F2R and irritable bowel syndrome: The studies on human specimens show the presence of PAR-1 and PAR-2 in mast cells from various normal human tissues [27]; expression of PAR-2 and PAR-4 in mast cells both at protein and mRNA levels in the patients with postinfectious irritable bowel syndrome (PI-IBS) [28]; upregulated expression of PAR-2 in mast cells from ulcerative colitis tissues [25]; and the increased fraction of PAR-2-expressing mucosal mast cells in Crohn's specimens [23] (Table 1).