Dorsolateral cervical spinal injury differentially affects forelimb and hindlimb action in rats

In experimental spinal injury studies, damage to the dorsal half of the spinal cord is common but the behavioural effects of damage to specific pathways in the dorsal cord have been less well investigated. We performed bilateral transection of the dorsolateral spinal funiculus (DLF) on 12 Long-Evans rats at the third cervical spinal segment. We quantified overground locomotion by measuring ground reaction forces, step timing and step distances as animals moved unrestrained. We also assessed skilled locomotion by measuring footslip errors made while the animals crossed horizontal ladders, and examined paw usage in a cylinder exploration task and during a skilled reaching task. Ground reaction forces revealed that rats with bilateral DLF lesions moved with a symmetrical gait, characterized mainly by altered forces exerted by the hindlimbs, delayed onset of hindlimb stance, and understepping of the hindlimbs relative to the forelimbs. These alterations in overground locomotion were subtle but were nevertheless consistent between animals and persisted throughout the 6-week recovery period. During ladder crossing, rats with DLF lesions made more footslip errors with the hindlimbs after surgery than before. Spontaneous forelimb usage during exploration was not affected by DLF axotomy but lesioned animals were less successful during skilled reaching. This is the first study which describes preferentially altered hindlimb use during overground locomotion after cervical DLF transections. We discuss these findings in relation to previous work and to the possible contributions of different ascending and descending pathways in the DLF to locomotion and skilled movements in rats.