A novel visceral excitatory neuropeptide from the brain tissue of cloudy dogfish (Scyliorhinus torazame)

A visceral excitatory neuropeptide with a molecular weight of 1563 Da was isolated from the brain extracts of cloudy dogfish (Scyliorhinus torazame) discarded as a fishery by-product. Fish hindgut was employed to carry out physiological assay for its visceral excitation. During consecutive purification using C18 cartridge and high-performance liquid chromatography (HPLC), a neuropeptide (DF-2) was isolated from neuronal cell extracts of dogfish brain tissue and clearly exhibited potential to exert visceral excitatory effect on hindgut of dogfish. The primary structure of DF-2 established by ESI-Q-TOF tandem mass was LESLVYEQLWPWamide. The results of database search provided evidence for this peptide sequence to be novel. In visceral excitatory assay using myography, the threshold concentration of DF-2 required for the changes in spontaneous contraction of cloudy dogfish hindgut was found to be 10−6 M. Therefore, this study suggests that DF-2 isolated from brain of elasmobranches could be one of the sequences, which regulates spontaneous visceral contractions in dogfish digestive duct.