Increase in Arc RNA expression in the CA1 pyramidal cell layer 30 min after spatial water-task training.a and c show nuclei (blue) and Arc RNA staining (red) for a caged control and a spatial water-task trained rat, respectively.b and d show grayscale images ofArc RNA staining from a andc, respectively. Final magnification is 40×. Scale bars (shown in a and c): 50 μm. See Materials and Methods for experimental details and Table 4 for the summary of the quantitative analyses.