Role of Spared Pathways in Locomotor Recovery after Body-Weight-Supported Treadmill Training in Contused Rats

Abstract

Body-weight-supported treadmill training (BWSTT)-related locomotor recovery has been shown in spinalized animals. Only a few animal studies have demonstrated locomotor recovery after BWSTT in an incomplete spinal cord injury (SCI) model, such as contusion injury. The contribution of spared descending pathways after BWSTT to behavioral recovery is unclear. Our goal was to evaluate locomotor recovery in contused rats after BWSTT, and to study the role of spared pathways in spinal plasticity after BWSTT. Forty-eight rats received a contusion, a transection, or a contusion followed at 9 weeks by a second transection injury. Half of the animals in the three injury groups were given BWSTT for up to 8 weeks. Kinematics and the Basso-Beattie-Bresnahan (BBB) test assessed behavioral improvements. Changes in Hoffmann-reflex (H-reflex) rate depression property, soleus muscle mass, and sprouting of primary afferent fibers were also evaluated. BWSTT-contused animals showed accelerated locomotor recovery, improved H-reflex properties, reduced muscle atrophy, and decreased sprouting of small caliber afferent fibers. BBB scores were not improved by BWSTT. Untrained contused rats that received a transection exhibited a decrease in kinematic parameters immediately after the transection; in contrast, trained contused rats did not show an immediate decrease in kinematic parameters after transection. This suggests that BWSTT with spared descending pathways leads to neuroplasticity at the lumbar spinal level that is capable of maintaining locomotor activity. Discontinuing training after the transection in the trained contused rats abolished the improved kinematics within 2 weeks and led to a reversal of the improved H-reflex response, increased muscle atrophy, and an increase in primary afferent fiber sprouting. Thus continued training may be required for maintenance of the recovery. Transected animals had no effect of BWSTT, indicating that in the absence of spared pathways this training paradigm did not improve function.

Supraspinal Control Predicts Locomotor Function and Forecasts Responsiveness to Training after Spinal Cord Injury

“…116 For this reason, there are new approaches that aim to improve locomotor function by increasing effectiveness of the spared corticospinal or corticoreticulospinal pathways. 117 This premise has been tested in an operant conditioning training program in humans targeting improved volitional control of ankle dorsiflexion.…”

Undirected compensatory plasticity contributes to neuronal dysfunction after severe spinal cord injury

“…Various studies in experimental animals uncovered a mosaic of injury-induced molecular and cellular changes in segments caudal to a SCI (Krenz and Weaver, 1998;Ballermann and Fouad, 2006;Kitzman, 2006Kitzman, , 2007Soares et al, 2007;Hou et al, 2008;Tan et al, 2008;Hou et al, 2009;Boulenguez et al, 2010;Murray et al, 2010;Ichiyama et al, 2011;Singh et al, 2011;Kapitza et al, 2012;Tan et al, 2012). Depending upon the SCI model and specific functional assessments, these alterations in the properties of neuronal circuits have alternatively been classified as beneficial or detrimental.…”

The effect of timing electrical stimulation to robotic-assisted stepping on neuromuscular activity and associated kinematics

“…Previous studies have reported a beneficial effect of treadmill training in spinally contused rats [47,68]. However, such benefits do not result when high levels of robotic assistance are applied during the training [46].…”