Paired-Pulse Facilitation

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In neurophysiology , especially in electrophysiology , the phenomenon of an intensified postsynaptic response when the presynaptic input is stimulated twice ( paired pulse ) is referred to as paired-pulse facilitation ( English : facilitation for "relief", "facilitation", "support") . It is a form of short-term synaptic plasticity . An example of a synapse with Paired-Pulse Facilitation is the parallel fiber synapse of the Purkinje cell, a synapse between the granule cells and Purkinje cells in the cerebellar cortex .

Paired-Pulse Facilitation only occurs if a certain time interval is not exceeded between the first and second stimulus (usually in the milliseconds to seconds range). As time elapsed between two pulses ( pulse ), the paired-pulse facilitation decays. With frequent stimulation, the amplitude of the postsynaptic response saturates and no further amplification takes place.

It is now considered certain that the paired pulse facilitation is largely caused presynaptically. The response to the second stimulus is greater than that to the first, because in the presynaptic terminal the probability of the transmitter being released is greater than that of the first pulse. The reason for this higher concentration of so-called free calcium - ion , which for activating the exocytosis of synaptic vesicles available.

Paired pulse facilitation is a characteristic property of synapses with a generally low probability of neurotransmitter release (low release probability ). This means that the supply of synaptic vesicles that are immediately available for the fusion ( readily releasable pool ) is not yet exhausted by the first action potential . As a result of the higher calcium concentration after the second action potential has occurred, a higher number of vesicles can then be released or more presynaptic endings take part in the release.

literature

  • Per Andersen: The Hippocampus Book . Oxford University Press, USA, 2007, p. 347 f. ( online )
  • Vivian Budnik, L. Siam Gramates: Neuromuscular Junctions in Drosophila . Academic Press, 1999, p. 60 f. ( online )
  • Laurence O. Trussell, Arthur N. Popper, Richard R. Fay: Synaptic Mechanisms in the Auditory System . Springer Science & Business Media, Heidelberg 2011, p. 77 f. ( online )
  • Pablo Rudomin, Michael A. Arbib, Francisco Cervantes-Perez, Ranulfo Romo: Neuroscience: From Neural Networks to Artificial Intelligence . Springer Science & Business Media, Heidelberg 2012, p. 304 f. ( online )
  • Louis W. Chang, William Slikker, Jr .: Neurotoxicology: Approaches and Methods . Academic Press, 1995, pp. 191 f. ( online )
  • Gerard Meurant: International Review of Neurobiology , Volume 36, pp. 189 f. ( online )

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