Submitted to: Peptides
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 8, 1998
Publication Date: N/A
Interpretive Summary: Over the past decade there has been much emphasis on the study of a class of insect hormones called neuropeptides. Neuropeptides regulate virtually all aspects of insect physiology and are therefore attractive targets for development of novel methods of insect pest control. However, neuropeptides do not penetrate the surface of the insect when applied topically. Therefore, development of new strategies for pest control based on these neuropeptides requires the development of a delivery system that allows these hormones to enter the body after being applied to the surface of the insect. Scientists at the Center for Medical, Agricultural and Veterinary Entomology, USDA, ARS, Gainesville, Florida and Food Animal Protection Research Laboratory, College Station, Texas have successfully synthesized and modified insect neuropeptides that penetrate the insect cuticle and stimulate sex pheromone production. Their work has shown peptide analogs can be designed to penetrate the cuticle at different rates by changing the structures of the neuropeptides. The results provide important information for development of new strategies for pest control based on the use of insect neuropeptides because neuropeptide analogs can be designed to penetrate the cuticle of specific pest insects a specific rates and thus have prolonged effects in the target insect.
Technical Abstract: Rates of penetration through the cuticle of amphiphylic pseudopeptides, synthesized by addition of 6-phenylhexanoic acid or 9-fluoreneacetic acid or 1-pyrenebutyric acid to the amino terminus of the pentapeptide Phe-Thr-Pro-Arg-Leu-amide, were assessed by quantitative analysis using reversed phase liquid chromatography. The pseudopeptides effectively penetrated the cuticle of both the adult American cockroach and tobacco budworm moth. However, the amounts of pseudopeptides that penetrated the cuticle of the cockroach were significantly lower and the rates of penetration were slower than for moth cuticle. Penetration of the pseudopeptides through the cuticle was dependent upon the size of the lipidic attachment to the pentapeptide. The 6-phenylhexanoic acid analog penetrated most rapidly followed by the 9-fluoreneacetic acid analog and the 1-pyrenebutyric acid analog penetrated slowest. All of the pseudopeptides exhibited an initial rapid period of penetration lasting 2-3 h followed by the establishment of a steady slow release state which lasted between 9-24 h and was dependent upon both the size of the pseudopeptide and species to which the analog was applied. The results confirmed the hypothesis that the insect cuticle could be employed as a slow release device for delivery of pseudopeptide analogs of insect neuropeptides.