The study, published in Neural Regeneration Research, investigated the effects of Ginkgo biloba extract on the formation of neurones in rat brains after previous findings suggested that the Ginkgo biloba extract EGb 76 - which containing high levels of flavonoids and terpenoids - improves memory loss and cognitive impairments in patients with senile dementia.
Led by Jiwei Wang ofWeifang Medical University,China, the research teamused a rat model of vascular dementia to test the effects behavioural and physiological effects of supplementation with the extract - finding that rats given the EGb761 extract performed significantly better in tests of learning and memory and had significant growth of neural stem cells in certain brain regions.
"These experimental findings suggest that EGb761 enhances proliferation of neural stem cells in the subventricular zone and dentate gyrus, and significantly improves learning and memory in rats with vascular dementia," wrote Wang and his colleagues.
"EGb761 administration can regulate neural stem cell proliferation, migration and differentiation, and promotes cell proliferation and differentiation in rats with vascular dementia," they added.
The team reported that the extract promoted growth in both brain regions for up to four months - with peak growth occurring around one month after the model of vascular dementia was induced and supplementation had begun.
"This evidence suggests that there is an optimal phase (time-window) for promoting the proliferation of neural stem cells."
Wang and his team created the rat model of vascular dementia by repeatedly clipping and reperfusing the bilateral common carotid arteries of rats in combination with an intraperitoneal injection of a sodium nitroprusside solution. Seven days after establishing the model, rats were then supplemented with EGb761 at 50 mg/kg per day.
The rats learning and memory abilities were assessed during the trial using the Morris water maze, while proliferation of endogenous neural stem cells in the subventricular zone and dentate gyrus were labelled by 5-bromo-2-deoxyuridine immunofluorescence in all rats at 15 days, and 1, 2, and 4 months after model establishment.
EGb761 was found to significantly improve learning and memory in the rats, while immunofluorescence analysis showed that the number and proliferation of 5-bromo-2-deoxyuridine-positive cells in the subventricular zone and dentate gyrus of the was significantly higher for rats given the extract - meaning that the Ginkgo biloba led to a proliferation of neuronal stem cells in these areas.
The team said that their findings provide a new idea and approach to further explore the induced proliferation of neural stem cells in situ in the treatment of vascular dementia.
Source: Neural Regeneration Research
Volume 8, Issue 18, Pages 1655-1662, doi:10.3969/j.issn.1673-5374.2013.18.003
"A ginkgo biloba extract promotes proliferation of endogenous neural stem cells in vascular dementia rats"
Authors: Jiwei Wang, Wen Chen, Yuliang Wang