银杏叶提取物在大鼠脑缺血再灌注损伤中的保护作用

目的：研究银杏叶提取物(GbE)对大鼠脑缺血再灌注损伤皮质内自由基、氨基酸动态平衡的影响及其对原代培养的大鼠海马神经元内游离钙离子浓度(Ca2+〕i)的影响和特征。方法：采用高压液相色谱仪测量大鼠大脑皮质中氨基酸(G1u、Asp，GABA、G1y)的浓度；MDA和GSH-Px采用TBA法测量，SOD采用嘌呤法测量。使用显微荧光检测系统检测单个原代培养的海马神经元内游离钙离子浓度(Ca2+)i)的变化和特征。结果：与非治疗组比较，GbE各浓度治疗组的缺血大脑皮质内G1u、Asp和MDA含量在各时间观察点(缺血3h、缺血再灌注lh和缺血再灌注2h)均明显降低(P＜0．0l或P＜0．05)，而SOD和GSH-Px含量则在各时间观察点均明显升高(P＜0．0l或P＜0．05)；GbE l0mg／kg、15mg／kg治疗组缺血大脑皮质内的GAGB和G1y含量在各时间观察点均有所降低(P＜0．05)。与GbE 5mg/kg治疗组比较，GbE l0mg/kg,15mg／kg治疗组大脑皮质内的G1u、Asp和MDA含量在各时间观察点较低(P＜0．05)，而GABA,Gly,SOD和GSH=Px含量则较高(P＜0．05)；GbE l0mg/kg治疗组与15mg／kg治疗组之间差异无显著性。当向原代培养的神经元同时给予谷氨酸l×l0—5mol／L和GbE 25μg／m120s时所诱导的Ca2+]i明显低于单独使用谷氨酸l×l0—5mol／L所诱导的Ca2+]i变化，其峰值明显下降，且在上升阶段其升高速度减慢，下降阶段的时间也有所缩短，二者之间的平台期相对延长，当其返回基线后，再次给予谷氨酸l×l0-5mol／L时，其反应可恢复。结论：GbE在大鼠脑再灌注损伤中可通过保持抑制性氨基酸／兴奋性氨基酸、自由基系统的平衡，及快速抑制谷氨酸诱导大鼠海马神经元内Ca2+]i浓度升高，从而保护受损的神经元。

Protective Effect of Ginkgo biloba Extract on Cerebral Ischemia/reperfusion Injury in Rats

OBJECTIVE: To study the effect of Ginkgo biloba extract (GbE) on dynamic equilibrium of free radicals and amino-acids in cortex of rats with cerebral ischemia/reperfusion (I/R) injury and its influence and characteristics to intracellular free calcium concentration (Ca2+]i) in primary cultured hippocampal neuron of rats. METHODS: Amino-acids were quantified by high performance liquid chromatographic (HPLC) analysis. Concentration of MDA and GSH-Px were determined by thiobarbituric acid (TBA) technique. SOD was assayed through xanthine method, and microfluoremetric technique was used to assay the change of Ca2+]i and its characteristics. RESULTS: Compared with the non-treated groups, at all time points (3 hrs after ischemia, 1 and 2 hrs after I/R separately), in the GbE treated groups, the levels of Glu, Asp and MDA were lower and SOD and GSH-Px were higher (P < 0.01 or P < 0.05), the GABA and Gly levels were lower in groups treated with middle (10 mg/kg) or high dosage (15 mg/kg) of GbE (P < 0.05). Compared with the group treated with small dosage GbE (5 mg/kg), Glu, Asp and MDA were lower and GABA, Gly, SOD and GSH-Px were higher in the groups treated with middle or high dosage of GbE (P < 0.05), while the difference in the latter two groups was insignificant. Level of Ca2+]i in cultured neurons treated with 1 x 10(-5) mol/L glutamate combined 25 micrograms/ml GbE for 20s was lower with lower peak value and longer time for reaching the peak than that in neurons treated with 1 x 10(-5) mol/L glutamate alone. Besides, the time of decline phase was also shorter in the former, so the flatform stage was prolonged. The response was recovered by re-applying of glutamate after Ca2+]i back to base line. CONCLUSION: GbE can protect damaged neurons through keeping the balance of inhibitory/excitatory amino-acids, enhancing free radicals scavengers system, and inhibiting the effect of glutamate to Ca2+]i.