Objective To evaluate the effect of dexmedetomidine on apoptosis in myocardial cells in rats with severe scald.Methods Eighteen healthy male Sprague-Dawley rats,weighing 220-280 g,were randomly divided into 3 groups (n =6 each) using a random number table:control group (group C),scald group (group B)and scald + dexmedetomidine 30 μg/kg group (group D).Thirty percent of the total body surface was shaved and then exposed to 94 ℃ water for 12 s.Rats were resuscitated with isotonic saline according to Parkland formula immediately after burn.Sham burn was produced in C group.In group D,the rats received inraperitoneal injection of dexmedetomidine 30 μg/kg immediately after burn,and the equal volume of normal saline was injected in group B.The left ventricle was removed at 12 h after burn to observe the pathological changes of myocardial tissues with light microscope and to detect the apoptosis in myocardial cells (TUNEL assay) and expression of glucose-regulated protein 78 (GRP78) and C/EBP-homologous protein (CHOP) (using Western blot).The apoptosis index was calculated.Results Compared with group C,the apoptosis index was significantly increased and the expression of GRP78 and CHOP was up-regulated in B and D groups (P ＜ 0.05).Compared with group B,the apoptosis index was significantly decreased and the expression of GRP78 and CHOP was down-regulated in group D (P ＜ 0.05).The pathological changes were obvious in group B and were significantly attenuated in group D.Conclusion Dexmedetomidine can protect myocardium through inhibiting endoplasmic reticulum stress-mediated apoptosis in myocardial cells in rats with severe scald.