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Vol. 343 ,
- 6 March 2014 1:04 pm , Vol. 343 , #6175
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ScienceShot: Lightning-Fast Recycling
4 December 2013 1:00 pm
A lot happens in the instant you yank your hand away from a hot stove. Your neurons fire, releasing hundreds of bubbles filled with chemicals called neurotransmitters (orange in artist’s conception above) into a microscopic junction called a synapse, which connects the cell to its neighbor. Then the bubbles reform (yellow), and the whole process begins again. Now it turns out the process is even faster than scientists thought. By genetically programming mouse neurons to fire in response to flashes of blue light, freezing them with liquid nitrogen at millisecond intervals, and photographing them with an electron microscope, a team of researchers has discovered that the whole thing happens in about 100 milliseconds—up to 200 times quicker than previously proposed mechanisms. Rather than using a protein to facilitate the process by building a scaffold for the vesicles, or another proposed mechanism called "kiss-and-run," in which vesicles merely "kiss" the inside of the first neuron, briefly merging with it and emptying their contents into the synapse, the researchers found that vesicles are fully formed, then recycled to form new bubbles only one-tenth of a second after they release their cargo into the synapse. This near-instantaneous recycling is likely what makes the nervous system so fast and its function so seamless, the scientists report today in Nature. They say studying the process could enhance our understanding of neurodegenerative conditions such as Alzheimer's disease.