摘要目的 研究高频重复经颅磁刺激(rTMS)对全脑缺血大鼠学习记忆的影响并探讨其机制.方法 将体重210～250 g的35只雄性SD大鼠(8～10周龄)按随机区组法随机分为假手术组(8只)、模型组(9只)、rTMS组(9只)、假刺激组(9只),采用改良四血管阻断法制作全脑缺血大鼠模型,其中rTMS组给予连续2周的10 Hz rTMS刺激,假刺激组给予假刺激.利用Morris水迷宫检测大鼠空间学习记忆能力,多通道在体记录技术采集海马CA1区局部场电位(local field potentials,LFPs)分析θ和γ节律振荡,免疫组织化学和蛋白免疫印迹法检测海马组织蛋白激酶A(PKA)、磷酸化环磷腺苷效应元件结合蛋白(p-CREB)表达.结果 模型组与假手术组相比,平均逃避潜伏期延长[(35.16±0.80)s与(16.57±0.74)s,k=3.723,P=0.013]、跨越平台次数减少[(1.14±0.42)次与(4.46±0.23)次,k=3.185,P=0.042]以及原平台象限游泳时间缩短[(14.46±0.73)s与(29.31±0.42)s,k=3.027,P=0.047],海马CA1区LFPs θ和γ功率谱密度均值降低[分别为(-68.48±2.61)Hz与(-59.38±2.25)Hz,k=2.958,P=0.048;(-82.23±4.60)Hz与(-70.50±4.25)Hz,k=3.729,P=0.021],免疫组织化学染色显示海马PKA、p-CREB表达减少(分别为7 184.26±975.12与25 137.35±1 010.62,k=3.588,P=0.027;1 803.73±336.18与20 175.25±727.23,k=2.912,P=0.049);rTMS组与模型组相比,平均逃避潜伏期缩短[(24.69±1.01)s与(35.16±0.80)s,k=4.082,P=0.034]、跨越平台次数增加[(2.42±0.31)次与(1.14±0.42)次,t=3.296,P=0.039]及原平台象限游泳时间延长[(23.07±0.67)s与(14.46±0.73)s,k=4.323,P=0.012],海马CA1区LFPs θ和γ功率谱密度均值升高[分别为(-63.81±3.12)Hz与(-68.48±2.61)Hz,k=3.582,P=0.015;(-75.80±4.58) Hz与(-82.23±4.60)Hz,k=4.051,P=0.026],免疫组织化学染色显示海马PKA、p-CREB表达增加(分别为13 065.32±1 045.18与7 184.26±975.12,k=3.923,P=0.031;11 032.83±562.86与1 803.73±336.18,k=3.178,P=0.038).结论 高频rTMS可能通过增强海马CA1区θ和γ振荡和提高海马PKA、p-CREB蛋白表达,增强海马神经元突触可塑性,从而改善全脑缺血大鼠的学习记忆障碍.

abstractsObjective To study the effect of high frequency repeated transcranial magnetic stimulation (rTMS) on learning and memory in rats with global cerebral ischemia and to investigate its mechanism.Methods Thirty-five male Sprague-Dawley rats (8-10 weeks old) were randomly divided into sham operation group (n=8),model group (n=9),sham-rTMS (s-rTMS) group (n=9) and rTMS group (n=9).The global cerebral ischemia model was established by modified four-vessel occlusion method.The rTMS group received 10 Hz rTMS stimulation for two weeks,whereas the s-rTMS group received sham stimulation.Morris water maze test was used to detect the spatial learning ability,multi-channel recording technique was used to detect the local field potentials in the hippocampus CA1 region of theta and gamma oscillation,and immunohistochemical staining and Western blotting were used to detect the expression of protein kinase A (PKA) and phosphorylated cyclic adenosine monophosphate response element binding protein (p-CREB) of hippocampus.Results The average escape latency in the model group was longer than that in the sham operation group ((35.16±0.80) s vs (16.57±0.74) s,k=3.723,P=0.013),the spanning platform times and the original platform quadrant swimming time in the model group were shorter than that in the sham operation group (1.14±0.42 vs 4.46±0.23,k=3.185,P=0.042;(14.46±0.73) s vs (29.31±0.42) s,k=3.027,P=0.047).Compared with the sham operation group,the mean power spectral density of theta and gamma reduced ((-68.48±2.61) Hz vs (-59.38±2.25) Hz,k=2.958,P=0.048;(-82.23±4.60) Hz vs (-70.50±4.25) Hz,k=3.729,P=0.021),and the expression of PKA and p-CREB protein decreased in the model group (7 184.26±975.12 vs 25 137.35±1 010.62,k=3.588,P=0.027;1 803.73±336.18 vs 20 175.25±727.23,k=2.912,P=0.049).The average escape latency in the rTMS group was shorter than that in the model group ((24.69± 1.01) s vs (35.16±0.80) s,k=4.082,P=0.034),and the spanning platform times and the original platform quadrant swimming time in the rTMS group was longer than that in the model group (2.42±0.31 vs 1.14±0.42,k=3.296,P=0.039;(23.07±0.67) s vs (14.46±0.73) s,k=4.323,P=0.012).Compared with the rTMS group,the power spectral density of theta and gamma reduced ((-63.81±3.12) Hz vs (-68.48±2.61) Hz,k=3.582,P=0.015;(-75.80±4.58) Hz vs (-82.23±4.60) Hz,k=4.051,P=0.026),and the expression of PKA and p-CREB protein decreased in the model group (13 065.32±1 045.18 vs 7 184.26±975.12,k=3.923,P=0.031;11 032.83±562.86 vs 18 03.73±336.18,k=3.178,P=0.038).Conclusion High frequency rTMS could improve learning and memory of global cerebral ischemia rats,the mechanism of which might be that rTMS enhance the hippocampal theta and gamma oscillations and increase the expression of PKA and p-CREB protein in the hippocampus,thus increasing the hippocampus synaptic plasticity.