衰老与海马CA1区锥体细胞退行性变及自由基和空间记忆的关系

目的:研究衰老大鼠记忆行为、自由基含量和CA1区细胞超微结构的特征以及衰老所致记忆减退的神经生物学机制。方法:雄性SD大鼠40只,青年和老年组各20只。应用Morris水迷宫测量大鼠空间记忆水平,分光光度计测量海马组织蛋白质的含量;巴比妥酸还原法测定海马脂质过氧化物含量;透射电镜观察海马CA1区锥体细胞的形态;体视学分析细胞内粗面内质网和线粒体的面数密度。结果:较之青年大鼠,衰老大鼠寻找平台的潜伏期延长(38与12s,t=8.04,P<0.01);跨平台次数的百分比减少(50%与82%,t=10.17,P<0.05)。海马脂质过氧化物(146.2与178.4nmol/g,t=5.61,P<0.01)、组织总蛋白(127.9与168.8μg比较,t=8.25,P<0.01)和非水溶性蛋白(21.1与34.3μg比较,t=9.53,P<0.01)的含量增高;海马CA1区250μm锥体细胞的数量(51.9与40.7个比较,t=6.55,P<0.01)、核仁体积(5.34与4.02μm3,t=7.71,P<0.01)、粗面内质网面密度(1.47与0.94μm2/μm3,t=6.55,P<0.01)减少。结论:海马CA1区锥体细胞的退行性变化是衰老致记忆减退的原因之一,而过量的脂质过氧化物可能是导致锥体细胞变性的原因。

Relationships of aging with the degeneration of CA1 pyramidal cells, free radical contents of hippocampus and spatial memory of rats

AIM:To observe the characteristics of memory behavior, free radical contents and ultrastructural morphometry of pyramidal cells of hippocampal CA1 sector of aged rats in order to study the neurobiological mechanism of age related memory deficiency. METHODS:Forty male SD rats were randomly divided into young and aged groups, with 20 rats for each group. Morris water maze test was used to observe learning and memory behavior of all the rats. The homogenates of rat hippocampus was used to determine the amount of lipid peroxide using the barbituric acid reactive substances assay, and the protein content was determined by spectrophotometer.The ultrastructural morphology of hippocampal CA1 pyramidal cells was observed using transmission electron microscope (TEM), and the morphometrical quantification and stereological technique were used to compare the numbers and sizes of cell nuclei, rough endoplasmic reticulum and mitochondria between the two groups. RESULTS:Compared with the young rats, the aged rats showed the longer latency (38 vs 12 s, t=8.04, P< 0.01) in place navigation during the place training experiment and less crossing numbers over the platform (50% vs 82% , t=10.17, P< 0.05) during spatial probe test. The amount of lipid peroxide(146.2 vs 178.4 nmol/g, t=5.61, P< 0.01 ), tissue total protein (127.9 vs 168.8 μ g, t=8.25, P< 0.01) and sedimental protein (21.1 vs 34.3 μ g, t=9.53, P< 0.01 )were all increased in aged rats, compared with those in the young rats. A lot of pyramidal cells in 250 μ m CA1 sector (51.9 vs 40.7, t=6.55, P< 0.01 ) lost with smaller volume of nucleoli (5.34 vs 4.02 μ m3, t=6.55, P< 0.01 ). The rough endoplasmic reticulum density (1.47 vs 0.94 μ m2/ μ m3, t=10.44) and mitochondria of pyramidal cells were less and smaller in the aged rats than those in the young rats. CONCLUSION:Degenerative changes are present in pyramidal cells in hippocampal CA1 sector. The degeneration is one of the causes that lead to spatial memory deficient of the aged rats. The overdose lipid peroxide may result in the degeneration of pyramidal cells.