A novel active pentapeptide from chicken brain identified by antibodies to FMRFamide

The tetrapeptide Phe-Met-Arg-Phe-NH 2 (FMRFamide) and peptides structurally related to it, have been isolated from molluscan ganglia 1–3 . They have widespread actions on both invertebrate and vertebrate tissues and there is increasing evidence that they are an important group of invertebrate peptide neurotransmitters 3–8 . It is of interest that the primary amino acid sequence of FMRFamide forms the C-terminal tetrapeptide of an enkephalin-like heptapeptide (Met-enkephalin-Arg 6 Phe 7 ) isolated from bovine adrenal medulla and striatum 9,10 . Antisera to FMRFamide have been shown to react in radioimmunoassay and immunohistochemistry with material in the central nervous system of various vertebrate species 11–17 , but the identity of this material, and in particular its relationship to the opioid heptapeptide, remains uncertain. We have used antibodies specific for the C-terminus of FMRFamide in radioimmunoassays to monitor purification of the material in chicken brain. We describe here the sequence of one of the peptides obtained. It is a biologically active peptide which does not seem to be related to other known vertebrate neuropeptides.