Nakamura K, Hatakeyama T, Furuta S, Sakaki S
Department of Neurosurgery, Ehime University School of Medicine, Japan.
Brain Res. 1993 Jun 11;613(2):181-92. doi: 10.1016/0006-8993(93)90898-w.
To examine the role of calcium influx in the early phase after brief forebrain ischemia and subsequent delayed neuronal cell death in the hippocampus, 45Ca autoradiography and electron microscopic cytochemistry, by a combined oxalate-pyroantimonate method, were carried out in gerbil brains after 5 min bilateral common carotid arterial occlusion. Further, neuronal damage during the ischemic and postischemic periods was determined by conventional or immunohistochemical staining for microtubule-associated protein 2 (MAP2) with and without calcium-entry blockers. 45Ca autoradiography showed a high peak of calcium in the hippocampus at 5 min of recirculation. Electron cytochemical microscopy also demonstrated accumulation of intracellular calcium pyroantimonate deposits in the neuronal cells in all regions. At 30 min of reperfusion, amounts of calcium in the hippocampus returned to the control levels, and intracellular dense calcium pyroantimonate deposits were reduced in these areas. Loss of the reaction for MAP2 was noted in the medial CA1 of the hippocampus immediately after 5 min ischemia and at 5 and 30 min after reperfusion. MK-801 (10 mg kg-1), an N-methyl-D-aspartate (NMDA) receptor antagonist, injected intraperitoneally 1 h before ischemia, suppressed the early increase of calcium in the forebrain and neuronal cell necrosis in the CA1. However, neither injection of MK-801 30 min after reperfusion nor preischemic treatment with 0.5 mg kg-1 Nimodipine or 1 mg kg-1 Nicardipine, voltage-sensitive calcium channel antagonists, prevented neuronal death. In immunohistochemical staining for MAP2, the ischemic lesion in the medial CA1 maintained after 5 min ischemia and the subsequent early reperfusion period in the untreated brains was protected by the preischemic injection of 10 mg kg-1 MK-801, but was not restored by the injection of 0.5 mg kg-1 Nimodipine or 1 mg kg-1 Nicardipine. In conclusion, it is suggested that an early excess of calcium influx could be caused mainly by excitatory amino acid overload through NMDA receptor-mediated calcium channels during the ischemic and early postischemic periods.
为研究短暂性前脑缺血后早期钙内流以及随后海马区延迟性神经元细胞死亡中的作用，采用草酸盐 - 焦锑酸盐联合法进行了⁴⁵Ca放射自显影和电子显微镜细胞化学检测，检测对象为沙土鼠脑在双侧颈总动脉闭塞5分钟后的情况。此外，通过对微管相关蛋白2（MAP2）进行常规或免疫组织化学染色，在有或没有钙通道阻滞剂的情况下，测定缺血期和缺血后期的神经元损伤。⁴⁵Ca放射自显影显示再灌注5分钟时海马区钙含量出现高峰。电子细胞化学显微镜检查也证实所有区域的神经元细胞内均有焦锑酸钙沉积物积累。再灌注30分钟时，海马区钙含量恢复至对照水平，这些区域细胞内致密的焦锑酸钙沉积物减少。缺血5分钟后以及再灌注5分钟和30分钟时，海马内侧CA1区出现MAP2反应缺失。缺血前1小时腹腔注射N - 甲基 - D - 天冬氨酸（NMDA）受体拮抗剂MK - 801（10毫克/千克）可抑制前脑钙的早期增加以及CA1区神经元细胞坏死。然而，再灌注30分钟后注射MK - 801，或缺血前用0.5毫克/千克尼莫地平或1毫克/千克尼卡地平（电压敏感性钙通道拮抗剂）处理，均不能预防神经元死亡。在MAP2免疫组织化学染色中，缺血前注射10毫克/千克MK - 801可保护未处理脑在缺血5分钟及随后早期再灌注期内侧CA1区的缺血性损伤，但注射0.5毫克/千克尼莫地平或1毫克/千克尼卡地平不能使其恢复。总之，提示在缺血期和缺血后早期，早期过量的钙内流可能主要由兴奋性氨基酸通过NMDA受体介导的钙通道过载引起。
