Transiently higher release probability during critical period at thalamocortical synapses in the mouse barrel cortex: relevance to differential short-term plasticity of AMPA and NMDA EPSCs and possible involvement of silent synapses

2004 ◽  
Vol 20 (11) ◽  
pp. 3006-3018 ◽  
Author(s):  
Takufumi Yanagisawa ◽  
Tadaharu Tsumoto ◽  
Fumitaka Kimura
Keyword(s):  
Critical Period ◽  
Barrel Cortex ◽  
Short Term ◽  
Short Term Plasticity ◽  
Release Probability ◽  
Silent Synapses

scholarly journals Presynaptic Endoplasmic Reticulum Contributes Crucially to Short-term Plasticity in Small Hippocampal Synapses

2018 ◽  
Author(s):  
Nishant Singh ◽  
Thomas Bartol ◽  
Herbert Levine ◽  
Terrence Sejnowski ◽  
Suhita Nadkarni
Keyword(s):  
Endoplasmic Reticulum ◽  
Calcium Influx ◽  
Critical Role ◽  
Presynaptic Terminal ◽  
Calcium Stores ◽  
Pathological State ◽  
Calcium Dynamics ◽  
Short Term ◽  
Short Term Plasticity ◽  
Release Probability

Short-term plasticity (STP) of the presynaptic terminal maintains a brief history of activity experienced by the synapse that may otherwise remain unseen by the postsynaptic neuron. These synaptic changes are primarily regulated by calcium dynamics in the presynaptic terminal. A rapid increase in intracellular calcium is initiated by the opening of voltage-dependent calcium channels in response to depolarization, the main source of calcium required for vesicle fusion. Separately, electron-microscopic studies of hippocampal CA3-CA1 synapses reveal the strong presence of endoplasmic reticulum (ER) in all presynaptic terminals. However, the precise role of the ER in modifying STP at the presynaptic terminal remains unexplored. To investigate the contribution of ER in modulating calcium dynamics in small hippocampal boutons, we performed in silico experiments in a physiologically-realistic canonical synaptic geometry based on reconstructions of CA3-CA1 Schaffer collaterals in the rat hippocampus. The model predicts that presynaptic calcium stores are critical in generating the observed paired-pulse ratio (PPR) of normal CA3-CA1 synapses. In control synapses with intact ER, SERCA pumps act as additional calcium buffers, lowering the intrinsic release probability of vesicle release and increasing PPR. In addition, the presence of ER allows ongoing activity to trigger calcium influx from the presynaptic ER via ryanodine receptors (RyRs) and inositol trisphosphate receptors (IP3Rs). Intracellular stores and their associated machinery also allows a synapse with a low release probability to operate more reliably due to attenuation of calcium fluctuations. Finally, blocking ER activity in the presynaptic terminal mimics the pathological state of a low facilitating synapse characterized in animal models of Alzheimer’s disease, and underscores the critical role played by presynaptic stores in normal function.

scholarly journals Rapid regulation of vesicle priming explains synaptic facilitation despite heterogeneous vesicle:Ca2+ channel distances

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Janus RL Kobbersmed ◽  
Andreas T Grasskamp ◽  
Meida Jusyte ◽  
Mathias A Böhme ◽  
Susanne Ditlevsen ◽  
...  
Keyword(s):  
Super Resolution ◽  
Release Site ◽  
Stochastic Simulations ◽  
Short Term ◽  
Short Term Plasticity ◽  
Release Probability ◽  
Vesicular Release ◽  
Dependent Inhibition ◽  
Super Resolution Microscopy ◽  
Activity Dependent

Chemical synaptic transmission relies on the Ca2+-induced fusion of transmitter-laden vesicles whose coupling distance to Ca2+ channels determines synaptic release probability and short-term plasticity, the facilitation or depression of repetitive responses. Here, using electron- and super-resolution microscopy at the Drosophila neuromuscular junction we quantitatively map vesicle:Ca2+ channel coupling distances. These are very heterogeneous, resulting in a broad spectrum of vesicular release probabilities within synapses. Stochastic simulations of transmitter release from vesicles placed according to this distribution revealed strong constraints on short-term plasticity; particularly facilitation was difficult to achieve. We show that postulated facilitation mechanisms operating via activity-dependent changes of vesicular release probability (e.g. by a facilitation fusion sensor) generate too little facilitation and too much variance. In contrast, Ca2+-dependent mechanisms rapidly increasing the number of releasable vesicles reliably reproduce short-term plasticity and variance of synaptic responses. We propose activity-dependent inhibition of vesicle un-priming or release site activation as novel facilitation mechanisms.

scholarly journals Regulation of a subset of release-ready vesicles by the presynaptic protein Mover

2021 ◽  
Vol 118 (3) ◽  
pp. e2022551118
Author(s):  
Ermis Pofantis ◽  
Erwin Neher ◽  
Thomas Dresbach
Keyword(s):  
Synaptic Vesicles ◽  
Wild Type ◽  
Short Term ◽  
Calyx Of Held ◽  
Short Term Plasticity ◽  
Release Probability ◽  
Pulse Ratio ◽  
Vesicular Release ◽  
Evolutionarily Conserved ◽  
Presynaptic Protein

Neurotransmitter release occurs by regulated exocytosis from synaptic vesicles (SVs). Evolutionarily conserved proteins mediate the essential aspects of this process, including the membrane fusion step and priming steps that make SVs release-competent. Unlike the proteins constituting the core fusion machinery, the SV protein Mover does not occur in all species and all synapses. Its restricted expression suggests that Mover may modulate basic aspects of transmitter release and short-term plasticity. To test this hypothesis, we analyzed synaptic transmission electrophysiologically at the mouse calyx of Held synapse in slices obtained from wild-type mice and mice lacking Mover. Spontaneous transmission was unaffected, indicating that the basic release machinery works in the absence of Mover. Evoked release and vesicular release probability were slightly reduced, and the paired pulse ratio was increased in Mover knockout mice. To explore whether Mover’s role is restricted to certain subpools of SVs, we analyzed our data in terms of two models of priming. A model assuming two SV pools in parallel showed a reduced release probability of so-called “superprimed vesicles” while “normally primed” ones were unaffected. For the second model, which holds that vesicles transit sequentially from a loosely docked state to a tightly docked state before exocytosis, we found that knocking out Mover selectively decreased the release probability of tight state vesicles. These results indicate that Mover regulates a subclass of primed SVs in the mouse calyx of Held.

Distinct Transmitter Release Properties Determine Differences in Short-Term Plasticity at Functional and Silent Synapses

2006 ◽  
Vol 95 (5) ◽  
pp. 3024-3034 ◽  
Author(s):  
Carolina Cabezas ◽  
Washington Buño
Keyword(s):  
Transmitter Release ◽  
Molecular Mechanisms ◽  
Long Term Potentiation ◽  
Lower Percentage ◽  
Functional Importance ◽  
Short Term ◽  
Short Term Plasticity ◽  
Silent Synapses ◽  
Term Potentiation

Recent evidence suggests that functional and silent synapses are not only postsynaptically different but also presynaptically distinct. The presynaptic differences may be of functional importance in memory formation because a proposed mechanism for long-term potentiation is the conversion of silent synapses into functional ones. However, there is little direct experimentally evidence of these differences. We have investigated the transmitter release properties of functional and silent Schaffer collateral synapses and show that on the average functional synapses displayed a lower percentage of failures and higher excitatory postsynaptic current (EPSC) amplitudes than silent synapses at +60 mV. Moreover, functional but not silent synapses show paired-pulse facilitation (PPF) at +60 mV and thus presynaptic short-term plasticity will be distinct in the two types of synapse. We examined whether intraterminal endoplasmic reticulum Ca2+ stores influenced the release properties of these synapses. Ryanodine (100 μM) and thapsigargin (1 μM) increased the percentage of failures and decreased both the EPSC amplitude and PPF in functional synapses. Caffeine (10 mM) had the opposite effects. In contrast, silent synapses were insensitive to both ryanodine and caffeine. Hence we have identified differences in the release properties of functional and silent synapses, suggesting that synaptic terminals of functional synapses express regulatory molecular mechanisms that are absent in silent synapses.

scholarly journals Release probability modulates short‐term plasticity at a rat giant terminal

2000 ◽  
Vol 524 (2) ◽  
pp. 513-523 ◽  
Author(s):  
Sharon Oleskevich ◽  
John Clements ◽  
Bruce Walmsley
Keyword(s):  
Short Term ◽  
Short Term Plasticity ◽  
Release Probability

Short-Term Dynamics of Synaptic Transmission Within the Excitatory Neuronal Network of Rat Layer 4 Barrel Cortex

2002 ◽  
Vol 87 (6) ◽  
pp. 2904-2914 ◽  
Author(s):  
Carl C. H. Petersen
Keyword(s):  
Synaptic Transmission ◽  
Dynamic Behavior ◽  
Neuronal Network ◽  
Action Potentials ◽  
Time Course ◽  
Barrel Cortex ◽  
Short Term ◽  
Short Term Plasticity ◽  
Layer 4 ◽  
Detection Of Objects

The short-term plasticity of synaptic transmission between excitatory neurons within a barrel of layer 4 rat somatosensory neocortex was investigated. Action potentials in presynaptic neurons at frequencies ranging from 1 to 100 Hz evoked depressing postsynaptic excitatory postsynaptic potentials (EPSPs). Recovery from synaptic depression followed an exponential time course with best-fit parameters that differed greatly between individual synaptic connections. The average maximal short-term depression was close to 0.5 with a recovery time constant of around 500 ms. Analysis of each individual sweep showed that there was a correlation between the amplitude of the response to the first and second action potentials such that large first EPSPs were followed by smaller than average second EPSPs and vice versa. Short-term depression between excitatory layer 4 neurons can thus be termed use dependent. A simple model describing use-dependent short-term plasticity was able to closely simulate the experimentally observed dynamic behavior of these synapses for regular spike trains. More complex irregular trains of 10 action potentials occurring within 500 ms were initially well described, but during the train errors increased. Thus for short periods of time the dynamic behavior of these synapses can be predicted accurately. In conjunction with data describing the connectivity, this forms a first step toward computational modeling of the excitatory neuronal network of layer 4 barrel cortex. Simulation of whisking-evoked activity suggests that short-term depression may provide a mechanism for enhancing the detection of objects within the whisker space.

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