Motor deficits following dorsal corticospinal tract transection in rats: voluntary versus skilled locomotion readouts

Following spinal cord injury, severe deficits result from damages to ascending and descending tracts, such as the corticospinal tract (CST) which is highly relevant for the motor execution in humans. Unfortunately, no curative treatment is available and intensive efforts are deployed in animal models, such as the CST transection model, to identify interventions providing functional regeneration after spinal cord injury. The CatWalk XT is a system for multi-parameter gait analysis of voluntary locomotion. In this study, the performance of the CatWalk XT for monitoring of functional deficits associated with dorsal CST lesion in rats was compared to skilled locomotion tests. Motor deficits associated with dorsal CST transection could be reliably monitored over seven weeks based on skilled locomotion testing, i.e. Horizontal Ladder Walk and Grid Walk. The collateral lesion to the overlaying gracile and cuneate funiculi occurring during dorsal CST transection resulted in slight hyposensitivity and proprioceptive deficit, which likely contributed to the lowered performance in skilled locomotion. In contrast, parameters of voluntary locomotion were not significantly affected by dorsal CST transection. Finally, an abnormal adduction reflex was detected immediately after lesion of the CST and could be conveniently used to confirm successful CST lesion in rats of experimental groups. The functional relevance of the dorsal CST in locomotion of rats is not as prominent as compared to in humans and thus challenging the motor execution is mandatory to reliably investigate CST function. A detailed analysis of voluntary walking using the CatWalk XT is not adequate to detect deficits following dorsal CST lesion in rats.