Nitric oxide (NO) plays an important role in neurotransmission, vascular regulation, immune response and apoptosis. NO has been established as one of the key regulators in cardiovascular, nervous, and immune systems. NO plays a pivotal role in numerous processes: in central nervous system, NO participates in cell communication and information storage; in vascular endothelium, NO is involved with regulation of vascular function. Finally, NO is produced by immune cells, including macrophages, as a part of body's defense mechanism during immunological responses and oxidative stress conditions. However, chronic overproduction of NO is one of the fundamental causes underlying disorders including neurodegenerative diseases and pathophysiology of