The Protective Effect Of IGF-2 On Plasticity Of Visual Cortex And Visual Function In Monocular Deprivation Mice

Objective: To investigate the dynamic changes of IGF-2 in visual cortex during the critical period of visual development in mice and the effect of IGF-2 on the expression of SYN1、SYP、PSD95 and visual function in visual cortex of monocular deprivation miceMethods :(1)Kunming male mice aged 3 weeks after birth were randomly divided into 3 groups: the beginning of critical period of plasticity group(P3W group),the peak of critical period of plasticity group(P5W group),and the end of critical period of plasticity group(P7W group)were fed with 12 mice in each group.Each group was fed to3 W,5W and 7W in the same environment,and then the changes of IGF-2in visual cortex during visual development of mice were detected by Western blot and Immunohistochemistry.(2)Kunming male mice aged 3weeks after birth were randomly divided into 4 groups: normal control group(Nor),monocular deprivation group(MD),monocular deprivation+IGF-2 recombinant protein group(MD+IGF-2),monocular deprivation+ fluoxetine group(MD+FLX),monocular deprivation + fluoxetine group(MD+FLX),The MD group,MD+IGF-2 group and MD+FLX group were treated with right eyelid suture for 2 weeks at the beginning of 3 weeks of age,The MD+IGF-2 group was intraperitoneally injected with recombinant IGF-2 protein during monocular deprivation,The MD+FLX group was fed with fluoxetine in drinking water after eyelid opening.Mice in each model group were opened their eyelids at the end of 5 weeks,and visual acuity was detected by forepaw touchdown reflex experiment,and objective visual function was detected by flash visual evoked potentials.The expressions of SYN1,SYP and PSD95 in the visual cortex(the opposite side of the deprived eye)of mice were detected by western blot.Results :(1)The expression level of IGF-2 in the visual cortex was significantly upregulated during the critical period of visual development(P < 0.05).(2)The results of synaptic plasticity related proteins: Western blot showed that the protein expression levels of SYN1,SYP and PSD95 in MD group were all significantly lower than those in Nor group(P <0.05),the protein expressions of SYN1,SYP and PSD95 in visual cortex of MD+IGF-2 group were all significantly higher than those in MD group(P < 0.05),and there was no statistical significance in the protein expressions of SYN1,SYP and PSD95 in MD+IGF-2 group compared with those in Nor group and MD+FLX group(P > 0.05).(3)The visual acuity test results: At the end of 5 weeks of age,eyes deprivation was opened in each model group for detection,the MD group is lower than the Nor group(P < 0.05),MD + IGF-2 group was obviously higher than MD group(P < 0.05)and compared with Nor group and no statistical difference(P > 0.05).(4)The flash visual evoked potentials results: the P2 wave amplitude of F-VEP in MD group was significantly lower than that in Nor group(P < 0.05),the P2 wave amplitude of F-VEP in MD+IGF-2group was significantly higher than that in MD group(P < 0.05).Compared with that in Nor group,the P2 wave amplitude of F-VEP in MD+IGF-2 group was not statistically significant(P > 0.05);there was no statistical difference in P2 wave latency of F-VEP in the right eye of mice(P > 0.05).Conclusion :(1)IGF-2 protein was expressed in the mouse visual cortex at the beginning of the critical period of plasticity group(3W),the expression of IGF-2 in the visual cortex of normal developing mice during the critical period showed a developmental change with the increase of weeks of age,which was age-dependent.(2)During the critical period,monocular deprivation mice were given exogenous IGF-2 can maintain the plasticity of visual cortex and protect the visual function to a certain extent.