Effect of estrogen on infarction volume in PARP-/- females. Physiological levels of E2 were restored to ovariectomized (OVX) PARP-/- and WT female mice. WT females had significant reductions in total, cortical (CTX) and striatal (CP) infarct volumes after E2 replacement compared to oil treated WT females (*; p < .01). PARP-/- females demonstrated increased damage compared to WT (**; p < .01). Interestingly the neuroprotective effect of E2 was completely absent in PARP -/- females. E2 treatment exacerbated stroke damage; both striatal and total infarct volumes were significantly higher in E2 treated vs. oil treated PARP-/- mice (***; p < .05) .