[Effect of Ginkgo biloba extract on memory deficits in radial maze performance induced by some drugs in rats].

Ginkgo biloba extract is widely used as a herbal medicine or dietary supplement in Europe, since Ginkgo biloba extract is effective in facilitation of learning and recollection of memories. However, little is known about the mechanism of the action of Ginkgo biloba extract on learning and memory enhancements. On the other hand, it is well known that cholinergic, histaminergic and glutamatergic systems play a crucial role in learning and memory in animals. Therefore, in order to elucidate the mechanism of Ginkgo biloba extract on memory, we studied and clarified the effect of Ginkgo biloba extract on spatial memory deficits induced by scopolamine, diphenhydramine or MK-801 using eight-arm radial maze performance. It was found that Ginkgo biloba extract improved the spatial memory deficits induced by scopolamine. Ginkgo biloba extract also caused repair to spatial memory deficits induced by diphenhydramine. On the other hand, no significant effect was observed with MK-801-induced spatial memory deficits. These findings suggest that the effect of Ginkgo biloba extract is mediated not only by the cholinergic system but also by the histaminergic system to induce learning and memory enhancements.