Tachykinin receptors and the potential of tachykinin antagonists as clinically effective analgesics and anti-inflammatory agents

Tachykinins (also known as neurokinins) share a common C-terminal sequence, Phe-X-Gly-Leu-Met-NH 2 (where X is Phe, Tyr, Val or Ile). Substance P was the first to be discovered and is the best characterised. Other tachykinins notable for their widespread distribution in mammalian tissues, including the peripheral and central nervous system, are neurokinins A and B. The biological actions of tachykinins are through G-protein linked receptors designated NK 1 , NK 2 and NK 3 and there has been an assumption that the preferred agonists were substance P, neurokinin A and neurokinin B respectively [1], [2]. However, the receptor selectivity of these peptides is relatively poor. There is a mismatch between tachykinin-containing neurones and fibres and their corresponding receptor in certain brain regions and this is particularly apparent in the case of neurokinin A since NK 2 receptor expression appears to be extremely low in the adult mammalian nervous system [3]. A novel NK 4 receptor has been proposed and it appears that there are two NK 3 receptors designated A and B [4]. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.