Effects of dexmedetomidine preconditioning on cerebral hypoxia-ischemia injury in rats

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Objective To investigate the effects of dexmedetomidine preconditioning on cerebral hypoxia-ischemia injury in rats. Methods Seventy-two adult male Sprague-Dawley (SD) rats weighing 250-300 g were randomly divided into 3 groups: sham group (Group S), conventional resuscitation group (Group C) and dexmedetomidine preconditioning group (Group D). Cerebral hypoxia-ischemia injury rat model was produced by mechanical asphyxia. In Group D, 4 μ g/kg dexmedetomidine was injected intravenously 5 min before asphyxia. The Neurological Deficit Scale (NDS) was assessed at 12, 24, 48 and 72 h after return of spontaneous circulation. Six rats were sacrificed in each group and brain tissues were removed for microscopic examination of hippocampal CA1 region and ultrastructure by electron microscope. Results The PaO 2 in Group D and C rats was significantly lower after resuscitation ( P = 0.000, for all), while the PaCO 2 was increased as compared with before asphyxia ( P = 0.000, for all). Compared with Group S, NDS at each time point were significantly increased in Group C ( P = 0.000, for all). Compared with Group C, NDS were significantly decreased at 24, 48 and 72 h in Group D ( P = 0.000, for all). Compared with Group C, hippocampal neurons in Group D revealed alleviative necrosis, karyopyknosis and karyolysis, as well as increased number of survival neurons and relieved edema. Besides, there was good microenvironment of neurovascular unit and no obvious demyelination. Conclusions Dexmedetomidine preconditioning can attenuate cerebral hypoxia?ischemia injury in rats, and improve the pathologic changes and ultrastructure of neurons of hippocampus. doi: 10.3969/j.issn.1672-6731.2014.05.012