CLDN5 and ischemia: Although both groups had similar levels of claudin-5 at 1-day post dMCAO (old vs. young: 0.19±0.03 vs. 0.23±0.02, p=0.32), at 3 days post-ischemia, the old group had a lower level of claudin-5 than the young group (old vs. young: 0.22±0.03 vs. 0.3±0.05, p=0.0096, Fig. 4B).