Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/30/2000
Publication Date: N/A
Interpretive Summary: Because of problems with the development of resistance to conventional pesticides, there is a critical need for new concepts and alternative approaches in controlling such pests. The basic premise of this research is that peptides (short chains of amino acids) serve as potent internal messengers in insects to regulate vital functions. Peptides themselves are unsuitable for control measures due to their instability to enzymes in the circulatory and digestive systems, and an inability to penetrate the outer surface of the insect. New, selective control measures may be developed by designing metabolically stable mimics of these neuropeptides that actively inhibit or over-stimulate functions regulated by them, resulting in disruption of the internal environment of the insect. In this paper, we investigate the effect of natural neuropeptides of the pyrokinin family on stimulation of contractions of muscles important to the digestive and reproductive processes of the cockroach. A more thorough understanding of the complete spectrum of biological activity and the functions of this neuropeptide family will enhance our ability to use them to disrupt critical digestive and reproductive life processes in cockroaches and related insects. This work leads us one step closer to the development of practical neuropeptide-like agents that will be effective in controlling certain pests (such as cockroaches) in an environmentally friendly fashion.
Technical Abstract: Six pyrokinins, members of a widely distributed neuropeptide family in insects (FXPRLamides), have been identified from the American cockroach (Predel and Eckert, 2000). Five of these peptides, Pea-PK- 1-5, were tested in different myotropic bioassays, including hyperneural muscle, hindgut, foregut, and oviduct. Among these muscles, the hyperneural muscle exhibited the highest sensitivity to pyrokinin applications. The efficacy of the different pyrokinins differed dramatically. No muscle specific effectiveness was obtained, the ranking order in all muscle assays was as follows: PK- 1 > PK-4 > PK-3 > PK-2 > PK-5. Testing of synthetic analogs revealed the importance of the amino acid at the variable 4 position of the C- terminus. Pyrokinin-5, the only one of the five tested peptides that is stored in abdominal perisympathetic organs, has probably no myotropic function at all. This is further evidence, that these neurohaemal release sites are not necessary to compensate the open circulatory system of insects but have further specific functions which are totally unknown as yet.