Objective · To investigate the preventive effects of curcumin on inflammation and expression of tryptophan hydroxylase (TPH) in a rat model of ulcerative colitis(UC). Methods · UC was induced by 5% dextran sulfate sodium (DSS) in drinking water provided to SD rats for continuous 7 d .The oral administrations of curcumin (60 mg/kg, once a day for 10 d) were started at Day 1 since the establishment of UC model as preventive treatment. The anti-inflammatory effects of curcumin were assessed by disease activities index (DAI) score and colonic histological score(H-E staining). The effect of curcumin on expression of TPH was examined by Western blotting. Results · DSS-induced histological change in colon defined as UC increased in DAI score and increased in protein level of TPH in colon (P=0.000). Compared with the control group, preventive treatment with curcumin significantly inhibited histological score (P=0.034)and DAI score (P=0.045), while curcumin did not alter the DSS-induced upregulation of TPH. Conclusion · Preventive treatment with curcumin suppresses the inflammatory responses, while curcumin does not alter the DSS-induced upregulation of TPH. These findings indicate that anti-inflammatory effect of curcumin is independent of inhibition of 5-HT synthesis.