Establishment of molecular mechanism of exercise motivation using a novel rat-strain featured by high levels of wheel-running activity

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We established a novel rat strain featured by high levels of voluntary wheel-running, which is called SPORTS(Spontaneously-Running Tokushima-Shikoku) rat. The aim of this study was to investigate the effect of high-or low-intensities in voluntary exercise on sympathetic and vagal controls of heart at sedentary and during wheel-running exercise by use of SPORTS rats. At 15 weeks of age, each rat was moved to a new cage with or without an exercise wheel, and sorted into four groups ; 1) SPORTS rat with an exercise wheel(running), 2) SPORTS rat without an exercise wheel(sedentary), 3) control rat with an exercise wheel(running), and 4) control rat without an exercise wheel(sedentary). Heart rate was significantly increased in sedentary SPORTS rats compared to those in control rats. SPORTS rats show a significant reduction in resting heart rate by high-intensity running. The low frequency/high frequency(LF/HF) ratio, which reflects cardiac sympathetic nerve activity, was significantly decreased in SPORTS rats by voluntary running. However, a decrease of sympathetic nerve activity was not observed in control rats with approximately 1/10 wheel-running activity. By wheel running, the low frequency(LF) power was augmented in control rats, and was markedly depressed in SPORTS rats. High-intensity voluntary running decreases mean heart rate during resting period(sedentary) with a depression of sympathetic nerve activity. These results suggest that high-intensity voluntary exercise attenuates sympathetic nerve activity not only during exercise but also during resting period as a lasting effects.