The Expression Of Synaptophysin And PSD-95 In The Visual Cortex Of Normal And Monocularly Deprived Rats

Objective:To study the expression of synaptophysin (SYN) and post-synaptic density 95 (PSD-95) in the visual cortex of normal and monocularly deprived rats,to provide the molecular mechanism of the visual plasticity at the level of synapse.Methods:35 14-day-old healthy Wistar rats were randomly divided into 7 groups:5 in every group,in which 1-4 groups for normal group (N), 5-7 groups for monocular deprivation group (MD).The eyelids of MD groups were sutured at 14 days to obtain animal model. Rats were housed in alike environment, the time for experiment at postnatal day 14,21,28,45.After anesthesia,perfusion,fixation and opening cranium,cut the posterior brain coronally (get the brain opposite to deprived eye in the rats of MD),putted it in fixative solution for 24-48h,then imbedded with paraffin routinely.Sliced the prepared tissue in 5μtm,carried out routine HE stain and immunohistochemistry stain, Observed the expression of SYN and PSD-95 in visual cortex under the light microscope. Pictures were Collectted with Olympus micro-image system,integrated optical density (IOD) were determined with image analysis system. Analyzed and compared the IOD, experiment data was indicated with mean±standard deviation.Analyzed data with SPSSll.5,adopted t -test innormal and visual deprivation groups,ANOVA in the different stages of same group, Pearson test in correlation the two protein expression.Results:1.HE stain resultsThe neurons of visual cortex in rats distributed in layers, from superficial to the deep layer there were molecular layer,external granular layer,external pyramidal layer,internal granular layer,internal pyramidal layer and polymorphous cell layer,the neurons in every layer lined in order.There was not obviously abnormality in the visual cortex of monocular deprivation group.2.The expression of SYN in rat visual cortex in different stagesIn light microscope,synaptophysin positive reaction product was yellow granulous,mainly located between neurons.Neuron cell body,blood vessel and callosum were not labeled.The synaptophysin positive granula were seen in every layer of visual cortex.The expression of synaptophysin increased developmentally in the normal groups. At P14 the IOD was 13.31±1.08,at P21 it increased to 26.52±1.88,afterward maintained at higher level.The expression of synaptophysin in visual cortex of monocular deprivation rats decreased,the IOD at P21 was 16.89±2.00 (t=10.755,P<0.05),17.16+0.79 atP28 (t=12.219,P<0.05),17.00±0.92 atP45(t=18.255,P<0.05).3.The expression of PSD-95 in rat visual cortex in different stagesIn light microscope,PSD-95 positive reaction product was brown,mainly located in cell body,dendrite and axone of neuron. The expression product could be found in every layer of visual cortex,but litter in molecular layer.The expression of PSD-95 increased developmentally in the normal groups.At P14 the IOD was 5.48±1.03,at P21 it increased to 12.47±2.06,10.54±1.72 at P28,and 11.65±1.55 at P45.There was not significant deviation in those three stages,the IOD maintained at higher level.The expression of PSD-95 in visual cortex of visual deprivation rats obviously decreased.At P21 the IOD was 4.94±0.57 (t=6.503,P<0.05),5.20+0.47 at P28 (t=7.637,P<0.05),and 4.87±0.72 at P45 (t=12.895,P<0.05).4.The correlation of the expression of SYN and PSD 95We analyzed the correlation of the expression of synaptophysin and PSD-95 in visual cortex of normal and visual deprivation rats respectively.The result showed that the expression of synaptophysin and PSD-95 in visual cortex of normal rats correlate positivly (r=0.756,P<0.05),the expression of synaptophysin and PSD 95 in visual cortex of visual deprivation rats correlate positivly (r=0.786,P<0.05).Conclusion:The expression of SYN and PSD-95 increased in P14-P21, the critical period of rats visual development was P14-P45.In early stages they came to peak,suggested that synaptophysin and PSD-95 may involve in the early development and mature of rat visual cortex.Further investigation indicated that the expression in visual cortex of visual deprivation rats at P21,P28 and P45 decrease obviously compared to normal groups.We supposed that SYN and PSD-95 may involve in regulation of neuron plasticity in visual cortex in critical period. The expression of SYN was correlated 4 with PSD-95,so the process of synaptic plasticity may be the result of unification and promotion between pre-synapse and post-synapse.