EFFECTS OF LAMPREY GONADOTROPIN-RELEASING HORMONE-III ON STEROIDOGENESIS AND SPERMIATION IN MALE SEA LAMPREYS

The biological activities of lamprey gonadotropin-releasing hormone-III (GnRH-III) were determined in the adult male sea lamprey, Petromyzon marinus. One injection of lamprey GnRH-III at 0.1 or 0.2 mu g/g body wt stimulated plasma estradiol and progesterone levels in adult male sea lampreys undergoing final maturation. Four successive injections of lamprey GnRH-III at 0.1 mu g/g or lamprey GnRH-I at 0.2 mu g/g induced spermiation in 78 or 30% of the lampreys, respectively, compared to 0% in controls by Day 16. In summary, lamprey GnRH-III is biologically active in stimulating the pituitary-gonadal axis in adult male lampreys. (C) 1994 Academic Press, Inc.