The effect of noradrenergic drugs on the recovery of walking after spinal cord injury

Clonidine, a noradrenergic agonist has been associated with improved walking in both spinal cat and spinal cord injured (SCI) subjects. Objectives: The objective of this brief review is to compare the effects of clonidine on walking capabilities in SCI subjects with functionally complete and incomplete spinal cord injuries. Study design/methods: Both oral administration and intrathecal injection of clonidine were investigated. A motorized treadmill was used and harness support provided in most of the SCI subjects as no walking capabilities could be observed overground. A single subject design was used in these chronic SCI subjects. Setting: Canada and France. Results: In complete SCI subjects while receiving clonidine, none of the subjects was able to initiate independent stepping. In contrast, the greatest effects were found in SCI subjects with injuries that are incomplete but still severely disabling while minimal effects could be observed in the more functional SCI subjects. These effects on walking are observed in measures of walking speed, and electromyographic and kinematic patterns. Regardless of effects on walking, however, a consistent decrease of the flexor reflex amplitude could be observed in all SCI subjects independent of the severity of the lesion. Conclusion: This review demonstrated that clonidine could be a powerful anti-spasmodic drug in addition to improving locomotion in a limited number of SCI subjects. The mechanism, significance and implications of these results will be discussed. Sponsorship: Fonds de la recherche en Sante du Quebec, Echange Franco-Quebec and network center of excellence in Neurosciences. Spinal Cord (2003) 41, 137-143. doi:10.1038/sj.sc.3101374.