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United States Department of Agriculture

Agricultural Research Service

Title: Immunocytochemical Localisation and Biological Activity of Diuretic Peptides in the Housefly, Musca Domestica

Authors
item Iaboni, Andrea - UNIVERSITY OF TORONTO
item Holman, G - RETIRED ARS
item Nachman, Ronald
item Orchard, Ian - UNIVERSITY OF TORONTO
item Coast, Geoffrey - UNIVERSITY OF LONDON

Submitted to: Cell and Tissue Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 4, 1998
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 internal messengers in insects to regulate vital functions. Peptides themselves are unsuitable efor control measures due to their instability to enzymes in the circulator and digestive systems of the insect. New, selective control measures may be developed by designing mimics of these neuropeptides that actively inhibit or 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 the determination of their distribution in the nervous system, which provides clues to the precise functions they perform. We have determined the distribution of the insect kinin class of neuropeptides in the nervous and hormonal systems of the housefly. The insect kinins are regulators of important processes in insects that maintain water balance and normal digestion. 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: The distribution of a CRF-related diuretic peptide (Musca-DP) and the diuretic/myotropic insect myokinins in the central nervous system of larval and adult houseflies was investigated using antisera raised against Locusta-DH and leucokinin-I, respectively. Two separate, small populations of immunoreactive neurons are present in the brain and fused thoracic-abdominal ganglion mass. There is no evidence for these immunoreactivities being colocalised either within single neurons or at neurohaemal release sites. Crude extracts of tissues containing immunoreactive material increase fluid secretion by isolated Malpighian tubules from adult flies. Diuretic activity is highest in tissues containing myokinin-immunoreactive material. Consistent with this observation, myokinin analogues produce a four to five-fold increase in fluid secretion, which is more than twice the response to Musca-DP. These effects are mimicked by treatments that increase intracellular calcium and cyclic AMP, respectively. When tested at threshold concentrations, the two classes of diuretic peptide act synergistically to accelerate tubule secretion, and their separate localisation may be important for the precise control of diuresis.

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