Physical exercise prevents age-related decline in precursor cell activity in the mouse dentate gyrus

Physical activity induces adult hippocampal neurogenesis. We here show that the acute up-regulating effect of voluntary wheel running on precursor cell proliferation decreases with continued exercise, but that continued exercise reduces the age-dependent decline in adult neurogenesis. Cell proliferation peaked at 3 days of running. After 32 days of exercise this response returned to baseline. Running-induced proliferation of transiently amplifying progenitor cells led to a consecutive increase in the number of more mature cells. Increasing age reduced adult neurogenesis at 9 months to 50% of the value at 6 weeks and to 17% at the age of 2 years. At both 1 and 2 years, precursor cell divisions remained inducible by physical activity. Exercise from 3 to 9 months of age significantly reduced the age-dependent decline in cell proliferation but (presumably in the absence of additional stimuli) did not maintain net neurogenesis at levels corresponding to a younger age. We propose that physical activity might contribute to successful aging by increasing the potential for neurogenesis represented by the pool of proliferating precursor cells. (c) 2005 Elsevier Inc. All rights reserved.