Autonomic & Sensory Neurotransmission Laboratory

Research Projects

Mapping sensory neuron projections into the spinal cord with an in vitro tracing technique

Potentially noxious and painful stimuli are detected by a variety of different types of slowly conducting, small diameter sensory neurons (nociceptors). Recently we partially characterised a population of probable nociceptive neurons that do not express any of the well-known markers of nociceptive neurons. In order to determine the central projections of these neurons into the dorsal horn of the spinal cord, we developed an in vitro axonal tracing protocol, derived from that originally developed by Simon Brookes and his collaborators. By applying a low molecular weight tracer (Neurobiotin) to selected spinal nerves, we have identified and mapped the projections of the neurons projecting into the spinal cord from that segment. Consequently, we have identified the central projections of several different functional populations of sensory neurons that project into the superficial layers of the spinal cord where noxious information is processed. Some of these pathways have never been seen to clearly before. We also have developed a series of quantitative image analyses that allow us to objectively quantify the spatial organisation of sensory nerve endings in the spinal cord. These results are generating a radical new framework to understand the normal and pathological generation of pain responses.

Spinal sensory and autonomic motor pathways activated from the reproductive tract of female guinea-pigs

For many years we have been investigating the autonomic motor pathways innervating the vasculature of the reproductive tract of female guinea-pigs. In particular we have characterised vasodilator pathways that can be activated mostly from the lumbar spinal cord. We now have been doing a complex series of related experiments in vitro and in vivo to identify the sensory and spinal components of pathways that activate these vasodilator neurons.
Activation of the urethro-genital reflex, a well-established surrogate for sexual activity, stimulated increased expression of c-Fos, an intermediate early gene that identifies activated neurons, in the dorsal horn of the sacral spinal cord. Similarly, electrical stimulation of the pudendal nerves resulted in motor activity recorded electrophysiologically in the pelvic nerves. Thus, the urethro-genital reflex clearly activates sacral pathways to the reproductive tract. Stimulation of the pudendal nerve also activates an ascending spinal pathway with motor outflows from the lumbar spinal cord to the pelvic ganglia. This pathway is potentiated by pharmacological blockade of inhibitory GABA receptors in the spinal cord, indicating that this output is likely to be under tonic descending inhibition.
We also characterised the neurochemical profile and structure of different populations of sensory neurons that project from the external genitalia to the spinal cord. These observations suggest that there is a previously overlooked population of sensory neurons, containing the peptide, CGRP, but not substance P, that may transmit noxious mechanical stimuli from the genital tract.

Fluorescence correlation spectroscopy (FCS) and the direct visualisation of neuropeptide diffusion and receptor binding

Fluorescence correlation spectroscopy (FCS) is a sophisticated biophysical technique that allows direct estimation of diffusing fluorescent molecules using optical methods. The method takes advantage of confocal microscopy optics to count photons emitted by single fluorescent molecules diffusing through a tiny confocal detection volume (typically < 0.15 fl). We have been using FCS and high speed resonant scanning at 8kHZ (20 frames/sec) combined with ultra-sensitive single photon detectors to measure the diffusion of fluorescently-labelled peptides such as angiotensin II and substance P and their binding to receptors on cell lines and native sympathetic or sensory neurons.
We found that the cell membrane of cell lines expressing high levels of angiotensin  II receptors (visualised via linked fluorescent protein) is highly motile, using a mechanism that depends on an intact actin cytoskeleton. In contrast to cell lines, we observed that activated peptide receptors do not internalise in native sympathetic neurons, suggesting that these neurons use an unconventional signalling mechanism to maintain their responses to these agonists. Surprisingly, angiotensin II and substance P bind to the same microdomains on native sympathetic neurons, indicating that they are highly likely to operate cooperatively on the same pool of intracellular messengers to control neuronal excitability.

Neuroscience and the arts

Building on collaborative projects with artists begun in 2005 (that resulted in highly acclaimed public events) we have continued our explorations of the interfaces between neuroscience, human anatomy and a range of creative and performing arts. Ian continued to have considerable success with his poetry, being short listed for national competitions, including the prestigious Newcastle Poetry prize. He was commissioned to write text for Australian Dance Theatre’s acclaimed production “Be Your Self” that premiered at the 2010 Adelaide Festival of the Arts. Ian also spoke to a booked-out audience at RiAus about neuroscience, the body and poetry.

Neuroscience and education

2010 was the final year of the highly successful and innovative Graduate Certificate in Neuroscience (Learning) program, with collaborative teaching input from colleagues at the University of Adelaide and the University of South Australia. The program was directed mainly at teachers, many of whom have gone on to pursue research projects arising from their work. Ian also has spoken about neuroscience at a wide variety of other venues, including Rotary Clubs, University of the Third Age, and the Australian Science & Mathematics School. Ian and Catherine won a Teaching and Learning Innovation Grant to study how students learn anatomy which revealed a considerable number of new insights.

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Updated July 3, 2011