In the Normo + ischemia group, HO-1 immunoreactivity was not altered until 12 h after ischemia (Figure 2Ab,c,C) and increased in cells throughout all layers of CA1 from 1 day after ischemia (Figure 2Ad–f), showing that the relative optical density (ROD) of HO-1 immunoreactivity was 154.0% at 2 days and 310.1% at 5 days after ischemia compared with that in the Normo + sham group (Figure 2C). Here, HMOX1 is linked to ischemia.