Vertebrate-Type Neuropeptides and Steroids in Locusta migratoria: Identification and Metabolism

Abstract

The search for “vertebrate-type” steroid hormones in insects was initiated in our lab after Huybrechts and De Loof (1977, 1982) succeeded in inducing vitellogenin synthesis in male flies (Sarcophaga bullata, Calliphora erythrocephala, Musca domestica, Phormia regina) by injecting or feeding 20-hydroxyecdysone. Flies apparently use this steroid as the equivalent of estrogens in vertebrates, which use this steroid for control of vitellogenin synthesis by the liver. When the search for a male-specific ecdysteroid did not yield any positive result, the question was raised whether insects might perhaps have some typical “vertebrate-type” steroids. There is now hard evidence that at least 10 different such steroids are indeed present in insects. Not clear at all is whether these steroids derive either from food or from biosynthesis. In a parallel line of research, the possible presence of molecules resembling the peptide hormones that control steroid biosynthesis in vertebrates (e.g. LH, FSH, ACTH) was investigated. Immunocytochemical data suggest that they are indeed present. None of these has as yet been isolated, however, but as an indirect result, a lot of other neuropeptides have been fully characterized.