Amphibian skin contains a wide variety of peptides that are often homologous or even identical to the gastrointestinal hormones and neurotransmitters of the Mammalia.
Striking examples are cerulein, the amphibian counterpart of mammalian cholecystokinin and gastrin; physalemin and kassinin, counterparts of the mammalian neuropeptides substance P and neurokinins; the amphibian bombesins and litorins, which heralded the discovery of the gastrin-releasing peptides (mammalian bombesin) and neuromedin B; finally sauvagine, whose structure elucidation preceded that of the analogous, hypothalamic corticotropin releasing hormone. Other peptide families common to amphibian skin and mammalian tissues are bradykinins, angiotensins, somatostatins and the thyrotropin-releasing hormone. Opioid peptides have so far only been in the skin of the hylid frog of the Phyllomedusine stock. During his long scientific life, the pharmacologist Vittorio Erspamer sought biologically active molecules...