目的 观察可卡因-苯丙胺调节转录肽(CART)对缺血-再灌注(I/R)小鼠皮质突触可塑性的影响.方法 选用10~12周龄的健康雄性清洁级昆明小鼠288只,按照随机数字表法完全随机分为I/R组(81只)、I/R+CART组(81只)和假手术组(63只)、假手术+CART组(63只).建立大脑中动脉阻塞(MCAO)2 h再灌注模型.I/R+CART组于再灌注前经尾静脉注射CART(0.5μg,200μl),假手术+CART组予以等剂量CART;每24小时重复给药1次.在实现再灌注后不同时间点(24 h、72 h和7 d)采用2,3,5-氯化三苯基四氮唑染色检测I/R组和I/R+CART组脑梗死体积;采用透射电镜观察各组不同时间点突触超微结构变化,并对突触形态学参数进行定量分析;采用Western Blot法观察再灌注72 h皮质梗死周围区突触后致密物95(PSD-95)蛋白表达水平.结果 (1)与假手术组比较,I/R组小鼠造模后24、72 h和7 d皮质切片中突触数量明显减少[(3.37±0.38)个/μm2比(7.04±0.55)个/μm2,(2.89±0.22)个/μm2比(6.89±0.04)个/μm2,(3.25±0.18)个/μm2比(6.78±0.42)个/μm2;均P<0.05],PSD密度明显下降[(24.4±2.8)nm比(47.3±6.1)nm,(23.8±3.7)nm比(46.5±7.5)nm,(24.6±2.2)nm比(48.1±5.1)nm;均P<0.05],突触间隙宽度增大[(25.2±2.1)nm比(21.5±1.6)nm,(25.2±1.4)nm比(21.3±1.0)nm,(23.7±2.6)nm比(21.6±1.6)nm;均P<0.05];再灌注后72 h时间点PSD-95蛋白表达水平下降(P<0.05);(2)与I/R组比较,I/R+CART组小鼠I/R后24、72 h和7 d脑梗死体积缩小[分别为(29.0±1.9)%比(36.3±1.4)%,(38.1±1.4)%比(47.6±2.7)%,(36.0±2.8)%比(42.5±2.0)%;均P<0.05];再灌注后72 h时间点突触数量[(4.32±0.35)个/μm2]明显增多(P<0.05),PSD-95蛋白表达水平增加(P<0.05);再灌注后24、72 h和7 d各时间点PSD密度[分别为(33.8±3.4)、(34.2±4.6)、(38.2±4.0)nm]增厚(均P<0.05);而各时间点突触间隙宽度差异无统计学意义(均P>0.05).结论 CART可缩小I/R小鼠脑梗死体积,改善缺血损伤后小鼠脑皮质神经细胞突触可塑性.%Objective To investigate the effect of cocaine and amphetamine-regulated transcript (CART ) peptides on cortical synaptic plasticity in ischemia-reperfusion (I/R ) injury mice. Methods A total of 288 healthy male specific pathogen free(SPF)grade Kunming mice aged 0 to 12 weeks were selected. They were divided into four groups:I/R group (n =81 ),I/R +CART group (n =81),sham operation group (n=63),and sham operation+CART group (n=63)according to the random number table method. A model of middle cerebral artery occlusion (MCAO)for 2 h and reperfusion was induced. Before reperfusion,the mice of the I/R+CART group were injected CART via tail vein (0. 5μg, 200μl)and the those of the sham operation+CART group were injected equal CART;repeated administration once every 24 hours. 2,3,5-Triphenyl tetrazolium chloride assay was used to detect cerebral infarction volume of the I/R group and the I/R+CART group at different time points (24 h,72 h,and day 7 )after achieving reperfusion. The transmission electron microscope was used to observe the ultrastructural changes of synapses at different time points,and the synaptic morphological parameters were analyzed quantitatively. Western blot was used to observe the expression level of postsynaptic density 95 (PSD-95)proteins in the surrounding area of cortical infarct at 72 h after reperfusion. Results (1 )Compared with the sham operation group,the number of synapses was significantly decreased in the cortical slices in the I/R group (3. 37 ± 0. 38μm2 vs. 7. 04 ± 0. 55μm2 ,2. 89 ± 0. 22μm2 vs. 6. 89 ± 0. 04μm2 ,3. 25 ± 0. 18μm2 vs. 6. 78 ± 0. 42μm2;all P<0. 05). The density of PSD was significantly decreased (24. 4 ± 2. 8 nm vs. 47. 3 ± 6. 1 nm,23. 8 ± 3. 7 nm vs. 46. 5 ± 7. 5 nm,24. 6 ± 2. 2 nm vs. 48. 1 ± 5. 1 nm;all P <0. 05). The width of synaptic cleft was increased (25. 2 ± 2. 1 nm vs. 21. 5 ± 1. 6 nm,25. 2 ± 1. 4 nm vs. 21. 3 ± 1. 0 nm,23. 7 ± 2. 6 nm vs. 21. 6 ± 1. 6 nm;all P<0. 05). The expression level of PSD-95 protein was decreased at 72 h after reperfusion (P<0. 05). (2)Compared with the I/R group,the infarction volume of the I/R+CART group was significantly reduced at 24 h,72 h,and day 7 after reperfusion (29. 0 ± 1. 9% vs. 36. 3 ± 1. 4%,38. 1 ± 1. 4% vs. 47. 6 ± 2. 7%,and 36. 0 ± 2. 8% vs. 42. 5 ± 2. 0%,respectively;all P<0. 05). The number of synapses was significantly increased (4. 32 ± 0. 35 μm2 )and the expression level of PSD-95 protein was increased at 72 h after reperfusion (P<0. 05). The PSD density (33. 8 ± 3. 4,34. 2 ± 4. 6,38. 2 ± 4. 0 nm)was thickened at 24 h,72 h,and day 7 after reperfusion (all P <0. 05),and there were no significant differences in the width of synaptic cleft at each time point(allP>0.05).Conclusion CART can reduce cerebral infarct volume of I/R in mice and improve synaptic plasticity of cortical neurons in mice after ischemic injury.
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