Effects Of Remifentanil Preconditioning On Learning And Memory In Rats With Transient Cerebral Ischemia

Objective To investigate the effects of remifentanil preconditioning on learning and memory in rats after transient cerebral ischemia and evaluate its mechanism..Methods Forty male SD rats were randomly divided into 5 groups:sham group, model group, remifentanil preconditioning(RPC)group with the dose of 0.2μg·kg-1·min-1 (RPC1 subgroup), 0.6μg·kg-1·min-1 (RPC2 subgroup) or 2.0μg·kg-1·min-1 (RPC3 subgroup) respectively. Global cerebral ischemia was induced by bilateral common occlusion for 8min and blood withdraw to lower the mean arterial blood pressure to 30～35 mmHg, according to the previously described Smith's with some modifications. Rats were received preconditioning by NS, remifentanil 0.2,0.6 or 2.0μg·kg-1·min-1 intravenous infusion before global cerebral ischemia.The ischemic time was maintained 8min. Remifentanil was pumped via tail vein for 3 episodes of 5 min at 5 min interval. After 30 min of the preconditioning, the 2VO+H ischemia model was finished. The rats' learning and memory were tested by Morris water maze respectively. All rats were tested with Morris water maze from the third day of reperfusion, then the brains were removed for determination of the expression of ChAT. The epression of ChAT in the hippocampus was determined by immunohistochemistry. All data were expressed as mean±SD and data analysis was performed with SPSS 11.0, a statistical software. Data of different groups were analyzed using one-way analysis of variance(ANOVN) with Newman-Keuls test for multiple comparisons. Statistical differences were considered significant if the P value was<0.05. Results Compared with model group, the latency period in mid dosage group, high dosage group and sham group were significantly reduced (P<0.05) since the third day, and the number of times straddling the origin platform and time percentage of straddling the origin platform quadrant in mid dosage group, high dosage group and sham group were significantly increased [(38.0±5.1)%, (39.9±4.6)% vs. (29.4±5.6)%, P<0.05]. Immunohistochemical results showed that the levels of ChAT protein expression were significantly different among groups. Compared with model group, the expression of ChAT in mid dosage group, high dosage group and sham group were significantly increased (0.51±0.19,0.53±0.2,0.6±0.22vs.0.35±0.13, P<0.05).Conclusion Preconditioning with Mid dosage and high dosage remifentanil was obviously ameliorataed the ability of spatial learning and memory. The mechanism of its protective effect against global cerebral ischemia-reperfusion injury in rats may be via up-regulating the expression of ChAT in CA1...