Training improves the electrophysiological properties of lumbar neurons and locomotion after thoracic spinal cord injury in rats

The aim of the present study was to evaluate the effect of a stepping-based rehabilitation program in voluntary wheel cages on the functional recovery and electrophysiological properties of neurons in the rat lumbar spinal cord after compressive thoracic (T10) spinal cord injury (SCI). A significant decrease in stance/swing duration and the number of limbs simultaneously in the stance phase was seen in trained compared to sedentary rats at 28 days after SCI (p < 0.05). These kinematic improvements were associated with a significant increase in the amplitude of extracellular recordings from the tibial motoneuron pool in response to descending neuronal drive as well as significant amelioration of electrophysiological properties assessed from intracellular recordings. In fact, electrophysiological properties were not significantly different between uninjured controls and SCI-trained rats. Brain-derived neurotrophic factor (BDNF) levels were significantly elevated in the lumbar spinal cord of SCI-trained rats compared to SCI-sedentary controls. The data support a therapeutic role of increased neuromuscular activity in promoting functional recovery and suggest that it might occur via the beneficial effects of neurotrophic factors on neuronal plasticity.