Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/1999
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 eunsuitable 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. In this paper, we describe new information about the mechanism of action of a hormone that induces both the processes of normal birth and, depending on the timing of exposure, abortion of offspring in the tsetse fly. It further identifies two other insect neuropeptide classes, proctolin and th pyrokinins, that can induce abortion and/or the birthing process in this fly. The work presents another target with which to disrupt pest insect development via exposure to mimetic analogs of the aforementioned neuropeptides that are resistant to the enzymes which inactivate the natural hormones. 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: Parturition hormone (PH) activity is present not only in the uterus of the tsetse Glossina morsitans but also in the oviducts of Bombyx mori and Schistocerca gregaria, as well as the ejaculatory duct of S. gregaria males. Activity thus appears to be present in the reproductive ducts of diverse insect taxa. To determine whether any of the common insect neuropeptides are capable of mimicking the effect of PH, 35 identified neuropeptides and analogs were evaluated for PH activity. Modest PH activity was observed for only high doses of proctolin and a pyrokinin analog, thus suggesting that PH is unlikely to be closely related to any of the identified neuropeptides tested. While proctolin was highly effective in stimulating contractions of the S. gregaria oviduct, the extract from the tsetse uterus elicited only a weak response in this bioassay. PH activity was, however, effectively mimicked with an injection of 8 bromo-cyclic GMP, thus suggesting a potential role for this cyclic nucleotide in mediating the PH response. Pregnant females were responsive to PH, other neuropeptides and cyclic nucleotides only when females were neck-ligated. In intact females, the brain can presumably override the stimulation provided by the active compounds.