Photoablating neuronal groups using an intracellularly aggregating dye

We report here on a new method to kill several selected neurons, using a modified fluorescence photoablation technique that does not require impaling any cells. Rather, we injected extracellularly the dye rhodamine 6-G, which is taken up by the cells. We made our injections into one side of a cockroach ganglion, after which the nearby cell bodies of individually known giant interneurons (GIs), as well as other cell bodies and many axons, became highly fluorescent. After this dye accumulation, we irradiated either the entire ganglionic region of the accumulated dye, or specifically the cell bodies of two identified GIs. After allowing over one week for axonal degeneration, both histological and behavioral tests confirmed that specifically the axons of the targeted illuminated cells had been killed.