Ouardouz Mohamed, Malek Sameh, Coderre Elaine, Stys Peter K
Division of Neuroscience, Ottawa Health Research Institute, 725 Parkdale Avenue, Ottawa, Ontario, Canada K1Y 4E9.
J Physiol. 2006 Nov 15;577(Pt 1):191-204. doi: 10.1113/jphysiol.2006.116798. Epub 2006 Aug 31.
Electrophysiological recordings of propagated compound action potentials (CAPs) and axonal Ca(2+) measurements using confocal microscopy were used to study the interplay between AMPA receptors and intracellullar Ca(2+) stores in rat spinal dorsal columns subjected to in vitro combined oxygen and glucose deprivation (OGD). Removal of Ca(2+) or Na(+) from the perfusate was protective after 30 but not 60 min of OGD. TTX was ineffective with either exposure, consistent with its modest effect on ischaemic depolarization. In contrast, AMPA antagonists were very protective, even after 60 min of OGD where 0Ca(2+) + EGTA perfusate was ineffective. Similarly, blocking ryanodine receptor-mediated Ca(2+) mobilization from internal stores (0Ca(2+) + nimodipine or 0Ca(2+) + ryanodine), or inositol 1,4,5-trisphosphate (IP(3))-dependent Ca(2+) release (block of group 1 metabotropic glutamate receptors with 1-aminoindan-1,5-dicarboxylic acid, inhibition of phospholipase C with U73122 or IP(3) receptor block with 2APB; each in 0Ca(2+)) were each very protective, with the combination resulting in virtually complete functional recovery after 1 h OGD (97 +/- 32% CAP recovery versus 4 +/- 6% in artificial cerebrospinal fluid). AMPA induced a rise in Ca(2+) concentration in normoxic axons, which was greatly reduced by blocking ryanodine receptors. Our data therefore suggest a novel and surprisingly complex interplay between AMPA receptors and Ca(2+) mobilization from intracellular Ca(2+) stores. We propose that AMPA receptors may not only allow Ca(2+) influx from the extracellular space, but may also significantly influence Ca(2+) release from intra-axonal Ca(2+) stores. In dorsal column axons, AMPA receptor-dependent mechanisms appear to exert a greater influence than voltage-gated Na(+) channels on functional outcome following OGD.
采用共聚焦显微镜对复合动作电位（CAPs）的电生理记录和轴突Ca(2+)测量，研究体外联合氧糖剥夺（OGD）大鼠脊髓背柱中AMPA受体与细胞内Ca(2+)储存之间的相互作用。在OGD 30分钟而非60分钟后，从灌注液中去除Ca(2+)或Na(+)具有保护作用。TTX在两种暴露情况下均无效，这与其对缺血性去极化的适度作用一致。相比之下，AMPA拮抗剂具有很强的保护作用，即使在60分钟OGD后，0Ca(2+) + EGTA灌注液无效时也是如此。同样，阻断ryanodine受体介导的细胞内储存Ca(2+)动员（0Ca(2+) + 尼莫地平或0Ca(2+) + ryanodine），或肌醇1,4,5-三磷酸（IP(3)）依赖性Ca(2+)释放（用1-氨基茚满-1,5-二羧酸阻断第1组代谢型谷氨酸受体、用U73122抑制磷脂酶C或用2-氨基乙氧基二苯硼酸（2APB）阻断IP(3)受体；每种情况均在0Ca(2+)中）均具有很强的保护作用，联合使用可在1小时OGD后实现几乎完全的功能恢复（CAP恢复率为97 +/- 32%，而在人工脑脊液中为4 +/- 6%）。AMPA可使常氧轴突中的Ca(2+)浓度升高，通过阻断ryanodine受体可使其大幅降低。因此，我们的数据表明AMPA受体与细胞内Ca(2+)储存的Ca(2+)动员之间存在一种新颖且惊人复杂的相互作用。我们提出，AMPA受体不仅可能允许Ca(2+)从细胞外空间内流，还可能显著影响轴突内Ca(2+)储存的Ca(2+)释放。在背柱轴突中，OGD后AMPA受体依赖性机制似乎比电压门控Na(+)通道对功能结果的影响更大。
