Figure 2

Microglial activation coincides with selective neuronal vulnerability towards excitotoxicity. Confocal images of microglia in control (A-D), 10 μM (E-H) and 15 μM (I-L) NMDA-treated slice cultures, as determined by Iba1-immuno-histochemistry. After 6 days in culture (A), microglia were evenly distributed throughout the slice cultures and displayed a typical ramified morphology (B:CA1, C:CA3, D:DG). At 10 μM NMDA (E), changes in the CA1 region were clearly visible as numerous microglia accumulated at the site of injury (E, arrow). Morphologically, these microglia displayed an "activated" phenotype (F, CA1) with enlarged somata and loss of secondary and tertiary branching. In contrast, accumulation of microglia did not occur in the CA3 (G) and DG (H) and these cells retained their ramified phenotype. At 15 μM NMDA, pronounced accumulation of morphologically activated microglia (I, arrows) was observed in both CA1 (J) and CA3 (K). In contrast, microglia in the DG (L) showed only mild activation and accumulation of microglia was minimal in this region. Scale bars indicate 300 μM (overviews) and 25 μM (magnifications). Confocal images were gray-scaled and inversed.