Protective effects of Ginkgo biloba extract on rats during cerebral ischemia/reperfusion. 
To study the effect of Ginkgo biloba extract on rats during ischemia/reperfusion and its influence on intracellular calcium in hippocampal neurons.  Model of intraluminal occlusion of the middle cerebral artery (MCAO) was used to prepare the ischemia/reperfusion cortex tissue.  Concentration of MDA was determined by measuring thiobarbituric acid-reactive substance.  GSH-PX was quantified using the thiobarbituric acid (TBA) technique.  SOD was assayed througha xanthine method.  Endogenous amino acids were quantified by high performance liquid chromatographic (HPLC) analysis.  Primary culturs of hippocampal neurons were prepared for a free intracellular calcium ([Ca(2+)]I) assay by Fura-2 based single cell microfluoremetric technique.  Comparing control and treatment groups, the concentration of SOD and GSH-PX were higher, whereas that of MDA was much lower; the concentration of glutamate and aspartate decreased and that of GABA increased markedly at all time point (P < 0.01), Gly also decreased at some time points (P < 0.05).  The differences were significant between the groups of 10 mg/kg, 15 mg/kg and the groups of 5 mg/kg.  When 1 x 10(-5) mol/L glutamate was applied with 25 micro g/ml ginkgo biloba extract to cultured neurons, the increase in [Ca(2+)]I was lower than that caused by applying glutamate alone.  Its peak value was much lower and increased phase was longer, its declining phase was shorter.  After returning to baseline, the application of 1 x 10(-5) mol/L glutamate could induce the reaction to recover.  Ginkgo biloba extract could protect damaged neurons by keeping the balance of inhibitory/excitatory aminoacids, enhancing the free radical scavengers system, and inhibiting the effect of glutamate on [Ca(2+)]I.