Michael Smith Laboratories and Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada.
Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada.
Epilepsia. 2018 Apr;59(4):778-791. doi: 10.1111/epi.14018. Epub 2018 Feb 21.
Genetic alterations have been identified in the CACNA1H gene, encoding the Ca 3.2 T-type calcium channel in patients with absence epilepsy, yet the precise mechanisms relating to seizure propagation and spike-wave-discharge (SWD) pacemaking remain unknown. Neurons of the thalamic reticular nucleus (TRN) express high levels of Ca 3.2 calcium channels, and we investigated whether a gain-of-function mutation in the Cacna1h gene in Genetic Absence Epilepsy Rats from Strasbourg (GAERS) contributes to seizure propagation and pacemaking in the TRN.
Pathophysiological contributions of Ca 3.2 calcium channels to burst firing and absence seizures were assessed in vitro using acute brain slice electrophysiology and quantitative real-time polymerase chain reaction (PCR) and in vivo using free-moving electrocorticography recordings.
TRN neurons from GAERS display sustained oscillatory burst-firing that is both age- and frequency-dependent, occurring only in the frequencies overlapping with GAERS SWDs and correlating with the expression of a Ca 3.2 mutation-sensitive splice variant. In vivo knock-down of Ca 3.2 using direct thalamic injection of lipid nanoparticles containing Ca 3.2 dicer small interfering (Dsi) RNA normalized TRN burst-firing, and in free-moving GAERS significantly shortened seizures.
This supports a role for TRN Ca 3.2 T-type channels in propagating thalamocortical network seizures and setting the pacemaking frequency of SWDs.
在伴有失神发作的患者中，CACNA1H 基因（编码 Ca 3.2 型 T 型钙通道）发生了遗传改变，但与痫性发作传播和棘波放电（SWD）起搏相关的确切机制仍不清楚。丘脑网状核（TRN）神经元表达高水平的 Ca 3.2 钙通道，我们研究了 Strasbourg 遗传性失神癫痫大鼠（GAERS）中 Cacna1h 基因突变是否会影响 TRN 的痫性发作传播和起搏。
使用急性脑片电生理学和实时定量聚合酶链反应（PCR）体外评估 Ca 3.2 钙通道对爆发放电和失神发作的病理生理贡献，并使用自由移动皮层电图记录进行体内评估。
GAERS 的 TRN 神经元显示出持续的振荡爆发式放电，这种放电具有年龄和频率依赖性，仅在与 GAERS SWD 重叠的频率下发生，并且与 Ca 3.2 突变敏感剪接变体的表达相关。通过直接向丘脑内注射含有 Ca 3.2 双链 RNA 小干扰（Dsi）RNA 的脂质纳米颗粒在体内敲低 Ca 3.2，可使 TRN 爆发式放电正常化，并且在自由移动的 GAERS 中可显著缩短癫痫发作。
这支持了 TRN Ca 3.2 T 型通道在传播丘脑皮质网络痫性发作和设定 SWD 起搏频率中的作用。
