Oral treatment with the Ginkgo biloba extract EGb 761® prevents sodium azide-induced memory deficits in rats

EGb 761® is a special extract from leaves of Ginkgo biloba L. and is one of the most popular herbal medicines in the world. Its therapeutic use includes the treatment of cognitive impairment and neuropsychiatric symptoms in dementia. Alzheimer's disease (AD) is a neurodegenerative disorder that accounts for 50 – 70% of all cases of dementia. Although the etiology of the disease is still unknown considerable evidence suggests the involvement of mitochondrial damage. Reduction of mitochondrial complex IV activity mimics pathological processes involved in AD and can be evoked in rats by chronic administration of sodium azide (NaN3). In fact, chronic infusion of NaN3 for one month via subcutaneously implanted osmotic minipumps induced deficits in learning performance of rats in the passive avoidance paradigm (PA). In comparison to control rats, animals receiving NaN3 showed a significantly shorter latency time indicating a diminished potential to remember previous aversive stimuli. Daily concomitant oral administration of EGb 761® (25, 50 or 100 mg/kg) reversed the NaN3-induced learning deficit in the PA model which was statistically significant already for the lowest dose and was comparable to that of the acetylcholinesterase inhibitor donepezil (0.3 mg/kg/day).

Tab. 1: Effect of EGb 761® and donepezil on NaN3-induced cognitive impairment in rats as measured by the latency time (seconds) in the passive avoidance model

Dose (mg/kg, p.o.)	Vehicle + NaCl	Vehicle + NaN3	EGb 761® + NaN3	Donepezil + NaN3
0	180 ± 0	44 ± 29 *
0.3				145 ± 61 #
25			160 ± 56 #
50			147 ± 64 #
100			177 ± 7 #
* p < 0.05 vs. control group without NaN3; # p < 0.01 vs. vehicle group with NaN3

These results substantiate earlier experimental findings demonstrating neuroprotective activity of EGb 761® and support its therapeutic use in the prevention and treatment of AD.