Melatonin mitigates hippocampal and cognitive impairments caused by prenatal irradiation

다국어 초록 (Multilingual Abstract)

Formation of new neurons and glial cells in the brain is taking place in mammals not only during prenatal embryogenesis but also during adult life. As an enhancer of oxidative stress, ionizing radiation represents a potent inhibitor of neurogenesis and gliogenesis in the brain. It is known that the pineal hormone melatonin is a potent free radical scavenger and counteracts inflammation and apoptosis in brain injuries. The aim of our study was to establish the effects of melatonin on cells in the hippocampus and selected forms of behaviour in prenatally irradiated rats. The male progeny of irradiated (1 Gy of gamma rays; n = 38) and sham‐irradiated mothers (n = 19), aged 3 weeks or 2 months, were used in the experiment. Melatonin was administered daily in drinking water (4 mg/kg b. w.) to a subset of animals from each age group. Prenatal irradiation markedly suppressed proliferative activity in the dentate gyrus in both age groups. Melatonin significantly increased the number of proliferative BrdU‐positive cells in hilus of young irradiated animals, and the number of mature NeuN‐positive neurons in hilus and granular cell layer of the dentate gyrus in these rats and in CA1 region of adult irradiated rats. Moreover, melatonin significantly improved the spatial memory impaired by irradiation, assessed in Morris water maze. A significant correlation between the number of proliferative cells and cognitive performances was found, too. Our study indicates that melatonin may decrease the loss of hippocampal neurons in the CA1 region and improve cognitive abilities after irradiation.
Prenatal irradiation decreased proliferative activity in hippocampal neurogenic region and decreased the number of hippocampal neurons that was associated with cognitive impairment. Melatonin may decrease the loss of hippocampal neurons in the CA1 region and improve cognitive abilities after irradiation. Significant relationship was revealed between the spatial memory and the number of BrdU+ (hilus, SGZ) and NeuN+ (hilus, CA1) cells.