Responses of dorsal root ganglion cells to increased and decreased neuromuscular activity

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Very little is known as to the effects of increased and decreased physical activity on the properties of sensory nerves.  The proposed research program will examine the large sensory cells innervating mechanoreceptors in the hindlimbs of rats exposed to 1 month of increased (treadmill training and voluntary wheel exercise) or decreased (unilateral hindlimb paralysis and simulated weightlessness via hindlimb suspension) daily neuromuscular activity.  Properties to be measured in dorsal root ganglion cells include their electrophysiological properties and ion current densities, the expression of genes coding for neurotrophic factors and ion channel subunits, their metabolic signaling responses to acute electrical stimulation, and their synaptic efficacy with alpha-motoneurones in spinal cord.  Techniques to be used range from electrophysiological to immunohistochemical, and on to procedures used to detect changes in gene expression.  The information emanating from these experiments will give us some direction in examining physical activity effects on other types of sensory cells, such as pain afferents, and in more complex systems, such as brain and spinal cord.