Endocrine Abstracts (2009) 20 P560

Ovariectomy causes hippocampal neuronal loss and cognitive dysfunction and restored by Ginkgo biloba extract EGb761 in rats

Koji Koike1, Kazuhiro Takuma2, Yuki Hoshina1, Nobutaka Suzuki1, Masaki Inoue1 & Kiyofumi Yamada3


1Kanazawa University, Kanazawa, Japan; 2Osaka University, Osaka, Japan; 3Nagoya University, Nagoya, Japan.


Combination of ovariectomy (OVX) and chronic restraint stress causes cognitive dysfunction and reduces hippocampal CA3 neurons in female rats and that estrogen replacement suppresses the OVX/stress-induced behavioral and morphological changes. Aim of this study is to exsamine the effect of Ginkgo biloba extract (EGb 761) on the cognitive dysfunction and neuromorphological change in OVX/stress-subjected rats. Female Fisher 344 rats were randomly divided into three groups: vehicle-treated ovariectomized, EGb 761 (50 mg/kg)-treated ovariectomized and vehicle-treated sham-operated control groups. Two months after ovariectomy, all animals received restraint stress for 21 days (6 h/day), and were then subjected to a novel object recognition test followed by morphological examination by Nissl staining. EGb 761 was orally administered once daily until the behavioral analysis was done. Treatment with EGb 761 improved memory impairment and neuronal loss of hippocampus in the OVX/stress-subjected group in the same ways as 17-estradiol. On the other hand, EGb 761 did not affect the loss of bone mineral density and increase in body weight after OVX, although 17β-estradiol attenuated them. These results have important implications for neuroprotective and cognition enhancing effects of EGb 761 in postmenopausal women and suggest that the effects are mediated by a different mechanism from estrogen.

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