Fig. 11

Structural change of mitochondria in three experimental systems under different conditions. In hippocampal slice cultures, mitochondria in control samples could appear swollen (a) or not (b) while those in NMDA-treated samples were consistently swollen (c). In dissociated hippocampal cell cultures, 55–90% of neurons contained swollen mitochondria in control samples (d). Upon 2–3 min depolarization with high K⁺, 87–100% neurons contain swollen mitochondria (e). When EGTA, a calcium chelator, is included in the high K⁺ medium, mitochondria were not swollen (f). When dissociated cell cultures were incubated for 1 h with or without TTX, 50–67% of neurons contained swollen mitochondria in control samples (g) while the great majority (more than 90%) of mitochondria in TTX-treated samples were not swollen (h). Washing control samples with EGTA for 2 min also prevented mitochondria from swelling (i). In perfusion-fixed mouse brains, the great majority of mitochondria in fast perfusion-fixed brains were not swollen (j), while some swollen mitochondria were seen in delayed perfusion-fixed brains (k). However, many mitochondria in delayed-fixed brains were not swollen (l), and co-existed with CaMKII clusters (large arrow in l) and ER cisternal stacks (small arrows in l), two structural benchmarks indicating that this neuron was under hypoxic excitatory stress. Scale bar = 0.5 μm