Less sensitive BrdU antibodies are not made more sensitive by increasing their concentration. At both the 2h (A) and 3 week (B) survival times, a 1:100 concentration of the Vector antibody labeled fewer cells in the dentate gyrus compared to the Dako antibody. In contrast, a 1:100 concentration of the Novocastra BrdU antibody amplified the number of BrdU-labeled cells at both 2h and 3 weeks. However, at 3 weeks, the number of cells labeled by Novocastra was lower than that labeled by Dako. Bars represent mean ± SEM, * P < 0.05 vs. Dako, ** P < 0.05 vs. Dako and Vector.