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Title: Insect satiety: Sulfakinin localization and the effect of drosulfakinin on protein and carbohydrate ingestion in the blow fly, Phormia regina (Diptera: Calliphoridae)

item DOWNER, K.
item Nachman, Ronald

Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/31/2006
Publication Date: 11/7/2006
Citation: Downer, K.E., Haselton, A.T., Nachman, R.J., Stoffolano, J.G. 2006. Insect satiety: Sulfakinin localization and the effect of drosulfakinin on protein and carbohydrate ingestion in the blow fly, Phormia regina (Diptera: Calliphoridae). Journal of Insect Physiology. 53:106-112.

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 insect pests. The basic premise of this research is that neuropeptides (short chains of amino acids) serve as potent messengers in insects to regulate vital functions. 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. We report on a finding that the sulfakinin neuropeptide class can inhibit feeding of carbohydrates by 44% in blow flies. A deeper understanding of how these neuropeptides regulate the critical processes of satiety and digestion in insects will aid in the design of strategies to disrupt insect populations. The above results suggest that development of metabolically stable versions of the sulfakinins could lead to agents capable of disrupting the feeding process in insect pests. The work brings us one step closer to the development of practical neuropeptide-like substances that will be effective in controlling pest insects in an environmentally friendly fashion.

Technical Abstract: Sulfakinins, which are satiety factors in invertebrates, have previously been shown to inhibit feeding in the German cockroach and desert locust. This study examines the occurrence of sulfakinin immunoreactivity and the role of sulfakinin as a feeding satiety factor in the black blow fly, Phormia regina. Specifically, this study examines the effect of sulfakinin on two of the blow fly's nutrient requirements (i.e., carbohydrates and proteins). We observed sulfakinin immunoreactive cells in the brains of both male and female flies. We found that drosulfakinin I (DrmSKI, FDDY[SO3H]GHMRFa) significantly inhibited carbohydrate feeding by 44% at the most effective dose (10 nmol) in female flies. Statistically, there was no significant effect on males; however, injections of 10 nmol DrmSKI reduced carbohydrate feeding by 34% compared to the sham. Drosulfakinin had no effect on protein feeding and no significant inhibition was detected in females or males. The results of this study lend further support to the idea that carbohydrate and protein feeding are regulated by separate control mechanisms, especially in Calliphoridae.