Tachykinins are active peptides which excite neurons, evoke behavioral responses, are potent vasodilators and secretagogues, and contract (directly or indirectly) many smooth muscles. Stimulates gut muscle contractions (PubMed:10801863). Required for the response to the male sex pheromone CH503 which is transferred from males to females during mating and inhibits courtship behavior by other males (PubMed:26083710). The Gr68a gustatory receptor is required for detection of the pheromone and Gr68a-expressing neurons in the male foreleg relay signals to the suboesophageal zone (SEZ) which leads to courtship suppression through release of tachykinin from a cluster of 8-10 neurons in the SEZ (PubMed:26083710). Strong expression is seen in a group of 14 cells plus one isolated cell in the midgut of stage 17 embryos. Also expressed in a pair of medially located unidentified cells, just posterior to the brain, and in two lateral groups of cells that may be associated with tracheae. Expression in the larval gut is restricted to cells with endocrine cell-like morphology in the posterior midgut, just anterior to the malphigian tubules. In the brain, expression is detected in a restricted number of neuronal cell bodies. Expression in the adult female gut is restricted to the midgut with no expression detected in the hindgut. Belongs to the tachykinin family.