Objective To investigate the ultrastructural basis underlying electroacupuncture(EA) induced improvement of Alzheimer disease(AD) in transgenic mice.Methods Twelve APP 695 V 717 I transgenic mice were randomly divided into model group and EA group;and other 6 negative transgenic mice(C 57 BL/6 J) were made up of normal control group.After 3 months treatment by EA(15 min per other day

2 Hz/100 Hz

3-4 mA) applied to "Baihui"(GV 20) and "Yongquan"(KI 1)

the learning and memory ability of mice was measured by Lashley Ⅲ water maze test

and the ultrastructural changes of hippocampal CA 1 region was observed by electronic microscopy.Results The swimming escape latency and the number of navigating errors(dead-end forward swimming) in model group were significantly longer and more than those in normal control group(P<0.05);and those in EA group were considerably shorter and fewer than those in model group(P<0.05)

suggesting an improvement of learning-memory ability after EA.Comparison of the ultrastructure of the neurons in the hippocampal CA 1 region showed swelling of the mitochondria

broken or disappearance of the mitochondrial cristae

degeneration of the synapses

breakage and vague outline of the basement membrane of the blood capillaries in mice of model group;and basically distinct outline of the mitochondrial cristae and microvessels

and more synaptic vesicles in EA group.Conclusion EA may effectively improve the learning-memory capacity of the APP transgenic AD mice and alleviate the pathological changes of neurons of the hippocampal CA 1 region

which may be one of the mechanisms underlying the improvement of AD by EA.