Subcellular resolution imaging in neural circuits

Drosophila combines advanced genetics with a brain of ideal size for high-resolution imaging in toto. However, imaging of intracellular compartments pushes the limits of light microscopy in every system, and at the subcellular level the small size of fly neurons presents a challenge. In this chapter, we review recent imaging advances that, often for the first time, allow the visualization of intracellular biology of neurons in the context of their neuronal circuits. We discuss the different preparations that keep neural circuit architectures intact for live and fixed imaging. Finally, we review advances in light microscopy and imaging probes in combination with these preparations and provide a guide to which high-resolution microscopy techniques are applicable to the different Drosophila preparations. We focus on the imaging of intracellular membrane trafficking dynamics. However, since any imaging of intracellular trafficking constitutes an example of imaging at subcellular resolution, many approaches discussed here will be useful for the study of neuronal cell biology in Drosophila in general.