Electroacupuncture improves learning and memory impairment and enhances hippocampal synaptic plasticity through BDNF/TRKB/CREB signaling pathway in cerebral ischemia-reperfusion injury rats

Abstract

To observe the effect of electroacupuncture on brain-derived neurotrophin factor (BDNF) / tyrosine kinase receptor B (TRKB) / cyclic adenosine monophosphate response element binding protein (CREB) pathway, synaptic plasticity marker protein and synaptic ultrastructure in the hippocampus of rats with learning and memory impairment induced by cerebral ischemia reperfusion (IR), so as to explore its mechanisms underlying improvement of cognitive impairment after stroke. SD rats were randomly divided into blank, sham operation, model, and EA groups, with 12 rats in each group. The model of IR was established by occlusion of the middle cerebral artery. EA (2 Hz/10 Hz, 1-3 mA) was applied to "Shenting" (GV24) and "Baihui" (GV20) for 30 min, once daily for 14 days. The neurological function was evaluated according to the Zea Longa's score criteria. Morris water maze test was used to detect the learning and memory function of the rats. Nissl staining was used to observe the pathological morphology of the hippocampus. Transmission electron microscopy was used to observe the ultrastructure of the syna-pse in the hippocampus, the synaptic gap width and postsynaptic dense substance (PSD) thickness were measured. Immunofluorescence staining was used to observe the positive expression levels of BDNF, PSD-95 and synaptophysin (SYN) in hippocampal CA1 region. The protein expression levels of BDNF, TRKB, CREB, PSD-95, and SYN in hippocampal tissue were detected by Western blot. Compared with the sham operation group, the neurological function score and escape latency (EL) were significantly increased (P<0.01), the times of crossing the original platform were decreased (P<0.01), the number of neurons in the CA1 area of the hippocampus was reduced, with incomplete morphology, widened synaptic gaps and significantly decreased PSD thickness (P<0.01), the positive expressions of BDNF, PSD-95, SYN and the protein expression levels of BDNF, TRKB, CREB, PSD-95, SYN were significantly decreased (P<0.01) in the model group. Compared with the model group, the neurological function scores and EL on the 12th and 13th day were decreased (P<0.01, P<0.05), the times of crossing the original platform were increased (P<0.01), the morphology of hippocampal CA1 neurons improved, the synaptic gaps was decreased (P<0.01), the PSD thickness was significantly increased (P<0.01), the positive expressions of BDNF, PSD-95, SYN, and the protein expression levels of BDNF, TRKB, CREB, PSD-95, SYN were increased (P<0.05, P<0.01) in the EA group. EA can alleviate cognitive impairment in IR rats, which may be related to its function in up-regulating the proteins of BDNF/TRKB/CREB pathway, promoting the expressions of synaptic plasticity marker proteins PSD-95 and SYN, thus improving the synaptic plasticity.