Alterations in normal serotonin (5-hydroxytryptamine;5-HT) signaling have been reported in ulcerative colitis (UC) and Crohn's disease (CD). Studies report an increase in enterochromaffin (EC) cell, main source of 5-HT in the gut, numbers in CD and UC patients. Up-regulated expression of mucosal Tryptophan hydroxylase (TPH)-1, catalytic enzyme in 5-HT production, messenger RNA (mRNA) have been found in CD patients in remission who are suffering the irritable bowel syndrome (IBS)-like symptoms. Alterations in normal 5-HT signaling has also been reported in animal models of inflammatory bowel disease (IBD). Thus, the aim of the proposed research project will be to study the alterations in 5-HT signalling accompanying GI inflammatory conditions, such as IBD.