Mechanisms Of Long Term Excitability Changes In Enteric Neurons
Funder
National Health and Medical Research Council
Funding Amount
$308,250.00
Summary
The intestine contains within its walls a nerve circuitry, the enteric nervous system, that controls many of its activities. The intestine itself adapts to circumstances, such as diet, and to pathological changes, such as infection or inflammation. In fact, changes in the intestine can outlast the events that cause them. This implies that there are prolonged changes in properties of control systems in the intestine. We have discovered that the intrinsic sensory neurons of the intestine exhibit l ....The intestine contains within its walls a nerve circuitry, the enteric nervous system, that controls many of its activities. The intestine itself adapts to circumstances, such as diet, and to pathological changes, such as infection or inflammation. In fact, changes in the intestine can outlast the events that cause them. This implies that there are prolonged changes in properties of control systems in the intestine. We have discovered that the intrinsic sensory neurons of the intestine exhibit long-term excitability increases following prolonged, low frequency, stimulation of their inputs from other neurons. This phenomenon has been called sustained slow postsynaptic excitation (SSPE). We have begun to examine the mechanisms behind the SSPE, and have discovered that it involves the enzymatic modification of molecules in the intrinsic sensory neurons. In this work, we will identify the enzymes and their molecular targets. This will add to basic knowledge of how the digestive system performs its task and adapts over time. It will provide data that can be used to predict molecules that might be of therapeutic value in dealing with chronic disorders in the intestine, such as irritable bowel syndrome.Read moreRead less
Heartbeats are considered to arise through specialised pacemaker cells establishing rhythmically generated (i.e. pacemaker) action potentials, which then trigger propagating action potentials in heart muscle causing contraction and pumping of blood. This research proposal aims to challenge the physical model that is used to describe this pacemaker process and resultant heart conduction. Our reasons for doing this derive from our discovery of an alternative pacemaker-conduction mechanism, which w ....Heartbeats are considered to arise through specialised pacemaker cells establishing rhythmically generated (i.e. pacemaker) action potentials, which then trigger propagating action potentials in heart muscle causing contraction and pumping of blood. This research proposal aims to challenge the physical model that is used to describe this pacemaker process and resultant heart conduction. Our reasons for doing this derive from our discovery of an alternative pacemaker-conduction mechanism, which we have shown to operate in various smooth muscles. This mechanism, termed store-based pacemaking, is entirely different to the currently held cardiac model but could readily achieve the same outcome. We will investigate the hypothesis that this pacemaker mechanism is also fundamental to heart pacemaking and conduction. Positive support for our hypothesis, as indicated by our pilot findings, may severely challenge the present model for cardiac pacemaking. Such an outcome will have major ramifications on present interpretation of cardiac function in health and disease and will be particularly important to interpretation of disorders associated with cardiac arrhythmias and heart conduction.Read moreRead less
Neural Mechanisms Mediating Hypersecretion And Motility Patterns Induced By Enterotoxins
Funder
National Health and Medical Research Council
Funding Amount
$415,250.00
Summary
This project aims to identify the nerve cells that are responsible for the massive oversecretion of water and salt seen with cholera and other diseases producing diarrhoea. Many of these disease act through specific toxins and, although the biochemical targets of these toxins are reasonably well understood, the nerve cells on which they act have never been identified. Furthermore, the mechanisms that couple the oversecretion with a massive increase in the propulsive activity of the intestine are ....This project aims to identify the nerve cells that are responsible for the massive oversecretion of water and salt seen with cholera and other diseases producing diarrhoea. Many of these disease act through specific toxins and, although the biochemical targets of these toxins are reasonably well understood, the nerve cells on which they act have never been identified. Furthermore, the mechanisms that couple the oversecretion with a massive increase in the propulsive activity of the intestine are also unknown. We will investigate each of these questions using the small intestine of the guinea-pig, because the nerve circuit in this preparation is better understood than that of any other. Nerve cells that respond to three specific toxins, each known to activate the nervous system via different mechanisms, will be determined using intracellular recording methods, injection of marker dyes and methods that allow the identification of their neurochemistry. This will allow the functions of responsive nerve cells to be identified and their places in the circuits that control secretion and propulsion to be determined. This information will be correlated with studies in whole animals being undertaken in Sweden so that potential sites for intervention can be identified.Read moreRead less
Distribution, Pharmacology, Molecular Identity And Roles Of Purine Receptors In Enteric Neurons
Funder
National Health and Medical Research Council
Funding Amount
$395,250.00
Summary
Digestive function needs to be adapted to the great variety of foods that we eat, and to our variable dietary habits. Adaptation is controlled through an extensive nervous system in the wall of the gastrointestinal tract, the enteric nervous system, and through digestive system hormones. The enteric nervous system detects the volume and key chemical components in the gastrointestinal lumen and, through an integrating nerve circuitry, causes changes in the patterns of movement, fluid secretion an ....Digestive function needs to be adapted to the great variety of foods that we eat, and to our variable dietary habits. Adaptation is controlled through an extensive nervous system in the wall of the gastrointestinal tract, the enteric nervous system, and through digestive system hormones. The enteric nervous system detects the volume and key chemical components in the gastrointestinal lumen and, through an integrating nerve circuitry, causes changes in the patterns of movement, fluid secretion and local blood flow. Digestive system diseases, for example irritable bowel syndrome, can involve disordered function of the enteric nervous system, and there is considerable research and development focus to identify drug targets in the enteric nervous system that can be used in therapy. Amongst potential targets are receptors for purines that are located on enteric neurons and are one of the important classes of receptor that is involved in communication between the neurons. These studies aim to identify the purine receptors, their roles in controlling digestive function and their potential as therapeutic targets in the treatment of digestive disease.Read moreRead less
Convergent Regulation Of Sympathetic Neuronal Excitability By Peptide Hormones And Transmitters
Funder
National Health and Medical Research Council
Funding Amount
$498,465.00
Summary
This project will examine how hormones involved in regulating blood pressure interact with the nerves that control blood flow to the gut. We will combine electrical recordings of the activity of single nerve cells with an innovative new method of optically tracking the movements of single molecules, including hormons and neuronal messengers, that send signals to the nerve cells. Our results will reveal how blood pressure is normally maintained at healthy levels, even if we are ill.
Role Of Calcium Channels And Small-conductance Potassium Channels In Myenteric Neurons
Funder
National Health and Medical Research Council
Funding Amount
$131,717.00
Summary
This proposal will investigate the electrical properties of neurons in the wall of the intestine that control movements of the bowel. These neurons form an extensive network that runs the length of the gastrointestinal tract and control mixing and propulsion of food along the intestine. We will determine the basic electrical properties of these neurons and investigate why some of them transmit signals in a continuous manner while others transmit signals intermittently and how these patterns of a ....This proposal will investigate the electrical properties of neurons in the wall of the intestine that control movements of the bowel. These neurons form an extensive network that runs the length of the gastrointestinal tract and control mixing and propulsion of food along the intestine. We will determine the basic electrical properties of these neurons and investigate why some of them transmit signals in a continuous manner while others transmit signals intermittently and how these patterns of activity fit into the overall activity of the gut. This study will build on a large body of data obtained from our laboratory that has shown that some of these neurons act as sensors of the presence-absence of food in the intestine while others send signals to the muscle in the wall of the intestine to either relax or contract it so that the food can be processed properly. By knowing what makes these neurons different from each other we will be able to understand what goes wrong in functional bowel disorders where motility is affected, resulting in pain and discomfort.Read moreRead less