Fig. 3

Chromatin in neurons aggregates into dark clusters upon depolarization. Electron micrographs of neuronal nuclei from CA1 region of the hippocampus in slice cultures under different experimental conditions. (left column) – Chromatin appeared non-clustered under control conditions (a), but became aggregated into dark clusters (arrows) at 30 s after depolarization with high K⁺ (90 mM, d), and progressed into even more pronounced clustering after 2 min of treatment (g). (middle column) – In a second series of experiments, the chromatin was again non-clustered under control conditions (b), became extensively clustered upon 3 min of depolarization with high K⁺ (e), and reverted to the non-clustered appearance upon washout of the high K⁺ medium and returning the samples to control medium for 1 h (h). (right column) – In contrast, nucleoplasm of fibrous astrocytes had a thin but dense rim of dark material of irregular thickness around the edge of the nucleus, and this configuration was not affected by high K⁺ (c, f, i). Scale bar = 0.5 μm