Ultrastructural changes of synapses in the hippocampal CA1 region visualized by transmission electron microscopy. The animals were killed at 6 hours post-MV. Six-hour exposure to mechanical ventilation (MV) aggravated impairment in the synaptic ultrastructure at 6 hours post-MV. (A) Control group (C). (B) Surgical group (S) at 6 hours (S6h). (C) MV group at 3 hours (MV3h). (D) MV group at 6 hours (MV6h). Arrows point to synaptic cleft; arrowheads point to postsynaptic density. Ultrastructural changes of the mitochondrion and endoplasmic reticulum were visualized under transmission electron microscopy. The degree of rough endoplasmic reticulum degranulation in the hippocampus was more severe in the MV6h group (G) and (H) compared with the MV3h group (E) and (F). Scale bar =500 nm. Quantitation of the data is presented for (I) width of synaptic cleft, (J) area of postsynaptic density (PSD) and (K) number of vesicles. Data for each group in (J) are summarized by a box chart, in which the horizontal lines denote the 25th, 50th and 75th percentile values and the error bars denote the 5th and 95th percentile values. *P <0.05, compared with group S; †
P <0.05, compared with group C.