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Related Concept Videos

Chemical Synapses01:26

Chemical Synapses

Chemical synapses are specialized sites between two neurons or between a neuron and a non-neuronal cell like a muscle, glandular or sensory cell.
Because chemical synapses depend on the release of neurotransmitter molecules from synaptic vesicles to pass on their signal, there is an approximately one millisecond delay between when the axon potential reaches the presynaptic terminal and when the neurotransmitter leads to opening of postsynaptic ion channels. Additionally, this signaling is...
Chemical Synapses01:26

Chemical Synapses

Chemical synapses are specialized sites between two neurons or between a neuron and a non-neuronal cell like a muscle, glandular or sensory cell.
Because chemical synapses depend on the release of neurotransmitter molecules from synaptic vesicles to pass on their signal, there is an approximately one millisecond delay between when the axon potential reaches the presynaptic terminal and when the neurotransmitter leads to opening of postsynaptic ion channels. Additionally, this signaling is...
The Synapse02:47

The Synapse

Neurons communicate with one another by passing on their electrical signals to other neurons. A synapse is the location where two neurons meet to exchange signals. At the synapse, the neuron that sends the signal is called the presynaptic cell, while the neuron that receives the message is called the postsynaptic cell. Note that most neurons can be both presynaptic and postsynaptic, as they both transmit and receive information.
Electrical Synapses01:28

Electrical Synapses

Electrical synapses found in all nervous systems play important and unique roles. In these synapses, the presynaptic and postsynaptic membranes are very close together (3.5 nm) and are actually physically connected by channel proteins forming gap junctions.
Gap junctions allow the current to pass directly from one cell to the next. In contrast, in the chemical synapse, the neurotransmitters carry the information through the synaptic cleft from one neuron to the next. They consist of two...
Synaptic Signaling01:09

Synaptic Signaling

Neurons communicate at synapses, or junctions, to excite or inhibit the activity of other neurons or target cells, such as muscles. Synapses may be chemical or electrical.
Most synapses are chemical, meaning an electrical impulse or action potential spurs the release of chemical messengers called neurotransmitters. The neuron sending the signal is called the presynaptic neuron, and the neuron receiving the signal is the postsynaptic neuron.
The presynaptic neuron fires an action potential that...
Synaptic Signaling01:12

Synaptic Signaling

Neurons communicate at synapses, or junctions, to excite or inhibit the activity of other neurons or target cells, such as muscles. Synapses may be chemical or electrical.

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Correction: Savtchenko, L.P.; Rusakov, D.A. Glutamate-Transporter Unbinding in Probabilistic Synaptic Environment Facilitates Activation of Distant NMDA Receptors. <i>Cells</i> 2023, <i>12</i>, 1610.

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Real-time Electrophysiology: Using Closed-loop Protocols to Probe Neuronal Dynamics and Beyond
08:08

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Published on: June 24, 2015

Bilateral processing in chemical synapses with electrical 'ephaptic' feedback: a theoretical model.

Leonid P Savtchenko1

  • 1Dnepropetrovsk National University and International Center of Molecular Physiology, Dnepropetrovsk Division, Dnepropetrovsk, per. Nauchniy, 15, 49050 Dnepropetrovsk, Ukraine. leon@ff.dsu.dp.ua

Mathematical Biosciences
|November 23, 2006
PubMed
Summary

A new biophysical model reveals positive ephaptic feedback in large central synapses. This mechanism enhances presynaptic action potential widening, boosting calcium influx and synaptic release, and explains previously observed electrical phenomena.

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Area of Science:

  • Neuroscience
  • Biophysics
  • Computational Biology

Background:

  • Chemical synapses are crucial for neural communication.
  • Synaptic transmission involves complex interplay of ion channels and membrane properties.
  • Large central synapses present unique biophysical challenges.

Purpose of the Study:

  • To develop a detailed biophysical model of chemical synapses.
  • To investigate the role of synaptic cleft electrochemical phenomena in action potential (AP) modulation.
  • To elucidate the mechanism of positive ephaptic feedback in synaptic transmission.

Main Methods:

  • Developed a detailed biophysical model of chemical synapses.
  • Incorporated voltage-dependent presynaptic ion channels and synaptic membrane capacitance.
  • Simulated synaptic transmission at synapses with high cleft resistance.

Main Results:

  • Identified electrochemical phenomena within the synaptic cleft that widen presynaptic APs.
  • Demonstrated that AP widening enhances presynaptic calcium (Ca2+) influx and neurotransmitter release probability.
  • Explained the fast capacitance transient observed in postsynaptic cells at the giant calyx synapse.
  • Provided a mechanism for supralinear voltage dependence of EPSCs.

Conclusions:

  • Proposed positive ephaptic feedback as a key mechanism in large central synapses.
  • This feedback loop contributes to basal synaptic transmission and enhances signaling.
  • The model explains previously unexplained experimental observations in synaptic physiology.