Description_x000D_ Amino Acid Sequence_x000D_ Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Sar-Leu-Met-NH2_x000D_ Application_x000D_ Substance P is a tachykinin family 11 amino acid neuropeptide involved in neurotransmission and neuromodulation. Substance P acts via the neurokinin-1 receptor (NK1-receptor, NK1R). [Sar9]-Substance P and [Sar9] substance P-sulphone (NK1-receptor agonist) are used to study and differentiate NK1-receptors activities from NK2R and NK3R activities.