Changes in the number of EC cells and the levels of 5-HT in the serum samples from IBD patients have previously been documented.85,86 Colonic biopsy specimens from IBD patients also demonstrate an upregulation of 5-HTR3 and, more recently 5-HTR7 expression with associated increases in intestinal inflammation.87,88 Whilst this demonstrates a role for serotonin signaling in IBD pathogenesis, it remains to be seen if this also correlates with the development of chronic pain in these patients. The gene discussed is HTR5A; the disease is inflammatory bowel disease.