Pre-clinical and clinical studies have shown that the extract of the leaves of Ginkgo biloba has modest therapeutic potential as a cognitive enhancing drug. The pharmacology of Ginkgo biloba is complex due to its multiple active constituents. While Ginkgo biloba's cognitive enhancing effects have been attributed to its platelet-activating factor antagonistic effects and its free-radical scavenger activity, recent evidence suggests it may have direct effects on the cholinergic system which might explain both its acute and chronic cognitive enhancing effects. Ginkgo biloba's direct cholinergic actions include reduction of scopolamine-induced amnesia, modulation of pre-synaptic choline uptake and acetylcholine release, upregulation of post-synaptic muscarnic receptors and indirect effects on cholinergic function by modulation of the serotonergic system. The overall pharmacodynamic effect of Ginkgo biloba is likely due to a combination of platelet activating factor antagonistic effects, free radical scavenging activity and modulation of cholinergic function.
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