Effects of Gingko biloba extract on glutamate-induced ［Ca²⁺］_i changes in cultured cortical astrocytes after hypoxia/reoxygenation, H₂O₂ or L-glutamate injury

AimTo investigate glutamate-induced ［Ca²⁺］_i changes in cultured rat neonatal cortical astrocytes after hypoxia/reoxygenation, H₂O₂ or high concentration of L-glutamate injury. In the meantime, the effects of Gingko biloba extract (GbE) were examined. Methods［Ca²⁺］_i changes in astrocytes were monitored by laser scanning confocal microscopy with the Ca²⁺ sensitive fluorescent probe fluo-3. ResultsAfter astrocytes were impaired by hypoxia/reoxygenation, H₂O₂ (50 μmol·L^-1) or L-glutamate (0.25 mmol·L^-1), the exogenous glutamate (27 μmol·L^-1) could not induce increase of ［Ca²⁺］_i, but decrease by (3.3±1.6)%, (81±11)% and (81±7)%, respectively. Pretreatment with Gb<、i>E (10 mg·L^-1) could not improve injured astrocytic glutamate response. But after pretreatment with Gb<、i>E (100 mg·L^-1), glutamate-induced ［Ca²⁺］_i elevation of astrocytes after hypoxia/reoxygenation, H₂O₂ or high concentration of L-glutamate injury were (135±98)%, (117±93)% and (89±36)%, respectively. Nimodipine (1.6 mg·L^-1) could also reverse the abnormal response of astrocytes after different injury. ConclusionHypoxia/reoxygenation, H₂O₂ and high concentration of L-glutamate impaired astrocytes′ response to exogenous L-glutamate, and then bidirectional communication between astrocytes and neurons could not take place. Gb<、i>E could improve the abnormal responses and maintain the normal function of astroglical network. These effects support that GbE has potential beneficial actions against brain injury.