The increase in new-born neuron number by wheel running is delayed in DBA/2 mice.
Animals were housed in STD or RUN cages for 4 weeks (A, B), 2 weeks (C), 3 weeks (D) or 6 weeks (E–G). Running mice of the strain C57BL/6 exhibited an increase in new neurons at both time points measured, 4 weeks (B) and 6 weeks (F). The number of new neurons in DBA/2 mice was only transiently increased after 3 weeks of running and not at 2 weeks (C), 4 weeks (A) or 6 weeks (E) following a single labeling injection. DBA/2 animals labeled with a series of injections over 10 days showed an increased number of new-born neurons after 6 weeks of wheel running (G). Representative fluorescence microscopy image of a new-born neuron stained using antibodies against CldU (H; green) and NeuN (I; magenta) with the arrow indicating a double-positive cell (J; merged image). Bar graphs show mean ± SEM. All p-values are from two-tailed Student’s t-tests. Scale bars in H–J are 20 µm.