This study addresses whether hippocampal progenitor cells express nestin following cerebral ischemia in rats. Cell counts within the hippocampal hilus were significantly greater following severe (eight-vessel occlusion) ischemia than following intermediate (four-vessel occlusion) ischemia (1527+/-87/mm2 vs. 918+/-71/mm2). Bromedeoxyuridine-positive cell counts were significantly higher with severe ischemia than with intermediate ischemia or in sham-operated animals, respectively (368+/-45, 43+/-14 and 7+/-1/mm2). In the eight-vessel occlusion group, 47+/-8/mm2 bromedeoxyuridine-labeled cells expressed nestin, significantly higher than in the four-vessel occlusion group and sham-operated animals (1+/-1 and 1+/-0/mm2, P<0.01 vs. eight-vessel occlusion, respectively). Confocal microscopy verified that a subset of the bromedeoxyuridine-positive cells expressed nestin. In conclusion, severe ischemia elicits nestin expression in hippocampal progenitor cells in rats.