Objective To investigate the effect of isoflurane preconditioning on Toll-like receptor 4 (TLR4)-myeloid differentiation factor 88 (MyD88) signaling pathway in ischemic penumbra following focal cerebral ischemia-reperfusion (I/R) in rats.Methods Fifty-four healthy male SD rats,aged 3 months,weighing 250-280 g,were randomly divided into 3 groups (n =18 each):sham operation group (group S),I/R group and isoflurane preconditioning group (group IP).Focal cerebral I/R was induced by middle cerebral artery occlusion.In groups I/R and IP,a nylon thread with rounded tip was inserted into the right internal jugular vein and threaded cranially until resistance was met.The middle cerebral artery was occluded for 2 h,followed by 24 h reperfusion.In group IP,the animals inhaled 2.0％ isoflurane for 2 h,and middle cerebral artery occlusion was performed at 24 h after the end of preconditioning.Neurological deficit was scored at 24 h of reperfusion and then the rats were sacrificed.Five rats in each group were chosen and the brains removed for measurement of the cerebral infarct volume.The right cerebral ischemic penumbra was removed for detection of the expression of HSP60,TLR4,MyD88 protein and mRNA by Western blot analysis and real time-PCR.Apoptosis was detected in the ischemic penumbra in the left 3 rats in each group using TUNEL.Apoptosis index (AI) was calculated.Results Neurological deficit scores and AI were significantly increased,the cerebral infarct volume was significantly enlarged,and the expression of HSP60,TLR4,MyD88 protein and mRNA was up-regulated in groups I/R and IP as compared with group S ( P ＜ 0.05).Isoflurane preconditioning significantly reduced the cerebral infarct volume and decreased neurological deficit scores and AI,and down-regulated the expression of HSP60,TLR4,MyD88 protein and mRNA (P ＜ 0.05).Conclusion The mechanisn by which isoflurane preconditioning protects ischenic penumbra following focal cerebral I/R may be related to inhibition of TLR4-MyD88 signaling pathway.

Objective To investigate the effect of isoflurane preconditioning on the expression of 5-lipoxy-genase (5-LOX) during focal cerebral ischemia-reperfusion (I/R) in rats.Methods Thirty-nine male adult Sprague-Dawley rats weighing 250-300 g were randomly divided into 3 groups (n =13 each):sham operation group (group S); focal cerebral I/R group (group I/R); isoflurane preconditioning group (group Ⅰ).Focal cerebral I/R was produced by mid-cerebral artery occlusion in anesthetized rats.The rats inhaled 2 h of 2％ isoflurane and focal cerebral I/R was produced 24 h later in group I.The neurological deficits were scored at 24 h of reperfusion.The animals were then sacrificed.The brains were immediately removed for determination of the infarct size.The expression of 5-LOX,myeloid differentiation factor88 (MyD88) and nuclear factor kappa B (NF-κB) protein and mRNA was detected using Western blot and RT-PCR respectively.Results Compared with group S,the neurological deficit score was significantly increased,the infarct size was enlarged in groups I/R and I,the expression of 5-LOX,MyD88 and NF-κB protein and mRNA was up-regulated in group I/R,and the expression of 5-LOX mRNA and MyD88 protein and mRNA was up-regulated in group I (P ＜ 0.05).Compared with group I/R,the neurological deficit score was significantly lower,the infarct size was smaller,and the expression of 5-LOX,MyD88 and NF-κB protein and mRNA was lower in group I (P ＜ 0.05).Conclusion Isoflurane preconditioning can reduce focal cerebral I/R injury by down-regulating the expression of 5-LOX and inhibiting MyD88/NF-κB signaling pathway in rats.

Objective To evaluate the role of δ opioid receptor in the brain injury following asphyxial cardiac arrest-resuscitation in rats.Methods Ninety-six pathogen-free male Sprague-Dawley rats,weighing 300-350 g,were randomly divided into 4 groups (n =24 each):sham operation group (group S),asphyxial cardiac arrest-resuscitation group (group M),δ opioid receptor agonist BW373U86 group (group B) and δ opioid receptor antagonist naltrindole group (group N).Cardiac arrest was induced by clamping the tracheal tube for 8 min.Mechanical ventilation with pure oxygen was performed.Epinephrine 0.02 mg/kg and 5％ NaHCO3 1 mg/kg were injected intravenously as soon as chest compression was started.Appearance of spontaneous breathing and MAP ＞ 50 mm Hg (lasting for more than 10 min) were considered to be signs of successful recovery of spontaneous circulation (ROSC).BW373U86 and naltrindole 1 mg/kg were injected via the femoral vein immediately after ROSC in groups B and N,respectively,while the equal volume of normal saline was given instead in groups S and M.Neurological deficit score (NDS) was evaluated at 3,24 and 72 h after ROSC.The rats were then sacrificed,brains were isolated and the hippocampus was obtained for detection of the expression of brain-derived neurotrophic factor (BDNF)and tyrosine receptor kinase B (TrkB)mRNA by RT-PCR.The histological grading (HG) of neurons and number of survival neurons in hippocampal CA1 region were determined at 72 h after ROSC.Results Compared with group S,the expression of BDNF and TrkB mRNA was significantly up-regulated,HG was increased,and NDS and the number of survival neurons were decreased in groups M,B and N (P ＜ 0.05).Compared with group M,the expression of BDNF and TrkB mRNA was significantly up-regulated in group B,the expression of BDNF and TrkB mRNA was down-regulated in group N,and HG was significantly decreased,and NDS and the number of survival neurons were increased in groups B and N (P ＜ 0.05).NDS was significantly lower,the number of survival neurons was smaller,the expression of BDNF and TrkB mRNA was lower,and HG was higher in group N than in group B (P ＜ 0.05).Conclusion Activation of δ opioid receptor can reduce the brain injury following asphyxial cardiac arrest-resuscitation in rats and the mechanism may be related to up-regulation of BDNF and TrkB after activation of δ opioid receptor.