BDNF Haploinsufficiency Limits Voluntary Exercise-Induced Adult Hippocampal Neurogenesis

Adult hippocampal neurogenesis is involved in hippocampal plasticity and can be enhanced by voluntary physical activity, which also elevates "brain-derived neurotrophic factor" (BDNF) levels and improves memory performance. BDNF might either be essential for the maintenance of neurogenesis, or be necessary for mediating activity-dependent increases in neurogenesis. In order to get more insight on this, we examined male heterozygous BDNF-deficient (BDNF +/-) mice with or without access to a running wheel. Only males were analyzed, since sex steroids can interact with BDNF signaling pathways. Although male BDNF +/- mice exhibited a higher body weight as compared to age-matched controls (BDNF +/+), they did not differ in distance traveled, running time or running speed. We then analyzed whether changes in adult hippocampal neurogenesis can be observed. Under housing conditions without running wheels, the rates of basal adult hippocampal neurogenesis were not altered between genotypes. Interestingly, voluntary wheel running significantly increased neurogenesis in both groups; however, the magnitude was attenuated in BDNF +/- mice. These results indicate that, in adult male mice, reduced BDNF availability does not impair basal adult hippocampal neurogenesis, but limits the plasticity-related enhancement of neurogenesis induced by physical activity.