Gautam Akash, Kaul Sunil C, Thakur Mahendra K
Biochemistry and Molecular Biology Laboratory, Department of Zoology, Banaras Hindu University, Varanasi, 221005, India.
Centre for Neural and Cognitive Sciences, University of Hyderabad, Hyderabad, 500046, India.
Mol Neurobiol. 2016 Apr;53(3):1760-1769. doi: 10.1007/s12035-015-9117-2. Epub 2015 Mar 7.
Our earlier report on scopolamine-induced amnesia and its improvement by pre-treatment with i-Extract (alcoholic extract of Ashwagandha leaf) suggested that the i-Extract mediated nootropic effect may involve neuronal immediate early gene, Arc. With a hypothesis that the i-Extract induced expression of Arc protein may cause augmentation in Arc function, we examined the effect of i-extract on a major function of Arc protein, i.e. F-actin expansion, using Arc antisense oligodeoxynucleotides (ODN). Stereotaxic infusion of Arc antisense ODN in the CA1 region of hippocampus decreased the level of Arc protein as demonstrated by immunoblotting. However, this decrease was attenuated when treated with i-Extract prior to infusion of Arc antisense ODN. We noted a significant decrease in the polymerization of F-actin during scopolamine-induced amnesia as well as Arc antisense ODN infusion that was restored rather enhanced when pre-treated with i-Extract in both the cases. We also compared the corresponding changes between CA1 (the infusion site) and CA3 (neighbouring site of infusion) regions of hippocampus, and found more pronounced effects in CA1 than in the CA3 region. The extent of F-actin polymerization, as revealed by changes in the dendritic spine architecture through Golgi staining, showed that both scopolamine as well as Arc antisense ODN disrupted the spine density and mushroom-shaped morphology that was again regained if pre-treated with i-Extract. In conclusion, the findings reveal that the Arc helps in polymerization of F-actin and subsequent changes in the morphology of dendritic spines after pre-treatment with i-Extract in scopolamine-induced amnesic mice, suggesting an important role of Arc in scopolamine-induced amnesia and its recovery by i-Extract.
我们之前关于东莨菪碱诱导失忆及其通过印度人参叶醇提取物（i-Extract）预处理得到改善的报告表明，i-Extract介导的益智作用可能涉及神经元即刻早期基因Arc。基于i-Extract诱导Arc蛋白表达可能导致Arc功能增强的假设，我们使用Arc反义寡脱氧核苷酸（ODN）研究了i-Extract对Arc蛋白一项主要功能（即F-肌动蛋白扩张）的影响。通过免疫印迹证实，在海马体CA1区立体定位注入Arc反义ODN可降低Arc蛋白水平。然而，在注入Arc反义ODN之前用i-Extract处理时，这种降低作用会减弱。我们注意到，在东莨菪碱诱导失忆以及注入Arc反义ODN过程中，F-肌动蛋白的聚合显著减少，而在这两种情况下，预先用i-Extract处理后，这种减少得到恢复甚至增强。我们还比较了海马体CA1区（注入部位）和CA3区（注入相邻部位）的相应变化，发现CA1区的影响比CA3区更明显。通过高尔基染色观察树突棘结构变化所揭示的F-肌动蛋白聚合程度表明，东莨菪碱和Arc反义ODN均破坏了棘密度和蘑菇状形态，而预先用i-Extract处理后又可恢复。总之，研究结果表明，在东莨菪碱诱导失忆的小鼠中，预先用i-Extract处理后，Arc有助于F-肌动蛋白聚合以及随后树突棘形态的变化，这表明Arc在东莨菪碱诱导失忆及其通过i-Extract恢复过程中发挥重要作用。
