Restoration of Motor Functions in Spinal Rats by Electrical Stimulation of the Spinal Cord and Locomotor Training

The recovery of motor functions in chronic spinal rats with locomotor training on a treadmill combined with electrical stimulation of the spinal cord was studied. Training to a bipedal gait on a moving band with the body weight supported and use of either subcutaneous or epidural electrical stimulation (40 Hz) was performed for five days per week for 20–30 min. The dynamics of changes in locomotor capacity using subcutaneous and epidural electrical stimulation and their actions on the neural structures of the spinal cord could be similar. After three weeks of motor rehabilitation, a single stimulation at a frequency of 1 Hz evoked reflex monosynaptic potentials in the hindlimb muscles, while simultaneous rhythmic stimulation of two loci in the spinal cord at a frequency of 40 Hz initiated locomotor-like activity on the moving band of the treadmill. A more marked rhythm was seen after nine weeks of training, which coincided with the appearance of polysynaptic spinal reflexes. Administration of the serotonin receptor agonist quipazine enhanced polysynaptic activity in reflex responses and improved locomotion. Use of noninvasive subcutaneous stimulation in combination with locomotor training was found to be an effective method of activating neural locomotor networks to an extent comparable to that obtained with invasive epidural stimulation.