Role of food-derived opioid peptides in regulation of thermosensitivity of Periplaneta americana cockroach

Abstract

The ability of exorphines (relative δ-selective opioid fragments of food-derived peptides) to change the defense response of American cockroaches Periplaneta americana placed in a hot chamber (T= 50°C) was studied. It was found that the ED50 for a fragment of D-ribulose-1,5-bisphosphate carboxylase rubiscolin-5 (YPLDL) doubling the stay time for the insects in the hot chamber was 340 nM/g. The ED50 for wheat gluten exorphine C (YPISL) was 573 nM/g. Cytochropin-4, a fragment of cytochrome B, did not have a significant effect. Comparison of the obtained data with the results of previous experiments with μ-selective exorphines—milk β-casein fragments—led to the conclusion that opioid receptors of various types are equally involved in regulation of cockroach protective behavior. The significance of phytogenous exorphines in formation of the opioid system of insects in the course of evolution is discussed.