Hyperacute Radiation Effect on Cerebral Cortex after Local Gamma-irradiation in the Rat Brain

ABSTRACT

OBJECTIVE: We investigated the morphologic changes within 24 hours after a single gamma-irradiation in the rat brain. METHODS: Forty Sprague-Dawley rats were used. After a burr hole trephination on right parietal area, cerebral hemisphere was irradiated with 2Gy and 5Gy using iridium-192(192Ir), respectively. The effect was assessed at 4, 8, 12 and 24 hours after irradiation. The histological changes were scored following the detection of edema or disarray severity. TUNEL-positive cells exhibiting apoptotic morphology were counted in irradiated region. RESULTS: Cortical edema and disarray were initially showed at 4 or 8hour and almost all defined at 24hour after irradiation. And the injury was wedge shape. TUNEL-positive cells were minimal at 8hour after irradiation as the number of positive cells were 2.6+/-5.27(n=5) after 2Gy, and 0.8+/-0.84(n=5) after 5Gy. But, the number of apoptotic cells were increased markedly to 60+/-6.24 at 12hour after 2Gy and to 104+/-19.7 at 24hour after 5Gy. CONCLUSION: There were prominent morphologic changes immediately after gamma-irradiation. And, apoptosis was increased according to the time period. These findings implicate that brain irradiation induces rapid apoptotic change, which may play an important role in the pathogenesis of radiation-induced pathologic conditions.