Effects of dexmedetomidine on global cerebral ischemia-reperfusion injury in rats

Objective To investigate the effects of dexmedetomidine on global cerebral ischemia-reperfusion (I/R) injury in rats.Methods Fifty-four adult male SD rats weighing 200-250 g were randomly divided into 3 groups (n =18 each): shame operation group (group S),global cerebral I/R group (group I/R) and dexmedetomidine group (group D).Global cerebral I/R was produced by occlusion of bilateral common carotid arteries combined with hypotension (MAP maintained at 35-45 mm Hg).In group D dexmedetomidine 3 μg/kg was injected iv immediately after I/R,followed by infusion of dexmedetomidine at a rate of 3 μg· kg- 1 · h- 1 until 2 h of reperfusion.The neurological deficit score (NDS) was assessed (0 =normal,100 =brain death) at 6 h (T1),24 h (T2)and 72 h (T3) of reperfusion.Then six rats were sacrificed in each group and brain tissues were removed for microscopic examination of hippocampus CA1 region and determination of activity of myeloperoxidase (MPO),contents of TNF-α and IL-1β and expression of glial fibrillary acidic protein ( GFAP).Results Compared with group S,NDS,MPO activity and the contents of TNF-α and IL-1β at T1-3 were significantly increased,the expression of GFAP was up-regulated at T2,3 in groups I/R and D ( P ＜ 0.05 or 0.01).Compared with group I/R,NDS,MPO activity and TNF-α concent were significantly decreased at T1-3,IL-1β concent was decreased at T1,2,the expression of GFAP was down-regulated at T2,3 in group D (P ＜ 0.05 or 0.01 ).The pathologic changes were significantly attenuated in group D as compared with group I/R.Conclusion Dexmedetomidine can attenuate global cerebral I/R injury in rats,and the inhibition of inflammatory response may be involved in the mechanism. Key words: Dexmedetomidine;  Reperfusion injury;  Brain