CCK and irritable bowel syndrome: For example, a subset expressed cholecystokinin (Cck) and vasoactive intestinal polypeptide (Vip), markers of intestinofugal neurons, or brain-derived neurotrophic factor (Bdnf), which is increased in patients affected by irritable bowel syndrome, or Piezo2, a mechanosensitive ion channel involved in the regulation of smooth muscle tone.