[Exploration of electroacupuncture at "Fengchi" (GB 20) and "Sishencong" (EX-HN 1) for attenuating learning and memory impairment in vascular dementia rats based on NMDAR/CREB/BDNF signaling pathway].

OBJECTIVE

To explore the mechanism of electroacupuncture (EA) at "Fengchi" (GB 20) and "Sishencong" (EX-HN 1) on learning and memory impairment in vascular dementia (VD) rats by observing the influences on the N-methyl-D-aspartate receptor (NMDAR)/cyclic adenosine monophosphate response element-binding protein (CREB)/brain-derived neurotrophic factor (BDNF) signaling pathway and the excitotoxicity induced by hippocampal calcium overload.

METHODS

Thirty-two male SD rats of SPF grade were selected and randomized into a normal group (6 rats), a sham-operation group (6 rats) and an operation group (20 rats). VD model was established with the modified Pulsinelli's four-vessel occlusion (4-VO) method. Twelve rats after successfully modeled were assigned randomly into a model group and an EA group, 6 rats in each one. In the EA group, EA was delivered at bilateral "Fengchi" (GB 20) and "Sishencong" (EX-HN 1), with the continuous wave, the frequency of 2 Hz and the electric current of 1 mA. Stimulation intensity was adjusted depending on the slightly trembling of rat head. EA was given once daily, 30 min each time; and EA intervention was delivered for 21 days continuously. Using Morris water maze test, the learning and memory function was assessed. The neuronal morphology in the hippocampal CA1 was observed with HE staining; the level of glutamate (GLU) in serum and hippocampal tissue, as well as the activity of calcium pump (Ca-ATP) in the hippocampus were detected using colorimetric method. The protein expression of NMDAR, calmodulin-dependent protein kinase Ⅱ (CaMKⅡ), phosphorylated calmodulin-dependent protein kinase Ⅱ (p-CaMKⅡ), phosphorylated cyclic phosphoradenosine effector element binding proteins (p-CREB), CREB, and BDNF in the hippocampal CA1 was detected using immunohistochemistry. The protein expression of NMDAR, CREB, p-CREB and BDNF in the hippocampal tissue was detected using Western blot method.

RESULTS

Compared to the sham-operation group, in the model group, the escape latency was prolonged and the platform crossing times of rats were reduced (<0.01), the hippocampal neuron structure was damaged to different degrees, the structure in hippocampal CA1 was loosened, the arrangement disorganized, with clear grid-like structure; the neuronal morphology was irregular, pyknosis and even dissolution occurred, glial cells increased, blood capillary was dilated and the inflammatory cells were infiltrated and scattered. The level of GLU in the serum and hippocampal tissue and the protein expression of hippocampal NMDAR were elevated (<0.01), the activity of Ca-ATP and the protein expression of CaMKⅡ, p-CaMKⅡ, CREB, p-CREB and BDNF were reduced (<0.01, <0.05); and the ratio of p-CaMKⅡ/CaMKⅡ and that of p-CREB/CREB were dropped (<0.05). In comparison with the model group, in the EA group, the escape latency was shortened and the platform crossing times of rats rose (<0.01), the arrangement was improved in the hippocampal CA1, the neuronal morphology was intact, the nucleoli were clear relatively and the pyknosis or dissolution were attenuated, the numbers of glial cells reduced relatively, the dilation of blood capillary was alleviated. The level of GLU in the serum and hippocampal tissue and the protein expression of NMDAR were reduced in the hippocampal tissue (<0.01), the activity of Ca-ATP and the protein expression of CaMKⅡ, p-CaMKⅡ, CREB, p-CREB and BDNF were elevated (<0.05, <0.01); and the ratio of p-CaMKⅡ/CaMKⅡ and that of p-CREB/CREB increased (<0.05).

CONCLUSION

EA at "Fengchi" (GB 20) and "Sishencong" (EX-HN 1) can attenuate learning and memory impairment in VD rats, which may be obtained by reducing GLU level in hippocampal tissue, inhibiting hippocampal excitotoxicity, mediating protein expression related to the NMDAR/CREB/BDNF signaling pathway, and maintaining neuronal survival and growth.