Abstract
Dual whole-cell recordings were made in layer 2/3 of the rat neocortex in synaptically connected pyramidal cells and fast-spiking non-accommodating (FSN) interneurons. In 75% of cell pairs (n = 80), the cells formed reciprocal synaptic connections. Trains of backpropagating action potentials in pyramidal cells induced Ca2+ transients in dendrites followed by inhibition of unitary IPSPs. IPSP depression was prevented by loading pyramidal cells with 5 mM BAPTA or EGTA. IPSP depression was mimicked by the metabotropic glutamate receptor (mGluR) agonist ACPD and was prevented by a mixture of the mGluR antagonists CPCCOEt and EGLU.IPSP depression was prevented by loading pyramidal cells with the antagonists of vesicular exocytosis botulinum toxin D (light chain) and GDP-beta-S. It is concluded that Ca2+-dependent release of a retrograde messenger, most probably glutamate, from pyramidal cell dendrites suppresses the inhibition of pyramidal neurons via activation of mGluRs located in FSN interneuron nerve terminals.
MeSH terms
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Action Potentials / physiology
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Animals
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Botulinum Toxins / pharmacology
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Calcium / metabolism
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Cycloleucine / analogs & derivatives
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Cycloleucine / pharmacology
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Dendrites / metabolism*
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Egtazic Acid / analogs & derivatives
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Egtazic Acid / pharmacology
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Electrophysiology
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Glutamic Acid / physiology*
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Guanosine Diphosphate / analogs & derivatives*
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Guanosine Diphosphate / pharmacology
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Interneurons / physiology
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Neocortex / cytology
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Neocortex / physiology*
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Neural Inhibition / physiology*
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Pyramidal Cells / physiology*
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Rats
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Rats, Wistar
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Receptors, Metabotropic Glutamate / agonists
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Receptors, Metabotropic Glutamate / antagonists & inhibitors
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Synapses / physiology*
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Synaptic Transmission / drug effects
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Synaptic Transmission / physiology
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Thionucleotides / pharmacology
Substances
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Receptors, Metabotropic Glutamate
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Thionucleotides
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Cycloleucine
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1-amino-1,3-dicarboxycyclopentane
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Guanosine Diphosphate
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botulinum toxin type D
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Glutamic Acid
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Egtazic Acid
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guanosine 5'-O-(2-thiodiphosphate)
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Botulinum Toxins
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1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid
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Calcium