Contextual fear conditioning responses after surgery followed by mechanical ventilation. In the surgery group (S), surgery consisted of an open tibial fracture with intramedullary fixation in aseptic conditions under general anesthesia with isoflurane and buprenorphine, and then mice were placed in the anesthesia chamber with isoflurane for 1 hour, 3 hours or 6 hours. In the mechanical ventilation (MV) group, after the same surgery, isoflurane was administered to maintain anesthetic level during MV for 1 hour, 3-hour and 6-hour procedures. (A) Freezing time of C1h and S1h subgroups. (B) Percentage freezing time in the 6-hour groups. (C) Percentage freezing time on day 1. (D) Percentage freezing time on day 3. n =12/group. Values are mean ± standard error of the mean. *P <0.05 indicates significant differences.