The persistence but not the induction of AP bursting over the 10 hour post induction period is transcription-dependent. (A) Western blot experiments showing the induction of the immediate-early gene c-fos either 2 hours or 30 minutes after a 15 minute period of bicuculline (50 μM) treatment in the presence or absence of actinomycin D (Act D, 8 μM). The histogram represents the intensities of the c-fos expression level relative to unstimulated control conditions. Endogenous calmodulin serves as loading control. (B) Histograms show the proportion of neurons exhibiting either bursting or random/silent activity patterns the 10 hours after a 15 min period of bicuculline or vehicle treatment in control and actinomycin D (ActD) treated neurons. Total neuron numbers in each group are indicated above each bar. (C) The bursting incidence data shown in B is separated into 6 groups to illustrate the time course of its modulation. Neuron numbers per group are indicated above each data point.