Effect Of Reverse Suture Combined With Enriched Environment Intervention On The Reactivation Of Ocular Dominance Plasticity In The Visual Cortex Of Monocular Form-Deprived Adult Rats.

BackgroundAmblyopia is a common visual disorder that affect severely binocular function in the visual development. In recent years, the research of the visual neuron synaptic plasticity has become one of the hot spots of amblyopia pathogenesis research,The research mainly focus on amblyopia during the critical period,but less on amblyopia beyond the critical period, Studies found that the postsynaptic density protein-95(PSD-95) mingt regulate synaptic plasticity of visual cortex during the critical period and enriched environment intervention have a major impact on the reactivation of ocular dominance plasticity in the visual cortex of moncular form deprived adult rats.so far, it has not been reported that the expression rule of PSD-95in the visual cortex after the critical period,effect of monocular deprivation on it,the impact of reverse suture intervention and reverse suture combined with enriched environment intervention on moncular form-deprived adult rats,and the difference between reverse suture intervention and reverse suture combined with enriched environment intervention was statistically significant or not.ObjectiveIn the subject,we attempt to explore the expression change of PSD-95in the visual cortex of monocular form-deprived amblyopia rats after the critical period by the morphological and molecular level and the impact of reverse suture intervention and reverse suture combined with enriched environment intervention on it,and thus discuss effect of reverse suture intervention and reverse suture combined with enriched environment intervention on the reactivation of ocular dominance plasticity in the visual cortex of moncular form-deprived adult rats.Methods1. The14-day-old SD rats were randomly divided into eight groups:1-3groups’ are normal control group (NC),4-8groups are monocular deprivation group(MD).The right eyelids of MD groups were sutured at postnatal14days to obtain animal model,Rats were housed in the standard environment. After testing by pattern visual evoked potential (P-VEP), all the rats of1-6groups were sacrificed at postnatal45days,60days,90days;The right eyelids of7-8groups were opened while left eyelids were sutured at postnatal60days,Rats of7group(RS) were housed in the standard environment and rats of8group (RS+EE)were housed in the enriched environment,After testing by P-VEP,the two groups were sacrificed at postnatal90days.2. The HE staining were carried out to observe the neural morphological change and recognize the realm and border of the visual cortex,and we measured the expression of PSD-95protein and the transcription level of PSD-95mRNA in the visual cortex of the different groups by using immunohistochemistry staining and Real Time PCR.3. Analysis the images by the image analysis system, analysis the data by SPSS17.0statistics software, compare difference between normal control group (NC) and monocular deprivation group (MD) with the same age (45-day-old rats,60-day-old rats)by paired-sample t test, difference between four groups(90-day-old rats)by analysis of LSD test,The differences were statistically significant (P<0.05).Results1. P-VEP detection:The P-VEP of normal control group (NC) rats have steady wave forms, latency and amplitude,contrasted to the deprived eyes of MD group with the same age, the degree of change for instability, latency, and amplitude of the P wave were decreased(P<0.05),thus confirming deprived eyes have produced amblyopia, and the amblyopia models of rats were constructed successfully.The degree of change for instability, latency, and amplitude of the P wave in RS group was lower than MD group with the same age(P<0.05), contrasted to NC group with the same age, there are still different for the latency and amplitude of the P waves(P<0.05);the degree of change for instability, latency, and amplitude of the P wave in RS+EE group was lower than those of MD group and RS group with the same age(P<0.05), compared with NC group with the same age, the difference was not statistically significant (P>0.05).2.HE staining results:The neurons of visual cortex in normal rats distributed in layers and arranged orderly, The nuclear were dyed to blue and cell plusma were dyed to red.The six layers of visual cortex can be distinguished easily,from superficial to the deep layer were molecular layer,external granular layer,external pyramidal layer,internal granular layer,internal pyramidal layer and polymorphous cell layer.Contrasted to NC groups,there were not obviously abnormality in the visual cortex of MD groups,RS group and RS+EE group.3. The results of immunohistochemistry:In light microscope, immunopositive products of PSD-95in the visual cortex were brown, it predominantly expressed in the neurons cell body,pendrite and axon.The density of positive neurons of PSD-95in the visual cortex of MD group was significantly much less than those in NC group with the same age(P<0.001);The density of positive neurons of PSD-95in RS group was higher than those of MD group(P<0.05), but still lower than those of NC group with the same age (P<0.05);The density of positive neurons of PSD-95in RS+EE group was higher than those of MD group and RS group with the same age(P<0.05), Compared with NC group with the same age, the difference was not statistically significant (P>0.05).4.The expression of PSD-95mRNA:there were PSD-95mRNA in the visual cortex of each group. The relative expression of PSD-95mRNA in the visual cortex of MD group was significantly much less than those in NC group with the same age(P<0.001);The relative expression of PSD-95mRNA in RS group was higher than those of MD group(P＜0.001), but still lower than those of NC group with the same age (P<0.001);The relative expression of PSD-95mRNA in RS+EE group was higher than those of MD group and RS group with the same age(P<0.001), Compared with NC group with the same age, the difference was not statistically significant (P>0.05).Conclusion1. PSD-95mingt participated in the ocular dominance plasticity in the adult visual cortex and a certain degree of synaptic plasticity still retain in adult visual cortex.2. Effect of reverse suture combined with enriched environment intervention was much larger than reverse suture intervention on the reactivation of ocular dominance plasticity in the visual cortex of moncular form deprived adult rats,it offered the theoretical foundation for Occlusion therapy-based combination therapy which is cured adult patients with amblyopia in the clinic.