GINKGO-BILOBA EXTRACT (EGB 761) INDEPENDENTLY IMPROVES CHANGES IN PASSIVE-AVOIDANCE LEARNING AND BRAIN MEMBRANE FLUIDITY IN THE AGING MOUSE

Decreases in cell membrane fluidity may be a major mechanism of age-re lated functional decline. A prime cause for the decline of membrane fl uidity may be the presence of free radicals. Gingko biloba extract EGb 761 protects neuronal cell membranes from free radical damage in vitr o. Further, EGb 761 has repeatedly been shown to improve cognitive fun ctions in man and in laboratory animals. To test if there is a link be tween these two actions we assessed the effects of EGb 761 on passive avoidance learning and on neuronal membrane fluidity in vivo in young (three-month-old), middle-aged (12-month-old) and aged (22 to 24-month -old) female NMRI mice. The animals were treated daily with 100 mg/kg EGb 761 for three weeks. There was a significant improvement in short- term memory, measured by the avoidance latency 60 seconds after the av ersive stimulus (p < 0.0311), and of membrane fluidity(p < 0.01) in th e aged animals, but no improvement in long-term memory as measured by the avoidance latency 24 hours after shock. However, no significant co rrelation between membrane fluidity and short-term memory performance was found. Taken together, these results indicate that EGb 761 indepen dently improves changes in passive avoidance learning and brain membra ne fluidity.