TAC1 (tachykinin precursor 1) encodes a neuropeptide precursor that generates substance P and neurokinin A, serving as ligands for tachykinin receptors 1. TAC1 activates G protein-coupled receptor signaling through both Gq-phospholipase C and adenylate cyclase-cAMP pathways 1. In sensory neurons, TAC1+ nociceptors mediate pain perception and allergic responses; house dust mites activate TAC1+ TRPV1+ peptidergic nociceptors, which release substance P to trigger mast cell degranulation via MRGPRB2 activation, initiating type 2 skin inflammation 2. TAC1-expressing spinal neurons specifically drive coping behaviors associated with sustained pain without affecting reflexive defensive responses 3. TAC1+ neurons can be generated from human pluripotent stem cells for pain research and developing non-addictive analgesics 4. Beyond nociception, TAC1+ neurons in the nucleus of the solitary tract coordinate cough-like defensive respiratory behaviors through vagal sensory inputs 5. In the hypothalamic paraventricular nucleus, TAC1 marks neuroendocrine neuronal subtypes involved in homeostatic regulation 6. Sex hormone-responsive TAC1+ neurons in the brain regulate sex-typical social behaviors including mating 7. These diverse functions establish TAC1 as a critical mediator of sensory, neuroendocrine, and behavioral processes.