Postsynaptic hyperpolarization increases the strength of AMPA-mediated synaptic transmission at large synapses between mossy fibers and CA3 pyramidal cells

Nicola Berretta, Aleksej V. Rossokhin, Alexander M. Kasyanov, Maxim V. Sokolov, Enrico Cherubini, Leon L. Voronin

Research output: Contribution to journalArticle

Abstract

In chemical synapses information flow is polarized. However, the postsynaptic cells can affect transmitter release via retrograde chemical signaling. Here we explored the hypothesis that, in large synapses, having large synaptic cleft resistance, transmitter release can be enhanced by electrical (ephaptic) signaling due to depolarization of the presynaptic release site induced by the excitatory postsynaptic current itself. The hypothesis predicts that, in such synapses, postsynaptic hyperpolarization would increase response amplitudes 'supralinearly', i.e. stronger than predicted from the driving force shift. We found supralinear increases in the amplitude of minimal excitatory postsynaptic potential (EPSP) during hyperpolarization of CA3 pyramidal neurons. Failure rate, paired-pulse facilitation, coefficient of variation of the EPSP amplitude and EPSP quantal content were also modified. The effects were especially strong on mossy fiber EPSPs (MF-EPSPs) mediated by the activation of large synapses and identified pharmacologically or by their kinetics. The effects were weaker on commissural fiber EPSPs mediated by smaller and more remote synapses. Even spontaneous membrane potential fluctuations were associated with supralinear MF-EPSP increases and failure rate reduction. The results suggest the existence of a novel mechanism for retrograde control of synaptic efficacy from postsynaptic membrane potential and are consistent with the ephaptic feedback hypothesis. Copyright (C) 2000 Elsevier Science Ltd.

Original languageEnglish
Pages (from-to)2288-2301
Number of pages14
JournalNeuropharmacology
Volume39
Issue number12
DOIs
Publication statusPublished - Nov 2000

Keywords

  • CA3 synapses
  • Ephaptic feedback
  • Failures
  • Postsynaptic membrane potential
  • Quantal analysis
  • Retrograde signaling

ASJC Scopus subject areas

  • Cellular and Molecular Neuroscience
  • Drug Discovery
  • Pharmacology

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