Although the heart contracts spontaneously, the rate and force with which it beats may be modified by the autonomic nervous system. That is, the rate and force of heart muscle contraction may be increased or decreased by the activation of two different sets of nerves. This project will determine how the autonomic nervous system modifies the strength of heart muscle contraction. It will involve the measurement of changes in contractile force, electrical activity and calcium levels within cardiac ....Although the heart contracts spontaneously, the rate and force with which it beats may be modified by the autonomic nervous system. That is, the rate and force of heart muscle contraction may be increased or decreased by the activation of two different sets of nerves. This project will determine how the autonomic nervous system modifies the strength of heart muscle contraction. It will involve the measurement of changes in contractile force, electrical activity and calcium levels within cardiac cells during muscle contraction. The effects of excitatory and inhibitory nerve stimulation on these three parameters will be examined. Results of this study will improve our understanding of how the contraction of heart muscle is controlled and provide an insight into the treatment of heart disease.Read moreRead less
Peripheral Mechanisms Involved In Autonomic Hyperreflexia
Funder
National Health and Medical Research Council
Funding Amount
$229,917.00
Summary
Bladder distension or minor unheeded injuries below the lesion in spinally injured people often lead to episodes of high blood pressure that may cause stroke or death. These events require emergency hospitalization and are expensive as well as dangerous. After spinal injury, the control of sympathetic nerves that supply arteries and regulate blood pressure is lost. However, the nerves below the injury remain in place and the spinal cord below the lesion contains connections that can activate the ....Bladder distension or minor unheeded injuries below the lesion in spinally injured people often lead to episodes of high blood pressure that may cause stroke or death. These events require emergency hospitalization and are expensive as well as dangerous. After spinal injury, the control of sympathetic nerves that supply arteries and regulate blood pressure is lost. However, the nerves below the injury remain in place and the spinal cord below the lesion contains connections that can activate them. Signals from the bladder or skin enter the remaining lower part of the spinal cord and activate the sympathetic supply generating a rise in blood pressure. This project will test the hypothesis that increased sensitivity of arteries to the chemicals released from the sympathetic nerves leads to excessive vessel constriction, contributing to the exaggerated increase in pressure. We will investigate arteries removed from rats with experimental spinal transection. We will test the contractions of the arteries (a) to sympathetic nerve stimulation and (b) to the chemicals noradrenaline, adenosine 5'-triphosphate (ATP) and neuropeptide Y that are normally released during nerve activity. We will determine whether release of noradrenaline and ATP from nerves is normal or augmented using electrochemical and electrophysiological techniques. We will compare the responses with those in normal arteries, those in arteries whose nerves have been silenced by removing all connections from the spinal cord and those in arteries that have lost all their nerve supply. This will enable us to identify whether the mechanisms for release of transmitter substances are modified and whether the arterial muscle is hypersensitive to these substances. The results will help in the design of safer treatment for these potentially lethal emergencies in spinal patients.Read moreRead less
Neurotransmission In Functionally Distinct Vasodilator Pathways
Funder
National Health and Medical Research Council
Funding Amount
$809,934.00
Summary
A surprising feature of our body is that there is not enough blood to fully supply all our organs at once. This is why we sometimes faint when we are hot or get cramps when we are exercising. Consequently, the blood vessels change their diameter so that blood can be directed to the organs with greatest demand at any particular time. For example, if the vessel decreases in diameter, less blood flows through it, but if it increases in diameter, more blood flows through it to reach the appropriate ....A surprising feature of our body is that there is not enough blood to fully supply all our organs at once. This is why we sometimes faint when we are hot or get cramps when we are exercising. Consequently, the blood vessels change their diameter so that blood can be directed to the organs with greatest demand at any particular time. For example, if the vessel decreases in diameter, less blood flows through it, but if it increases in diameter, more blood flows through it to reach the appropriate organ. An important function of the nervous system is to control the flow of blood to different organs by changing the diameters of the blood vessels. One set of nerves decreases the diameter of the arteries, and another set of nerves increases the diameter. The nerves do this by releasing special combinations of chemicals when they get a message from the brain to do so. In this project we are especially interested in the nerves which increase blood flow to organs in the head and the pelvis. We will use a wide range of modern methods to find out how these nerves work. In some experiments, we will use sophisticated electrical equipment to measure just how the nerve cells controlling the diameter of the vessels respond to the instructions sent by the brain. In other experiments, we will find out which chemicals the nerves use to make the blood vessels increase in diameter. We also will discover how the various chemicals get released by the nerves at the right times, so that messages from the brain get to the blood vessels as efficiently as possible. One of the special parts of our project is that we will be able to observe directly the connections between the nerve cells and the blood vessels we are studying. Our results will be important for designing new drugs that could help people whose nerves are not working properly, such as in some patients with diabetes or vascular disease.Read moreRead less