The Impact Of Age And Monocular Deprivation On The Expression Of GluR2/3 Subunit Of AMPA Receptor In Visual Cortex Of Rats

ObjectiveObserve the impact of age and visual experience on the expression of GluR2/3 subunit of AMPA receptor in layerⅡ/Ⅲof visual cortex of rats in critical period of visual development,and discuss the possible mechanism of the action of GluR2/3 receptor in visual plasticity.Method1.25 healthy Wistar rats were randomly divided into 5 groups:NP7,NP14,NP21,NP28 and NP45,5 in each group,all were normal groups.All the rats were rearing in same environment,and the time for experiment was at the postnatal 7,14,21,28,45 days.After anesthesia,perfusion,fixation and opening cranium to get the whole brain tissure.Then put the brain tissure in 4℃4%paraformaldehyde to fix for a night.After that we transfered them into 4℃30%cane sugar to dehydration for 2 times.Then,imbedded the tissue with OCT,sliced the prepared tissue in 12μm frozen section,carried out routine HE stain and immunofluorescence histochemistry stain.We observed the expression of GluR2/3 subunit of AMPA receptor in layerⅡ/Ⅲof rat's visual cortex under the fluorescence microscope. Pictures were collectted with Olympus micro-image system.We measured the count and average optical density(AOD) of positive cells with image analysis system of IPP6.0.The experiment data was indicated with mean±standard deviation.We analyzed and compared the data with SPSS16.0,and adopted ANOVA to compare the parameters in different stages.2.15 healthy Wistar rats were randomly divided into 3 groups:MD21,MD28 and MD45,5 in each group.The eyelids of monocular deprivation groups were sutured at 14 days to obtain animal model.Rats were reared in same environment with normal groups(NP21,NP28 and NP45) in PartⅠ.The time for experiment was at postnatal 21,8,45 days.The laboratory precedure,collection of picture,analysis of the count and AOD of positive cells were all the same with PartⅠ. Independent-samples T test was adopted in the comparetion between the normal groups and monocular deprivation groups.Result1.HE stain results:The neurons of visual cortex in normal rats distributed in layers,the neurons in each layer lined in order.There was no obviously abnormality in visual cortex of monocular deprivation groups compared with normal groups.2.Immunofluorescence histochemistry stain:from the observation of the fluorescence microscope,the GluR2/3 immuno-positive reaction products take on green-fluorescence.GluR2/3 immuno-positive neurons were present in visual cortex of the rats in different ages.Viewing roughly,most of GluR2/3 immuno-positive neurons were present in layersⅡ/Ⅲof visual cortex;in layerⅠ,we see almost no immuno-positive neurons;layersⅣ,ⅤandⅥwere moderately expressed.The positive area was mostly located at the cell membrane and kytoplasm.3.We compared the positive cell count and AOD of different stages of GluR2/3 receptor in layerⅡ/Ⅲof visual cortex.Positive cell count:NP7 was 143.13±9.53,NP14 was135.20±9.47,NP21 was 150.40±8.19,NP28 was154.40±10.23,NP45 was 164.93±9.14.There was statistical significance of all the groups for ANOVA(P＜0.05).The AOD:NP7 was 0.0545±0.0107,NP14 was 0.0655±0.0118,NP21 was 0.0848±0.0114,NP28 was 0.0967±0.0147,NP45 was 0.1051±0.0152.There was statistical significance of all the groups for ANOVA(P＜0.05). We could see that the immuno-positive neurons and AOD in layerⅡ/Ⅲof visual cortex were increased with age.4.The expression of GluR2/3 receptor in layerⅡ/Ⅲof visual cortex of monocular deprivation rats was decreased.It shows that the count and AOD of GluR2/3 receptor were all decreased.Positive cell count:MD21 was 140.13±11.06; MD28 was 141.27±8.70;MD45 was 145.13±8.47.The AOD:MD21 was 0.0656±0.0120;MD28 was 0.0813±0.0111;MD45 was 0.0893±0.0137.We compared the count and AOD of GluR2/3 positive cells in layerⅡ/Ⅲof visual cortex between monocular deprivation groups and normal groups.There was statistical significance of both cell count and AOD of GluR2/3 receptor.Conclusion The expression of GluR2/3 receptor in layerⅡ/Ⅲof visual cortex take on the regularity of coherent with age development from 7 days postnatal to the end of critical period of visual development,so we speculate that the expression of GluR2/3 was related with the function and development of synapes,the phenomenon maybe one of important mechanisms of the development and plasticity of visual system. The expression of GIuR2/3 in monocular deprivation rats were less than in normal ones,so we speculate that monocular deprivation can prevent the increase of GluR2/3 receptor in critical period of visual development.The expression of GluR2/3 in visual cortex in critical period was regulated by visual experience,and abnormal visual experience can influence the function of visual cortex.