Effects of Rehabilitation on Perineural Nets and Synaptic Plasticity Following Spinal Cord Transection

Epidural electrical stimulation (ES) of the lumbar spinal cord combined with daily locomotor training has been demonstrated to enhance stepping ability after complete spinal transection in rodents and clinically complete spinal injuries in humans. Although functional gain is observed, plasticity mechanisms associated with such recovery remain mostly unclear. Here, we investigated how ES and locomotor training affected expression of chondroitin sulfate proteoglycans (CSPG), perineuronal nets (PNN), and synaptic plasticity on spinal motoneurons. To test this, adult rats received a complete spinal transection (T9–T10) followed by daily locomotor training performed under ES with administration of quipazine (a serotonin (5-HT) agonist) starting 7 days post-injury (dpi). Excitatory and inhibitory synaptic changes were examined at 7, 21, and 67 dpi in addition to PNN and CSPG expression. The total amount of CSPG expression significantly increased with time after injury, with no effect of training. An interesting finding was that γ-motoneurons did not express PNNs, whereas α-motoneurons demonstrated well-defined PNNs. This remarkable difference is reflected in the greater extent of synaptic changes observed in γ-motoneurons compared to α-motoneurons. A medium negative correlation between CSPG expression and changes in putative synapses around α-motoneurons was found, but no correlation was identified for γ-motoneurons. These results suggest that modulation of γ-motoneuron activity is an important mechanism associated with functional recovery induced by locomotor training under ES after a complete spinal transection

Effects of treadmill training on microvascular remodeling in the rat following spinal cord injury

Introduction: The morphological characteristics of skeletal muscles innervated caudal to a spinal cord injury (SCI) undergo dramatic phenotypic and microvascular changes. Method: Female Sprague Dawley rats received a severe contusion at thoracic level 9/10, and were randomly assigned to locomotor training (TR), epidural stimulation (ES) or a combination of the treatment groups (CB). Fibre type composition and capillary distribution were assessed in phenotypically distinct compartments of the tibialis anterior. Results: SCI induced a shift in Type II fibre phenotype from oxidative to glycolytic (P<0.05) as well as capillary loss within the oxidative core and glycolytic cortex; the CB treatment best maintained capillary supply within both compartments. Discussion: The angiogenic response of CB training improved capillary distribution across the muscle, becoming spatially more homogeneous and decreasing mean capillary supply area, potentially improving oxygenation. There is an important role for weight bearing training in maintaining the oxidative phenotype of muscle following SCI