Poly(ADP-ribose) polymerase plays an important role in cell survival and death. Our previous histological and ultrastructural studies showed that PARP inhibitor 3-aminobenzamide (3-AB) protected neurons against death after ischemia. In this study we investigated the effect of 3-AB on the localization and expression of apoptosis inducing factor (AIF) and on two proteins from Bcl-2 family: Bcl-2 and Bax in hippocampal area CA1, on the 4th day after 3 min of forebrain ischemia in gerbils. Our results indicated that after ischemia AIF is preferentially translocated from the mitochondria to the cytoplasm and to the nucleus. Intravenous administration of 3-AB (30 mg/kg b.w.) prevents AIF translocation to the nucleus. AIF was mainly seen in the structurally unchanged mitochondria and Golgi complex. Moreover, after 3-AB administration overexpression of Bcl-2 protein was observed in mitochondrial membranes, rough endoplasmatic reticulum, Golgi complex, nuclear envelopes, and also in cytoplasm and in nucleus. These data suggest that inhibition of PARP activity may have a beneficial effect on hippocampal neurons through overexpression of Bcl-2 protein and suppression of AIF translocation to the nucleus.