ArgI localization in the cerebral cortex of WT and ApoE−/− mice. Representative images of ArgI staining (in red) in frontal cerebral cortex from young (A, E, I, M) and old (B, F, J, N) WT mice and from young (C, G, K, O) and old (D, H, L, P) ApoE−/− mice (n = 6 per group). Single staining is shown in the first (A-D) and last row (M-P). Arrows show a vascular localization. Arrowheads show a nuclear localization in extravascular cells. Double staining with NeuN (in blue) and laminin (in green) are shown on the second and third row, respectively. Scale bar = 100 μm in A to L and 40 μm in M to P.