MECHANISMS OF TRANSMITTER SECRETION AT SYMPATHETIC NERVE VARICOSITIES
Funder
National Health and Medical Research Council
Funding Amount
$438,707.00
Summary
The mechanism by which quantal packets of transmitter are secreted from release sites called varicosities on sympathetic nerve terminals can now be taken to the molecular level, given the new techniques which we have introduced to solve this problem. There are two main facets to the problem. The first of these involves the question of how proteins involved in controlling the regulated secretion or exocytosis of the quantal packets of transmitter carry out this function. These proteins (syntaxin, ....The mechanism by which quantal packets of transmitter are secreted from release sites called varicosities on sympathetic nerve terminals can now be taken to the molecular level, given the new techniques which we have introduced to solve this problem. There are two main facets to the problem. The first of these involves the question of how proteins involved in controlling the regulated secretion or exocytosis of the quantal packets of transmitter carry out this function. These proteins (syntaxin, synaptobrevin, SNAP25 and synaptotagmin) together with a calcium channel are complexed with a docked synaptic vesicle containing a quantum of transmitter in a module of secretion appropriately called a secretosome. The leading questions here are to determine if only a single secretosome participates in transmitter release on the arrival of a nerve impulse, whether the number of these secretosomes in a varicosity determines its probability for secretion of a quantum, and fundamentally, how do the proteins within the secretosome cooperate to trigger exocytosis when there is sufficient calcium influx through the secretosome-associated calcium channel following the impulse. The other problem concerns the mechanism of removal of calcium from the varicosity once it has entered through the channels, This calcium can have considerable affects on the extent to which secretosomes participate in secretion with subsequent impulses. Furthermore, this influx of calcium can be modulated for subsequent impulses by transmitter released by the first impulse. The present research will solve these problems, providing a molecular description of secretion from single sympathetic varicosities.Read moreRead less
Sensory Mechanisms In Normal Bladder And In Cystitis
Funder
National Health and Medical Research Council
Funding Amount
$408,861.00
Summary
The function of the lower urinary tract is to store urine and release it at appropriate times. This requires neural circuits in the brain, spinal cord and peripheral ganglia. When the bladder fills, sensory neurones fire and activate these neural circuits to store urine or to empty the bladder. If sensory neurones are too easily excited (a process called sensitisation ) this will lead to clinical disorders, including the common painful bladder syndromes, whose cause is not known (interstitial cy ....The function of the lower urinary tract is to store urine and release it at appropriate times. This requires neural circuits in the brain, spinal cord and peripheral ganglia. When the bladder fills, sensory neurones fire and activate these neural circuits to store urine or to empty the bladder. If sensory neurones are too easily excited (a process called sensitisation ) this will lead to clinical disorders, including the common painful bladder syndromes, whose cause is not known (interstitial cystitis, sensory urgency etc). These are characterised by pelvic pain, urinary urgency, frequency and, in some cases, urge incontinence (loss of urine for no apparent reason) which results from unstable or overactive bladder. Despite a large database of knowledge about the sensory innervation of the bladder, many important gaps still exist. These gaps have restricted the development of new therapies. For example, we have little idea about exactly which functional classes of sensory neurones signal filling of the normal bladder or what different types of information they carry. This is vital information for understanding which neurones are affected in disease states and whether they are all affected in the same way. We have developed new methods that will allow us to identify the major classes of sensory neurones that innervate the bladder, what they respond to and how they are activated. We will also determine whether some classes are preferentially sensitised by inflammation and the most important mechanisms that are likely to underlie this. The significance of this project is that it provides the basic scientific understanding of sensory innervation of the bladder and will identify potential targets for selective pharmacological intervention in common bladder disorders.Read moreRead less