Central Nervous System/growth & development; Central Nervous System/metabolism; Myelin Proteins/metabolism; RNA, Messenger/metabolism; Aging/metabolism; Animals; Blotting, Northern; Blotting, Western; Brain Injuries/metabolism; Brain Injuries/pathology; Central Nervous System/cytology; Cerebellum/cytology; Cerebellum/growth & development; Cerebellum/metabolism; Cerebral Cortex/cytology; Cerebral Cortex/growth & development; Cerebral Cortex/metabolism; Hippocampus/cytology; Hippocampus/growth & development; Hippocampus/metabolism; Immunohistochemistry; In Situ Hybridization; Myelin Proteins/genetics; Neurites/metabolism; Neurites/ultrastructure; Nogo Proteins; Organ Specificity; Protein Isoforms/genetics; Protein Isoforms/metabolism; Rats; Spinal Cord/cytology; Spinal Cord/growth & development; Spinal Cord/metabolism; Spinal Cord Injuries/metabolism; Spinal Cord Injuries/pathology