Effects of dexmedetomidine on expression of TNF-α and ICAM-1 during cerebral ischemia-reperfusion in rats

Objective To evaluate the effects of dexmedetomidine on the expression of tumor necrosis factor-α（TNF-α） and intercellular adhesion molecule-1 （ICAM-1 ） during cerebral ischemia-reperfusion （I/R ） in rats .Methods Thirty-six male Sprague-Dawley rats , aged 8-12 weeks ,weighing 280-320 g ,were randomly divided into 3 groups （ n= 12 each ）：sham operation group （group S ） , cerebral I/R group （group I/R ） and dexmedetomidine group （group D ） .The animals were anesthetized with 10% chloral hydrate 3.5 ml/kg .The focal cerebral ischemia was induced by middle cerebral artery occlusion using a nylon thread with rounded tip inserted into internal carotid artery and advanced cranially until resistance was met .In group D ,dexmedetomidine 3μg/kg was injected intravenously immediately after beginning of ischemia ,followed by infusion at 3μg·kg-1 ·h-1 for 120 min ,while the equal volume of normal saline was given in group I/R .Four rats from each group were chosen at 24 ,48 and 72 h of reperfusion , and blood samples were taken from the left ventricle to determine the concentrations of serum S100B protein .The rats were then sacrificed and the brains were removed to determine the expression of TNF-αand ICAM-1 in brain tissues .Results Compared with group S ,the concentrations of serum S100B protein were significantly increased , and the expression of TNF-α and ICAM-1 in brain tissues was up-regulated in I/R and D groups （ P〈0.05） .Compared with group I/R ,the concentrations of serum S100B protein were significantly decreased , and the expression of TNF-α and ICAM-1 in brain tissues was down-regulated in group D （ P〈0.05 ） .Conclusion The mechanism by which dexmedetomidine reduces the cerebral I/R injury is related to down-regulation of TNF-αand ICAM-1 expression in rats . Key words: Dexmedetomidine; Brain; Reperfusion injury; Tumor necrosis factor-alpha; Intercellular adhesion molecule-1