Overview
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The importance of the ability to detect environmental stimuli which have the potential to cause injury is perhaps best illustrated by individuals born with a congenital insensitivity to pain. These unfortunate children die at a young age from the horrific injuries they sustain due to their inability to detect stimuli which cause tissue damage. Pain then constitutes the conditioning stimuli which teaches as to avoid environmental stimuli which have the potential to cause harm. A second very important function of pain is to warn us about pathological states and thus initiate the appropriate behavioural response to promote healing (e.g limb immobilisation after a broken arm). Unfortunately in some disease states such as cancer or some nervous system lesions, the pain becomes intractable and even today treatment for such chronic pain is unsatisfactory. We have previously shown that a characteristic carbohydrate in expressed by the central terminals of unmyelinated sensory neurones. This galactose-containing, membrane-associated glycoconjugate is characterised by binding of the lectin Bandeiraea simplicifolia isolectin B4 (IB4). We have also shown that injection of the lectin, conjugated to the enzyme horseradish peroxidase (IB4-HRP), into a peripheral nerve, resulted in the conjugate being transported through the soma (left) to the central terminals of neurones with an axon in this nerve. The effectiveness of the uptake of IB4-HRP by this class of neurones is attributed to the presence of binding sites for this lectin on the plasma membrane which potentiates the uptake (and consequently transport) of the tracer. Demonstrating the effectiveness of uptake from the periphery is an important prerequisite to the development of other conjugates which may be used to modify nociceptor function by this population of neurones and thus produce analgesia. In this project the ability of IB4-HRP to be taken up and transported to the soma of unmyelinated sensory neurones following injection into peripheral tissues such as the skin will be investigated.
Approaches: Adult rats will be deeply anaesthetised and a series of small (2-4 microlitre) injections of IB4-HRP diluted in phosphate-buffered saline made into the skin on the plantar surface of both hindlimbs. Seven to fourteen days later the animals will be euthanased and the somtatotopically-appropriate lumbar dorsal root ganglia removed. These ganglia will then be serially-sectioned on a cryostat and enzyme histochemistry used to determine whether or not uptake and transport of the conjugate to the cell bodies has been effective. If injections in the skin are effective then the experiments will be repeated with injections into the skin and viscera to determine whether there is any target-tissue specificity in the uptake and transport of the conjugate.
Image: Labelling of small diameter sensory neurones following injection of IB4-HRP into a peripheral nerve.
References:
- Gerke, M.B. and Plenderleith, M.B. (2004) Analysis of the unmyelinated primary sensory neurone projection through the dorsal columns of the rat spinal cord using transganglionic transport of Bandeiraea simplicifolia I-isolectin B4. Journal of the Neurological Sciences. 22: 69-77.
- Gerke, M.B. and Plenderleith, M.B. (2004) Ultrastructural analysis of the central terminals of primary sensory neurones labelled by transganglionic transport of Bandeiraea simplicifolia I-isolectin B4. Neuroscience. 127: 165-175.
- Study level
- Honours
- Supervisors
- QUT
- Organisational unit
Science and Engineering Faculty
- Research area
- Contact
- Please contact the supervisor.
Dr Mark Plenderleith
