TAC1 and digestive system disorder: The enteric tachykininergic system has a fundamental role in the maintenance of the intestinal neuromuscular function, and alterations in substance P-mediated neurotransmission, i.e., higher content and release from enteric neurons as well as immune cells of intestinal lamina propria, may participate to the pathogenesis of some gastrointestinal disorders of high clinical impact, such as chronic inflammatory diseases [52,53,54].