Improvement of Synaptic Plasticity Injury of Alzheimer's Disease Rats by Electro-acupuncture at Different Frequency Through Regulating Protein and Phosphorylation Levels of GSK-3β / 广州中医药大学学报

ABSTRACT

Objective To investigate the mechanism of electro-acupuncture (EA) at different frequency in improving synaptic plasticity injury in Alzheimer's disease(AD) rats, and to provide the theoretical basis for the clinical application of electro-acupuncture for the treatment of AD. Methods Ninety Wistar rats were randomly divided into normal group, model group, sham-operation group, and 2 Hz, 30 Hz, 50 Hz acupuncture groups, 15 rats in each group. AD rat model was established by injection of amyloid β1-42 (Aβ1-42) into the lateral ventricle. The rats in EA groups were treated with EA on Baihui and Shenshu acupoints at different frequencies (2, 30, 50 Hz). Learning and memory ability and space exploration ability of rats in each group were measured by Morris water maze test. The synaptic ultrastructure of hippocampus was observed by transmission electron microscopy. Nerve fibers were stained using Golgi techniques. The protein and phosphorylation levels of glycogen synthase kinase 3 beta (GSK-3β) in the brain tissues were detected by Western blotting method. Results(1) Compared with the normal group, the average escape latency time in the model group was significantly prolonged (P < 0.05), and the number of platform crossing was significantly reduced (P < 0.05), indicating that AD model had been established successfully. The average escape latency of rats in EA groups was significantly shortened and the frequency of platform crossing was increased as compared with those of the model group (P < 0.05). (2) The synaptic morphology of the hippocampus showed that the anterior membrane, posterior membrane and the interspace of the synapses in the model group were blurred, and the membrane structures of synapses were incomplete and dissolved. But the synaptic ultrastructures of the 3 EA groups were improved.(3) In the model group, the neurofibrillary tangles were found in the brain tissue, while the neurofibrillary tangles were relieved and the nerve fibers became clear in EA groups.(4) The levels of GSK-3β and GSK-3β(pTyr216) in the model group were significantly higher than those in the normal group (P < 0.05), whearas the GSK-3β(pSer9) level was significantly down-regulated (P < 0.05). In the EA groups, the levels of GSK-3βand GSK-3β(pTyr216) were down-regulated, while GSK-3β(pSer9) level was increased with the frequency of EA, and there was significant difference compared with the model group (P<0.05). (5) Compared with 2 Hz and 30 Hz EA groups, the number of plateau crossing, the average escape latency and the protein and phosphorylation levels of GSK-3β in 50 Hz EA group were significantly improved (P < 0.05). The improvement of synaptic morphology and neurofibrillary tangles of 50 Hz EA group was superior to that of the other 2 EA groups. Conclusion EA at different frequency can improve the learning and memory ability of AD rats, and the effect of 50 Hz is stronger. The therapeutic effect might be achieved by regulating the expression level of GSK-3βprotein and phosphorylation levels, which can improve synaptic plasticity damage of AD rats.