Temporal relationship between the recovery of longitudinal reflex systems and motor recovery in chronic spinally-lesioned rats

Abstract

This study was performed to determine whether a correlation exists in the functional recovery of the longitudinal reflex systems and recovery of quadrupedal locomotion in chronic spinally-lesioned rats. Partial spinal lesions sparing only the right ventral quadrant (VQ) or dorsal quadrant (DQ) of the spinal cord at the lower thoracic (T9-10) levels were performed aseptically under Nembutal anesthesia. Quadrupedal locomotion reappeared within 2-3 weeks after the initial operations in VQ rats. However, no recovery of hindlimb movement was observed in DQ rats. In terminal experiments with VQ and DQ rats, the right brachial plexus (C6-T1) was dissected and mounted on a bipolar stimulating electrode. Spino-bulbo-spinal and interlimb reflex potentials were recorded from bilateral hindlimb muscles under urethane-chloralose anesthesia and Nembutal anesthesia, respectively. In VQ rats, these longitudinal reflex potentials could not be evoked for several days post-operatively. However, the early threshold elevation for evoking the reflex potentials returned gradually to the normal range in accordance with locomotor recovery. In DQ rats, on the other hand, disappearance of the reflex potentials persisted over 1 month observation period. These results suggest that the functional recovery of these longitudinal reflex systems in the ventral quadrant parallels the quadrupedal locomotor recovery after partial spinal cord lesions in rats.