Encephalomyelitis, Autoimmune, Experimental/drug therapy; Encephalomyelitis, Autoimmune, Experimental/pathology; Phosphodiesterase 5 Inhibitors/therapeutic use; Piperazines/therapeutic use; Spinal Cord/pathology; Sulfones/therapeutic use; Animals; CD3 Complex/metabolism; Demyelinating Diseases/drug therapy; Demyelinating Diseases/etiology; Demyelinating Diseases/metabolism; Disease Models, Animal; Encephalomyelitis, Autoimmune, Experimental/chemically induced; Female; Forkhead Transcription Factors/metabolism; Gene Expression Regulation/drug effects; Gene Expression Regulation/physiology; Glial Fibrillary Acidic Protein/metabolism; Gliosis/drug therapy; Gliosis/etiology; Glycoproteins/adverse effects; Intercellular Adhesion Molecule-1/metabolism; Mice; Mice, Inbred C57BL; Myelin-Oligodendrocyte Glycoprotein; Neurofilament Proteins/metabolism; Peptide Fragments/adverse effects; Purines/therapeutic use; Sildenafil Citrate; Spinal Cord/drug effects; Time Factors