Isolation of three novel neuropeptides, the Cyanea-RFamides I-III, from Scyphomedusae.

Cnidarians are the lowest animal group having a nervous system. Using a radioimmunoassay for the C-terminal sequence Arg-Phe-NH2 (RFamide), we have isolated three novel neuropeptides from the jellyfish Cyanea lamarckii (belonging to the class Scyphozoa): (Glu-Trp-Leu-Arg-Gly-Arg-Phe-NH2 (Cyanea-RFamide I), (Glu-Pro-Leu-Trp-Ser-Gly-Arg-Phe-NH2 (Cyanea-RFamide II) and Gly-Arg-Phe-NH2 (Cyanea-RFamide III). The Cyanea-RFamides are neuropeptides and form a peptide family with other known neuropeptides isolated from Hydra and hydromedusae (belonging to the class Hydrozoa), and various sea anemones and sea pansies (belonging to the class Anthozoa). The presence of RFamide neuropeptides in all major cnidarian classes suggests that this type of substance was among the first neurotransmitters used in evolution.