1. Department of Spinal Cord and Brain Injury Research Center, University of Kentucky College of Medicine, Lexington, Kentucky.
2. Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky.
3. Department of Neurosurgery, Wayne State University School of Medicine, Detroit, Michigan.
4. Department of Neuroscience, University of Kentucky College of Medicine, Lexington, Kentucky.
5. Department of Neurosurgery, University of Kentucky College of Medicine, Lexington, Kentucky.