Analysis of the anti-fatigue activity of polysaccharide from Spirulina platensis: Role of central 5-hydroxytryptamine mechanisms.
This study is to evaluate the effects of polysaccharide from Spirulina platensis (PSP) on treadmill exercise endurance, the levels of some biochemical indicators as hemoglobin (Hb), Lactic acid (LA), creatine kinase (CK) and urea nitrogen (BUN) in the blood, 5-hydroxytryptamine (5-HT) concentrations, the second isoforms of tryptophan hydroxylase (TPH2) and serotonergic type 1B inhibitory autoreceptors (5-HT1B) expression in the caudate putamen of exercised rats. Sixty Sprague-Dawley male rats were randomly divided into six groups: control group, exercise group, exercise and PSP (50, 100,200 mg/kg)–treated groups, exercise and caffeine (10 mg/ kg)–treated group (positive control). In exercise groups, rats were put on treadmill and forced to run for 30 min 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. The levels of Hb and LA were tested by the HiCN (Hemoglobin ferricyanide) colorimetry method and colorimetric assay method, respectively. The levels of CK and BUN were determined by automatic biochemical analyser. 5-HT concentrations were detected by HPLC analysis. TPH2 and 5-HT1B expression were measured by western blot analysis and real-time PCR. The results demonstrated that PSP could prolong the time to exhaustion in treadmill exercise, increase Hb levels and decrease LA, BUN and CK levels in the blood and suppress the exercise-induced increase of 5-HT concentrations and TPH2 expression and prevent the exercise-induced decrease of 5-HT1B expression in the caudate putamen. The most potent effects were observed at the dose of 200 mg/kg of PSP. It suggests that the mechanism of PSP’s promoting physical performance might be related to increasing Hb levels and decreasing LA, BUN and CK levels in the blood and the inhibition of the exercise-induced synthesis of 5-HT and TPH2 expression, and the increase of the 5-HT1B expression in the caudate putamen of exercised rats.