[Effect of transcutaneous electrical acupoint stimulation on learning and memory ability of chronic fatigue syndrome rats and its mechanisms].

Objective: To observe the effect of transcutaneous electrical acupoint stimulation (TEAS) on the histomorphological manifestations of hippocampal CA1 region and the expression of extracellular regulatory protein kinase (ERK), cyclic adenosine response element binding protein (CREB) and brain-derived neurotrophic factor (BDNF) in chronic fatigue syndrome (CFS) rats, so as to explore the mechanisms of TEAS in improving the learning and memory abilities of CFS rats.

Methods: Forty male Wistar rats were randomly divided into normal group (10 rats) and modeling group (30 rats); then after modeling, they were selected and randomly divided into model group (10 rats) and TEAS group (10 rats). CFS rats model was prepared by sleep deprivation combined with weight-bearing swimming. Rats in the TEAS group were stimulated with Han's acupoint nerve stimulator at bilateral "Zusanli" (ST36) and "Shenshu" (BL23) (2 Hz/15 Hz, 1-2 mA), 20 min each time, once a day for 4 weeks with 1 d rest every 6 d. The score of general conditions of rats was evaluated. The learning and memory ability was tested with Morris water maze. The morphology and ultrastructure of hippocampal CA1 region were observed by HE staining and transmission electron microscopy. The expression levels of ERK, CREB and BDNF mRNAs and proteins in hippocampus were detected by real time quantitative PCR and Western blot, respectively.

Results: Compared with the normal group, the score of general condition was increased (P<0.01); the escape latency was prolonged (P<0.05, P<0.01) and the times of crossing the original platform was decreased (P<0.05); the expression levels of ERK, CREB and BDNF mRNAs and proteins in hippocampus were decreased (P<0.05, P<0.01) in the model group. Compared with the model group, the scores of general condition on the 42^nd and 49^th day were decreased (P<0.05, P<0.01); the escape latency was shortened (P<0.01, P<0.05)and the times of crossing the original platform were increased (P<0.05); the expression levels of ERK, CREB and BDNF mRNAs and proteins in hippocampus were increased (P<0.01, P<0.05) in the TEAS group. The morphology of neurons in hippocampal CA1 region was normal in the normal group. In the model group, the number of neurons in hippocampal CA1 region decreased, the arrangement of nerve cells was scattered, the number of apoptotic cells increased, some nuclear structures disappeared, nuclear heterochromatin increased, the cell membrane wrinkled, the chromatin appeared empty bright area, and the crista was incomplete. Compared with the model group, the nerve cells morphology in hippocampal CA1 region was more regular, the number of apoptotic cells decreased, the chromatin and the cytoplasm were uniformly distributed, and the crista was relatively intact in the TEAS group.

Conclusion: TEAS can improve the learning and memory ability of CFS rats, the mechanisms may be related to improving the neural structure of hippocampal CA1 region and up-regulating the expression levels of ERK/CREB/BDNF.