Effects of gingko biloba extract on glutamate-induced [Ca2+]i changes in cultured cortical astrocytes after hypoxia/reoxygenation, H2O2 or L-glutamate injury.
OBJECTIVE
To 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.


RESULTS
After astrocytes were impaired by hypoxia/reoxygenation, H2O2 (50 micromol x L(-1)) or L-glutamate (0.25 mmol x L(-)), the exogenous glutamate (27 micromol x L(-1)) could not induce increase of [Ca2+]i, but decrease by (3.3 +/- 1.6)%, (81 +/- 11)% and (81 +/- 7)%, respectively. Pretreatment with GbE (10 mg x L(-1)) could not improve injured astrocytic glutamate response. But after pretreatment with GbE (100 mg x 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 x L(-1)) could also reverse the abnormal response of astrocytes after different injury.


CONCLUSIONS
Hypoxia/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. GbE 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.
Li
Zhen
Z
Institute of Clinical Phannacology, Tongji Medical College of Huazhong University of Science and Technology, Wuhan 430030, China.
Lin
Xian-ming
XM
Gong
Pei-li
PL
Du
Guan-hua
GH
Zeng
Fan-dian
FD
D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D015687:Cell Hypoxia; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000378:metabolism; D004365:Drugs, Chinese Herbal / Q000302:isolation & purification / Q000494:pharmacology*; D020441:Ginkgo biloba / Q000737:chemistry; D018698:Glutamic Acid / Q000633:toxicity; D006861:Hydrogen Peroxide / Q000633:toxicity; D018515:Plant Leaves / Q000737:chemistry; D010946:Plants, Medicinal / Q000737:chemistry; D051381:Rats; D015427:Reperfusion Injury
D004365:Drugs, Chinese Herbal; D018698:Glutamic Acid; D006861:Hydrogen Peroxide; D002118:Calcium