Hydroxystilbamidine has been used extensively as a retrograde tracer for neurons and also a histochemical stain. The 4% solution in deionized H2O is a more convenient, ready-to-use form. If desired, the solution can be diluted to a lower concentration. For most applications, the typically dye concentration is 2% to 4%. FluoroGold is a trademark of Fluorochrome, LLC.