Analyzing Synaptic Vesicle Recycling and Fluorescent Dye Uptake in <em>Drosophila</em> Larvae

Source: Kopke, D. L., et al., FM Dye Cycling at the Synapse: Comparing High Potassium Depolarization, Electrical and Channelrhodopsin Stimulation. J. Vis. Exp. (2018). This video demonstrates a protocol to study synaptic vesicle recycling at neuromuscular junctions in channelrhodopsin-expressing Drosophila larvae using a fluorescent dye. Blue light activates the channelrhodopsins, causing calcium influx and synaptic vesicle exocytosis. The dye integrates into the neuronal membranes and is internalized during endocytosis, resulting in enhanced fluorescence. Further blue light stimulation induces exocytosis and dye release, which is shown by reduced fluorescence.