Three tachykinins in mammalian brain

Two polypeptide precursors to the neuropeptide substance P have recently been identified. One of them (β-preprotachykinin) contains amino acid sequences corresponding not only to substance P but also to substance K, a novel, related peptide. A third substance P-like peptide, neuromedin K, has recently been isolated from spinal cord. The existence in vertebrates of three members of the tachykinin family of peptides may account for pharmacological observations suggesting the presence of more than one type of substance P receptor in the nervous system.