Figure 2. γ-DGG reduces the EPSC amplitude, unmasks facilitation, and reduces short-term depression. Ai, Effect of γ-DGG on the amplitude of a single EPSC. Traces are mean of 20 EPSCs in the absence (control) and presence of either 2 or 4 mm γ-DGG. Aii, EPSC amplitudes in the presence ofγ-DGG normalized to the peak EPSC in control conditions. B–D, Effect ofγ-DGG on the EPSC amplitude during a 50 Hz train. Control (B),γ-DGG (C), and normalized data (D) from two different neurons are shown in i and ii. Bi, Control. After an initial large EPSC, there is rapid depression to a low steady-state level (< 10% of initial EPSC amplitude), which is maintained throughout the train. Bii, Control. In this neuron, the EPSC declines slowly, and the relative steady-state amplitude is greater than that for i, being 50% of initial EPSC amplitude. C, Bath application of 4 mm γ-DGG reduces EPSC amplitude by 85% in both neurons (Ci, Cii). Di, The trace shown in Ci is scaled to the amplitude of the first EPSC in the control train (Bi). The amplitude of the steady-state EPSCs is higher with respect to the first EPSC. ii, The trace shown in Cii is scaled to the amplitude of the first EPSC in the control train (Bii). The EPSC now facilitates from the second to the eighth stimulus and then depresses, but to a higher steady-state amplitude relative to control.