Department of Physics of Complex Systems, Weizmann Institute of Science, P.O. Box 26, Rehovot 76100 Israel.
Department of Neurobiology, Weizmann Institute of Science, P.O. Box 26, Rehovot 76100 Israel.
EBioMedicine. 2015 Jul 31;2(9):1048-62. doi: 10.1016/j.ebiom.2015.07.038. eCollection 2015 Sep.
Down syndrome (DS) mouse models exhibit cognitive deficits, and are used for studying the neuronal basis of DS pathology. To understand the differences in the physiology of DS model neurons, we used dissociated neuronal cultures from the hippocampi of Ts65Dn and Tc1 DS mice. Imaging of [Ca(2+)]i and whole cell patch clamp recordings were used to analyze network activity and single neuron properties, respectively. We found a decrease of ~ 30% in both fast (A-type) and slow (delayed rectifier) outward potassium currents. Depolarization of Ts65Dn and Tc1 cells produced fewer spikes than diploid cells. Their network bursts were smaller and slower than diploids, displaying a 40% reduction in Δf / f0 of the calcium signals, and a 30% reduction in propagation velocity. Additionally, Ts65Dn and Tc1 neurons exhibited changes in the action potential shape compared to diploid neurons, with an increase in the amplitude of the action potential, a lower threshold for spiking, and a sharp decrease of about 65% in the after-hyperpolarization amplitude. Numerical simulations reproduced the DS measured phenotype by variations in the conductance of the delayed rectifier and A-type, but necessitated also changes in inward rectifying and M-type potassium channels and in the hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. We therefore conducted whole cell patch clamp measurements of M-type potassium currents, which showed a ~ 90% decrease in Ts65Dn neurons, while HCN measurements displayed an increase of ~ 65% in Ts65Dn cells. Quantitative real-time PCR analysis indicates overexpression of 40% of KCNJ15, an inward rectifying potassium channel, contributing to the increased inhibition. We thus find that changes in several types of potassium channels dominate the observed DS model phenotype.
唐氏综合征（DS）小鼠模型表现出认知缺陷，被用于研究 DS 病理的神经元基础。为了了解 DS 模型神经元生理学的差异，我们使用来自 Ts65Dn 和 Tc1 DS 小鼠海马的分离神经元培养物。通过 [Ca(2+)]i 成像和全细胞膜片钳记录分别用于分析网络活动和单个神经元特性。我们发现快速（A 型）和缓慢（延迟整流）外向钾电流均降低约 30%。与二倍体细胞相比，Ts65Dn 和 Tc1 细胞的去极化产生的尖峰较少。它们的网络爆发比二倍体细胞小且慢，钙信号的 Δf / f0 降低了 40%，传播速度降低了 30%。此外，与二倍体神经元相比，Ts65Dn 和 Tc1 神经元的动作电位形状发生了变化，动作电位幅度增加，尖峰触发阈值降低，超极化激活环核苷酸门控（HCN）通道的后超极化幅度急剧降低约 65%。数值模拟通过改变延迟整流和 A 型的电导来再现 DS 测量的表型，但还需要改变内向整流和 M 型钾通道以及 HCN 通道。因此，我们进行了全细胞膜片钳测量 M 型钾电流，结果显示 Ts65Dn 神经元的电流降低了约 90%，而 HCN 测量显示 Ts65Dn 细胞的电流增加了约 65%。实时定量 PCR 分析表明，内向整流钾通道 KCNJ15 的表达增加了 40%，这有助于增加抑制。因此，我们发现几种类型的钾通道的变化主导了观察到的 DS 模型表型。
