Mechanical ventilation induced significantly greater apoptosis in surgical mice. Six-hour exposure to mechanical ventilation (MV) induced upregulation of cytochrome c (Cytc), cleaved caspase-3 and cleaved poly(ADP-ribose) polymerase 1 (PARP-1) in the hippocampus after surgery (S). (A) Representative Western blot of Cytc, cleaved caspase-3 and cleaved PARP-1. (B, C and D) The results of semiquantitative analysis of the ratio of Cytc to β-actin (B), the ratio of cleaved caspase-3 to β-actin (C) and the ratio of cleaved PARP-1 to β-actin (D). All Western blot assay data are expressed as mean ± standard error of the mean. C, Control group. n =6/group. *P <0.05, compared with group S.