PEPTIDERGIC INNERVATION AND ENDOCRINE-CELLS OF INSECT MIDGUT

Antibody against FMRFamide reacts with the stomatogastric innervation and with the midgut endocrine cells in the representatives of most insect orders. The innervation was not revealed in Homoptera, Heteroptera, and Hymenoptera, and the endocrine cells were not recognized in aphids. Other insects exhibited FMRF-amide positive endocrine cells of both open and closed types. The cells are mostly single, rarely grouped, and are distributed unequally in different midgut regions; some of the cells project cytoplasmic extensions indicative of a paracrine function. Investigations on Galleria revealed that the gut innervation persists during midgut reconstruction in the course of metamorphosis. The endocrine cells are sloughed off into the new gut lumen, but there they maintain their antigenic properties until a new population of endocrine cells becomes detectable. Antisera to most mammalian gastroenteropancreatic peptides react specifically with the innervation and/or the endocrine cells of insect midgut; only antisera to bombesin, neurotensin, secretin, motilin, and insulin failed to react. All insects seem to contain antigens that can be detected with antisera to pancreatic polypeptide, FMRFamide, enkephalins, and vasopressins. Stomatogastric innervation and the endocrine cells of some lepidopterans also possess allatotropin- and diuretic hormone-like antigens; stomatogastric ganglia, in particular, a prothoracicotropic hormone-like antigen.