The glycoprotein reelin has been implicated in both memory-related synaptic plasticity and Alzheimer's disease pathogenesis. Aged rats with memory impairment display decreased reelin expression in layer II of the entorhinal cortex (EC) relative to memory-intact subjects, and here we tested whether this effect extends to the primate brain. Seven young adult (8-10 years) and 14 aged (27-38 years) rhesus monkeys (Macaca mulatta) were examined, including 7 old animals classified as impaired based on their scores from a delayed nonmatching-to-sample recognition memory test. Histological sections spanning the rostrocaudal extent of the intermediate and caudal divisions of EC were processed by immunohistochemistry and the total number of reelin-positive neurons in layer II was estimated using design-based stereological techniques. The main finding was that the number of reelin-expressing neurons in EC layer II is decreased selectively in aged monkeys with memory deficits relative to young adult and aged subjects with intact memory. The results add to evidence implicating EC-hippocampal integrity in neurocognitive aging, and they suggest that disrupted reelin signaling may be among the mechanisms that mediate the associated vulnerability of this circuitry in Alzheimer's disease.

中文翻译：

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Reelin in the Years：记忆障碍老年猴子内嗅皮层第 II 层中 reelin 免疫反应神经元的数量下降

糖蛋白 reelin 与记忆相关的突触可塑性和阿尔茨海默病的发病机制有关。与记忆完好的受试者相比，具有记忆障碍的老年大鼠在内嗅皮层 (EC) 的第二层中的 reelin 表达降低，在这里我们测试了这种影响是否延伸到灵长类动物的大脑。检查了 7 只年轻成年（8-10 岁）和 14 只年龄（27-38 岁）恒河猴（猕猴），包括 7 只根据延迟非匹配样本识别记忆测试得分被归类为受损的老年动物。通过免疫组织化学处理跨越 EC 中间和尾部分裂的 rostrocaudal 范围的组织学切片，并使用基于设计的立体技术估计第 II 层中 reelin 阳性神经元的总数。主要发现是，与具有完整记忆的年轻成人和老年受试者相比，具有记忆缺陷的老年猴子的 EC 层 II 中表达 reelin 的神经元数量选择性减少。结果增加了暗示 EC-海马完整性与神经认知衰老有关的证据，并且他们表明，被破坏的 reelin 信号传导可能是介导阿尔茨海默病中该电路相关脆弱性的机制之一。