Ginkgo biloba abolishes aggression in mice lacking MAO A.

Mice deficient in monoamine oxidase A (MAO A) have increased brain levels of serotonin (5-HT) and norepinephrine and show enhanced aggression. We used MAO A knock-out (KO) mice as a model to study the effect of ginkgo biloba (EGb) on aggression. When EGb was administered to MAO A KO mice, their aggressive behavior in resident-intruder confrontations was reduced to levels seen in wild types. EGb did not affect the locomotive behavior of MAO A KO mice, which suggests that its effects on aggression were not due to sedation. EGb caused a significant 16.9% decrease in [3H]ketanserin binding to 5-HT2A receptors in the frontal cortex of MAO A KO mice but did not change the receptor affinity for [3H]ketanserin. This suggests that the antiaggressive effect of EGb may be mediated by 5-HT2A receptors and that EGb may be developed as a novel antiaggressive agent.