Fig. 5.

Representative photomicrographs of proliferating and mature BrdU-labeled cells. A–C, Photomicrographs of labeled cells 2 hr after BrdU injection (1000×). At this time point proliferating cells are localized to the SGZ and often appear in clusters. The cell clusters in A and Bcontain multiple progenitor cells. Mitotic figures (B,C, indicated by arrow) were also evident in sections from every animal. D, E,Photomicrographs of labeled cells 4 weeks after BrdU injection (1000×). At this time point mature cells are found throughout the granule cell layer and appear ovoid or round, similar to surrounding granule cells. The characteristics of the new and mature cells from control and antidepressant-treated sections were not different. Only the number of proliferating cells was significantly increased by antidepressant treatment.