Selective agonists of tachykinin binding sites

Three types of binding sites for the mammalian tachykinins, ie Substance P (SP) Neurokinin A (NKA) and Neurokinin B (NKB), have been found in both the central and peripheral nervous systems. Substance P binds to the NK-1 subclass of binding site while NKA and NKB are less selective endogenous ligands, which preferentially interact with the NK-2 and NK-3 subclasses of binding sites, respectively. Complementary strategies, including 3-dimensional structure analysis by NMR spectroscopy and structure-activity relationship led to the design of selective agonists of these binding sites. [Pro9] SP, [Pro10] SP and the cyclic analogues [Cys3,6, Tyr8, Pro9] SP and [Cys3,6, Tyr8, Pro10] SP are selective NK-1 agonists. [Lys5] NKA(4-10) is a water soluble NK-2 potent agonist. Finally, [Pro7] NKB, which completely discriminates NK-2 and NK-3 binding sites, is a water-soluble NK-3 selective agonist.