Neuronal communication relies on the process of exocytosis by which neurons release a neurotransmitter. Exocytosis is critical for the simplest muscle movement to complex tasks such as learning and memory, and is altered in several neurodegenerative pathologies. We will investigate how the protein Munc18 controls exocytosis. This research will be important for understanding how neurons communicate in health and disease and will be relevant to other processes such as insulin release in diabetes.
Neuroendocrine Mechanisms By Which Leptin Regulates Reproduction
Funder
National Health and Medical Research Council
Funding Amount
$447,750.00
Summary
The reproductive system is sensitive to alterations in body weight. In particular, low body weight causes the reproductive system to cease functioning. This is because the brain 'senses' metabolic status and responds by ceasing to secrete the brain hormone that drives the reproductive process. This hormone is gonadotropin releasing hormone that acts on the pituitary gland to control the release of gonadotropins. These, in turn, act on the gonads. How the brain perceives metabolic status is not k ....The reproductive system is sensitive to alterations in body weight. In particular, low body weight causes the reproductive system to cease functioning. This is because the brain 'senses' metabolic status and responds by ceasing to secrete the brain hormone that drives the reproductive process. This hormone is gonadotropin releasing hormone that acts on the pituitary gland to control the release of gonadotropins. These, in turn, act on the gonads. How the brain perceives metabolic status is not known. Leptin is a hormone that is produced by fat and acts on the brain. This appears to be one of the means by which the reproductive system is regulated. Leptin also regulates food intake and other brain processes. Leptin acts on specific cell types in the brain. Some of these may have dual function to regulated appetite as well as reproduction. The present proposal is for work to determine mechanisms within the brain that are altered by leptin. We will also determine which specific mechanisms relate to the regulation of gonadotropin releasing hormone. The work will provide information on how putative appetite regulators might affect the reproductive axis. Such work will provide a platform for design of pharmaceutical means to manipulate the reproductive axis and will impact on the design of drugs that regulate obesity. It is possible that drugs that developed to control obesity may affect the reproductive axis and the project will identify these.Read moreRead less
Orexins As Neuroendocrine Integrators Between Nutrition And Reproduction Control Systems
Funder
National Health and Medical Research Council
Funding Amount
$332,036.00
Summary
Studies on humans and a range of animal species have shown that the effects of nutrition on reproduction are mediated at least partly by changes in the secretion of gonadotrophin releasing hormone (GnRH) and thus gonadotrophins. A number of metabolic signals must also be involved but those tested to date (glucose, insulin, leptin) do not seem to play major roles. Two exciting new candidates are orexin-A and orexin-B, a recently discovered pair of peptides that stimulate feeding behaviour. They a ....Studies on humans and a range of animal species have shown that the effects of nutrition on reproduction are mediated at least partly by changes in the secretion of gonadotrophin releasing hormone (GnRH) and thus gonadotrophins. A number of metabolic signals must also be involved but those tested to date (glucose, insulin, leptin) do not seem to play major roles. Two exciting new candidates are orexin-A and orexin-B, a recently discovered pair of peptides that stimulate feeding behaviour. They are synthesized in the brain and, in rodents, they either stimulate or inhibit gonadotrophin secretion, depending on the presence of sex steroids. In this project, we will investigate the roles of the orexins as integrators of signals about gonadal activity, nutrition and body condition, all of which affect the activity of the reproductive control centres in the brain. We will use the mature male sheep because it shows clear and repeatable reproductive responses to changes in nutrition. We will locate the orexin-producing cells and the cells that respond to the orexins, and show how orexin production is affected by diet. We will also study the ways in which the orexins affect, and are affected by, the hormone systems that control reproduction and metabolism. Finally, we will try to find out why there are two orexins by looking at how their actions differ. Ultimately, the orexin system might explain the brain processes that are behind many of the reproductive problems that are associated with metabolic disorders, such as appetite loss, excessive exercise, undernutrition, polycystic ovarian syndrome, and insulin-dependent diabetes.Read moreRead less
Neurons And Neurotransmitters That Control Phasic Laryngeal Motoneuron Activity
Funder
National Health and Medical Research Council
Funding Amount
$278,736.00
Summary
Opening and closing of the vocal cords with breathing is an automatic function that is present before birth and is essential for life. Opening the vocal cords allows inspired air to enter the lungs and closure serves to protect the lungs from food and drink. Failure of coordination is associated with a range of life-threatening airway disorders, particularly in newborns. Nerves in the brain and the chemicals they release transmit the rhythm of breathing to the nerves that control the vocal cords ....Opening and closing of the vocal cords with breathing is an automatic function that is present before birth and is essential for life. Opening the vocal cords allows inspired air to enter the lungs and closure serves to protect the lungs from food and drink. Failure of coordination is associated with a range of life-threatening airway disorders, particularly in newborns. Nerves in the brain and the chemicals they release transmit the rhythm of breathing to the nerves that control the vocal cords. However, the specific neurons and chemicals involved are not known. This information is crucial in understanding the chemical disorder in the brain responsible for the loss of coordination between breathing and vocal cord activity, and in formulating strategies to treat these conditions using drugs that correct the chemical disorder. By way of example, we have used our animal studies to develop the first ever drug trial to treat children with congenital vocal cord paralysis, whose vocal cords fail to open with inspiration and require a tracheostomy. We have selected a drug that corrects the proposed disorder of brain chemistry responsible for this condition. This approach will serve as a template for the management of a variety of other life-threatening airway disorders in newborns using drugs that act on the brain. We will now carry out further experiments to identify the nerves and their chemicals that control the motoneurons that drive the vocal cords. The key experiment involves recording from inside an individual vocal cord motoneuron in the brain while simultaneously applying a range of chemicals to its external surface. By recording the response of the nerve, we can determine which chemicals control its activity. Using our knowledge of the pattern of chemicals released by respiratory neurons, we will identify neurons for further study, and establish chemical and anatomical relationships between the respiratory nerve and the vocal cord nerve.Read moreRead less