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Modulatory effects of oligodendrocytes on the conduction velocity of action potentials along axons in the alveus of the rat hippocampal CA1 region

Published online by Cambridge University Press:  01 April 2008

Yoshihiko Yamazaki
Affiliation:
Department of Neurophysiology, Yamagata University School of Medicine, Yamagata 990-9585, Japan
Yasukazu Hozumi
Affiliation:
Department of Anatomy & Cell Biology, Yamagata University School of Medicine, Yamagata 990-9585, Japan
Kenya Kaneko
Affiliation:
Department of Neurophysiology, Yamagata University School of Medicine, Yamagata 990-9585, Japan
Toshimichi Sugihara
Affiliation:
Department of Neurophysiology, Yamagata University School of Medicine, Yamagata 990-9585, Japan
Satoshi Fujii
Affiliation:
Department of Neurophysiology, Yamagata University School of Medicine, Yamagata 990-9585, Japan
Kaoru Goto
Affiliation:
Department of Anatomy & Cell Biology, Yamagata University School of Medicine, Yamagata 990-9585, Japan
Hiroshi Kato
Affiliation:
Department of Neurophysiology, Yamagata University School of Medicine, Yamagata 990-9585, Japan

Abstract

Like neurons and astrocytes, oligodendrocytes have a variety of neurotransmitter receptors and ion channels. However, except for facilitating the rapid conduction of action potentials by forming myelin and buffering extracellular K+, little is known about the direct involvement of oligodendrocytes in neuronal activities. To investigate their physiological roles, we focused on oligodendrocytes in the alveus of the rat hippocampal CA1 region. These cells were found to respond to exogenously applied glutamate by depolarization through N-methyl-D-aspartate (NMDA) receptors and non-NMDA receptors. Electrical stimulation of the border between the alveus and stratum oriens evoked inward currents through several routes involving glutamate receptors and inward rectifier K+ channels. Moreover, electrical stimulation resembling in vivo activity evoked long-lasting depolarization. To examine the modulatory effects of oligodendrocytes on neuronal activities, we performed dual, whole-cell recording on CA1 pyramidal neurons and oligodendrocytes. Direct depolarization of oligodendrocytes shortened the latencies of action potentials evoked by antidromic stimulation. These results indicate that oligodendrocytes increase the conduction velocity of action potentials by a mechanism additional to saltatory conduction, and that they have active roles in information processing in the brain.

Type
Research Article
Copyright
Copyright © Cambridge University Press 2007

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