RT Journal Article
SR Electronic
T1 SNARE Protein-Dependent Glutamate Release from Astrocytes
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 666
OP 673
DO 10.1523/JNEUROSCI.20-02-00666.2000
VO 20
IS 2
A1 Araque, Alfonso
A1 Li, Nianzhen
A1 Doyle, Robert T.
A1 Haydon, Philip G.
YR 2000
UL http://www.jneurosci.org/content/20/2/666.abstract
AB We investigated the cellular mechanisms underlying the Ca2+-dependent release of glutamate from cultured astrocytes isolated from rat hippocampus. Using Ca2+imaging and electrophysiological techniques, we analyzed the effects of disrupting astrocytic vesicle proteins on the ability of astrocytes to release glutamate and to cause neuronal electrophysiological responses, i.e., a slow inward current (SIC) and/or an increase in the frequency of miniature synaptic currents. We found that the Ca2+-dependent glutamate release from astrocytes is not caused by the reverse operation of glutamate transporters, because the astrocyte-induced glutamate-mediated responses in neurons were affected neither by inhibitors of glutamate transporters (β-threo-hydroxyaspartate, dihydrokainate, andl-trans-pyrrolidine-2,4-dicarboxylate) nor by replacement of extracellular sodium with lithium. We show that Ca2+-dependent glutamate release from astrocytes requires an electrochemical gradient necessary for glutamate uptake in vesicles, because bafilomycin A1, a vacuolar-type H+-ATPase inhibitor, reduced glutamate release from astrocytes. Injection of astrocytes with the light chain of the neurotoxin Botulinum B that selectively cleaves the vesicle-associated SNARE protein synaptobrevin inhibited the astrocyte-induced glutamate response in neurons. Therefore, the Ca2+-dependent glutamate release from astrocytes is a SNARE protein-dependent process that requires the presence of functional vesicle-associated proteins, suggesting that astrocytes store glutamate in vesicles and that it is released through an exocytotic pathway.