Effect of emulsified isoflurane preconditioning on focal cerebral ischemia-reperfusion injury in rats

Objective To investigate the effect of emulsified isoflurane preconditioning on focal cerebral ischemia-reperfusion (I/R) injury in rats and the mechanism. Methods Fifty-six healthy male adult SD rats weighing 250-280 g were randomly divided into 4 groups (n = 14): group Ⅰ sham operation (group S); group Ⅱfocal cerebral I/R; group Ⅲ emulsified isoflurane preconditioning and group Ⅳ fat emulsion preconditioning. Focal cerebral ischemia was induced by middle cerebral artery occlusion (MCAO) using a nylon thread with rounded tip inserted into internal carotid artery and advanced cranially until resistance was met. MCAO was maintained for 2 h followed by 24 h reperfusion. In group Ⅲ and Ⅳ 8% emulsified isoflurane 7.5 ml/kg and 3% fat emulsion 7.5 ml/kg were injected intraperitoneally at 24 h before MCAO respectively. Neurologic outcome was evaluated at 24 h of reperfusion and scored (0 = no deficit, 4 = unable to crawl, loss of consciousness). The animals were then killed and brains removed. The infarct size was assessed. The apoptotic cells were detected by TUNEL and calculated. The expression of Bax, Bcl-2, cytochrome C and caspase-3 protein was detected by immunohistochemical staining. Results The neurologic deficit scores were significantly lower in emulsified isoflurane preconditioning group than in I/R group. Preconditioning with emulsified isoflurane significantly decreased the infarct size and the number of apoptotic cells and increased the expression of Bcl-2 protein and inhibited the expression of Bax, cytochrome C and caspace-3 protein. Conclusion Emulsified iscflurane preconditioning can protect the brain from focal cerebral I/R by increasing Bcl-2 protein expression and decreasing Bax protein expression, and reducing cytochrome C release from mitochondria, caspase-3 activation and neuronal apoptosis. Key words: Isoflurane;  Fat emulsions, intravenous;  Ischemic preconditioning;  Reperfusion injury; Brain