Sun David A, Sombati Sompong, Blair Robert E, DeLorenzo Robert J
Departments of Pharmacology and Toxicology, and the Graduate Program in Neuroscience, Virginia Commonwealth University, Richmond, Virginia 23298, USA.
Epilepsia. 2002 Nov;43(11):1296-305. doi: 10.1046/j.1528-1157.2002.09702.x.
Stroke is the most common cause of acquired epilepsy. The purpose of this investigation was to characterize the role of calcium in the in vitro, glutamate injury-induced epileptogenesis model of stoke-induced epilepsy.
Fura-2 calcium imaging and whole-cell current clamp electrophysiology techniques were used to measure short-term changes in neuronal free intracellular calcium concentration and long-term alterations in neuronal excitability in response to epileptogenic glutamate injury (20 microM, 10 min) under various extracellular calcium conditions and in the presence of different glutamate-receptor antagonists.
Glutamate injury-induced epileptogenesis was associated with prolonged, reversible elevations of free intracellular calcium concentration during and immediately after injury and chronic hyperexcitability manifested as spontaneous recurrent epileptiform discharges for the remaining life of the cultures. Epileptogenic glutamate exposure performed in solutions containing low extracellular calcium, barium substituted for calcium, or N-methyl-d-aspartate (NMDA)-receptor antagonists reduced the duration of intracellular calcium elevation and inhibited epileptogenesis. Antagonism of non-NMDA-receptor subtypes had no effect on glutamate injury-induced calcium changes or the induction epileptogenesis. The duration of the calcium elevation and the total calcium load statistically correlated with the development of epileptogenesis. Comparable elevations in neuronal calcium induced by non-glutamate receptor-mediated pathways did not cause epileptogenesis.
This investigation indicates that the glutamate injury-induced epileptogenesis model of stroke-induced epilepsy is calcium dependent and requires NMDA-receptor activation. Further, these experiments suggest that prolonged, reversible elevations in neuronal free intracellular calcium initiate the long-term plasticity changes that underlie the development of injury-induced epilepsy.
中风是后天性癫痫最常见的病因。本研究的目的是确定钙在中风诱发癫痫的体外谷氨酸损伤诱导癫痫发生模型中的作用。
采用Fura-2钙成像和全细胞膜片钳电生理技术，在不同细胞外钙条件下及存在不同谷氨酸受体拮抗剂的情况下，测量致痫性谷氨酸损伤（20微摩尔，10分钟）后神经元细胞内游离钙浓度的短期变化和神经元兴奋性的长期改变。
谷氨酸损伤诱导的癫痫发生与损伤期间及损伤后立即出现的细胞内游离钙浓度的长时间、可逆性升高相关，并且慢性兴奋性过高表现为培养物剩余存活期内的自发性反复癫痫样放电。在含有低细胞外钙、用钡替代钙或N-甲基-D-天冬氨酸（NMDA）受体拮抗剂的溶液中进行致痫性谷氨酸暴露，可缩短细胞内钙升高的持续时间并抑制癫痫发生。非NMDA受体亚型的拮抗作用对谷氨酸损伤诱导的钙变化或癫痫发生诱导没有影响。钙升高的持续时间和总钙负荷与癫痫发生的发展在统计学上相关。非谷氨酸受体介导途径诱导的神经元钙的类似升高不会导致癫痫发生。
本研究表明，中风诱发癫痫的谷氨酸损伤诱导癫痫发生模型是钙依赖性的，并且需要NMDA受体激活。此外，这些实验表明，神经元细胞内游离钙的长时间、可逆性升高启动了损伤诱导癫痫发展所依据的长期可塑性变化。
