Zhong Le, Yan Chong-huai, Huang Hua, Lu Cheng-qiu, Xu Jian, Yu Xiao-gang, Shen Xiao-ming
Xinhua Hospital, Medical School of Shanghai Jiaotong University, Shanghai 200092, China.
Zhonghua Yi Xue Za Zhi. 2007 Jun 12;87(22):1559-63.
To explore the effects of preweaning exposure to enriched environment on hippocampal neurogenesis and the underlying mechanisms.
Thirty-six 10-day-old SD rats were randomly divided into the 2 equal groups: control group and enriched environment group (EE group. From the age of 10 days to 24 days the rats received intraperitoneal injection of bromodeoxyuridine (BrdU) 50 mg/kg every other day to label the newly proliferated cells in vivo, and the rats in EE group were daily exposed to enriched environment for 20 minutes. Six rats of each group were sacrificed whren they were 24 days of age. Nuclear protein of the hippocampus was extracted to undergo Western blotting to detect the levels of calmodulin and phosphorylated CREB (cAMP response element binding). Other rats were sacrificed at the age of 63 days. Coronal cryostat sections of brain were cut. Sections at the level 3.6 mm posterior to the bregma were obtained and stained with methyl aniline blue and the number of cells in the hippocampal dentate gurus (DG) of the right hemisphere were counted using x 400 microscope. BrdU immunohistochemistry and double immunofluorescence labeling with BrdU/NeuN or BrdU/GFAP were done, and the numbers of BrdU-labeled cells and ratios of neurons and astrocytes differentiated from BrdU-labeled cells were calculated.
The levels of calmodulin and phosphorylated CREB in the hippocampal nuclear extract of the EE group were 0.065 +/- 0.035 and 0.485 +/- 0.007 respectively, both significantly higher than those of the control group (0.245 +/- 0.035 and 0.220 +/- 0.014 respectively, P = 0.01 and P = 0.002). The number of cells in the DG area of right hippocampus 3.6 mm posterior to bregma of the EE group was 1580 +/- 72, significantly higher than that of the control rats (1375 +/- 62, t = -7.461, P < 0.01). The number of BrdU labeled cells of the EE group was 5363 +/- 487, significantly higher than that of the control group (2984 +/- 318, t = -14.177, P < 0.01). The ratio of neurons of the EE group was 85.0% +/- 2.8%, significantly higher than that of the control group (80.2% +/- 2.8%, t = -4.166, P < 0.01). The differentiation rate of astrocytes of the EE group was 4.0% +/- 0.5%, significantly higher than that of the control group (2.6% +/- 0.6%, t = -6.493, P < 0.01).
Preweaning exposure to enriched environment can induce neurogenesis. The underlying mechanism may be that enriched environment induces the activation of calmodulin and CREB in hippocampus.
探讨断奶前暴露于丰富环境对海马神经发生的影响及其潜在机制。
将36只10日龄的SD大鼠随机分为两组，每组18只：对照组和丰富环境组（EE组）。从10日龄至24日龄，大鼠每隔一天腹腔注射50mg/kg溴脱氧尿苷（BrdU）以标记体内新增殖的细胞，EE组大鼠每天暴露于丰富环境20分钟。每组6只大鼠在24日龄时处死，提取海马核蛋白进行蛋白质免疫印迹法检测钙调蛋白和磷酸化环磷腺苷反应元件结合蛋白（CREB）水平。其他大鼠在63日龄时处死，制作脑冠状冰冻切片，获取前囟后3.6mm水平的切片，用甲基苯胺蓝染色，在400倍显微镜下计数右侧海马齿状回（DG）的细胞数量。进行BrdU免疫组织化学以及BrdU/神经元核抗原（NeuN）或BrdU/胶质纤维酸性蛋白（GFAP）双免疫荧光标记，计算BrdU标记细胞的数量以及由BrdU标记细胞分化而来的神经元和星形胶质细胞的比例。
EE组海马核提取物中钙调蛋白和磷酸化CREB水平分别为0.065±0.035和0.485±0.007，均显著高于对照组（分别为0.245±0.035和0.220±0.014，P = 0.01，P = 0.002）。EE组前囟后3.6mm处右侧海马DG区细胞数量为1580±72，显著高于对照大鼠（1375±62，t = -7.461，P < 0.01）。EE组BrdU标记细胞数量为5363±487，显著高于对照组（2984±318，t = -14.177，P < 0.01）。EE组神经元比例为85.0%±2.8%，显著高于对照组（80.2%±2.8%，t = -4.166，P < 0.01）。EE组星形胶质细胞分化率为4.0%±0.5%，显著高于对照组（2.6%±0.6%，t = -6.493，P < 0.01）。
断奶前暴露于丰富环境可诱导神经发生。其潜在机制可能是丰富环境诱导海马中钙调蛋白和CREB的激活。
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