Duncan Blair

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Eryn Werry

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Ryan Downey

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Duncan Blair- PhD Student

Figures 1 and 2

My work has primarily been focussed on attempting to gain a better understanding of the mechanisms involved in neurotransmitter release and action in the sympathetic nervous system.

Most recently, this work has involved using electrochemical techniques to monitor the release kinetics of neurotransmitter. Specifically, using continuous amperometry (or chronoamperometry), I have been investigating the release and clearance rates of noradrenaline (NAd) from sympathetic varicosities on the surface of mesenteric arteries. The data derived from this work helps to refine mathematical models of the diffusion of released transmitter either into the media of the vessel or through the adventitia, away from the vessel. Amperometry makes us of the fact that some neurotransmitters, including the catecholamines, are oxidisable. A small carbon fibre electrode is clamped at a potential above that required for transmitter oxidation. This electrode is placed against the tissue which is then electrically stimulated to induce transmitter release. When NAd comes into contact with the electrode, it is oxidised and the current required to maintain the electrode's potential is measure as the "oxidation current".

We also intend to extend this work to investigate the release of transmitter from single, visualised synapses in cultured sympathetic neurons.

Earlier work involved the design of novel peptides which were intended to interfere with key protein-protein interactions in the synaptic vesicle cycle. These peptides were then conjugated to a small peptide which spontaneously translocates across membranes. The carrier peptide, penetratin, is a 16 residue peptide derived from the Drosophila transcription factor, antennapedia and is capable of carrying covalently linked cargos into cells. Penetratin and the peptides of interest were synthesised with terminal cysteine residues to facilitate covalent linkage.

The efficacy of these peptides at inhibiting synaptic vesicle (SV) exocytosis in cultured sympathetic neurons was then assessed. This was achieved by loading cycling SVs with fluorescent, applying the penetratin-peptide conjugate and then monitoring dye loss on a confocal microscope during repeated stimulation to induce further SV cycling. Some of these peptides were then used to distinguish between what appears to be two types of transmitter release occurring on the surface of the mouse vas deferens. To achieve this, electrical recordings of the postsynaptic effect of transmitter release were made with extracellular electrodes places over visualised varicosities. The electrode was then perfused with a solution of penetratin-peptides conjugate and the effects on the type of signal produced were observed. The data from this work supports the notion that there a two distinct mechanisms of SV exocytosis occurring in this preparation.

Eryn Werry - Honours Student

Figure 1

If activated by a strong or enduring stimulus, neural pain circuits can change to create hyperalgesia and allodynia. Central to the creation of hyperalgesia is an increase in both substance P and glutamate in the dorsal horn of the spinal cord, whilst cytokines appear to be imperative for the appearance of allodynia. A recent theory has been proposed to explain the appearance of mirror-image allodynia and hyperalgesia that utilises the emerging picture of a reciprocal nature of communication between astrocytes and neurons. This theory is flawed on two accounts, however if it can be shown that substance P plays a part in the reciprocal communication between astrocytes and neurons, these flaws may be corrected. This research, then, aims to investigate whether substance P is a mediator of the reciprocal communication between astrocytes and neurons, and if found to be a mediator, what the nature and mediators of its role are.

Ryan Downey - Honours Student

Figures 1 and 2

As their name suggests, neuroglia (latin: nerve-glue) have historically been regarded merely as structural support for what were thought to be the pillars of nervous function, neurons. The critical role of glial cells in modulating the concentrations of ions, metabolites and neurotransmitters surrounding neurons as well as guiding synaptic development and neural growth is well established. Recent evidence has shown that with a full range of receptors and ion channels, glial cells can communicate with each other, as well as respond to and regulate neuronal activity. My research looks at the role that glia (Schwann cells) play in the superior cervical ganglion. More specifically, the response of Schwann cells to neurotransmitter is being examined.