γ-DGG had no effect on short-term depression during 10 Hz trains but has a marked effect during 50 Hz trains. Average EPSC amplitudes during the train are shown for four cells with EPSC trains at a frequency of 10 and 50 Hz, under control conditions (black diamonds) and in the presence of 4 mm γ-DGG (gray squares). A, Average EPSC amplitude during a 10 Hz train. B, Average EPSC amplitude during a 50 Hz train. C, Normalized EPSC amplitude during a 10 Hz train. Data with and withoutγ-DGG are superimposed and show a 60% depression at 1 sec. D, Normalized EPSC amplitude during a 50 Hz train. At this frequency,γ-DGG unmasks facilitation and reduces depression from 78 to 50% at 1 sec.