[Electroacupuncture improves learning-memory ability following cerebral ischemia-reperfusion in rats by regulating mitochondrial fission/fusion of hippocampal neurons].

OBJECTIVES: To observe the effect of electroacupuncture (EA) on mitochondrial fission/fusion in rats with learning-memory impairment induced by cerebral ischemia-reperfusion (CI/R), so as to explore its potential neuroprotective mechanisms against the ischemic reperfusion injury of hippocampal neurons.

METHODS: Male SD rats were randomly divided into normal, sham-operation, model, and EA groups, with 12 rats in each group. The CI/R model was established by middle cerebral artery occlusion and reperfusion by using the intraluminal suture method. After successful modeling, rats in the EA group received EA (2 Hz/10 Hz, 6 V) at "Shenting"(GV24) and "Baihui" (GV20) for 30 min, once daily for 14 consecutive days. The rats' learning-memory ability was evaluated using the novel object recognition test and Morris water maze test. The cerebral infarct volume was assessed by 2, 3, 5-triphenyltetrazolium chloride (TTC) staining. Hippocampal neuronal morphology was examined by HE staining, and the mitochondrial morphology and structure of hippocampal neurons were observed using transmission electron microscopy. The adenosine triphosphate (ATP) content in the hippocampal tissue was measured using colorimetry, and mitochondrial DNA (mtDNA) copy number was detected by qPCR. The relative protein and mRNA expression levels of mitochondrial fusion proteins 1/2 (MFN1/2), optic atrophy protein 1 (OPA1), dynamin-related protein 1 (DRP1), and fission protein 1 (FIS1) in the hippocampal tissue were detected by Western blot and qPCR respectively.

RESULTS: No significant differences were found between the normal and sham-operation groups in all the indices. Compared with the sham-operation group, the model group exhibited a significant increase in the escape latency of Morris water maze test from the 3rd to the 5th day, brain infarction volume, expression levels of DRP1 and FIS1 protein and mRNA (P<0.01, P<0.05), and a significant decrease in the novel object recognition index, crossing number of the original target platform in Morris water maze test, copy number of mtDNA, ATP content, and the expression levels of MFN1, MFN2, and OPA1 protein and mRNA (P<0.01, P<0.05). In comparison with the model group, both the increased levels of the escape latency, brain infarction volume, expressions of DRP1 and FIS1 protein and mRNA, and the decreased levels of the novel object recognition index, crossing number of the original target platform, copy number of mtDNA, ATP content, and the expressions of MFN1, MFN2, and OPA1 protein and mRNA were reversed in the EA group (P<0.01, P<0.05). Histological examination showed that in the model group, the hippocampal neurons were loosely arranged, with extensive vacuolar degeneration and necrosis, swollen and ruptured mitochondria, irregular mitochondrial membrane, and disappearance of cristae, while in the EA group, hippocampal neurons were closely arranged and relative intact in the morphology, with relatively complete mitochondria, and clear cristae.

CONCLUSIONS: EA can improve the learning-memory ability in CI/R rats which may be related to its functions in inhibiting the mitochondrial fission and promoting mitochondrial fusion, thus maintaining mitochondrial function and structural stability.