radioprotective effect of melatonin on the cervical spinal cord in irradiated rats

objective: it has been suggested that the vascular endothelial growth factor (vegf) gene expression plays an important role in radiation-induced injury to the spinal cord. this study assesses the radioprotective effects of n-acetyl-5-methoxytryptamine (melatonin) through its modulation of vegf expression after localized irradiation of the cervical spinal cord. materials and methods: in this experimental study, we divided 192 male rats into four groups: 1. control (n=48); 2. rats that received an intraperitoneal (ip) injection of melatonin (n=48); 3. rats that received an ip injection of melatonin 30 minutes prior to cervical spinal cord gamma irradiation [dose: 22 gy; (n=48)]; and 4. rats that received an ip injection of vehicle prior to spinal cord irradiation (n=48). the changes in vegf expression were assessed using real-time rt-pcr and enzyme-linked immunosorbent assays. samples for light microscopy were stained with hematoxylin and eosin (h&e;). the differences among the groups were analyzed using the analysis of variance (anova) test followed by tukey’s multiple comparisons test. results: up-regulation of vegf expression was observed from 8 to 22 weeks after irradiation (p<0.05). paralysis and other radiation-induced myelopathy manifestations developed within 22 weeks after irradiation. vegf expression in the melatonin pre-treatment group significantly down-regulated in the 20th and 22nd weeks after irradiation compared to the radiation-only group. conclusion: the results support the hypothesis that modulation of vegf expression by melatonin administration may increase the survival rate of irradiated animals.