2012 年 1 巻 4 号 p. 585-594
The hippocampus is important for learning and memory. It is also one of the few regions in the adult mammalian brain that can generate new neurons (adult hippocampus neurogenesis, AHN). It is suggested that altered hippocampal neurogenesis, by stress or aging, is related to pathophysiology of mood disorders, such as depression. On the other hand, AHN is robustly stimulated by voluntary and treadmill running, and accumulating knowledge indicates that the beneficial effects of exercise on cognition and mental health may be mediated, at least in part, by exercised-induced AHN. Thus, it is important to elucidate the mechanisms underlying exercise-induced AHN. However, the mechanisms and exercise conditions (intensity and frequency etc.) that activate AHN are still undetermined. Since high-intensity exercise elicits a stress response, mild exercise without a stress response may be a useful model for increasing AHN. To address this hypothesis, we used treadmill running, which can be controlled for speed, and developed a mild-intensity treadmill exercise model below the lactate threshold (LT, about 20 m/min) and minimal stress response; the LT is a physiologic index of moderate exercise intensity established in rats, as in humans. Recently, we have demonstrated that mild-intensity exercise enhances hippocampal neuronal activity, neurotrophic factors and neurogenesis. Therefore, a mild exercise model is shown that enhances cognitive functions, and further information, through mechanistic studies with the model, will be of benefit for developing effective exercise programs enhancing cognitive functions in humans, especially in vulnerable people with poor physical fitness.