1. Department of Neuroscience, University of Kentucky, Lexington, KY 40508, USA
2. Spinal Cord and Brain Injury Research Center, University of Kentucky, Lexington, KY 40536, USA
3. Lexington Veterans Affairs Healthcare System, Lexington, KY 40502, USA
4. Department of Physiology, University of Kentucky, Lexington, KY 40508, USA