Dexmedetomidine renders a brain protection on hippocampal formation through inhibition of nNOS-NO signalling in endotoxin-induced shock rats

Abstract

Background: Endotoxin shock (ES) and its severe complications, such as brain injury, remain a handicap clinically. Therefore, it is a clinical significance of developing a new drug to treat brain damage induced by ES.Aim: The present study aimed to observe the protective effect of dexmedetomidine (Dex) on hippocampal formation in endotoxin-induced shock rats and explore its possible mechanism.Methods: High and low doses of Dex were tail intravenously administered slowly. After a 5-minute interval, lipopolysaccharide was tail intravenous injected slowly to establish the ES rats. Six hours after Dex administration, these rats were immediately sacrificed. Then, the brain water content was determined. NO amounts in homogenate, cerebrospinal fluid and serum were detected by Griess Reagent assay. nNOS mRNA in hippocampal formation was measured by RT-PCR and nNOS protein was determined by Western blotting and immunohistochemistry.Results: ES rats showed that cerebral water contents were significantly increased, NO concentrations in brain tissues, serum and cerebrospinal fluid were each obviously raised and meanwhile expressions of nNOS mRNA and its protein in hippocampal formation were notably augmented. Treatment of these rats with Dex evidently decreased cerebral water contents, NO concentrations and nNOS mRNA and its protein expressions.Conclusion: These results demonstrated that Dex exerted a brain protection on hippocampal formation through inhibition of the nNOS-NO signalling in ES rats and Dex may have a favourably therapeutic value in treating brain damage in patients with endotoxin shock.