Topographic analysis of cell proliferation in the hippocampus of the adult mouse.

The dentate gyrus of the hippocampus generates new neurons throughout life. The distribution of neural progenitor cells in the hippocampus along the anteroposterior axis is, however, not known. To determine whether mitotic activity differs along the anteroposterior axis, we examined mitotic activity in serial hippocampal sections of two experimental groups: normal bred (control) and exercised groups. In both groups, the number of 5-bromo-2'-deoxyuridine-positive cells was markedly decreased in the caudal dentate gyrus; exercised groups also had mitotic activity of about 1.5 times that of control groups. Mitotic activity tended to increase in the suprapyramidal blade of the middle dentate gyrus of exercised groups. These results indicate that the adult hippocampus has regional differences in mitotic activity.