Melatonin maintains adult hippocampal neurogenesis and cognitive functions after irradiation.

Cognitive health of an organism is considered to be maintained by the capacity of hippocampal precursors to proliferate and differentiate. Environmental stressors including irradiation have been shown to inhibit neurogenesis and are associated with the onset of cognitive impairments. Over the last two decades, much evidence has been gathered showing that enhanced free radical levels and an impaired antioxidant pool are important factors underlying the pathophysiological mechanisms in a variety of neurocognitive and neurodegenerative ailments. Since oxidative stress is reported to be implicated in impaired neurogenesis, it is likely that antioxidants such as melatonin and its metabolites could restore or minimize cellular death in the hippocampal dentate gyrus. The present review summarizes the recent studies documenting the protective role of melatonin against radiation-induced impairment of neurogenesis and cognitive functions. Copyright 2009 Elsevier Ltd. All rights reserved.