TAC1 and major depressive disorder: It is activated by the neuropeptide neurokinin A (NKA) and signals through the Gq pathway.3 Found in various tissues, including the ileum and both the central and peripheral nervous systems, it has been linked to intestinal functions, inflammation, and asthma.4 As a result, NK2R has been explored as a target for treating conditions such as irritable bowel disease (IBD), colitis, and major depressive disorder.