In a previous study, we have discovered another pain mediator, brain-derived neurotrophic factor (BDNF), which has been well-recognized as an essential modulator in central physiologic and pathologic pain5, is substantially increased in colonic epithelium and lamina propria in patients with IBS, especially in diarrhoea-predominant IBS (IBS-D) subgroup. This evidence concerns the gene BDNF and irritable bowel syndrome.