Immunochemical evidence for a gastrin-like peptide in insect neuroendocrine system

Manduca sexta (L.), contains a peptide that is gastrin-like in its antigenicity, size, and susceptibility to degradative enzymes is presented. No immunoreactive gastrin was found in gut extracts from four species of insects. These results suggest the existence of a peptide in insect nervous tissue having structural similarities to vertebrate gastrin. There is much interest in the origin and evolution of polypeptides in vertebrates that may be common to both nerve cells of the brain and gastrointestinal endocrinelike cells (Pearse, 1976). These peptides include gastrin (Vanderhaegen et al., 1975), somatostatin (Brazeau et al., 1973; Arimura et al., 1975), vasoactive intestinal peptide (Said and Rosenburg, 1976), and substance P (Hokfelt et al., 1975; Pearse and Polak, 1975). For a more precise picture of the molecular evolution of these materials, a search for their presence in the invertebrate phyla is essential. Straus ef al. (1975) have recently demonstrated the presence of gastrin-like immunoreactive peptides in the blood and gastrointestinal tissues from two molluscan species. We have conducted a survey for immunoreactive gastrin in insect tissues and report here the identification of a gastrin-like polypeptide in the neuroendocrine system (brain, corpus cardiacum, and corpus allatum) of the tobacco hornworm,