Fig. 4.

Effect of aniracetam on synaptic depression.Ai, A single EPSC in 5 mm aniracetam (gray trace). Control peak (black trace) is indicated with an arrow. In this cell, aniracetam increased the peak amplitude by 60% (from −6.19 to −10.24 nA). Aii, A 200 Hz train in control (black trace) and aniracetam (gray trace) is shown. Traces have been normalized to the amplitude of the first peak in each train. Averages of five traces are shown. Bi, Normalized peak amplitudes during 200 Hz stimulus trains (control,black circles; aniracetam, gray circles). Data from 13 cells. Depression is significantly reduced by aniracetam for stimuli 2–10 of trains (p < 0.01; paired t test). Bii, Relative enhancement of EPSC amplitudes by aniracetam throughout the train, calculated as 100% · (EPSC_ANI − EPSC_CON)/EPSC_CON. C, Effect of aniracetam on synaptic depression in the continuous presence of 20 μm Cd²⁺. Ci, EPSC trains at 200 Hz in 20 μm Cd²⁺(black trace) and 20 μmCd²⁺ plus 5 mm aniracetam (gray trace). In this example, aniracetam increased the peak of the first EPSC by 55.8% (from 0.84 to 1.30 nA).Cii, Responses during trains in the presence of Cd²⁺ (black circles) and Cd²⁺ plus aniracetam (gray circles) were normalized to the first response amplitude and plotted versus stimulus number. No effect of aniracetam on synaptic depression was seen when P_R was lowered with 20 μm Cd²⁺ (n = 12).