Substance P corresponds to amino acid 58-68 of neurokinin A precursor. Neurokinin A belongs to the tachykinin family, peptides that are potent vasodilators and secretagogues, excite neurons, provoke behaviorial responses, and contract smooth muscles. Substance P acts as a neurotransmitter found in brain ans spinal cord and is associated with inflammatory responses in the joints by causing pain.Human: H-Arg-Pro-Lys-Pro-Gln-Gln-Phe-OH or H-RPKPQQF-OH