皮质扩散性抑制的启动机制。

BACKGROUND: There is increasing evidence from human and animal studies that cortical spreading depression (CSD) is the neurophysiological correlate of migraine aura and a trigger of migraine pain mechanisms. The mechanisms of initiation of CSD in the brain of migraineurs remain unknown, and the mechanisms of initiation of experimentally induced CSD in normally metabolizing brain tissue remain incompletely understood and controversial. Here, we investigated the mechanisms of CSD initiation by focal application of KCl in mouse cerebral cortex slices. METHODS: High KCl puffs of increasing duration up to the threshold duration eliciting a CSD were applied on layer 2/3 whilst the membrane potential of a pyramidal neuron located very close to the site of KCl application and the intrinsic optic signal were simultaneously recorded. This was done before and after the application of a specific blocker of either NMDA or AMPA glutamate receptors (NMDARs, AMPARs) or voltage-gated Ca (Ca) channels. If the drug blocked CSD, stimuli up to 12-15 times the threshold were applied. RESULTS: Blocking either NMDARs with MK-801 or Ca channels with Ni completely inhibited CSD initiation by both CSD threshold and largely suprathreshold KCl stimuli. Inhibiting AMPARs with NBQX was without effect on the CSD threshold and velocity. Analysis of the CSD subthreshold and threshold neuronal depolarizations in control conditions and in the presence of MK-801 or Ni revealed that the mechanism underlying ignition of CSD by a threshold stimulus (and not by a just subthreshold stimulus) is the Ca-dependent activation of a threshold level of NMDARs (and/or of channels whose opening depends on the latter). The delay of several seconds with which this occurs underlies the delay of CSD initiation relative to the rapid neuronal depolarization produced by KCl. CONCLUSIONS: Both NMDARs and Ca channels are necessary for CSD initiation, which is not determined by the extracellular K or neuronal depolarization levels per se, but requires the Ca-dependent activation of a threshold level of NMDARs. This occurs with a delay of several seconds relative to the rapid depolarization produced by the KCl stimulus. Our data give insights into potential mechanisms of CSD initiation in migraine.

背景：越来越多的来自人类和动物研究的证据表明，皮质扩散性抑制（CSD）是偏头痛先兆的神经生理学相关物，也是偏头痛疼痛机制的触发因素。偏头痛患者大脑中 CSD 起始的机制尚不清楚，而在正常代谢脑组织中诱发 CSD 起始的机制仍不完全了解且存在争议。在这里，我们研究了在小鼠大脑皮层切片中通过局部施加 KCl 引发 CSD 的机制。

方法：在层 2/3 上施加持续时间递增的高 KCl 脉冲，直至引发 CSD 的阈值持续时间，同时记录非常靠近 KCl 施加部位的锥体神经元的膜电位和固有光信号。在施加特定的 NMDA 或 AMPA 谷氨酸受体（NMDARs、AMPA Rs）或电压门控 Ca（Ca）通道阻滞剂之前和之后进行此操作。如果药物阻断 CSD，则施加高达阈值 12-15 倍的刺激。

结果：用 MK-801 阻断 NMDARs 或用 Ni 阻断 Ca 通道完全抑制了 CSD 阈值和大量超阈值 KCl 刺激引发的 CSD 起始。用 NBQX 抑制 AMPARs 对 CSD 阈值和速度没有影响。在对照条件下以及在 MK-801 或 Ni 存在下分析 CSD 阈下和阈值神经元去极化，结果表明，阈刺激引发 CSD 的机制（而不是仅阈下刺激）是 Ca 依赖性激活阈值水平的 NMDARs（和/或其开放取决于后者的通道）。这种情况发生的几秒钟延迟是 CSD 起始相对于 KCl 产生的快速神经元去极化的延迟的基础。

结论：NMDARs 和 Ca 通道对于 CSD 起始都是必需的，CSD 起始不是由细胞外 K 或神经元去极化水平本身决定的，而是需要 Ca 依赖性激活阈值水平的 NMDARs。这与 KCl 刺激产生的快速去极化相比延迟了几秒钟。我们的数据深入了解了偏头痛中 CSD 起始的潜在机制。