Pharmacology and Toxicology, Institute of Pharmacy, University of Tübingen, Tübingen, Germany.
PLoS One. 2010 Dec 30;5(12):e15601. doi: 10.1371/journal.pone.0015601.
Neuronal calcium-activated potassium channels of the BK type are activated by membrane depolarization and intracellular Ca(2+) ions. It has been suggested that these channels may play a key neuroprotective role during and after brain ischemia, but this hypothesis has so far not been tested by selective BK-channel manipulations in vivo. To elucidate the in vivo contribution of neuronal BK channels in acute focal cerebral ischemia, we performed middle cerebral artery occlusion (MCAO) in mice lacking BK channels (homozygous mice lacking the BK channel alpha subunit, BK(-/-)). MCAO was performed in BK(-/-) and WT mice for 90 minutes followed by a 7-hour-reperfusion period. Coronal 1 mm thick sections were stained with 2,3,5-triphenyltetrazolium chloride to reveal the infarction area. We found that transient focal cerebral ischemia by MCAO produced larger infarct volume, more severe neurological deficits, and higher post-ischemic mortality in BK(-/-) mice compared to WT littermates. However, the regional cerebral blood flow was not significantly different between genotypes as measured by Laser Doppler (LD) flowmetry pre-ischemically, intra-ischemically, and post-ischemically, suggesting that the different impact of MCAO in BK(-/-) vs. WT was not due to vascular BK channels. Furthermore, when NMDA was injected intracerebrally in non-ischemic mice, NMDA-induced neurotoxicity was found to be larger in BK(-/-) mice compared to WT. Whole-cell patch clamp recordings from CA1 pyramidal cells in organotypic hippocampal slice cultures revealed that BK channels contribute to rapid action potential repolarization, as previously found in acute slices. When these cultures were exposed to ischemia-like conditions this induced significantly more neuronal death in BK(-/-) than in WT cultures. These results indicate that neuronal BK channels are important for protection against ischemic brain damage.
BK 型神经元钙激活钾通道可被膜去极化和细胞内 Ca(2+) 离子激活。有人认为，这些通道在脑缺血期间和之后可能发挥关键的神经保护作用，但迄今为止，尚未通过体内选择性 BK 通道操作来检验这一假说。为了阐明急性局灶性脑缺血时神经元 BK 通道的体内作用，我们在缺乏 BK 通道的小鼠（BK 通道 α 亚单位缺失的纯合子小鼠，BK(-/-))中进行了大脑中动脉闭塞 (MCAO)。在 BK(-/-)和 WT 小鼠中进行 MCAO 90 分钟，然后进行 7 小时再灌注期。用 2,3,5-三苯基氯化四氮唑染色冠状 1 毫米厚的切片以显示梗塞面积。我们发现，与 WT 同窝仔鼠相比，短暂的局灶性脑缺血通过 MCAO 导致更大的梗塞体积、更严重的神经功能缺损和更高的缺血后死亡率。然而，通过激光多普勒 (LD) 血流测量，在缺血前、缺血中和缺血后，两种基因型之间的局部脑血流无明显差异，表明 MCAO 在 BK(-/-)与 WT 之间的不同影响不是由于血管 BK 通道。此外，当 NMDA 被脑内注射到非缺血小鼠中时，发现 NMDA 诱导的神经毒性在 BK(-/-)小鼠中比 WT 小鼠更大。在器官型海马切片培养物的 CA1 锥体神经元中进行全细胞膜片钳记录显示，BK 通道有助于快速动作电位复极，如在急性切片中发现的那样。当这些培养物暴露于类似缺血的条件下时，BK(-/-)培养物中的神经元死亡明显多于 WT 培养物。这些结果表明，神经元 BK 通道对于保护免受缺血性脑损伤很重要。
