Fig. 3.

Regulation of arg3.1/arc and c-fostranscription by cAMP. Autoradiographs are of Northern blots. RNA amounts and labels are as in Figure 2. Cells were stimulated with the adenylyl cyclase activator forskolin (50 μm).A, B, RNA isolated from PC12 cells (n = 4). Where indicated, cells in Bwere exposed to 3 mm of the transcription inhibitor actinomycin D (ActD), 1.25 and 4.25 hr before lysis, or 15 min before stimulation with forskolin, respectively.C, RNA isolated from NIH3T3 fibroblasts (n = 2). D, RNA isolated from Neuro2a neuroblastoma cells (n = 2). Note that arg3.1/arc is induced by forskolin in PC12 cells but not in NIH3T3 or Neuro2a cells.