Fluorescent Measurement of Synaptic Activity Using FM Dyes in Dissociated Hippocampal Cultured Neurons

Release and recycling of synaptic vesicles are essential for neurotransmission and synaptic plasticity. To gain mechanistic understanding of these processes, direct measurements of vesicle release and retrieval is indispensable. Styryl dyes like FM1-43 and FM4-64 have been widely used for this purpose and their loading and unloading are reliable measurements for synaptic vesicle release and retrieval in cultured neurons. This protocol describes in detail the procedure of using styryl dyes to label and measure synaptic vesicle uptake and release in cultured rat hippocampal neurons. We also include a brief description of hippocampal culture. In the end, we briefly discuss the commonality and difference among FM dye, pH-sensitive fluorescent proteins and quantum dots in terms of measuring synaptic vesicle behavior.