Role of Nitric Oxide Synthase, Superoxide Dismutase, and Glutathione Peroxidasein Radiation-Induced Decrease in Norepinephrine Release

摘要

Although the central nervous system (CNS) is considered to be relativelyresistant to the direct effects of ionizing radiation, the dose and the time elapsed after radiation exposure can have a complex effect on the CNS. The hippocampus is important in critical functions such as learning, memory, and motor performance, and these functions are impaired after exposure to ionizing radiation.' Noradrenergic systems are important in mediating arousal, food intake, and to some extent motor functions. Histofluorescence and immunohistochemical techniques have shown noradrenergic pathways in the hippocampus.2 Several factors can contribute to acute nervous system damage in vivo: (1) reduced systemic blood pressure following exposure to 25-100 Gy of gamma radiation,3-5 (2) decreased cerebral blood flow in various regions of the brain, including the hippocampus,3-5 (3) ischemia produced by the decreased blood flow, which is likely to affect neuronal activity;6 (4) free radical generation with resulting oxygen radicals implicated in cell damage following ischemia; (5) brain ischemia-induced release of an excessive amount of glutamate in the hippocampus, which acts on nitric oxide (NO) synthase to form NO through N-methvl-D-aspartate (NMDA) receptors, causing toxic effects. JMD.