Ventral Nerve Cord Dissection and Microscopy of Drosophila Embryos.

The technique of visualizing axon pathways in the embryonic ventral nerve cord using antibody labeling has been fundamental to our understanding of the genetic and developmental mechanisms underlying nervous system wiring in Drosophila. High-resolution microscopic examination of the ventral nerve cord remains an essential component of many experiments in Drosophila developmental neuroscience. Although it is possible to examine the ventral nerve cord in intact whole-mount embryos, to collect the highest-quality images it is often useful to isolate the nervous system away from the other embryonic tissues through embryo dissection. This protocol describes methods for dissecting ventral nerve cords from Drosophila embryos that have been fixed and stained via immunofluorescence or horseradish peroxidase (HRP) immunohistochemistry. The process of making fine dissection needles for this purpose from electrolytically sharpened tungsten wire is also described. Dissected and mounted ventral nerve cords can be examined and imaged using a variety of microscopy techniques including differential interference contrast (DIC) optics, epifluorescence, or confocal microscopy.