Effect of protein tyrosine phosphatase σ on the reactivation of ocular dominance plasticity in the visual cortex of adult rats / 中华实验眼科杂志

ABSTRACT

Background Chondroitin sulphate proteoglycans (CSPGs) can cause the termination of ocular dominance plasticity in the visual cortex.Recently,protein tyrosine phosphatase σ (PTPσ) has been identified as a receptor that inhibits CSPGs.However,whether PTPσ and its downstream molecules participate in the reactivation of ocular dominance plasticity in adult visual cortex has not been studied.Objective The present study was to investigate the changes in the expression of the PTPσ,probabilistic neural networks (PNNs),and molecules downstream of PNN,such as N-cadherin/β-catenin,after the reactivation of adult visual cortical plasticity.Methods Fifty-four SPF Long Evans rats were grouped according to different postnatal week (PW) as the PW1 (6 rats),PW3 (6 rats),PW5 (6 rats),PW7 (24 rats),and PW9 (12 rats) groups,and the upper and lower eyelids were sutured in the 12 rats from the PW7 group for 14 days to establish the binocular plasticity reactivation models.Expression of PTPσ and PNNs in the rat visual cortex was detected using immunochemistry,and changes of PTPσ mRNA,N-cadherin mRNA and β-catenin mRNA expression in the rat visual cortex with plasticity reactivation were assessed by real-time fluorescence quantitative PCR (RT Q-PCR).The use of animals followed the Regulations for the Administration of Affairs Concerning Experimental Animals by State Science and Technology Commission.Results The expression level of PTPσ mRNA was significantly higher in the PW9 group than that of the binocular plasticity reactivation models and the PW7 group (t =1.965,3.526,P＜0.01).The staining of the rat visual cortex for PTPσwas localized to the cellular membrane,cytoplasm and axon.Cell densities of the PW9 group in the Ⅱ-Ⅲ layer,Ⅳ layer and Ⅴ-Ⅵ layer of the visual cortex were elevated in the PW9 rats compared with the PW7 rats (t =24.593,23.444,13.556,P＜0.01) and rats from the binocular plasticity reactivation model (t =44.111,43.000,16.556,P＜0.01).Cell densities for PNNs in the Ⅳ and Ⅴ-Ⅵ layers were significantly increased in the PW9 rats in comparison with the PW7 rats (t=1.926,P＜0.01 ;t=1.370,P＜0.05),but the cell density in the Ⅱ-Ⅱ layer has no statistical significance (t=0.889,P＞0.05).However,cell densities for PNNs in the Ⅱ-Ⅲ and Ⅳ layers in the binocular plasticity reactivation models were lower than those of the PW9 rats (t =2.556,4.585,P＜0.01).Compared with PW1 rats,the expression levels of the N-cadherin mRNA in the PW3,PW5,PW7,PW9 rats were lower (t =28.932,28.988,27.083,28.908,P＜0.01),but those in the PW7 rats were enhanced in comparison with the PW3 rats,PW5 rats and PW9 rats (t =1.848,1.904,1.825,P＜0.01).No significant difference was seen in the expression of the N-cadherin mRNA between the PW9 rats and rats from the binocular plasticity reactivation model (t =0.072,P＞0.05).A statistically significant increase was found in the β-catenin mRNA expression in the PW1 rats compared with the PW3,PW5,PW7 and PW9 rats (t =3.918,3.534,2.645,4.652,P＜ 0.0 1),as well as between rats from the binocular plasticity reactivation model and the PW9 rats (t =0.570,P＜0.01).Conclusions PTPr,PNNs and β-catenin are involved in the reactivation of ocular dominance plasticity in the adult visual cortex.