砂ネズミ前脳虚血モデルにおける海馬CA1 sector星状膠細胞の経時的超微細構造変化

Abstract

Transient forebrain ischemia in gerbils was produced by a 5-minute occlusion of the bilateral carotid arteries. This model produces selective delayed neuronal death (SDND) in the hippocampus CA1 sector with high reproducibility. Changes in the hippocampal and cortical astrocytes and neurons at 1, 2, 3, 6, 12, 24, 48, 96 hours after ischemia were evaluated by electron microscopy, and quantitative estimations of increases in cytoplasmic area and the number of mitochondrial profile were performed. In areas of the hippocampus with SDND, cytoplasm-soma ratio increased 32.8% in control to 49.1% at 1 hour after ischemia (p＜0.01) and 42.2% at 96 hours (p＜0.05). The number of mitochondrial profiles in astrocytic perikarya rose significantly at 48 hours (p＜0.05) and 96 hours (p＜0.01) postischemia. Paired nuclei which are regarded as a reactive change of astrocyte were observed at 12 hours postischemia. In the area of the parietal cortex, no significant morphological change was observed in either neurons or astrocytes. Even in the final evaluation (at 96 hours), neurons, astrocytes and the surrounding neuropils were morphologically intact. In the early phase (＜6 hours), the cytoplasmic swelling of astrocytes suggests the protective activity for hyperexciting neurons. But in the late phase (＞6 hours), the configurational change of the nucleus, paired nuclei and swelling of astrocytes suggest increased metabolic acivity in the renovation of brain tissue.