Expression Of Psd-95in Visual Cortex Of Juvenile And Adult Rats With Monocular Form-deprivation Amblyopia

BackgroundAmblyopia is a common eye disease to seriously affect the development of visual function during the development of children, with the incidence being1%-5%. The pathogenesis of amblyopia is closely related to the neuronal synaptic development and plasticity of the visual system, synaptic plasticity is the central link of development of amblyopia. Postsynaptic density protein-95(PSD-95) can play a decisive role in controlling synapse maturation and activity-dependent synaptic plasticity, morphological studies have established that PSD-95may participate in the process of the early visual development, whereas, the special studies on the gene level is relatively less.ObjectiveTo observe the expression of PSD-95in the visual cortex of normal control rats and monocular form-deprivation amblyopia rats within the juvenile and adult period, and provide the theoretic foundation for exploring its role in the pathogenesis of amblyopia and finding out a new target in the treatment of amblyopia.MethodsⅠ Forty-eight SD rats aged14days old, male and female unlimited, were randomly divided into24monocular form-deprivation group(MD) and24normal control group (NC). The rats in the NC group were randomly divided into normal control Ⅰ group(NC Ⅰ) and normal control Ⅱ group(NC Ⅱ),12in every group; the rats in the MD group were randomly divided into monocular form-deprivation Ⅰ group(MD Ⅰ) and monocular form-deprivation Ⅱ group (MD Ⅱ),12in every group. For the MD groups, we sutured the unilateral eyelids of rats at14days to set up the monocular form-deprivation amblyopia animal model.2When all of the rats in the NC I group and MD I group were feeded to postnatal45days (P45, Juvenile period), contralateral visual cortex of deprivation eyes of twelve rats the MD Ⅰ group and the unilateral visual cortex of twelve rats from the NC Ⅰ group were taken in the same condition, the samples were marked by NCP45and MDP45; when all of the rats in the NC Ⅱ group and MD Ⅱ group were feeded to postnatal90days (P90, Adult period), the samples were taken as above and marked by NCP90and MDP90. In addition, we proved the MD model successful by pattern visual evoked potential (P-VEP).3Carry out Nissl’s staining to observe the neural morphological change and recognize the realm and border of the visual cortex,and use immunohistochemistry staining and reverse transcription-polymerase chain reaction (RT-PCR) to investigate the expression of PSD-95protein and mRNA in the visual cortex of the four different groups.4The microscope, photograthy microscope, computer image analysis were used to get the data:the average optic density(AOD) of PSD-95and the PSD-95mRNA quantity, which were analyzed with SPSS12.0statistical analysis software, and were measured by mean and standard deviation(x±s),compare difference between groups in the same visual development period by paired-sample t test, difference between groups in the different visual development periods by analysis of variance.Results1P-VEP detection:Normal rats have steady waveforms, latency and amplitude.In the juvenile and adult period, contrasted to normal eyes of NC groups and undeprived eyes of MD groups, the P waves of deprived eyes of MD groups were prolonged in latency declined in amplitude, and had instability waveforms, the differences were significant(P<0.05). There were no significant differences between normal eyes of NC groups and undeprived eyes of MD groups(P>0.05).2Nissl’s staining results:visual cortex neurons were vesicular, distributed widely in every layer of visual cortex.The cytoplasm stained and nuclear not shaded. The six layers of visual cortex can be distinguished easily, from superficial to the deep layer were molecular layer(I),external granular layer(II), external pyramidal layer(III), internal granular layer(IV),internal pyramidal layer(V) and polymorphous cell layer(VI). Compared with NC groups, there were not obviously abnormality in the visual cortex of MD group.3Result of immunohistochemistry:In light microscope, PSD-95positive reaction products were brown, mainly located in cell body of neuron, and widely distributed in the each layer, but less in molecular layer. In NC groups, the AOD in NCP45group was0.397±0.008, in NCP90group was O.318±0.007,and difference between the two groups was obvious(F1=441.993, P<0.05); Contrasted to the NC groups, the expression of PSD-95protein in visual cortex of MD rats both were remarkable reduced,the AOD in MDP45group was0.352±0.005, in MDP90group was0.259±0.011, and the differences were significant(t45=22.650, P<0.01、t90=10.547, P<0.01). Moreover, difference of the expression of PSD-95protein between the MDP45group and the MDP90group was significant (F3=474.793, P<0.05).4The expression of PSD-95mRNA in visual cortex:In NC groups, the PSD-95/β-actin ratio of NCP45group and NCP90group were0.667±0.009and0.399±0.019, difference between the two groups was obvious (F1=468.810, P<0.05); In MD groups, the expression of PSD-95mRNA was obviously less than that in normal control groups, at MDP45the PSD-95/β-actin ratio was0.470±0.005(t45=42.707, P<0.01), at MDP90was0.350±0.005(t90=,5.118P<0.05); Moreover, difference of the expression of PSD-95mRNA between the MDP45group and the MDP90group was significant (F2=990.992, P<0.05).Conclusion1In the sensitve period of visual development, the activity-dependent visual experience may regulate the expression of PSD-95by participating in the connection of synapses between neurons in visual system, that is to say, PSD-95is possibly one of the molceular biology basis of amblyopia; 2Monocular form-deprivation affect the expression of PSD-95in visual cortex of adult rats, it may concloude that a certain degree of synaptic plasticity still retain in adult visual cortex.3In normal control groups, the expression of PSD-95in the visual cortex of adult rats was less than that in juvenile rats. The result indicated that the age factor effect the expression of PSD-95.