Salmon pancreatic polypeptide exhibits neuropeptide Y-like activities in rats

Salmon pancreatic polypeptide (sPP) is a 36 residue peptide amide isolated from salmon pancreas. It has 83% sequence identity with porcine neuropeptide Y (NPY). To confirm the sequence and obtain sufficient quantity of peptide for biological investigations, sPP was synthesized by automated t-Boc solid phase synthesis. The purified product had the expected amino acid composition, primary structure and mass, and was chemically and biologically indistinguishable from natural sPP. Investigation of its biological properties revealed that, like NPY, sPP increased blood pressure and decreased heart rate in anesthetized rats in a dose-dependent manner. There was no significant difference in the responses of NPY and sPP. Furthermore, administration of sPP directly into the hypothalamus of rats induced a feeding response comparable to that induced by NPY. Based on these investigations it may be suggested that synthetic and natural sPP are identical, and that sPP can express NPY-like activities in mammals presumably by interacting with the receptors of NPY.