Article abstract
Nature Neuroscience 10, 321 - 330 (2007)
Published online: 11 February 2007 | doi:10.1038/nn1854
Vesicular release of glutamate from unmyelinated axons in white matter
Jennifer L Ziskin1, Akiko Nishiyama2, Maria Rubio2, Masahiro Fukaya3 & Dwight E Bergles1
Abstract
Directed fusion of transmitter-laden vesicles enables rapid intercellular signaling in the central nervous system and occurs at synapses within gray matter. Here we show that action potentials also induce the release of glutamate from axons in the corpus callosum, a white matter region responsible for interhemispheric communication. Callosal axons release glutamate by vesicular fusion, which induces quantal AMPA receptor–mediated currents in NG2+ glial progenitors at anatomically distinct axo–glial synaptic junctions. Glutamate release from axons was facilitated by repetitive stimulation and could be inhibited through activation of metabotropic autoreceptors. Although NG2+ cells form associations with nodes of Ranvier in white matter, measurements of conduction velocity indicated that unmyelinated fibers are responsible for glutamatergic signaling with NG2+ glia. This activity-dependent secretion of glutamate was prevalent in the developing and mature mouse corpus callosum, indicating that axons within white matter both conduct action potentials and engage in rapid neuron-glia communication.
- Department of Neuroscience, Johns Hopkins University School of Medicine, 725 N. Wolfe St., WBSB 813, Baltimore, Maryland 21205, USA.
- Department of Neurobiology and Physiology, University of Connecticut, 75 North Eagleville Road, Unit 3156, Storrs, Connecticut 06269-3156, USA.
- Department of Anatomy, Hokkaido University Graduate School of Medicine, Sapporo, 060-8638 Japan.
Correspondence to: Dwight E Bergles1 e-mail: dbergles@jhmi.edu
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