Single-Molecule Imaging of Recycling Synaptic Vesicles in Live Neurons

The capacity of neurons to communicate and store information in the brain critically depends on neurotransmission, a process which relies on the release of chemicals called neurotransmitters stored in synaptic vesicles at the presynaptic nerve terminals. Following their fusion with the presynaptic plasma membrane, synaptic vesicles are rapidly reformed via compensatory endocytosis. The investigation of the endocytic pathway dynamics is severely restricted by the diffraction limit of light and, therefore, the recycling of synaptic vesicles, which are roughly 45 nm in diameter, has been primarily studied with electrophysiology, low-resolution fluorescence-based techniques, and electron microscopy. Here, we describe a recently developed technique we named subdiffractional tracking of internalized molecules (sdTIM) that can be used to track and study the mobility of recycling synaptic vesicles in live hippocampal presynapses. The chapter provides detailed guidelines on the application of the sdTIM protocol and highlights controls, adaptations, and limitations of the technique