Effect of Acanthopanax senticosus on 5-hydroxytryptamine synthesis and tryptophan hydroxylase expression in the dorsal raphe of exercised rats.

Acanthopanax senticosus Harms (AS) is classified into the family of Araliaceae. The plant has been used as an analeptic aid, which improves weakened physical status and strength. Serotonin (5-hydroxytryptamine, 5-HT) is an important neurotransmitter and tryptophan hydroxylase (TPH) catalyzes the rate-f the raphe nuclei. These are associated with "central fatigue hypotheses" in the brain. In the present study, the effects of Acanthopanax senticosus on the time to exhaustion by treadmill exercise and on 5-HT synthesis and TPH expression in the dorsal raphe were investigated by immunohistochemistry. In the present results, Acanthopanax senticosus increased the time to exhaustion by treadmill running and it suppressed the exercise-induced increase of 5-HT synthesis and TPH expression. Acanthopanax senticosus was effective as caffeine for increasing the exhaustion time in treadmill running and for reducing the exercise-induced increase of 5-HT synthesis and TPH expression in the dorsal raphe. The present study shows that Acanthopanax senticosus reduces fatigue during exercise by the inhibition of exercise-induced 5-HT synthesis and TPH expression in the dorsal raphe.