“Kiss-and-Run” Glutamate Secretion in Cultured and Freshly Isolated Rat Hippocampal Astrocytes
- Xiaoke Chen1,2,
- Liecheng Wang1,2,
- Yang Zhou1,2,
- Liang-Hong Zheng1,2,3, and
- Zhuan Zhou1,2,3
- 1Institute of Molecular Medicine, Peking University, Beijing 100871, China, 2Institute of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China, and 3State Key Laboratory of Biomembrane Engineering, College of Life Sciences, Peking University, Beijing 100871, China
Abstract
Under physiological conditions, astrocytes not only passively support and nourish adjacent neurons, but also actively modulate neuronal transmission by releasing “glial transmitters,” such as glutamate, ATP, and d-serine. Unlike the case for neurons, the mechanisms by which glia release transmitters are essentially unknown. Here, by using electrochemical amperometry and frequency-modulated single-vesicle imaging, we discovered that hippocampal astrocytes exhibit two modes of exocytosis of glutamate in response to various stimuli. After physiological stimulation, a glial vesicle releases a quantal content that is only 10% of that induced by nonphysiological, mechanical stimulation. The small release event arises from a brief (∼2 ms) opening of the fusion pore. We conclude that, after physiological stimulation, astrocytes release glutamate via a vesicular “kiss-and-run” mechanism.
- Received April 26, 2005.
- Revision received August 22, 2005.
- Accepted August 23, 2005.
