Oxygen free radicals and brain dysfunction.

Oxygen free radicals, any chemical moiety containing an oxygen atom with an unpaired electron in the outer orbital shell, are generated during many normal biochemical reactions in living tissue. The unpaired electron makes these compounds highly reactive and they can initiate disruptive peroxidation reactions with various substrates important to the survival of cells such as proteins, lipids and nucleic acids. A fairly complex defense system has evolved to protect living tissue from free radicals and to minimize the damage they might cause. Neurons are especially vulnerable to free radical attack and impaired defenses or exposure to excess free radicals can lead to neuronal death. Free radicals contribute to neuronal loss in cerebral ischemia and hemorrhage and may be involved in the degeneration of neurons in epilepsy, schizophrenia, tardive dyskinesia, normal aging, Parkinson's Disease and Alzheimer's Disease. The development of drugs that limit or prevent the attack of free radicals on neurons would be an important advance in the treatment of these conditions.