The Neuroprotective Effect Of Dexmedetomidine In Rats Following TBI

Objective:To observe the effect of dexmedetomidine on neuron specific enolase, content of water in brain tissue, and changes on TNF-a and IL-6 in serum after TBI in rats, and to explore its neuroprotective effect and mechanism.Methods:Sixty male Sprague-Dawley (SD) rats were randomly divided into four groups, six in normal control group (C),eighteen in each sham operation group (SHAM), traumatic brain injury group (TBI) and dexmedetomidine treatment group (DEX). Parietal brain contusion, according to Feeney's trial, was established by a free-falling weight on the exposed dura of the left parietal lobe.The DEX group were injected with dexmedetomidine injection transperitoneally by 3μg.kg-1 for three times,that is,at the onset of injury,two hours and four hours after injury. The C, SHAM and TBI groups were given the equal volume of normal saline in the same way.And the SHAM group were only exposed the skull with the dural undamaged. Each group, except the C group,was further randomly divided into 3 subgroups (n=6 for each subgroup). Each subgroup was killed at the time of 6,24, and 72 hours after injury respectively. The PaO2, PaCO2 and PH values were detected by arterial blood gas analysis, the brain water content was measured by dry-wet weight method, the brain histopathological examination was done by HE staining, and the NSE content in brain tissue, serum concentrations of TNF-a and IL-6 were detected by ELISA.Results:1.Arterial blood gas for PaO2, PaCO2 and PH values:The PaO2 value was lower in the TBI and DEX groups than SHAM group at 6,24,72h posttrauma (P<0.05), but no significant difference was found between the TBI and DEX groups. The PaCO2 value did not differ significantly among the four groups at any point during experimental period. The arterial PH value was significantly reduced in TBI and DEX groups, compared with the SHAM group at 6,24,72h posttrauma (P<0.05). The arterial PH value in DEX group was significantly higher than that of TBI group at 24,72h posttrauma (P<0.05).2.The content of water in injuried brain tissue:The water content of brain tissue in TBI and DEX groups was significantly higher than SHAM group at 6,24,72h posttrauma (P<0.05), but it was significantly lower in DEX group than that in TBI group at 24,72h posttrauma (P<0.05).3.The NSE lever in injuried brain tissue:The NSE lever of brain tissue in TBI and DEX groups was significantly higher than that in SHAM group at 6,24,72h posttrauma (P<0.05), but it was significantly lower in DEX group than that in TBI group at 6,24,72h posttrauma respectively (P<0.05).4.The serum TNF-a and IL-6 lever:The serum TNF-a and IL-6 lever in TBI and DEX groups were significantly higher than SHAM group at 6,24,72h posttrauma (P<0.05).To compare with the TBI Group, the serum TNF-a level in the DEX group was significantly decreased respectively at the time 6,24, and 72 hours after injury (P<0.05); and the serum IL-6 concentration in the DEX group was significantly decreased at the time 6 and 72 hours after injury (P<0.05).Conclution:The model of severe traumatic brain injury in rats is successfully reproduced with good stability. Dexmedetomidine can decreace NSE, the water content of brain tissue after TBI, which shows neuroprotective effect. Dexmedetomidine can decreace the serum TNF-a and IL-6 lever posttrauma, which may be part of the neuroprotective mechanism at an early phase following TBI.