Abstract
Gamma frequency network oscillations are assumed to be important in cognitive processes, including hippocampal memory operations, but the precise functions of these oscillations remain unknown. Here, we examine the cellular and network mechanisms underlying carbachol-induced fast network oscillations in the hippocampus in vitro, which closely resemble hippocampal gamma oscillations in the behaving rat. Using a combination of planar multielectrode array recordings, imaging with voltage-sensitive dyes, and recordings from single hippocampal neurons within the CA3 gamma generator, active current sinks and sources were localized to the stratum pyramidale. These proximal currents were driven by phase-locked rhythmic inhibitory inputs to pyramidal cells from identified perisomatic-targeting interneurons. AMPA receptor-mediated recurrent excitation was necessary for the synchronization of interneuronal discharge, which strongly supports a synaptic feedback model for the generation of hippocampal gamma oscillations.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Action Potentials / drug effects
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Action Potentials / physiology
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Animals
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Biological Clocks / drug effects
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Biological Clocks / physiology*
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Carbachol / pharmacology
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Cholinergic Agonists / pharmacology
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Cholinergic Fibers / physiology*
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Feedback / drug effects
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Feedback / physiology
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Fluorescent Dyes
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Hippocampus / physiology*
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Interneurons / drug effects
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Interneurons / physiology
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Models, Neurological
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Nerve Net / drug effects
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Nerve Net / physiology*
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Neural Inhibition / drug effects
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Neural Inhibition / physiology*
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Neural Pathways / drug effects
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Neural Pathways / physiology*
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Organ Culture Techniques
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Patch-Clamp Techniques
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Pyramidal Cells / drug effects
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Pyramidal Cells / physiology
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Rats
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Rats, Wistar
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Receptors, AMPA / agonists
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Receptors, AMPA / metabolism
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Receptors, Muscarinic / drug effects
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Receptors, Muscarinic / metabolism
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Synaptic Transmission / drug effects
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Synaptic Transmission / physiology
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Time Factors
Substances
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Cholinergic Agonists
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Fluorescent Dyes
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Receptors, AMPA
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Receptors, Muscarinic
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Carbachol