We focused on β-endorphin, vasoactive intestinal peptide (VIP), neurotensin, enkephalins, substance P and bradykinin because these peptides are linked to pain sensitization or inflammation and, as such, are relevant in the pathophysiology of colitis [17,18,19,20,21,22,23,24,25,26,27,28,29,30]. Here, VIP is linked to colitis.