Astrocytes can release a variety of transmitters, including glutamate and ATP, in response to stimuli that induce increases in intracellular Ca 2+ levels. This release occurs via a regulated, exocytotic pathway. As evidence of this, astrocytes express protein components of the vesicular secretory apparatus, including synaptobrevin 2, syntaxin, and SNAP-23. Additionally, astrocytes possess vesicular organelles, the essential morphological elements required for regulated Ca2+-dependent transmitter release. The location of specific exocytotic sites on these cells, however, remains to be unequivocally determined. © 2006 Wiley-Liss, Inc.
