[Free radicals and neural cell damage].

Free radicals are species containing unpaired electron, such as superoxide, hydroxyl radical and nitric oxide. The non-radical hydrogen peroxide is easily converted to the free radical during metabolism. These free radicals and hydrogen peroxide are constantly generated in the human and animal bodies and removed by antioxidant defences. Excessive production of free radicals can result in tissue damage, which mainly involves generation of hydroxyl radical and other oxidants in the presence of iron. The brain tissue contains large amount of unsaturated fatty acids and catecholamines, which are thought to be target molecules for free radical-induced peroxidation and neural cell damage, and such free radical-induced cell damage appears to play a major role in the pathogenesis of many neurological diseases.