Center for Dementia Research, Nathan Kline Institute, New York University School of Medicine, 140 Old Orangeburg Road, Orangeburg, NY 10962, USA.
Eur J Neurosci. 2010 Jan;31(1):110-8. doi: 10.1111/j.1460-9568.2009.07031.x. Epub 2009 Dec 21.
Although transgenic mouse models of Alzheimer's disease (AD) recapitulate amyloid-beta (Abeta)-related pathologies and cognitive impairments, previous studies have mainly evaluated their hippocampus-dependent memory dysfunctions using behavioral tasks such as the water maze and fear conditioning. However, multiple memory systems become impaired in AD as the disease progresses and it is important to test whether other forms of memory are affected in AD models. This study was designed to use conditioned taste aversion (CTA) and contextual fear conditioning paradigms to compare the phenotypes of hippocampus-independent and -dependent memory functions, respectively, in 5XFAD amyloid precursor protein/presenilin-1 transgenic mice that harbor five familial AD mutations. Although both types of memory were significantly impaired in 5XFAD mice, the onset of CTA memory deficits ( approximately 9 months of age) was delayed compared with that of contextual memory deficits ( approximately 6 months of age). Furthermore, 5XFAD mice that were genetically engineered to have reduced levels of beta-site amyloid precursor protein-cleaving enzyme 1 (BACE1) (BACE1(+/-).5XFAD) exhibited improved CTA memory, which was equivalent to the performance of wild-type controls. Importantly, elevated levels of cerebral beta-secretase-cleaved C-terminal fragment (C99) and Abeta peptides in 5XFAD mice were significantly reduced in BACE1(+/-).5XFAD mice. Furthermore, Abeta deposition in the insular cortex and basolateral amygdala, two brain regions that are critically involved in CTA performance, was also reduced in BACE1(+/-).5XFAD compared with 5XFAD mice. Our findings indicate that the CTA paradigm is useful for evaluating a hippocampus-independent form of memory defect in AD model mice, which is sensitive to rescue by partial reductions of the beta-secretase BACE1 and consequently of cerebral Abeta.
尽管阿尔茨海默病(AD)的转基因小鼠模型再现了淀粉样β(Abeta)相关的病理学和认知障碍,但以前的研究主要使用行为任务(如水迷宫和恐惧条件反射)评估其海马依赖性记忆功能障碍。然而,随着疾病的进展,多种记忆系统受损,因此重要的是要测试 AD 模型中是否存在其他形式的记忆受损。本研究旨在使用条件味觉厌恶(CTA)和情境恐惧条件反射范式,分别比较具有五个家族性 AD 突变的淀粉样前体蛋白/早老素-1 转基因 5XFAD 小鼠的海马无关和依赖记忆功能的表型。尽管两种类型的记忆在 5XFAD 小鼠中均明显受损,但 CTA 记忆缺陷的发作(约 9 月龄)晚于情境记忆缺陷(约 6 月龄)。此外,具有降低水平的β位淀粉样前体蛋白裂解酶 1(BACE1)的基因工程 5XFAD 小鼠(BACE1(+/-).5XFAD)表现出改善的 CTA 记忆,与野生型对照相当。重要的是,在 5XFAD 小鼠中升高的脑β-分泌酶切割的 C 端片段(C99)和 Abeta 肽水平在 BACE1(+/-).5XFAD 小鼠中显著降低。此外,在 BACE1(+/-).5XFAD 与 5XFAD 小鼠相比,参与 CTA 表现的两个大脑区域,即岛叶皮层和基底外侧杏仁核中的 Abeta 沉积也减少。我们的研究结果表明,CTA 范式可用于评估 AD 模型小鼠中与海马无关的记忆缺陷形式,该形式对β-分泌酶 BACE1的部分降低(继而对脑 Abeta)的挽救敏感。