Tachykinins biological actions

Substance P and Substance K are also known as tachykinins. They are a family of closely related peptides responsible for important biological actions including bronchoconstriction, salivation, vasodilatation. 

Mammalian tachykinins, a family of tachykinin peptides traditionally classified as neurotransmitters that include substance P (SP), neurokinins (NKA and NKB), two elongated versions of NKA, neuropeptide y (NP,) and neuropeptide K (NPK), hemokinin 1 (HK-1) and endokinins A-D. They act as neurotransmitters, paracrine or endocrine factors, neuroimmunomodulators, and have also immune and pro-inflammatory actions. Furthermore, mammalian tachykinins are involved in vasodilation, plasma extravasation, smooth muscle contraction, secretion, neural excitation, and processing of sensory information. The biological actions are mediated via three known mammalian tachykinin receptors, NKi, NK2, and NK3 [N. M. Page et al, Proc. Natl. Acad. Sci. USA 2003, 100, 6245 N. M. Page, Peptides 2005, 26, 1356 L. Liu, E. Burcher, Peptides 2005, 26, 1369]. 

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