Minkeviciene Rimante, Rheims Sylvain, Dobszay Marton B, Zilberter Misha, Hartikainen Jarmo, Fülöp Lívia, Penke Botond, Zilberter Yuri, Harkany Tibor, Pitkänen Asla, Tanila Heikki
A. I. Virtanen Institute, University of Kuopio, FIN-70211 Kuopio, Finland.
J Neurosci. 2009 Mar 18;29(11):3453-62. doi: 10.1523/JNEUROSCI.5215-08.2009.
Alzheimer's disease is associated with an increased risk of unprovoked seizures. However, the underlying mechanisms of seizure induction remain elusive. Here, we performed video-EEG recordings in mice carrying mutant human APPswe and PS1dE9 genes (APdE9 mice) and their wild-type littermates to determine the prevalence of unprovoked seizures. In two recording episodes at the onset of amyloid beta (Abeta) pathogenesis (3 and 4.5 months of age), at least one unprovoked seizure was detected in 65% of APdE9 mice, of which 46% had multiple seizures and 38% had a generalized seizure. None of the wild-type mice had seizures. In a subset of APdE9 mice, seizure phenotype was associated with a loss of calbindin-D28k immunoreactivity in dentate granular cells and ectopic expression of neuropeptide Y in mossy fibers. In APdE9 mice, persistently decreased resting membrane potential in neocortical layer 2/3 pyramidal cells and dentate granule cells underpinned increased network excitability as identified by patch-clamp electrophysiology. At stimulus strengths evoking single-component EPSPs in wild-type littermates, APdE9 mice exhibited decreased action potential threshold and burst firing of pyramidal cells. Bath application (1 h) of Abeta1-42 or Abeta25-35 (proto-)fibrils but not oligomers induced significant membrane depolarization of pyramidal cells and increased the activity of excitatory cell populations as measured by extracellular field recordings in the juvenile rodent brain, confirming the pathogenic significance of bath-applied Abeta (proto-)fibrils. Overall, these data identify fibrillar Abeta as a pathogenic entity powerfully altering neuronal membrane properties such that hyperexcitability of pyramidal cells culminates in epileptiform activity.
阿尔茨海默病与无诱因癫痫发作风险增加相关。然而，癫痫发作诱导的潜在机制仍不清楚。在此，我们对携带突变型人类APPswe和PS1dE9基因的小鼠（APdE9小鼠）及其野生型同窝小鼠进行了视频脑电图记录，以确定无诱因癫痫发作的发生率。在淀粉样β蛋白（Aβ）发病初期的两次记录阶段（3个月和4.5个月龄），65%的APdE9小鼠检测到至少一次无诱因癫痫发作，其中46%有多次癫痫发作，38%有全身性癫痫发作。野生型小鼠均未出现癫痫发作。在一部分APdE9小鼠中，癫痫表型与齿状颗粒细胞中钙结合蛋白-D28k免疫反应性丧失以及苔藓纤维中神经肽Y的异位表达有关。在APdE9小鼠中，通过膜片钳电生理学确定，新皮层第2/3层锥体细胞和齿状颗粒细胞的静息膜电位持续降低，这是网络兴奋性增加的基础。在野生型同窝小鼠中，刺激强度诱发单成分兴奋性突触后电位时，APdE9小鼠的锥体细胞动作电位阈值降低且出现爆发性放电。在幼年啮齿动物脑中，通过细胞外场记录测量，浴用（1小时）Aβ1-42或Aβ25-35（原）纤维而非寡聚体可诱导锥体细胞膜显著去极化，并增加兴奋性细胞群体的活性，证实了浴用Aβ（原）纤维的致病意义。总体而言，这些数据确定纤维状Aβ是一种致病实体，可有力改变神经元膜特性，使锥体细胞的过度兴奋最终导致癫痫样活动。
