Fluoro-Gold: a new fluorescent retrograde axonal tracer with numerous unique properties.

A new fluorescent dye, Fluoro-Gold, has been demonstrated to undergo retrograde axonal transport. Its properties include intense fluorescence, extensive filling of dendrites, high resistance to fading, no uptake by intact undamaged fibers of passage, no diffusion from labeled cells, consistent and pure commercial source, wide latitude of survival times and compatibility with all other tested neuro-histochemical techniques.