Central cholinergic function in AChE-deficient mice

描述(申请人提供)：乙酰胆碱酯酶(AChE)是负责胆碱能突触中神经递质乙酰胆碱(ACh)分解的酶。在大脑中，ACh对注意力、学习和记忆等重要功能起辅助作用。在阿尔茨海默病期间，支配皮质和海马区的中枢胆碱能神经元典型地退化；这一过程伴随着阿尔茨海默病患者的注意力和记忆障碍。在目前的建议中，我们建议研究缺乏AChE的转基因小鼠的中枢胆碱能功能。这些小鼠有身体震颤，并容易癫痫发作，这与由于缺乏酶分解而导致的ACh过量是一致的。我们研究的第一个目的是量化AChE缺陷小鼠与杂合子小鼠和对照组小鼠脑细胞外ACh的水平。为此，我们将使用适用于小鼠的微透析技术。我们还将测量高亲和力胆碱摄取，以确定胆碱能神经元ACh周转的可能代偿性变化。然而，AChE缺乏的小鼠还活着这一事实表明，可能存在其他途径来分解ACh。丁酰胆碱酯酶(BChE)是一种与大脑中神经胶质细胞相关但功能未知的酶，它以缓慢的速度水解乙酰胆碱酯酶。我们假设BChE能在AChE缺乏的小鼠中水解乙酰胆碱，从而使它们存活。因此，我们的第二个目标是测试在应用特定的AChE或BChE抑制剂后，大脑中细胞外ACh的变化。我们的结果将显示大脑可以在多大程度上补偿疼痛的损失；这也是人们对有机磷(神经毒气)中毒的兴趣。我们还将确定BChE在多大程度上可以替代大脑中的AChE。我们的结果将表明，BChE的抑制剂是否对阿尔茨海默病的治疗有用。在没有外周胆碱能毒性的情况下，BChE抑制剂有望增加阿尔茨海默病患者的脑ACh，从而提高治疗安全性。

DESCRIPTION (provided by applicant): Acetylcholinesterase (ACHE) is the enzyme which is responsible for the breakdown of the neurotransmitter, acetylcholine (ACh), in cholinergic synapses. In the brain, ACh subserves important functions e.g. for attention, learning and memory. Central cholinergic neurons which innervate cortex and hippocampus are typically degenerating during Alzheimer's disease; this process is accompanied by attention and memory deficits in Alzheimer patients. In the present proposal, we suggest to investigate central cholinergic functions in genetically modified mice which are deficient for ACHE. These mice have body tremor and are prone to seizures, observations which are compatible with an excess of ACh due to lack of enzymatic breakdown. The first aim of our study is to quantify extracellular levels of ACh in the brain of AChE-deficient mice compared to heterozygous mice and control mice. For this purpose, we will use the microdialysis technique adapted to mice. We will also measure high-affinity choline uptake to determine possible compensatory changes of ACh turnover in cholinergic neurons. However, the fact that AChE-deficient mice are alive suggests that other pathways may exist to break down ACh. Butyrylcholinesterase (BChE), an enzyme associated with glial cells in the brain but of unknown function, is known to hydrolyze ACh at slow rates. We hypothesize that BChE hydrolyzes ACh in AChE-deficient mice thereby making them viable. Our second aim therefore is to test changes of extracellular ACh in the brain upon application of specific inhibitors of AChE or BChE. Our results will show to what extent the brain can compensate for the loss of ACHE; this is also of interest for intoxications of humans with organophosphates (nerve gases). We will also determine to what extent BChE can substitute for AChE in the brain. Our results will show if inhibitors of BChE may be useful for the treatment of Alzheimer's disease. BChE inhibitors would be expected to increase brain ACh in Alzheimer patients in the absence of peripheral cholinergic toxicity thereby improving therapeutic safety.