RESUMEN
The purpose of this study, the effects on the cerebral cortex of the rats after brain irradiation was to investigate the change of distribution and morphology of neuropeptide-Y (NPY) neurons. Radiation was produced by the linear accelerator 6MV X-ray. The animals were categorized into control and experimental groups and we use 45 Sprague-Dawley rats weighing about 200 ~250 gm. The head areas of the animals were positioned within the radiation field of 15 cmx20 cm and with the radiation depth of 2 cm. Sodium chloral hydrate-anesthetized rats were exposed to the radiation with the dose rate of 240 cGy/min. The total dose was 1,800 cGy(rad). Animals were sacrificed on 2 hours, 5 hours, 1 day, 2 days, 3 days, 1 week, weeks, 3 weeks after brain irradiation. Using ABC immunohistochemistry, morphology and distribution of neuropeptide-Y immunoreactive neurons (NPY-IR)were studied on the cerebral cortex of the control and brain-irradiated rats. We used light and confocal laser scanning microscopy (CLSM). The following results were obtained : 1. On control group, NPY-IR neurons were found in all layers of the primary motor and sensory cerebral cortex, and the NPY-IR neurons were concentrated within the layer II, III, IV, V and VI. The typical NPY-IR perikarya was bipolar and multipolar shape. 2. On 2 hours, 5 hours after X-irradiation, decreased number of NPY-IR neurons were detected in the primary motor and sensory cerebral cortex of the rats. Also shrunken and transformed NPY-IR neurons were detected in the primary motor and sensory cerebral cortex of the rats. 3. On 1 day, 2 days, 3 days after X-irradiation, morphology and distribution of NPY-IR neurons in the primary motor and sensory cerebral cortex was generally restored. 4. On 1 week, 2 weeks, 3 weeks after X-irradiation, morphology and distribution of NPY-IR neurons in the primary motor and sensory cerebral cortex was almost similar to control group. 5. In optical serial section analysis of NPY-IR neurons, high intensity of immunofluorescence were observed in a part of the 8 ~11 sections of the control and all irradiated groups. In optical single section analysis of NPY-IR neurons, red color (high fluorescence intensity) were observed in a part of 6, 7 sections of the control and all irradiated groups. From the above results, it was concluded that the release of neurotransmitters and transcapillary leakage of blood substance were occurred on 2 hours, 5 hours, 1 day after X-irradiation, but the condition was generally restored on 3 days and 7 days following X-irradiation.