Abstract
Hippocampal neurogenesis persists throughout adult life and plays an important role in learning and memory. Although the influence of physical exercise on neurogenesis has been intensively studied, there is controversy in regard to how the impact of exercise may vary with its regime. Less is known about how distinct exercise paradigms may differentially affect the learning behavior. Here we found that, chronic moderate treadmill running led to an increase of cell proliferation, survival, neuronal differentiation, and migration. In contrast, intense running only promoted neuronal differentiation and migration, which was accompanied with lower expressions of vascular endothelial growth factor, brain-derived neurotrophic factor, insulin-like growth factor 1, and erythropoietin. In addition, the intensely but not mildly exercised animals exhibited a lower mitochondrial activity in the dentate gyrus. Correspondingly, neurogenesis induced by moderate but not intense exercise was sufficient to improve the animal’s ability in spatial pattern separation. Our data indicate that the effect of exercise on spatial learning is intensity-dependent and may involve mechanisms other than a simple increase in the number of new neurons.
Highlights
New neurons are continuously produced in the dentate gyrus (DG) of adult animals (Altman and Das, 1965; Kaplan and Hinds, 1977; Zhao et al, 2008)
It has been reported that low- to moderate- but not high-intensity intensity exercise can enhance adult hippocampal neurogenesis; exercise of high-intensity is usually associated with significant more production of stress hormones in those studies (Inoue et al, 2015)
To exclude the interference from stress, we replaced the commonly used electric shock with a gentle tail tapping in forced treadmill running, which led to similar levels of serum cortisol in fatiguing exercise (FE) and moderate exercise (ME) mice, and allowed us to compare the effects of moderate- and high-intensity training alone
Summary
New neurons are continuously produced in the dentate gyrus (DG) of adult animals (Altman and Das, 1965; Kaplan and Hinds, 1977; Zhao et al, 2008). The exact function of adult neurogenesis remains an open question, accumulating evidence suggests that nascent dentate granule cells (DGCs) play an important role in memory formation, consolidation and retrieval (Kempermann et al, 1997; Shors et al, 2001; Kitamura et al, 2009; Gu et al, 2012). It is necessary to elucidate factors that modulate adult hippocampal neurogenesis. The adult-born DGCs originate from neural stem cells (NSCs) located in the subgranular zone. A large body of literature has reported benefits of physical exercise on neurogenesis in the adult DG
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