Figure 2.

Arc expression before (HC) and after (5 min and 30 min) re-exposure to the training context. Sections are from mice that were sacrificed 1 d after training with shock. For 5 min and 30 min, mice were returned to their home cage after exposure to context S on Day 2 for 5 min and 30 min before sacrifice, respectively. Nuclei are blue and Arc RNA is green. Almost no labeling is present in HC. At 5 min, small intranuclear foci of labeled Arc RNA are present in some neurons in each brain region. At 30 min, perinuclear cytoplasmic labeling of Arc mRNA is present and intranuclear labeling is similar to that for HC. Regions are as per Figure 1. The scale bar is 40 μm for all regions except dCA3 and dCA1, where it is 20 μm.