PURIFICATION OF A NEUROPEPTIDE Y-RELATED PEPTIDE FROM THE BRAIN OF THE SEA LAMPREY AND ITS EFFECT ON STEROIDOGENESIS

A peptide with neuropeptide Y-like immunoreactivity was identified by radioimmunoassay in an extract of the brain of the sea lamprey, Petrom yzon marinus using an antiserum raised against the conserved COOH-term inal region of mammalian neuropeptide Y. Purification of the peptide a nd determination of its primary structure showed that it was identical to peptide methionine-tyrosine (PMY), previously isolated from the in testine of the same species. Intraperitoneal injection of synthetic PM Y (0.15 mug/g) into female lampreys undergoing final maturation before spawning produced a significant (P < 0.05) decrease in plasma concent rations of estradiol compared with control lampreys injected with vehi cle only. These data suggest the hypothesis that the observed decrease in the concentration of PMY-containing cells in the intestines of lam preys during upstream migration may correlate with the increase in cir culating estradiol concentrations and final maturational processes.