Neural and hormonal control of visceral systems

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Our long-term goals are to study how cells, tissues and organ systems in insects are regulated and integrated by neurons and neuroendocrine pathways that utilize a variety of neuroactive chemicals (neuropeptides and amines), G-protein coupled receptors (GPCRs) and second messengers. We are interested in determining how these systems participate in successful behaviours; including feeding, digestion, circulation of nutrients and waste, growth, and reproduction. We have observed that some neuroactive chemicals are expressed in a variety of cell types and these neuroactive chemicals might represent functional units that interact to bias the insect towards a new functional state or behaviour. These neuroactive chemicals are also components of the brain-gut axis and therefore serve as a link between the endocrine/neural system of the digestive tract, the neuroendocrine system, the central nervous system, and circulation of haemolymph (blood) and neurohormones. The research objects of the proposed research program involve discovery in the medically-important disease vector, Rhodnius prolixus, and lie in the following areas: 1) integrative control of blood-gorging and the storage and delivery of nutrients; 2) integrative control of reproduction in both male and female R. prolixus initiated by a blood meal; 3) identification of physiological effects of these neuroactive chemicals on circulation; and 4) molecular characterization and distribution of the GPCRs and their ligands involved in behaviours. Our scientific approach is holistic and incorporates multi-facetted aspects from gene to behaviour. We define the neural substrates and circuits (including their neuroactive chemicals and receptors) used in the integrative control of these behaviours using a variety of techniques including molecular biology, pharmacology, neurophysiology, physiological assays, peptide isolation, neural mapping and immunohistochemistry. Novelty and expected significance The importance of research into insects lies increasingly in the testing and demonstration of universal principles of neural organization and functioning, while identifying unique features for target of novel pest control strategies. The future is hopeful, especially for neuropeptides, where the intrinsic problems associated with their use have been overcome. In addition, there is some hope using symbiont-mediated RNAi, whereby the symbiont bacterium that lives in the R. prolixus gut can be modified to deliver dsRNA that targets neuropeptide-signalling pathways. This need for control is particularly relevant for our model, R. prolixus; a medically-important insect that is a major vector of human Chagas disease. While once considered to be confined to the Americas, Chagas disease now occurs throughout the World due to human migration and blood transfusions. Therefore, this research as outlined above, has the potential to discover lead compounds that can be developed into bio-pesticides in the future.