The upregulation of mEPSCs does not persist if AP bursting is blocked immediately after the 15 minute induction period. (A) Stimulation protocol used to block action potential bursting with TTX (1 μM) immediately after the 15 minute bicuculline application in presence or absence of actinomycin D (8 μM) which was applied 15 minutes prior to bicuculline and left on the cells for 2 hours after bicuculline washout (see Methods). The time line indicates the time window when mEPSCs were recorded after washout of bicuculline. (B) The histogram shows mean values of mEPSC IEI of vehicle (white) or bicuculline (grey or black) treated cells in the presence (dashed border) or absence (solid border) of actinomycin D that were either transferred to TTX (black) or not (grey) immediately after bicuculline washout. Data are separated into three groups to illustrate the time course of IEI-modulation by TTX application immediately after bicuculline stimulation. Numbers within columns represent n of cells per group. * p < 0.05, ** p < 0.01.