[Effect of electroacupuncture combined with Donepezil on learning-memory ability and expression of hippocampal β-amyloid clearance-related genes in SAMP8 mice].

Objective: To investigate the effect of electroacupuncture (EA) combined with Donepezil on learning-memory ability and gene expression of β-amyloid (Aβ) clearance-related factors in the hippocampus in senescence-accelerated mouse prone 8 (SAMP8) mice, so as to explore their synthetic effect in improving dementia of Alzheimer's disease (AD)．.

Methods: Male SAMP8 mice (30-week-old) were randomly divided into model, medication and EA＋medication groups (＝6 mice in each group), and other 6 senescence-resistant 1 (SAMR1) mice were used as the control group. Mice of the medication and EA＋medication group received gavage of Donepezil (1.3 mg•kg•d) once daily for 4 weeks. EA (2 Hz, 1 mA) was applied to "Baihui"(GV20) and "Yintang" (EX-HN3) for 15 min, once daily, 6 days a week for 4 weeks for rats in the EA＋medication group. The Morris water maze (MWM) task (including place navigation tests and space exploration trials) was used to assess the mouse's learning-memory ability. Histopathological changes of hippocampus tissue were observed by H．E. staining. The expression levels of matrix metalloprotein 9 (MMP-9), low density lipoprotein receptor-related protein-1 (LRP-1), P-glycoprotein (Pgp, an important drug transporter responsible for multidrug resistance), Claudin-5 (a component of tight junction strands that serves as a physical barrier to prevent solutes and water from passing freely through the paracellular space between epithelial or endothelial cell sheets of blood-brain barrier, BBB) and Aβ mRNAs of the hippocampus tissue were detected by quantitative real-time PCR.

Results: Compared with the control group, the average escape latency of place navigation tests, and the expression levels of MMP-9 and Aβ mRNAs were significantly increased (<0.01), and the number of platform quadrant-crossing times of space exploration trials, and the expression levels of LRP-1, Pgp and Claudin-5 mRNAs considerably decreased in the model group (<0.01). After the intervention, the learning-memory ability was significantly improved in the medication and EA＋medication groups (<0.01，<0.05), the expression levels of Aβ mRNAs in the medication and EA＋medication groups and MMP-9 mRNA in the EA＋medication group were obviously down-regulated (<0.01), and those of LRP-1 and Pgp mRNAs in the medication and EA＋medication groups and Claudin-5 mRNA in the EA＋medication group were remarkably up-regulated (<0.05, <0.01). The therapeutic effect of EA＋medication was apparently superior to that of simple medication in shortening the escape latency (<0.05，<0.01) and in down-regulating the expression of MMP-9 and Aβ mRNAs(<0.01), and in increasing the number of platform quadrant-crossing times(<0.01), and expression levels of LRP-1, Pgp and Claudin-5 mRNAs (<0.01). H．E. staining showed scatted and loose arrangement of neurons in the hippocampus, with reduction of number of cell layers and unclear nucleoli, which was relatively milder in the medication and EA＋medication groups.

Conclusion: EA can enhance the effect of Donepezil in improving learning-memory ability in AD mice possibly by regulating expression of MMP-9, LRP-1, Pgp and Claudin-5 mRNAs and strengthening the effect of Donepezil in transporting Aβ via BBB.