancy, these data have compelling implications for the prevention and reversibility of the consequences that follow immune activation in early in

  12. Excitability and Synaptic Transmission in the Enteric Nervous System: Does Diet Play a Role?

    PubMed

    Bertrand, Paul P; Polglaze, Kate E; Chen, Hui; Sandow, Shaun L; Walduck, Anna; Jenkins, Trisha A; Bertrand, Rebecca L; Lomax, Alan E; Liu, Lu

    2016-01-01

    Changes in diet are a challenge to the gastrointestinal tract which needs to alter its processing mechanisms to continue to process nutrients and maintain health. In particular, the enteric nervous system (ENS) needs to adapt its motor and secretory programs to deal with changes in nutrient type and load in order to optimise nutrient absorption.The nerve circuits in the gut are complex, and the numbers and types of neurons make recordings of specific cell types difficult, time-consuming, and prone to sampling errors. Nonetheless, traditional research methods like intracellular electrophysiological approaches have provided the basis for our understanding of the ENS circuitry. In particular, animal models of intestinal inflammation have shown us that we can document changes to neuronal excitability and synaptic transmission.Recent studies examining diet-induced changes to ENS programming have opted to use fast imaging techniques to reveal changes in neuron function. Advances in imaging techniques using voltage- or calcium-sensitive dyes to record neuronal activity promise to overcome many limitations inherent to electrophysiological approaches. Imaging techniques allow access to a wide range of ENS phenotypes and to the changes they undergo during dietary challenges. These sorts of studies have shown that dietary variation or obesity can change how the ENS processes information-in effect reprogramming the ENS. In this review, the data gathered from intracellular recordings will be compared with measurements made using imaging techniques in an effort to determine if the lessons learnt from inflammatory changes are relevant to the understanding of diet-induced reprogramming. PMID:27379647

  13. Light-evoked recovery from wortmannin-induced inhibition of catecholamine secretion and synaptic transmission.

    PubMed

    Warashina, A

    1999-07-15

    Wortmannin (WT) is known to inhibit catecholamine (CA) secretion in chromaffin cells. This effect was found to be sensitive to UV light in experiments designed to perform simultaneous monitoring of changes in [Ca2+]i and CA secretion in perfused rat adrenal medullas. When the change in [Ca2+]i was measured using calcium green-1 (490 nm excitation), a 35-min treatment with 10 microM WT caused a 69% inhibition of CA secretion evoked by excess (30 mM) extracellular K+ and a moderate inhibition of the [Ca2+]i response. In contrast, the same treatment of fura-2-loaded cells with WT caused only an 11% inhibition of the high-K+-evoked secretion and no significant attenuation of the [Ca2+]i response. However, during interruption of fluorometry with fura-2, the inhibitory effect of WT developed at a rate similar to that exhibited in calcium green-1-loaded cells. The WT-induced inhibition of high-K+- or bradykinin-evoked secretory responses, which was otherwise irreversible, was reversed by exposing WT-treated chromaffin cells to 380-nm light. When WT was reapplied to the cells of which the secretory ability had been restored by light irradiation, the secretory response was inhibited with a time course similar to that shown during the initial treatment with WT. The photosensitive effect of WT was also demonstrated using bullfrog sympathetic ganglia in which WT-induced inhibition of synaptic transmission was reversed by irradiation with 380-nm light. These results suggest that UV light removes the inhibitory effects of WT by disrupting the covalent bond formed between WT and a target molecule which remains to be determined, although myosin light chain kinase has been reported as the target molecule in both cases examined in this study. PMID:10395748

  14. Mechanisms underlying H(2)O(2)-mediated inhibition of synaptic transmission in rat hippocampal slices.

    PubMed

    Avshalumov, M V; Chen, B T; Rice, M E

    2000-11-01

    Hydrogen peroxide (H(2)O(2)) inhibits the population spike (PS) evoked by Schaffer collateral stimulation in hippocampal slices. Proposed mechanisms underlying this effect include generation of hydroxyl radicals (.OH) and inhibition of presynaptic Ca(2+) entry. We have examined these possible mechanisms in rat hippocampal slices. Inhibition of the evoked PS by H(2)O(2) was sharply concentration-dependent: 1.2 mM H(2)O(2) had no effect, whereas 1.5 and 2.0 mM H(2)O(2) reversibly depressed PS amplitude by roughly 80%. The iron chelator, deferoxamine (1 mM), and the endogenous.OH scavenger, ascorbate (400 microM), prevented PS inhibition, confirming.OH involvement. Isoascorbate (400 microM), which unlike ascorbate is not taken up by brain cells, also prevented PS inhibition, indicating an extracellular site of.OH generation or action. We then investigated whether H(2)O(2)-induced PS depression could be overcome by prolonged stimulation, which enhances Ca(2+) entry. During 5-s, 10-Hz trains under control conditions, PS amplitude increased to over 200% during the first three-four pulses, then stabilized. In the presence of H(2)O(2), PS amplitude was initially depressed, but began to recover after 2.5 s of stimulation, finally reaching 80% of the control maximum. In companion experiments, we assessed the effect of H(2)O(2) on presynaptic Ca(2+) entry by monitoring extracellular Ca(2+) concentration ([Ca(2+)](o)) during train stimulation in the presence of postsynaptic receptor blockers. Evoked [Ca(2+)](o) shifts were apparently unaltered by H(2)O(2), suggesting a lack of effect on Ca(2+) entry. Taken together, these findings suggest new ways in which reactive oxygen species (ROS) might act as signaling agents, specifically as modulators of synaptic transmission. PMID:11056187

  15. Acetyl-l-carnitine restores synaptic transmission and enhances the inducibility of stable LTP after oxygen-glucose deprivation.

    PubMed

    Kocsis, Kitti; Frank, Rita; Szabó, József; Knapp, Levente; Kis, Zsolt; Farkas, Tamás; Vécsei, László; Toldi, József

    2016-09-22

    Hypoxic circumstances result in functional and structural impairments of the brain. Oxygen-glucose deprivation (OGD) on hippocampal slices is a technique widely used to investigate the consequences of ischemic stroke and the potential neuroprotective effects of different drugs. Acetyl-l-carnitine (ALC) is a naturally occurring substance in the body, and it can therefore be administered safely even in relatively high doses. In previous experiments, ALC pretreatment proved to be effective against global hypoperfusion. In the present study, we investigated whether ALC can be protective in an OGD model. We are not aware of any earlier study in which the long-term potentiation (LTP) function on hippocampal slices was measured after OGD. Therefore, we set out to determine whether an effective ALC concentration has an effect on synaptic plasticity after OGD in the hippocampal CA1 subfield of rats. A further aim was to investigate the mechanism underlying the protective effect of this compound. The experiments revealed that ALC is neuroprotective against OGD in a dose-dependent manner, which is manifested not only in the regeneration of the impaired synaptic transmission after the OGD, but also in the inducibility and stability of the LTP. In the case of the most effective concentration of ALC (500μM), use of a phosphoinositide 3-kinase (PI3K) inhibitor (LY294002) revealed that the PI3K/Akt signaling pathway has a key role in the restoration of the synaptic transmission and plasticity reached by ALC treatment. PMID:27378558

  16. GSK-3β inhibitors reverse cocaine-induced synaptic transmission dysfunction in the nucleus accumbens.

    PubMed

    Zhao, Rui; Chen, Jiaojiao; Ren, Zhaoxiang; Shen, Hui; Zhen, Xuechu

    2016-11-01

    Nucleus accumbens receives glutamatergic projection from the prefrontal cortex (PFC) and dopaminergic input from the Ventral tegmental area (VTA). Recent studies have suggested a critical role for serine/threonine kinase glycogen synthase kinase 3β (GSK3β) in cocaine-induced hyperactivity; however, the effect of GSK3β on the modulation of glutamatergic and dopaminergic afferents is unclear. In this study, we found that the GSK3 inhibitors, LiCl (100 mg/kg, i.p.) or SB216763 (2.5 mg/kg, i.p.), blocked the cocaine-induced hyperlocomotor activity in rats. By employing single-unit recordings in vivo, we found that pretreatment with either SB216763 or LiCl for 15 min reversed the cocaine-inhibited firing frequency of medium spiny neuron (MSN) in the nucleus accumbens (NAc). Preperfusion of SB216763 (5 μM) ameliorated the inhibitory effect of cocaine on both the α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) (up to 99 ± 6.8% inhibition) and N-methyl-D-aspartic acid receptor (NMDAR)-mediate EPSC (up to 73 ± 9.7% inhibition) in the NAc in brain slices. The effect of cocaine on AMPA and NMDA receptor-mediate excitatory postsynaptic current (EPSC) were mimicked by the D1 -like receptor agonist SKF 38393 and blocked by the D1 -like receptor antagonist SCH 23390, whereas D2 -like receptor agonist or antagonist failed to mimic or to block the action of cocaine. Preperfusion of SB216763 for 5 min also ameliorated the inhibitory effect of SKF38393 on both AMPA and NMDA receptor-mediated components of EPSC, indicate the effect of SB216763 on cocaine was via the D1 -like receptor. Moreover, cocaine inhibited the presynaptic release of glutamate in the NAc, and SB216763 reversed this effect. In conclusion, D1 receptor-GSK3β pathway, which mediates glutamatergic transmission in the NAc core through a presynaptic mechanism, plays an important role in acute cocaine-induced hyperlocomotion. PMID:27377051

  17. Ligands for Ionotropic Glutamate Receptors

    NASA Astrophysics Data System (ADS)

    Swanson, Geoffrey T.; Sakai, Ryuichi

    Marine-derived small molecules and peptides have played a central role in elaborating pharmacological specificities and neuronal functions of mammalian ionotropic glutamate receptors (iGluRs), the primary mediators of excitatory syn-aptic transmission in the central nervous system (CNS). As well, the pathological sequelae elicited by one class of compounds (the kainoids) constitute a widely-used animal model for human mesial temporal lobe epilepsy (mTLE). New and existing molecules could prove useful as lead compounds for the development of therapeutics for neuropathologies that have aberrant glutamatergic signaling as a central component. In this chapter we discuss natural source origins and pharmacological activities of those marine compounds that target ionotropic glutamate receptors.

  18. [The role of synaptic transmission in memory and neurodegeneration processes and effects of neurotropic preparations].

    PubMed

    Voronina, T A

    2003-01-01

    Academician Zakusov, in his book Pharmacology of Central Synapses (Moscow, 1973), emphasized the central role of synaptic processes in regulation of various forms of behavior, memory, and psychotropic drug action. The paper considers most promising directions in the search for substances possessing nootropic and neuroprotector properties, many of which were developed at the Institute of Pharmacology based on the notion about synaptic processes. These investigations led to the creation of well-known drugs such as mexidole, noopept, nooglutyl, beglimin, etc. Special attention is devoted to the implementation and modern development of the ideas of Academician Zakusov. Recent data are presented on the role of neuropeptides, neurotrophins, and intracellular signaling mechanisms in synaptic plasticity, memory processes, and development of neurodegenerative states. PMID:12962041

  19. Disruption of Akt signaling decreases dopamine sensitivity in modulation of inhibitory synaptic transmission in rat prefrontal cortex.

    PubMed

    Li, Yan-Chun; Yang, Sha-Sha; Gao, Wen-Jun

    2016-09-01

    Akt is a serine/threonine kinase, which is dramatically reduced in the prefrontal cortex (PFC) of patients with schizophrenia, and a deficiency in Akt1 results in PFC function abnormalities. Although the importance of Akt in dopamine (DA) transmission is well established, how impaired Akt signaling affects the DA modulation of synaptic transmission in the PFC has not been characterized. Here we show that Akt inhibitors significantly decreased receptor sensitivity to DA by shifting DA modulation of GABAA receptor-mediated inhibitory postsynaptic currents (IPSCs) in prefrontal cortical neurons. Akt inhibition caused a significant decrease in synaptic dopamine D2 receptor (D2R) levels with high-dose DA exposure. In addition, Akt inhibition failed to affect DA modulation of IPSCs after blockade of β-arrestin 2. β-arrestin 2-mediated interaction of clathrin with D2R was enhanced by co-application of a Akt inhibitor and DA. Taken together, the reduced response in DA modulation of inhibitory transmission mainly involved β-arrestin 2-dependent D2R desensitization. PMID:27163190

  20. Effects of chronic stress in adolescence on learned fear, anxiety, and synaptic transmission in the rat prelimbic cortex.

    PubMed

    Negrón-Oyarzo, Ignacio; Pérez, Miguel Ángel; Terreros, Gonzalo; Muñoz, Pablo; Dagnino-Subiabre, Alexies

    2014-02-01

    The prelimbic cortex and amygdala regulate the extinction of conditioned fear and anxiety, respectively. In adult rats, chronic stress affects the dendritic morphology of these brain areas, slowing extinction of learned fear and enhancing anxiety. The aim of this study was to determine whether rats subjected to chronic stress in adolescence show changes in learned fear, anxiety, and synaptic transmission in the prelimbic cortex during adulthood. Male Sprague Dawley rats were subjected to seven days of restraint stress on postnatal day forty-two (PND 42, adolescence). Afterward, the fear-conditioning paradigm was used to study conditioned fear extinction. Anxiety-like behavior was measured one day (PND 50) and twenty-one days (PND 70, adulthood) after stress using the elevated-plus maze and dark-light box tests, respectively. With another set of rats, excitatory synaptic transmission was analyzed with slices of the prelimbic cortex. Rats that had been stressed during adolescence and adulthood had higher anxiety-like behavior levels than did controls, while stress-induced slowing of learned fear extinction in adolescence was reversed during adulthood. As well, the field excitatory postsynaptic potentials of stressed adolescent rats had significantly lower amplitudes than those of controls, although the amplitudes were higher in adulthood. Our results demonstrate that short-term stress in adolescence induces strong effects on excitatory synaptic transmission in the prelimbic cortex and extinction of learned fear, where the effect of stress on anxiety is more persistent than on the extinction of learned fear. These data contribute to the understanding of stress neurobiology. PMID:24216268

  1. Interaction of electrically evoked activity with intrinsic dynamics of cultured cortical networks with and without functional fast GABAergic synaptic transmission

    PubMed Central

    Baltz, Thomas; Voigt, Thomas

    2015-01-01

    The modulation of neuronal activity by means of electrical stimulation is a successful therapeutic approach for patients suffering from a variety of central nervous system disorders. Prototypic networks formed by cultured cortical neurons represent an important model system to gain general insights in the input–output relationships of neuronal tissue. These networks undergo a multitude of developmental changes during their maturation, such as the excitatory–inhibitory shift of the neurotransmitter GABA. Very few studies have addressed how the output properties to a given stimulus change with ongoing development. Here, we investigate input–output relationships of cultured cortical networks by probing cultures with and without functional GABAAergic synaptic transmission with a set of stimulation paradigms at various stages of maturation. On the cellular level, low stimulation rates (<15 Hz) led to reliable neuronal responses; higher rates were increasingly ineffective. Similarly, on the network level, lowest stimulation rates (<0.1 Hz) lead to maximal output rates at all ages, indicating a network wide refractory period after each stimulus. In cultures aged 3 weeks and older, a gradual recovery of the network excitability within tens of milliseconds was in contrast to an abrupt recovery after about 5 s in cultures with absent GABAAergic synaptic transmission. In these GABA deficient cultures evoked responses were prolonged and had multiple discharges. Furthermore, the network excitability changed periodically, with a very slow spontaneous change of the overall network activity in the minute range, which was not observed in cultures with absent GABAAergic synaptic transmission. The electrically evoked activity of cultured cortical networks, therefore, is governed by at least two potentially interacting mechanisms: A refractory period in the order of a few seconds and a very slow GABA dependent oscillation of the network excitability. PMID:26236196

  2. Interaction of electrically evoked activity with intrinsic dynamics of cultured cortical networks with and without functional fast GABAergic synaptic transmission.

    PubMed

    Baltz, Thomas; Voigt, Thomas

    2015-01-01

    The modulation of neuronal activity by means of electrical stimulation is a successful therapeutic approach for patients suffering from a variety of central nervous system disorders. Prototypic networks formed by cultured cortical neurons represent an important model system to gain general insights in the input-output relationships of neuronal tissue. These networks undergo a multitude of developmental changes during their maturation, such as the excitatory-inhibitory shift of the neurotransmitter GABA. Very few studies have addressed how the output properties to a given stimulus change with ongoing development. Here, we investigate input-output relationships of cultured cortical networks by probing cultures with and without functional GABAAergic synaptic transmission with a set of stimulation paradigms at various stages of maturation. On the cellular level, low stimulation rates (<15 Hz) led to reliable neuronal responses; higher rates were increasingly ineffective. Similarly, on the network level, lowest stimulation rates (<0.1 Hz) lead to maximal output rates at all ages, indicating a network wide refractory period after each stimulus. In cultures aged 3 weeks and older, a gradual recovery of the network excitability within tens of milliseconds was in contrast to an abrupt recovery after about 5 s in cultures with absent GABAAergic synaptic transmission. In these GABA deficient cultures evoked responses were prolonged and had multiple discharges. Furthermore, the network excitability changed periodically, with a very slow spontaneous change of the overall network activity in the minute range, which was not observed in cultures with absent GABAAergic synaptic transmission. The electrically evoked activity of cultured cortical networks, therefore, is governed by at least two potentially interacting mechanisms: A refractory period in the order of a few seconds and a very slow GABA dependent oscillation of the network excitability. PMID:26236196

  3. From Synaptic Transmission to Cognition: An Intermediary Role for Dendritic Spines

    ERIC Educational Resources Information Center

    Gonzalez-Burgos, Ignacio

    2012-01-01

    Dendritic spines are cytoplasmic protrusions that develop directly or indirectly from the filopodia of neurons. Dendritic spines mediate excitatory neurotransmission and they can isolate the electrical activity generated by synaptic impulses, enabling them to translate excitatory afferent information via several types of plastic changes, including…

  4. Shank1 regulates excitatory synaptic transmission in mouse hippocampal parvalbumin-expressing inhibitory interneurons.

    PubMed

    Mao, Wenjie; Watanabe, Takuya; Cho, Sukhee; Frost, Jeffrey L; Truong, Tina; Zhao, Xiaohu; Futai, Kensuke

    2015-04-01

    The Shank genes (SHANK1, 2, 3) encode scaffold proteins highly enriched in postsynaptic densities where they regulate synaptic structure in spiny neurons. Mutations in human Shank genes are linked to autism spectrum disorder and schizophrenia. Shank1 mutant mice exhibit intriguing cognitive phenotypes reminiscent of individuals with autism spectrum disorder. However, the molecular mechanisms leading to the human pathophysiological phenotypes and mouse behaviors have not been elucidated. In this study it is shown that Shank1 protein is highly localized in parvalbumin-expressing (PV+) fast-spiking inhibitory interneurons in the hippocampus. Importantly, a lack of Shank1 in hippocampal CA1 PV+ neurons reduced excitatory synaptic inputs and inhibitory synaptic outputs to pyramidal neurons. Furthermore, it is demonstrated that hippocampal CA1 pyramidal neurons in Shank1 mutant mice exhibit a shift in the excitatory and inhibitory balance (E-I balance), a pathophysiological hallmark of autism spectrum disorder. The mutant mice also exhibit lower expression of gephyrin (a scaffold component of inhibitory synapses), supporting the dysregulation of E-I balance in the hippocampus. These results suggest that Shank1 scaffold in PV+ interneurons regulates excitatory synaptic strength and participates in the maintenance of E-I balance in excitatory neurons. PMID:25816842

  5. Dendritic morphology, synaptic transmission, and activity of mature granule cells born following pilocarpine-induced status epilepticus in the rat

    PubMed Central

    Gao, Fei; Song, Xueying; Zhu, Dexiao; Wang, Xiaochen; Hao, Aijun; Nadler, J. Victor; Zhan, Ren-Zhi

    2015-01-01

    To understand the potential role of enhanced hippocampal neurogenesis after pilocarpine-induced status epilepticus (SE) in the development of epilepsy, we quantitatively analyzed the geometry of apical dendrites, synaptic transmission, and activation levels of normotopically distributed mature newborn granule cells in the rat. SE in male Sprague-Dawley rats (between 6 and 7 weeks old) lasting for more than 2 h was induced by an intraperitoneal injection of pilocarpine. The complexity, spine density, miniature post-synaptic currents, and activity-regulated cytoskeleton-associated protein (Arc) expression of granule cells born 5 days after SE were studied between 10 and 17 weeks after CAG-GFP retroviral vector-mediated labeling. Mature granule cells born after SE had dendritic complexity similar to that of granule cells born naturally, but with denser mushroom-like spines in dendritic segments located in the outer molecular layer. Miniature inhibitory post-synaptic currents (mIPSCs) were similar between the controls and rats subjected to SE; however, smaller miniature excitatory post-synaptic current (mEPSC) amplitude with a trend toward less frequent was found in mature granule cells born after SE. After maturation, granule cells born after SE did not show denser Arc expression in the resting condition or 2 h after being activated by pentylenetetrazol-induced transient seizure activity than vicinal GFP-unlabeled granule cells. Thus our results suggest that normotopic granule cells born after pilocarpine-induced SE are no more active when mature than age-matched, naturally born granule cells. PMID:26500490

  6. Cocaine-induced neuroadaptations in the dorsal striatum: glutamate dynamics and behavioral sensitization.

    PubMed

    Parikh, Vinay; Naughton, Sean X; Shi, Xiangdang; Kelley, Leslie K; Yegla, Brittney; Tallarida, Christopher S; Rawls, Scott M; Unterwald, Ellen M

    2014-09-01

    Recent evidence suggests that diminished ability to control cocaine seeking arises from perturbations in glutamate homeostasis in the nucleus accumbens. However, the neurochemical substrates underlying cocaine-induced neuroadaptations in the dorsal striatum and how these mechanisms link to behavioral plasticity is not clear. We employed glutamate-sensitive microelectrodes and amperometry to study the impact of repeated cocaine administration on glutamate dynamics in the dorsolateral striatum of awake freely-moving rats. Depolarization-evoked glutamate release was robustly increased in cocaine-pretreated rats challenged with cocaine. Moreover, the clearance of glutamate signals elicited either by terminal depolarization or blockade of non-neuronal glutamate transporters slowed down dramatically in cocaine-sensitized rats. Repeated cocaine exposure also reduced the neuronal tone of striatal glutamate. Ceftriaxone, a β-lactam antibiotic that activates the astrocytic glutamate transporter, attenuated the effects of repeated cocaine exposure on synaptic glutamate release and glutamate clearance kinetics. Finally, the antagonism of AMPA glutamate receptors in the dorsolateral striatum blocked the development of behavioral sensitization to repeated cocaine administration. Collectively, these data suggest that repeated cocaine exposure disrupts presynaptic glutamate transmission and transporter-mediated clearance mechanisms in the dorsal striatum. Moreover, such alterations produce an over activation of AMPA receptors in this brain region leading to the sensitized behavioral response to repeated cocaine. PMID:24911954

  7. Weak endogenous Ca2+ buffering supports sustained synaptic transmission by distinct mechanisms in rod and cone photoreceptors in salamander retina

    PubMed Central

    Van Hook, Matthew J; Thoreson, Wallace B

    2015-01-01

    Differences in synaptic transmission between rod and cone photoreceptors contribute to different response kinetics in rod- versus cone-dominated visual pathways. We examined Ca2+ dynamics in synaptic terminals of tiger salamander photoreceptors under conditions that mimicked endogenous buffering to determine the influence on kinetically and mechanistically distinct components of synaptic transmission. Measurements of ICl(Ca) confirmed that endogenous Ca2+ buffering is equivalent to ˜0.05 mmol/L EGTA in rod and cone terminals. Confocal imaging showed that with such buffering, depolarization stimulated large, spatially unconstrained [Ca2+] increases that spread throughout photoreceptor terminals. We calculated immediately releasable pool (IRP) size and release efficiency in rods by deconvolving excitatory postsynaptic currents and presynaptic Ca2+ currents. Peak efficiency of ˜0.2 vesicles/channel was similar to that of cones (˜0.3 vesicles/channel). Efficiency in both cell types was not significantly affected by using weak endogenous Ca2+ buffering. However, weak Ca2+ buffering speeded Ca2+/calmodulin (CaM)-dependent replenishment of vesicles to ribbons in both rods and cones, thereby enhancing sustained release. In rods, weak Ca2+ buffering also amplified sustained release by enhancing CICR and CICR-stimulated release of vesicles at nonribbon sites. By contrast, elevating [Ca2+] at nonribbon sites in cones with weak Ca2+ buffering and by inhibiting Ca2+ extrusion did not trigger additional release, consistent with the notion that exocytosis from cones occurs exclusively at ribbons. The presence of weak endogenous Ca2+ buffering in rods and cones facilitates slow, sustained exocytosis by enhancing Ca2+/CaM-dependent replenishment of ribbons in both rods and cones and by stimulating nonribbon release triggered by CICR in rods. PMID:26416977

  8. Laser-evoked synaptic transmission in cultured hippocampal neurons expressing Channelrhodopsin-2 delivered by adeno-associated virus

    PubMed Central

    Wang, Jennifer; Hasan, Mazahir T.; Seung, H. Sebastian

    2009-01-01

    We present a method for studying synaptic transmission in mass cultures of dissociated hippocampal neurons based on patch clamp recording combined with laser stimulation of neurons expressing Channelrhodopsin-2 (ChR2). Our goal was to use the high spatial resolution of laser illumination to come as close as possible to the ideal of identifying monosynaptically coupled pairs of neurons, which is conventionally done using microisland rather than mass cultures. Using recombinant adeno-associated virus (rAAV) to deliver the ChR2 gene, we focused on the time period between 14 and 20 days in vitro, during which expression levels are high, and spontaneous bursting activity has not yet started. Stimulation by wide-field illumination is sufficient to make the majority of ChR2-expressing neurons spike. Stimulation with a laser spot at least 10 μm in diameter also produces action potentials, but in a reduced fraction of neurons. We studied synaptic transmission by voltage-clamping a neuron with low expression of ChR2 and scanning a 40 μm laser spot at surrounding locations. Responses were observed to stimulation at a subset of locations in the culture, indicating spatial localization of stimulation. Pharmacological means were used to identify responses that were synaptic. Many responses were of smaller amplitude than those typically found in microisland cultures. We were unable to find an entirely reliable criterion for distinguishing between monosynaptic and polysynaptic responses. However, we propose that postsynaptic currents with small amplitudes, simple shapes, and latencies not much greater than 8 msec are reasonable candidates for monosynaptic interactions. PMID:19560489

  9. The SOL-2/Neto auxiliary protein modulates the function of AMPA-subtype ionotropic glutamate receptors.

    PubMed

    Wang, Rui; Mellem, Jerry E; Jensen, Michael; Brockie, Penelope J; Walker, Craig S; Hoerndli, Frédéric J; Hauth, Linda; Madsen, David M; Maricq, Andres V

    2012-09-01

    The neurotransmitter glutamate mediates excitatory synaptic transmission by gating ionotropic glutamate receptors (iGluRs). AMPA receptors (AMPARs), a subtype of iGluR, are strongly implicated in synaptic plasticity, learning, and memory. We previously discovered two classes of AMPAR auxiliary proteins in C. elegans that modify receptor kinetics and thus change synaptic transmission. Here, we have identified another auxiliary protein, SOL-2, a CUB-domain protein that associates with both the related auxiliary subunit SOL-1 and with the GLR-1 AMPAR. In sol-2 mutants, behaviors dependent on glutamatergic transmission are disrupted, GLR-1-mediated currents are diminished, and GLR-1 desensitization and pharmacology are modified. Remarkably, a secreted variant of SOL-1 delivered in trans can rescue sol-1 mutants, and this rescue depends on in cis expression of SOL-2. Finally, we demonstrate that SOL-1 and SOL-2 have an ongoing role in the adult nervous system to control AMPAR-mediated currents. PMID:22958824

  10. Palmitoylation-dependent regulation of glutamate receptors and their PDZ domain-containing partners

    PubMed Central

    Thomas, Gareth M.; Huganir, Richard L.

    2013-01-01

    In recent years, it has become clear that both AMPA (α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid)- and NMDA (N-methyl-D-aspartate)-type glutamate receptors, and many of their interacting partners, are palmitoylated proteins. Interfering with palmitoylation dramatically affects receptor trafficking and distribution and, in turn, can profoundly alter synaptic transmission. Increased knowledge of synaptic palmitoylation not only will aid our understanding of physiological neuronal regulation, but also may provide insights into, and even novel treatments for, neuropathological conditions. In the present paper, we review recent advances regarding the regulation of ionotropic glutamate receptor trafficking and function by palmitoylation. PMID:23356261

  11. Nicotinic Transmission onto Layer 6 Cortical Neurons Relies on Synaptic Activation of Non-α7 Receptors.

    PubMed

    Hay, Y Audrey; Lambolez, Bertrand; Tricoire, Ludovic

    2016-06-01

    Nicotinic excitation in neocortex is mediated by low-affinity α7 receptors and by high-affinity α4β2 receptors. There is evidence that α7 receptors are synaptic, but it is unclear whether high-affinity receptors are activated by volume transmission or synaptic transmission. To address this issue, we characterized responses of excitatory layer 6 (L6) neurons to optogenetic release of acetylcholine (ACh) in cortical slices. L6 responses consisted in a slowly decaying α4β2 current and were devoid of α7 component. Evidence that these responses were mediated by synapses was 4-fold. 1) Channelrhodopsin-positive cholinergic varicosities made close appositions onto responsive neurons. 2) Inhibition of ACh degradation failed to alter onset kinetics and amplitude of currents. 3) Quasi-saturation of α4β2 receptors occurred upon ACh release. 4) Response kinetics were unchanged in low release probability conditions. Train stimulations increased amplitude and decay time of responses and these effects appeared to involve recruitment of extrasynaptic receptors. Finally, we found that the α5 subunit, known to be associated with α4β2 in L6, regulates short-term plasticity at L6 synapses. Our results are consistent with previous anatomical observations of widespread cholinergic synapses and suggest that a significant proportion of these small synapses operate via high-affinity nicotinic receptors. PMID:25934969

  12. Selective optical control of synaptic transmission in the subcortical visual pathway by activation of viral vector-expressed halorhodopsin.

    PubMed

    Kaneda, Katsuyuki; Kasahara, Hironori; Matsui, Ryosuke; Katoh, Tomoko; Mizukami, Hiroaki; Ozawa, Keiya; Watanabe, Dai; Isa, Tadashi

    2011-01-01

    The superficial layer of the superior colliculus (sSC) receives visual inputs via two different pathways: from the retina and the primary visual cortex. However, the functional significance of each input for the operation of the sSC circuit remains to be identified. As a first step toward understanding the functional role of each of these inputs, we developed an optogenetic method to specifically suppress the synaptic transmission in the retino-tectal pathway. We introduced enhanced halorhodopsin (eNpHR), a yellow light-sensitive, membrane-targeting chloride pump, into mouse retinal ganglion cells (RGCs) by intravitreously injecting an adeno-associated virus serotype-2 vector carrying the CMV-eNpHR-EYFP construct. Several weeks after the injection, whole-cell recordings made from sSC neurons in slice preparations revealed that yellow laser illumination of the eNpHR-expressing retino-tectal axons, putatively synapsing onto the recorded cells, effectively inhibited EPSCs evoked by electrical stimulation of the optic nerve layer. We also showed that sSC spike activities elicited by visual stimulation were significantly reduced by laser illumination of the sSC in anesthetized mice. These results indicate that photo-activation of eNpHR expressed in RGC axons enables selective blockade of retino-tectal synaptic transmission. The method established here can most likely be applied to a variety of brain regions for studying the function of individual inputs to these regions. PMID:21483674

  13. P2Y Receptors in Synaptic Transmission and Plasticity: Therapeutic Potential in Cognitive Dysfunction

    PubMed Central

    Guzman, Segundo J.; Gerevich, Zoltan

    2016-01-01

    ATP released from neurons and astrocytes during neuronal activity or under pathophysiological circumstances is able to influence information flow in neuronal circuits by activation of ionotropic P2X and metabotropic P2Y receptors and subsequent modulation of cellular excitability, synaptic strength, and plasticity. In the present paper we review cellular and network effects of P2Y receptors in the brain. We show that P2Y receptors inhibit the release of neurotransmitters, modulate voltage- and ligand-gated ion channels, and differentially influence the induction of synaptic plasticity in the prefrontal cortex, hippocampus, and cerebellum. The findings discussed here may explain how P2Y1 receptor activation during brain injury, hypoxia, inflammation, schizophrenia, or Alzheimer's disease leads to an impairment of cognitive processes. Hence, it is suggested that the blockade of P2Y1 receptors may have therapeutic potential against cognitive disturbances in these states. PMID:27069691

  14. Modulation of synaptic transmission by adenosine in layer 2/3 of the rat visual cortex in vitro

    PubMed Central

    Bannon, Nicholas; Zhang, Pei; Ilin, Vladimir; Chistiakova, Marina; Volgushev, Maxim

    2014-01-01

    Adenosine is a wide-spread endogenous neuromodulator. In the central nervous system it activates A1 and A2A receptors (A1Rs and A2ARs) which have differential distributions, different affinities to adenosine, are coupled to different G-proteins, and have opposite effects on synaptic transmission. Although effects of adenosine are studied in detail in several brain areas, such as hippocampus and striatum, the heterogeneity of the effects of A1R and A 2A R activation and their differential distribution preclude generalization over brain areas and cell types. Here we study adenosine's effects on excitatory synaptic transmission to layer 2/3 pyramidal neurons in slices of the rat visual cortex. We measured effects of bath application of adenosine receptor ligands on evoked EPSPs, miniature EPSPs (mEPSPs), and membrane properties. Adenosine reduced the amplitude of evoked EPSPs and EPSCs, and reduced frequency of mEPSPs in a concentration dependent and reversible manner. Concurrent with EPSP/C amplitude reduction was an increase in the paired-pulse ratio. These effects were blocked by application of the selective A1R antagonist DPCPX, suggesting that activation of presynaptic A1Rs suppresses excitatory transmission by reducing release probability. Adenosine (20 μM) hyperpolarized the cell membrane from 65.3±1.5 to -67.7±1.8 mV, and reduced input resistance from 396.5±44.4 to 314.0±36.3 MOhm (~20%). These effects were also abolished by DPCPX, suggesting postsynaptic A1Rs. Application of the selective A2AR antagonist SCH-58261 on the background of high adenosine concentrations revealed an additional decrease in EPSP amplitude. Moreover, application of the A2AR agonist CGS-21680 led to an A1R-dependent increase in mEPSP frequency. Dependence of the A2AR effects on the A1R availability suggests interaction between these receptors, whereby A2ARs exert their facilitatory effect on synaptic transmission by inhibiting the A1R mediated suppression. Our results demonstrate

  15. Membrane-tethered AKT kinase regulates basal synaptic transmission and early phase LTP expression by modulation of post-synaptic AMPA receptor level.

    PubMed

    Pen, Y; Borovok, N; Reichenstein, M; Sheinin, A; Michaelevski, I

    2016-09-01

    The serine/threonine kinase AKT/PKB plays a fundamental role in a wide variety of neuronal functions, including neuronal cell development, axonal growth, and synaptic plasticity. Multiple evidence link AKT signaling pathways to regulation of late phase long-term synaptic plasticity, synaptogenesis, and spinogenesis, as well as long-term memory formation. Nevertheless, the downstream effectors mediating the effects of AKT on early phase long-term potentiation (eLTP) are currently unknown. Here we report that using different regimes of pharmacological activation and inhibition of AKT activity in acute hippocampal slices, we found that AKT regulates the post-synaptic expression of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPA) receptors affecting solely the expression of eLTP, with no effect on its induction and maintenance. We further show that both maintenance of basal synaptic activity and expression of eLTP require plasma membrane tethering by activated AKT and that basal synaptic activity may be regulated via the direct effects of AKT1 on the expression level of post-synaptic AMPA receptors bypassing the canonical AKT signaling. Finally, we establish that eLTP expression requires the involvement of both the canonical AKT signaling pathways and the direct effect of AKT1 on AMPA receptor activity/expression in the post-synaptic membrane. © 2016 Wiley Periodicals, Inc. PMID:27068236

  16. Layer- and area-specific actions of norepinephrine on cortical synaptic transmission.

    PubMed

    Salgado, Humberto; Treviño, Mario; Atzori, Marco

    2016-06-15

    The cerebral cortex is a critical target of the central noradrenergic system. The importance of norepinephrine (NE) in the regulation of cortical activity is underscored by clinical findings that involve this catecholamine and its receptor subtypes in the regulation of a large number of emotional and cognitive functions and illnesses. In this review, we highlight diverse effects of the LC/NE system in the mammalian cortex. Indeed, electrophysiological, pharmacological, and behavioral studies in the last few decades reveal that NE elicits a mixed repertoire of excitatory, inhibitory, and biphasic effects on the firing activity and transmitter release of cortical neurons. At the intrinsic cellular level, NE can produce a series of effects similar to those elicited by other monoamines or acetylcholine, associated with systemic arousal. At the synaptic level, NE induces numerous acute changes in synaptic function, and ׳gates' the induction of long-term plasticity of glutamatergic synapses, consisting in an enhancement of engaged and relevant cortical synapses and/or depression of unengaged synapses. Equally important in shaping cortical function, in many cortical areas NE promotes a characteristic, most often reversible, increase in the gain of local inhibitory synapses, whose extent and temporal properties vary between different areas and sometimes even between cortical layers of the same area. While we are still a long way from a comprehensive theory of the function of the LC/NE system, its cellular, synaptic, and plastic effects are consistent with the hypothesis that noradrenergic modulation is critical in coordinating the activity of cortical and subcortical circuits for the integration of sensory activity and working memory. This article is part of a Special Issue entitled SI: Noradrenergic System. PMID:26820639

  17. EPO induces changes in synaptic transmission and plasticity in the dentate gyrus of rats.

    PubMed

    Almaguer-Melian, William; Mercerón-Martínez, Daymara; Delgado-Ocaña, Susana; Pavón-Fuentes, Nancy; Ledón, Nuris; Bergado, Jorge A

    2016-06-01

    Erythropoietin has shown wide physiological effects on the central nervous system in animal models of disease, and in healthy animals. We have recently shown that systemic EPO administration 15 min, but not 5 h, after daily training in a water maze is able to induce the recovery of spatial memory in fimbria-fornix chronic-lesioned animals, suggesting that acute EPO triggers mechanisms which can modulate the active neural plasticity mechanism involved in spatial memory acquisition in lesioned animals. Additionally, this EPO effect is accompanied by the up-regulation of plasticity-related early genes. More remarkably, this time-dependent effects on learning recovery could signify that EPO in nerve system modulate specific living-cellular processes. In the present article, we focus on the question if EPO could modulate the induction of long-term synaptic plasticity like LTP and LTD, which presumably could support our previous published data. Our results show that acute EPO peripheral administration 15 min before the induction of synaptic plasticity is able to increase the magnitude of the LTP (more prominent in PSA than fEPSP-Slope) to facilitate the induction of LTD, and to protect LTP from depotentiation. These findings showing that EPO modulates in vivo synaptic plasticity sustain the assumption that EPO can act not only as a neuroprotective substance, but is also able to modulate transient neural plasticity mechanisms and therefore to promote the recovery of nerve function after an established chronic brain lesion. According to these results, EPO could be use as a molecular tool for neurorestaurative treatments. Synapse 70:240-252, 2016. © 2016 Wiley Periodicals, Inc. PMID:26860222

  18. Autism-Associated Insertion Mutation (InsG) of Shank3 Exon 21 Causes Impaired Synaptic Transmission and Behavioral Deficits.

    PubMed

    Speed, Haley E; Kouser, Mehreen; Xuan, Zhong; Reimers, Jeremy M; Ochoa, Christine F; Gupta, Natasha; Liu, Shunan; Powell, Craig M

    2015-07-01

    SHANK3 (also known as PROSAP2) is a postsynaptic scaffolding protein at excitatory synapses in which mutations and deletions have been implicated in patients with idiopathic autism, Phelan-McDermid (aka 22q13 microdeletion) syndrome, and other neuropsychiatric disorders. In this study, we have created a novel mouse model of human autism caused by the insertion of a single guanine nucleotide into exon 21 (Shank3(G)). The resulting frameshift causes a premature STOP codon and loss of major higher molecular weight Shank3 isoforms at the synapse. Shank3(G/G) mice exhibit deficits in hippocampus-dependent spatial learning, impaired motor coordination, altered response to novelty, and sensory processing deficits. At the cellular level, Shank3(G/G) mice also exhibit impaired hippocampal excitatory transmission and plasticity as well as changes in baseline NMDA receptor-mediated synaptic responses. This work identifies clear alterations in synaptic function and behavior in a novel, genetically accurate mouse model of autism mimicking an autism-associated insertion mutation. Furthermore, these findings lay the foundation for future studies aimed to validate and study region-selective and temporally selective genetic reversal studies in the Shank3(G/G) mouse that was engineered with such future experiments in mind. PMID:26134648

  19. Loss of Predominant Shank3 Isoforms Results in Hippocampus-Dependent Impairments in Behavior and Synaptic Transmission

    PubMed Central

    Kouser, Mehreen; Speed, Haley E.; Dewey, Colleen M.; Reimers, Jeremy M.; Widman, Allie J.; Gupta, Natasha; Liu, Shunan; Jaramillo, Thomas C.; Bangash, Muhammad; Xiao, Bo; Worley, Paul F.

    2013-01-01

    The Shank3 gene encodes a scaffolding protein that anchors multiple elements of the postsynaptic density at the synapse. Previous attempts to delete the Shank3 gene have not resulted in a complete loss of the predominant naturally occurring Shank3 isoforms. We have now characterized a homozygous Shank3 mutation in mice that deletes exon 21, including the Homer binding domain. In the homozygous state, deletion of exon 21 results in loss of the major naturally occurring Shank3 protein bands detected by C-terminal and N-terminal antibodies, allowing us to more definitively examine the role of Shank3 in synaptic function and behavior. This loss of Shank3 leads to an increased localization of mGluR5 to both synaptosome and postsynaptic density-enriched fractions in the hippocampus. These mice exhibit a decrease in NMDA/AMPA excitatory postsynaptic current ratio in area CA1 of the hippocampus, reduced long-term potentiation in area CA1, and deficits in hippocampus-dependent spatial learning and memory. In addition, these mice also exhibit motor-coordination deficits, hypersensitivity to heat, novelty avoidance, altered locomotor response to novelty, and minimal social abnormalities. These data suggest that Shank3 isoforms are required for normal synaptic transmission/plasticity in the hippocampus, as well as hippocampus-dependent spatial learning and memory. PMID:24259569

  20. Autism-Associated Insertion Mutation (InsG) of Shank3 Exon 21 Causes Impaired Synaptic Transmission and Behavioral Deficits

    PubMed Central

    Speed, Haley E.; Kouser, Mehreen; Xuan, Zhong; Reimers, Jeremy M.; Ochoa, Christine F.; Gupta, Natasha; Liu, Shunan

    2015-01-01

    SHANK3 (also known as PROSAP2) is a postsynaptic scaffolding protein at excitatory synapses in which mutations and deletions have been implicated in patients with idiopathic autism, Phelan–McDermid (aka 22q13 microdeletion) syndrome, and other neuropsychiatric disorders. In this study, we have created a novel mouse model of human autism caused by the insertion of a single guanine nucleotide into exon 21 (Shank3G). The resulting frameshift causes a premature STOP codon and loss of major higher molecular weight Shank3 isoforms at the synapse. Shank3G/G mice exhibit deficits in hippocampus-dependent spatial learning, impaired motor coordination, altered response to novelty, and sensory processing deficits. At the cellular level, Shank3G/G mice also exhibit impaired hippocampal excitatory transmission and plasticity as well as changes in baseline NMDA receptor-mediated synaptic responses. This work identifies clear alterations in synaptic function and behavior in a novel, genetically accurate mouse model of autism mimicking an autism-associated insertion mutation. Furthermore, these findings lay the foundation for future studies aimed to validate and study region-selective and temporally selective genetic reversal studies in the Shank3G/G mouse that was engineered with such future experiments in mind. PMID:26134648

  1. Fear Conditioning Potentiates Synaptic Transmission onto Long-Range Projection Neurons in the Lateral Subdivision of Central Amygdala

    PubMed Central

    Penzo, Mario A.; Robert, Vincent

    2014-01-01

    Recent studies indicate that the lateral subdivision of the central amygdala (CeL) is essential for fear learning. Specifically, fear conditioning induces cell-type-specific synaptic plasticity in CeL neurons that is required for the storage of fear memories. The CeL also controls fear expression by gating the activity of the medial subdivision of the central amygdala (CeM), the canonical amygdala output to areas that mediate defensive responses. In addition to the connection with CeM, the CeL sends long-range projections to innervate extra-amygdala areas. However, the long-range projection CeL neurons have not been well characterized, and their role in fear regulation is unknown. Here we show in mice that a subset of CeL neurons directly project to the midbrain periaqueductal gray (PAG) and the paraventricular nucleus of the thalamus, two brain areas implicated in defensive behavior. These long-range projection CeL neurons are predominantly somatostatin-positive (SOM+) neurons, which can directly inhibit PAG neurons, and some of which innervate both the PAG and paraventricular nucleus of the thalamus. Notably, fear conditioning potentiates excitatory synaptic transmission onto these long-range projection CeL neurons. Thus, our study identifies a subpopulation of SOM+ CeL neurons that may contribute to fear learning and regulate fear expression independent of CeM. PMID:24523533

  2. DISC1 Protein Regulates γ-Aminobutyric Acid, Type A (GABAA) Receptor Trafficking and Inhibitory Synaptic Transmission in Cortical Neurons.

    PubMed

    Wei, Jing; Graziane, Nicholas M; Gu, Zhenglin; Yan, Zhen

    2015-11-13

    Association studies have suggested that Disrupted-in-Schizophrenia 1 (DISC1) confers a genetic risk at the level of endophenotypes that underlies many major mental disorders. Despite the progress in understanding the significance of DISC1 at neural development, the mechanisms underlying DISC1 regulation of synaptic functions remain elusive. Because alterations in the cortical GABA system have been strongly linked to the pathophysiology of schizophrenia, one potential target of DISC1 that is critically involved in the regulation of cognition and emotion is the GABAA receptor (GABAAR). We found that cellular knockdown of DISC1 significantly reduced GABAAR-mediated synaptic and whole-cell current, whereas overexpression of wild-type DISC1, but not the C-terminal-truncated DISC1 (a schizophrenia-related mutant), significantly increased GABAAR currents in pyramidal neurons of the prefrontal cortex. These effects were accompanied by DISC1-induced changes in surface GABAAR expression. Moreover, the regulation of GABAARs by DISC1 knockdown or overexpression depends on the microtubule motor protein kinesin 1 (KIF5). Our results suggest that DISC1 exerts an important effect on GABAergic inhibitory transmission by regulating KIF5/microtubule-based GABAAR trafficking in the cortex. The knowledge gained from this study would shed light on how DISC1 and the GABA system are linked mechanistically and how their interactions are critical for maintaining a normal mental state. PMID:26424793

  3. TARP phosphorylation regulates synaptic AMPA receptors through lipid bilayers

    PubMed Central

    Sumioka, Akio; Yan, Dan; Tomita, Susumu

    2010-01-01

    Summary Neurons use neurotransmitters to communicate across synapses, constructing neural circuits in the brain. AMPA-type glutamate receptors are the predominant excitatory neurotransmitter receptors mediating fast synaptic transmission. AMPA receptors localize at synapses by forming protein complexes with transmembrane AMPA receptor regulatory proteins (TARPs) and PSD-95-like MAGUKs. Among the three classes of ionotropic glutamate receptors (AMPA-, NMDA, kainate-type), AMPA receptor activity is most regulatable by neuronal activity to adjust synaptic strength. Here, we mutated the prototypical TARP, stargazin, and found that TARP phosphorylation regulates synaptic AMPA receptor activity in vivo. We also found that stargazin interacts with negatively-charged lipid bilayers in its phosphorylation dependent manner, and that the lipid interaction inhibited stargazin binding to PSD-95. Cationic lipids dissociated stargazin from lipid bilayers and enhanced synaptic AMPA receptor activity in a stargazin phosphorylation-dependent manner. Thus, TARP phosphorylation plays a critical role in regulating AMPA receptor-mediated synaptic transmission via a lipid bilayer interaction. PMID:20547132

  4. A review of glutamate's role in traumatic brain injury mechanisms

    NASA Astrophysics Data System (ADS)

    Good, Cameron H.

    2013-05-01

    Glutamate is the primary excitatory neurotransmitter used by the central nervous system (CNS) for synaptic communication, and its extracellular concentration is tightly regulated by glutamate transporters located on nearby astrocytes. Both animal models and human clinical studies have demonstrated elevated glutamate levels immediately following a traumatic brain event, with the duration and severity of the rise corresponding to prognosis. This rise in extracellular glutamate likely results from a combination of excessive neurotransmitter release from damaged neurons and down regulation of uptake mechanisms in local astrocytes. The immediate results of a traumatic event can lead to necrotic tissue in severely injured regions, while prolonged increases in excitatory transmission can cause secondary excitotoxic injury through activation of delayed apoptotic pathways. Initial TBI animal studies utilized a variety of broad glutamate receptor antagonists to successfully combat secondary injury mechanisms, but unfortunately this same strategy has proven inconclusive in subsequent human trials due to deleterious side effects and heterogeneity of injuries. More recent treatment strategies have utilized specific glutamate receptor subunit antagonists in an effort to minimize side effects and have shown promising results. Future challenges will be detecting the concentration and kinetics of the glutamate rise following injury, determining which patient populations could benefit from antagonist treatment based on their extracellular glutamate concentrations and when drugs should be administered to maximize efficacy.

  5. Similar oxysterols may lead to opposite effects on synaptic transmission: Olesoxime versus 5α-cholestan-3-one at the frog neuromuscular junction.

    PubMed

    Kasimov, M R; Zakyrjanova, G F; Giniatullin, A R; Zefirov, A L; Petrov, A M

    2016-07-01

    Cholesterol oxidation products frequently have a high biological activity. In the present study, we have used microelectrode recording of end plate currents and FM-based optical detection of synaptic vesicle exo-endocytosis to investigate the effects of two structurally similar oxysterols, olesoxime (cholest-4-en-3-one, oxime) and 5ɑ-cholestan-3-one (5ɑCh3), on neurotransmission at the frog neuromuscular junction. Olesoxime is an exogenous, potentially neuroprotective, substance and 5ɑCh3 is an intermediate product in cholesterol metabolism, which is elevated in the case of cerebrotendinous xanthomatosis. We found that olesoxime slightly increased evoked neurotransmitter release in response to a single stimulus and significantly reduced synaptic depression during high frequency activity. The last effect was due to an increase in both the number of synaptic vesicles involved in exo-endocytosis and the rate of synaptic vesicle recycling. In contrast, 5ɑCh3 reduced evoked neurotransmitter release during the low- and high frequency synaptic activities. The depressant action of 5ɑCh3 was associated with a reduction in the number of synaptic vesicles participating in exo- and endocytosis during high frequency stimulation, without a change in rate of the synaptic vesicle recycling. Of note, olesoxime increased the staining of synaptic membranes with the B-subunit of cholera toxin and the formation of fluorescent ganglioside GM1 clusters, and decreased the fluorescence of 22-NBD-cholesterol, while 5ɑCh3 had the opposite effects, suggesting that the two oxysterols have different effects on lipid raft stability. Taken together, these data show that these two structurally similar oxysterols induce marked different changes in neuromuscular transmission which are related with the alteration in synaptic vesicle cycle. PMID:27102612

  6. Investigation of the juxtamembrane region of neuronal-Synaptobrevin in synaptic transmission at the Drosophila neuromuscular junction.

    PubMed

    DeMill, Colin M; Qiu, Xinping; Kisiel, Marta; Bolotta, Alanna; Stewart, Bryan A

    2014-09-15

    In this study, the juxtamembrane region of the Drosophila SNARE protein neuronal-Synaptobrevin (n-Syb) was tested for its role in synaptic transmission. A transgenic approach was used to express n-Syb mutant genes. The transgenes carried engineered point mutations that alter the amino acid sequence of the conserved tryptophan residues in the juxtamembrane sequence. Such transgenes were expressed in an n-syb hypomorphic background, which produces little endogenous protein. On their own, hypomorphic flies displayed severe motor inhibition, limited life span, reduced evoked junctional potentials (EJPs), decreased synchronicity in EJP time to peak, and potentiation of EJPs with 10-Hz stimulation. All of these deficits were restored to wild-type levels with the expression of wild-type transgenic n-syb, regulated by the endogenous promoter (n-syb(WT)). We created transgenic mutants with one additional tryptophan (n-syb(WW)) or one less tryptophan (n-syb(AA)) than the wild-type sequence. While n-syb(WW) resembled n-syb(WT) in all variables listed, n-syb(AA) exhibited decreased EJP amplitude, synchronicity, and quantal content. To determine whether the n-syb juxtamembrane region is important for transduction of force arising from SNARE complex assembly during membrane fusion, we introduced short 6-amino acid (n-syb(L6)) or long 24-amino acid (n-syb(L24)) flexible linkers into the n-syb transgene. We observed a reduced EJP amplitude in n-syb(L6) but not n-syb(L24), while both linker mutants showed a decreased quantal content and an effect on the readily releasable and recycling vesicle pools. In conclusion, mutation of the juxtamembrane region of n-syb deleteriously affected synaptic transmission at the Drosophila neuromuscular junction. PMID:24944220

  7. Enhanced GABAergic synaptic transmission at VLPAG neurons and potent modulation by oxycodone in a bone cancer pain model

    PubMed Central

    Takasu, Keiko; Ogawa, Koichi; Nakamura, Atsushi; Kanbara, Tomoe; Ono, Hiroko; Tomii, Takako; Morioka, Yasuhide; Hasegawa, Minoru; Shibasaki, Masahiro; Mori, Tomohisa; Suzuki, Tsutomu; Sakaguchi, Gaku

    2015-01-01

    Background and Purpose We demonstrated previously that oxycodone has potent antinociceptive effects at supraspinal sites. In this study, we investigated changes in neuronal function and antinociceptive mechanisms of oxycodone at ventrolateral periaqueductal gray (VLPAG) neurons, which are a major site of opioid action, in a femur bone cancer (FBC) model with bone cancer-related pain. Experimental Approach We characterized the supraspinal antinociceptive profiles of oxycodone and morphine on mechanical hypersensitivity in the FBC model. Based on the disinhibition mechanism underlying supraspinal opioid antinociception, the effects of oxycodone and morphine on GABAA receptor-mediated inhibitory postsynaptic currents (IPSCs) in VLPAG neurons were evaluated in slices from the FBC model. Key Results The supraspinal antinociceptive effects of oxycodone, but not morphine, were abolished by blocking G protein-gated inwardly rectifying potassium1 (Kir3.1) channels. In slices from the FBC model, GABAergic synaptic transmission at VLPAG neurons was enhanced, as indicated by a leftward shift of the input–output relationship curve of evoked IPSCs, the increased paired-pulse facilitation and the enhancement of miniature IPSC frequency. Following treatment with oxycodone and morphine, IPSCs were reduced in the FBC model, and the inhibition of presynaptic GABA release by oxycodone, but not morphine was enhanced and dependent on Kir3.1 channels. Conclusion and Implications Our results demonstrate that Kir3.1 channels are important for supraspinal antinociception and presynaptic GABA release inhibition by oxycodone in the FBC model. Enhanced GABAergic synaptic transmission at VLPAG neurons in the FBC model is an important site of supraspinal antinociception by oxycodone via Kir3.1 channel activation. PMID:25521524

  8. Glutamate co-transmission from developing medial nucleus of the trapezoid body - Lateral superior olive synapses is cochlear dependent in kanamycin-treated rats

    SciTech Connect

    Lee, Jae Ho; Pradhan, Jonu; Maskey, Dhiraj; Park, Ki Sup; Hong, Sung Hwa; Suh, Myung-Whan; Kim, Myeung Ju; Ahn, Seung Cheol

    2011-02-11

    Research highlights: {yields} Glutamate co-transmission is enhanced in kanamycin-treated rats. {yields} VGLUT3 expression is increased in kanamycin-treated rats. {yields} GlyR expression is decreased in kanamycin-treated rats. {yields} GlyR, VGLUT3 expression patterns are asymmetric in unilaterally cochlear ablated rat. -- Abstract: Cochlear dependency of glutamate co-transmission at the medial nucleus of the trapezoid body (MNTB) - the lateral superior olive (LSO) synapses was investigated using developing rats treated with high dose kanamycin. Rats were treated with kanamycin from postnatal day (P) 3 to P8. A scanning electron microscopic study on P9 demonstrated partial cochlear hair cell damage. A whole cell voltage clamp experiment demonstrated the increased glutamatergic portion of postsynaptic currents (PSCs) elicited by MNTB stimulation in P9-P11 kanamycin-treated rats. The enhanced VGLUT3 immunoreactivities (IRs) in kanamycin-treated rats and asymmetric VGLUT3 IRs in the LSO of unilaterally cochlear ablated rats supported the electrophysiologic data. Taken together, it is concluded that glutamate co-transmission is cochlear-dependent and enhanced glutamate co-transmission in kanamycin-treated rats is induced by partial cochlear damage.

  9. Modulatory effects of serotonin on glutamatergic synaptic transmission and long-term depression in the deep cerebellar nuclei.

    PubMed

    Murano, M; Saitow, F; Suzuki, H

    2011-01-13

    The deep cerebellar nuclei (DCN) are the terminal components of the cerebellar circuitry and constitute its primary output structure. Their activity is important for certain forms of motor learning as well as generation and control of movement. DCN neurons receive glutamatergic excitatory inputs from the pontine nuclei via mossy fibres (MFs) and concomitantly receive inputs from 5-HT-containing neurons of the raphe nuclei. We aimed to explore the roles of 5-HT at MF-DCN synapses by using cerebellar slices from 11 to 15-day-old rats. Bath application of 5-HT reversibly decreased the amplitude of stimulation-evoked excitatory postsynaptic currents (eEPSCs) via the activation of 5-HT1B receptors at the presynaptic terminals of the MFs. Burst stimulation of the MFs elicited long-term depression (LTD) at the MF-DCN synapses that require activation of the group I metabotropic glutamate receptor (mGluR). In the presence of 5-HT, the extent of burst-induced LTD of MF EPSCs was significantly reduced. Application of 5-HT also decreased the amplitude of mGluR-dependent slow EPSCs evoked by similar burst stimulation. Furthermore, (S)-3,5-dihydroxyphenylglycine (DHPG), a group I mGluR agonist, induced chemical LTD of MF EPSCs, and 5-HT had no significant effect on this LTD. Taken together, the results suggest that 5-HT not only has transitory inhibitory effects on MF EPSCs but also plays a role in regulating the long-term synaptic efficacy. PMID:20969929

  10. Prefrontal glutamate correlates of methamphetamine sensitization and preference.

    PubMed

    Lominac, Kevin D; Quadir, Sema G; Barrett, Hannah M; McKenna, Courtney L; Schwartz, Lisa M; Ruiz, Paige N; Wroten, Melissa G; Campbell, Rianne R; Miller, Bailey W; Holloway, John J; Travis, Katherine O; Rajasekar, Ganesh; Maliniak, Dan; Thompson, Andrew B; Urman, Lawrence E; Kippin, Tod E; Phillips, Tamara J; Szumlinski, Karen K

    2016-03-01

    Methamphetamine (MA) is a widely misused, highly addictive psychostimulant that elicits pronounced deficits in neurocognitive function related to hypo-functioning of the prefrontal cortex (PFC). Our understanding of how repeated MA impacts excitatory glutamatergic transmission within the PFC is limited, as is information about the relationship between PFC glutamate and addiction vulnerability/resiliency. In vivo microdialysis and immunoblotting studies characterized the effects of MA (ten injections of 2 mg/kg, i.p.) upon extracellular glutamate in C57BL/6J mice and upon glutamate receptor and transporter expression, within the medial PFC. Glutamatergic correlates of both genetic and idiopathic variance in MA preference/intake were determined through studies of high vs. low MA-drinking selectively bred mouse lines (MAHDR vs. MALDR, respectively) and inbred C57BL/6J mice exhibiting spontaneously divergent place-conditioning phenotypes. Repeated MA sensitized drug-induced glutamate release and lowered indices of N-methyl-d-aspartate receptor expression in C57BL/6J mice, but did not alter basal extracellular glutamate content or total protein expression of Homer proteins, or metabotropic or α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid glutamate receptors. Elevated basal glutamate, blunted MA-induced glutamate release and ERK activation, as well as reduced protein expression of mGlu2/3 and Homer2a/b were all correlated biochemical traits of selection for high vs. low MA drinking, and Homer2a/b levels were inversely correlated with the motivational valence of MA in C57BL/6J mice. These data provide novel evidence that repeated, low-dose MA is sufficient to perturb pre- and post-synaptic aspects of glutamate transmission within the medial PFC and that glutamate anomalies within this region may contribute to both genetic and idiopathic variance in MA addiction vulnerability/resiliency. PMID:26742098

  11. Postnatal down-regulation of the GABAA receptor γ2 subunit in neocortical NG2 cells accompanies synaptic-to-extrasynaptic switch in the GABAergic transmission mode.

    PubMed

    Balia, Maddalena; Vélez-Fort, Mateo; Passlick, Stefan; Schäfer, Christoph; Audinat, Etienne; Steinhäuser, Christian; Seifert, Gerald; Angulo, María Cecilia

    2015-04-01

    NG2 cells, a main pool of glial progenitors, express γ-aminobutyric acid A (GABA(A)) receptors (GABA(A)Rs), the functional and molecular properties of which are largely unknown. We recently reported that transmission between GABAergic interneurons and NG2 cells drastically changes during development of the somatosensory cortex, switching from synaptic to extrasynaptic communication. Since synaptic and extrasynaptic GABA(A)Rs of neurons differ in their subunit composition, we hypothesize that GABA(A)Rs of NG2 cells undergo molecular changes during cortical development accompanying the switch of transmission modes. Single-cell RT-PCR and the effects of zolpidem and α5IA on evoked GABAergic currents reveal the predominance of functional α1- and α5-containing GABA(A)Rs at interneuron-NG2 cell synapses in the second postnatal week, while the α5 expression declines later in development when responses are exclusively extrasynaptic. Importantly, pharmacological and molecular analyses demonstrate that γ2, a subunit contributing to the clustering of GABA(A)Rs at postsynaptic sites in neurons, is down-regulated in NG2 cells in a cell type-specific manner in concomitance with the decline of synaptic activity and the switch of transmission mode. In keeping with the synaptic nature of γ2 in neurons, the down-regulation of this subunit is an important molecular hallmark of the change of transmission modes between interneurons and NG2 cells during development. PMID:24217990

  12. Synaptic Vesicle Endocytosis

    PubMed Central

    Saheki, Yasunori; De Camilli, Pietro

    2012-01-01

    Neurons can sustain high rates of synaptic transmission without exhausting their supply of synaptic vesicles. This property relies on a highly efficient local endocytic recycling of synaptic vesicle membranes, which can be reused for hundreds, possibly thousands, of exo-endocytic cycles. Morphological, physiological, molecular, and genetic studies over the last four decades have provided insight into the membrane traffic reactions that govern this recycling and its regulation. These studies have shown that synaptic vesicle endocytosis capitalizes on fundamental and general endocytic mechanisms but also involves neuron-specific adaptations of such mechanisms. Thus, investigations of these processes have advanced not only the field of synaptic transmission but also, more generally, the field of endocytosis. This article summarizes current information on synaptic vesicle endocytosis with an emphasis on the underlying molecular mechanisms and with a special focus on clathrin-mediated endocytosis, the predominant pathway of synaptic vesicle protein internalization. PMID:22763746

  13. Cholinergic Synaptic Transmissions Were Altered after Single Sevoflurane Exposure in Drosophila Pupa

    PubMed Central

    Chen, Rongfa; Zhang, Tao; Kuang, Liting; Chen, Zhen; Ran, Dongzhi; Niu, Yang; Gu, Huaiyu

    2015-01-01

    Purpose. Sevoflurane, one of the most used general anesthetics, is widely used in clinical practice all over the world. Previous studies indicated that sevoflurane could induce neuron apoptosis and neural deficit causing query in the safety of anesthesia using sevoflurane. The present study was designed to investigate the effects of sevoflurane on electrophysiology in Drosophila pupa whose excitatory neurotransmitter is acetylcholine early after sevoflurane exposure using whole brain recording technique. Methods. Wide types of Drosophila (canton-s flies) were allocated to control and sevoflurane groups randomly. Sevoflurane groups (1% sevoflurane; 2% sevoflurane; 3% sevoflurane) were exposed to sevoflurane and the exposure lasted 5 hours, respectively. All flies were subjected to electrophysiology experiment using patch clamp 24 hours after exposure. Results. The results showed that, 24 hours after sevoflurane exposure, frequency but not the amplitude of miniature excitatory postsynaptic currents (mEPSCs) was significantly reduced (P < 0.05). Furthermore, we explored the underlying mechanism and found that calcium currents density, which partially regulated the frequency of mEPSCs, was significantly reduced after sevoflurane exposure (P < 0.05). Conclusions. All these suggested that sevoflurane could alter the mEPSCs that are related to synaptic plasticity partially through modulating calcium channel early after sevoflurane exposure. PMID:25705662

  14. Inhibitory synaptic transmission from the substantia nigra pars reticulata to the ventral medial thalamus in mice.

    PubMed

    Kase, Daisuke; Uta, Daisuke; Ishihara, Hiromi; Imoto, Keiji

    2015-08-01

    The cortico-basal ganglia-thalamic loop circuit is involved in variety of motor, association and limbic functions. The basal ganglia receive neural information from various areas of the cerebral cortex and transfer them back to the frontal and motor cortex via the ventral medial (VM), and the anterior-ventral lateral thalamic complex. The projection from the basal ganglia to the thalamus is GABAergic, and, therefore, the output from the basal ganglia cannot directly evoke excitation in the thalamic nuclei. The mechanism underlying the information transfer via the inhibitory projection remains unclear. To address this issue, we recorded electrophysiological properties of nigro-thalamic synapses from the VM neuron. We developed a nigro-thalamic slice preparation, in which the projection from the substantia nigra pars reticulata (SNr) to VM nucleus is stored, to enable the selective activation of the projection from the SNr. We characterized synaptic properties and membrane properties of the VM neuron, and developed a VM neuron model to simulate the impacts of SNr inputs on VM neuron activity. Neural simulation suggested that the inhibitory projection from SNr can control neural activity in two ways: a disinhibition from the spontaneous nigral inhibition and a β-band synchronization evoked by combination of excitation and inhibition of SNr activity. PMID:25887794

  15. A study of the oligomeric state of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-preferring glutamate receptors in the synaptic junctions of porcine brain.

    PubMed

    Wu, T Y; Liu, C I; Chang, Y C

    1996-11-01

    The number of the subunits in an alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-preferring L-glutamate receptor in the synaptic junctions of porcine brain was investigated in this study. Upon incubation of the synaptic junctions with three cross-linking regents, dimethyl adipimidate (DMA), dimethyl suberimidate (DMS) and N-succinimidyl-(4-azidophenyl)-1,3'-dithiopropionate (SADP), AMPA receptor subunits in higher-molecular-mass aggregates were detected by immunoblotting. These aggregates migrated as proteins of approx. 200, 300 and 400 kDa. The number and identity of the subunits in a solubilized AMPA receptor were also investigated here. Two samples, W1 and W2, enriched in AMPA receptors were prepared from synaptic junctions by a combination of detergent-solubilization, anion-exchange chromatography and wheatgerm agglutinin affinity chromatography. Hydrodynamic behaviour analyses revealed that the majority of the AMPA receptors in either one of these samples were asymmetrical detergent-surrounded particles with a protein mass around 350 kDa. SDS/PAGE analysis revealed that the majority of AMPA receptors in the W1 sample were comprised of dimers of 106 kDa subunits which were covalently linked by disulphide bonds. Cross-linking these receptors with SADP yielded a new band of approx. 400 kDa. The results obtained here, either from the studies of AMPA receptors embedding in synaptic junctions or from those of detergent-solubilized and partially purified receptors, suggest that AMPA receptors contain a basic core structure comprising of four 106 kDa subunits. PMID:8920974

  16. A study of the oligomeric state of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-preferring glutamate receptors in the synaptic junctions of porcine brain.

    PubMed Central

    Wu, T Y; Liu, C I; Chang, Y C

    1996-01-01

    The number of the subunits in an alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-preferring L-glutamate receptor in the synaptic junctions of porcine brain was investigated in this study. Upon incubation of the synaptic junctions with three cross-linking regents, dimethyl adipimidate (DMA), dimethyl suberimidate (DMS) and N-succinimidyl-(4-azidophenyl)-1,3'-dithiopropionate (SADP), AMPA receptor subunits in higher-molecular-mass aggregates were detected by immunoblotting. These aggregates migrated as proteins of approx. 200, 300 and 400 kDa. The number and identity of the subunits in a solubilized AMPA receptor were also investigated here. Two samples, W1 and W2, enriched in AMPA receptors were prepared from synaptic junctions by a combination of detergent-solubilization, anion-exchange chromatography and wheatgerm agglutinin affinity chromatography. Hydrodynamic behaviour analyses revealed that the majority of the AMPA receptors in either one of these samples were asymmetrical detergent-surrounded particles with a protein mass around 350 kDa. SDS/PAGE analysis revealed that the majority of AMPA receptors in the W1 sample were comprised of dimers of 106 kDa subunits which were covalently linked by disulphide bonds. Cross-linking these receptors with SADP yielded a new band of approx. 400 kDa. The results obtained here, either from the studies of AMPA receptors embedding in synaptic junctions or from those of detergent-solubilized and partially purified receptors, suggest that AMPA receptors contain a basic core structure comprising of four 106 kDa subunits. PMID:8920974

  17. Mutation of Drosophila Focal Adhesion Kinase Induces Bang-Sensitive Behavior and Disrupts Glial Function, Axonal Conduction and Synaptic Transmission

    PubMed Central

    Ueda, Atsushi; Grabbe, Caroline; Lee, Jihye; Lee, Jisue; Palmer, Ruth H.; Wu, Chun-Fang

    2009-01-01

    The role of the conserved Focal Adhesion Kinase (FAK) family of protein tyrosine kinases (PTKs) in the development and physiological functions of the CNS has long been an area of interest among neuroscientists. In this report, we observe that Drosophila mutants lacking Fak56 exhibit a decreased life span, accompanied by a bang-sensitive phenotype, which is characterised by sensitivity to mechanical and high-frequency electrical stimulation. Fak56 mutant animals display lower thresholds and higher rates of seizures in response to electroconvulsive stimuli, and direct measurements of action potential conduction in larval segmental nerves demonstrate a slowed propagation speed and failure during high-frequency nerve stimulation. In addition, neuromuscular junctions in Fak56 mutant animals display transmission blockade during high-frequency activity as a result of action potential failure. Endogenous Fak56 protein is abundant in glial cells ensheathing the axon bundles, and structural alterations of segmental nerve bundles can be observed in mutants. Manipulation of Fak56 function specifically in glial cells also disrupts action potential conduction and neurotransmission, suggesting a glial component in the Fak56 bang-sensitive phenotype. Furthermore, we show that increased intracellular calcium levels result in the dephosphorylation of endogenous Fak56 protein in Drosophila cell lines, in parallel with our observations of highly variable synaptic potentials at a higher Ca2+ level in Fak56 mutant larvae. Together these findings suggest that modulation of Fak56 function is important for action potential propagation and Ca2+-regulated neuromuscular transmission in vivo. PMID:18540882

  18. The effect of sevoflurane on the cognitive function of rats and its association with the inhibition of synaptic transmission

    PubMed Central

    Zhang, Deng-Xin; Jiang, Shan; Yu, Li-Na; Zhang, Feng-Jiang; Zhuang, Qing; Yan, Min

    2015-01-01

    To observe the effects of different concentrations of sevoflurane on synaptotagmin 1 (Syt1) expression, synaptic long term depression (LTD), and paired pulse depression (PPD) in the rat hippocampus as well as to investigate the association between these effects and the cognitive function of rats. A total of 24 male Sprague-Dawley (SD) rats were selected and randomly divided into 3 groups: the control group (group A), which inhaled air; group B, which inhaled 0.65 minimum alveolar concentration (MAC) sevoflurane for 2 h; and group C, which inhaled 1.30 MAC sevoflurane for 2 h. The subsequent experiments were performed after one day. (1) Y maze tests were performed, and the expression of Syt1 in hippocampal tissues was detected using western blot. (2) The changes in LTD and PPD in rat hippocampal slices were examined using electrophysiological techniques. Compared to the control group, the cognitive function was decreased and Syt1 expression in the hippocampus was significantly decreased in rats in the 1.30 MAC sevoflurane inhalation group. After 60 min of low frequency stimulation, the amplitudes of population spike (PS) potentials in rat hippocampal slices were significantly decreased. After induction of PPD, the P2/P1 ratio was significantly increased. No indicators in the 0.65 MAC sevoflurane inhalation group showed any significant changes. Inhalation of high concentrations of sevoflurane significantly reduced Syt1 protein levels in the rat hippocampus, significantly inhibited the release of presynaptic neurotransmitters, and reduced the efficiency of synaptic transmission, thus causing memory impairment. PMID:26885010

  19. Isoflurane-sensitive presynaptic R-type calcium channels contribute to inhibitory synaptic transmission in the rat thalamus

    PubMed Central

    Joksovic, Pavle M.; Weiergräber, Marco; Lee, WooYong; Struck, Henrik; Schneider, Toni; Todorovic, Slobodan M.

    2009-01-01

    Since inhibitory synaptic transmission is a major mechanism of general anesthesia, we examined the effects of isoflurane on properties of GABAergic inhibitory currents in the reticular thalamic nucleus (nRT) in brain slices. The evoked inhibitory postsynaptic currents (eIPSCs) and spontaneous miniature synaptic currents (mIPSCs) of visualized nRT cells in young and adult rats were recorded. Consistent with postsynaptic effects on GABAA receptors, isoflurane prolonged the decay-time constants of both eIPSCs and mIPCSs. Surprisingly, isoflurane completely inhibited the amplitude of eIPSCs at clinically relevant concentrations (IC50 of 240 ± 20 μM), increased the paired-pulse ratio, and decreased the frequency of mIPSCs, indicating that presynaptic mechanisms may also contribute to the effects of isoflurane on IPSCs. The overall effect of isoflurane on eIPSCs in nRT cells was a decrease of net charge-transfer across the postsynaptic membrane. The application of 100 μM nickel (Ni2+) and the more specific R-type Ca2+ channel blocker SNX-482 (0.5 μM) decreased eIPSC amplitudes, increased the paired-pulse ratio, and attenuated isoflurane-induced inhibition of eIPSCs. In addition, isoflurane potently blocked currents in recombinant human CaV2.3 (α1E) channels with an IC50 of 206 ± 22 μM. Importantly, in vivo electroencephalographic (EEG) recordings in adult CaV2.3 knockout mice demonstrated alterations in isoflurane-induced burst-suppression activity. Because the thalamus has a key function in processing sensory information, sleep, and cognition, modulation of its GABAergic tone by presynaptic R-type Ca2+ channels may contribute to the clinical effects of general anesthesia. PMID:19193890

  20. Mechanism underlying unaltered cortical inhibitory synaptic transmission in contrast with enhanced excitatory transmission in CaV2.1 knockin migraine mice.

    PubMed

    Vecchia, Dania; Tottene, Angelita; van den Maagdenberg, Arn M J M; Pietrobon, Daniela

    2014-09-01

    Familial hemiplegic migraine type 1 (FHM1), a monogenic subtype of migraine with aura, is caused by gain-of-function mutations in CaV2.1 (P/Q-type) calcium channels. In FHM1 knockin mice, excitatory neurotransmission at cortical pyramidal cell synapses is enhanced, but inhibitory neurotransmission at connected pairs of fast-spiking (FS) interneurons and pyramidal cells is unaltered, despite being initiated by CaV2.1 channels. The mechanism underlying the unaltered GABA release at cortical FS interneuron synapses remains unknown. Here, we show that the FHM1 R192Q mutation does not affect inhibitory transmission at autapses of cortical FS and other types of multipolar interneurons in microculture from R192Q knockin mice, and investigate the underlying mechanism. Lowering the extracellular [Ca(2+)] did not reveal gain-of-function of evoked transmission neither in control nor after prolongation of the action potential (AP) with tetraethylammonium, indicating unaltered AP-evoked presynaptic calcium influx at inhibitory autapses in FHM1 KI mice. Neither saturation of the presynaptic calcium sensor nor short duration of the AP can explain the unaltered inhibitory transmission in the mutant mice. Recordings of the P/Q-type calcium current in multipolar interneurons in microculture revealed that the current density and the gating properties of the CaV2.1 channels expressed in these interneurons are barely affected by the FHM1 mutation, in contrast with the enhanced current density and left-shifted activation gating of mutant CaV2.1 channels in cortical pyramidal cells. Our findings suggest that expression of specific CaV2.1 channels differentially sensitive to modulation by FHM1 mutations in inhibitory and excitatory cortical neurons underlies the gain-of-function of excitatory but unaltered inhibitory synaptic transmission and the likely consequent dysregulation of the cortical excitatory-inhibitory balance in FHM1. PMID:24907493

  1. In vivo synaptic transmission and morphology in mouse models of Tuberous sclerosis, Fragile X syndrome, Neurofibromatosis type 1, and Costello syndrome.

    PubMed

    Wang, Tiantian; de Kok, Laura; Willemsen, Rob; Elgersma, Ype; Borst, J Gerard G

    2015-01-01

    Defects in the rat sarcoma viral oncogene homolog (Ras)/extracellular-signal-regulated kinase and the phosphatidylinositol 3-kinase-mammalian target of rapamycin (mTOR) signaling pathways are responsible for several neurodevelopmental disorders. These disorders are an important cause for intellectual disability; additional manifestations include autism spectrum disorder, seizures, and brain malformations. Changes in synaptic function are thought to underlie the neurological conditions associated with these syndromes. We therefore studied morphology and in vivo synaptic transmission of the calyx of Held synapse, a relay synapse in the medial nucleus of the trapezoid body (MNTB) of the auditory brainstem, in mouse models of tuberous sclerosis complex (TSC), Fragile X syndrome (FXS), Neurofibromatosis type 1 (NF1), and Costello syndrome. Calyces from both Tsc1(+/-) and from Fmr1 knock-out (KO) mice showed increased volume and surface area compared to wild-type (WT) controls. In addition, in Fmr1 KO animals a larger fraction of calyces showed complex morphology. In MNTB principal neurons of Nf1 (+/) (-) mice the average delay between EPSPs and APs was slightly smaller compared to WT controls, which could indicate an increased excitability. Otherwise, no obvious changes in synaptic transmission, or short-term plasticity were observed during juxtacellular recordings in any of the four lines. Our results in these four mutants thus indicate that abnormalities of mTOR or Ras signaling do not necessarily result in changes in in vivo synaptic transmission. PMID:26190969

  2. In vivo synaptic transmission and morphology in mouse models of Tuberous sclerosis, Fragile X syndrome, Neurofibromatosis type 1, and Costello syndrome

    PubMed Central

    Wang, Tiantian; de Kok, Laura; Willemsen, Rob; Elgersma, Ype; Borst, J. Gerard G.

    2015-01-01

    Defects in the rat sarcoma viral oncogene homolog (Ras)/extracellular-signal-regulated kinase and the phosphatidylinositol 3-kinase-mammalian target of rapamycin (mTOR) signaling pathways are responsible for several neurodevelopmental disorders. These disorders are an important cause for intellectual disability; additional manifestations include autism spectrum disorder, seizures, and brain malformations. Changes in synaptic function are thought to underlie the neurological conditions associated with these syndromes. We therefore studied morphology and in vivo synaptic transmission of the calyx of Held synapse, a relay synapse in the medial nucleus of the trapezoid body (MNTB) of the auditory brainstem, in mouse models of tuberous sclerosis complex (TSC), Fragile X syndrome (FXS), Neurofibromatosis type 1 (NF1), and Costello syndrome. Calyces from both Tsc1+/- and from Fmr1 knock-out (KO) mice showed increased volume and surface area compared to wild-type (WT) controls. In addition, in Fmr1 KO animals a larger fraction of calyces showed complex morphology. In MNTB principal neurons of Nf1+/- mice the average delay between EPSPs and APs was slightly smaller compared to WT controls, which could indicate an increased excitability. Otherwise, no obvious changes in synaptic transmission, or short-term plasticity were observed during juxtacellular recordings in any of the four lines. Our results in these four mutants thus indicate that abnormalities of mTOR or Ras signaling do not necessarily result in changes in in vivo synaptic transmission. PMID:26190969

  3. External QX-314 inhibits evoked cranial primary afferent synaptic transmission independent of TRPV1.

    PubMed

    Hofmann, Mackenzie E; Largent-Milnes, Tally M; Fawley, Jessica A; Andresen, Michael C

    2014-12-01

    The cell-impermeant lidocaine derivative QX-314 blocks sodium channels via intracellular mechanisms. In somatosensory nociceptive neurons, open transient receptor potential vanilloid type 1 (TRPV1) receptors provide a transmembrane passageway for QX-314 to produce long-lasting analgesia. Many cranial primary afferents express TRPV1 at synapses on neurons in the nucleus of the solitary tract and caudal trigeminal nucleus (Vc). Here, we investigated whether QX-314 interrupts neurotransmission from primary afferents in rat brain-stem slices. Shocks to the solitary tract (ST) activated highly synchronous evoked excitatory postsynaptic currents (ST-EPSCs). Application of 300 μM QX-314 increased the ST-EPSC latency from TRPV1+ ST afferents, but, surprisingly, it had similar actions at TRPV1- ST afferents. Continued exposure to QX-314 blocked evoked ST-EPSCs at both afferent types. Neither the time to onset of latency changes nor the time to ST-EPSC failure differed between responses for TRPV1+ and TRPV1- inputs. Likewise, the TRPV1 antagonist capsazepine failed to prevent the actions of QX-314. Whereas QX-314 blocked ST-evoked release, the frequency and amplitude of spontaneous EPSCs remained unaltered. In neurons exposed to QX-314, intracellular current injection evoked action potentials suggesting a presynaptic site of action. QX-314 acted similarly at Vc neurons to increase latency and block EPSCs evoked from trigeminal tract afferents. Our results demonstrate that QX-314 blocked nerve conduction in cranial primary afferents without interrupting the glutamate release mechanism or generation of postsynaptic action potentials. The TRPV1 independence suggests that QX-314 either acted extracellularly or more likely entered these axons through an undetermined pathway common to all cranial primary afferents. PMID:25185814

  4. External QX-314 inhibits evoked cranial primary afferent synaptic transmission independent of TRPV1

    PubMed Central

    Largent-Milnes, Tally M.; Fawley, Jessica A.; Andresen, Michael C.

    2014-01-01

    The cell-impermeant lidocaine derivative QX-314 blocks sodium channels via intracellular mechanisms. In somatosensory nociceptive neurons, open transient receptor potential vanilloid type 1 (TRPV1) receptors provide a transmembrane passageway for QX-314 to produce long-lasting analgesia. Many cranial primary afferents express TRPV1 at synapses on neurons in the nucleus of the solitary tract and caudal trigeminal nucleus (Vc). Here, we investigated whether QX-314 interrupts neurotransmission from primary afferents in rat brain-stem slices. Shocks to the solitary tract (ST) activated highly synchronous evoked excitatory postsynaptic currents (ST-EPSCs). Application of 300 μM QX-314 increased the ST-EPSC latency from TRPV1+ ST afferents, but, surprisingly, it had similar actions at TRPV1− ST afferents. Continued exposure to QX-314 blocked evoked ST-EPSCs at both afferent types. Neither the time to onset of latency changes nor the time to ST-EPSC failure differed between responses for TRPV1+ and TRPV1− inputs. Likewise, the TRPV1 antagonist capsazepine failed to prevent the actions of QX-314. Whereas QX-314 blocked ST-evoked release, the frequency and amplitude of spontaneous EPSCs remained unaltered. In neurons exposed to QX-314, intracellular current injection evoked action potentials suggesting a presynaptic site of action. QX-314 acted similarly at Vc neurons to increase latency and block EPSCs evoked from trigeminal tract afferents. Our results demonstrate that QX-314 blocked nerve conduction in cranial primary afferents without interrupting the glutamate release mechanism or generation of postsynaptic action potentials. The TRPV1 independence suggests that QX-314 either acted extracellularly or more likely entered these axons through an undetermined pathway common to all cranial primary afferents. PMID:25185814

  5. Dissociation of μ- and δ-opioid inhibition of glutamatergic synaptic transmission in superficial dorsal horn

    PubMed Central

    2010-01-01

    Background There is anatomical and behavioural evidence that μ- and δ-opioid receptors modulate distinct nociceptive modalities within the superficial dorsal horn. The aim of the present study was to examine whether μ- and δ-opioid receptor activation differentially modulates TRP sensitive inputs to neurons within the superficial dorsal horn. To do this, whole cell patch clamp recordings were made from lamina I - II neurons in rat spinal cord slices in vitro to examine the effect of opioids on TRP agonist-enhanced glutamatergic spontaneous miniature excitatory postsynaptic currents (EPSCs). Results Under basal conditions the μ-opioid agonist DAMGO (3 μM) reduced the rate of miniature EPSCs in 68% of neurons, while the δ- and κ-opioid agonists deltorphin-II (300 nM) and U69593 (300 nM) did so in 13 - 17% of neurons tested. The TRP agonists menthol (400 μM) and icilin (100 μM) both produced a Ca2+-dependent increase in miniature EPSC rate which was unaffected by the voltage dependent calcium channel (VDCC) blocker Cd2+. The proportion of neurons in which deltorphin-II reduced the miniature EPSC rate was enhanced in the presence of icilin (83%), but not menthol (0%). By contrast, the proportion of DAMGO and U69593 responders was unaltered in the presence of menthol (57%, 0%), or icilin (57%, 17%). Conclusions These findings demonstrate that δ-opioid receptor activation selectively inhibits inputs activated by icilin, whereas μ-opioid receptor activation has a more widespread effect on synaptic inputs to neurons in the superficial dorsal horn. These findings suggest that δ-opioids may provide a novel analgesic approach for specific, TRPA1-like mediated pain modalities. PMID:20977770

  6. Biphasic modulation of synaptic transmission by hypertonicity at the embryonic Drosophila neuromuscular junction

    PubMed Central

    Suzuki, Kazuhiro; Okamoto, Tomonori; Kidokoro, Yoshiaki

    2002-01-01

    Puff-application of hypertonic saline (sucrose added to external saline) causes a transient increase in the frequency of spontaneous miniature synaptic currents (mSCs) at the neuromuscular junctions of Drosophila embryos. The frequency gradually returns to pre-application levels. External Ca2+ is not needed for this response, but it may modify it. At 50 mm added sucrose, for example, enhanced spontaneous release was observed only in the presence of external Ca2+, suggesting that Ca2+ augments the response. In a high-K+ solution, in which the basal mSC frequency was elevated, higher sucrose concentrations produced an increase in mSC frequency that was followed (during and after the hypertonic exposure) by depression, with the magnitude of both effects increasing with hypertonicity between 100 and 500 mm. Evoked release by nerve stimulation showed only depression in response to hypertonicity. We do not believe that the depression of spontaneous or evoked release can be explained by the depletion of releasable quanta, however, since the frequency of quantal release did not reach levels compatible with this explanation and the enhancement and depression could be obtained independent of one another. In a mutant lacking neuronal synaptobrevin, only the depression of mSC frequency was induced by hypertonicity. Conversely, only the enhancing effect was observed in wild-type embryos when the mSC frequency was elevated with forskolin in Ca2+-free saline. In cultured embryonic Drosophila neurons, Ca2+ signals that were induced by high K+ and detected by Fura-2, were reduced by hypertonicity, suggesting that the depressing response is due to a direct effect of hypertonicity on Ca2+ influx. PMID:12433954

  7. μ-Opioid Receptor-Mediated Inhibition of Intercalated Neurons and Effect on Synaptic Transmission to the Central Amygdala.

    PubMed

    Blaesse, Peter; Goedecke, Lena; Bazelot, Michaël; Capogna, Marco; Pape, Hans-Christian; Jüngling, Kay

    2015-05-13

    The amygdala is a key region for the processing of information underlying fear, anxiety, and fear extinction. Within the local neuronal networks of the amygdala, a population of inhibitory, intercalated neurons (ITCs) modulates the flow of information among various nuclei of amygdala, including the basal nucleus (BA) and the centromedial nucleus (CeM) of the amygdala. These ITCs have been shown to be important during fear extinction and are target of a variety of neurotransmitters and neuropeptides. Here we provide evidence that the activation of μ-opioid receptors (MORs) by the specific agonist DAMGO ([D-Ala2,N-Me-Phe4,Gly5-ol]-Enkephalin) hyperpolarizes medially located ITCs (mITCs) in acute brain slices of mice. Moreover, we use whole-cell patch-clamp recordings in combination with local electrical stimulation or glutamate uncaging to analyze the effect of MOR activation on local microcircuits. We show that the GABAergic transmission between mITCs and CeM neurons is attenuated by DAMGO, whereas the glutamatergic transmission on CeM neurons and mITCs is unaffected. Furthermore, MOR activation induced by theta burst stimulation in BA suppresses plastic changes of feedforward inhibitory transmission onto CeM neurons as revealed by the MOR antagonist CTAP d-Phe-Cys-Tyr-d-Trp-Arg-Thr-Pen-Thr-NH2. In summary, the mITCs constitute a target for the opioid system, and therefore, the activation of MOR in ITCs might play a central role in the modulation of the information processing between the basolateral complex of the amygdala and central nuclei of the amygdala. PMID:25972162

  8. Molecular pharmacology of glutamate transporters, EAATs and VGLUTs.

    PubMed

    Shigeri, Yasushi; Seal, Rebecca P; Shimamoto, Keiko

    2004-07-01

    L-Glutamate serves as a major excitatory neurotransmitter in the mammalian central nervous system (CNS) and is stored in synaptic vesicles by an uptake system that is dependent on the proton electrochemical gradient (VGLUTs). Following its exocytotic release, glutamate activates fast-acting, excitatory ionotropic receptors and slower-acting metabotropic receptors to mediate neurotransmission. Na+-dependent glutamate transporters (EAATs) located on the plasma membrane of neurons and glial cells rapidly terminate the action of glutamate and maintain its extracellular concentration below excitotoxic levels. Thus far, five Na+-dependent glutamate transporters (EAATs 1-5) and three vesicular glutamate transporters (VGLUTs 1-3) have been identified. Examination of EAATs and VGLUTs in brain preparations and by heterologous expression of the various cloned subtypes shows these two transporter families differ in many of their functional properties including substrate specificity and ion requirements. Alterations in the function and/or expression of these carriers have been implicated in a range of psychiatric and neurological disorders. EAATs have been implicated in cerebral stroke, epilepsy, Alzheimer's disease, HIV-associated dementia, Huntington's disease, amyotrophic lateral sclerosis (ALS) and malignant glioma, while VGLUTs have been implicated in schizophrenia. To examine the physiological role of glutamate transporters in more detail, several classes of transportable and non-transportable inhibitors have been developed, many of which are derivatives of the natural amino acids, aspartate and glutamate. This review summarizes the development of these indispensable pharmacological tools, which have been critical to our understanding of normal and abnormal synaptic transmission. PMID:15210307

  9. MAGUKs, Synaptic Development, and Synaptic Plasticity

    PubMed Central

    Zheng, Chan-Ying; Seabold, Gail K.; Horak, Martin; Petralia, Ronald S.

    2011-01-01

    MAGUKs are proteins that act as key scaffolds in surface complexes containing receptors, adhesion proteins, and various signaling molecules. These complexes evolved prior to the appearance of multicellular animals and play key roles in cell-cell intercommunication. A major example of this is the neuronal synapse, which contains several presynaptic and postsynaptic MAGUKs including PSD-95, SAP102, SAP97, PSD-93, CASK, and MAGIs. Here, they play roles in both synaptic development and in later synaptic plasticity events. During development, MAGUKs help to organize the postsynaptic density via associations with other scaffolding proteins, such as Shank, and the actin cytoskeleton. They affect the clustering of glutamate receptors and other receptors, and these associations change with development. MAGUKs are involved in long-term potentiation and depression (e.g., via their phosphorylation by kinases and phosphorylation of other proteins associated with MAGUKs). Importantly, synapse development and function are dependent on the kind of MAGUK present. For example, SAP102 shows high mobility and is present in early synaptic development. Later, much of SAP102 is replaced by PSD-95, a more stable synaptic MAGUK; this is associated with changes in glutamate receptor types that are characteristic of synaptic maturation. PMID:21498811

  10. Functional Characterization of a Vesicular Glutamate Transporter in an Interneuron That Makes Excitatory and Inhibitory Synaptic Connections in a Molluscan Neural Circuit

    PubMed Central

    Alexeeva, Vera; Chen, Song-an; Yu, Ke; Due, Michael R.; Tan, Li-nuo; Chen, Ting-ting; Liu, Dan-dan; Cropper, Elizabeth C.; Vilim, Ferdinand S.; Weiss, Klaudiusz R.

    2015-01-01

    Understanding circuit function requires the characterization of component neurons and their neurotransmitters. Previous work on radula protraction in the Aplysia feeding circuit demonstrated that critical neurons initiate feeding via cholinergic excitation. In contrast, it is less clear how retraction is mediated at the interneuronal level. In particular, glutamate involvement was suggested, but was not directly confirmed. Here we study a suspected glutamatergic retraction interneuron, B64. We used the representational difference analysis (RDA) method to successfully clone an Aplysia vesicular glutamate transporter (ApVGLUT) from B64 and from a glutamatergic motor neuron B38. Previously, RDA was used to characterize novel neuropeptides. Here we demonstrate its utility for characterizing other types of molecules. Bioinformatics suggests that ApVGLUT is more closely related to mammalian VGLUTs than to Drosophila and Caenorhabditis elegans VGLUTs. We expressed ApVGLUT in a cell line, and demonstrated that it indeed transports glutamate in an ATP and proton gradient-dependent manner. We mapped the ApVGLUT distribution in the CNS using in situ hybridization and immunocytochemistry. Further, we demonstrated that B64 is ApVGLUT positive, supporting the idea that it is glutamatergic. Although glutamate is primarily an excitatory transmitter in the mammalian CNS, B64 elicits inhibitory PSPs in protraction neurons to terminate protraction and excitatory PSPs in retraction neurons to maintain retraction. Pharmacological data indicated that both types of PSPs are mediated by glutamate. Thus, glutamate mediates the dual function of B64 in Aplysia. More generally, our systematic approaches based on RDA may facilitate analyses of transmitter actions in small circuits with identifiable neurons. PMID:26085636

  11. Carbamazepine and oxcarbazepine, but not eslicarbazepine, enhance excitatory synaptic transmission onto hippocampal CA1 pyramidal cells through an antagonist action at adenosine A1 receptors.

    PubMed

    Booker, Sam A; Pires, Nuno; Cobb, Stuart; Soares-da-Silva, Patrício; Vida, Imre

    2015-06-01

    This study assessed the anticonvulsant and seizure generation effects of carbamazepine (CBZ), oxcarbazepine (OXC) and eslicarbazepine (S-Lic) in wild-type mice. Electrophysiological recordings were made to discriminate potential cellular and synaptic mechanisms underlying anti- and pro-epileptic actions. The anticonvulsant and pro-convulsant effects were evaluated in the MES, the 6-Hz and the Irwin tests. Whole-cell patch-clamp recordings were used to investigate the effects on fast excitatory and inhibitory synaptic transmission in hippocampal area CA1. The safety window for CBZ, OXC and eslicarbazepine (ED50 value against the MES test and the dose that produces grade 5 convulsions in all mice), was 6.3, 6.0 and 12.5, respectively. At high concentrations the three drugs reduced synaptic transmission. CBZ and OXC enhanced excitatory postsynaptic currents (EPSCs) at low, therapeutically-relevant concentrations. These effects were associated with no change in inhibitory postsynaptic currents (IPSCs) resulting in altered balance between excitation and inhibition. S-Lic had no effect on EPSC or IPSC amplitudes over the same concentration range. The CBZ mediated enhancement of EPSCs was blocked by DPCPX, a selective antagonist, and occluded by CCPA, a selective agonist of the adenosine A1 receptor. Furthermore, reduction of endogenous adenosine by application of the enzyme adenosine deaminase also abolished the CBZ- and OXC-induced increase of EPSCs, indicating that the two drugs act as antagonists at native adenosine receptors. In conclusion, CBZ and OXC possess pro-epileptic actions at clinically-relevant concentrations through the enhancement of excitatory synaptic transmission. S-Lic by comparison has no such effect on synaptic transmission, explaining its lack of seizure exacerbation. PMID:25656478

  12. Melamine Alters Glutamatergic Synaptic Transmission of CA3-CA1 Synapses Presynaptically Through Autophagy Activation in the Rat Hippocampus.

    PubMed

    Zhang, Hui; Wang, Hui; Xiao, Xi; Zhang, Tao

    2016-01-01

    Melamine is an industrial chemical that can cause central nervous system disorders including excitotoxicity and cognitive impairment. Its illegal use in powdered baby formula was the focus of a milk scandal in China in 2008. One of our previous studies showed that melamine impaired glutamatergic transmission in rat hippocampal CA1 pyramidal cells. However, the underlying mechanism of action of melamine is unclear, and it is unknown if the CA3-CA1 pathway is directly involved. In the present study, a whole-cell patch-clamp technique was employed to investigate the effect of melamine on the hippocampal CA3-CA1 pathway in vitro. Both the evoked excitatory postsynaptic current (eEPSC) and the paired-pulse ratio (PPR) were recorded. Furthermore, we examined whether autophagy was involved in glutamatergic transmission alterations induced by melamine. Our data showed that melamine significantly increased the amplitude of eEPSCs in a dose-dependent manner. Inhibition of the N-methyl-D-aspartic acid receptor did not prevent the increase in eEPSC amplitude. In addition, the PPR was remarkably decreased by a melamine concentration of 5 × 10(-5) g/mL. It was found that autophagy could be activated by melamine and an autophagy inhibitor, 3-MA, prevented the melamine-induced increase in eEPSC amplitude. Overall, our results show that melamine presynaptically alters glutamatergic synaptic transmission of hippocampal CA3-CA1 synapses in vitro and this is likely associated with autophagy alteration. PMID:26530910

  13. Conditioned taste aversion prevents the long-lasting BDNF-induced enhancement of synaptic transmission in the insular cortex: A metaplastic effect.

    PubMed

    Rivera-Olvera, Alejandro; Rodríguez-Durán, Luis F; Escobar, Martha L

    2016-04-01

    Homeostatic plasticity mechanisms dynamically adjust synaptic strengths to promote stability that is crucial for memory storage. Metaplasticity is an example of these forms of plasticity that modify the capacity of synapses to experience subsequent Hebbian modifications. In particular, training in several behavioral tasks modifies the ability to induce long-term potentiation (LTP). Recently, we have reported that prior training in conditioned taste aversion (CTA) prevents the subsequent induction of LTP generated by high frequency stimulation in the projection from the basolateral nucleus of the amygdala (Bla) to the insular cortex (IC). One of the key molecular players that underlie long-term synaptic plasticity is brain-derived neurotrophic factor (BDNF). Previous studies from our group reported that acute microinfusion of BDNF in the IC induces a lasting potentiation of synaptic efficacy at the Bla-IC projection. Thus, the aim of the present study was to analyze whether CTA training modifies the ability to induce subsequent BDNF-induced potentiation of synaptic transmission in the Bla-IC projection in vivo. Accordingly, CTA trained rats received intracortical microinfusion of BDNF in order to induce lasting potentiation 48h after the aversion test. Our results show that CTA training prevents the induction of in vivo BDNF-LTP in the Bla-IC projection. The present results provide evidence that CTA modulates BDNF-dependent changes in IC synaptic strength. PMID:26854904

  14. Impaired Synaptic Development, Maintenance, and Neuromuscular Transmission in LRP4 Myasthenia

    PubMed Central

    Selcen, Duygu; Ohkawara, Bisei; Shen, Xin-Ming; McEvoy, Kathleen; Ohno, Kinji; Engel, Andrew G.

    2015-01-01

    IMPORTANCE Congenital myasthenic syndromes (CMS) are heterogeneous disorders. Defining the phenotypic features, genetic basis, and pathomechanisms of a CMS is relevant to prognosis, genetic counseling, and therapy. OBJECTIVE To characterize clinical, structural, electrophysiologic, and genetic features of a CMS and search for optimal therapy. DESIGN, SETTINGS, AND PARTICIPANTS Two sisters, 34 and 20 years of age suffering from a CMS affecting the limb-girdle muscles were investigated at an academic medical center by clinical observation, in vitro analysis of neuromuscular transmission, cytochemical and electron microscopy studies of the neuromuscular junction, exome sequencing, expression studies in HEK293 and COS-7 cells, and for response to therapy. MAIN OUTCOMES AND MEASURES We identified the disease gene and mutation, confirmed pathogenicity of the mutation by expression studies, and instituted optimal pharmacotherapy. RESULTS Intercostal muscle endplates (EPs) were abnormally small with attenuated reactivities for the acetylcholine receptor and acetylcholine esterase. Most EPs had poorly differentiated or degenerate junctional folds and some appeared denuded of nerve terminals. The amplitude of the EP potential (EPP), the miniature EPP, and the quantal content of the EPP were all markedly reduced. Exome sequencing identified a novel homozygous p.Glu1233Ala mutation in LRP4, a coreceptor for agrin to activate MuSK, required for EP development and maintenance. Expression studies indicate the mutation compromises ability of LRP4 to bind to, phosphorylate, and activate MuSK. Albuterol improved the patients’ symptoms. CONCLUSIONS AND RELEVANCE We identify a second CMS kinship harboring mutations in LRP4, identify the mechanisms that impair neuromuscular transmission, and mitigate the disease by appropriate therapy. PMID:26052878

  15. Signaling mechanism underlying α2A -adrenergic suppression of excitatory synaptic transmission in the medial prefrontal cortex of rats.

    PubMed

    Yi, Feng; Liu, Shu-Su; Luo, Fei; Zhang, Xue-Han; Li, Bao-Ming

    2013-08-01

    Stimulation of α2A -adrenoceptors (ARs) in the prefrontal cortex (PFC) produces a beneficial effect on cognitive functions such as working memory. A previous study in our laboratory showed that α2A -AR stimulation suppresses excitatory synaptic transmission in layer V-VI pyramidal cells of the rat medial PFC (mPFC). However, the intracellular mechanism underlying the α2A -AR suppression remains unclear. In the present study, we recorded evoked excitatory postsynaptic current (eEPSC) in layer V-VI pyramidal cells of the mPFC, using whole-cell patch-clamp recording. We found that the α2A -AR agonist guanfacine significantly suppresses eEPSC in mPFC pyramidal cells. The α2A -AR inhibition is mediated by the Gi-cAMP-PKA-PP1-CaMKII-AMPAR signaling pathway, as such inhibition no longer exists when each step of this pathway is blocked with NF023, Rp-cAMP, PKI5-24 or H89, tautomycin, and KN-62 or KN-93, respectively. PMID:23701442

  16. Prenatal Stress Enhances Excitatory Synaptic Transmission and Impairs Long-Term Potentiation in the Frontal Cortex of Adult Offspring Rats

    PubMed Central

    Sowa, Joanna; Bobula, Bartosz; Glombik, Katarzyna; Slusarczyk, Joanna; Basta-Kaim, Agnieszka; Hess, Grzegorz

    2015-01-01

    The effects of prenatal stress procedure were investigated in 3 months old male rats. Prenatally stressed rats showed depressive-like behavior in the forced swim test, including increased immobility, decreased mobility and decreased climbing. In ex vivo frontal cortex slices originating from prenatally stressed animals, the amplitude of extracellular field potentials (FPs) recorded in cortical layer II/III was larger, and the mean amplitude ratio of pharmacologically-isolated NMDA to the AMPA/kainate component of the field potential—smaller than in control preparations. Prenatal stress also resulted in a reduced magnitude of long-term potentiation (LTP). These effects were accompanied by an increase in the mean frequency, but not the mean amplitude, of spontaneous excitatory postsynaptic currents (sEPSCs) in layer II/III pyramidal neurons. These data demonstrate that stress during pregnancy may lead not only to behavioral disturbances, but also impairs the glutamatergic transmission and long-term synaptic plasticity in the frontal cortex of the adult offspring. PMID:25749097

  17. Altered neuronal intrinsic properties and reduced synaptic transmission of the rat's medial geniculate body in salicylate-induced tinnitus.

    PubMed

    Su, Yan-Yan; Luo, Bin; Jin, Yan; Wu, Shu-Hui; Lobarinas, Edward; Salvi, Richard J; Chen, Lin

    2012-01-01

    Sodium salicylate (NaSal), an aspirin metabolite, can cause tinnitus in animals and human subjects. To explore neural mechanisms underlying salicylate-induced tinnitus, we examined effects of NaSal on neural activities of the medial geniculate body (MGB), an auditory thalamic nucleus that provides the primary and immediate inputs to the auditory cortex, by using the whole-cell patch-clamp recording technique in MGB slices. Rats treated with NaSal (350 mg/kg) showed tinnitus-like behavior as revealed by the gap prepulse inhibition of acoustic startle (GPIAS) paradigm. NaSal (1.4 mM) decreased the membrane input resistance, hyperpolarized the resting membrane potential, suppressed current-evoked firing, changed the action potential, and depressed rebound depolarization in MGB neurons. NaSal also reduced the excitatory and inhibitory postsynaptic response in the MGB evoked by stimulating the brachium of the inferior colliculus. Our results demonstrate that NaSal alters neuronal intrinsic properties and reduces the synaptic transmission of the MGB, which may cause abnormal thalamic outputs to the auditory cortex and contribute to NaSal-induced tinnitus. PMID:23071681

  18. Group III metabotropic glutamate receptors inhibit startle-mediating giant neurons in the caudal pontine reticular nucleus but do not mediate synaptic depression/short-term habituation of startle.

    PubMed

    Schmid, Susanne; Brown, Tyler; Simons-Weidenmaier, Nadine; Weber, Maruschka; Fendt, Markus

    2010-08-01

    Short-term habituation is a basic form of learning that is analyzed in different species and using different behavioral models. Previous studies on mechanisms of short-term habituation yielded evidence for a potential role of group III metabotropic glutamate receptors (mGluRIIIs). Here we tested the hypothesis that mGluRIII mediate short-term habituation of startle in rats, combining electrophysiological experiments in vitro with behavioral studies in vivo. We applied different mGluRIII agonists and antagonists on rat brainstem slices while recording from startle-mediating neurons in the caudal pontine reticular nucleus (PnC) and monitoring synaptic depression presumably underlying habituation. Furthermore, we injected the mGluRIII antagonist (RS)-alpha-phosphonophenylglycine (MPPG) and the agonist L-(+)-2-amino-4-phosphonobutyric acid (L-AP4) into the PnC of rats in vivo and measured its effect on startle habituation. Our results show that activation of mGluRIIIs in the PnC strongly inhibits startle-mediating giant neurons in vitro. Accordingly, L-AP4 reduced startle responses in vivo. However, synaptic depression in the slice was not disrupted by mGluRIII antagonists or agonists. Correspondingly, the in vivo application of the mGluRIII antagonist MPPG failed to show any effect on short-term habituation of startle responses. We therefore conclude that mGluRs are expressed within the primary startle pathway and that they inhibit startle responses upon activation; however, this inhibition does not play any role in synaptic depression and short-term habituation of startle. This is in contrast to the role of mGluRIIIs in other forms of habituation and supports the notion that there are different mechanisms involved in habituation of sensory-evoked behaviors. PMID:20685984

  19. Glutamate uptake block triggers deadly rhythmic bursting of neonatal rat hypoglossal motoneurons

    PubMed Central

    Sharifullina, Elina; Nistri, Andrea

    2006-01-01

    In the brain the extracellular concentration of glutamate is controlled by glial transporters that restrict the neurotransmitter action to synaptic sites and avoid excitotoxicity. Impaired transport of glutamate occurs in many cases of amyotrophic lateral sclerosis, a devastating motoneuron disease. Motoneurons of the brainstem nucleus hypoglossus are among the most vulnerable, giving early symptoms like slurred speech and dysphagia. However, the direct consequences of extracellular glutamate build-up, due to uptake block, on synaptic transmission and survival of hypoglossal motoneurons remain unclear and have been studied using the neonatal rat brainstem slice preparation as a model. Patch clamp recording from hypoglossal motoneurons showed that, in about one-third of these cells, inhibition of glutamate transport with the selective blocker dl-threo-β-benzyloxyaspartate (TBOA; 50 μ m) unexpectedly led to the emergence of rhythmic bursting consisting of inward currents of long duration with superimposed fast oscillations and synaptic events. Synaptic inhibition block facilitated bursting. Bursts had a reversal potential near 0 mV, and were blocked by tetrodotoxin, the gap junction blocker carbenoxolone, or antagonists of AMPA, NMDA or mGluR1 glutamate receptors. Intracellular Ca2+ imaging showed bursts as synchronous discharges among motoneurons. Synergy of activation of distinct classes of glutamate receptor plus gap junctions were therefore essential for bursting. Ablating the lateral reticular formation preserved bursting, suggesting independence from propagated network activity within the brainstem. TBOA significantly increased the number of dead motoneurons, an effect prevented by the same agents that suppressed bursting. Bursting thus represents a novel hallmark of motoneuron dysfunction triggered by glutamate uptake block. PMID:16455692

  20. Functional and Structural Remodeling of Glutamate Synapses in Prefrontal and Frontal Cortex Induced by Behavioral Stress

    PubMed Central

    Musazzi, Laura; Treccani, Giulia; Popoli, Maurizio

    2015-01-01

    Increasing evidence has shown that the pathophysiology of neuropsychiatric disorders, including mood disorders, is associated with abnormal function and regulation of the glutamatergic system. Consistently, preclinical studies on stress-based animal models of pathology showed that glucocorticoids and stress exert crucial effects on neuronal excitability and function, especially in cortical and limbic areas. In prefrontal and frontal cortex, acute stress was shown to induce enhancement of glutamate release/transmission dependent on activation of corticosterone receptors. Although the mechanisms whereby stress affects glutamate transmission have not yet been fully understood, it was shown that synaptic, non-genomic action of corticosterone is required to increase the readily releasable pool of glutamate vesicles, but is not sufficient to enhance transmission in prefrontal and frontal cortex. Slower, partly genomic mechanisms are probably necessary for the enhancement of glutamate transmission induced by stress. Combined evidence has suggested that the changes in glutamate release and transmission are responsible for the dendritic remodeling and morphological changes induced by stress and it has been argued that sustained alterations of glutamate transmission may play a key role in the long-term structural/functional changes associated with mood disorders in patients. Intriguingly, modifications of the glutamatergic system induced by stress in the prefrontal cortex seem to be biphasic. Indeed, while the fast response to stress suggests an enhancement in the number of excitatory synapses, synaptic transmission and working memory, long-term adaptive changes – including those consequent to chronic stress – induce opposite effects. Better knowledge of the cellular effectors involved in this biphasic effect of stress may be useful to understand the pathophysiology of stress-related disorders, and open new paths for the development of therapeutic approaches. PMID

  1. σ2-Adaptin Facilitates Basal Synaptic Transmission and Is Required for Regenerating Endo-Exo Cycling Pool Under High-Frequency Nerve Stimulation in Drosophila.

    PubMed

    Choudhury, Saumitra Dey; Mushtaq, Zeeshan; Reddy-Alla, Suneel; Balakrishnan, Sruthi S; Thakur, Rajan S; Krishnan, Kozhalmannom S; Raghu, Padinjat; Ramaswami, Mani; Kumar, Vimlesh

    2016-05-01

    The functional requirement of adapter protein 2 (AP2) complex in synaptic membrane retrieval by clathrin-mediated endocytosis is not fully understood. Here we isolated and functionally characterized a mutation that dramatically altered synaptic development. Based on the aberrant neuromuscular junction (NMJ) synapse, we named this mutation angur (a Hindi word meaning "grapes"). Loss-of-function alleles of angur show more than twofold overgrowth in bouton numbers and a dramatic decrease in bouton size. We mapped the angur mutation to σ2-adaptin, the smallest subunit of the AP2 complex. Reducing the neuronal level of any of the subunits of the AP2 complex or disrupting AP2 complex assembly in neurons phenocopied the σ2-adaptin mutation. Genetic perturbation of σ2-adaptin in neurons leads to a reversible temperature-sensitive paralysis at 38°. Electrophysiological analysis of the mutants revealed reduced evoked junction potentials and quantal content. Interestingly, high-frequency nerve stimulation caused prolonged synaptic fatigue at the NMJs. The synaptic levels of subunits of the AP2 complex and clathrin, but not other endocytic proteins, were reduced in the mutants. Moreover, bone morphogenetic protein (BMP)/transforming growth factor β (TGFβ) signaling was altered in these mutants and was restored by normalizing σ2-adaptin in neurons. Thus, our data suggest that (1) while σ2-adaptin facilitates synaptic vesicle (SV) recycling for basal synaptic transmission, its activity is also required for regenerating SVs during high-frequency nerve stimulation, and (2) σ2-adaptin regulates NMJ morphology by attenuating TGFβ signaling. PMID:26920756

  2. Synapse-associated protein-97 isoform-specific regulation of surface AMPA receptors and synaptic function in cultured neurons.

    PubMed

    Rumbaugh, Gavin; Sia, Gek-Ming; Garner, Craig C; Huganir, Richard L

    2003-06-01

    Members of the synapse-associated protein-97 (SAP97) family of scaffold proteins have been implicated as central organizers of synaptic junctions to build macromolecular signaling complexes around specific postsynaptic neurotransmitter receptors. In this regard, SAP97 has been suggested to regulate the synaptic localization of glutamate receptor type 1 subunits of the AMPA-type glutamate receptors. To test this hypothesis directly, we assessed the effects of SAP97 overexpression on surface expression of synaptic AMPA receptors. We find that recombinant SAP97 not only becomes concentrated at synaptic junctions but also leads to an increase in synaptic AMPA receptors, spine enlargement, and an increase in miniature EPSC (mEPSC) frequency, indicating that SAP97 has both postsynaptic and presynaptic effects on synaptic transmission. Synaptic targeting of SAP97, increased surface AMPA receptors, and increased mEPSC frequency are dependent on the presence of specific alternatively spliced sequences in SAP97 that encode a protein 4.1 binding site. These results suggest that SAP97 can affect the synaptic recruitment of AMPA receptors and spine morphology and that these effects may be regulated by alternative splicing. PMID:12805297

  3. NMDA and non-NMDA glutamate receptors in auditory transmission in the barn owl inferior colliculus.

    PubMed

    Feldman, D E; Knudsen, E I

    1994-10-01

    subdivisions, and mediate the bulk of auditory transmission in the lateral shell. The time course of the NMDA receptor contribution to ICx auditory responses and the dependence of this contribution on stimulus level were both examined in detail. AP5 preferentially blocked spikes late in ICx auditory responses, while CNQX blocked spikes equally throughout the responses. This pattern is consistent with a simple model in which slow NMDA receptor currents and faster non-NMDA receptor currents are both activated by auditory inputs to ICx neurons. PMID:7931555

  4. Glutamate Receptor Ion Channels: Structure, Regulation, and Function

    PubMed Central

    Wollmuth, Lonnie P.; McBain, Chris J.; Menniti, Frank S.; Vance, Katie M.; Ogden, Kevin K.; Hansen, Kasper B.; Yuan, Hongjie; Myers, Scott J.; Dingledine, Ray

    2010-01-01

    The mammalian ionotropic glutamate receptor family encodes 18 gene products that coassemble to form ligand-gated ion channels containing an agonist recognition site, a transmembrane ion permeation pathway, and gating elements that couple agonist-induced conformational changes to the opening or closing of the permeation pore. Glutamate receptors mediate fast excitatory synaptic transmission in the central nervous system and are localized on neuronal and non-neuronal cells. These receptors regulate a broad spectrum of processes in the brain, spinal cord, retina, and peripheral nervous system. Glutamate receptors are postulated to play important roles in numerous neurological diseases and have attracted intense scrutiny. The description of glutamate receptor structure, including its transmembrane elements, reveals a complex assembly of multiple semiautonomous extracellular domains linked to a pore-forming element with striking resemblance to an inverted potassium channel. In this review we discuss International Union of Basic and Clinical Pharmacology glutamate receptor nomenclature, structure, assembly, accessory subunits, interacting proteins, gene expression and translation, post-translational modifications, agonist and antagonist pharmacology, allosteric modulation, mechanisms of gating and permeation, roles in normal physiological function, as well as the potential therapeutic use of pharmacological agents acting at glutamate receptors. PMID:20716669

  5. Central dysmyelination reduces the temporal fidelity of synaptic transmission and the reliability of postsynaptic firing during high-frequency stimulation.

    PubMed

    Kim, Sei Eun; Turkington, Karl; Kushmerick, Christopher; Kim, Jun Hee

    2013-10-01

    Auditory brain stem circuits rely on fast, precise, and reliable neurotransmission to process auditory information. To determine the fundamental role of myelination in auditory brain stem function, we examined the evoked auditory brain stem response (ABR) from the Long Evans shaker (LES) rat, which lacks myelin due to a genetic deletion of myelin basic protein. In control rats, the ABR evoked by a click consisted of five well-defined waves (denoted waves I-V). In LES rats, waves I, IV, and V were present, but waves II and III were undetectable, indicating disrupted function in the earliest stages of central nervous system auditory processing. In addition, the developmental shortening of the interval between waves I and IV that normally occurs in control rats was arrested and resulted in a significant increase in the central conduction time in LES rats. In brain stem slices, action potential transmission between the calyx of Held terminals and the medial nucleus of the trapezoid body (MNTB) neurons was delayed and less reliable in LES rats, although the resting potential, threshold, input resistance, and length of the axon initial segment of the postsynaptic MNTB neurons were normal. The amplitude of glutamatergic excitatory postsynaptic currents (EPSCs) and the degree of synaptic depression during high-frequency stimulation were not different between LES rats and controls, but LES rats exhibited a marked slow component to the EPSC decay and a much higher rate of presynaptic failures. Together, these results indicate that loss of myelin disrupts brain stem auditory processing, increasing central conduction time and reducing the reliability of neurotransmission. PMID:23843435

  6. Changes in synaptic transmission and protein expression in the brains of adult offspring after prenatal inhibition of the kynurenine pathway.

    PubMed

    Forrest, C M; Khalil, O S; Pisar, M; McNair, K; Kornisiuk, E; Snitcofsky, M; Gonzalez, N; Jerusalinsky, D; Darlington, L G; Stone, T W

    2013-12-19

    During early brain development, N-methyl-d-aspartate (NMDA) receptors are involved in cell migration, neuritogenesis, axon guidance and synapse formation, but the mechanisms which regulate NMDA receptor density and function remain unclear. The kynurenine pathway of tryptophan metabolism includes an agonist (quinolinic acid) and an antagonist (kynurenic acid) at NMDA receptors and we have previously shown that inhibition of the pathway using the kynurenine-3-monoxygenase inhibitor Ro61-8048 in late gestation produces rapid changes in protein expression in the embryos and effects on synaptic transmission lasting until postnatal day 21 (P21). The present study sought to determine whether any of these effects are maintained into adulthood. After prenatal injections of Ro61-8048 the litter was allowed to develop to P60 when some offspring were euthanized and the brains removed for examination. Analysis of protein expression by Western blotting revealed significantly reduced expression of the GluN2A subunit (32%) and the morphogenetic protein sonic hedgehog (31%), with a 29% increase in the expression of doublecortin, a protein associated with neurogenesis. No changes were seen in mRNA abundance using quantitative real-time polymerase chain reaction. Neuronal excitability was normal in the CA1 region of hippocampal slices but paired-pulse stimulation revealed less inhibition at short interpulse intervals. The amount of long-term potentiation was decreased by 49% in treated pups and recovery after low-frequency stimulation was delayed. The results not only strengthen the view that basal, constitutive kynurenine metabolism is involved in normal brain development, but also show that changes induced prenatally can affect the brains of adult offspring and those changes are quite different from those seen previously at weaning (P21). Those changes may be mediated by altered expression of NMDAR subunits and sonic hedgehog. PMID:24076085

  7. Excitatory and inhibitory synaptic transmission is differentially influenced by two ortho-substituted polychlorinated biphenyls in the hippocampal slice preparation

    SciTech Connect

    Kim, Kyung Ho; Inan, Salim Yalcin; Berman, Robert F.; Pessah, Isaac N.

    2009-06-01

    Exposure to polychlorinated biphenyls impairs cognition and behavior in children. Two environmental PCBs 2,2',3,3',4,4',5-heptachlorobiphenyl (PCB170) and 2,2',3,5',6-pentachlorobiphenyl (PCB95) were examined in vitro for influences on synaptic transmission in rat hippocampal slices. Field excitatory postsynaptic potentials (fEPSPs) were recorded in the CA1 region using a multi-electrode array. Perfusion with PCB170 (10 nM) had no effect on fEPSP slope relative to baseline period, whereas (100 nM) initially enhanced then depressed fEPSP slope. Perfusion of PCB95 (10 or 100 nM) persistently enhanced fEPSP slope > 200%, an effect that could be inhibited by dantrolene, a drug that attenuates ryanodine receptor signaling. Perfusion with picrotoxin (PTX) to block GABA neurotransmission resulted in a modest increase in fEPSP slope, whereas PTX + PCB170 (1-100 nM) persistently enhanced fEPSP slope in a dose dependent manner. fEPSP slope reached > 250% of baseline period in the presence of PTX + 100 nM PCB170, conditions that evoked marked epileptiform after-potential discharges. PCB95 and PCB170 were found to differentially influence the Ca{sup 2+}-dependence of [{sup 3}H]ryanodine-binding to hippocampal ryanodine receptors. Non-coplanar PCB congeners can differentially alter neurotransmission in a manner suggesting they can elicit imbalances between inhibitory and excitatory circuits within the hippocampus. Differential sensitization of ryanodine receptors by Ca{sup 2+} appears to mediate, at least in part, hippocampal excitotoxicity by non-coplanar PCBs.

  8. Age-dependent actions of dopamine on inhibitory synaptic transmission in superficial layers of mouse prefrontal cortex.

    PubMed

    Paul, Kush; Cox, Charles L

    2013-03-01

    Numerous developmental changes in the nervous system occur during the first several weeks of the rodent lifespan. Therefore, many characteristics of neuronal function described at the cellular level from in vitro slice experiments conducted during this early time period may not generalize to adult ages. We investigated the effect of dopamine (DA) on inhibitory synaptic transmission in superficial layers of the medial prefrontal cortex (PFC) in prepubertal [postnatal age (P; days) 12-20], periadolescent (P30-48), and adult (P70-100) mice. The PFC is associated with higher-level cognitive functions, such as working memory, and is associated with initiation, planning, and execution of actions, as well as motivation and cognition. It is innervated by DA-releasing fibers that arise from the ventral tegmental area. In slices from prepubertal mice, DA produced a biphasic modulation of inhibitory postsynaptic currents (IPSCs) recorded in layer II/III pyramidal neurons. Activation of D2-like receptors leads to an early suppression of the evoked IPSC, which was followed by a longer-lasting facilitation of the IPSC mediated by D1-like DA receptors. In periadolescent mice, the D2 receptor-mediated early suppression was significantly smaller compared with the prepubertal animals and absent in adult animals. Furthermore, we found significant differences in the DA-mediated lasting enhancement of the inhibitory response among the developmental groups. Our findings suggest that behavioral paradigms that elicit dopaminergic release in the PFC differentially modulate inhibition of excitatory pyramidal neuron output in prepuberty compared with periadolescence and adulthood in the superficial layers (II/III) of the cortex. PMID:23221420

  9. Mood disorders: regulation by metabotropic glutamate receptors.

    PubMed

    Pilc, Andrzej; Chaki, Shigeyuki; Nowak, Gabriel; Witkin, Jeffrey M

    2008-03-01

    Medicinal therapies for mood disorders neither fully serve the efficacy needs of patients nor are they free of side-effect issues. Although monoamine-based therapies are the primary current treatment approaches, both preclinical and clinical findings have implicated the excitatory neurotransmitter glutamate in the pathogenesis of major depressive disorders. The present commentary focuses on the metabotropic glutamate receptors and their relationship to mood disorders. Metabotropic glutamate (mGlu) receptors regulate glutamate transmission by altering the release of neurotransmitter and/or modulating the post-synaptic responses to glutamate. Convergent biochemical, pharmacological, behavioral, and clinical data will be reviewed that establish glutamatergic neurotransmission via mGlu receptors as a biologically relevant process in the regulation of mood and that these receptors may serve as novel targets for the discovery of small molecule modulators with unique antidepressant properties. Specifically, compounds that antagonize mGlu2, mGlu3, and/or mGlu5 receptors (e.g. LY341495, MGS0039, MPEP, MTEP) exhibit biochemical effects indicative of antidepressant effects as well as in vivo activity in animal models predictive of antidepressant efficacy. Both preclinical and clinical data have previously been presented to define NMDA and AMPA receptors as important targets for the modulation of major depression. In the present review, we present a model suggesting how the interplay of glutamate at the mGlu and at the ionotropic AMPA and NMDA receptors might account for the antidepressant-like effects of glutamatergic- and monoaminergic-based drugs affecting mood in patients. The current data lead to the hypothesis that mGlu-based compounds and conventional antidepressants impact a network of interactive effects that converge upon a down regulation of NMDA receptor function and an enhancement in AMPA receptor signaling. PMID:18164691

  10. Dysfunctional TCA-Cycle Metabolism in Glutamate Dehydrogenase Deficient Astrocytes.

    PubMed

    Nissen, Jakob D; Pajęcka, Kamilla; Stridh, Malin H; Skytt, Dorte M; Waagepetersen, Helle S

    2015-12-01

    Astrocytes take up glutamate in the synaptic area subsequent to glutamatergic transmission by the aid of high affinity glutamate transporters. Glutamate is converted to glutamine or metabolized to support intermediary metabolism and energy production. Glutamate dehydrogenase (GDH) and aspartate aminotransferase (AAT) catalyze the reversible reaction between glutamate and α-ketoglutarate, which is the initial step for glutamate to enter TCA cycle metabolism. In contrast to GDH, AAT requires a concomitant interconversion of oxaloacetate and aspartate. We have investigated the role of GDH in astrocyte glutamate and glucose metabolism employing siRNA mediated knock down (KD) of GDH in cultured astrocytes using stable and radioactive isotopes for metabolic mapping. An increased level of aspartate was observed upon exposure to [U-(13) C]glutamate in astrocytes exhibiting reduced GDH activity. (13) C Labeling of aspartate and TCA cycle intermediates confirmed that the increased amount of aspartate is associated with elevated TCA cycle flux from α-ketoglutarate to oxaloacetate, i.e. truncated TCA cycle. (13) C Glucose metabolism was elevated in GDH deficient astrocytes as observed by increased de novo synthesis of aspartate via pyruvate carboxylation. In the absence of glucose, lactate production from glutamate via malic enzyme was lower in GDH deficient astrocytes. In conclusions, our studies reveal that metabolism via GDH serves an important anaplerotic role by adding net carbon to the TCA cycle. A reduction in GDH activity seems to cause the astrocytes to up-regulate activity in pathways involved in maintaining the amount of TCA cycle intermediates such as pyruvate carboxylation as well as utilization of alternate substrates such as branched chain amino acids. PMID:26221781

  11. The glutamate homeostasis hypothesis of addiction.

    PubMed

    Kalivas, Peter W

    2009-08-01

    Addiction is associated with neuroplasticity in the corticostriatal brain circuitry that is important for guiding adaptive behaviour. The hierarchy of corticostriatal information processing that normally permits the prefrontal cortex to regulate reinforcement-seeking behaviours is impaired by chronic drug use. A failure of the prefrontal cortex to control drug-seeking behaviours can be linked to an enduring imbalance between synaptic and non-synaptic glutamate, termed glutamate homeostasis. The imbalance in glutamate homeostasis engenders changes in neuroplasticity that impair communication between the prefrontal cortex and the nucleus accumbens. Some of these pathological changes are amenable to new glutamate- and neuroplasticity-based pharmacotherapies for treating addiction. PMID:19571793

  12. Circuit Mapping by UV Uncaging of Glutamate

    PubMed Central

    Shepherd, Gordon M. G.

    2014-01-01

    In laser photostimulation, small clusters of neurons in brain slices are induced to fire action potentials by focal glutamate uncaging, and synaptic connectivity between photoexcited presynaptic neurons and individual postsynaptic neurons is assessed by intracellular recording of synaptic events. With a scanner, this process can be repeated sequentially across a patterned array of stimulus locations, generating maps of neurons’ local sources of synaptic inputs. Laser scanning photostimulation (LSPS) based on patterned glutamate uncaging offers an efficient, quantitative, optical-electrophysiological way to map synaptic circuits in brain slices. PMID:22949715

  13. Segregated Glycine-Glutamate Co-transmission from vGluT3 Amacrine Cells to Contrast-Suppressed and Contrast-Enhanced Retinal Circuits.

    PubMed

    Lee, Seunghoon; Zhang, Yi; Chen, Minggang; Zhou, Z Jimmy

    2016-04-01

    Since the introduction of Dale's principle of "one neuron releases one transmitter at all its synapses," a growing number of exceptions to this principle have been identified. While the concept of neurotransmitter co-release by a single neuron is now well accepted, the specific synaptic circuitry and functional advantage of co-neurotransmission remain poorly understood in general. Here we report Ca(2+)-dependent co-release of a new combination of inhibitory and excitatory neurotransmitters, namely, glycine and glutamate, by the vGluT3-expressing amacrine cell (GAC) in the mouse retina. GACs selectively make glycinergic synapses with uniformity detectors (UDs) and provide a major inhibitory drive that underlies the suppressed-by-contrast trigger feature of UDs. Meanwhile, GACs release glutamate to excite OFF alpha ganglion cells and a few other nonlinear, contrast-sensitive ganglion cells. This coordinated inhibition and excitation of two separate neuronal circuits by a single interneuron suggests a unique advantage in differential detection of visual field uniformity and contrast. PMID:26996083

  14. [Functional changes in the chromatophilic substance and RNA content of the cytoplasm of sympathetic neurons in the presence of synaptic transmission disorders].

    PubMed

    Gorelikov, P L

    1981-07-01

    At a disturbed synaptic transmission in the rabbit cranial sympathetic cervical ganglion in histological sections stained with gallocyanin chrome alum, distribution of the chromatophilic substance was studied, and in the same sections RNA content was determined cytophotometrically. In ganglia of intact animals three groups of neurons with various structure of the chromatophilic substance were defined and their quantitative relation was stated. After administration of various doses of the ganglio-blockader, there was an essential difference in the changes of the chromatophilic substance, but they were unitypical in mono- and double-nuclear neurons. In the same cells, the synaptic blockade produced a rather great increase in the content of the cytoplasmic RNA. Comparing the quantitative data with the visual observation results, a conclusion was made that it is not reliable to use any changes in the chromatophilic substance as a criterium on quantitative shifts in the neuronal RNA and for the morphological test of the neuronal functional activity. PMID:6170279

  15. Differential effects of N-acetyl-aspartyl-glutamate on synaptic and extrasynaptic NMDA receptors are subunit- and pH-dependent in the CA1 region of the mouse hippocampus.

    PubMed

    Khacho, Pamela; Wang, Boyang; Ahlskog, Nina; Hristova, Elitza; Bergeron, Richard

    2015-10-01

    Ischemic strokes cause excessive release of glutamate, leading to overactivation of N-methyl-d-aspartate receptors (NMDARs) and excitotoxicity-induced neuronal death. For this reason, inhibition of NMDARs has been a central focus in identifying mechanisms to avert this extensive neuronal damage. N-acetyl-aspartyl-glutamate (NAAG), the most abundant neuropeptide in the brain, is neuroprotective in ischemic conditions in vivo. Despite this evidence, the exact mechanism underlying its neuroprotection, and more specifically its effect on NMDARs, is currently unknown due to conflicting results in the literature. Here, we uncover a pH-dependent subunit-specific action of NAAG on NMDARs. Using whole-cell electrophysiological recordings on acute hippocampal slices from adult mice and on HEK293 cells, we found that NAAG increases synaptic GluN2A-containing NMDAR EPSCs, while effectively decreasing extrasynaptic GluN2B-containing NMDAR EPSCs in physiological pH. Intriguingly, the results of our study further show that in low pH, which is a physiological occurrence during ischemia, NAAG depresses GluN2A-containing NMDAR EPSCs and amplifies its inhibitory effect on GluN2B-containing NMDAR EPSCs, as well as upregulates the surface expression of the GluN2A subunit. Altogether, our data demonstrate that NAAG has differential effects on NMDAR function based on subunit composition and pH. These findings suggest that the role of NAAG as a neuroprotective agent during an ischemic stroke is likely mediated by its ability to reduce NMDAR excitation. The inhibitory effect of NAAG on NMDARs and its enhanced function in acidic conditions make NAAG a prime therapeutic agent for the treatment of ischemic events. PMID:26303888

  16. Systemic dexmedetomidine augments inhibitory synaptic transmission in the superficial dorsal horn through activation of descending noradrenergic control: an in vivo patch-clamp analysis of analgesic mechanisms.

    PubMed

    Funai, Yusuke; Pickering, Anthony Edward; Uta, Daisuke; Nishikawa, Kiyonobu; Mori, Takashi; Asada, Akira; Imoto, Keiji; Furue, Hidemasa

    2014-03-01

    α2-Adrenoceptors are widely distributed throughout the central nervous system (CNS) and the systemic administration of α2-agonists such as dexmedetomidine produces clinically useful, centrally mediated sedation and analgesia; however, these same actions also limit the utility of these agents (ie, unwanted sedative actions). Despite a wealth of data on cellular and synaptic actions of α2-agonists in vitro, it is not known which neuronal circuits are modulated in vivo to produce the analgesic effect. To address this issue, we made in vivo recordings of membrane currents and synaptic activities in superficial spinal dorsal horn neurons and examined their responses to systemic dexmedetomidine. We found that dexmedetomidine at doses that produce analgesia (<10 μg/kg) enhanced inhibitory postsynaptic transmission within the superficial dorsal horn without altering excitatory synaptic transmission or evoking direct postsynaptic membrane currents. In contrast, higher doses of dexmedetomidine (>10 μg/kg) induced outward currents by a direct postsynaptic action. The dexmedetomidine-mediated inhibitory postsynaptic current facilitation was not mimicked by spinal application of dexmedetomidine and was absent in spinalized rats, suggesting that it acts at a supraspinal site. Furthermore, it was inhibited by spinal application of the α1-antagonist prazosin. In the brainstem, low doses of systemic dexmedetomidine produced an excitation of locus coeruleus neurons. These results suggest that systemic α2-adrenoceptor stimulation may facilitate inhibitory synaptic responses in the superficial dorsal horn to produce analgesia mediated by activation of the pontospinal noradrenergic inhibitory system. This novel mechanism may provide new targets for intervention, perhaps allowing analgesic actions to be dissociated from excessive sedation. PMID:24355412

  17. Systemic dexmedetomidine augments inhibitory synaptic transmission in the superficial dorsal horn through activation of descending noradrenergic control: an in vivo patch-clamp analysis of analgesic mechanisms

    PubMed Central

    Funai, Yusuke; Pickering, Anthony Edward; Uta, Daisuke; Nishikawa, Kiyonobu; Mori, Takashi; Asada, Akira; Imoto, Keiji; Furue, Hidemasa

    2014-01-01

    α2-adrenoceptors are widely distributed throughout the central nervous system (CNS) and the systemic administration of α2-agonists such as dexmedetomidine produces clinically useful, centrally-mediated sedation and analgesia; however, these same actions also limit the utility of these agents (ie unwanted sedative actions). Despite a wealth of data on cellular and synaptic actions of α2-agonists in vitro, it is not known which neuronal circuits are modulated in vivo to produce the analgesic effect. To address this issue, we made in vivo recordings of membrane currents and synaptic activities in superficial spinal dorsal horn neurons and examined their responses to systemic dexmedetomidine. We found that dexmedetomidine at doses that produce analgesia (<10 μg/kg) enhanced inhibitory postsynaptic transmission within the superficial dorsal horn without altering excitatory synaptic transmission or evoking direct postsynaptic membrane currents. In contrast, higher doses of dexmedetomidine (>10 μg/kg) induced outward currents by a direct postsynaptic action. The dexmedetomidine-mediated inhibitory postsynaptic current (IPSC) facilitation was not mimicked by spinal application of dexmedetomidine and was absent in spinalized rats, suggesting it acts at a supraspinal site. Further it was inhibited by spinal application of the α1-antagonist prazosin. In the brain stem, low doses of systemic dexmedetomidine produced an excitation of locus coeruleus neurons. These results suggest that systemic α2-adrenoceptor stimulation may facilitate inhibitory synaptic responses in the superficial dorsal horn to produce analgesia mediated by activation of the pontospinal noradrenergic inhibitory system. This novel mechanism may provide new targets for intervention perhaps allowing analgesic actions to be dissociated from excessive sedation. PMID:24355412

  18. Pathophysiology of depression and innovative treatments: remodeling glutamatergic synaptic connections

    PubMed Central

    Duman, Ronald S.

    2014-01-01

    Despite the complexity and heterogeneity of mood disorders, basic and clinical research studies have begun to elucidate the pathophysiology of depression and to identify rapid, efficacious antidepressant agents. Stress and depression are associated with neuronal atrophy, characterized by loss of synaptic connections in key cortical and limbic brain regions implicated in depression. This is thought to occur in part via decreased expression and function of growth factors, such as brain-derived neurotrophic factor (BDNF), in the prefrontal cortex (PFC) and hippocampus. These structural alterations are difficult to reverse with typical antidepressants. However, recent studies demonstrate that ketamine, an N-methyl-D-aspartate (NMDA) receptor antagonist that produces rapid antidepressant actions in treatment-resistant depressed patients, rapidly increases spine synapses in the PFC and reverses the deficits caused by chronic stress. This is thought to occur by disinhibition of glutamate transmission, resulting in a rapid but transient burst of glutamate, followed by an increase in BDNF release and activation of downstream signaling pathways that stimulate synapse formation. Recent work demonstrates that the rapid-acting antidepressant effects of scopolamine, a muscarinic receptor antagonist, are also associated with increased glutamate transmission and synapse formation. These findings have resulted in testing and identification of additional targets and agents that influence glutamate transmission and have rapid antidepressant actions in rodent models and in clinical trials. Together these studies have created tremendous excitement and hope for a new generation of rapid, efficacious antidepressants. PMID:24733968

  19. Excitatory synapses are stronger in the hippocampus of Rett syndrome mice due to altered synaptic trafficking of AMPA-type glutamate receptors.

    PubMed

    Li, Wei; Xu, Xin; Pozzo-Miller, Lucas

    2016-03-15

    Deficits in long-term potentiation (LTP) at central excitatory synapses are thought to contribute to cognitive impairments in neurodevelopmental disorders associated with intellectual disability and autism. Using the methyl-CpG-binding protein 2 (Mecp2) knockout (KO) mouse model of Rett syndrome, we show that naïve excitatory synapses onto hippocampal pyramidal neurons of symptomatic mice have all of the hallmarks of potentiated synapses. Stronger Mecp2 KO synapses failed to undergo LTP after either theta-burst afferent stimulation or pairing afferent stimulation with postsynaptic depolarization. On the other hand, basal synaptic strength and LTP were not affected in slices from younger presymptomatic Mecp2 KO mice. Furthermore, spine synapses in pyramidal neurons from symptomatic Mecp2 KO are larger and do not grow in size or incorporate GluA1 subunits after electrical or chemical LTP. Our data suggest that LTP is occluded in Mecp2 KO mice by already potentiated synapses. The higher surface levels of GluA1-containing receptors are consistent with altered expression levels of proteins involved in AMPA receptor trafficking, suggesting previously unidentified targets for therapeutic intervention for Rett syndrome and other MECP2-related disorders. PMID:26929363

  20. Adenosine receptor activation is responsible for prolonged depression of synaptic transmission after spreading depolarization in brain slices.

    PubMed

    Lindquist, B E; Shuttleworth, C W

    2012-10-25

    Spreading depolarization (SD) is a slowly propagating, coordinated depolarization of brain tissue, which is followed by a transient (5-10min) depression of synaptic activity. The mechanisms for synaptic depression after SD are incompletely understood. We examined the relative contributions of action potential failure and adenosine receptor activation to the suppression of evoked synaptic activity in murine brain slices. Focal micro-injection of potassium chloride (KCl) was used to induce SD and synaptic potentials were evoked by electrical stimulation of Schaffer collateral inputs to hippocampal area Cornu Ammonis area 1 (CA1). SD was accompanied by loss of both presynaptic action potentials (as assessed from fiber volleys) and field excitatory postsynaptic potentials (fEPSPs). Fiber volleys recovered rapidly upon neutralization of the extracellular direct current (DC) potential, whereas fEPSPs underwent a secondary suppression phase lasting several minutes. Paired-pulse ratio was elevated during the secondary suppression period, consistent with a presynaptic mechanism of synaptic depression. A transient increase in extracellular adenosine concentration was detected during the period of secondary suppression. Antagonists of adenosine A1 receptors (8-cyclopentyl-1,3-dipropylxanthine [DPCPX] or 8-cyclopentyl-1,3-dimethylxanthine [8-CPT]) greatly accelerated fEPSP recovery and abolished increases in paired-pulse ratio normally observed after SD. The duration of fEPSP suppression was correlated with both the duration of the DC shift and the area of tissue depolarized, consistent with the model that adenosine accumulates in proportion to the metabolic burden of SD. These results suggest that in brain slices, the duration of the DC shift approximately defined the period of action potential failure, but the secondary depression of evoked responses was in large part due to endogenous adenosine accumulation after SD. PMID:22864185

  1. Botulinum and Tetanus Neurotoxin-Induced Blockade of Synaptic Transmission in Networked Cultures of Human and Rodent Neurons.

    PubMed

    Beske, Phillip H; Bradford, Aaron B; Grynovicki, Justin O; Glotfelty, Elliot J; Hoffman, Katie M; Hubbard, Kyle S; Tuznik, Kaylie M; McNutt, Patrick M

    2016-02-01

    Clinical manifestations of tetanus and botulism result from an intricate series of interactions between clostridial neurotoxins (CNTs) and nerve terminal proteins that ultimately cause proteolytic cleavage of SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins and functional blockade of neurotransmitter release. Although detection of cleaved SNARE proteins is routinely used as a molecular readout of CNT intoxication in cultured cells, impaired synaptic function is the pathophysiological basis of clinical disease. Work in our laboratory has suggested that the blockade of synaptic neurotransmission in networked neuron cultures offers a phenotypic readout of CNT intoxication that more closely replicates the functional endpoint of clinical disease. Here, we explore the value of measuring spontaneous neurotransmission frequencies as novel and functionally relevant readouts of CNT intoxication. The generalizability of this approach was confirmed in primary neuron cultures as well as human and mouse stem cell-derived neurons exposed to botulinum neurotoxin serotypes A-G and tetanus neurotoxin. The sensitivity and specificity of synaptic activity as a reporter of intoxication was evaluated in assays representing the principal clinical and research purposes of in vivo studies. Our findings confirm that synaptic activity offers a novel and functionally relevant readout for the in vitro characterizations of CNTs. They further suggest that the analysis of synaptic activity in neuronal cell cultures can serve as a surrogate for neuromuscular paralysis in the mouse lethal assay, and therefore is expected to significantly reduce the need for terminal animal use in toxin studies and facilitate identification of candidate therapeutics in cell-based screening assays. PMID:26615023

  2. Imaging extracellular waves of glutamate during calcium signaling in cultured astrocytes.

    PubMed

    Innocenti, B; Parpura, V; Haydon, P G

    2000-03-01

    A growing body of evidence proposes that glial cells have the potential to play a role as modulators of neuronal activity and synaptic transmission by releasing the neurotransmitter glutamate (Arague et al., 1999). We explore the spatial nature of glutamate release from astrocytes with an enzyme-linked assay system and CCD imaging technology. In the presence of glutamate, L-glutamic dehydrogenase (GDH) reduces NAD(+) to NADH, a product that fluoresces when excited with UV light. Theoretically, provided that GDH and NAD(+) are present in the bathing saline, the release of glutamate from stimulated astrocytes can be optically detected by monitoring the accumulation of NADH. Indeed, stimuli that induce a wave of elevated calcium among astrocytes produced a corresponding spread of extracellular NADH fluorescence. Treatment of cultures either with thapsigargin, to deplete internal calcium stores, or with the membrane-permeant calcium chelator BAPTA AM significantly decreased the accumulation of NADH, demonstrating that this fluorometric assay effectively monitors calcium-dependent glutamate release. With a temporal resolution of 500 msec and spatial resolution of approximately 20 micrometer, discrete regions of glutamate release were not reliably resolved. The wave of glutamate release that underlies the NADH fluorescence propagated at an average speed of approximately 26 micrometer/sec, correlating with the rate of calcium wave progression (10-30 micrometer/sec), and caused a localized accumulation of glutamate in the range of 1-100 microM. Further analysis of the fluorescence accumulation clearly demonstrated that glutamate is released in a regenerative manner, with subsequent cells that are involved in the calcium wave releasing additional glutamate. PMID:10684881

  3. Presynaptic inhibitory effects of fluvoxamine, a selective serotonin reuptake inhibitor, on nociceptive excitatory synaptic transmission in spinal superficial dorsal horn neurons of adult mice.

    PubMed

    Tomoyose, Orie; Kodama, Daisuke; Ono, Hideki; Tanabe, Mitsuo

    2014-01-01

    Fluvoxamine, a selective serotonin (5-HT) reuptake inhibitor, has been shown to exert analgesic effects in humans and laboratory animals. However, its effects on spinal nociceptive synaptic transmission have not been fully characterized. Here, whole-cell recordings were made from dorsal horn neurons in spinal slices with attached dorsal roots from adult mice, and the effects of fluvoxamine on monosynaptic A-fiber- and C-fiber-mediated excitatory postsynaptic currents (EPSCs) evoked in response to electrical stimulation of a dorsal root were studied. Fluvoxamine (10 - 100 μM) concentration-dependently suppressed both monosynaptic A-fiber- and C-fiber-mediated EPSCs, which were attenuated by the selective 5-HT1A receptor antagonist WAY100635. In the presence of the selective 5-HT3 receptor antagonist tropisetron, fluvoxamine hardly suppressed A-fiber-mediated EPSCs, whereas its inhibitory effect on C-fiber-mediated EPSCs was not affected. Although fluvoxamine increased the paired-pulse ratio of A-fiber-mediated EPSCs, it increased the frequency of spontaneous and miniature EPSCs (sEPSCs and mEPSCs). Since sEPSCs and mEPSCs appeared to arise largely from spinal interneurons, we then recorded strontium-evoked asynchronous events occurring after A-fiber stimulation, whose frequency was reduced by fluvoxamine. These results suggest that fluvoxamine reduces excitatory synaptic transmission from primary afferent fibers via presynaptic mechanisms involving 5-HT1A and/or 5-HT3 receptors, which may contribute to its analgesic effects. PMID:25252797

  4. Activity Level-Dependent Synapse-Specific AMPA Receptor Trafficking Regulates Transmission Kinetics

    PubMed Central

    Zhu, J. Julius

    2009-01-01

    Central glutamatergic synapses may express AMPA-sensitive glutamate receptors (AMPA-Rs) with distinct gating properties and exhibit different transmission dynamics, which are important for computing various synaptic inputs received at different populations of synapses. However, how glutamatergic synapses acquire AMPA-Rs with distinct kinetics to influence synaptic integration remains poorly understood. Here I report synapse-specific trafficking of distinct AMPA-Rs in rat cortical layer 4 stellate and layer 5 pyramidal neurons. The analysis indicates that in single layer 4 stellate neurons thalamocortical synapses generate faster synaptic responses than intracortical synapses. Moreover, GluR1-containing AMPA-Rs traffic selectively into intracortical synapses, and this process requires sensory experience-dependent activity and slows down transmission kinetics. GluR4-containing AMPA-Rs traffic more heavily into thalamocortical synapses than intracortical synapses, and this process requires spontaneous synaptic activity and speeds up transmission kinetics. GluR2-containing AMPA-Rs traffic equally into both thalamocortical and intracortical synapses, and this process requires no synaptic activity and resets transmission kinetics. Notably, synaptic trafficking of distinct AMPA-Rs differentially regulates synaptic integration. Thus, synapse-specific AMPA-R trafficking coarsely sets and synaptic activity finely tunes transmission kinetics and integration properties at different synapses in central neurons. PMID:19439609

  5. Effect of cannabis on glutamate signalling in the brain: A systematic review of human and animal evidence.

    PubMed

    Colizzi, Marco; McGuire, Philip; Pertwee, Roger G; Bhattacharyya, Sagnik

    2016-05-01

    Use of cannabis or delta-9-tetrahydrocannabinol (Δ9-THC), its main psychoactive ingredient, is associated with psychotic symptoms or disorder. However, the neurochemical mechanism that may underlie this psychotomimetic effect is poorly understood. Although dopaminergic dysfunction is generally recognized as the final common pathway in psychosis, evidence of the effects of Δ9-THC or cannabis use on dopaminergic measures in the brain is equivocal. In fact, it is thought that cannabis or Δ9-THC may not act on dopamine firing directly but indirectly by altering glutamate neurotransmission. Here we systematically review all studies examining acute and chronic effects of cannabis or Δ9-THC on glutamate signalling in both animals and man. Limited research carried out in humans tends to support the evidence that chronic cannabis use reduces levels of glutamate-derived metabolites in both cortical and subcortical brain areas. Research in animals tends to consistently suggest that Δ9-THC depresses glutamate synaptic transmission via CB1 receptor activation, affecting glutamate release, inhibiting receptors and transporters function, reducing enzyme activity, and disrupting glutamate synaptic plasticity after prolonged exposure. PMID:26987641

  6. Relevance of exocytotic glutamate release from retinal glia.

    PubMed

    Slezak, Michal; Grosche, Antje; Niemiec, Aurore; Tanimoto, Naoyuki; Pannicke, Thomas; Münch, Thomas A; Crocker, Britni; Isope, Philippe; Härtig, Wolfgang; Beck, Susanne C; Huber, Gesine; Ferracci, Geraldine; Perraut, Martine; Reber, Michael; Miehe, Monique; Demais, Valérie; Lévêque, Christian; Metzger, Daniel; Szklarczyk, Klaudia; Przewlocki, Ryszard; Seeliger, Mathias W; Sage-Ciocca, Dominique; Hirrlinger, Johannes; Reichenbach, Andreas; Reibel, Sophie; Pfrieger, Frank W

    2012-05-10

    Glial cells release molecules that influence brain development, function, and disease. Calcium-dependent exocytosis has been proposed as potential release mechanism in astroglia, but the physiological relevance of "gliotransmission" in vivo remains controversial. We focused on the impact of glial exocytosis on sensory transduction in the retina. To this end, we generated transgenic mice to block exocytosis by Cre recombinase-dependent expression of the clostridial botulinum neurotoxin serotype B light chain, which cleaves vesicle-associated membrane protein 1-3. Ubiquitous and neuronal toxin expression caused perinatal lethality and a reduction of synaptic transmission thus validating transgene function. Toxin expression in Müller cells inhibited vesicular glutamate release and impaired glial volume regulation but left retinal histology and visual processing unaffected. Our model to study gliotransmission in vivo reveals specific functions of exocytotic glutamate release in retinal glia. PMID:22578502

  7. Concurrent Imaging of Synaptic Vesicle Recycling and Calcium Dynamics

    PubMed Central

    Li, Haiyan; Foss, Sarah M.; Dobryy, Yuriy L.; Park, C. Kevin; Hires, Samuel Andrew; Shaner, Nathan C.; Tsien, Roger Y.; Osborne, Leslie C.; Voglmaier, Susan M.

    2011-01-01

    Synaptic transmission involves the calcium dependent release of neurotransmitter from synaptic vesicles. Genetically encoded optical probes emitting different wavelengths of fluorescent light in response to neuronal activity offer a powerful approach to understand the spatial and temporal relationship of calcium dynamics to the release of neurotransmitter in defined neuronal populations. To simultaneously image synaptic vesicle recycling and changes in cytosolic calcium, we developed a red-shifted reporter of vesicle recycling based on a vesicular glutamate transporter, VGLUT1-mOrange2 (VGLUT1-mOr2), and a presynaptically localized green calcium indicator, synaptophysin-GCaMP3 (SyGCaMP3) with a large dynamic range. The fluorescence of VGLUT1-mOr2 is quenched by the low pH of synaptic vesicles. Exocytosis upon electrical stimulation exposes the luminal mOr2 to the neutral extracellular pH and relieves fluorescence quenching. Reacidification of the vesicle upon endocytosis again reduces fluorescence intensity. Changes in fluorescence intensity thus monitor synaptic vesicle exo- and endocytosis, as demonstrated previously for the green VGLUT1-pHluorin. To monitor changes in calcium, we fused the synaptic vesicle protein synaptophysin to the recently improved calcium indicator GCaMP3. SyGCaMP3 is targeted to presynaptic varicosities, and exhibits changes in fluorescence in response to electrical stimulation consistent with changes in calcium concentration. Using real time imaging of both reporters expressed in the same synapses, we determine the time course of changes in VGLUT1 recycling in relation to changes in presynaptic calcium concentration. Inhibition of P/Q- and N-type calcium channels reduces calcium levels, as well as the rate of synaptic vesicle exocytosis and the fraction of vesicles released. PMID:22065946

  8. Acute and Chronic Effects of Ethanol on Learning-Related Synaptic Plasticity

    PubMed Central

    Zorumski, Charles F.; Mennerick, Steven; Izumi, Yukitoshi

    2014-01-01

    Alcoholism is associated with acute and long-term cognitive dysfunction including memory impairment, resulting in substantial disability and cost to society. Thus, understanding how ethanol impairs cognition is essential for developing treatment strategies to dampen its adverse impact. Memory processing is thought to involve persistent, use-dependent changes in synaptic transmission, and ethanol alters the activity of multiple signaling molecules involved in synaptic processing, including modulation of the glutamate and gamma-aminobutyric acid (GABA) transmitter systems that mediate most fast excitatory and inhibitory transmission in the brain. Effects on glutamate and GABA receptors contribute to ethanol-induced changes in long-term potentiation (LTP) and long-term depression (LTD), forms of synaptic plasticity thought to underlie memory acquisition. In this paper, we review the effects of ethanol on learning-related forms of synaptic plasticity with emphasis on changes observed in the hippocampus, a brain region that is critical for encoding contextual and episodic memories. We also include studies in other brain regions as they pertain to altered cognitive and mental function. Comparison of effects in the hippocampus to other brain regions is instructive for understanding the complexities of ethanol’s acute and long-term pharmacological consequences. PMID:24447472

  9. Vesicular Glutamate Transport Promotes Dopamine Storage and Glutamate Corelease In Vivo

    PubMed Central

    Hnasko, Thomas S.; Chuhma, Nao; Zhang, Hui; Goh, Germaine Y.; Sulzer, David; Palmiter, Richard D.; Rayport, Stephen; Edwards, Robert H.

    2010-01-01

    SUMMARY Dopamine neurons in the ventral tegmental area (VTA) play an important role in the motivational systems underlying drug addiction, and recent work has suggested that they also release the excitatory neurotransmitter glutamate. To assess a physiological role for glutamate corelease, we disrupted the expression of vesicular glutamate transporter 2 selectively in dopamine neurons. The conditional knockout abolishes glutamate release from midbrain dopamine neurons in culture and severely reduces their excitatory synaptic output in mesoaccumbens slices. Baseline motor behavior is not affected, but stimulation of locomotor activity by cocaine is impaired, apparently through a selective reduction of dopamine stores in the projection of VTA neurons to ventral striatum. Glutamate co-entry promotes monoamine storage by increasing the pH gradient that drives vesicular monoamine transport. Remarkably, low concentrations of glutamate acidify synaptic vesicles more slowly but to a greater extent than equimolar Cl−, indicating a distinct, presynaptic mechanism to regulate quantal size. PMID:20223200

  10. Sex differences in cerebellar synaptic transmission and sex-specific responses to autism-linked Gabrb3 mutations in mice

    PubMed Central

    Mercer, Audrey A; Palarz, Kristin J; Tabatadze, Nino; Woolley, Catherine S; Raman, Indira M

    2016-01-01

    Neurons of the cerebellar nuclei (CbN) transmit cerebellar signals to premotor areas. The cerebellum expresses several autism-linked genes, including GABRB3, which encodes GABAA receptor β3 subunits and is among the maternal alleles deleted in Angelman syndrome. We tested how this Gabrb3 m-/p+ mutation affects CbN physiology in mice, separating responses of males and females. Wild-type mice showed sex differences in synaptic excitation, inhibition, and intrinsic properties. Relative to females, CbN cells of males had smaller synaptically evoked mGluR1/5-dependent currents, slower Purkinje-mediated IPSCs, and lower spontaneous firing rates, but rotarod performances were indistinguishable. In mutant CbN cells, IPSC kinetics were unchanged, but mutant males, unlike females, showed enlarged mGluR1/5 responses and accelerated spontaneous firing. These changes appear compensatory, since mutant males but not females performed indistinguishably from wild-type siblings on the rotarod task. Thus, sex differences in cerebellar physiology produce similar behavioral output, but provide distinct baselines for responses to mutations. DOI: http://dx.doi.org/10.7554/eLife.07596.001 PMID:27077953

  11. Loss of neuronal GSK3β reduces dendritic spine stability and attenuates excitatory synaptic transmission via β-catenin.

    PubMed

    Ochs, S M; Dorostkar, M M; Aramuni, G; Schön, C; Filser, S; Pöschl, J; Kremer, A; Van Leuven, F; Ovsepian, S V; Herms, J

    2015-04-01

    Central nervous glycogen synthase kinase 3β (GSK3β) is implicated in a number of neuropsychiatric diseases, such as bipolar disorder, depression, schizophrenia, fragile X syndrome or anxiety disorder. Many drugs employed to treat these conditions inhibit GSK3β either directly or indirectly. We studied how conditional knockout of GSK3β affected structural synaptic plasticity. Deletion of the GSK3β gene in a subset of cortical and hippocampal neurons in adult mice led to reduced spine density. In vivo imaging revealed that this was caused by a loss of persistent spines, whereas stabilization of newly formed spines was reduced. In electrophysiological recordings, these structural alterations correlated with a considerable drop in the frequency and amplitude of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor-dependent miniature excitatory postsynaptic currents. Expression of constitutively active β-catenin caused reduction in spine density and electrophysiological alterations similar to GSK3β knockout, suggesting that the effects of GSK3β knockout were mediated by the accumulation of β-catenin. In summary, changes of dendritic spines, both in quantity and in morphology, are correlates of experience-dependent synaptic plasticity; thus, these results may help explain the mechanism of action of psychotropic drugs inhibiting GSK3β. PMID:24912492

  12. 5-HT7 receptors as modulators of neuronal excitability, synaptic transmission and plasticity: physiological role and possible implications in autism spectrum disorders

    PubMed Central

    Ciranna, Lucia; Catania, Maria Vincenza

    2014-01-01

    Serotonin type 7 receptors (5-HT7) are expressed in several brain areas, regulate brain development, synaptic transmission and plasticity, and therefore are involved in various brain functions such as learning and memory. A number of studies suggest that 5-HT7 receptors could be potential pharmacotherapeutic target for cognitive disorders. Several abnormalities of serotonergic system have been described in patients with autism spectrum disorder (ASD), including abnormal activity of 5-HT transporter, altered blood and brain 5-HT levels, reduced 5-HT synthesis and altered expression of 5-HT receptors in the brain. A specific role for 5-HT7 receptors in ASD has not yet been demonstrated but some evidence implicates their possible involvement. We have recently shown that 5-HT7 receptor activation rescues hippocampal synaptic plasticity in a mouse model of Fragile X Syndrome, a monogenic cause of autism. Several other studies have shown that 5-HT7 receptors modulate behavioral flexibility, exploratory behavior, mood disorders and epilepsy, which include core and co-morbid symptoms of ASD. These findings further suggest an involvement of 5-HT7 receptors in ASD. Here, we review the physiological roles of 5-HT7 receptors and their implications in Fragile X Syndrome and other ASD. PMID:25221471

  13. Nonvesicular Release of Glutamate by Glial xCT Transporters Suppresses Glutamate Receptor Clustering In Vivo

    PubMed Central

    Augustin, Hrvoje; Grosjean, Yael; Chen, Kaiyun; Sheng, Qi; Featherstone, David E.

    2008-01-01

    We hypothesized that cystine/glutamate transporters (xCTs) might be critical regulators of ambient extracellular glutamate levels in the nervous system and that misregulation of this glutamate pool might have important neurophysiological and/or behavioral consequences. To test this idea, we identified and functionally characterized a novel Drosophila xCT gene, which we subsequently named “genderblind” (gb). Genderblind is expressed in a previously overlooked subset of peripheral and central glia. Genetic elimination of gb causes a 50% reduction in extracellular glutamate concentration, demonstrating that xCT transporters are important regulators of extracellular glutamate. Consistent with previous studies showing that extracellular glutamate regulates postsynaptic glutamate receptor clustering, gb mutants show a large (200–300%) increase in the number of postsynaptic glutamate receptors. This increase in postsynaptic receptor abundance is not accompanied by other obvious synaptic changes and is completely rescued when synapses are cultured in wild-type levels of glutamate. Additional in situ pharmacology suggests that glutamate-mediated suppression of glutamate receptor clustering depends on receptor desensitization. Together, our results suggest that (1) xCT transporters are critical for regulation of ambient extracellular glutamate in vivo; (2) ambient extracellular glutamate maintains some receptors constitutively desensitized in vivo; and (3) constitutive desensitization of ionotropic glutamate receptors suppresses their ability to cluster at synapses. PMID:17202478

  14. Activity-Dependent Plasticity of Astroglial Potassium and Glutamate Clearance

    PubMed Central

    Cheung, Giselle; Sibille, Jérémie; Zapata, Jonathan; Rouach, Nathalie

    2015-01-01

    Recent evidence has shown that astrocytes play essential roles in synaptic transmission and plasticity. Nevertheless, how neuronal activity alters astroglial functional properties and whether such properties also display specific forms of plasticity still remain elusive. Here, we review research findings supporting this aspect of astrocytes, focusing on their roles in the clearance of extracellular potassium and glutamate, two neuroactive substances promptly released during excitatory synaptic transmission. Their subsequent removal, which is primarily carried out by glial potassium channels and glutamate transporters, is essential for proper functioning of the brain. Similar to neurons, different forms of short- and long-term plasticity in astroglial uptake have been reported. In addition, we also present novel findings showing robust potentiation of astrocytic inward currents in response to repetitive stimulations at mild frequencies, as low as 0.75 Hz, in acute hippocampal slices. Interestingly, neurotransmission was hardly affected at this frequency range, suggesting that astrocytes may be more sensitive to low frequency stimulation and may exhibit stronger plasticity than neurons to prevent hyperexcitability. Taken together, these important findings strongly indicate that astrocytes display both short- and long-term plasticity in their clearance of excess neuroactive substances from the extracellular space, thereby regulating neuronal activity and brain homeostasis. PMID:26346563

  15. Metabotropic glutamate receptors: their therapeutic potential in anxiety.

    PubMed

    Spooren, Will; Lesage, Anne; Lavreysen, Hilde; Gasparini, Fabrizio; Steckler, Thomas

    2010-01-01

    Psychiatric and neurological disorders are linked to changes in synaptic excitatory processes with a key role for glutamate, that is, the most abundant excitatory amino-acid. Molecular cloning of the metabotropic glutamate (mGlu) receptors has led to the identification of eight mGlu receptors, which, in contrast to ligand-gated ion channels (responsible for fast excitatory transmission), modulate and fine-tune the efficacy of synaptic transmission. mGlu receptors are G protein-coupled and constitute a new group of "drugable" targets for the treatment of various CNS disorders. The recent discovery of small molecules that selectively bind to receptors of Groups I (mGlu1 and mGlu5) and II (mGlu2 and mGlu3) allowed significant advances in our understanding of the roles of these receptors in brain function and dysfunction including anxiety. Although investigation of the role of the Group III (mGlu4, 6, 7, and 8) receptors is less advanced, the generation of genetically manipulated animals and recent advances in the identification of subtype-selective compounds have revealed some first insights into the therapeutic potential of this group of receptors. PMID:21309118

  16. Potentiation of Acetylcholine-Mediated Facilitation of Inhibitory Synaptic Transmission by an Azaindolizione Derivative, ZSET1446 (ST101), in the Rat Hippocampus.

    PubMed

    Takeda, Kentaro; Yamaguchi, Yoshimasa; Hino, Masataka; Kato, Fusao

    2016-02-01

    The integrity of the hippocampal network depends on the coordination of excitatory and inhibitory signaling, which are under dynamic control by various regulatory influences such as the cholinergic systems. ZSET1446 (ST101; spiro[imidazo[1,2-a]pyridine-3,2-indan]-2(3H)-one) is a newly synthesized azaindolizinone derivative that significantly improves learning deficits in various types of Alzheimer disease (AD) models in rats. We examined the effect of ZSET1446 on the nicotinic acetylcholine (ACh) receptor (nAChR)-mediated regulation of synaptic transmission in hippocampal slices of rats. ZSET1446 significantly potentiated the facilitatory effect of nicotine and ACh on the frequency of spontaneous postsynaptic currents (sPSCs) recorded in CA1 pyramidal neurons with a maximum effect at 100 pM (tested range, 10 pM-1000 pM). The basal sPSC frequency without ACh was not affected. Such potentiation by ZSET1446 was observed in both the pharmacologic isolations of inhibitory and excitatory sPSCs and markedly reduced by blockade of either α7 or α4β2 nAChRs. ZSET1446 did not affect ACh-activated inward currents or depolarization of interneurons in the stratum radiatum and the lacunosum moleculare. These results indicate that ZSET1446 potentiates the nicotine-mediated enhancement of synaptic transmission in the hippocampal neurons without affecting nAChRs themselves, providing a novel possible mechanism of procognitive action that might improve learning deficits in clinical therapy. PMID:26578264

  17. Amplification of neuromuscular transmission by methylprednisolone involves activation of presynaptic facilitatory adenosine A2A receptors and redistribution of synaptic vesicles.

    PubMed

    Oliveira, L; Costa, A C; Noronha-Matos, J B; Silva, I; Cavalcante, W L G; Timóteo, M A; Corrado, A P; Dal Belo, C A; Ambiel, C R; Alves-do-Prado, W; Correia-de-Sá, P

    2015-02-01

    The mechanisms underlying improvement of neuromuscular transmission deficits by glucocorticoids are still a matter of debate despite these compounds have been used for decades in the treatment of autoimmune myasthenic syndromes. Besides their immunosuppressive action, corticosteroids may directly facilitate transmitter release during high-frequency motor nerve activity. This effect coincides with the predominant adenosine A2A receptor tonus, which coordinates the interplay with other receptors (e.g. muscarinic) on motor nerve endings to sustain acetylcholine (ACh) release that is required to overcome tetanic neuromuscular depression in myasthenics. Using myographic recordings, measurements of evoked [(3)H]ACh release and real-time video microscopy with the FM4-64 fluorescent dye, results show that tonic activation of facilitatory A2A receptors by endogenous adenosine accumulated during 50 Hz bursts delivered to the rat phrenic nerve is essential for methylprednisolone (0.3 mM)-induced transmitter release facilitation, because its effect was prevented by the A2A receptor antagonist, ZM 241385 (10 nM). Concurrent activation of the positive feedback loop operated by pirenzepine-sensitive muscarinic M1 autoreceptors may also play a role, whereas the corticosteroid action is restrained by the activation of co-expressed inhibitory M2 and A1 receptors blocked by methoctramine (0.1 μM) and DPCPX (2.5 nM), respectively. Inhibition of FM4-64 loading (endocytosis) by methylprednisolone following a brief tetanic stimulus (50 Hz for 5 s) suggests that it may negatively modulate synaptic vesicle turnover, thus increasing the release probability of newly recycled vesicles. Interestingly, bulk endocytosis was rehabilitated when methylprednisolone was co-applied with ZM241385. Data suggest that amplification of neuromuscular transmission by methylprednisolone may involve activation of presynaptic facilitatory adenosine A2A receptors by endogenous adenosine leading to synaptic

  18. Baclofen and adenosine inhibition of synaptic transmission at CA3-CA1 synapses display differential sensitivity to K+ channel blockade.

    PubMed

    Skov, Jane; Andreasen, Mogens; Hablitz, John J; Nedergaard, Steen

    2011-05-01

    The metabotropic GABA(B) and adenosine A(1) receptors mediate presynaptic inhibition through regulation of voltage-dependent Ca(2+) channels, whereas K(+) channel regulation is believed to have no role at the CA3-CA1 synapse. We show here that the inhibitory effect of baclofen (20 μM) and adenosine (300 μM) on field EPSPs are differentially sensitive to Cs(+) (3.5 mM) and Ba(2+) (200 μM), but not 4-aminopyridine (100 μM). Barium had no effect on paired-pulse facilitation (PPF) in itself, but gave significant reduction (14 ± 5%) when applied in the presence of baclofen, but not adenosine, suggesting that the effect is presynaptic and selective on the GABA(B) receptor-mediated response. The effect of Ba(2+) on PPF was not mimicked by tertiapin (30 nM), indicating that the underlying mechanism does not involve GIRK channels. Barium did not affect PPF in slices from young rats (P7-P8), suggesting developmental regulation. The above effects of Ba(2+) on adult tissue were reproduced when measuring evoked whole-cell EPSCs from CA1 pyramidal neurons: PPF was reduced by 22 ± 3% in the presence of baclofen and unaltered in adenosine. In contrast, Ba(2+) caused no significant change in frequency or amplitude of miniature EPSCs. The Ba(2+)-induced reduction of PPF was antagonized by LY341495, suggesting metabotropic glutamate receptor involvement. We propose that these novel effects of Ba(2+) and Cs(+) are exerted through blockade of inwardly rectifying K(+) channels in glial cells, which are functionally interacting with the GABA(B) receptor-dependent glutamate release that generates heterosynaptic depression. PMID:21274618

  19. L-glutamate may be the fast excitatory transmitter of Aplysia sensory neurons.

    PubMed Central

    Dale, N; Kandel, E R

    1993-01-01

    Although modulation of synaptic transmission between Aplysia mechanosensory and motor neurons has been an important model for processes thought to underlie simple forms of learning and memory, the nature of the fast excitatory transmitter utilized by the sensory neurons has remained obscure. To identify the sensory neuron transmitter, we first examined the detailed properties of the synaptic response evoked in motor neurons cocultured with pleural sensory neurons. The excitatory postsynaptic current had a nonlinear current-voltage relation with a reversal potential between 0 and 10 mV and a plateau region between -40 and -70 mV. When the concentration of Mg2+ in the artificial sea water was lowered to 5 mM, the current-voltage relation of the excitatory postsynaptic current became linear, suggesting that Mg2+ blocks the postsynaptic receptor in a voltage-dependent manner. After screening a variety of small molecules, we found that L-glutamate could mimic the actions of the sensory neuron transmitter: responses to L-glutamate also had a reversal potential between 0 and 10 mV and a nonlinear current-voltage relation that could be made linear by lowering external Mg2+. To demonstrate further similarity of action between L-glutamate and the endogenous transmitter, we utilized four antagonists (kynurenate, 6,7-dinitroquinoxaline-2,3-dione, D-aspartate, and D-glutamate) to block in a dose-dependent manner the actions of L-glutamate and the natural transmitter. We therefore suggest that the sensory neurons use a glutamate-like transmitter and favor L-glutamate itself, because no other naturally occurring amino acid that we have studied has had similar actions. As the postsynaptic receptor for the sensory neuron transmitter is weakly blocked in a voltage-dependent manner by Mg2+, the excitatory receptors innervated by the Aplysia sensory neuron may represent a distant precursor of the vertebrate N-methyl-D-aspartate receptor. PMID:8102205

  20. Virtual leak channels modulate firing dynamics and synaptic integration in rat sympathetic neurons: implications for ganglionic transmission in vivo

    PubMed Central

    Springer, Mitchell G; Kullmann, Paul H M; Horn, John P

    2015-01-01

    Abstract The excitability of rat sympathetic neurons and integration of nicotinic EPSPs were compared in primary cell culture and in the acutely isolated intact superior cervical ganglion using whole cell patch electrode recordings. When repetitive firing was classified by Hodgkin's criteria in cultured cells, 18% displayed tonic class 1 excitability, 36% displayed adapting class 2 excitability and 46% displayed phasic class 3 excitability. In the intact ganglion, 71% of cells were class 1 and 29% were class 2. This diverges from microelectrode reports that nearly 100% of superior cervical ganglion neurons show phasic class 3 firing. The hypothesis that the disparity between patch and microelectrode data arises from a shunt conductance was tested using the dynamic clamp in cell culture. Non-depolarizing shunts of 3–10 nS converted cells from classes 1 and 2 to class 3 dynamics with current–voltage relations that replicated microelectrode data. Primary and secondary EPSPs recorded from the intact superior cervical ganglion were modelled as virtual synapses in cell culture using the dynamic clamp. Stimulating sympathetic neurons with virtual synaptic activity, designed to replicate in vivo recordings of EPSPs in muscle vasoconstrictor neurons, produced a 2.4-fold amplification of presynaptic activity. This gain in postsynaptic output did not differ between neurons displaying the three classes of excitability. Mimicry of microelectrode damage by virtual leak channels reduced and eventually obliterated synaptic gain by inhibiting summation of subthreshold EPSPs. These results provide a framework for interpreting sympathetic activity recorded from intact animals and support the hypothesis that paravertebral ganglia function as activity-dependent amplifiers of spinal output from preganglionic circuitry. PMID:25398531

  1. Prefrontal synaptic markers of cocaine addiction-like behavior in rats.

    PubMed

    Kasanetz, F; Lafourcade, M; Deroche-Gamonet, V; Revest, J-M; Berson, N; Balado, E; Fiancette, J-F; Renault, P; Piazza, P-V; Manzoni, O J

    2013-06-01

    Defining the drug-induced neuroadaptations specifically associated with the behavioral manifestation of addiction is a daunting task. To address this issue, we used a behavioral model that differentiates rats controlling their drug use (Non-Addict-like) from rats undergoing transition to addiction (Addict-like). Dysfunctions in prefrontal cortex (PFC) synaptic circuits are thought to be responsible for the loss of control over drug taking that characterizes addicted individuals. Here, we studied the synaptic alterations in prelimbic PFC (pPFC) circuits associated with transition to addiction. We discovered that some of the changes induced by cocaine self-administration (SA), such as the impairment of the endocannabinoid-mediated long-term synaptic depression (eCB-LTD) was similarly abolished in Non-Addict- and Addict-like rats and thus unrelated to transition to addiction. In contrast, metabotropic glutamate receptor 2/3-mediated LTD (mGluR2/3-LTD) was specifically suppressed in Addict-like rats, which also show a concomitant postsynaptic plasticity expressed as a change in the relative contribution of AMPAR and NMDAR to basal glutamate-mediated synaptic transmission. Addiction-associated synaptic alterations in the pPFC were not fully developed at early stages of cocaine SA, when addiction-like behaviors are still absent, suggesting that pathological behaviors appear once the pPFC is compromised. These data identify specific synaptic impairments in the pPFC associated with addiction and support the idea that alterations of synaptic plasticity are core markers of drug dependence. PMID:22584869

  2. Reverse optical trawling for synaptic connections in situ.

    PubMed

    Sasaki, Takuya; Minamisawa, Genki; Takahashi, Naoya; Matsuki, Norio; Ikegaya, Yuji

    2009-07-01

    We introduce a new method to unveil the network connectivity among dozens of neurons in brain slice preparations. While synaptic inputs were whole cell recorded from given postsynaptic neurons, the spatiotemporal firing patterns of presynaptic neuron candidates were monitored en masse with functional multineuron calcium imaging, an optical technique that records action potential-evoked somatic calcium transients with single-cell resolution. By statistically screening the neurons that exhibited calcium transients immediately before the postsynaptic inputs, we identified the presynaptic cells that made synaptic connections onto the patch-clamped neurons. To enhance the detection power, we devised the following points: 1) [K+]e was lowered and [Ca2+]e and [Mg2+]e were elevated, to reduce background synaptic activity and minimize the failure rate of synaptic transmission; and 2) a small fraction of presynaptic neurons was specifically activated by glutamate applied iontophoretically through a glass pipette that was moved to survey the presynaptic network of interest ("trawling"). Then we could theoretically detect 96% of presynaptic neurons activated in the imaged regions with a 1% false-positive error rate. This on-line probing technique would be a promising tool in the study of the wiring topography of neuronal circuits. PMID:19386760

  3. Methamphetamine blunts Ca(2+) currents and excitatory synaptic transmission through D1/5 receptor-mediated mechanisms in the mouse medial prefrontal cortex.

    PubMed

    González, Betina; Rivero-Echeto, Celeste; Muñiz, Javier A; Cadet, Jean Lud; García-Rill, Edgar; Urbano, Francisco J; Bisagno, Verónica

    2016-05-01

    Psychostimulant addiction is associated with dysfunctions in frontal cortex. Previous data demonstrated that repeated exposure to methamphetamine (METH) can alter prefrontal cortex (PFC)-dependent functions. Here, we show that withdrawal from repetitive non-contingent METH administration (7 days, 1 mg/kg) depressed voltage-dependent calcium currents (ICa ) and increased hyperpolarization-activated cation current (IH ) amplitude and the paired-pulse ratio of evoked excitatory postsynaptic currents (EPSCs) in deep-layer pyramidal mPFC neurons. Most of these effects were blocked by systemic co-administration of the D1/D5 receptor antagonist SCH23390 (0.5 and 0.05 mg/kg). In vitro METH (i.e. bath-applied to slices from naïve-treated animals) was able to emulate its systemic effects on ICa and evoked EPSCs paired-pulse ratio. We also provide evidence of altered mRNA expression of (1) voltage-gated calcium channels P/Q-type Cacna1a (Cav 2.1), N-type Cacna1b (Cav 2.2), T-type Cav 3.1 Cacna1g, Cav 3.2 Cacna1h, Cav 3.3 Cacna1i and the auxiliary subunit Cacna2d1 (α2δ1); (2) hyperpolarization-activated cyclic nucleotide-gated channels Hcn1 and Hcn2; and (3) glutamate receptors subunits AMPA-type Gria1, NMDA-type Grin1 and metabotropic Grm1 in the mouse mPFC after repeated METH treatment. Moreover, we show that some of these changes in mRNA expression were sensitive D1/5 receptor blockade. Altogether, these altered mechanisms affecting synaptic physiology and transcriptional regulation may underlie PFC functional alterations that could lead to PFC impairments observed in METH-addicted individuals. PMID:25871318

  4. Structure, Dynamics, and Allosteric Potential of Ionotropic Glutamate Receptor N-Terminal Domains

    PubMed Central

    Krieger, James; Bahar, Ivet; Greger, Ingo H.

    2015-01-01

    Ionotropic glutamate receptors (iGluRs) are tetrameric cation channels that mediate synaptic transmission and plasticity. They have a unique modular architecture with four domains: the intracellular C-terminal domain (CTD) that is involved in synaptic targeting, the transmembrane domain (TMD) that forms the ion channel, the membrane-proximal ligand-binding domain (LBD) that binds agonists such as L-glutamate, and the distal N-terminal domain (NTD), whose function is the least clear. The extracellular portion, comprised of the LBD and NTD, is loosely arranged, mediating complex allosteric regulation and providing a rich target for drug development. Here, we briefly review recent work on iGluR NTD structure and dynamics, and further explore the allosteric potential for the NTD in AMPA-type iGluRs using coarse-grained simulations. We also investigate mechanisms underlying the established NTD allostery in NMDA-type iGluRs, as well as the fold-related metabotropic glutamate and GABAB receptors. We show that the clamshell motions intrinsically favored by the NTD bilobate fold are coupled to dimeric and higher-order rearrangements that impact the iGluR LBD and ultimately the TMD. Finally, we explore the dynamics of intact iGluRs and describe how it might affect receptor operation in a synaptic environment. PMID:26255587

  5. Presynaptic kainate receptor facilitation of glutamate release involves protein kinase A in the rat hippocampus

    PubMed Central

    Rodríguez-Moreno, Antonio; Sihra, Talvinder S

    2004-01-01

    We have explored the mechanisms involved in the facilitation of glutamate release mediated by the activation of kainate receptors in the rat hippocampus using isolated nerve terminal (synaptosome) and slice preparations. In hippocampal nerve terminals, kainate (KA) produced an increase of glutamate release at concentrations of agonist ranging from 10 to 1000 μm. In hippocampal slices, KA at low nanomolar concentrations (20–50 nm) also produced an increase of evoked excitatory postsynaptic currents (eEPSCs) at mossy fibre–CA3 synapses. In both, synaptosomes and slices, the effect of KA was antagonized by CNQX, and persisted after pretreatment with a cocktail of antagonists for other receptors whose activation could potentially have produced facilitation of release. These data indicate that the facilitation of glutamate release observed is mediated by the activation of presynaptic glutamate receptors of the kainate type. Mechanistically, the observed effects of KA appear to be the same in synaptosomal and slice preparations. Thus, the effect of KA on glutamate release and mossy fibre–CA3 synaptic transmission was occluded by the stimulation of adenylyl cyclase by forskolin and suppressed by the inhibition of protein kinase A by H-89 or Rp-Br-cAMP. We conclude that kainate receptors present at presynaptic terminals in the rat hippocampus mediate the facilitation of glutamate release through a mechanism involving the activation of an adenylyl cyclase–second messenger cAMP–protein kinase A signalling cascade. PMID:15107475

  6. Different pools of glutamate receptors mediate sensitivity to ambient glutamate in the cochlear nucleus

    PubMed Central

    Yang, Yang

    2015-01-01

    Ambient glutamate plays an important role in pathological conditions, such as stroke, but its role during normal activity is not clear. In addition, it is not clear how ambient glutamate acts on glutamate receptors with varying affinities or subcellular localizations. To address this, we studied “endbulb of Held” synapses, which are formed by auditory nerve fibers onto bushy cells (BCs) in the anteroventral cochlear nucleus. When ambient glutamate was increased by applying the glutamate reuptake inhibitor TFB-TBOA, BCs depolarized as a result of activation of N-methyl-d-aspartate receptors (NMDARs) and group I metabotropic glutamate receptors (mGluRs). Application of antagonists against NMDARs (in 0 Mg2+) or mGluRs caused hyperpolarization, indicating that these receptors were bound by a tonic source of glutamate. AMPA receptors did not show these effects, consistent with their lower glutamate affinity. We also evaluated the subcellular localization of the receptors activated by ambient glutamate. The mGluRs were not activated by synaptic stimulation and thus appear to be exclusively extrasynaptic. By contrast, NMDARs in both synaptic and extrasynaptic compartments were activated by ambient glutamate, as shown using the use-dependent antagonist MK-801. Levels of ambient glutamate appeared to be regulated in a spike-independent manner, and glia likely play a major role. These low levels of ambient glutamate likely have functional consequences, as even low concentrations of TBOA caused significant increases in BC spiking following synaptic stimulation. These results indicate that normal resting potential appears to be poised in the region of maximal sensitivity to small changes in ambient glutamate. PMID:25855696

  7. Different pools of glutamate receptors mediate sensitivity to ambient glutamate in the cochlear nucleus.

    PubMed

    Yang, Yang; Xu-Friedman, Matthew A

    2015-06-01

    Ambient glutamate plays an important role in pathological conditions, such as stroke, but its role during normal activity is not clear. In addition, it is not clear how ambient glutamate acts on glutamate receptors with varying affinities or subcellular localizations. To address this, we studied "endbulb of Held" synapses, which are formed by auditory nerve fibers onto bushy cells (BCs) in the anteroventral cochlear nucleus. When ambient glutamate was increased by applying the glutamate reuptake inhibitor TFB-TBOA, BCs depolarized as a result of activation of N-methyl-D-aspartate receptors (NMDARs) and group I metabotropic glutamate receptors (mGluRs). Application of antagonists against NMDARs (in 0 Mg(2+)) or mGluRs caused hyperpolarization, indicating that these receptors were bound by a tonic source of glutamate. AMPA receptors did not show these effects, consistent with their lower glutamate affinity. We also evaluated the subcellular localization of the receptors activated by ambient glutamate. The mGluRs were not activated by synaptic stimulation and thus appear to be exclusively extrasynaptic. By contrast, NMDARs in both synaptic and extrasynaptic compartments were activated by ambient glutamate, as shown using the use-dependent antagonist MK-801. Levels of ambient glutamate appeared to be regulated in a spike-independent manner, and glia likely play a major role. These low levels of ambient glutamate likely have functional consequences, as even low concentrations of TBOA caused significant increases in BC spiking following synaptic stimulation. These results indicate that normal resting potential appears to be poised in the region of maximal sensitivity to small changes in ambient glutamate. PMID:25855696

  8. Prodomain Removal Enables Neto to Stabilize Glutamate Receptors at the Drosophila Neuromuscular Junction

    PubMed Central

    Kim, Young-Jun; Igiesuorobo, Oghomwen; Ramos, Cathy I.; Bao, Hong; Zhang, Bing; Serpe, Mihaela

    2015-01-01

    Stabilization of neurotransmitter receptors at postsynaptic specializations is a key step in the assembly of functional synapses. Drosophila Neto (Neuropillin and Tolloid-like protein) is an essential auxiliary subunit of ionotropic glutamate receptor (iGluR) complexes required for the iGluRs clustering at the neuromuscular junction (NMJ). Here we show that optimal levels of Neto are crucial for stabilization of iGluRs at synaptic sites and proper NMJ development. Genetic manipulations of Neto levels shifted iGluRs distribution to extrajunctional locations. Perturbations in Neto levels also produced small NMJs with reduced synaptic transmission, but only Neto-depleted NMJs showed diminished postsynaptic components. Drosophila Neto contains an inhibitory prodomain that is processed by Furin1-mediated limited proteolysis. neto null mutants rescued with a Neto variant that cannot be processed have severely impaired NMJs and reduced iGluRs synaptic clusters. Unprocessed Neto retains the ability to engage iGluRs in vivo and to form complexes with normal synaptic transmission. However, Neto prodomain must be removed to enable iGluRs synaptic stabilization and proper postsynaptic differentiation. PMID:25723514

  9. Neuronal MHC Class I Molecules are Involved in Excitatory Synaptic Transmission at the Hippocampal Mossy Fiber Synapses of Marmoset Monkeys

    PubMed Central

    Zhang, Mingyue; Schlumbohm, Christina; Mätz-Rensing, Kerstin; Uchanska-Ziegler, Barbara; Flügge, Gabriele; Zhang, Weiqi; Walter, Lutz; Fuchs, Eberhard

    2010-01-01

    Several recent studies suggested a role for neuronal major histocompatibility complex class I (MHCI) molecules in certain forms of synaptic plasticity in the hippocampus of rodents. Here, we report for the first time on the expression pattern and functional properties of MHCI molecules in the hippocampus of a nonhuman primate, the common marmoset monkey (Callithrix jacchus). We detected a presynaptic, mossy fiber-specific localization of MHCI proteins within the marmoset hippocampus. MHCI molecules were present in the large, VGlut1-positive, mossy fiber terminals, which provide input to CA3 pyramidal neurons. Furthermore, whole-cell recordings of CA3 pyramidal neurons in acute hippocampal slices of the common marmoset demonstrated that application of antibodies which specifically block MHCI proteins caused a significant decrease in the frequency, and a transient increase in the amplitude, of spontaneous excitatory postsynaptic currents (sEPSCs) in CA3 pyramidal neurons. These findings add to previous studies on neuronal MHCI molecules by describing their expression and localization in the primate hippocampus and by implicating them in plasticity-related processes at the mossy fiber–CA3 synapses. In addition, our results suggest significant interspecies differences in the localization of neuronal MHCI molecules in the hippocampus of mice and marmosets, as well as in their potential function in these species. Electronic supplementary material The online version of this article (doi:10.1007/s10571-010-9510-3) contains supplementary material, which is available to authorized users. PMID:20232136

  10. DEEP BRAIN STIMULATION IN MIDLINE THALAMIC REGION FACILITATES SYNAPTIC TRANSMISSION AND SHORTTERM MEMORY IN A MOUSE MODEL OF ALZHEIMER'S DISEASE.

    PubMed

    Arrieta-Cruz, Isabel; Pavlides, Constantine; Pasinetti, Giulio Maria

    2010-09-01

    Based on evidence suggesting that deep brain stimulation (DBS) may promote certain cognitive processes, we have been interested in developing DBS as a means of mitigating memory and learning impairments in Alzheimer's disease (AD). In this study we used an animal model of AD (TgCRND8 mice) to determine the effects of high-frequency stimulation (HFS) on non-amyloidogenic α-secretase activity and DBS in short-term memory. We tested our hypothesis using hippocampal slices (in vitro studies) from TgCRND8 mice to evaluate whether HFS increases α-secretase activity (non-amyloidogenic pathway) in the CA1 region. In a second set of experiments, we performed in vivo studies to evaluate whether DBS in midline thalamic region re-establishes hippocampal dependent short-term memory in TgCRND8 mice. The results showed that application of HFS to isolated hippocampal slices significantly increased synaptic plasticity in the CA1 region and promoted a 2-fold increase of non-amyloidogenic α-secretase activity, in comparison to low frequency stimulated controls from TgCRND8 mice. In the in vivo studies, DBS treatment facilitated acquisition of object recognition memory in TgCRND8 mice, in comparison to their own baseline before treatment. These results provide evidence that DBS could enhance short-term memory in the CA1 region of hippocampus in a mouse model of AD. PMID:23227306

  11. Neuronal activity mediated regulation of glutamate transporter GLT-1 surface diffusion in rat astrocytes in dissociated and slice cultures.

    PubMed

    Al Awabdh, Sana; Gupta-Agarwal, Swati; Sheehan, David F; Muir, James; Norkett, Rosalind; Twelvetrees, Alison E; Griffin, Lewis D; Kittler, Josef T

    2016-07-01

    The astrocytic GLT-1 (or EAAT2) is the major glutamate transporter for clearing synaptic glutamate. While the diffusion dynamics of neurotransmitter receptors at the neuronal surface are well understood, far less is known regarding the surface trafficking of transporters in subcellular domains of the astrocyte membrane. Here, we have used live-cell imaging to study the mechanisms regulating GLT-1 surface diffusion in astrocytes in dissociated and brain slice cultures. Using GFP-time lapse imaging, we show that GLT-1 forms stable clusters that are dispersed rapidly and reversibly upon glutamate treatment in a transporter activity-dependent manner. Fluorescence recovery after photobleaching and single particle tracking using quantum dots revealed that clustered GLT-1 is more stable than diffuse GLT-1 and that glutamate increases GLT-1 surface diffusion in the astrocyte membrane. Interestingly, the two main GLT-1 isoforms expressed in the brain, GLT-1a and GLT-1b, are both found to be stabilized opposed to synapses under basal conditions, with GLT-1b more so. GLT-1 surface mobility is increased in proximity to activated synapses and alterations of neuronal activity can bidirectionally modulate the dynamics of both GLT-1 isoforms. Altogether, these data reveal that astrocytic GLT-1 surface mobility, via its transport activity, is modulated during neuronal firing, which may be a key process for shaping glutamate clearance and glutamatergic synaptic transmission. GLIA 2016;64:1252-1264. PMID:27189737

  12. Neuronal activity mediated regulation of glutamate transporter GLT‐1 surface diffusion in rat astrocytes in dissociated and slice cultures

    PubMed Central

    Al Awabdh, Sana; Gupta‐Agarwal, Swati; Sheehan, David F.; Muir, James; Norkett, Rosalind; Twelvetrees, Alison E.; Griffin, Lewis D.

    2016-01-01

    The astrocytic GLT‐1 (or EAAT2) is the major glutamate transporter for clearing synaptic glutamate. While the diffusion dynamics of neurotransmitter receptors at the neuronal surface are well understood, far less is known regarding the surface trafficking of transporters in subcellular domains of the astrocyte membrane. Here, we have used live‐cell imaging to study the mechanisms regulating GLT‐1 surface diffusion in astrocytes in dissociated and brain slice cultures. Using GFP‐time lapse imaging, we show that GLT‐1 forms stable clusters that are dispersed rapidly and reversibly upon glutamate treatment in a transporter activity‐dependent manner. Fluorescence recovery after photobleaching and single particle tracking using quantum dots revealed that clustered GLT‐1 is more stable than diffuse GLT‐1 and that glutamate increases GLT‐1 surface diffusion in the astrocyte membrane. Interestingly, the two main GLT‐1 isoforms expressed in the brain, GLT‐1a and GLT‐1b, are both found to be stabilized opposed to synapses under basal conditions, with GLT‐1b more so. GLT‐1 surface mobility is increased in proximity to activated synapses and alterations of neuronal activity can bidirectionally modulate the dynamics of both GLT‐1 isoforms. Altogether, these data reveal that astrocytic GLT‐1 surface mobility, via its transport activity, is modulated during neuronal firing, which may be a key process for shaping glutamate clearance and glutamatergic synaptic transmission. GLIA 2016;64:1252–1264 PMID:27189737

  13. Inhibitory effects of endomorphin-2 on excitatory synaptic transmission and the neuronal excitability of sacral parasympathetic preganglionic neurons in young rats

    PubMed Central

    Chen, Ying-Biao; Huang, Fen-Sheng; Fen, Ban; Yin, Jun-Bin; Wang, Wei; Li, Yun-Qing

    2015-01-01

    The function of the urinary bladder is partly controlled by parasympathetic preganglionic neurons (PPNs) of the sacral parasympathetic nucleus (SPN). Our recent work demonstrated that endomorphin-2 (EM-2)-immunoreactive (IR) terminals form synapses with μ-opioid receptor (MOR)-expressing PPNs in the rat SPN. Here, we examined the effects of EM-2 on excitatory synaptic transmission and the neuronal excitability of the PPNs in young rats (24–30 days old) using a whole-cell patch-clamp approach. PPNs were identified by retrograde labeling with the fluorescent tracer tetramethylrhodamine-dextran (TMR). EM-2 (3 μM) markedly decreased both the amplitude and the frequency of the spontaneous and miniature excitatory postsynaptic currents (sEPSCs and mEPSCs) of PPNs. EM-2 not only decreased the resting membrane potentials (RMPs) in 61.1% of the examined PPNs with half-maximal response at the concentration of 0.282 μM, but also increased the rheobase current and reduced the repetitive action potential firing of PPNs. Analysis of the current–voltage relationship revealed that the EM-2-induced current was reversed at −95 ± 2.5 mV and was suppressed by perfusion of the potassium channel blockers 4-aminopyridine (4-AP) or BaCl2 or by the addition of guanosine 5′-[β-thio]diphosphate trilithium salt (GDP-β-S) to the pipette solution, suggesting the involvement of the G-protein-coupled inwardly rectifying potassium (GIRK) channel. The above EM-2-invoked inhibitory effects were abolished by the MOR selective antagonist D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2 (CTOP), indicating that the effects of EM-2 on PPNs were mediated by MOR via pre- and/or post-synaptic mechanisms. EM-2 activated pre- and post-synaptic MORs, inhibiting excitatory neurotransmitter release from the presynaptic terminals and decreasing the excitability of PPNs due to hyperpolarization of their membrane potentials, respectively. These inhibitory effects of EM-2 on PPNs at the spinal cord level may

  14. Inhibitory effects of endomorphin-2 on excitatory synaptic transmission and the neuronal excitability of sacral parasympathetic preganglionic neurons in young rats.

    PubMed

    Chen, Ying-Biao; Huang, Fen-Sheng; Fen, Ban; Yin, Jun-Bin; Wang, Wei; Li, Yun-Qing

    2015-01-01

    The function of the urinary bladder is partly controlled by parasympathetic preganglionic neurons (PPNs) of the sacral parasympathetic nucleus (SPN). Our recent work demonstrated that endomorphin-2 (EM-2)-immunoreactive (IR) terminals form synapses with μ-opioid receptor (MOR)-expressing PPNs in the rat SPN. Here, we examined the effects of EM-2 on excitatory synaptic transmission and the neuronal excitability of the PPNs in young rats (24-30 days old) using a whole-cell patch-clamp approach. PPNs were identified by retrograde labeling with the fluorescent tracer tetramethylrhodamine-dextran (TMR). EM-2 (3 μM) markedly decreased both the amplitude and the frequency of the spontaneous and miniature excitatory postsynaptic currents (sEPSCs and mEPSCs) of PPNs. EM-2 not only decreased the resting membrane potentials (RMPs) in 61.1% of the examined PPNs with half-maximal response at the concentration of 0.282 μM, but also increased the rheobase current and reduced the repetitive action potential firing of PPNs. Analysis of the current-voltage relationship revealed that the EM-2-induced current was reversed at -95 ± 2.5 mV and was suppressed by perfusion of the potassium channel blockers 4-aminopyridine (4-AP) or BaCl2 or by the addition of guanosine 5'-[β-thio]diphosphate trilithium salt (GDP-β-S) to the pipette solution, suggesting the involvement of the G-protein-coupled inwardly rectifying potassium (GIRK) channel. The above EM-2-invoked inhibitory effects were abolished by the MOR selective antagonist D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2 (CTOP), indicating that the effects of EM-2 on PPNs were mediated by MOR via pre- and/or post-synaptic mechanisms. EM-2 activated pre- and post-synaptic MORs, inhibiting excitatory neurotransmitter release from the presynaptic terminals and decreasing the excitability of PPNs due to hyperpolarization of their membrane potentials, respectively. These inhibitory effects of EM-2 on PPNs at the spinal cord level may explain

  15. Effects of familial hemiplegic migraine type 1 mutations on neuronal P/Q-type Ca2+ channel activity and inhibitory synaptic transmission

    PubMed Central

    Cao, Yu-Qing; Tsien, Richard W.

    2005-01-01

    Inhibitory synapses play key roles in the modulatory circuitry that regulates pain signaling and generation of migraine headache. A rare, dominant form of this common disease, familial hemiplegic migraine type 1 (FHM1), arises from missense mutations in the pore-forming α1A subunit of P/Q-type Ca2+ channels. These channels are normally vital for presynaptic Ca2+ entry and neurotransmitter release at many central synapses, raising questions about effects of FHM1 mutations on neuronal Ca2+ influx and inhibitory and excitatory neurotransmission. We have expressed the four original FHM1 mutant channels in hippocampal neurons from α1A knockout mice. Whole-cell recordings indicated that FHM1 mutant channels were less effective than wild-type channels in their ability to conduct P/Q-type current, but not generally different from wild type in voltage-dependent channel gating. Ca2+ influx triggered by action potential waveforms was also diminished. In keeping with decreased channel activity, FHM1 mutant channels were correspondingly impaired in supporting the P/Q-type component of inhibitory neurotransmission. When expressed in wild-type inhibitory neurons, FHM1 mutant channels reduced the contribution of P/Q-type channels to GABAergic synaptic currents, consistent with a competition of mutant and endogenous channels for P/Q-specific slots. In all cases, N-type channels took up the burden of supporting transmission and homeostatic mechanisms maintained overall synaptic strength. The shift to reliance on N-type channels greatly increased the susceptibility to G protein-coupled modulation of neurotransmission, studied with the GABAB agonist baclofen. Thus, mutant-expressing synapses might be weakened in a heightened state of neuromodulation like that provoked by triggers of migraine such as stress. PMID:15699344

  16. Glutamate Receptor Stimulation Up-Regulates Glutamate Uptake in Human Müller Glia Cells.

    PubMed

    López-Colomé, Ana María; López, Edith; Mendez-Flores, Orquidia G; Ortega, Arturo

    2016-07-01

    Glutamate, the main excitatory amino acid in the vertebrate retina, is a well know activator of numerous signal transduction pathways, and has been critically involved in long-term synaptic changes acting through ionotropic and metabotropic glutamate receptors. However, recent findings underlining the importance of intensity and duration of glutamate stimuli for specific neuronal responses, including excitotoxicity, suggest a crucial role for Na(+)-dependent glutamate transporters, responsible for the removal of this neurotransmitter from the synaptic cleft, in the regulation of glutamate-induced signaling. Transporter proteins are expressed in neurons and glia cells, albeit most of glutamate uptake occurs in the glial compartment. Within the retina, Müller glia cells are in close proximity to glutamatergic synapses and participate in the recycling of glutamate through the glutamate/glutamine shuttle. In this context, we decided to investigate a plausible role of glutamate as a regulatory signal for its own transport in human retinal glia cells. To this end, we determined [(3)H]-D-aspartate uptake in cultures of spontaneously immortalized human Müller cells (MIO-M1) exposed to distinct glutamatergic ligands. A time and dose-dependent increase in the transporter activity was detected. This effect was dependent on the activation of the N-methyl D-aspartate subtype of glutamate receptors, due to a dual effect: an increase in affinity and an augmented expression of the transporter at the plasma membrane, as established via biotinylation experiments. Furthermore, a NMDA-dependent association of glutamate transporters with the cystoskeletal proteins ezrin and glial fibrillary acidic protein was also found. These results add a novel mediator of the glutamate transporter modulation and further strengthen the notion of the critical involvement of glia cells in synaptic function. PMID:27017513

  17. Familial hemiplegic migraine type-1 mutated cav2.1 calcium channels alter inhibitory and excitatory synaptic transmission in the lateral superior olive of mice.

    PubMed

    Inchauspe, Carlota González; Pilati, Nadia; Di Guilmi, Mariano N; Urbano, Francisco J; Ferrari, Michel D; van den Maagdenberg, Arn M J M; Forsythe, Ian D; Uchitel, Osvaldo D

    2015-01-01

    CaV2.1 Ca(2+) channels play a key role in triggering neurotransmitter release and mediating synaptic transmission. Familial hemiplegic migraine type-1 (FHM-1) is caused by missense mutations in the CACNA1A gene that encodes the α1A pore-forming subunit of CaV2.1 Ca(2+) channels. We used knock-in (KI) transgenic mice harbouring the pathogenic FHM-1 mutation R192Q to study inhibitory and excitatory neurotransmission in the principle neurons of the lateral superior olive (LSO) in the auditory brainstem. We tested if the R192Q FHM-1 mutation differentially affects excitatory and inhibitory synaptic transmission, disturbing the normal balance between excitation and inhibition in this nucleus. Whole cell patch-clamp was used to measure neurotransmitter elicited excitatory (EPSCs) and inhibitory (IPSCs) postsynaptic currents in wild-type (WT) and R192Q KI mice. Our results showed that the FHM-1 mutation in CaV2.1 channels has multiple effects. Evoked EPSC amplitudes were smaller whereas evoked and miniature IPSC amplitudes were larger in R192Q KI compared to WT mice. In addition, in R192Q KI mice, the release probability was enhanced compared to WT, at both inhibitory (0.53 ± 0.02 vs. 0.44 ± 0.01, P = 2.10(-5), Student's t-test) and excitatory synapses (0.60 ± 0.03 vs. 0.45 ± 0.02, P = 4 10(-6), Student's t-test). Vesicle pool size was diminished in R192Q KI mice compared to WT mice (68 ± 6 vs 91 ± 7, P = 0.008, inhibitory; 104 ± 13 vs 335 ± 30, P = 10(-6), excitatory, Student's t-test). R192Q KI mice present enhanced short-term plasticity. Repetitive stimulation of the afferent axons caused short-term depression (STD) of E/IPSCs that recovered significantly faster in R192Q KI mice compared to WT. This supports the hypothesis of a gain-of-function of the CaV2.1 channels in R192Q KI mice, which alters the balance of excitatory/inhibitory inputs and could also have implications in the altered cortical excitability responsible for FHM

  18. Abnormal glutamate release in aged BTBR mouse model of autism

    PubMed Central

    Wei, Hongen; Ding, Caiyun; Jin, Guorong; Yin, Haizhen; Liu, Jianrong; Hu, Fengyun

    2015-01-01

    Autism is a neurodevelopmental disorder characterized by abnormal reciprocal social interactions, communication deficits, and repetitive behaviors with restricted interests. Most of the available research on autism is focused on children and young adults and little is known about the pathological alternation of autism in older adults. In order to investigate the neurobiological alternation of autism in old age stage, we compared the morphology and synaptic function of excitatory synapses between the BTBR mice with low level sociability and B6 mice with high level sociability. The results revealed that the number of excitatory synapse colocalized with pre- and post-synaptic marker was not different between aged BTBR and B6 mice. The aged BTBR mice had a normal structure of dendritic spine and the expression of Shank3 protein in the brain as well as that in B6 mice. The baseline and KCl-evoked glutamate release from the cortical synaptoneurosome in aged BTBR mice was lower than that in aged B6 mice. Overall, the data indicate that there is a link between disturbances of the glutamate transmission and autism. These findings provide new evidences for the hypothesis of excitation/inhibition imbalance in autism. Further work is required to determine the cause of this putative abnormality. PMID:26617779

  19. Metabotropic Glutamate Receptor Dependent Cortical Plasticity in Chronic Pain.

    PubMed

    Koga, Kohei; Li, Shermaine; Zhuo, Min

    2016-01-01

    Many cortical areas play crucial roles in higher order brain functions such as pain and emotion-processing, decision-making, and cognition. Among them, anterior cingulate cortex (ACC) and insular cortex (IC) are two key areas. Glutamate mediates major excitatory transmission during long-term plasticity in both physiological and pathological conditions. Specifically related to nociceptive or pain behaviors, metabotropic glutamate subtype receptors (mGluRs) have been involved in different types of synaptic modulation and plasticity from periphery to the spinal cord. However, less is known about their functional roles in plasticity related to pain and its related behaviors within cortical regions. In this review, we first summarized previous studies of synaptic plasticity in both the ACC and IC, and discussed how mGluRs may be involved in both cortical long-term potentiation (LTP) and long-term depression (LTD)-especially in LTD. The activation of mGluRs contributes to the induction of LTD in both ACC and IC areas. The loss of LTD caused by peripheral amputation or nerve injury can be rescued by priming ACC or IC with activations of mGluR1 receptors. We also discussed the potential functional roles of mGluRs for pain-related behaviors. We propose that targeting mGluRs in the cortical areas including the ACC and IC may provide a new therapeutic strategy for the treatment of chronic pain, phantom pain or anxiety. PMID:27296638

  20. The dose makes the poison: from glutamate-mediated neurogenesis to neuronal atrophy and depression.

    PubMed

    Rubio-Casillas, Alberto; Fernández-Guasti, Alonso

    2016-08-01

    Experimental evidence has demonstrated that glutamate is an essential factor for neurogenesis, whereas another line of research postulates that excessive glutamatergic neurotransmission is associated with the pathogenesis of depression. The present review shows that such paradox can be explained within the framework of hormesis, defined as biphasic dose responses. Low glutamate levels activate adaptive stress responses that include proteins that protect neurons against more severe stress. Conversely, abnormally high levels of glutamate, resulting from increased release and/or decreased removal, cause neuronal atrophy and depression. The dysregulation of the glutamatergic transmission in depression could be underlined by several factors including a decreased inhibition (γ-aminobutyric acid or serotonin) or an increased excitation (primarily within the glutamatergic system). Experimental evidence shows that the activation of N-methyl-D-aspartate receptor (NMDA) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors (AMPAR) can exert two opposite effects on neurogenesis and neuron survival depending on the synaptic or extrasynaptic concentration. Chronic stress, which usually underlies experimental and clinical depression, enhances glutamate release. This overactivates NMDA receptors (NMDAR) and consequently impairs AMPAR activity. Various studies show that treatment with antidepressants decreases plasma glutamate levels in depressed individuals and regulates glutamate receptors by reducing NMDAR function by decreasing the expression of its subunits and by potentiating AMPAR-mediated transmission. Additionally, it has been shown that chronic treatment with antidepressants having divergent mechanisms of action (including tricyclics, selective serotonin reuptake inhibitors, and ketamine) markedly reduced depolarization-evoked glutamate release in the hippocampus. These data, taken together, suggest that the glutamatergic system could be a final

  1. Limiting glutamate transmission in a Vglut2-expressing subpopulation of the subthalamic nucleus is sufficient to cause hyperlocomotion

    PubMed Central

    Schweizer, Nadine; Pupe, Stéfano; Arvidsson, Emma; Nordenankar, Karin; Smith-Anttila, Casey J. A.; Mahmoudi, Souha; Andrén, Anna; Dumas, Sylvie; Rajagopalan, Aparna; Lévesque, Daniel; Leão, Richardson N.; Wallén-Mackenzie, Åsa

    2014-01-01

    The subthalamic nucleus (STN) is a key area of the basal ganglia circuitry regulating movement. We identified a subpopulation of neurons within this structure that coexpresses Vglut2 and Pitx2, and by conditional targeting of this subpopulation we reduced Vglut2 expression levels in the STN by 40%, leaving Pitx2 expression intact. This reduction diminished, yet did not eliminate, glutamatergic transmission in the substantia nigra pars reticulata and entopeduncular nucleus, two major targets of the STN. The knockout mice displayed hyperlocomotion and decreased latency in the initiation of movement while preserving normal gait and balance. Spatial cognition, social function, and level of impulsive choice also remained undisturbed. Furthermore, these mice showed reduced dopamine transporter binding and slower dopamine clearance in vivo, suggesting that Vglut2-expressing cells in the STN regulate dopaminergic transmission. Our results demonstrate that altering the contribution of a limited population within the STN is sufficient to achieve results similar to STN lesions and high-frequency stimulation, but with fewer side effects. PMID:24821804

  2. Balance and stability of synaptic structures during synaptic plasticity.

    PubMed

    Meyer, Daniel; Bonhoeffer, Tobias; Scheuss, Volker

    2014-04-16

    Subsynaptic structures such as bouton, active zone, postsynaptic density (PSD) and dendritic spine, are highly correlated in their dimensions and also correlate with synapse strength. Why this is so and how such correlations are maintained during synaptic plasticity remains poorly understood. We induced spine enlargement by two-photon glutamate uncaging and examined the relationship between spine, PSD, and bouton size by two-photon time-lapse imaging and electron microscopy. In enlarged spines the PSD-associated protein Homer1c increased rapidly, whereas the PSD protein PSD-95 increased with a delay and only in cases of persistent spine enlargement. In the case of nonpersistent spine enlargement, the PSD proteins remained unchanged or returned to their original level. The ultrastructure at persistently enlarged spines displayed matching dimensions of spine, PSD, and bouton, indicating their correlated enlargement. This supports a model in which balancing of synaptic structures is a hallmark for the stabilization of structural modifications during synaptic plasticity. PMID:24742464

  3. Microbial Rhodopsin Optogenetic Tools: Application for Analyses of Synaptic Transmission and of Neuronal Network Activity in Behavior.

    PubMed

    Glock, Caspar; Nagpal, Jatin; Gottschalk, Alexander

    2015-01-01

    Optogenetics was introduced as a new technology in the neurosciences about a decade ago (Zemelman et al., Neuron 33:15-22, 2002; Boyden et al., Nat Neurosci 8:1263-1268, 2005; Nagel et al., Curr Biol 15:2279-2284, 2005; Zemelman et al., Proc Natl Acad Sci USA 100:1352-1357, 2003). It combines optics, genetics, and bioengineering to render neurons sensitive to light, in order to achieve a precise, exogenous, and noninvasive control of membrane potential, intracellular signaling, network activity, or behavior (Rein and Deussing, Mol Genet Genomics 287:95-109, 2012; Yizhar et al., Neuron 71:9-34, 2011). As C. elegans is transparent, genetically amenable, has a small nervous system mapped with synapse resolution, and exhibits a rich behavioral repertoire, it is especially open to optogenetic methods (White et al., Philos Trans R Soc Lond B Biol Sci 314:1-340, 1986; De Bono et al., Optogenetic actuation, inhibition, modulation and readout for neuronal networks generating behavior in the nematode Caenorhabditis elegans, In: Hegemann P, Sigrist SJ (eds) Optogenetics, De Gruyter, Berlin, 2013; Husson et al., Biol Cell 105:235-250, 2013; Xu and Kim, Nat Rev Genet 12:793-801, 2011). Optogenetics, by now an "exploding" field, comprises a repertoire of different tools ranging from transgenically expressed photo-sensor proteins (Boyden et al., Nat Neurosci 8:1263-1268, 2005; Nagel et al., Curr Biol 15:2279-2284, 2005) or cascades (Zemelman et al., Neuron 33:15-22, 2002) to chemical biology approaches, using photochromic ligands of endogenous channels (Szobota et al., Neuron 54:535-545, 2007). Here, we will focus only on optogenetics utilizing microbial rhodopsins, as these are most easily and most widely applied in C. elegans. For other optogenetic tools, for example the photoactivated adenylyl cyclases (PACs, that drive neuronal activity by increasing synaptic vesicle priming, thus exaggerating rather than overriding the intrinsic activity of a neuron, as occurs with

  4. Pharmacological inhibitions of glutamate transporters EAAT1 and EAAT2 compromise glutamate transport in photoreceptor to ON- bipolar cell synapses

    PubMed Central

    Tse, Dennis Y.; Chung, Inyoung; Wu, Samuel M.

    2015-01-01

    To maintain reliable signal transmission across a synapse, free synaptic neurotransmitters must be removed from the cleft in a timely manner. In the first visual synapse, this critical task is mainly undertaken by glutamate transporters (EAATs). Here we study the differential roles of the EAAT1, EAAT2 and EAAT5 subtypes in glutamate (GLU) uptake at the photoreceptor-to-depolarizing bipolar cell synapse in intact dark-adapted retina. Various doses of EAAT blockers and/or GLU were injected into the eye before the electroretinogram (ERG) was measured. Their effectiveness and potency in inhibiting the ERG b-wave were studied to determine their relative contributions to the GLU clearing activity at the synapse. The results showed that EAAT1 and EAAT2 plays different roles. Selectively blocking glial EAAT1 alone using UCPH101 inhibited the b-wave 2–24 hours following injection, suggesting a dominating role of EAAT1 in the overall GLU clearing capacity in the synaptic cleft. Selectively blocking EAAT2 on photoreceptor terminals had no significant effect on the b-wave, but increased the potency of exogenous GLU in inhibiting the b-wave. These suggest that EAAT2 play a secondary yet significant role in the GLU reuptake activity at the rod and the cone output synapses. Additionally, we have verified our electrophysiological findings with double-label immunohistochemistry, and extend the literature on the spatial distribution of EAAT2 splice variants in the mouse retina. PMID:25152321

  5. Glutamate release in the nucleus accumbens core is necessary for heroin seeking.

    PubMed

    LaLumiere, Ryan T; Kalivas, Peter W

    2008-03-19

    Long-term changes in glutamate transmission in the nucleus accumbens core (NAcore) contribute to the reinstatement of drug seeking after extinction of cocaine self-administration. Whether similar adaptations in glutamate transmission occur during heroin and cue-induced reinstatement of heroin seeking is unknown. After 2 weeks of heroin self-administration and 2 weeks of subsequent extinction training, heroin seeking was induced by a noncontingent injection of heroin or by presentation of light/tone cues previously paired with heroin infusions. Microdialysis was conducted in the NAcore during reinstatement of heroin seeking in animals extinguished from heroin self-administration or in subjects receiving parallel (yoked) noncontingent saline or heroin. Reinstatement by either heroin or cue increased extracellular glutamate in the NAcore in the self-administration group, but no increase was elicited during heroin-induced reinstatement in the yoked control groups. The increase in glutamate during heroin-induced drug seeking was abolished by inhibiting synaptic transmission in the NAcore with tetrodotoxin or by inhibiting glutamatergic afferents to the NAcore from the prelimbic cortex. Supporting critical involvement of glutamate release, heroin seeking induced by cue or heroin was blocked by inhibiting AMPA/kainate glutamate receptors in the NAcore. Interestingly, although a heroin-priming injection increased dopamine equally in animals trained to self-administer heroin and in yoked-saline subjects, inhibition of dopamine receptors in the NAcore also blocked heroin- and cue-induced drug seeking. Together, these findings show that recruitment of the glutamatergic projection from the prelimbic cortex to NAcore is necessary to initiate the reinstatement of heroin seeking. PMID:18354020

  6. L-glutamate detection using a poly-L-lysine coated ENFET

    NASA Astrophysics Data System (ADS)

    Braeken, D.; Zhou, C.; Huys, R.; Bartic, C.; De Keersmaecker, K.; Winters, K.; Callewaert, G.; Borghs, G.

    2005-06-01

    Synaptic transmission in neuronal networks occur on a very short time scale and is highly specific. Fast, sensitive and in situ detection of single neuron L-glutamate release is essential for the investigation of these events under physiological or pathophysiological conditions. Up till now, amperometry with enzyme-modified electrodes has extensively been used to monitor extracellular glutamate release. However, due to in situ signal amplification, ENzyme-modified Field-Effect Transistors (ENFETs) have the advantage of preserving sensitivity and a fast response time when scaled down to micrometer dimensions. We have realized a L-GLutamate OxiDase (GLOD) functionalized FET to be used for glutamate detection in neuronal cultures. Effective and reproducible immobilization of GLOD on the FET active area is achieved by using Poly-L-Lysine (PLL) as a loading matrix. PLL plays a dual role in the assay: on the one hand this molecule serves as a platform for obtaining high enzyme loading and on the other hand it benefits the survival of the neuronal network on the active area of the FET. Both PLL and enzyme immobilization were characterised by quartz crystal microbalance measurements. A much higher enzyme loading has been achieved by this approach compared to immobilization methods without PLL. The enzyme coating has proven to be extremely durable as it keeps its activity for at least 3 weeks as monitored by a colorimetric assay. FET characterisation curves and glutamate response curves of the ENFET are presented.

  7. Modulation of gamma-aminobutyric acid-mediated inhibitory synaptic currents in dissociated cortical cell cultures.

    PubMed Central

    Vicini, S; Alho, H; Costa, E; Mienville, J M; Santi, M R; Vaccarino, F M

    1986-01-01

    Inhibitory gamma-aminobutyric acid-mediated synaptic currents were studied in dissociated primary cultures of neonatal rat cortex with the whole-cell patch-clamp technique. Immunocytochemical staining of the cultures showed the presence of a large number of glutamic acid decarboxylase-containing neurons, and electrical stimulation of randomly selected neurons produced in many cases chloride-mediated and bicuculline-sensitive inhibitory synaptic currents in postsynaptic cells. The amplitude and decay time of the inhibitory synaptic currents were increased by flunitrazepam and decreased by the beta-carboline derivative methyl 6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate, two high-affinity ligands for the allosteric regulatory sites of gamma-aminobutyric acid receptors. The imidazobenzodiazepine Ro 15-1788, another high-affinity ligand of the gamma-aminobutyric acid receptor regulatory sites that has negligible intrinsic activity, blocked the action of flunitrazepam and beta-carboline. However, Ro 15-1788 also increased the decay rate of the inhibitory synaptic currents. This might suggest that an endogenous ligand for the benzodiazepine-beta-carboline binding site is operative in gamma-aminobutyric acid-mediated synaptic transmission. Images PMID:3097650

  8. Synaptic rearrangement following axonal injury: Old and new players.

    PubMed

    Spejo, Aline Barroso; Oliveira, Alexandre L R

    2015-09-01

    Following axotomy, the contact between motoneurons and muscle fibers is disrupted, triggering a retrograde reaction at the neuron cell body within the spinal cord. Together with chromatolysis, a hallmark of such response to injury is the elimination of presynaptic terminals apposing to the soma and proximal dendrites of the injured neuron. Excitatory inputs are preferentially eliminated, leaving the cells under an inhibitory influence during the repair process. This is particularly important to avoid glutamate excitotoxicity. Such shift from transmission to a regeneration state is also reflected by deep metabolic changes, seen by the regulation of several genes related to cell survival and axonal growth. It is unclear, however, how exactly synaptic stripping occurs, but there is substantial evidence that glial cells play an active role in this process. In one hand, immune molecules, such as the major histocompatibility complex (MHC) class I, members of the complement family and Toll-like receptors are actively involved in the elimination/reapposition of presynaptic boutons. On the other hand, plastic changes that involve sprouting might be negatively regulated by extracellular matrix proteins such as Nogo-A, MAG and scar-related chondroitin sulfate proteoglycans. Also, neurotrophins, stem cells, physical exercise and several drugs seem to improve synaptic stability, leading to functional recovery after lesion. This article is part of a Special Issue entitled 'Neuroimmunology and Synaptic Function'. PMID:25445484

  9. Circuit mapping by ultraviolet uncaging of glutamate.

    PubMed

    Shepherd, Gordon M G

    2012-09-01

    In laser photostimulation, small clusters of neurons in brain slices are induced to fire action potentials by focal glutamate uncaging, and synaptic connectivity between photoexcited presynaptic neurons and individual postsynaptic neurons is assessed by intracellular recording of synaptic events. With a scanner, this process can be repeated sequentially across a patterned array of stimulus locations, generating maps of neurons' local sources of synaptic inputs. Laser scanning photostimulation (LSPS) based on patterned glutamate uncaging offers an efficient, quantitative, optical-electrophysiological way to map synaptic circuits in brain slices. The efficacy of glutamate-based photostimulation for circuit mapping (in contrast to electrical stimulation) derives from the ability to stimulate neurons with high precision and speed, and without stimulating axons of passage. This protocol describes the components, assembly, and operation of a laser scanning microscope for ultraviolet (UV) uncaging, along with experimental methods for circuit mapping in brain slices. It presents a general approach and a set of guidelines for quantitative circuit mapping using "standard" LSPS methods based on single-photon glutamate uncaging using a UV laser, a pair of scanning mirror galvanometers, a patch-clamp setup, and open-source data acquisition software. PMID:22949715

  10. Targeting Glia with N-Acetylcysteine Modulates Brain Glutamate and Behaviors Relevant to Neurodevelopmental Disorders in C57BL/6J Mice

    PubMed Central

    Durieux, Alice M. S.; Fernandes, Cathy; Murphy, Declan; Labouesse, Marie Anais; Giovanoli, Sandra; Meyer, Urs; Li, Qi; So, Po-Wah; McAlonan, Grainne

    2015-01-01

    An imbalance between excitatory (E) glutamate and inhibitory (I) GABA transmission may underlie neurodevelopmental conditions such as autism spectrum disorder (ASD) and schizophrenia. This may be direct, through alterations in synaptic genes, but there is increasing evidence for the importance of indirect modulation of E/I balance through glial mechanisms. Here, we used C57BL/6J mice to test the hypothesis that striatal glutamate levels can be shifted by N-acetylcysteine (NAC), which acts at the cystine-glutamate antiporter of glial cells. Striatal glutamate was quantified in vivo using proton magnetic resonance spectroscopy. The effect of NAC on behaviors relevant to ASD was examined in a separate cohort. NAC induced a time-dependent decrease in striatal glutamate, which recapitulated findings of lower striatal glutamate reported in ASD. NAC-treated animals were significantly less active and more anxious in the open field test; and NAC-treated females had significantly impaired prepulse inhibition of startle response. This at least partly mimics greater anxiety and impaired sensorimotor gating reported in neurodevelopmental disorders. Thus glial mechanisms regulate glutamate acutely and have functional consequences even in adulthood. Glial cells may be a potential drug target for the development of new therapies for neurodevelopmental disorders across the life-span. PMID:26696857

  11. The role of gamma-aminobutyric acid/glycinergic synaptic transmission in mediating bilirubin-induced hyperexcitation in developing auditory neurons.

    PubMed

    Yin, Xin-Lu; Liang, Min; Shi, Hai-Bo; Wang, Lu-Yang; Li, Chun-Yan; Yin, Shan-Kai

    2016-01-01

    Hyperbilirubinemia is a common clinical phenomenon observed in human newborns. A high level of bilirubin can result in severe jaundice and bilirubin encephalopathy. However, the cellular mechanisms underlying bilirubin excitotoxicity are unclear. Our previous studies showed the action of gamma-aminobutyric acid (GABA)/glycine switches from excitatory to inhibitory during development in the ventral cochlear nucleus (VCN), one of the most sensitive auditory nuclei to bilirubin toxicity. In the present study, we investigated the roles of GABAA/glycine receptors in the induction of bilirubin hyperexcitation in early developing neurons. Using the patch clamp technique, GABAA/glycine receptor-mediated spontaneous inhibitory synaptic currents (sIPSCs) were recorded from bushy and stellate cells in acute brainstem slices from young mice (postnatal day 2-6). Bilirubin significantly increased the frequency of sIPSCs, and this effect was prevented by pretreatments of slices with either fast or slow Ca(2+) chelators BAPTA-AM and EGTA-AM suggesting that bilirubin can increase the release of GABA/glycine via Ca(2+)-dependent mechanisms. Using cell-attached recording configuration, we found that antagonists of GABAA and glycine receptors strongly attenuated spontaneous spiking firings in P2-6 neurons but produced opposite effect in P15-19 neurons. Furthermore, these antagonists reversed bilirubin-evoked hyperexcitability in P2-6 neurons, indicating that excitatory action of GABA/glycinergic transmission specifically contribute to bilirubin-induced hyperexcitability in the early stage of development. Our results suggest that bilirubin-induced enhancement of presynaptic release GABA/Glycine via Ca(2+)-dependent mechanisms may play a critical role in mediating neuronal hyperexcitation associated with jaundice, implicating potential new strategies for predicting, preventing, and treating bilirubin neurotoxicity. PMID:26476400

  12. Role of Neurotrophin Receptor TrkB in the Maturation of Rod Photoreceptors and Establishment of Synaptic Transmission to the Inner Retina

    PubMed Central

    Rohrer, Baerbel; Korenbrot, Juan I.; LaVail, Matthew M.; Reichardt, Louis F.; Xu, Baoji

    2009-01-01

    Brain-derived neurotrophic factor (BDNF) acts through TrkB, a receptor with kinase activity, and mitigates light-induced apoptosis in adult mouse rod photoreceptors. To determine whether TrkB signaling is necessary for rod development and function, we examined the retinas of mice lacking all isoforms of the TrkB receptor. Rod migration and differentiation occur in the mutant retina, but proceed at slower rates than in wild-type mice. In postnatal day 16 (P16) mutants, rod outer segment dimensions and rhodopsin content are comparable with those of photoreceptors in P12 wild type (WT). Quantitative analyses of the photoreceptor component in the electroretinogram (ERG) indicate that the gain and kinetics of the rod phototransduction signal in dark-adapted P16 mutant and P12 WT retinas are similar. In contrast to P12 WT, however, the ERG in mutant mice entirely lacks a b-wave, indicating a failure of signal transmission in the retinal rod pathway. In the inner retina of mutant mice, although cells appear anatomically and immunohistochemically normal, they fail to respond to prolonged stroboscopic illumination with the normal expression of c-fos. Absence of the b-wave and failure of c-fos expression, in view of anatomically normal inner retinal cells, suggest that lack of TrkB signaling causes a defect in synaptic signaling between rods and inner retinal cells. Retinal pigment epithelial cells and cells in the inner retina, including Müller, amacrine, and retinal ganglion cells, express the TrkB receptor, but rod photoreceptors do not. Moreover, inner retinal cells respond to exogenous BDNF with c-fos expression and extracellular signal-regulated kinase phosphorylation. Thus, interactions of rods with TrkB-expressing cells must be required for normal rod development. PMID:10516311

  13. Whole-Cell Patch-Clamp Analysis of Recombinant NMDA Receptor Pharmacology Using Brief Glutamate Applications

    PubMed Central

    Glasgow, Nathan G.; Johnson, Jon W.

    2015-01-01

    Summary NMDA receptors (NMDARs) are ionotropic glutamate receptors that are essential for synaptic plasticity, learning and memory. Dysfunction of NMDARs has been implicated in many nervous system disorders; therefore, pharmacological modulation of NMDAR activity has great therapeutic potential. However, given the broad physiological importance of NMDARs, modulating their activity often has detrimental side effects precluding pharmaceutical use of many NMDAR modulators. One approach to possibly improve the therapeutic potential of NMDAR modulators is to identify compounds that modulate subsets of NMDARs. An obvious target for modulating NMDAR subsets are the many NMDAR subtypes produced through different combinations of NMDAR subunits. With seven identified genes that encode NMDAR subunits, there are many neuronal NMDAR subtypes with distinct properties and potentially differential pharmacological sensitivities. Study of NMDAR subtype-specific pharmacology is complicated in neurons, however, because most neurons express at least three NMDAR subtypes. Thus, use of an approach that permits study in isolation of a single receptor subtype is preferred. Additionally, the effects of drugs on agonist-activated responses typically depend on duration of agonist exposure. To evaluate drug effects on synaptic transmission, an approach should be used that allows activation of receptor responses as brief as those observed during synaptic transmission, both in the absence and presence of drug. To address these issues, we designed a fast perfusion system capable of (1) delivering brief (~5 ms) and consistent applications of glutamate to recombinant NMDARs of known subunit composition, and (2) easily and quickly (~5 seconds) changing between glutamate applications in the absence and presence of drug. PMID:25023300

  14. Synaptic inhibition and γ-aminobutyric acid in the mammalian central nervous system

    PubMed Central

    OBATA, Kunihiko

    2013-01-01

    Signal transmission through synapses connecting two neurons is mediated by release of neurotransmitter from the presynaptic axon terminals and activation of its receptor at the postsynaptic neurons. γ-Aminobutyric acid (GABA), non-protein amino acid formed by decarboxylation of glutamic acid, is a principal neurotransmitter at inhibitory synapses of vertebrate and invertebrate nervous system. On one hand glutamic acid serves as a principal excitatory neurotransmitter. This article reviews GABA researches on; (1) synaptic inhibition by membrane hyperpolarization, (2) exclusive localization in inhibitory neurons, (3) release from inhibitory neurons, (4) excitatory action at developmental stage, (5) phenotype of GABA-deficient mouse produced by gene-targeting, (6) developmental adjustment of neural network and (7) neurological/psychiatric disorder. In the end, GABA functions in simple nervous system and plants, and non-amino acid neurotransmitters were supplemented. PMID:23574805

  15. Controlling ionotropic and metabotropic glutamate receptors with light: principles and potential

    PubMed Central

    Reiner, Andreas; Levitz, Joshua; Isacoff, Ehud Y.

    2014-01-01

    Light offers unique advantages for studying and manipulating biomolecules and the cellular processes that they control. Optical control of ionotropic and metabotropic glutamate receptors has garnered significant interest, since these receptors are central to signaling at neuronal synapses and only optical approaches provide the spatial and temporal resolution required to directly probe receptor function in cells and tissue. Following the classical method of glutamate photo-uncaging, recently developed methods have added other forms of remote control, including those with high molecular specificity and genetic targeting. These tools open the door to the direct optical control of synaptic transmission and plasticity, as well as the probing of native receptor function in intact neural circuits. PMID:25573450

  16. Loss of Local Astrocyte Support Disrupts Action Potential Propagation and Glutamate Release Synchrony from Unmyelinated Hippocampal Axon Terminals In Vitro

    PubMed Central

    Sobieski, Courtney; Jiang, Xiaoping; Crawford, Devon C.

    2015-01-01

    Neuron–astrocyte interactions are critical for proper CNS development and function. Astrocytes secrete factors that are pivotal for synaptic development and function, neuronal metabolism, and neuronal survival. Our understanding of this relationship, however, remains incomplete due to technical hurdles that have prevented the removal of astrocytes from neuronal circuits without changing other important conditions. Here we overcame this obstacle by growing solitary rat hippocampal neurons on microcultures that were comprised of either an astrocyte bed (+astrocyte) or a collagen bed (−astrocyte) within the same culture dish. −Astrocyte autaptic evoked EPSCs, but not IPSCs, displayed an altered temporal profile, which included increased synaptic delay, increased time to peak, and severe glutamate release asynchrony, distinct from previously described quantal asynchrony. Although we observed minimal alteration of the somatically recorded action potential waveform, action potential propagation was altered. We observed a longer latency between somatic initiation and arrival at distal locations, which likely explains asynchronous EPSC peaks, and we observed broadening of the axonal spike, which likely underlies changes to evoked EPSC onset. No apparent changes in axon structure were observed, suggesting altered axonal excitability. In conclusion, we propose that local astrocyte support has an unappreciated role in maintaining glutamate release synchrony by disturbing axonal signal propagation. SIGNIFICANCE STATEMENT Certain glial cell types (oligodendrocytes, Schwann cells) facilitate the propagation of neuronal electrical signals, but a role for astrocytes has not been identified despite many other functions of astrocytes in supporting and modulating neuronal signaling. Under identical global conditions, we cultured neurons with or without local astrocyte support. Without local astrocytes, glutamate transmission was desynchronized by an alteration of the waveform

  17. The EHD protein Past1 controls postsynaptic membrane elaboration and synaptic function

    PubMed Central

    Koles, Kate; Messelaar, Emily M.; Feiger, Zachary; Yu, Crystal J.; Frank, C. Andrew; Rodal, Avital A.

    2015-01-01

    Membranes form elaborate structures that are highly tailored to their specialized cellular functions, yet the mechanisms by which these structures are shaped remain poorly understood. Here, we show that the conserved membrane-remodeling C-terminal Eps15 Homology Domain (EHD) protein Past1 is required for the normal assembly of the subsynaptic muscle membrane reticulum (SSR) at the Drosophila melanogaster larval neuromuscular junction (NMJ). past1 mutants exhibit altered NMJ morphology, decreased synaptic transmission, reduced glutamate receptor levels, and a deficit in synaptic homeostasis. The membrane-remodeling proteins Amphiphysin and Syndapin colocalize with Past1 in distinct SSR subdomains and collapse into Amphiphysin-dependent membrane nodules in the SSR of past1 mutants. Our results suggest a mechanism by which the coordinated actions of multiple lipid-binding proteins lead to the elaboration of increasing layers of the SSR and uncover new roles for an EHD protein at synapses. PMID:26202464

  18. The Amino Acid Transporter JhI-21 Coevolves with Glutamate Receptors, Impacts NMJ Physiology, and Influences Locomotor Activity in Drosophila Larvae.

    PubMed

    Ziegler, Anna B; Augustin, Hrvoje; Clark, Nathan L; Berthelot-Grosjean, Martine; Simonnet, Mégane M; Steinert, Joern R; Geillon, Flore; Manière, Gérard; Featherstone, David E; Grosjean, Yael

    2016-01-01

    Changes in synaptic physiology underlie neuronal network plasticity and behavioral phenomena, which are adjusted during development. The Drosophila larval glutamatergic neuromuscular junction (NMJ) represents a powerful synaptic model to investigate factors impacting these processes. Amino acids such as glutamate have been shown to regulate Drosophila NMJ physiology by modulating the clustering of postsynaptic glutamate receptors and thereby regulating the strength of signal transmission from the motor neuron to the muscle cell. To identify amino acid transporters impacting glutmatergic signal transmission, we used Evolutionary Rate Covariation (ERC), a recently developed bioinformatic tool. Our screen identified ten proteins co-evolving with NMJ glutamate receptors. We selected one candidate transporter, the SLC7 (Solute Carrier) transporter family member JhI-21 (Juvenile hormone Inducible-21), which is expressed in Drosophila larval motor neurons. We show that JhI-21 suppresses postsynaptic muscle glutamate receptor abundance, and that JhI-21 expression in motor neurons regulates larval crawling behavior in a developmental stage-specific manner. PMID:26805723

  19. The Amino Acid Transporter JhI-21 Coevolves with Glutamate Receptors, Impacts NMJ Physiology, and Influences Locomotor Activity in Drosophila Larvae

    PubMed Central

    Ziegler, Anna B.; Augustin, Hrvoje; Clark, Nathan L.; Berthelot-Grosjean, Martine; Simonnet, Mégane M.; Steinert, Joern R.; Geillon, Flore; Manière, Gérard; Featherstone, David E.; Grosjean, Yael

    2016-01-01

    Changes in synaptic physiology underlie neuronal network plasticity and behavioral phenomena, which are adjusted during development. The Drosophila larval glutamatergic neuromuscular junction (NMJ) represents a powerful synaptic model to investigate factors impacting these processes. Amino acids such as glutamate have been shown to regulate Drosophila NMJ physiology by modulating the clustering of postsynaptic glutamate receptors and thereby regulating the strength of signal transmission from the motor neuron to the muscle cell. To identify amino acid transporters impacting glutmatergic signal transmission, we used Evolutionary Rate Covariation (ERC), a recently developed bioinformatic tool. Our screen identified ten proteins co-evolving with NMJ glutamate receptors. We selected one candidate transporter, the SLC7 (Solute Carrier) transporter family member JhI-21 (Juvenile hormone Inducible-21), which is expressed in Drosophila larval motor neurons. We show that JhI-21 suppresses postsynaptic muscle glutamate receptor abundance, and that JhI-21 expression in motor neurons regulates larval crawling behavior in a developmental stage-specific manner. PMID:26805723

  20. Synaptic Function of Rab11Fip5: Selective Requirement for Hippocampal Long-Term Depression.

    PubMed

    Bacaj, Taulant; Ahmad, Mohiuddin; Jurado, Sandra; Malenka, Robert C; Südhof, Thomas C

    2015-05-13

    Postsynaptic AMPA-type glutamate receptors (AMPARs) are among the major determinants of synaptic strength and can be trafficked into and out of synapses. Neuronal activity regulates AMPAR trafficking during synaptic plasticity to induce long-term changes in synaptic strength, including long-term potentiation (LTP) and long-term depression (LTD). Rab family GTPases regulate most membrane trafficking in eukaryotic cells; particularly, Rab11 and its effectors are implicated in mediating postsynaptic AMPAR insertion during LTP. To explore the synaptic function of Rab11Fip5, a neuronal Rab11 effector and a candidate autism-spectrum disorder gene, we performed shRNA-mediated knock-down and genetic knock-out (KO) studies. Surprisingly, we observed robust shRNA-induced synaptic phenotypes that were rescued by a Rab11Fip5 cDNA but that were nevertheless not observed in conditional KO neurons. Both in cultured neurons and acute slices, KO of Rab11Fip5 had no significant effect on basic parameters of synaptic transmission, indicating that Rab11Fip5 is not required for fundamental synaptic operations, such as neurotransmitter release or postsynaptic AMPAR insertion. KO of Rab11Fip5 did, however, abolish hippocampal LTD as measured both in acute slices or using a chemical LTD protocol in cultured neurons but did not affect hippocampal LTP. The Rab11Fip5 KO mice performed normally in several behavioral tasks, including fear conditioning, but showed enhanced contextual fear extinction. These are the first findings to suggest a requirement for Rab11Fip5, and presumably Rab11, during LTD. PMID:25972173

  1. Fumarates modulate microglia activation through a novel HCAR2 signaling pathway and rescue synaptic dysregulation in inflamed CNS.

    PubMed

    Parodi, Benedetta; Rossi, Silvia; Morando, Sara; Cordano, Christian; Bragoni, Alberto; Motta, Caterina; Usai, Cesare; Wipke, Brian T; Scannevin, Robert H; Mancardi, Giovanni L; Centonze, Diego; Kerlero de Rosbo, Nicole; Uccelli, Antonio

    2015-08-01

    Dimethyl fumarate (DMF), recently approved as an oral immunomodulatory treatment for relapsing-remitting multiple sclerosis (MS), metabolizes to monomethyl fumarate (MMF) which crosses the blood-brain barrier and has demonstrated neuroprotective effects in experimental studies. We postulated that MMF exerts neuroprotective effects through modulation of microglia activation, a critical component of the neuroinflammatory cascade that occurs in neurodegenerative diseases such as MS. To ascertain our hypothesis and define the mechanistic pathways involved in the modulating effect of fumarates, we used real-time PCR and biochemical assays to assess changes in the molecular and functional phenotype of microglia, quantitative Western blotting to monitor activation of postulated pathway components, and ex vivo whole-cell patch clamp recording of excitatory post-synaptic currents in corticostriatal slices from mice with experimental autoimmune encephalomyelitis (EAE), a model for MS, to study synaptic transmission. We show that exposure to MMF switches the molecular and functional phenotype of activated microglia from classically activated, pro-inflammatory type to alternatively activated, neuroprotective one, through activation of the hydroxycarboxylic acid receptor 2 (HCAR2). We validate a downstream pathway mediated through the AMPK-Sirt1 axis resulting in deacetylation, and thereby inhibition, of NF-κB and, consequently, of secretion of pro-inflammatory molecules. We demonstrate through ex vivo monitoring of spontaneous glutamate-mediated excitatory post-synaptic currents of single neurons in corticostriatal slices from EAE mice that the neuroprotective effect of DMF was exerted on neurons at pre-synaptic terminals by modulating glutamate release. By exposing control slices to untreated and MMF-treated activated microglia, we confirm the modulating effect of MMF on microglia function and, thereby, its indirect neuroprotective effect at post-synaptic level. These

  2. Changes in synaptic transmission of substantia gelatinosa neurons after spinal cord hemisection revealed by analysis using in vivo patch-clamp recording

    PubMed Central

    Kozuka, Yuji; Furue, Hidemasa; Ishida, Takashi; Tanaka, Satoshi; Namiki, Akiyoshi; Yamakage, Michiaki

    2016-01-01

    Background After spinal cord injury, central neuropathic pain develops in the majority of spinal cord injury patients. Spinal hemisection in rats, which has been developed as an animal model of spinal cord injury in humans, results in hyperexcitation of spinal dorsal horn neurons soon after the hemisection and thereafter. The hyperexcitation is likely caused by permanent elimination of the descending pain systems. We examined the change in synaptic transmission of substantia gelatinosa neurons following acute spinal hemisection by using an in vivo whole-cell patch-clamp technique. Results An increased spontaneous action potential firings of substantia gelatinosa neurons was detected in hemisected rats compared with that in control animals. The frequencies and amplitudes of spontaneous excitatory postsynaptic currents and of evoked excitatory postsynaptic currentss in response to non-noxious and noxious stimuli were not different between hemisected and control animals. On the contrary, the amplitude and frequency of spontaneous inhibitory postsynaptic currents of substantia gelatinosa neurons in hemisected animals were significantly smaller and lower, respectively, than those in control animals (P < 0.01). Large amplitude and high-frequency spontaneous inhibitory postsynaptic currents, which could not be elicited by mechanical stimuli, were seen in 44% of substantia gelatinosa neurons in control animals but only in 17% of substantia gelatinosa neurons in hemisected animals. In control animals, such large amplitude spontaneous inhibitory postsynaptic currents were suppressed by spinal application of tetrodotoxin (1 µM). Cervical application of lidocaine (2%, 10 µl) also inhibited such large amplitude of inhibitory postsynaptic currents. The proportion of multi-receptive substantia gelatinosa neurons, which exhibit action potential firing in response to non-noxious and noxious stimuli, was much larger in hemisected animals than in control animals

  3. Altered synaptic transmission at olfactory and vomeronasal nerve terminals in mice lacking N-type calcium channel Cav2.2.

    PubMed

    Weiss, Jan; Pyrski, Martina; Weissgerber, Petra; Zufall, Frank

    2014-11-01

    We investigated the role of voltage-activated calcium (Cav) channels for synaptic transmission at mouse olfactory and vomeronasal nerve terminals at the first synapse of the main and accessory olfactory pathways, respectively. We provided evidence for a central role of the N-type Cav channel subunit Cav2.2 in presynaptic transmitter release at these synapses. Striking Cav2.2 immunoreactivity was localised to the glomerular neuropil of the main olfactory bulb (MOB) and accessory olfactory bulb (AOB), and co-localised with presynaptic molecules such as bassoon. Voltage-clamp recordings of sensory nerve-evoked, excitatory postsynaptic currents (EPSCs) in mitral/tufted (M/T) and superficial tufted cells of the MOB and mitral cells of the AOB, in combination with established subtype-specific Cav channel toxins, indicated a predominant role of N-type channels in transmitter release at these synapses, whereas L-type, P/Q-type, and R-type channels had either no or only relatively minor contributions. In Cacna1b mutant mice lacking the Cav2.2 (α1B) subunit of N-type channels, olfactory nerve-evoked M/T cell EPSCs were not reduced but became blocker-resistant, thus indicating a major reorganisation and compensation of Cav channel subunits as a result of the Cav2.2 deletion at this synapse. Cav2.2-deficient mice also revealed that Cav2.2 was critically required for paired-pulse depression of olfactory nerve-evoked EPSCs in M/T cells of the MOB, and they demonstrated an essential requirement for Cav2.2 in vomeronasal nerve-evoked EPSCs of AOB mitral cells. Thus, Cacna1b loss-of-function mutations are unlikely to cause general anosmia but Cacna1b emerges as a strong candidate in the search for mutations causing altered olfactory perception, such as changes in general olfactory sensitivity and altered social responses to chemostimuli. PMID:25195871

  4. Matrix Metalloproteinase-9 as a Novel Player in Synaptic Plasticity and Schizophrenia

    PubMed Central

    Lepeta, Katarzyna; Kaczmarek, Leszek

    2015-01-01

    Recent findings implicate alterations in glutamate signaling, leading to aberrant synaptic plasticity, in schizophrenia. Matrix metalloproteinase-9 (MMP-9) has been shown to regulate glutamate receptors, be regulated by glutamate at excitatory synapses, and modulate physiological and morphological synaptic plasticity. By means of functional gene polymorphism, gene responsiveness to antipsychotics and blood plasma levels MMP-9 has recently been implicated in schizophrenia. This commentary critically reviews these findings based on the hypothesis that MMP-9 contributes to pathological synaptic plasticity in schizophrenia. PMID:25837304

  5. AMPA receptor trafficking and the mechanisms underlying synaptic plasticity and cognitive aging.

    PubMed

    Henley, Jeremy M; Wilkinson, Kevin A

    2013-03-01

    Even in healthy individuals there is an inexorable agerelated decline in cognitive function. This is due, in large part, to reduced synaptic plasticity caused by changes in the molecular composition of the postsynaptic membrane. AMPA receptors (AMPARs) are glutamate-gated cation channels that mediate the overwhelming majority of fast excitatory transmission in the brain. Changes in AMPAR number and/or function are a core feature of synaptic plasticity and age-related cognitive decline, AMPARs are highly dynamic proteins that are subject to highly controlled trafficking, recycling, and/or degradation and replacement. This active regulation of AMPAR synthesis, targeting, synaptic dwell time, and degradation is fundamentally important for memory formation and storage. Further, aberrant AMPAR trafficking and consequent detrimental changes in synapses are strongly implicated in many brain diseases, which represent a vast social and economic burden. The purpose of this article is to provide an overview of the molecular and cellular AMPA receptor trafficking events that control synaptic responsiveness and plasticity, and highlight what is known currently known about how these processes change with age and disease. PMID:23576886

  6. AMPA receptor trafficking and the mechanisms underlying synaptic plasticity and cognitive aging

    PubMed Central

    Henley, Jeremy M.; Wilkinson, Kevin A.

    2013-01-01

    Even in healthy individuals there is an inexorable agerelated decline in cognitive function. This is due, in large part, to reduced synaptic plasticity caused by changes in the molecular composition of the postsynaptic membrane. AMPA receptors (AMPARs) are glutamate-gated cation channels that mediate the overwhelming majority of fast excitatory transmission in the brain. Changes in AMPAR number and/or function are a core feature of synaptic plasticity and age-related cognitive decline, AMPARs are highly dynamic proteins that are subject to highly controlled trafficking, recycling, and/or degradation and replacement. This active regulation of AMPAR synthesis, targeting, synaptic dwell time, and degradation is fundamentally important for memory formation and storage. Further, aberrant AMPAR trafficking and consequent detrimental changes in synapses are strongly implicated in many brain diseases, which represent a vast social and economic burden. The purpose of this article is to provide an overview of the molecular and cellular AMPA receptor trafficking events that control synaptic responsiveness and plasticity, and highlight what is known currently known about how these processes change with age and disease. PMID:23576886

  7. Pregnenolone sulfate induces NMDA receptor dependent release of dopamIne from synaptIc termInals in the striatum

    PubMed Central

    Whittaker, Matthew T.; Gibbs, Terrell T.; Farb, David H.

    2009-01-01

    Neuromodulators that alter the balance between lower-frequency glutamate-mediated excitatory and higher-frequency GABA-mediated inhibitory synaptic transmission are likely to participate in core mechanisms for CNS function and may contribute to the pathophysiology of neurological disorders such as schizophrenia and Alzheimer's disease. Pregnenolone sulfate (PS) modulates both ionotropic glutamate and GABAA receptor mediated synaptic transmission. The enzymes necessary for PS synthesis and degradation are found in brain tissue of several species including human and rat, and up to 5 nM PS has been detected in extracts of postmortem human brain. Here, we ask whether PS could modulate transmitter release from nerve terminals located in the striatum. Superfusion of a preparation of striatal nerve terminals comprised of mixed synaptosomes and synaptoneurosomes with brief-duration (2 min) pulses of 25 nM PS demonstrates that PS increases the release of newly accumulated [3H]dopamine ([3H]DA), but not [14C]glutamate or [3H]GABA, whereas pregnenolone is without effect. PS does not affect dopamine transporter (DAT) mediated uptake of [3H]DA, demonstrating that it specifically affects the transmitter release mechanism. The PS-induced [3H]DA release occurs via an NMDA receptor (NMDAR) dependent mechanism as it is blocked by D-2-amino-5-phosphonovaleric acid. PS modulates DA release with very high potency, significantly increasing [3H]DA release at PS concentrations as low as 25 pM. This first report of a selective direct enhancement of synaptosomal dopamine release by PS at picomolar concentrations via an NMDAR dependent mechanism raises the possibility that dopaminergic axon terminals may be a site of action for this neurosteroid. PMID:18710414

  8. Sulforhodamine 101 induces long-tem potentiation of intrinsic excitability and synaptic efficacy in hippocampal CA1 pyramidal neurons

    PubMed Central

    Kang, Jian; Kang, Ning; Yu, Yufei; Zhang, Jinsong; Petersen, Nicolas; Tian, Guo-Feng; Nedergaard, Maiken

    2010-01-01

    Sulforhodamine 101 (SR101) has been extensively used for investigation as a specific marker for astroglia in vivo and activity-dependent dye for monitoring regulated exocytosis. Here, we report that SR101 has bioactive effects on neuronal activity. Perfusion of slices with SR101 (1 μM) for 10 min induced long-term potentiation of intrinsic neuronal excitability (LTP-IE) and a long-lasting increase in evoked EPSCs (eEPSCs) in CA1 pyramidal neurons in hippocampal slices. The increase in intrinsic neuronal excitability was a result of negative shifts in the action potential (AP) threshold. The N-methyl D-aspartate receptor (NMDAR) antagonist, AP-5 (50 μM), blocked SR101-induced LTP-IE, but glutamate receptor blockers, AP-5 (50 μM), MCPG (200 μM), and MSOP (100 μM), only partially blocked SR101-induced potentiation of eEPSCs. SR101 induced an enhancement of evoked synaptic NMDAR currents, suggesting that SR101 enhances activation of synaptic NMDARs. SR101-induced LTP-IE and potentiation of synaptic transmission triggered spontaneous neuronal firing in slices and in vivo epileptic seizures. Our results suggest that SR101 is an epileptogenic agent that long-lastingly lowers the AP threshold to increase intrinsic neuronal excitability and enhances the synaptic efficacy to increase synaptic inputs. As such, SR101 can be used as an experimental tool to induce epileptic seizures. PMID:20600669

  9. An investigation of interactions between hypocretin/orexin signaling and glutamate receptor surface expression in the rat nucleus accumbens under basal conditions and after cocaine exposure

    PubMed Central

    Plaza-Zabala, Ainhoa; Li, Xuan; Milovanovic, Mike; Loweth, Jessica A.; Maldonado, Rafael; Berrendero, Fernando; Wolf, Marina E.

    2013-01-01

    Hypocretin peptides are critical for the effects of cocaine on excitatory synaptic strength in the ventral tegmental area (VTA). However, little is known about their role in cocaine-induced synaptic plasticity in the nucleus accumbens (NAc). First, we tested whether hypocretin-1 by itself could acutely modulate glutamate receptor surface expression in the NAc, given that hypocretin-1 in the VTA reproduces cocaine’s effects on glutamate transmission. We found no effect of hypocretin-1 infusion on AMPA or NMDA receptor surface expression in the NAc, measured by biotinylation, either 30 min or 3 h after the infusion. Second, we were interested in whether changes in hypocretin receptor-2 (Hcrtr-2) expression contribute to cocaine-induced plasticity in the NAc. As a first step towards addressing this question, Hcrtr-2 surface expression was compared in the NAc after withdrawal from extended-access self-administration of saline (control) versus cocaine. We found that surface Hcrtr-2 levels remain unchanged following 14, 25 or 48 days of withdrawal from cocaine, a time period in which high conductance GluA2-lacking AMPA receptors progressively emerge in the NAc. Overall, our results fail to support a role for hypocretins in acute modulation of glutamate receptor levels in the NAc or a role for altered Hcrtr-2 expression in withdrawal-dependent synaptic adaptations in the NAc following cocaine self-administration. PMID:24262606

  10. P301L tau expression affects glutamate release and clearance in the hippocampal trisynaptic pathway.

    PubMed

    Hunsberger, Holly C; Rudy, Carolyn C; Batten, Seth R; Gerhardt, Greg A; Reed, Miranda N

    2015-01-01

    Individuals at risk of developing Alzheimer's disease (AD) often exhibit hippocampal hyperexcitability. A growing body of evidence suggests that perturbations in the glutamatergic tripartite synapse may underlie this hyperexcitability. Here, we used a tau mouse model of AD (rTg(TauP301L)4510) to examine the effects of tau pathology on hippocampal glutamate regulation. We found a 40% increase in hippocampal vesicular glutamate transporter, which packages glutamate into vesicles, and has previously been shown to influence glutamate release, and a 40% decrease in hippocampal glutamate transporter 1, the major glutamate transporter responsible for removing glutamate from the extracellular space. To determine whether these alterations affected glutamate regulation in vivo, we measured tonic glutamate levels, potassium-evoked glutamate release, and glutamate uptake/clearance in the dentate gyrus, cornu ammonis 3(CA3), and cornu ammonis 1(CA1) regions of the hippocampus. P301L tau expression resulted in a 4- and 7-fold increase in potassium-evoked glutamate release in the dentate gyrus and CA3, respectively, and significantly decreased glutamate clearance in all three regions. Both release and clearance correlated with memory performance in the hippocampal-dependent Barnes maze task. Alterations in mice expressing P301L were observed at a time when tau pathology was subtle and before readily detectable neuron loss. These data suggest novel mechanisms by which tau may mediate hyperexcitability. Pre-synaptic vesicular glutamate transporters (vGLUTs) package glutamate into vesicles before exocytosis into the synaptic cleft. Once in the extracellular space, glutamate acts on glutamate receptors. Glutamate is removed from the extracellular space by excitatory amino acid transporters, including GLT-1, predominantly localized to glia. P301L tau expression increases vGLUT expression and glutamate release, while also decreasing GLT-1 expression and glutamate clearance. PMID

  11. Synaptic excitation is regulated by the postsynaptic dSK channel at the Drosophila larval NMJ

    PubMed Central

    Gertner, Daniel M.; Desai, Sunil

    2014-01-01

    In the mammalian central nervous system, the postsynaptic small-conductance Ca2+-dependent K+ (SK) channel has been shown to reduce postsynaptic depolarization and limit Ca2+ influx through N-methyl-d-aspartate receptors. To examine further the role of the postsynaptic SK channel in synaptic transmission, we studied its action at the Drosophila larval neuromuscular junction (NMJ). Repetitive synaptic stimulation produced an increase in postsynaptic membrane conductance leading to depression of excitatory postsynaptic potential amplitude and hyperpolarization of the resting membrane potential (RMP). This reduction in synaptic excitation was due to the postsynaptic Drosophila SK (dSK) channel; synaptic depression, increased membrane conductance and RMP hyperpolarization were reduced in dSK mutants or after expressing a Ca2+ buffer in the muscle. Ca2+ entering at the postsynaptic membrane was sufficient to activate dSK channels based upon studies in which the muscle membrane was voltage clamped to prevent opening voltage-dependent Ca2+ channels. Increasing external Ca2+ produced an increase in resting membrane conductance and RMP that was not seen in dSK mutants or after adding the glutamate-receptor blocker philanthotoxin. Thus it appeared that dSK channels were also activated by spontaneous transmitter release and played a role in setting membrane conductance and RMP. In mammals, dephosphorylation by protein phosphatase 2A (PP2A) increased the Ca2+ sensitivity of the SK channel; PP2A appeared to increase the sensitivity of the dSK channel since PP2A inhibitors reduced activation of the dSK channel by evoked synaptic activity or increased external Ca2+. It is proposed that spontaneous and evoked transmitter release activate the postsynaptic dSK channel to limit synaptic excitation and stabilize synapses. PMID:24671529

  12. Insulin-Like Growth Factor I Produces an Antidepressant-Like Effect and Elicits N-Methyl-D-Aspartate Receptor Independent Long-Term Potentiation of Synaptic Transmission in Medial Prefrontal Cortex and Hippocampus

    PubMed Central

    Zhang, Xiao-lei; Colechio, Elizabeth M.; Ghoreishi-Haack, Nayereh; Gross, Amanda; Kroes, Roger A.; Stanton, Patric K.; Moskal, Joseph R.

    2016-01-01

    Background: Growth factors play an important role in regulating neurogenesis and synapse formation and may be involved in regulating the antidepressant response to conventional antidepressants. To date, Insulin-like growth factor I (IGFI) is the only growth factor that has shown antidepressant properties in human clinical trials. However, its mechanism of action remains unclear. Methods: The antidepressant-like effect of a single IV dose of IGFI was determined using a chronic unpredictable stress paradigm in the rat Porsolt, sucrose preference, novelty-induced hypophagia, and ultrasonic vocalization models. The dependence of the medial prefrontal cortex for these effects was determined by direct medial prefrontal cortex injection followed by Porsolt testing as well as IGFI receptor activation in the medial prefrontal cortex following an optimal IV antidepressant-like dose of IGFI. The effect of IGFI on synaptic transmission and long-term potentiation (LTP) of synaptic strength was assessed in the hippocampus and medial prefrontal cortex. The dependence of these effects on IGFI and AMPA receptor activation and protein synthesis were also determined. Results: IGFI produced a rapid-acting and long-lasting antidepressant-like effect in each of the depression models. These effects were blocked by IGFI and AMPA receptor antagonists, and medial prefrontal cortex was localized. IGFI robustly increased synaptic strength in the hippocampus and medial prefrontal cortex and these effects were IGFI receptor and protein synthesis-dependent but N-methyl-d-aspartate receptor independent. IGFI also robustly facilitated hippocampal metaplasticity 24 hours postdosing. Conclusions: These data support the conclusion that the antidepressant-like effects of IGFI are mediated by a persistent, LTP-like enhancement of synaptic strength requiring both IGFIR activation and ongoing protein synthesis. PMID:26374350

  13. Presynaptic Na+-dependent transport and exocytose of GABA and glutamate in brain in hypergravity.

    NASA Astrophysics Data System (ADS)

    Borisova, T.; Pozdnyakova, N.; Krisanova, N.; Himmelreich, N.

    γ-Aminobutyric acid (GABA) and L-glutamate are the most widespread neurotransmitter amino acids in the mammalian central nervous system. GABA is now widely recognized as the major inhibitory neurotransmitter. L-glutamate mediates the most of excitatory synaptic neurotransmission in the brain. They involved in the main aspects of normal brain function. The nerve terminals (synaptosomes) offer several advantages as a model system for the study of general mechanisms of neurosecretion. Our data allowed to conclude that exposure of animals to hypergravity (centrifugation of rats at 10G for 1 hour) had a profound effect on synaptic processes in brain. Comparative analysis of uptake and release of GABA and glutamate have demonstrated that hypergravity loading evokes oppositely directed alterations in inhibitory and excitatory signal transmission. We studied the maximal velocities of [^3H]GABA reuptake and revealed more than twofold enhancement of GABA transporter activity (Vmax rises from 1.4 |pm 0.3 nmol/min/mg of protein in the control group to 3.3 ± 0.59 nmol/min/mg of protein for animals exposed to hypergravity (P ≤ 0.05)). Recently we have also demonstrated the significant lowering of glutamate transporter activity (Vmax of glutamate reuptake decreased from 12.5 ± 3.2 nmol/min/mg of protein in the control group to 5.6 ± 0.9 nmol/min/mg of protein in the group of animals, exposed to the hypergravity stress (P ≤ 0.05)). Significant changes occurred in release of neurotransmitters induced by stimulating exocytosis with the agents, which depolarized nerve terminal plasma membrane. Depolarization-evoked Ca2+-stimulated release was more abundant for GABA (7.2 ± 0.54% and 11,74 ±1,2 % of total accumulated label for control and hypergravity, respectively (P≤0.05)) and was essentially less for glutamate (14.4 ± 0.7% and 6.2 ± 1.9%) after exposure of animals to centrifuge induced artificial gravity. Changes observed in depolarization-evoked exocytotic release

  14. EDITORIAL: Synaptic electronics Synaptic electronics

    NASA Astrophysics Data System (ADS)

    Demming, Anna; Gimzewski, James K.; Vuillaume, Dominique

    2013-09-01

    Conventional computers excel in logic and accurate scientific calculations but make hard work of open ended problems that human brains handle easily. Even von Neumann—the mathematician and polymath who first developed the programming architecture that forms the basis of today's computers—was already looking to the brain for future developments before his death in 1957 [1]. Neuromorphic computing uses approaches that better mimic the working of the human brain. Recent developments in nanotechnology are now providing structures with very accommodating properties for neuromorphic approaches. This special issue, with guest editors James K Gimzewski and Dominique Vuillaume, is devoted to research at the serendipitous interface between the two disciplines. 'Synaptic electronics', looks at artificial devices with connections that demonstrate behaviour similar to synapses in the nervous system allowing a new and more powerful approach to computing. Synapses and connecting neurons respond differently to incident signals depending on the history of signals previously experienced, ultimately leading to short term and long term memory behaviour. The basic characteristics of a synapse can be replicated with around ten simple transistors. However with the human brain having around 1011 neurons and 1015 synapses, artificial neurons and synapses from basic transistors are unlikely to accommodate the scalability required. The discovery of nanoscale elements that function as 'memristors' has provided a key tool for the implementation of synaptic connections [2]. Leon Chua first developed the concept of the 'The memristor—the missing circuit element' in 1971 [3]. In this special issue he presents a tutorial describing how memristor research has fed into our understanding of synaptic behaviour and how they can be applied in information processing [4]. He also describes, 'The new principle of local activity, which uncovers a minuscule life-enabling "Goldilocks zone", dubbed the

  15. EDITORIAL: Synaptic electronics Synaptic electronics

    NASA Astrophysics Data System (ADS)

    Demming, Anna; Gimzewski, James K.; Vuillaume, Dominique

    2013-09-01

    Conventional computers excel in logic and accurate scientific calculations but make hard work of open ended problems that human brains handle easily. Even von Neumann—the mathematician and polymath who first developed the programming architecture that forms the basis of today's computers—was already looking to the brain for future developments before his death in 1957 [1]. Neuromorphic computing uses approaches that better mimic the working of the human brain. Recent developments in nanotechnology are now providing structures with very accommodating properties for neuromorphic approaches. This special issue, with guest editors James K Gimzewski and Dominique Vuillaume, is devoted to research at the serendipitous interface between the two disciplines. 'Synaptic electronics', looks at artificial devices with connections that demonstrate behaviour similar to synapses in the nervous system allowing a new and more powerful approach to computing. Synapses and connecting neurons respond differently to incident signals depending on the history of signals previously experienced, ultimately leading to short term and long term memory behaviour. The basic characteristics of a synapse can be replicated with around ten simple transistors. However with the human brain having around 1011 neurons and 1015 synapses, artificial neurons and synapses from basic transistors are unlikely to accommodate the scalability required. The discovery of nanoscale elements that function as 'memristors' has provided a key tool for the implementation of synaptic connections [2]. Leon Chua first developed the concept of the 'The memristor—the missing circuit element' in 1971 [3]. In this special issue he presents a tutorial describing how memristor research has fed into our understanding of synaptic behaviour and how they can be applied in information processing [4]. He also describes, 'The new principle of local activity, which uncovers a minuscule life-enabling "Goldilocks zone", dubbed the

  16. Molecular underpinnings of synaptic vesicle pool heterogeneity.

    PubMed

    Crawford, Devon C; Kavalali, Ege T

    2015-04-01

    Neuronal communication relies on chemical synaptic transmission for information transfer and processing. Chemical neurotransmission is initiated by synaptic vesicle fusion with the presynaptic active zone resulting in release of neurotransmitters. Classical models have assumed that all synaptic vesicles within a synapse have the same potential to fuse under different functional contexts. In this model, functional differences among synaptic vesicle populations are ascribed to their spatial distribution in the synapse with respect to the active zone. Emerging evidence suggests, however, that synaptic vesicles are not a homogenous population of organelles, and they possess intrinsic molecular differences and differential interaction partners. Recent studies have reported a diverse array of synaptic molecules that selectively regulate synaptic vesicles' ability to fuse synchronously and asynchronously in response to action potentials or spontaneously irrespective of action potentials. Here we discuss these molecular mediators of vesicle pool heterogeneity that are found on the synaptic vesicle membrane, on the presynaptic plasma membrane, or within the cytosol and consider some of the functional consequences of this diversity. This emerging molecular framework presents novel avenues to probe synaptic function and uncover how synaptic vesicle pools impact neuronal signaling. PMID:25620674

  17. Molecular Underpinnings of Synaptic Vesicle Pool Heterogeneity

    PubMed Central

    Crawford, Devon C.; Kavalali, Ege T.

    2015-01-01

    Neuronal communication relies on chemical synaptic transmission for information transfer and processing. Chemical neurotransmission is initiated by synaptic vesicle fusion with the presynaptic active zone resulting in release of neurotransmitters. Classical models have assumed that all synaptic vesicles within a synapse have the same potential to fuse under different functional contexts. In this model, functional differences among synaptic vesicle populations are ascribed to their spatial distribution in the synapse with respect to the active zone. Emerging evidence suggests, however, that synaptic vesicles are not a homogenous population of organelles, and they possess intrinsic molecular differences and differential interaction partners. Recent studies have reported a diverse array of synaptic molecules that selectively regulate synaptic vesicles' ability to fuse synchronously and asynchronously in response to action potentials or spontaneously irrespective of action potentials. Here we discuss these molecular mediators of vesicle pool heterogeneity that are found on the synaptic vesicle membrane, on the presynaptic plasma membrane, or within the cytosol and consider some of the functional consequences of this diversity. This emerging molecular framework presents novel avenues to probe synaptic function and uncover how synaptic vesicle pools impact neuronal signaling. PMID:25620674

  18. Modulation of Synaptic Plasticity by Glutamatergic Gliotransmission: A Modeling Study

    PubMed Central

    De Pittà, Maurizio; Brunel, Nicolas

    2016-01-01

    Glutamatergic gliotransmission, that is, the release of glutamate from perisynaptic astrocyte processes in an activity-dependent manner, has emerged as a potentially crucial signaling pathway for regulation of synaptic plasticity, yet its modes of expression and function in vivo remain unclear. Here, we focus on two experimentally well-identified gliotransmitter pathways, (i) modulations of synaptic release and (ii) postsynaptic slow inward currents mediated by glutamate released from astrocytes, and investigate their possible functional relevance on synaptic plasticity in a biophysical model of an astrocyte-regulated synapse. Our model predicts that both pathways could profoundly affect both short- and long-term plasticity. In particular, activity-dependent glutamate release from astrocytes could dramatically change spike-timing-dependent plasticity, turning potentiation into depression (and vice versa) for the same induction protocol. PMID:27195153

  19. Structural mechanism of glutamate receptor activation and desensitization.

    PubMed

    Meyerson, Joel R; Kumar, Janesh; Chittori, Sagar; Rao, Prashant; Pierson, Jason; Bartesaghi, Alberto; Mayer, Mark L; Subramaniam, Sriram

    2014-10-16

    Ionotropic glutamate receptors are ligand-gated ion channels that mediate excitatory synaptic transmission in the vertebrate brain. To gain a better understanding of how structural changes gate ion flux across the membrane, we trapped rat AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) and kainate receptor subtypes in their major functional states and analysed the resulting structures using cryo-electron microscopy. We show that transition to the active state involves a 'corkscrew' motion of the receptor assembly, driven by closure of the ligand-binding domain. Desensitization is accompanied by disruption of the amino-terminal domain tetramer in AMPA, but not kainate, receptors with a two-fold to four-fold symmetry transition in the ligand-binding domains in both subtypes. The 7.6 Å structure of a desensitized kainate receptor shows how these changes accommodate channel closing. These findings integrate previous physiological, biochemical and structural analyses of glutamate receptors and provide a molecular explanation for key steps in receptor gating. PMID:25119039

  20. S-palmitoylation regulates AMPA receptors trafficking and function: a novel insight into synaptic regulation and therapeutics

    PubMed Central

    Han, Jun; Wu, Pengfei; Wang, Fang; Chen, Jianguo

    2014-01-01

    Glutamate acting on AMPA-type ionotropic glutamate receptor (AMPAR) mediates the majority of fast excitatory synaptic transmission in the mammalian central nervous system. Dynamic regulation of AMPAR by post-translational modifications is one of the key elements that allow the nervous system to adapt to environment stimulations. S-palmitoylation, an important lipid modification by post-translational addition of a long-chain fatty acid to a cysteine residue, regulates AMPA receptor trafficking, which dynamically affects multiple fundamental brain functions, such as learning and memory. In vivo, S-palmitoylation is controlled by palmitoyl acyl transferases and palmitoyl thioesterases. In this review, we highlight advances in the mechanisms for dynamic AMPA receptors palmitoylation, and discuss how palmitoylation affects AMPA receptors function at synapses in recent years. Pharmacological regulation of S-palmitoylation may serve as a novel therapeutic strategy for neurobiological diseases. PMID:26579419

  1. Diacylglycerol Kinases in the Coordination of Synaptic Plasticity

    PubMed Central

    Lee, Dongwon; Kim, Eunjoon; Tanaka-Yamamoto, Keiko

    2016-01-01

    Synaptic plasticity is activity-dependent modification of the efficacy of synaptic transmission. Although, detailed mechanisms underlying synaptic plasticity are diverse and vary at different types of synapses, diacylglycerol (DAG)-associated signaling has been considered as an important regulator of many forms of synaptic plasticity, including long-term potentiation (LTP) and long-term depression (LTD). Recent evidences indicate that DAG kinases (DGKs), which phosphorylate DAG to phosphatidic acid to terminate DAG signaling, are important regulators of LTP and LTD, as supported by the results from mice lacking specific DGK isoforms. This review will summarize these studies and discuss how specific DGK isoforms distinctly regulate different forms of synaptic plasticity at pre- and postsynaptic sites. In addition, we propose a general role of DGKs as coordinators of synaptic plasticity that make local synaptic environments more permissive for synaptic plasticity by regulating DAG concentration and interacting with other synaptic proteins.

  2. Classification: Molecular & Synaptic Mechanisms

    PubMed Central

    Lussier, Marc P.; Gu, Xinglong; Lu, Wei; Roche, Katherine W.

    2014-01-01

    Controlling the density of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) at synapses is essential for regulating the strength of excitatory neurotransmission. In particular, the phosphorylation of AMPARs is important for defining both synaptic expression and intracellular routing of receptors. Phosphorylation is a posttranslational modification known to regulate many cellular events and the C-termini of glutamate receptors are important targets. Recently, the first intracellular loop1 region of the GluA1 subunit of AMPARs was reported to regulate synaptic targeting through phosphorylation of S567 by Ca2+/calmodulin-dependent protein kinase II (CaMKII). Intriguingly, the loop1 region of all four AMPAR subunits contains many putative phosphorylation sites (S/T/Y), leaving the possibility that other kinases may regulate AMPAR surface expression via phosphorylation of the loop regions. To explore this hypothesis, we used in vitro phosphorylation assays with a small panel of purified kinases and found that casein kinase 2 (CK2) phosphorylates the GluA1 and GluA2 loop1 regions, but not GluA3 or GluA4. Interestingly, when we reduced the endogenous expression of CK2 using a specific shRNA against the regulatory subunit CK2β, we detected a reduction of GluA1 surface expression, whereas GluA2 was unchanged. Furthermore, we identified S579 of GluA1 as a substrate of CK2, and the expression of GluA1 phospho-deficient mutants in hippocampal neurons displayed reduced surface expression. Therefore, our study identifies CK2 as a regulator of GluA1 surface expression by phosphorylating the intracellular loop1 region. PMID:24712994

  3. Synaptic Control of Motoneuronal Excitability

    PubMed Central

    Rekling, Jens C.; Funk, Gregory D.; Bayliss, Douglas A.; Dong, Xiao-Wei; Feldman, Jack L.

    2016-01-01

    Movement, the fundamental component of behavior and the principal extrinsic action of the brain, is produced when skeletal muscles contract and relax in response to patterns of action potentials generated by motoneurons. The processes that determine the firing behavior of motoneurons are therefore important in understanding the transformation of neural activity to motor behavior. Here, we review recent studies on the control of motoneuronal excitability, focusing on synaptic and cellular properties. We first present a background description of motoneurons: their development, anatomical organization, and membrane properties, both passive and active. We then describe the general anatomical organization of synaptic input to motoneurons, followed by a description of the major transmitter systems that affect motoneuronal excitability, including ligands, receptor distribution, pre- and postsynaptic actions, signal transduction, and functional role. Glutamate is the main excitatory, and GABA and glycine are the main inhibitory transmitters acting through ionotropic receptors. These amino acids signal the principal motor commands from peripheral, spinal, and supraspinal structures. Amines, such as serotonin and norepinephrine, and neuropeptides, as well as the glutamate and GABA acting at metabotropic receptors, modulate motoneuronal excitability through pre- and postsynaptic actions. Acting principally via second messenger systems, their actions converge on common effectors, e.g., leak K+ current, cationic inward current, hyperpolarization-activated inward current, Ca2+ channels, or presynaptic release processes. Together, these numerous inputs mediate and modify incoming motor commands, ultimately generating the coordinated firing patterns that underlie muscle contractions during motor behavior. PMID:10747207

  4. Minocycline enhances inhibitory transmission to substantia gelatinosa neurons of the rat spinal dorsal horn.

    PubMed

    Peng, H-Z; Ma, L-X; Lv, M-H; Hu, T; Liu, T

    2016-04-01

    Minocycline, a second-generation tetracycline, is well known for its antibiotic, anti-inflammatory, and antinociceptive effects. Modulation of synaptic transmission is one of the analgesic mechanisms of minocycline. Although it has been reported that minocycline may suppress excitatory glutamatergic synaptic transmission, it remains unclear whether it could affect inhibitory synaptic transmission, which also plays a key role in modulating pain signaling. To examine the effect of minocycline on synaptic transmission in rat spinal substantia gelatinosa (SG) neurons, we recorded spontaneous inhibitory postsynaptic currents (sIPSCs) using whole-cell patch-clamp recording at a holding potential of 0 mV. Bath application of minocycline significantly increased the frequency but not the amplitude of sIPSCs in a reversible and concentration-dependent manner with an EC50 of 85. The enhancement of inhibitory synaptic transmission produced by minocycline was not affected by the glutamate receptor antagonists CNQX and D-APV or by the voltage-gated sodium channel blocker tetrodotoxin (TTX). Moreover, the potency of minocycline for facilitating sIPSC frequency was the same in both glycinergic and GABAergic sIPSCs without changing their decay phases. However, the facilitatory effect of minocycline on sIPSCs was eliminated in a Ca(2+)-free Krebs solution or by co-administration with calcium channel blockers. In summary, our data demonstrate that baseline inhibitory synaptic transmission in SG neurons is markedly enhanced by minocycline. This may function to decrease the excitability of SG neurons, thus leading to a modulation of nociceptive transmission. PMID:26826332

  5. CA3 Synaptic Silencing Attenuates Kainic Acid-Induced Seizures and Hippocampal Network Oscillations123

    PubMed Central

    Yu, Lily M. Y.; Wintzer, Marie E.

    2016-01-01

    Abstract Epilepsy is a neurological disorder defined by the presence of seizure activity, manifest both behaviorally and as abnormal activity in neuronal networks. An established model to study the disorder in rodents is the systemic injection of kainic acid, an excitatory neurotoxin that at low doses quickly induces behavioral and electrophysiological seizures. Although the CA3 region of the hippocampus has been suggested to be crucial for kainic acid-induced seizure, because of its strong expression of kainate glutamate receptors and its high degree of recurrent connectivity, the precise role of excitatory transmission in CA3 in the generation of seizure and the accompanying increase in neuronal oscillations remains largely untested. Here we use transgenic mice in which CA3 pyramidal cell synaptic transmission can be inducibly silenced in the adult to demonstrate CA3 excitatory output is required for both the generation of epileptiform oscillatory activity and the progression of behavioral seizures. PMID:27022627

  6. Selective Activation of Microglia Facilitates Synaptic Strength

    PubMed Central

    Clark, Anna K.; Gruber-Schoffnegger, Doris; Drdla-Schutting, Ruth; Gerhold, Katharina J.; Malcangio, Marzia

    2015-01-01

    Synaptic plasticity is thought to be initiated by neurons only, with the prevailing view assigning glial cells mere specify supportive functions for synaptic transmission and plasticity. We now demonstrate that glial cells can control synaptic strength independent of neuronal activity. Here we show that selective activation of microglia in the rat is sufficient to rapidly facilitate synaptic strength between primary afferent C-fibers and lamina I neurons, the first synaptic relay in the nociceptive pathway. Specifically, the activation of the CX3CR1 receptor by fractalkine induces the release of interleukin-1β from microglia, which modulates NMDA signaling in postsynaptic neurons, leading to the release of an eicosanoid messenger, which ultimately enhances presynaptic neurotransmitter release. In contrast to the conventional view, this form of plasticity does not require enhanced neuronal activity to trigger the events leading to synaptic facilitation. Augmentation of synaptic strength in nociceptive pathways represents a cellular model of pain amplification. The present data thus suggest that, under chronic pain states, CX3CR1-mediated activation of microglia drives the facilitation of excitatory synaptic transmission in the dorsal horn, which contributes to pain hypersensitivity in chronic pain states. PMID:25788673

  7. Neurotoxic Potential of Lunar and Martian Dust: Influence on Em, Proton Gradient, Active Transport, and Binding of Glutamate in Rat Brain Nerve Terminals

    PubMed Central

    Krisanova, Natalia; Kasatkina, Ludmila; Sivko, Roman; Borysov, Arseniy; Nazarova, Anastasiya; Slenzka, Klaus; Borisova, Tatiana

    2013-01-01

    Abstract The harmful effects of lunar dust (LD) on directly exposed tissues are documented in the literature, whereas researchers are only recently beginning to consider its effects on indirectly exposed tissues. During inhalation, nano-/microsized particles are efficiently deposited in nasal, tracheobronchial, and alveolar regions and transported to the central nervous system. The neurotoxic potential of LD and martian dust (MD) has not yet been assessed. Glutamate is the main excitatory neurotransmitter involved in most aspects of normal brain function, whereas disturbances in glutamate homeostasis contribute to the pathogenesis of major neurological disorders. The research was focused on the analysis of the effects of LD/MD simulants (JSC-1a/JSC, derived from volcanic ash) on the key characteristics of glutamatergic neurotransmission. The average size of LD and MD particles (even minor fractions) before and after sonication was determined by dynamic light scattering. With the use of radiolabeled l-[14C]glutamate, it was shown that there is an increase in l-[14C]glutamate binding to isolated rat brain nerve terminals (synaptosomes) in low [Na+] media and at low temperature in the presence of LD. MD caused significantly lesser changes under the same conditions, whereas nanoparticles of magnetite had no effect at all. Fluorimetric experiments with potential-sensitive dye rhodamine 6G and pH-sensitive dye acridine orange showed that the potential of the plasma membrane of the nerve terminals and acidification of synaptic vesicles were not altered by LD/MD (and nanoparticles of magnetite). Thus, the unique effect of LD to increase glutamate binding to the nerve terminals was shown. This can have deleterious effects on extracellular glutamate homeostasis in the central nervous system and cause alterations in the ambient level of glutamate, which is extremely important for proper synaptic transmission. During a long-term mission, a combination of constant irritation

  8. A Model of Bidirectional Synaptic Plasticity: From Signaling Network to Channel Conductance

    ERIC Educational Resources Information Center

    Castellani, Gastone C.; Quinlan, Elizabeth M.; Bersani, Ferdinando; Cooper, Leon N.; Shouval, Harel Z.

    2005-01-01

    In many regions of the brain, including the mammalian cortex, the strength of synaptic transmission can be bidirectionally regulated by cortical activity (synaptic plasticity). One line of evidence indicates that long-term synaptic potentiation (LTP) and long-term synaptic depression (LTD), correlate with the phosphorylation/dephosphorylation of…

  9. Synaptic plasticity and phosphorylation

    PubMed Central

    Lee, Hey-Kyoung

    2009-01-01

    A number of neuronal functions, including synaptic plasticity, depend on proper regulation of synaptic proteins, many of which can be rapidly regulated by phosphorylation. Neuronal activity controls the function of these synaptic proteins by exquisitely regulating the balance of various protein kinase and protein phosphatase activity. Recent understanding of synaptic plasticity mechanisms underscores important roles that these synaptic phosphoproteins play in regulating both pre- and post-synaptic functions. This review will focus on key postsynaptic phosphoproteins that have been implicated to play a role in synaptic plasticity. PMID:16904750

  10. Injury-specific functional alteration of N-type voltage-gated calcium channels in synaptic transmission of primary afferent C-fibers in the rat spinal superficial dorsal horn.

    PubMed

    Takasu, Keiko; Ogawa, Koichi; Minami, Kazuhisa; Shinohara, Shunji; Kato, Akira

    2016-02-01

    We investigated functional alterations of voltage-gated calcium channels (VGCCs) in excitatory synaptic transmission from primary afferent A- and C-fibers after peripheral nerve injury. Patch-clamp recordings were performed on substantia gelatinosa (SG) neurons of spinal cord slices with an attached dorsal root, prepared from L5 spinal nerve-ligated (SNL) rats. The effects of neuronal VGCC blockers, ω-conotoxin GVIA (ω-CgTX) for N-type channels and ω-agatoxin IVA (ω-AgaIVA) for P/Q-type channels, on evoked excitatory postsynaptic currents (eEPSCs) by stimulation of A- or C-fibers were studied. Besides, electrophysiological assay using dorsal root ganglion (DRG) and immunohistochemistry were done. In naïve rats, ω-CgTX (0.1-1μM) reduced more effectively A-fiber eEPSCs than C-fiber ones. After nerve injury, ω-CgTX produced great inhibition of C-fiber eEPSCs in slices with the injured L5 dorsal root of SNL model rats, as compared to sham-operated rats. By contrast, in slices with the non-injured L4 one, inhibitory effects of ω-CgTX were not changed. This occurred concurrently with increased expression of N-type VGCCs in L5 spinal dorsal horn and with enhanced Ca(2+) currents through N-type VGCCs in small-sized (C-type) L5 DRG. In terms of A-fiber eEPSCs, ω-CgTX elicited similar inhibition in nerve-injured and sham-operated rats. ω-AgaIVA (0.1μM) had less effect on A- or C-fiber eEPSCs. These results indicate that N-type, but not P/Q-type, VGCCs mainly contribute to excitatory synaptic transmission from A- and C-fibers in the spinal dorsal horn. More importantly, following nerve injury, the functional contribution of N-type VGCCs to nociceptive transmission is increased in the pre-synaptic terminals of injured C-fibers. PMID:26708163

  11. Convergence of dopamine and glutamate signaling onto striatal ERK activation in response to drugs of abuse

    PubMed Central

    Cahill, Emma; Salery, Marine; Vanhoutte, Peter; Caboche, Jocelyne

    2014-01-01

    Despite their distinct targets, all addictive drugs commonly abused by humans evoke increases in dopamine (DA) concentration within the striatum. The main DA Guanine nucleotide binding protein couple receptors (GPCRs) expressed by medium-sized spiny neurons of the striatum are the D1R and D2R, which are positively and negatively coupled to cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) signaling, respectively. These two DA GPCRs are largely segregated into distinct neuronal populations, where they are co-expressed with glutamate receptors in dendritic spines. Direct and indirect interactions between DA GPCRs and glutamate receptors are the molecular basis by which DA modulates glutamate transmission and controls striatal plasticity and behavior induced by drugs of abuse. A major downstream target of striatal D1R is the extracellular signal-regulated kinase (ERK) kinase pathway. ERK activation by drugs of abuse behaves as a key integrator of D1R and glutamate NMDAR signaling. Once activated, ERK can trigger chromatin remodeling and induce gene expression that permits long-term cellular alterations and drug-induced morphological and behavioral changes. Besides the classical cAMP/PKA pathway, downstream of D1R, recent evidence implicates a cAMP-independent crosstalk mechanism by which the D1R potentiates NMDAR-mediated calcium influx and ERK activation. The mounting evidence of reciprocal modulation of DA and glutamate receptors adds further intricacy to striatal synaptic signaling and is liable to prove relevant for addictive drug-induced signaling, plasticity, and behavior. Herein, we review the evidence that built our understanding of the consequences of this synergistic signaling for the actions of drugs of abuse. PMID:24409148

  12. CRF-R2 and the heterosynaptic regulation of VTA glutamate during reinstatement of cocaine seeking.

    PubMed

    Williams, Courtney L; Buchta, William C; Riegel, Arthur C

    2014-07-30

    Stress can reinstate cocaine seeking through an interaction between the stress hormone corticotropin releasing factor (CRF) and glutamate release onto dopamine neurons in the ventral tegmental area (VTA). To better understand the underlying causes, synaptic mechanisms were investigated in brain slices from rats. In control tissue, EPSCs displayed concentration-dependent, bimodal responses to CRF potentiation at low concentrations (3-100 nm) and attenuation at higher concentrations (300 nm). EPSC potentiation and attenuation were mediated by CRF-R1 and CRF-R2 receptor subtypes, respectively, localized to presynaptic terminals. The CRF-R2 attenuation was blocked by the GABA-B receptor antagonist CGP55843. Additional recordings of GABA-A IPSCs showed CRF-R2 activation-facilitated presynaptic release of GABA, suggesting that CRF-R2 may regulate glutamate release via heterosynaptic facilitation of GABA synapses. After chronic cocaine self-administration and extinction training, the sensitivity of glutamate and GABA receptors was unchanged. However, the ability of CRF-R2 agonists to depress EPSCs and potentiate IPSCs was diminished. After yohimbine plus cue reinstatement, the actions of CRF-R2 on GABA and glutamate release were reversed. CRF-R2 activation increased EPSCs as a result of a reduction of tonic GABA-dependent inhibition. After reinstatement, application of the A1 adenosine antagonist 1,3-dipropyl-8-cyclopentylxanthine increased GABA tone to inhibit the CRF-R2 action. Blockade of GABA-B receptors prevented both the CRF-R2 increase in EPSCs and the attenuation produced by 1,3-dipropyl-8-cyclopentylxanthine. These studies demonstrate that presynaptic CRF-R1/R2 tightly regulate glutamate transmission in the VTA via a concerted, heterosynaptic manner that may become altered by stress-related pathologies, such as addiction. PMID:25080599

  13. Modulation of the glutamatergic transmission by Dopamine: a focus on Parkinson, Huntington and Addiction diseases

    PubMed Central

    Gardoni, Fabrizio; Bellone, Camilla

    2015-01-01

    Dopamine (DA) plays a major role in motor and cognitive functions as well as in reward processing by regulating glutamatergic inputs. In particular in the striatum the release of DA rapidly influences synaptic transmission modulating both AMPA and NMDA receptors. Several neurodegenerative and neuropsychiatric disorders, including Parkinson, Huntington and addiction-related diseases, manifest a dysregulation of glutamate and DA signaling. Here, we will focus our attention on the mechanisms underlying the modulation of the glutamatergic transmission by DA in striatal circuits. PMID:25784855

  14. Oligomeric Aβ-induced synaptic dysfunction in Alzheimer's disease.

    PubMed

    Tu, Shichun; Okamoto, Shu-ichi; Lipton, Stuart A; Xu, Huaxi

    2014-01-01

    Alzheimer's disease (AD) is a devastating disease characterized by synaptic and neuronal loss in the elderly. Compelling evidence suggests that soluble amyloid-β peptide (Aβ) oligomers induce synaptic loss in AD. Aβ-induced synaptic dysfunction is dependent on overstimulation of N-methyl-D-aspartate receptors (NMDARs) resulting in aberrant activation of redox-mediated events as well as elevation of cytoplasmic Ca2+, which in turn triggers downstream pathways involving phospho-tau (p-tau), caspases, Cdk5/dynamin-related protein 1 (Drp1), calcineurin/PP2B, PP2A, Gsk-3β, Fyn, cofilin, and CaMKII and causes endocytosis of AMPA receptors (AMPARs) as well as NMDARs. Dysfunction in these pathways leads to mitochondrial dysfunction, bioenergetic compromise and consequent synaptic dysfunction and loss, impaired long-term potentiation (LTP), and cognitive decline. Evidence also suggests that Aβ may, at least in part, mediate these events by causing an aberrant rise in extrasynaptic glutamate levels by inhibiting glutamate uptake or triggering glutamate release from glial cells. Consequent extrasynaptic NMDAR (eNMDAR) overstimulation then results in synaptic dysfunction via the aforementioned pathways. Consistent with this model of Aβ-induced synaptic loss, Aβ synaptic toxicity can be partially ameliorated by the NMDAR antagonists (such as memantine and NitroMemantine). PSD-95, an important scaffolding protein that regulates synaptic distribution and activity of both NMDA and AMPA receptors, is also functionally disrupted by Aβ. PSD-95 dysregulation is likely an important intermediate step in the pathological cascade of events caused by Aβ. In summary, Aβ-induced synaptic dysfunction is a complicated process involving multiple pathways, components and biological events, and their underlying mechanisms, albeit as yet incompletely understood, may offer hope for new therapeutic avenues. PMID:25394486

  15. Depletion of the AMPAR reserve pool impairs synaptic plasticity in a model of hepatic encephalopathy.

    PubMed

    Schroeter, Annett; Wen, Shuping; Mölders, Andrea; Erlenhardt, Nadine; Stein, Valentin; Klöcker, Nikolaj

    2015-09-01

    Hepatic encephalopathy (HE) is the most common neuropsychiatric complication of acute or chronic liver failure. Clinical symptoms include cognitive and intellectual dysfunction as well as impaired motor activity and coordination. There is general consensus that increased levels of ammonia play a central role in the pathogenesis of HE. However, it is still elusive how cognitive performance including the ability to learn and memorize information is affected by ammonia at molecular levels. In the present study, we have employed a neuroglial co-culture model, which preserves neuroglial interplay but allows for cell-type specific molecular and functional analyses, to investigate glutamatergic neurotransmission under conditions of high ammonia. Chronic exposure to ammonia significantly reduced neuronal mRNA and protein expression of AMPA-subtype glutamate receptors (AMPARs), which mediate most fast excitatory neurotransmission in the brain. Surprisingly, neurons were able to fully maintain basal glutamatergic neurotransmission as recorded by AMPAR-mediated miniature excitatory postsynaptic currents (mEPSCs) even when >50% of total AMPARs were lost. However, long-lasting, activity-dependent changes in the efficacy of synaptic communication, which model the capability of the brain to learn and store information, were severely constrained. Whereas synaptic efficacy could still be depressed, an increase in synaptic strength was abolished. We conclude that neurons retain basal glutamatergic transmission at the expense of the extrasynaptic population of AMPARs, which is revealed when the extrasynaptic reserve pool is recruited in vain for synaptic potentiation. Our findings thus offer a molecular model, which might not only explain impaired synaptic plasticity in HE but also in other neurological diseases accompanied by a decrease in extrasynaptic AMPAR expression. PMID:26363416

  16. Membrane palmitoylated protein 2 is a synaptic scaffold protein required for synaptic SK2-containing channel function

    PubMed Central

    Kim, Gukhan; Luján, Rafael; Schwenk, Jochen; Kelley, Melissa H; Aguado, Carolina; Watanabe, Masahiko; Fakler, Bernd; Maylie, James; Adelman, John P

    2016-01-01

    Mouse CA1 pyramidal neurons express apamin-sensitive SK2-containing channels in the post-synaptic membrane, positioned close to NMDA-type (N-methyl-D-aspartate) glutamate receptors. Activated by synaptically evoked NMDAR-dependent Ca2+ influx, the synaptic SK2-containing channels modulate excitatory post-synaptic responses and the induction of synaptic plasticity. In addition, their activity- and protein kinase A-dependent trafficking contributes to expression of long-term potentiation (LTP). We have identified a novel synaptic scaffold, MPP2 (membrane palmitoylated protein 2; p55), a member of the membrane-associated guanylate kinase (MAGUK) family that interacts with SK2-containing channels. MPP2 and SK2 co-immunopurified from mouse brain, and co-immunoprecipitated when they were co-expressed in HEK293 cells. MPP2 is highly expressed in the post-synaptic density of dendritic spines on CA1 pyramidal neurons. Knocking down MPP2 expression selectively abolished the SK2-containing channel contribution to synaptic responses and decreased LTP. Thus, MPP2 is a novel synaptic scaffold that is required for proper synaptic localization and function of SK2-containing channels. DOI: http://dx.doi.org/10.7554/eLife.12637.001 PMID:26880549

  17. NMDA Receptors Mediate Synaptic Competition in Culture

    PubMed Central

    She, Kevin; Craig, Ann Marie

    2011-01-01

    Background Activity through NMDA type glutamate receptors sculpts connectivity in the developing nervous system. This topic is typically studied in the visual system in vivo, where activity of inputs can be differentially regulated, but in which individual synapses are difficult to visualize and mechanisms governing synaptic competition can be difficult to ascertain. Here, we develop a model of NMDA-receptor dependent synaptic competition in dissociated cultured hippocampal neurons. Methodology/Principal Findings GluN1 -/- (KO) mouse hippocampal neurons lacking the essential NMDA receptor subunit were cultured alone or cultured in defined ratios with wild type (WT) neurons. The absence of functional NMDA receptors did not alter neuron survival. Synapse development was assessed by immunofluorescence for postsynaptic PSD-95 family scaffold and apposed presynaptic vesicular glutamate transporter VGlut1. Synapse density was specifically enhanced onto minority wild type neurons co-cultured with a majority of GluN1 -/- neighbour neurons, both relative to the GluN1 -/- neighbours and relative to sister pure wild type cultures. This form of synaptic competition was dependent on NMDA receptor activity and not conferred by the mere physical presence of GluN1. In contrast to these results in 10% WT and 90% KO co-cultures, synapse density did not differ by genotype in 50% WT and 50% KO co-cultures or in 90% WT and 10% KO co-cultures. Conclusions/Significance The enhanced synaptic density onto NMDA receptor-competent neurons in minority coculture with GluN1 -/- neurons represents a cell culture paradigm for studying synaptic competition. Mechanisms involved may include a retrograde ‘reward’ signal generated by WT neurons, although in this paradigm there was no ‘punishment’ signal against GluN1 -/- neurons. Cell culture assays involving such defined circuits may help uncover the rules and mechanisms of activity-dependent synaptic competition in the developing nervous

  18. Topoisomerase 1 inhibition reversibly impairs synaptic function

    PubMed Central

    Mabb, Angela M.; Kullmann, Paul H. M.; Twomey, Margaret A.; Miriyala, Jayalakshmi; Philpot, Benjamin D.; Zylka, Mark J.

    2014-01-01

    Topotecan is a topoisomerase 1 (TOP1) inhibitor that is used to treat various forms of cancer. We recently found that topotecan reduces the expression of multiple long genes, including many neuronal genes linked to synapses and autism. However, whether topotecan alters synaptic protein levels and synapse function is currently unknown. Here we report that in primary cortical neurons, topotecan depleted synaptic proteins that are encoded by extremely long genes, including Neurexin-1, Neuroligin-1, Cntnap2, and GABAAβ3. Topotecan also suppressed spontaneous network activity without affecting resting membrane potential, action potential threshold, or neuron health. Topotecan strongly suppressed inhibitory neurotransmission via pre- and postsynaptic mechanisms and reduced excitatory neurotransmission. The effects on synaptic protein levels and inhibitory neurotransmission were fully reversible upon drug washout. Collectively, our findings suggest that TOP1 controls the levels of multiple synaptic proteins and is required for normal excitatory and inhibitory synaptic transmission. PMID:25404338

  19. The Nucleus Accumbens: Mechanisms of Addiction across Drug Classes Reflect the Importance of Glutamate Homeostasis.

    PubMed

    Scofield, M D; Heinsbroek, J A; Gipson, C D; Kupchik, Y M; Spencer, S; Smith, A C W; Roberts-Wolfe, D; Kalivas, P W

    2016-07-01

    The nucleus accumbens is a major input structure of the basal ganglia and integrates information from cortical and limbic structures to mediate goal-directed behaviors. Chronic exposure to several classes of drugs of abuse disrupts plasticity in this region, allowing drug-associated cues to engender a pathologic motivation for drug seeking. A number of alterations in glutamatergic transmission occur within the nucleus accumbens after withdrawal from chronic drug exposure. These drug-induced neuroadaptations serve as the molecular basis for relapse vulnerability. In this review, we focus on the role that glutamate signal transduction in the nucleus accumbens plays in addiction-related behaviors. First, we explore the nucleus accumbens, including the cell types and neuronal populations present as well as afferent and efferent connections. Next we discuss rodent models of addiction and assess the viability of these models for testing candidate pharmacotherapies for the prevention of relapse. Then we provide a review of the literature describing how synaptic plasticity in the accumbens is altered after exposure to drugs of abuse and withdrawal and also how pharmacological manipulation of glutamate systems in the accumbens can inhibit drug seeking in the laboratory setting. Finally, we examine results from clinical trials in which pharmacotherapies designed to manipulate glutamate systems have been effective in treating relapse in human patients. Further elucidation of how drugs of abuse alter glutamatergic plasticity within the accumbens will be necessary for the development of new therapeutics for the treatment of addiction across all classes of addictive substances. PMID:27363441

  20. Metabotropic glutamate receptors are required for the induction of long-term potentiation

    NASA Technical Reports Server (NTRS)

    Zheng, F.; Gallagher, J. P.

    1992-01-01

    Recent observations have led to the suggestion that the metabotropic glutamate receptor may play a role in the induction or maintenance of long-term potentiation (LTP). However, experimental evidence supporting a role for this receptor in the induction of LTP is still inconclusive and controversial. Here we report that, in rat dorsolateral septal nucleus (DLSN) neurons, which have the highest density of metabotropic receptors and show functional responses, the induction of LTP is not blocked by the NMDA receptor antagonist 2-amino-5-phosphonovalerate, but is blocked by two putative metabotropic glutamate receptor antagonists, L-2-amino-3-phosphonopropionic acid and L-2-amino-4-phosphonobutyrate. Furthermore, superfusion of (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid, a selective metabotropic glutamate agonist, resulted in a long-lasting potentiation of synaptic transmission similar to that induced by tetanic stimuli. Our results demonstrated that activation of postsynaptic metabotropic receptors is both necessary and sufficient for the induction of LTP in the DLSN, and we suggest that such a mechanism may be important at other CNS synapses.

  1. Phosphorylation and Assembly of Glutamate Receptors after Brain Ischemia

    PubMed Central

    Zhang, Fan; Guo, Ailan; Liu, Chunli; Comb, Micheal; Hu, Bingren

    2012-01-01

    Background and Purpose Over-assembly of synaptic glutamate receptors leads to excitotoxicity. The goal of this study is to investigate phosphorylation and assembly of AMPA and NMDA receptors after brain ischemia with reperfusion (I/R). Methods Rats were subjected to 15 min of global ischemia followed by 0.5, 4, and 24 h of reperfusion. Phosphotyrosine (Ptyr) peptides of glutamate receptors in synaptosomal fraction after I/R were identified and quantified by state-of-the-art immuno-affinity purification of Ptyr peptides followed by LC-MS/MS analysis (IAP-LC/MS/MS). Glutamate receptor phosphorylation and synaptic assembly after I/R were studied by biochemical methods. Results Numerous Ptyr sites of AMPA and NMDA were upregulated by about 2- to 37-fold after I/R. A core glutamate receptor kinase, Src kinase, was significantly activated. GluR2/3 and NR2A/B were rapidly clustered from extrasynaptic to synaptic membrane fractions after I/R. GluR2/3 was then translocated into the intracellular pool, whereas NR2A/B remained in the synaptic fraction for as long as 24 h. Consistently, trafficking-related phosphorylation of GluR2/3-S880 was significantly but transiently upregulated, whereas NR2A/B-Y1246 and -Y1472 were significantly and persistently upregulated after I/R. Conclusions Phosphorylation of glutamate receptors at synapses may lead to over-assembly of glutamate receptors, probably via activation of Src family kinases, after I/R. This study provides “global” proteomic information about glutamate receptor tyrosine phosphorylation after brain ischemia. PMID:23212166

  2. Potential of Glutamate-Based Drug Discovery for Next Generation Antidepressants

    PubMed Central

    Chaki, Shigeyuki; Fukumoto, Kenichi

    2015-01-01

    Recently, ketamine has been demonstrated to exert rapid-acting antidepressant effects in patients with depression, including those with treatment-resistant depression, and this discovery has been regarded as the most significant advance in drug development for the treatment of depression in over 50 years. To overcome unwanted side effects of ketamine, numerous approaches targeting glutamatergic systems have been vigorously investigated. For example, among agents targeting the NMDA receptor, the efficacies of selective GluN2B receptor antagonists and a low-trapping antagonist, as well as glycine site modulators such as GLYX-13 and sarcosine have been demonstrated clinically. Moreover, agents acting on metabotropic glutamate receptors, such as mGlu2/3 and mGlu5 receptors, have been proposed as useful approaches to mimicking the antidepressant effects of ketamine. Neural and synaptic mechanisms mediated through the antidepressant effects of ketamine have been being delineated, most of which indicate that ketamine improves abnormalities in synaptic transmission and connectivity observed in depressive states via the AMPA receptor and brain-derived neurotrophic factor-dependent mechanisms. Interestingly, some of the above agents may share some neural and synaptic mechanisms with ketamine. These studies should provide important insights for the development of superior pharmacotherapies for depression with more potent and faster onsets of actions. PMID:26393618

  3. Pituitary Adenylate cyclase-activating polypeptide orchestrates neuronal regulation of the astrocytic glutamate-releasing mechanism system xc (.).

    PubMed

    Kong, Linghai; Albano, Rebecca; Madayag, Aric; Raddatz, Nicholas; Mantsch, John R; Choi, SuJean; Lobner, Doug; Baker, David A

    2016-05-01

    Glutamate signaling is achieved by an elaborate network involving neurons and astrocytes. Hence, it is critical to better understand how neurons and astrocytes interact to coordinate the cellular regulation of glutamate signaling. In these studies, we used rat cortical cell cultures to examine whether neurons or releasable neuronal factors were capable of regulating system xc (-) (Sxc), a glutamate-releasing mechanism that is expressed primarily by astrocytes and has been shown to regulate synaptic transmission. We found that astrocytes cultured with neurons or exposed to neuronal-conditioned media displayed significantly higher levels of Sxc activity. Next, we demonstrated that the pituitary adenylate cyclase-activating polypeptide (PACAP) may be a neuronal factor capable of regulating astrocytes. In support, we found that PACAP expression was restricted to neurons, and that PACAP receptors were expressed in astrocytes. Interestingly, blockade of PACAP receptors in cultures comprised of astrocytes and neurons significantly decreased Sxc activity to the level observed in purified astrocytes, whereas application of PACAP to purified astrocytes increased Sxc activity to the level observed in cultures comprised of neurons and astrocytes. Collectively, these data reveal that neurons coordinate the actions of glutamate-related mechanisms expressed by astrocytes, such as Sxc, a process that likely involves PACAP. A critical gap in modeling excitatory signaling is how distinct components of the glutamate system expressed by neurons and astrocytes are coordinated. In these studies, we found that system xc (-) (Sxc), a glutamate release mechanism expressed by astrocytes, is regulated by releasable neuronal factors including PACAP. This represents a novel form of neuron-astrocyte communication, and highlights the possibility that pathological changes involving astrocytic Sxc may stem from altered neuronal activity. PMID:26851652

  4. Glutamate: Tastant and Neuromodulator in Taste Buds.

    PubMed

    Vandenbeuch, Aurelie; Kinnamon, Sue C

    2016-07-01

    In taste buds, glutamate plays a double role as a gustatory stimulus and neuromodulator. The detection of glutamate as a tastant involves several G protein-coupled receptors, including the heterodimer taste receptor type 1, member 1 and 3 as well as metabotropic glutamate receptors (mGluR1 and mGluR4). Both receptor types participate in the detection of glutamate as shown with knockout animals and selective antagonists. At the basal part of taste buds, ionotropic glutamate receptors [N-methyl-d-aspartate (NMDA) and non-NMDA] are expressed and participate in the modulation of the taste signal before its transmission to the brain. Evidence suggests that glutamate has an efferent function on taste cells and modulates the release of other neurotransmitters such as serotonin and ATP. This short article reviews the recent developments in the field with regard to glutamate receptors involved in both functions as well as the influence of glutamate on the taste signal. PMID:27422519

  5. ADAR-mediated RNA editing suppresses sleep by acting as a brake on glutamatergic synaptic plasticity

    PubMed Central

    Robinson, J. E.; Paluch, J.; Dickman, D. K.; Joiner, W. J.

    2016-01-01

    It has been postulated that synaptic potentiation during waking is offset by a homoeostatic reduction in net synaptic strength during sleep. However, molecular mechanisms to support such a process are lacking. Here we demonstrate that deficiencies in the RNA-editing gene Adar increase sleep due to synaptic dysfunction in glutamatergic neurons in Drosophila. Specifically, the vesicular glutamate transporter is upregulated, leading to over-activation of NMDA receptors, and the reserve pool of glutamatergic synaptic vesicles is selectively expanded in Adar mutants. Collectively these changes lead to sustained neurotransmitter release under conditions that would otherwise result in synaptic depression. We propose that a shift in the balance from synaptic depression towards synaptic potentiation in sleep-promoting neurons underlies the increased sleep pressure of Adar-deficient animals. Our findings provide a plausible molecular mechanism linking sleep and synaptic plasticity. PMID:26813350

  6. Deep mRNA Sequencing of the Tritonia diomedea Brain Transcriptome Provides Access to Gene Homologues for Neuronal Excitability, Synaptic Transmission and Peptidergic Signalling

    PubMed Central

    Senatore, Adriano; Edirisinghe, Neranjan; Katz, Paul S.

    2015-01-01

    Background The sea slug Tritonia diomedea (Mollusca, Gastropoda, Nudibranchia), has a simple and highly accessible nervous system, making it useful for studying neuronal and synaptic mechanisms underlying behavior. Although many important contributions have been made using Tritonia, until now, a lack of genetic information has impeded exploration at the molecular level. Results We performed Illumina sequencing of central nervous system mRNAs from Tritonia, generating 133.1 million 100 base pair, paired-end reads. De novo reconstruction of the RNA-Seq data yielded a total of 185,546 contigs, which partitioned into 123,154 non-redundant gene clusters (unigenes). BLAST comparison with RefSeq and Swiss-Prot protein databases, as well as mRNA data from other invertebrates (gastropod molluscs: Aplysia californica, Lymnaea stagnalis and Biomphalaria glabrata; cnidarian: Nematostella vectensis) revealed that up to 76,292 unigenes in the Tritonia transcriptome have putative homologues in other databases, 18,246 of which are below a more stringent E-value cut-off of 1x10-6. In silico prediction of secreted proteins from the Tritonia transcriptome shotgun assembly (TSA) produced a database of 579 unique sequences of secreted proteins, which also exhibited markedly higher expression levels compared to other genes in the TSA. Conclusions Our efforts greatly expand the availability of gene sequences available for Tritonia diomedea. We were able to extract full length protein sequences for most queried genes, including those involved in electrical excitability, synaptic vesicle release and neurotransmission, thus confirming that the transcriptome will serve as a useful tool for probing the molecular correlates of behavior in this species. We also generated a neurosecretome database that will serve as a useful tool for probing peptidergic signalling systems in the Tritonia brain. PMID:25719197

  7. Regulation of AMPA Receptor Trafficking and Synaptic Plasticity

    PubMed Central

    Anggono, Victor; Huganir, Richard L.

    2012-01-01

    AMPA receptors (AMPARs) mediate the majority of fast excitatory synaptic transmission in the brain. Dynamic changes in neuronal synaptic efficacy, termed synaptic plasticity, are thought to underlie information coding and storage in learning and memory. One major mechanism that regulates synaptic strength involves the tightly regulated trafficking of AMPARs into and out of synapses. The life cycle of AMPARs from their biosynthesis, membrane trafficking and synaptic targeting to their degradation are controlled by a series of orchestrated interactions with numerous intracellular regulatory proteins. Here we review recent progress made towards the understanding the regulation of AMPAR trafficking, focusing on the roles of several key intracellular AMPAR interacting proteins. PMID:22217700

  8. Location-dependent synaptic plasticity rules by dendritic spine cooperativity

    PubMed Central

    Weber, Jens P.; Andrásfalvy, Bertalan K.; Polito, Marina; Magó, Ádám; Ujfalussy, Balázs B.; Makara, Judit K.

    2016-01-01

    Nonlinear interactions between coactive synapses enable neurons to discriminate between spatiotemporal patterns of inputs. Using patterned postsynaptic stimulation by two-photon glutamate uncaging, here we investigate the sensitivity of synaptic Ca2+ signalling and long-term plasticity in individual spines to coincident activity of nearby synapses. We find a proximodistally increasing gradient of nonlinear NMDA receptor (NMDAR)-mediated amplification of spine Ca2+ signals by a few neighbouring coactive synapses along individual perisomatic dendrites. This synaptic cooperativity does not require dendritic spikes, but is correlated with dendritic Na+ spike propagation strength. Furthermore, we show that repetitive synchronous subthreshold activation of small spine clusters produces input specific, NMDAR-dependent cooperative long-term potentiation at distal but not proximal dendritic locations. The sensitive synaptic cooperativity at distal dendritic compartments shown here may promote the formation of functional synaptic clusters, which in turn can facilitate active dendritic processing and storage of information encoded in spatiotemporal synaptic activity patterns. PMID:27098773

  9. Location-dependent synaptic plasticity rules by dendritic spine cooperativity.

    PubMed

    Weber, Jens P; Andrásfalvy, Bertalan K; Polito, Marina; Magó, Ádám; Ujfalussy, Balázs B; Makara, Judit K

    2016-01-01

    Nonlinear interactions between coactive synapses enable neurons to discriminate between spatiotemporal patterns of inputs. Using patterned postsynaptic stimulation by two-photon glutamate uncaging, here we investigate the sensitivity of synaptic Ca(2+) signalling and long-term plasticity in individual spines to coincident activity of nearby synapses. We find a proximodistally increasing gradient of nonlinear NMDA receptor (NMDAR)-mediated amplification of spine Ca(2+) signals by a few neighbouring coactive synapses along individual perisomatic dendrites. This synaptic cooperativity does not require dendritic spikes, but is correlated with dendritic Na(+) spike propagation strength. Furthermore, we show that repetitive synchronous subthreshold activation of small spine clusters produces input specific, NMDAR-dependent cooperative long-term potentiation at distal but not proximal dendritic locations. The sensitive synaptic cooperativity at distal dendritic compartments shown here may promote the formation of functional synaptic clusters, which in turn can facilitate active dendritic processing and storage of information encoded in spatiotemporal synaptic activity patterns. PMID:27098773

  10. Temperature Differentially Facilitates Spontaneous but Not Evoked Glutamate Release from Cranial Visceral Primary Afferents

    PubMed Central

    Fawley, Jessica A.; Hofmann, Mackenzie E.; Largent-Milnes, Tally M.; Andresen, Michael C.

    2015-01-01

    Temperature is fundamentally important to all biological functions including synaptic glutamate release. Vagal afferents from the solitary tract (ST) synapse on second order neurons in the nucleus of the solitary tract, and glutamate release at this first central synapse controls autonomic reflex function. Expression of the temperature-sensitive Transient Receptor Potential Vanilloid Type 1 receptor separates ST afferents into C-fibers (TRPV1+) and A-fibers (TRPV1-). Action potential-evoked glutamate release is similar between C- and A-fiber afferents, but TRPV1 expression facilitates a second form of synaptic glutamate release in C-fibers by promoting substantially more spontaneous glutamate release. The influence of temperature on different forms of glutamate release is not well understood. Here we tested how temperature impacts the generation of evoked and spontaneous release of glutamate and its relation to TRPV1 expression. In horizontal brainstem slices of rats, activation of ST primary afferents generated synchronous evoked glutamate release (ST-eEPSCs) at constant latency whose amplitude reflects the probability of evoked glutamate release. The frequency of spontaneous EPSCs in these same neurons measured the probability of spontaneous glutamate release. We measured both forms of glutamate from each neuron during ramp changes in bath temperature of 4–5°C. Spontaneous glutamate release from TRPV1+ closely tracked with these thermal changes indicating changes in the probability of spontaneous glutamate release. In the same neurons, temperature changed axon conduction registered as latency shifts but ST-eEPSC amplitudes were constant and independent of TRPV1 expression. These data indicate that TRPV1-operated glutamate release is independent of action potential-evoked glutamate release in the same neurons. Together, these support the hypothesis that evoked and spontaneous glutamate release originate from two pools of vesicles that are independently

  11. Inhibition of vesicular glutamate transporters contributes to attenuate methamphetamine-induced conditioned place preference in rats.

    PubMed

    He, Zongsheng; Chen, Yuan; Dong, Huajin; Su, Ruibin; Gong, Zehui; Yan, Lingdi

    2014-07-01

    Accumulating evidence suggests that glutamatergic system plays a crucial role in methamphetamine (METH) addiction. In the glutamatergic transmission, vesicular glutamate transporters (VGLUTs) are responsible for transporting glutamate into synaptic vesicles and affect the glutamate concentrations in the synaptic cleft. It is well documented that VGLUTs play an essential role in pathophysiology of several psychiatric and neurological diseases, however, whether VGLUTs also have a role in addiction caused by psychostimulant drugs is still unknown. The present study was underwent to investigate the effect of inhibition of VGLUTs on METH-induced induce conditioned place preference in rats. Rats were induced to conditioned place preference with METH (0.5, 1.0 and 2.0mg/kg) by intraperitoneal injection. Intracerebroventricular administration of 1.0 or 5.0μg Chicago sky blue 6B (CSB6B), a VGLUTs inhibitor, and 2.5h prior to METH was to observe its effect on METH-induced conditioned place preference in rats. The rats receiving METH showed stronger place preference at the dose of 1.0mg/kg than that of other doses. The intracerebroventricular administration of CSB6B (1.0, 5.0μg) 2.5h prior to the exposure to METH attenuated the acquisition of METH-induced conditioned place preference, while CSB6B itself had no effect on place preference. These results indicate that VGLUTs are involved in the effect of METH-induced conditioned place preference and may be a new target against METH addiction. PMID:24613241

  12. Impact of Synaptic Neurotransmitter Concentration Time Course on the Kinetics and Pharmacological Modulation of Inhibitory Synaptic Currents

    PubMed Central

    Barberis, Andrea; Petrini, Enrica Maria; Mozrzymas, Jerzy W.

    2011-01-01

    The time course of synaptic currents is a crucial determinant of rapid signaling between neurons. Traditionally, the mechanisms underlying the shape of synaptic signals are classified as pre- and post-synaptic. Over the last two decades, an extensive body of evidence indicated that synaptic signals are critically shaped by the neurotransmitter time course which encompasses several phenomena including pre- and post-synaptic ones. The agonist transient depends on neurotransmitter release mechanisms, diffusion within the synaptic cleft, spill-over to the extra-synaptic space, uptake, and binding to post-synaptic receptors. Most estimates indicate that the neurotransmitter transient is very brief, lasting between one hundred up to several hundreds of microseconds, implying that post-synaptic activation is characterized by a high degree of non-equilibrium. Moreover, pharmacological studies provide evidence that the kinetics of agonist transient plays a crucial role in setting the susceptibility of synaptic currents to modulation by a variety of compounds of physiological or clinical relevance. More recently, the role of the neurotransmitter time course has been emphasized by studies carried out on brain slice models that revealed a striking, cell-dependent variability of synaptic agonist waveforms ranging from rapid pulses to slow volume transmission. In the present paper we review the advances on studies addressing the impact of synaptic neurotransmitter transient on kinetics and pharmacological modulation of synaptic currents at inhibitory synapses. PMID:21734864

  13. Coincident Glutamatergic and Cholinergic Inputs Transiently Depress Glutamate Release at Rat Schaffer Collateral Synapses

    PubMed Central

    Gipson, Keith E.; Yeckel, Mark F.

    2010-01-01

    The mammalian hippocampus, together with subcortical and cortical areas, is responsible for some forms of learning and memory. Proper hippocampal function depends on the highly dynamic nature of its circuitry, including the ability of synapses to change their strength for brief to long periods of time. In this study, we focused on a transient depression of glutamatergic synaptic transmission at Schaffer collateral synapses in acute hippocampal slices. The depression of evoked excitatory postsynaptic current (EPSC) amplitudes, herein called transient depression, follows brief trains of synaptic stimulation in stratum radiatum of CA1 and lasts for 2–3 min. Depression results from a decrease in presynaptic glutamate release, as NMDA-receptor–mediated EPSCs and composite EPSCs are depressed similarly and depression is accompanied by an increase in the paired-pulse ratio. Transient depression is prevented by blockade of metabotropic glutamate and acetylcholine receptors, presumably located presynaptically. These two receptor types—acting together— cause depression. Blockade of a single receptor type necessitates significantly stronger conditioning trains for triggering depression. Addition of an acetylcholinesterase inhibitor enables depression from previously insufficient conditioning trains. Furthermore, a strong coincident, but not causal, relationship existed between presynaptic depression and postsynaptic internal Ca2+ release, emphasizing the potential importance of functional interactions between presynaptic and postsynaptic effects of convergent cholinergic and glutamatergic inputs to CA1. These convergent afferents, one intrinsic to the hippocampus and the other likely originating in the medial septum, may regulate CA1 network activity, the induction of long-term synaptic plasticity, and ultimately hippocampal function. PMID:17303811

  14. Disorders of glutamate metabolism.

    PubMed

    Kelly, A; Stanley, C A

    2001-01-01

    The significant role the amino acid glutamate assumes in a number of fundamental metabolic pathways is becoming better understood. As a central junction for interchange of amino nitrogen, glutamate facilitates both amino acid synthesis and degradation. In the liver, glutamate is the terminus for release of ammonia from amino acids, and the intrahepatic concentration of glutamate modulates the rate of ammonia detoxification into urea. In pancreatic beta-cells, oxidation of glutamate mediates amino acid-stimulated insulin secretion. In the central nervous system, glutamate serves as an excitatory neurotransmittor. Glutamate is also the precursor of the inhibitory neurotransmittor GABA, as well as glutamine, a potential mediator of hyperammonemic neurotoxicity. The recent identification of a novel form of congenital hyperinsulinism associated with asymptomatic hyperammonemia assigns glutamate oxidation by glutamate dehydrogenase a more important role than previously recognized in beta-cell insulin secretion and hepatic and CNS ammonia detoxification. Disruptions of glutamate metabolism have been implicated in other clinical disorders, such as pyridoxine-dependent seizures, confirming the importance of intact glutamate metabolism. This article will review glutamate metabolism and clinical disorders associated with disrupted glutamate metabolism. PMID:11754524

  15. Dysregulated post-synaptic density and endocytic zone in the amygdala of human heroin and cocaine abusers

    PubMed Central

    Ökvist, Anna; Fagergren, Pernilla; Whittard, John; Garcia-Osta, Ana; Drakenberg, Katarina; Horvath, Monika Cs.; Schmidt, Carl J.; Keller, Eva; Bannon, Michael J.; Hurd, Yasmin L.

    2010-01-01

    Background Glutamatergic transmission in the amygdala is hypothesized as an important mediator of stimulus-reward associations contributing to drug-seeking behavior and relapse. Insight is, however, lacking regarding the amygdala glutamatergic system in human drug abusers. Methods We examined glutamate receptors and scaffolding proteins associated with the post-synaptic density (PSD) of excitatory synapses in the human post-mortem amygdala. mRNA or protein levels were studied in a multi-drug (7 heroin, 8 cocaine, 7 heroin/cocaine and 7 control) or predominant heroin (29 heroin and 15 control) population of subjects. Results The amygdala of drug abusers was characterized by a striking positive correlation (r > 0.8) between AMPA GluA1 and post-synaptic protein-95 (PSD-95) mRNA levels, which was not evident in controls. Structural equation multi-group analysis of protein correlations also identified the relationship between GluA1 and PSD-95 protein levels as the distinguishing feature of abusers. In line with the GluA1—PSD-95 implications of enhanced synaptic plasticity, Homer 1b/c protein expression was significantly increased in both heroin and cocaine users as was its binding partner dynamin-3, localized to the endocytic zone. Furthermore, there was a positive relationship between Homer 1b/c and dynamin-3 in drug abusers that reflected an increase in the direct physical coupling between the proteins. A noted age-related decline of Homer 1b/c—dynamin-3 interactions, as well as GluA1 levels, was blunted in abusers. Conclusions Impairment of key components of the amygdala PSD and coupling to the endocytic zone, critical for the regulation of glutamate receptor cycling, may underlie heightened synaptic plasticity in human drug abusers. PMID:21126734

  16. Glutamate Metabolism in Major Depressive Disorder

    PubMed Central

    Abdallah, Chadi G.; Jiang, Lihong; De Feyter, Henk M.; Fasula, Madonna; Krystal, John H.; Rothman, Douglas L.; Mason, Graeme F.; Sanacora, Gerard

    2015-01-01

    Objective Emerging evidence suggests abnormalities in amino acid neurotransmitter function and impaired energy metabolism contribute to the underlying pathophysiology of Major Depressive Disorder (MDD). To test whether impairments in energetics and glutamate neurotransmitter cycling are present in MDD we used in vivo 13C magnetic resonance spectroscopy (13C MRS) to measure these fluxes in individuals diagnosed with MDD relative to non-depressed subjects. Method 1H MRS and 13C MRS data were collected on 23 medication-free MDD and 17 healthy subjects. 1H MRS provided total glutamate and GABA concentrations, and 13C MRS, coupled with intravenous infusion of [1-13C]-glucose, provided measures of the neuronal tricarboxylic acid cycle (VTCAN) for mitochondrial energy production, GABA synthesis, and glutamate/glutamine cycling, from voxels placed in the occipital cortex. Results Our main finding was that mitochondrial energy production of glutamatergic neurons was reduced by 26% in MDD subjects (t = 2.57, p = 0.01). Paradoxically we found no difference in the rate of glutamate/glutamine cycle (Vcycle). We also found a significant correlation between glutamate concentrations and Vcycle considering the total sample. Conclusions We interpret the reduction in mitochondrial energy production as being due to either mitochondrial dysfunction or a reduction in proper neuronal input or synaptic strength. Future MRS studies could help distinguish these possibilities. PMID:25073688

  17. BMP signaling and microtubule organization regulate synaptic strength

    PubMed Central

    Ball, Robin W.; Peled, Einat; Guerrero, Giovanna; Isacoff, Ehud Y.

    2015-01-01

    The strength of synaptic transmission between a neuron and multiple postsynaptic partners can vary considerably. We have studied synaptic heterogeneity using the glutamatergic Drosophila neuromuscular junction (NMJ), which contains multiple synaptic connections of varying strength between a motor axon and muscle fiber. In larval NMJs, there is a gradient of synaptic transmission from weak proximal to strong distal boutons. We imaged synaptic transmission with the postsynaptically targeted fluorescent calcium sensor SynapCam, to investigate the molecular pathways that determine synaptic strength and set up this gradient. We discovered that mutations in the Bone Morphogenetic Protein (BMP) signaling pathway disrupt production of strong distal boutons. We find that strong connections contain unbundled microtubules in the boutons, suggesting a role for microtubule organization in transmission strength. The spastin mutation, which disorganizes microtubules, disrupted the transmission gradient, supporting this interpretation. We propose that the BMP pathway, shown previously to function in the homeostatic regulation of synaptic growth, also boosts synaptic transmission in a spatially selective manner that depends on the microtubule system. PMID:25681521

  18. Activity-dependent synaptic GRIP1 accumulation drives synaptic scaling up in response to action potential blockade

    PubMed Central

    Gainey, Melanie A.; Tatavarty, Vedakumar; Nahmani, Marc; Lin, Heather; Turrigiano, Gina G.

    2015-01-01

    Synaptic scaling is a form of homeostatic plasticity that stabilizes neuronal firing in response to changes in synapse number and strength. Scaling up in response to action-potential blockade is accomplished through increased synaptic accumulation of GluA2-containing AMPA receptors (AMPAR), but the receptor trafficking steps that drive this process remain largely obscure. Here, we show that the AMPAR-binding protein glutamate receptor-interacting protein-1 (GRIP1) is essential for regulated synaptic AMPAR accumulation during scaling up. Synaptic abundance of GRIP1 was enhanced by activity deprivation, directly increasing synaptic GRIP1 abundance through overexpression increased the amplitude of AMPA miniature excitatory postsynaptic currents (mEPSCs), and shRNA-mediated GRIP1 knockdown prevented scaling up of AMPA mEPSCs. Furthermore, knockdown and replace experiments targeting either GRIP1 or GluA2 revealed that scaling up requires the interaction between GRIP1 and GluA2. Finally, GRIP1 synaptic accumulation during scaling up did not require GluA2 binding. Taken together, our data support a model in which activity-dependent trafficking of GRIP1 to synaptic sites drives the forward trafficking and enhanced synaptic accumulation of GluA2-containing AMPAR during synaptic scaling up. PMID:26109571

  19. Ethanol directly depresses AMPA and NMDA glutamate currents in spinal cord motor neurons independent of actions on GABAA or glycine receptors.

    PubMed

    Wang, M Y; Rampil, I J; Kendig, J J

    1999-07-01

    Ethanol is a general anesthetic agent as defined by abolition of movement in response to noxious stimulation. This anesthetic endpoint is due to spinal anesthetic actions. This study was designed to test the hypothesis that ethanol acts directly on motor neurons to inhibit excitatory synaptic transmission at glutamate receptors. Whole cell recordings were made in visually identified motor neurons in spinal cord slices from 14- to 23-day-old rats. Currents were evoked by stimulating a dorsal root fragment or by brief pulses of glutamate. Ethanol at general anesthetic concentrations (50-200 mM) depressed both responses. Ethanol also depressed glutamate-evoked responses in the presence of tetrodotoxin (300 nM), showing that its actions are postsynaptic. Block of inhibitory gamma-aminobutyric acidA and glycine receptors by bicuculline (50 microM) and strychnine (5 microM), respectively, did not significantly reduce the effects of ethanol on glutamate currents. Ethanol also depressed glutamate-evoked currents when the inhibitory receptors were blocked and either D, L-2-amino-5-phosphonopentanoic acid (40 microM) or 6-cyano-7-nitroquinoxaline-2,3-dione disodium (10 microM) were applied to block N-methyl-D-aspartate or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate receptors, respectively. The results show that ethanol exerts direct depressant effects on both alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid and N-methyl-D-aspartate glutamate currents in motor neurons. Enhancement of gamma-aminobutyric acidA and glycine inhibition is not required for this effect. Direct depression of glutamatergic excitatory transmission by a postsynaptic action on motor neurons thus may contribute to general anesthesia as defined by immobility in response to a noxious stimulus. PMID:10381800

  20. Synaptic dysfunction in Parkinson's disease.

    PubMed

    Picconi, Barbara; Piccoli, Giovanni; Calabresi, Paolo

    2012-01-01

    Activity-dependent modifications in synaptic efficacy, such as long-term depression (LTD) and long-term potentiation (LTP), represent key cellular substrates for adaptive motor control and procedural memory. The impairment of these two forms of synaptic plasticity in the nucleus striatum could account for the onset and the progression of motor and cognitive symptoms of Parkinson's disease (PD), characterized by the massive degeneration of dopaminergic neurons. In fact, both LTD and LTP are peculiarly controlled and modulated by dopaminergic transmission coming from nigrostriatal terminals. Changes in corticostriatal and nigrostriatal neuronal excitability may influence profoundly the threshold for the induction of synaptic plasticity, and changes in striatal synaptic transmission efficacy are supposed to play a role in the occurrence of PD symptoms. Understanding of these maladaptive forms of synaptic plasticity has mostly come from the analysis of experimental animal models of PD. A series of cellular and synaptic alterations occur in the striatum of experimental parkinsonism in response to the massive dopaminergic loss. In particular, dysfunctions in trafficking and subunit composition of glutamatergic NMDA receptors on striatal efferent neurons contribute to the clinical features of the experimental parkinsonism. Interestingly, it has become increasingly evident that in striatal spiny neurons, the correct assembly of NMDA receptor complex at the postsynaptic site is a major player in early phases of PD, and it is sensitive to distinct degrees of DA denervation. The molecular defects at the basis of PD progression may be not confined just at the postsynaptic neuron: accumulating evidences have recently shown that the genes linked to PD play a critical role at the presynaptic site. DA release into the synaptic cleft relies on a proper presynaptic vesicular transport; impairment of SV trafficking, modification of DA flow, and altered presynaptic plasticity have

  1. Nuclear respiratory factor 1 co-regulates AMPA glutamate receptor subunit 2 and cytochrome c oxidase : Tight coupling of glutamatergic transmission and energy metabolism in neurons

    PubMed Central

    Dhar, Shilpa S.; Liang, Huan Ling; Wong-Riley, Margaret T. T.

    2013-01-01

    Neuronal activity, especially of the excitatory glutamatergic type, is highly dependent on energy from the oxidative pathway. We hypothesized that the coupling existed at the transcriptional level by having the same transcription factor to regulate a marker of energy metabolism, cytochrome c oxidase (COX) and an important subunit of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) glutamate receptors, GluR2 (Gria2). Nuclear respiratory factor 1 (NRF-1) was a viable candidate because it regulates all COX subunits and potentially activates Gria2. By means of in silico analysis, electrophoretic mobility shift and supershift, chromatin immunoprecipitation, and promoter mutational assays, we found that NRF-1 functionally bound to Gria2 promoter. Silencing of NRF-1 with small interference RNA prevented the depolarization-stimulated up-regulation of Gria2 and COX, and over-expression of NRF-1 rescued neurons from TTX-induced down-regulation of Gria2 and COX transcripts. Thus, neuronal activity and energy metabolism are tightly coupled at the molecular level, and NRF-1 is a critical agent in this process. PMID:19166514

  2. Early developmental bisphenol-A exposure sex-independently impairs spatial memory by remodeling hippocampal dendritic architecture and synaptic transmission in rats.

    PubMed

    Liu, Zhi-Hua; Ding, Jin-Jun; Yang, Qian-Qian; Song, Hua-Zeng; Chen, Xiang-Tao; Xu, Yi; Xiao, Gui-Ran; Wang, Hui-Li

    2016-01-01

    Bisphenol-A (BPA, 4, 4'-isopropylidene-2-diphenol), a synthetic xenoestrogen that widely used in the production of polycarbonate plastics, has been reported to impair hippocampal development and function. Our previous study has shown that BPA exposure impairs Sprague-Dawley (SD) male hippocampal dendritic spine outgrowth. In this study, the sex-effect of chronic BPA exposure on spatial memory in SD male and female rats and the related synaptic mechanism were further investigated. We found that chronic BPA exposure impaired spatial memory in both SD male and female rats, suggesting a dysfunction of hippocampus without gender-specific effect. Further investigation indicated that BPA exposure causes significant impairment of dendrite and spine structure, manifested as decreased dendritic complexity, dendritic spine density and percentage of mushroom shaped spines in hippocampal CA1 and dentate gyrus (DG) neurons. Furthermore, a significant reduction in Arc expression was detected upon BPA exposure. Strikingly, BPA exposure significantly increased the mIPSC amplitude without altering the mEPSC amplitude or frequency, accompanied by increased GABAARβ2/3 on postsynaptic membrane in cultured CA1 neurons. In summary, our study indicated that Arc, together with the increased surface GABAARβ2/3, contributed to BPA induced spatial memory deficits, providing a novel molecular basis for BPA achieved brain impairment. PMID:27578147

  3. Early developmental bisphenol-A exposure sex-independently impairs spatial memory by remodeling hippocampal dendritic architecture and synaptic transmission in rats

    PubMed Central

    Liu, Zhi-Hua; Ding, Jin-Jun; Yang, Qian-Qian; Song, Hua-Zeng; Chen, Xiang-Tao; Xu, Yi; Xiao, Gui-Ran; Wang, Hui-Li

    2016-01-01

    Bisphenol-A (BPA, 4, 4′-isopropylidene-2-diphenol), a synthetic xenoestrogen that widely used in the production of polycarbonate plastics, has been reported to impair hippocampal development and function. Our previous study has shown that BPA exposure impairs Sprague-Dawley (SD) male hippocampal dendritic spine outgrowth. In this study, the sex-effect of chronic BPA exposure on spatial memory in SD male and female rats and the related synaptic mechanism were further investigated. We found that chronic BPA exposure impaired spatial memory in both SD male and female rats, suggesting a dysfunction of hippocampus without gender-specific effect. Further investigation indicated that BPA exposure causes significant impairment of dendrite and spine structure, manifested as decreased dendritic complexity, dendritic spine density and percentage of mushroom shaped spines in hippocampal CA1 and dentate gyrus (DG) neurons. Furthermore, a significant reduction in Arc expression was detected upon BPA exposure. Strikingly, BPA exposure significantly increased the mIPSC amplitude without altering the mEPSC amplitude or frequency, accompanied by increased GABAARβ2/3 on postsynaptic membrane in cultured CA1 neurons. In summary, our study indicated that Arc, together with the increased surface GABAARβ2/3, contributed to BPA induced spatial memory deficits, providing a novel molecular basis for BPA achieved brain impairment. PMID:27578147

  4. Astroglial glutamate transporters coordinate excitatory signaling and brain energetics.

    PubMed

    Robinson, Michael B; Jackson, Joshua G

    2016-09-01

    In the mammalian brain, a family of sodium-dependent transporters maintains low extracellular glutamate and shapes excitatory signaling. The bulk of this activity is mediated by the astroglial glutamate transporters GLT-1 and GLAST (also called EAAT2 and EAAT1). In this review, we will discuss evidence that these transporters co-localize with, form physical (co-immunoprecipitable) interactions with, and functionally couple to various 'energy-generating' systems, including the Na(+)/K(+)-ATPase, the Na(+)/Ca(2+) exchanger, glycogen metabolizing enzymes, glycolytic enzymes, and mitochondria/mitochondrial proteins. This functional coupling is bi-directional with many of these systems both being regulated by glutamate transport and providing the 'fuel' to support glutamate uptake. Given the importance of glutamate uptake to maintaining synaptic signaling and preventing excitotoxicity, it should not be surprising that some of these systems appear to 'redundantly' support the energetic costs of glutamate uptake. Although the glutamate-glutamine cycle contributes to recycling of neurotransmitter pools of glutamate, this is an over-simplification. The ramifications of co-compartmentalization of glutamate transporters with mitochondria for glutamate metabolism are discussed. Energy consumption in the brain accounts for ∼20% of the basal metabolic rate and relies almost exclusively on glucose for the production of ATP. However, the brain does not possess substantial reserves of glucose or other fuels. To ensure adequate energetic supply, increases in neuronal activity are matched by increases in cerebral blood flow via a process known as 'neurovascular coupling'. While the mechanisms for this coupling are not completely resolved, it is generally agreed that astrocytes, with processes that extend to synapses and endfeet that surround blood vessels, mediate at least some of the signal that causes vasodilation. Several studies have shown that either genetic deletion or

  5. Post-Translational Modification Biology of Glutamate Receptors and Drug Addiction

    PubMed Central

    Mao, Li-Min; Guo, Ming-Lei; Jin, Dao-Zhong; Fibuch, Eugene E.; Choe, Eun Sang; Wang, John Q.

    2011-01-01

    Post-translational covalent modifications of glutamate receptors remain a hot topic. Early studies have established that this family of receptors, including almost all ionotropic and metabotropic glutamate receptor subtypes, undergoes active phosphorylation at serine, threonine, or tyrosine residues in their intracellular domains. Recent evidence identifies several glutamate receptor subtypes to be direct substrates for palmitoylation at cysteine residues. Other modifications such as ubiquitination and sumoylation at lysine residues also occur to certain glutamate receptors. These modifications are dynamic and reversible in nature and are regulatable by changing synaptic inputs. The regulated modifications significantly impact the receptor in many ways, including interrelated changes in biochemistry (synthesis, subunit assembling, and protein–protein interactions), subcellular redistribution (trafficking, endocytosis, synaptic delivery, and clustering), and physiology, usually associated with changes in synaptic plasticity. Glutamate receptors are enriched in the striatum and cooperate closely with dopamine to regulate striatal signaling. Emerging evidence shows that modification processes of striatal glutamate receptors are sensitive to addictive drugs, such as psychostimulants (cocaine and amphetamine). Altered modifications are believed to be directly linked to enduring receptor/synaptic plasticity and drug-seeking. This review summarizes several major types of modifications of glutamate receptors and analyzes the role of these modifications in striatal signaling and in the pathogenesis of psychostimulant addiction. PMID:21441996

  6. Synaptic dynamics: linear model and adaptation algorithm.

    PubMed

    Yousefi, Ali; Dibazar, Alireza A; Berger, Theodore W

    2014-08-01

    In this research, temporal processing in brain neural circuitries is addressed by a dynamic model of synaptic connections in which the synapse model accounts for both pre- and post-synaptic processes determining its temporal dynamics and strength. Neurons, which are excited by the post-synaptic potentials of hundred of the synapses, build the computational engine capable of processing dynamic neural stimuli. Temporal dynamics in neural models with dynamic synapses will be analyzed, and learning algorithms for synaptic adaptation of neural networks with hundreds of synaptic connections are proposed. The paper starts by introducing a linear approximate model for the temporal dynamics of synaptic transmission. The proposed linear model substantially simplifies the analysis and training of spiking neural networks. Furthermore, it is capable of replicating the synaptic response of the non-linear facilitation-depression model with an accuracy better than 92.5%. In the second part of the paper, a supervised spike-in-spike-out learning rule for synaptic adaptation in dynamic synapse neural networks (DSNN) is proposed. The proposed learning rule is a biologically plausible process, and it is capable of simultaneously adjusting both pre- and post-synaptic components of individual synapses. The last section of the paper starts with presenting the rigorous analysis of the learning algorithm in a system identification task with hundreds of synaptic connections which confirms the learning algorithm's accuracy, repeatability and scalability. The DSNN is utilized to predict the spiking activity of cortical neurons and pattern recognition tasks. The DSNN model is demonstrated to be a generative model capable of producing different cortical neuron spiking patterns and CA1 Pyramidal neurons recordings. A single-layer DSNN classifier on a benchmark pattern recognition task outperforms a 2-Layer Neural Network and GMM classifiers while having fewer numbers of free parameters and

  7. Frequency-dependent facilitation of synaptic throughput via postsynaptic NMDA receptors in the nucleus of the solitary tract.

    PubMed

    Zhao, Huan; Peters, James H; Zhu, Mingyan; Page, Stephen J; Ritter, Robert C; Appleyard, Suzanne M

    2015-01-01

    Hindbrain NMDA receptors play important roles in reflexive and behavioural responses to vagal activation. NMDA receptors have also been shown to contribute to the synaptic responses of neurons in the nucleus of the solitary tract (NTS), but their exact role remains unclear. In this study we used whole cell patch-clamping techniques in rat horizontal brain slice to investigate the role of NMDA receptors in the fidelity of transmission across solitary tract afferent-NTS neuron synapses. Results show that NMDA receptors contribute up to 70% of the charge transferred across the synapse at high (>5 Hz) firing rates, but have little contribution at lower firing frequencies. Results also show that NMDA receptors critically contribute to the fidelity of transmission across these synapses during high frequency (>5 Hz) afferent discharge rates. This novel role of NMDA receptors may explain in part how primary visceral afferents, including vagal afferents, can maintain fidelity of transmission across a broad range of firing frequencies. Neurons within the nucleus of the solitary tract (NTS) receive vagal afferent innervations that initiate gastrointestinal and cardiovascular reflexes. Glutamate is the fast excitatory neurotransmitter released in the NTS by vagal afferents, which arrive there via the solitary tract (ST). ST stimulation elicits excitatory postsynaptic currents (EPSCs) in NTS neurons mediated by both AMPA- and NMDA-type glutamate receptors (-Rs). Vagal afferents exhibit a high probability of vesicle release and exhibit robust frequency-dependent depression due to presynaptic vesicle depletion. Nonetheless, synaptic throughput is maintained even at high frequencies of afferent activation. Here we test the hypothesis that postsynaptic NMDA-Rs are essential in maintaining throughput across ST-NTS synapses. Using patch clamp electrophysiology in horizontal brainstem slices, we found that NMDA-Rs, including NR2B subtypes, carry up to 70% of the charge transferred

  8. Therapeutic Potential of Metabotropic Glutamate Receptor Modulators

    PubMed Central

    Hovelsø, N; Sotty, F; Montezinho, L.P; Pinheiro, P.S; Herrik, K.F; Mørk, A

    2012-01-01

    Glutamate is the main excitatory neurotransmitter in the central nervous system (CNS) and is a major player in complex brain functions. Glutamatergic transmission is primarily mediated by ionotropic glutamate receptors, which include NMDA, AMPA and kainate receptors. However, glutamate exerts modulatory actions through a family of metabotropic G-protein-coupled glutamate receptors (mGluRs). Dysfunctions of glutamatergic neurotransmission have been implicated in the etiology of several diseases. Therefore, pharmacological modulation of ionotropic glutamate receptors has been widely investigated as a potential therapeutic strategy for the treatment of several disorders associated with glutamatergic dysfunction. However, blockade of ionotropic glutamate receptors might be accompanied by severe side effects due to their vital role in many important physiological functions. A different strategy aimed at pharmacologically interfering with mGluR function has recently gained interest. Many subtype selective agonists and antagonists have been identified and widely used in preclinical studies as an attempt to elucidate the role of specific mGluRs subtypes in glutamatergic transmission. These studies have allowed linkage between specific subtypes and various physiological functions and more importantly to pathological states. This article reviews the currently available knowledge regarding the therapeutic potential of targeting mGluRs in the treatment of several CNS disorders, including schizophrenia, addiction, major depressive disorder and anxiety, Fragile X Syndrome, Parkinson’s disease, Alzheimer’s disease and pain. PMID:22942876

  9. Phosphorylation of delta2 glutamate receptors at serine 945 is not required for cerebellar long-term depression.

    PubMed

    Nakagami, Ryoichi; Kohda, Kazuhisa; Kakegawa, Wataru; Kondo, Tetsuro; Kato, Nobumasa; Yuzaki, Michisuke

    2008-06-01

    Long-term depression (LTD) of synaptic transmission at parallel fiber (PF)-Purkinje cell synapses is thought to regulate motor learning and memory formation in the cerebellum. Neuronal activity-evoked protein kinase C (PKC) activation is required for the induction of LTD. In addition, the delta2 glutamate receptor (GluRdelta2), which is predominantly expressed at PF-Purkinje cell synapses, is indispensable for the induction of LTD; however, the mechanisms by which GluRdelta2 regulates LTD and its relationship with PKC activation remain elusive. Interestingly, GluRdelta2 is phosphorylated by PKC on serine 945 (Ser945) near its C-terminus and a postsynaptic protein S-SCAM, which could potentially regulate glutamate receptor trafficking and synaptic plasticity, binds to the extreme C-terminus of GluRdelta2 in a phosphorylation-dependent manner on Ser945. Here, using a Sindbis-based virus expression approach, we show that a mutant GluRdelta2, in which alanine replaced Ser945 and did not undergo PKC phosphorylation, was normally localized at the postsynaptic sites of PF-Purkinje cell synapses. In addition, like wild-type GluRdelta2, the phosphorylation-disrupted GluRdelta2 successfully rescued abrogated LTD in GluRdelta2-null Purkinje cells. These results indicate that Ser945, a major PKC phosphorylation site of of GluRdelta2, may not play a crucial role in induction of LTD in the cerebellum. PMID:18677091

  10. Calcineurin mediates homeostatic synaptic plasticity by regulating retinoic acid synthesis

    PubMed Central

    Arendt, Kristin L.; Zhang, Zhenjie; Ganesan, Subhashree; Hintze, Maik; Shin, Maggie M.; Tang, Yitai; Cho, Ahryon; Graef, Isabella A.; Chen, Lu

    2015-01-01

    Homeostatic synaptic plasticity is a form of non-Hebbian plasticity that maintains stability of the network and fidelity for information processing in response to prolonged perturbation of network and synaptic activity. Prolonged blockade of synaptic activity decreases resting Ca2+ levels in neurons, thereby inducing retinoic acid (RA) synthesis and RA-dependent homeostatic synaptic plasticity; however, the signal transduction pathway that links reduced Ca2+-levels to RA synthesis remains unknown. Here we identify the Ca2+-dependent protein phosphatase calcineurin (CaN) as a key regulator for RA synthesis and homeostatic synaptic plasticity. Prolonged inhibition of CaN activity promotes RA synthesis in neurons, and leads to increased excitatory and decreased inhibitory synaptic transmission. These effects of CaN inhibitors on synaptic transmission are blocked by pharmacological inhibitors of RA synthesis or acute genetic deletion of the RA receptor RARα. Thus, CaN, acting upstream of RA, plays a critical role in gating RA signaling pathway in response to synaptic activity. Moreover, activity blockade-induced homeostatic synaptic plasticity is absent in CaN knockout neurons, demonstrating the essential role of CaN in RA-dependent homeostatic synaptic plasticity. Interestingly, in GluA1 S831A and S845A knockin mice, CaN inhibitor- and RA-induced regulation of synaptic transmission is intact, suggesting that phosphorylation of GluA1 C-terminal serine residues S831 and S845 is not required for CaN inhibitor- or RA-induced homeostatic synaptic plasticity. Thus, our study uncovers an unforeseen role of CaN in postsynaptic signaling, and defines CaN as the Ca2+-sensing signaling molecule that mediates RA-dependent homeostatic synaptic plasticity. PMID:26443861

  11. Calcineurin mediates homeostatic synaptic plasticity by regulating retinoic acid synthesis.

    PubMed

    Arendt, Kristin L; Zhang, Zhenjie; Ganesan, Subhashree; Hintze, Maik; Shin, Maggie M; Tang, Yitai; Cho, Ahryon; Graef, Isabella A; Chen, Lu

    2015-10-20

    Homeostatic synaptic plasticity is a form of non-Hebbian plasticity that maintains stability of the network and fidelity for information processing in response to prolonged perturbation of network and synaptic activity. Prolonged blockade of synaptic activity decreases resting Ca(2+) levels in neurons, thereby inducing retinoic acid (RA) synthesis and RA-dependent homeostatic synaptic plasticity; however, the signal transduction pathway that links reduced Ca(2+)-levels to RA synthesis remains unknown. Here we identify the Ca(2+)-dependent protein phosphatase calcineurin (CaN) as a key regulator for RA synthesis and homeostatic synaptic plasticity. Prolonged inhibition of CaN activity promotes RA synthesis in neurons, and leads to increased excitatory and decreased inhibitory synaptic transmission. These effects of CaN inhibitors on synaptic transmission are blocked by pharmacological inhibitors of RA synthesis or acute genetic deletion of the RA receptor RARα. Thus, CaN, acting upstream of RA, plays a critical role in gating RA signaling pathway in response to synaptic activity. Moreover, activity blockade-induced homeostatic synaptic plasticity is absent in CaN knockout neurons, demonstrating the essential role of CaN in RA-dependent homeostatic synaptic plasticity. Interestingly, in GluA1 S831A and S845A kn