Central anti-fatigue activity of verbascoside

In this study, the effects of verbascoside on treadmill exercise endurance, 5-hydroxytryptamine (5-HT) concentrations, the second isoforms of tryptophan hydroxylase (TPH2) and serotonergic type 1B inhibitory autoreceptors (5-HT1B) protein expression in the caudate putamen of exercised rats were investigated. Sixty Sprague-Dawley male rats were randomly divided into six groups: normal group, exercise group, exercise and verbascoside (0.1mg/kg)-treated group, exercise and verbascoside (1mg/kg)-treated group, exercise and verbascoside (10mg/kg)-treated group, exercise and caffeine (10mg/kg)-treated group. In exercise groups, rats were put on treadmill and forced to run for 30min once a day for 6 consecutive days. On the 7th day of the experiment, the time to exhaustion in treadmill exercise was determined for the trained groups. Immediately after the determination of the exhaustion time, all rats were sacrificed. 5-HT concentrations were detected by HPLC analysis. TPH2 and 5-HT1B protein expression were measured by western blot analysis. We found that verbascoside could prolong the time to exhaustion in treadmill exercise and suppress the exercise-induced increase of 5-HT synthesis and TPH2 protein expression, and prevent the exercise-induced decrease of 5-HT1B protein expression in the caudate putamen. Verbascoside was found as effective as caffeine in these effects. Verbascoside at 10mg/kg improved endurance of exercised rats. The mechanism of verbascoside' s anti-fatigue activity might be related to the inhibition of the exercise-induced synthesis of 5-HT and TPH2 expression, and to the increase of the 5-HT1B expression in the caudate putamen of exercised rats.