Research article summary (published 30 Aug 2005):

Synapse independence breaks down during highly synchronous network activity in the rat hippocampus.

Full Abstract

The discharge pattern of hippocampal pyramidal cells (PC) varies depending on the behaviour of the animal and on the accompanying network states. During theta activity, PCs fire asynchronously at low rates whereas during sharp waves PCs increase their firing frequency and many cells fire synchronously. In the present study, we addressed how the presynaptic activity of CA1 PCs influences the precise operation of their output synapses. Asynchronous presynaptic discharge was mimicked by activating only a single PC during paired recordings, whereas the highly synchronous presynaptic firing was emulated by extracellularly stimulating the axons of approximately 70 PCs in acute hippocampal slices. By using low- and high-affinity glutamate receptor competitive antagonists to monitor the synaptic glutamate concentration transient, we show that the synaptic transmitter concentration varies depending on the release probability (P(r)) when many fibres are synchronously activated. Our kinetic analysis revealed that an approximately 5-fold increase in P(r) from the beginning to the end of an action potential train resulted in a slowing down of the decay of evoked EPSCs, suggesting neurotransmitter spillover between neighbouring synapses. In agreement with this prediction, the slowing of the decay was reversed by the application of the low-affinity antagonist gamma-D-glutamyl-glycine. In contrast, altering P(r) had no effect on the kinetics of unitary EPSCs. Our data demonstrate that synapse independence breaks down during synchronous presynaptic activity, but the point-to-point communication is preserved when PCs fire asynchronously.

Author information

Author/s: Biró, Agota A (AA); Nusser, Zoltan (Z);

Affiliation: Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Szigony Street 43, 1083 Budapest, Hungary.

Grants: 070213 (Agency:Wellcome Trust) ; (Agency:Wellcome Trust)

Journal and publication information

Publication Type: Comparative Study; In Vitro; Journal Article; Research Support, Non-U.S. Gov't

Journal: The European journal of neuroscience (Eur J Neurosci), published in France. (Language: eng)

Reference: 2005-Sep; vol 22 (issue 5) : pp 1257-62

Dates: Created 2005/09/22; Completed 2006/01/10; Revised 2008/11/20;

PMID: 16176369, status: MEDLINE (last retrieval date: 2/18/2009, IMS Date: )

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

6-Cyano-7-nitroquinoxaline-2,3-dione - pharmacology Animals Animals, Newborn Electric Stimulation - methods Excitatory Amino Acid Antagonists - pharmacology Excitatory Postsynaptic Potentials - drug effects; physiology; radiation effects Hippocampus - cytology Male

Male Nerve Net - drug effects; physiology; radiation effects Oligopeptides - pharmacology Patch-Clamp Techniques - methods Presynaptic Terminals - physiology Pyramidal Cells - drug effects; physiology; radiation effects Rats Synapses - drug effects; physiology; radiation effects

Associated Chemicals: Excitatory Amino Acid Antagonists (0) ; Oligopeptides (0) ; 6-Cyano-7-nitroquinoxaline-2,3-dione (115066-14-3) ; glutamyl-aspartyl-glycine (75007-24-8)

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