Sensory pathways from the gastrointestinal mucosa

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Obesity is a looming health crisis for Australians; it increases the chances of many serious diseases including diabetes, cancer, stroke and heart disease. Obesity occurs when the amount of energy consumed in food is greater than the energy used over an extended period. Because human beings usually get most of their food in a few meals each day, the size of those meals is very important. Deciding when to stop eating can exert a powerful control on energy intake. It is well known that nutrients reaching the gut cause the release of hormones from cells in the lining of the stomach and intestine. These hormones tell the brain when enough food has been consumed. It used to be thought that the hormones travelled in the blood stream to affect the brain directly. Recently, it has become clear that much of their effect is actually carried by sensory neurons with endings in the lining of the gut. The hormones have a powerful effect the sensory nerve fibres which then send electrical signals in nerve fibres running in the vagus nerve to the brain. Here they make connections which eventually influence the centres that control feeding. There is much to understand about how hormones affect the sensory nerve endings in the wall of the gut, whether all nerve fibres are affected the same way and what sort of information is conveyed to the brain. This project will use electrophysiological methods to identify which nerve fibres are activated by hormones, whether different hormones affect different nerve fibres, which nutrients activate particular nerve fibres and whether nerve fibres make selective contacts with particular hormone-releasing cells. These questions are important for understanding how we normally stop feeding and how drugs might be designed to cause feelings of fullness earlier in each meal.