|DE LOOF, ARNOLD|
Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2000
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 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. One of the important pieces of information required to develop neuropeptide-based pest control strategies is to determine the effects of the natural neuropeptides on critical bodily functions and/or behavior. In this paper, we describe for the first time that neuropeptides of the sulfakinin class inhibit food intake in an immature form of an insect by 50-60% at low concentrations. It was further determined that this anti-feedant effect is dependent on the presence of a unique structural feature present in this neuropeptide class. These results open the possibility that this effect can be enhanced through the design and preparation of mimics that resist inactivation by internal forces that degrade the natural neuropeptides, a subject of future research. This work leads us one step closer to the development of practical neuropeptide-like chemicals that will be effective in controlling certain pest insects in an environmentally friendly fashion.
Technical Abstract: In vertebrates, the peptides cholecystokinin (CCK), neuropeptide Y, galanin, and bombesin are known to be involved in the control of food intake. We report here that insect sulfakinins, peptides which display substantial sequence similarities with the vertebrate gastrin/CCK peptide family, significantly inhibit food uptake in fifth instar nymphs of the locust, Schistocerca gregaria. Upon injection of Lom-sulfakinin, a neuropeptide present in the corpus cardiacum of locusts, food intake was significantly reduced in a dose-dependent manner within a fixed 20 mm time period. The induced effect ranged from 13% inhibition (10 pmol of injected peptide) to over 50% inhibition at 1 nmol. Other naturally occurring sulfakinins from different insect species also elicited this satiety effect. Analogous to the satiety effect of CCK in vertebrates, the sulfate group is required for activity. No effect on the palptip resistance was found after injection with sulfakinin. Therefore it seems unlikly that sulfakinins reduce food intake by decreasing the sensitivity of the taste receptors.