Following anesthesia, mice were perfused with PBS (pH 7.2). Brains and spinal cords were fixed with Clark's solution (75% ethanol and 25% glacial acetic acid), and embedded in paraffin. Spinal cords were divided into 6 sections prior to embedding, corresponding to cervical, thoracic and lumbar levels. Cross sections (6 mm), were stained with either hematoxylin and eosin (H&E) or luxol fast blue (LFB). Immunoperoxidase staining was used to identify activated astrocytes with anti-GFAP (AbCam, Cambridge, MA) and axonal integrity with SMI-31 and SMI-32 mAb (Sternberger Monoclonals Inc., Lutherville, MD) followed by visualization using Vectastain ABC kit (Vector Laboratories, Burlingame, CA) and 3,39-diaminobenzidine (Sigma-Aldrich).