Substance P

Neuropeptide inducing Ca²⁺ mobilization. Activates G₁-Proteins directly. Induces superoxide production in neutrophils.

Substance P (SP) was first discovered in 1931 by von Euler and Gaddum and is the best characterized member of the neurokinins. This class of peptide neurotransmitters includes neurokinin A (NK-A) and B (NK-B), and are characterized by the common C-terminal sequence Phe-X-Gly-Leu-Met-NH₂. The receptors for SP, NK-A and NK-B, designated NK₁, NK₂ and NK₃ respectively, are members of the G protein-coupled receptor superfamily. All three receptors have been shown to stimulate inositol phospholipid hydrolysis. SP is involved in pain, smooth muscle contraction, secretion from exocrine and endocrine glands, inflammatory response including vasodilation, plasma extravasation and mobilization of immune system cells.