Imaging single synaptic vesicles in mammalian central synapses with quantum dots.

This protocol describes a sensitive and rigorous method to monitor the movement and turnover of single synaptic vesicles in live presynaptic terminals of mammalian central nerve system. This technique makes use of fluorescent semiconductor nanocrystals, quantum dots (Qdots), by their nanometer size, superior photoproperties, and pH-sensitivity. In comparison with other fluorescent probes like styryl dyes and pH-sensitive fluorescent proteins, Qdots offer strict loading ratio, multi-modality detection, single vesicle precision, and most importantly distinctive signals for different modes of vesicle recycling. This application is spectrally compatible with existing optical labels for synapses and thus allows multichannel and simultaneous imaging. With easy modification, this technique can be applied to other types of cells.