Ablation of adult hippocampal neurogenesis. Doublecortin immunostaining in the granule cell layer of the dentate gyrus was reduced in (A) X-ray treated mice (F1,8 = 49.21, *P < 0.01) and (B) GFAP-TK TG mice treated with ganciclovir (F1,8 = 90.30, *P < 0.01). Representative photomicrographs of doublecortin immunoreactivity in the subgranular zone of the dentate gyrus of a WT mouse (C) and a GFAP-TK TG mouse (D) are shown. Scale bars, 200 mm. Error bars represent S.E.M. X-ray-treated (N = 5); sham-irradiated (N = 5); GFAP-TK TG (N = 5); WT (N = 5). [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]