Tachykinin

Tachykinins are a family of neuropeptides that play a significant role in the nervous system. The name "tachykinin" comes from the Greek words "tachys" meaning fast and "kinein" meaning to move, reflecting their ability to rapidly induce smooth muscle contraction. The most well-known member of this family is Substance P, which was the first tachykinin to be discovered. Other important tachykinins include Neurokinin A (also known as Substance K), Neurokinin B, and Eledoisin.

These peptides are characterized by a conserved C-terminal sequence, a key feature for their biological activity. Tachykinins are synthesized in various tissues, including the central and peripheral nervous systems, as well as non-neuronal cells like immune cells and epithelial cells. They exert their effects by binding to specific G protein-coupled receptors, primarily the neurokinin-1 (NK1) receptor for Substance P, the neurokinin-2 (NK2) receptor for Neurokinin A, and the neurokinin-3 (NK3) receptor for Neurokinin B.

The functions of tachykinins are diverse and include roles in pain transmission, inflammation, cardiovascular regulation, and gastrointestinal motility. In pain signaling, Substance P is a key mediator released from sensory neurons. They are also implicated in modulating mood and behavior, and their involvement in conditions such as asthma, irritable bowel syndrome, and certain neurological disorders is an active area of research. The therapeutic targeting of tachykinin receptors is being explored for the treatment of various diseases.