MPO and ischemia: Despite the lack of astroglial activation, microglial reactivity (Iba1-positive cells), and infiltrating neutrophils, measured as the level of MPO, in the hippocampal CA1 region after 12 min of global ischemia and seven days of reperfusion, was significantly elevated (p < 0.01) in young and aged IP KO ischemic mice compared to WT ischemic counterparts (p < 0.01) (Figure 5, Figure 6).