Effects of ionizing-radiation to the expressions of bFGF and BDNF and the protective and repaired functions of melatonin in the forebrain of rat

Objective: To investigate the expressions of bFGF and BDNF induced with ionizing-radiation and the effects of melatonin to the expressions of bFGF and BDNF in the rate cerebral cortex and subependymal ventrical zone (SVZ) and discuss the protective function and repaired mechanism of melatonin to brain during radiation nervous damage. Methods: 60 SD rats were used in this experiment, which were divided into three groups: blank control group, radiation control group, and treatment groups. Injections of melatonin were given into the abdomen of the rats in the treatment group in three doses of 1, 5 and 10 mg·kg-1 one time each day, in total of 10 days. Then, the radiation control and treatment groups were X-rayed a dose of 600 cGy. All of rat brains were cut up in coronal sections continuously, which were stained with bFGF and BDNF in immunohistochemical ABC method. The positive cells stained with bFGF and BDNF were observed and counted under the light microscope with computed program. Results: bFGF and BDNF are expressed weakly in cerebral cortex and subependymal ventrical zone of the normal rats. One day after radiation, the expressions of bFGF and BDNF are increasing, but weaking 5 days after radiation in cerebral cortex; then, one day after radiation, the expressions of bFGF and BDNF are less increasing, but more increasing 5 days after radiation in the subependymal ventrical zone cells. When the rats were treated by the melatonin in advance, the expressions of bFGF and BDNF are increasing continuously (more than 50%) and accompanying with the dose of melatonin. The cells of proliferation, differentiation, and migration can be observed in the subependymal ventrical zone (from 1-2 layers to 3-5 layers). Conclution: Radiation nervous damage can induce the expressions of bFGF and BDNF in the cerebral cortex and subependymal ventrical zone, which are more increasing when stimulated with melatonin. It is shown that melatonin has the functions to protect the cerebral cortex by the expressing of bFGF and BDNF and promote the proliferation, differentiation, and migration of cells in the subependymal ventrical zone. (authors)