Regulatory effect of electroacupuncture on visual cortex plasticity in adult amblyopic mice and its mechanism

Objective  To investigate the regulatory effect of electroacupuncture on visual cortex plasticity in adult amblyopic mice and its mechanism.

Methods  Forty-eight SPF male healthy 3-week-old Kunming mice were randomly divided into a normal control group, a monocular form deprivation (MD) group, and an electroacupuncture intervention group by the random number table method, with 16 mice in each group.Except for the normal control group, mice in the other groups had their right eyelids sutured for two weeks to establish an adult MD amblyopia model.The electroacupuncture intervention group received electroacupuncture stimulation at three acupoints, Taiyang (EX-HN5), Jingming (BL1), and Fengchi (GB20) for four weeks at five weeks of age.The subjective visual function (paw probing success rate) of each group of mice was measured at five and nine weeks of age, respectively.At nine weeks of age, the changes in flash-visual evoked potential (F-VEP) of mice in each group was detected.The expression of plasticity related proteins synaptophysin (SYP), synaptic protein 1 (SYN1), neurite overgrowth inhibitor A (Nogo-A), and Nogo receptor (NgR) proteins in the contralateral cortex of the deprived mouse eyes was detected by Western blot.Expression of early growth response gene 1 (Egr-1) in the visual cortex of mice was detected by immunohistochemical staining.This study was approved by the Animal Ethics Committee of Hunan Children’s Hospital (No.HCHDWLL-2022-17), and the management and use of animals were in accordance with the Laboratory Animal Management and Use Guide of Hunan Children’s Hospital.

Results  At nine weeks of age, the success rates of paw probing in the normal control group, MD group, and electroacupuncture intervention group were (71.69±10.60)%, (25.54±10.09)%, and (58.25±8.39)%, respectively, with a statistically significant overall difference ( F=5.987, P=0.006).Among them, the success rate of paw probing was significantly lower in the MD group than in the normal control group, and the electroacupuncture intervention group was significantly higher than in the MD group (both P<0.05).There was a significant overall difference in P2 wave amplitude in F-VEP examination among different groups of mice ( F=63.710, P<0.001), with lower P2 wave amplitude in the deprived eye of the MD group than in the normal control group and the electroacupuncture intervention group, and the differences were statistically significant (both P<0.001).There were significant differences in the expression levels of SYP and SYN1 proteins in the contralateral cortex of the deprived mouse eyes ( F=5.451, 3.871; both P<0.05).The relative expression levels of SYP and SYN1 proteins were significantly lower in the MD group than in the normal control group and electroacupuncture intervention group (all P<0.05).There were significant differences in levels of Nogo-A and NgR proteins in the contralateral cortex of the deprived mouse eyes ( F=4.188, 3.942, both P<0.05).The relative expression levels of Nogo-A and NgR proteins were significantly higher in the MD group than in the normal control group and the electroacupuncture intervention group (all P<0.05).The immunohistochemical staining results showed that compared with the normal control group, the MD group mice had a decrease in the expression of Egr-1 in the contralateral cortical neurons of the deprived eye, and the brown neuron protrusions were indistinguishable.Compared with the MD group, the electroacupuncture intervention group showed significant positive cell expression in the contralateral cortical area of the deprived eye, but the expression intensity was weaker than that of the normal control group.

Conclusions  Electroacupuncture treatment of Taiyang (EX-HN5), Jingming (BL1), and Fengchi (GB21) acupoints can reactivate the plasticity of the visual cortex in adult amblyopic mice and improve their visual function.The mechanism may be related to the regulation of Nogo-A/NgR signaling pathway.

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