Brilliant Yellow is a competitive inhibitor with glutamate for VGLUT. Synaptic vesicles were pre-incubated with 0, 40, and 80 nM Brilliant Yellow, followed by addition of a mixture of ATP and various concentrations of [3H]glutamate, with an additional 1.5- min incubation, as described in Materials and Methods. This represents a mean of three experimental data. v, initial rate of vesicular glutamate uptake; BY, Brilliant Yellow.