Vornov J J
Cerebrovascular Program, Johns Hopkins School of Medicine, Baltimore, Maryland, USA.
J Neurochem. 1995 Oct;65(4):1681-91. doi: 10.1046/j.1471-4159.1995.65041681.x.
In some animal models of reversible ischemia, there is a therapeutic window during early recovery when glutamate receptor antagonists can rescue neurons from injury. We have previously reported that organotypic cultures of the hippocampus can be protected by NMDA-receptor antagonists during recovery from a brief period of simulated ischemia. To model ischemia, we have used potassium cyanide to inhibit oxidative metabolism and 2-deoxyglucose to inhibit glycolysis. To study the time course and mechanisms of delayed NMDA-receptor toxicity in more detail, we have extended these studies to dissociated cortical cultures. Injury was assessed by release of lactate dehydrogenase into the culture medium. Metabolic inhibition for 15 min caused dose-dependent injury. Morphologic signs of neuronal toxicity were delayed until the recovery period. MK-801 reduced injury significantly when present throughout the experiment. Surprisingly, MK-801 provided the same protection when administration was delayed until after the end of the metabolic inhibition, blocking NMDA receptors only during recovery. To examine NMDA toxicity during metabolic inhibition, the competitive NMDA-receptor antagonist 3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid was added during exposure. The protective effect of NMDA-receptor blockade was completely lost if the antagonist was removed during 1 min of continuing selective inhibition of oxidative metabolism. The toxic potency and effectiveness of glutamate were enhanced during metabolic inhibition, showing that receptors were not inactivated by simulated ischemia. These results are consistent with the specific hypothesis that return of oxidative metabolism triggers a critical period of toxic NMDA-receptor activation.
在一些可逆性缺血的动物模型中，早期恢复阶段存在一个治疗窗，在此期间谷氨酸受体拮抗剂能够挽救神经元免受损伤。我们之前曾报道，海马体的器官型培养物在从短暂的模拟缺血中恢复的过程中可受到NMDA受体拮抗剂的保护。为模拟缺血，我们使用氰化钾抑制氧化代谢，并使用2-脱氧葡萄糖抑制糖酵解。为更详细地研究NMDA受体延迟毒性的时间进程和机制，我们将这些研究扩展至解离的皮质培养物。通过检测培养基中乳酸脱氢酶的释放来评估损伤情况。代谢抑制15分钟会导致剂量依赖性损伤。神经元毒性的形态学迹象会延迟至恢复期出现。在整个实验过程中存在MK-801时，可显著减轻损伤。令人惊讶的是，当给药延迟至代谢抑制结束后，MK-801仍能提供相同的保护作用，仅在恢复期间阻断NMDA受体。为检测代谢抑制期间的NMDA毒性，在暴露期间添加竞争性NMDA受体拮抗剂3-(2-羧基哌嗪-4-基)丙基-1-膦酸。如果在持续选择性抑制氧化代谢的1分钟内移除拮抗剂，NMDA受体阻断的保护作用会完全丧失。在代谢抑制期间，谷氨酸的毒性效力和作用增强，表明受体并未因模拟缺血而失活。这些结果与氧化代谢恢复触发NMDA受体毒性激活关键期这一特定假说是一致的。
