In vivo regulation of cerebral monoamine oxidase activity in senescent controls and chronically stressed mice by long-term treatment with Ginkgo biloba extract (EGb 761).

It is well recognized that Ginkgo biloba extract (EGb 761) exert beneficial effects against various age-related changes and is able to reduce the negative influence of stress. In view of the age-dependent increase in the activity of the B form of monoamine oxidase (MAO-B) and in view of the anti-stress action of EGb 761 hypothetically attributed to an inhibition of monoamine oxidase by this substance, we investigated the effects of long-term treatment with EGb 761 upon in vivo cerebral MAO-A and -B activities of stressed and unstressed 17- and 18-month-old mice. The stress was a 'chronic mild stress' regimen whose behavioral impact is known to be reduced by EGb 761. The results showed that: (1) EGb761 induced reductions in MAO activity in 18-month-old, but not in 17-month-old mice; the older animals having higher basal MAO activity; (2) in unstressed mice, EGb 761 appeared to reduce the age-induced increase in cerebral MAO activity; (3) MAO-A and -B activities of stressed and treated 18-month-old mice did not differ significantly from the levels observed in unstressed and untreated 17-month-old mice. These results may shed light on the anti-stress effects of Ginkgo biloba extract.