Grant: Operating Grant

Spinal cord injury affects 36,000 Canadians. It is associated with lifetime care costs ranging from $1.25 to 25 million. The brain sends signals to the lower part of the spinal cord that activate neural circuits responsible for walking. Individuals with spinal cord injury are unable to walk because these connections are interrupted. Until recently scientists assumed that long continuous nerve pathways were responsible for sending the command signal for walking. However, our recent experiments showed that another system can be used for this purpose. It involves relaying nerve signals through a series of short nerve cells, like a water bucket passed from one person to the next until it reaches the fire. This system should be much easier to repair because relay nerve cells need to re-grow only a short distance, until the next relay neuron below the injury is contacted. They do not need to re-grow the entire length of the spinal cord, which is the very difficult challenge faced by long continuous pathways. We now propose to further study this newly discovered relay pathway underlying the activation of walking. More specifically, we will determine which nerve cells in the brain activate the spinal relay system. We will examine whether the relay system is present in adult animals (our earlier work used newborn rats). Finally, we will determine whether artificial excitation of the relay pathway can promote transmission of the signal for walking through the site of spinal cord injury. If successful, this would allow improved voluntary control of walking despite spinal cord injury. The long-term goal is to apply drugs to the spinal cord of humans with spinal cord injury to facilitate or enable walking. Theoretically, this could be done using clinical technology that already exists (drug pumps with small tubes that lead to the spinal cord - for the treatment of other conditions such as pain and spasticity).