The effects of dexmedetomidine on postoperative cognitive dysfunction in rats with bone fractures undergoing open reduction

Abstract

Objective: To investigate the effects of dexmedetomidine on the cognitive dysfunction of aged rats after open tibia fracture surgery and the expression of inflammatory cytokines in the hippocampus.

Methods: A total of 45 aged healthy male Sprague Dawley rats were divided into control group, sham group, and dexmedetomidine group. The open tibia fracture surgery rat model was established, and dexmedetomidine was intraperitoneally injected before operation. The cognitive function of aged rats was examined by Morris Water-Maze Test, open field experiment, and passive avoidance memory test. The expression levels of IL-6, IL-1β, and TNF-α in the hippocampus were examined by enzyme-linked immunosorbent assay (ELISA).

Results: The escape latency over 5 continuous days in the dexmedetomidine group was significantly shorter than that in the control group (all P<0.05). The number of swimming times and the percentage of swimming time in the dexmedetomidine group were significantly higher and longer than those in the control group (all P<0.05). Moreover, rats in the dexmedetomidine group exhibited shorter time of stay at the central square and higher number of standing times in comparison with the control group (all P<0.05). Compared with the control group, dexmedetomidine intraperitoneally injected before surgery significantly inhibited the expression levels of IL-6, IL-1β, and TNF-α in the hippocampus (all P<0.05).

Conclusion: Dexmedetomidine could significantly relieve the postoperative cognitive dysfunction in aged rats. The mechanism may be associated with the decreased inflammatory cytokines in the hippocampus.

Keywords: Dexmedetomidine; inflammatory cytokine; mechanism; open tibia fracture surgery; postoperative cognitive dysfunction.

Figure 1

Results of the rotarod test and Morris water maze test. A: The rod velocity in the Rotarod Test. B: The time to fall in the Rotarod Test. C: The movement route in the Morris Water Maze Test. The swimming speed of rats from the control group, the sham group and the dexmedetomidine group were 32 cm/s, 30 cm/s, and 31 cm/s, respectively.

Figure 2

Comparison of the open field test results among three groups. A: The time of stay at the central square; B: The number of standing times. Note: Compared with the control group, *P<0.05, Compared with the control group or the sham group, #P<0.05.

Figure 3

Comparison of passive avoidance memory test results among three groups. A: The latency of the initiative avoiding; B: The latency of the passive avoiding; C: The times of avoiding; Note: Compared with the control group, *P<0.05, Compared with the sham group or the control group, #P<0.05.

Figure 4

Comparison of inflammatory cytokines among the three groups. A: The level of IL-6; B: The level of IL-1β; C: The level of TNF-α; Note: Compared with the control group, *P<0.05, Compared with the sham group or the control group, #P<0.05.