Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “synaptic plasticity”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources
PubMed2006

A role for the protein phosphatase 2B in altered hippocampal synaptic plasticity in the aged rat.

Synaptic plasticity following NMDA application on hippocampal slices from young (3-5 months) and aged (24-27 months) rats was compared. In young rats, NMDA (20 microM) induced opposite effects depending on the duration of the application. A short (1 min) or long (5 min) application induced a long-term depression of synaptic activity while a 3 min application induced a potentiation. In aged rats, however, NMDA application always induced depression, regardless of the duration. To identify mechanisms which could explain the difference observed between young and aged rats, we explored changes in NMDA receptor activation and changes in kinase/phosphatase balance. We first demonstrate that the potentiation present in slices from young rats was not restored in aged rats by exogenous application of the co-agonist of NMDA receptor d-serine (which compensates for the changes in NMDAR activation seen in aged rats). This suggested that alterations in synaptic plasticity activation mainly involve intracellular mechanisms. We next showed that the participation of the kinases PKA and CaMKII in the NMDA-induced potentiation in young rats is negligible. Finally, we determined the consequences of phosphatase inhibition in aged rats. Incubation of slices in okadaic acid (a PP1/PP2B antagonist) did not affect the depression induced by a 3min NMDA application in aged rats. The PP2B antagonist FK506 restored potentiation in aged rats (3 min NMDA application). In hippocampal neurons from aged rats, a depression is always observed, suggesting a preferential activation of PP2B by NMDA in these neurons.

2-Amino-5-phosphonovalerate↗
PubMed2006

Synaptic plasticity and phosphorylation.

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.

Animals↗
PubMedDate not supplied

[The mechanisms of synaptic plasticity: the role of synaptic protein phosphorylation and gene expression].

Results of investigations of protein phosphorylation and gene expression in the mechanisms of long-term potentiation and kindling was analyzed. It was discussed the participation of N-methyl-D-aspartate receptors, intracellular Ca2+, different protein kinases and immediate-early genes in the induction and maintenance of long-term changes of glutamatergic synaptic efficiency in hippocampus. It was suggested the essential role of the level of intracellular Ca2+ in the induction of the cell program leaded to the trace processes during electrical stimulation of the same hippocampal area.

Animals↗
PubMed2006

Hippocampal CA1 synaptic plasticity as a gamma transfer function.

The capacity of activity-dependent synaptic modification is essential in processing and storing information, yet little is known about how synaptic plasticity alters the input-output conversion efficiency at the synapses. In the adult mouse hippocampus in vivo, we carefully compared the input-output relationship, in terms of presynaptic activity levels versus postsynaptic potentials, before and after the induction of synaptic plasticity and found that synaptic plasticity led synapses to respond more robustly to inputs, that is, synaptic gain was increased as a function of synaptic activity with an expansive, power-law nonlinearity, i.e. conforming to the so-called gamma curve. In extreme cases, long-term potentiation and depression coexist in the same synaptic pathway with long-term potentiation dominating over long-term depression at higher levels of presynaptic activity. These findings predict a novel function of synaptic plasticity, i.e. a contrast-enhancing filtering of neural information through a gamma correction-like process.

Animals↗
PubMed2006

Effect of stochastic synaptic and dendritic dynamics on synaptic plasticity in visual cortex and hippocampus.

Various forms of synaptic plasticity, including spike timing-dependent plasticity, can be accounted for by calcium-dependent models of synaptic plasticity. However, recent results in which synaptic plasticity is induced by multi-spike protocols cannot simply be accounted for by linear superposition of plasticity due to spike pairs or by existing calcium-dependent models. In this paper, we show that multi-spike protocols can be accounted for if, in addition to the dynamics of back-propagating action potentials, stochastic synaptic dynamics are taken into account. We show that a stochastic implementation can account for the data better than a deterministic implementation and is also more robust. Our results demonstrate that differences between experimental results obtained in hippocampus and visual cortex can be accounted for by the different synaptic and dendritic dynamics in these two systems.

Action Potentials↗
PubMed2005

Early presynaptic and late postsynaptic components contribute independently to brain-derived neurotrophic factor-induced synaptic plasticity.

Trophin-induced synaptic plasticity consists of both presynaptic and postsynaptic processes. The potential interdependence of these mechanisms and their temporal relationships are undefined. The synaptic vesicle protein Rab3A is required for the early, initial 10 min phase but not for the later phase of BDNF-enhanced transmission. We now examine the temporal distinction and mechanistic relationships between these phases of BDNF action. Rab3A mutant cells did not exhibit increased miniature EPSC frequency in response to BDNF in cell culture, indicating an absence of the presynaptic component. In contrast, BDNF enhanced postsynaptic glutamate-induced current in the mutant neurons as in the wild type, indicating that the postsynaptic component of the response was intact. Finally, the postsynaptic NMDA receptor subunit NR2B was phosphorylated at Tyr1472 by BDNF in Rab3A knock-outs, as shown previously in wild type. Our results are the first to demonstrate that presynaptic and postsynaptic components of BDNF-enhanced synaptic activity are independent and temporally distinct.

Animals↗
PubMed2002

Regulation of AMPA receptors during synaptic plasticity.

Ionotropic neurotransmitter receptors mediate rapid synaptic transmission in the CNS and PNS. Owing to this central role in trans-synaptic signal transduction, modulation of these receptors could play a crucial role in the expression of synaptic plasticity in the brain. AMPA receptors mediate the majority of rapid excitatory synaptic transmission in the CNS. Recent studies have indicated that the activity and synaptic distribution of these receptors is dynamically regulated and could be crucial for the short- and long-term modification of synaptic efficacy. Here we review recent data on the molecular mechanisms that underlie the modulation of AMPA receptors and the role of AMPA-receptor regulation in mediating synaptic plasticity.

Animals↗
PubMed1999

Priming-induced shift in synaptic plasticity in the rat hippocampus.

The activity history of a given neuron has been suggested to influence its future responses to synaptic input in one prominent model of experience-dependent synaptic plasticity proposed by Bienenstock, Cooper, and Munro (BCM theory). Because plasticity of synaptic plasticity (i.e., metaplasticity) is similar in concept to aspects of the BCM proposal, we have tested the possibility that a form of metaplasticity induced by a priming stimulation protocol might exhibit BCM-like characteristics. CA1 field excitatory postsynaptic potentials (EPSPs) obtained from rat hippocampal slices were used to monitor synaptic responses before and after conditioning stimuli (3-100 Hz) of the Schaffer collateral inputs. A substantial rightward shift (>5-fold) in the frequency threshold between long-term depression (LTD) and long-term potentiation (LTP) was observed <1 h after priming. This change in the LTD/P crossover point occurred at both primed and unprimed synaptic pathways. These results provide new support for the existence of a rapid, heterosynaptic, experience-dependent mechanism that is capable of modifying the synaptic plasticity phenomena that are commonly proposed to be important for developmental and learning/memory processes in the brain.

2-Amino-5-phosphonovalerate↗
PubMed1996

Neural cell adhesion molecules in activity-dependent development and synaptic plasticity.

Cell adhesion molecules (CAMs) have a vital role in forming connections between neurons during embryonic development. Increasing evidence suggests that CAMs also participate in activity-dependent plasticity during development and synaptic plasticity in adults. Neural impulses of appropriate patterns can regulate expression of specific CAMs in mouse neurons from dorsal-root ganglia, alter cell-cell adhesion and produce structural reorganization of axon terminals in culture. Synaptic plasticity in Aplysia, learning in chick and long-term potentiation in rat hippocampus are accompanied by changes in CAM expression. Long-term potentiation can be blocked by disrupting CAM function in rat hippocampus, and learning deficits result from antibody blockade of CAMs in chicks and in transgenic mice lacking specific CAMs. Cell adhesion molecules might produce these effects by controlling several cellular processes, including cell adhesion, cytoskeletal structure and intracellular signaling.

Animals↗
PubMed2003

Dopamine: a potential substrate for synaptic plasticity and memory mechanisms.

It is only recently that a number of studies on synaptic plasticity in the hippocampus and other brain areas have considered that a heterosynaptic modulatory input could be recruited as well as the coincident firing of pre- and post-synaptic neurons. So far, the strongest evidence for such a regulation has been attributed to dopaminergic (DA) systems but other modulatory pathways have also been considered to influence synaptic plasticity. This review will focus on dopamine contribution to synaptic plasticity in different brain areas (hippocampus, striatum and prefrontal cortex) with, for each region, a few lines on the distribution of DA projections and receptors. New insights into the possible mechanisms underlying these plastic changes will be considered. The contribution of various DA systems in certain forms of learning and memory will be reviewed with recent advances supporting the hypothesis of similar cellular mechanisms underlying DA regulation of synaptic plasticity and memory processes in which the cyclic adenosine monophosphate/protein kinase A (cAMP/PKA) pathway has a potential role. To summarize, endogenous DA, which depends on the activity patterns of DA midbrain neurons in freely moving animals, appears as a key regulator in specific synaptic changes observed at certain stages of learning and memory and of synaptic plasticity.

Animals↗
PubMed2003

Dopamine, acetylcholine and nitric oxide systems interact to induce corticostriatal synaptic plasticity.

Two distinct forms of synaptic plasticity have been described at corticostriatal synapses: long-term depression (LTD) and long-term potentiation (LTP). Both these enduring changes in the efficacy of excitatory neurotransmission in the striatum have a major impact on the physiological activity of the basal ganglia and are triggered by the stimulation of complex and independent cascades of intracellular second messenger systems. Along with the massive glutamatergic inputs originating from the cortex, striatal neurons receive a myriad of other synaptic contacts arising from different sources. In particular, while the nigrostriatal pathway provides this brain area with dopamine (DA), intrinsic circuits are the main source of acetylcholine (ACh) and nitric oxide (NO). The three neurotransmitter systems interact with each other to determine whether corticostriatal LTP or LTD is triggered in response to repetitive synaptic stimulation. Two distinct subtypes of striatal interneurons produce ACh and NO in the striatum. These interneurons are activated by the cortex during the induction phase of striatal plasticity, and stimulate, in turn, the intracellular changes in projection neurons required for LTD or LTP. Interneurons, therefore, exert a feedforward control of the excitability of striatal projection neurons by ensuring the coordinate expression of two alternative forms of synaptic plasticity at the same type of excitatory synapse. The integrative action exerted by striatal projection neurons on the converging information arising from the cortex, nigral DA neurons, and from ACh- and NO-producing interneurons dictates the final output of the striatum to the other structures of the basal ganglia.

Acetylcholine↗
PubMed2003

Regulation of hippocampal synaptic plasticity by cyclic AMP-dependent protein kinases.

Protein kinases critically regulate synaptic plasticity in the mammalian hippocampus. Cyclic-AMP dependent protein kinase (PKA) is a serine-threonine kinase that has been strongly implicated in the expression of specific forms of long-term potentiation (LTP), long-term depression (LTD), and hippocampal long-term memory. We review the roles of PKA in activity-dependent forms of hippocampal synaptic plasticity by highlighting particular themes that have emerged in ongoing research. These include the participation of distinct isoforms of PKA in specific types of synaptic plasticity, modification of the PKA-dependence of LTP by multiple factors such as distinct patterns of imposed activity, environmental enrichment, and genetic manipulation of signalling molecules, and presynaptic versus postsynaptic mechanisms for PKA-dependent LTP. We also discuss many of the substrates that have been implicated as targets for PKA's actions in hippocampal synaptic plasticity, including CREB, protein phosphatases, and glutamatergic receptors. Future prospects for shedding light on the roles of PKA are also described from the perspective of specific aspects of synaptic physiology and brain function that are ripe for investigation using incisive genetic, cell biological, and electrophysiological approaches.

Animals↗
PubMed2006

Pain-related synaptic plasticity in spinal dorsal horn neurons: role of CGRP.

BACKGROUND: The synaptic and cellular mechanisms of pain-related central sensitization in the spinal cord are not fully understood yet. Calcitonin gene-related peptide (CGRP) has been identified as an important molecule in spinal nociceptive processing and ensuing behavioral responses, but its contribution to synaptic plasticity, cellular mechanisms and site of action in the spinal cord remain to be determined. Here we address the role of CGRP in synaptic plasticity in the spinal dorsal horn in a model of arthritic pain. RESULTS: Whole-cell current- and voltage-clamp recordings were made from substantia gelatinosa (SG) neurons in spinal cord slices from control rats and arthritic rats (> 6 h postinjection of kaolin/carrageenan into the knee). Monosynaptic excitatory postsynaptic currents (EPSCs) were evoked by electrical stimulation of afferents in the dorsal root near the dorsal root entry zone. Neurons in slices from arthritic rats showed increased synaptic transmission and excitability compared to controls. A selective CGRP1 receptor antagonist (CGRP8-37) reversed synaptic plasticity in neurons from arthritic rats but had no significant effect on normal transmission. CGRP facilitated synaptic transmission in the arthritis pain model more strongly than under normal conditions where both facilitatory and inhibitory effects were observed. CGRP also increased neuronal excitability. Miniature EPSC analysis suggested a post- rather than pre-synaptic mechanism of CGRP action. CONCLUSION: This study is the first to show synaptic plasticity in the spinal dorsal horn in a model of arthritic pain that involves a postsynaptic action of CGRP on SG neurons.

Action Potentials↗
PubMed2001

A functional role for adenosine A3 receptors: modulation of synaptic plasticity in the rat hippocampus.

Adenosine modulates hippocampal synaptic plasticity, namely long-term potentiation (LTP) and long-term depression (LTD), through activation of A1 and A2A receptors. We now report a novel role for the recently described adenosine A3 receptor in the regulation of synaptic plasticity in the CA1 area of hippocampal slices. Activation of adenosine A3 receptors by (1-[2-chloro-6-[[(3-iodophenyl)methyl]amino]-9H-purin-p-yl]-1-deoxy-N-methyl-beta-D-ribofuranuronamide (Cl-IBMECA) (100 nM) increased the magnitude of theta-burst induced LTP (from 1.2+/-0.6% in the control solution to 25.5+/-0.8% in the presence of Cl-IBMECA) and attenuated LTD (from 30.0+/-5.5% decrease in the control solution to 13.6+/-6.6% decrease in the presence of Cl-IBMECA). The selective adenosine A3 receptor antagonist, MRS 1191 (5-10 microM), prevented the effects of Cl-IBMECA. These findings indicate a functional role for adenosine A3 receptors in the modulation of synaptic plasticity.

Adenosine↗
PubMed2004

Metabotropic glutamate receptors and striatal synaptic plasticity: implications for neurological diseases.

Long- and short-term changes in the efficacy of synaptic transmission are known as synaptic plasticity. Phenomena such as long-term depression (LTD) and long-term potentiation (LTP) are two classical forms of synaptic plasticity that are expressed in several brain areas, including the striatum. Bi-directional changes in corticostriatal synaptic transmission, i.e. LTD and LTP, have been proposed to represent the cellular mechanisms underlying the physiological processes of motor learning and behavior. In parallel, other forms of synaptic plasticity induced by different experimental pathological conditions have been described in the striatum; these changes are presumed to represent the cellular processes underlying several neurological disorders, including Parkinson's disease and Huntington's chorea. A considerable number of receptor and post-receptor systems participate in the mechanisms of synaptic plasticity in the striatum, where glutamate plays a primary role through its ionotropic and metabotropic receptors (mGluRs). These latter constitute a group of recently characterized molecules, which have been shown to modulate synaptic transmission by acting on cellular excitability, ionic conductances and neurotransmitter release. These receptors have also been involved in several neuronal pathophysiological processes. The role of mGluRs in synaptic transmission and synaptic plasticity has been recently deeply studied and characterized in the striatum, in both physiological and pathological conditions. These findings open new and interesting perspectives in the study of basal ganglia function, and introduce new possible pharmacological approaches for the treatment of neurological disorders in which mGluRs have been experimentally involved.

Acetylcholine↗
PubMed2006

Requirement of dendritic calcium spikes for induction of spike-timing-dependent synaptic plasticity.

Spike-timing-dependent synaptic plasticity (STDP) by definition requires the temporal association of pre- and postsynaptic action potentials (APs). Yet, in cortical pyramidal neurons pairing unitary EPSPs with single APs at low frequencies is ineffective at generating plasticity. Using recordings from synaptically coupled layer 5 pyramidal neurons, we show here that high-frequency (200 Hz) postsynaptic AP bursts, rather than single APs, are required for both long-term potentiation (LTP) induction and NMDA channel activation during EPSP-AP pairing at low frequencies. Furthermore, we find that AP bursts can lead to LTP induction and NMDA channel activation during EPSP-AP pairing at both positive and negative times. High-frequency AP bursts generated supralinear calcium signals in basal dendrites suggesting the generation of dendritic calcium spikes, as has been observed previously in apical dendrites during AP burst firing at frequencies greater than 100 Hz. Consistent with a role of these dendritic calcium spikes in LTP induction, pairing EPSPs with low frequency (50 Hz) AP bursts was ineffective in generating LTP. Furthermore, supralinear calcium signals in basal dendrites during AP bursts were blocked by low concentrations of the T- and R-type calcium channel antagonist nickel, which also blocked LTP and NMDA channel activation. These data suggest an important role of dendritic calcium spikes during AP bursts in determining both the efficacy and time window for STDP induction.

Action Potentials↗
PubMed2004

Translational control by MAPK signaling in long-term synaptic plasticity and memory.

Enduring forms of synaptic plasticity and memory require new protein synthesis, but little is known about the underlying regulatory mechanisms. Here, we investigate the role of MAPK signaling in these processes. Conditional expression of a dominant-negative form of MEK1 in the postnatal murine forebrain inhibited ERK activation and caused selective deficits in hippocampal memory retention and the translation-dependent, transcription-independent phase of hippocampal L-LTP. In hippocampal neurons, ERK inhibition blocked neuronal activity-induced translation as well as phosphorylation of the translation factors eIF4E, 4EBP1, and ribosomal protein S6. Correspondingly, protein synthesis and translation factor phosphorylation induced in control hippocampal slices by L-LTP-generating tetanization were significantly reduced in mutant slices. Translation factor phosphorylation induced in the control hippocampus by memory formation was similarly diminished in the mutant hippocampus. These results suggest a crucial role for translational control by MAPK signaling in long-lasting forms of synaptic plasticity and memory.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Diabetes mellitus preserves synaptic plasticity in hippocampal slices from middle-aged rats.

Synaptic plasticity is generally believed to provide a cellular mechanism for learning and memory. One manifestation of synaptic plasticity, long-term potentiation in the CA1 region, was compared in hippocampal slices from young and older rats, both control animals and streptozotocin-treated diabetics with moderate hyperglycemia ( approximately 15 mM). Long-term potentiation of excitatory synaptic potentials, elicited by tetanic stimulation or by 2-deoxy-D-glucose application, was readily obtained in slices from young (four-month-old) control and diabetic rats, but not in slices from middle-aged (12-month-old) control rats. Both forms of potentiation, however, could be elicited in slices from 12-month-old diabetics. The unexpected finding that long-term potentiation is restored in moderately hyperglycemic older rats suggests that the blood glucose level of older animals may be important for synaptic plasticity and perhaps for the ability to learn.

Aging↗