Myotropins in invertebrates: state of the art

In vertebrates, the myotropic activity on distinct smooth muscle preparations of oxytocin, pancreatic polypeptide and several other peptidic hormones has been known for a long time. The first myotropin ever found in invertebrates, namely the pentapeptide proctolin, was isolated from a cockroach in 1975. Since 1985, the identification of myotropins from a variety of invertebrates, the focus of this symposium, started booming. Largely over 100 such peptides have already been characterized. At this moment, myotropins represent by far the largest group of signaling peptides in insects. Members of the myotropin peptide families have been associated with a variety of physiological activities such as myotropic and pheromonotropic activities, diapause induction, stimulation of cuticular melanization, diuresis, pupariation, the release of neurohormones from the corpora cardiaca, and allatostatic activities, this list not being exhaustive. In general the discovery of so many myotropins urges for a more systematic study of hormones on the cytoskeleton.