Effects of dexmedetomidine on expression of nNOS and c-fos in lcuos cruleus in a rat model of endotoxic shock

Objective To evaluate the effects of dexmedetomidine on the expression of neuronal nitric oxide synthase (nNOS) and c-fos in the lcuos cruleus (LC) in a rat model of endotoxic shock.Methods Twentyeight male Sprague-Dawley rats,aged 8 weeks,weighing 250-300 g,were randomly divided into 4 groups (n =7 each):control group (group C),endotoxic shock induced by lipopolysaccharide (LPS) group (group L),lowdose dexmedetomidine group (groupLD) and high-dose dexmedetomidine group (group HD).Normal saline 0.5 ml/kg was injected via the tail vein in C and L groups.Dexmedetomidine 0.5 and 4.5μg/kg were injected via the tail vein in group LD and group HD,respectively.Normal saline 0.5 ml/kg was injected via the tail vein 10 min later in C,while LPS 5 mg/kg was injected intravenously 10 min later in the other groups.The rats were sacrificed and their brains were removed for determination of brain water content,the number of nNOS and c-fos positive cells and expression of nNOS and c-fos in the LC by immuno-histochemistry.Results Compared with group C,the brain water content was significantly increased,the number of nNOS and c-fos positive cells in the LC was enlarged,and the expression of nNOS and c-fos in the LC was up-regulated in group L (P ＜ 0.05).The brain water content was significantly lower,the number of nNOS and c-fos positive cells in the LC was smaller,and the expression of nNOS and c-fos in the LC was lower in LD and HD groups than in group L (P ＜ 0.05).The number of nNOS and c-fos positive cells in the LC was significantly smaller,and the expression of nNOS and c-fos in the LC was lower in HD group than in group LD (P ＜ 0.05).Conclusion Dexmedetomidine can down-regulate the expression of nNOS and c-fos in the LC,which may be one of brain-protective mechanisms of dexmedetomidine in a rat model of endotoxic shock. Key words: Dexmedetomidine;  Shock, septic;  Nitric oxide synthase type Ⅰ ;  Proto-oncogene proteins c-fos