ABSTRACT
Neurons are postmitotic and do not divide once the brain has reached maturity. Although neurons do have substantial ability to form new processes and terminals in response to growth factors, synaptic activity, and injury, they cannot replace themselves in the same manner as do skin, liver, and intestinal cells. The notion that toxic substances can cause selective damage to certain subsets of brain neurons has been clearly verified in acute animal models of substantia nigra, striatal, cerebellar, and hippocampal damage. 6-Hydroxy-dopamine is selectively accumulated in dopamine neurons where it causes free radical formation and irreversible neuronal damage. In mammalian brain, additional naturally occurring compounds have been identified that cause neuronal damage. A popular theory in cardiac disease, brain disease, and cancer is that any mechanism that leads to free radical accumulation will likely contribute to the cause of certain forms of pathology in these organ systems.
