Iontophoretic injection of fluoro-gold and other fluorescent tracers.

Fluoro-gold, a retrograde axonally transported fluorescent tracer, has been successfully iontophoresed into brain regions to yield small injection sites with no detectable dye along the track. Previous difficulties involving iontophoretic application of fluoro-gold were overcome through the use of a cacodylate vehicle. This vehicle was also found to be suitable for iontophoresing other fluorescent tracers, such as propidium iodide or Fast Blue.