Expression of synapsin in visual cortex of developing mice / 中华实验眼科杂志

ABSTRACT

Background The treatment timing and method of amblyopia rely on the plasticity of visual system.Synapsin is a family of presynaptic terminal specific protein.Its role in visual developmental plasticity is below understood.Objective To investigate the dynamic expressions of synapsin (T-synapsin),and phosphorylation of synapsin (p-synapsin Ⅰ a/b) in visual cortex of normal mice and further explore the role of synapsin in plasticity of visual system.Methods Forty-two clean neonatal C57BL/6 mice were collected.The mice were sacrificed at postnatal 7,14,21,28,35,42,60 days respectively to obtain the tissue samples of visual cortex.Expression levels of T-synapsin and p-synapsin in the visual cortex following the ageing were quantitatively detected using Western blot assay.Results The expression of synapsin in normal mice showed a dynamic increase with the ageing.The T-synapsin Ⅰ a/b/β-actin value in visual cortex was (21.32 ± 3.27) ％,(56.27 ± 10.18) ％,(77.05 ± 10.05) ％,(83.75±10.52) ％,(94.69±11.46)％,(98.75±5.86) ％ of adults mice (postnatal 60 days,P60) in the mice of postnatal 7,14,21,28,35,42 days,respectively,showing a significant difference among them (F =69.538,P ＜ 0.001).Compared with the adult mice,the T-synapsin Ⅰ a/b/β-actin value in the mice of P7,P14,P21,P28 was significantly lower (all at P＜0.05),but no significant difference was found between P35 and P60,P42 and P60 (P =0.280,0.798).The development trend of different synapsin subtypes,such as T-synapsin Ⅰ a/b,T-synapsin Ⅱ a,T-synapsin Ⅱ b and T-synapsin Ⅲ a,was not quite the same during the ageing.The expression of T-synapsin Ⅱ a and Ⅲ a increasing more slowly with development,and kept increasing until P60.Significant differences were found among various age of mice in T-synapsin Ⅱ a,Ⅱ b,Ⅲa respectively(F =42.492 55.595,39.172,all at P＜0.001).The p-synapsin Ⅰ a/b level in the visual cortex elevated with the ageing of the mice,and that peaked in P21 mice,which was (2.86±0.17) times more than that in adult mice.After that,the expression level of p-synapsin Ⅰ a/b dropped rapidly.A significant difference was found in the p-synapsin Ⅰ a/b expression among different ages of mice (F =22.620,P ＜ 0.001).Conclusions Synapsin level in visual cortex presents a developmental change which correlated with the onset and decline of the critical period.Synapsin is probably involved in the regulation of neural plasticity in visual cortex in critical period.