NMDA受体亚单位NR2A、NR2B在正常大鼠视皮层中的表达变化

Expression of NMDA receptor subunit NR2A and NR2B in visual cortex of rats

目的观察大鼠视皮层中N-甲基-D-天门冬氨酸受体(NMDAR)功能亚单位NR2A与NR2B的表达随发育的变化。方法运用免疫组织化学和图像分析技术分析NR2A、NR2B在Wistar大鼠生后第0、14、21、28、35、42、60、90d视皮层的表达情况。结果NR2A、NR2B在出生时的视皮层中即已存在,之后NR2A的表达缓慢上升,生后35d达峰值,后略有下降,至成年维持于较高水平;NR2B生后14d达到峰值,继而逐渐下降,至第60d后趋于平稳。结论视皮层中NR2A、NR2B表达量的变化与视觉发育可塑性关键期的起始与终止在时间上具有一定程度的同步性,提示生后NR2A、NR2B表达的发育性时间差异可能是视觉发育可塑性调节的一个重要分子基础。

Objective N-methyl-D-aspartate receptors（NMDAR）are important in developmental plasticity in the visual cortex.The NR2A and NR2B subunits of NMDAR may play a different role during the plasticity.The change of expression of NR2A and NR2B from neonatal to 90-day Wistar rats in visual cortex was investigated in this study.Methods Forty neonatal healthy pureblooded Wistar rats were divided into eight groups randomly according to the different killing time and five for each.These rats were sacrificed at 0,14,21,28,35,42,60 and 90 days respectively.The sections with 5 μm thickness were cut from paraffin imbedded tissue of visual cortex in coronary side,and the expressions of NR2A and NR2B in the visual cortex of rats were examined by immunohistochemstry with monoclonal anti-NR2A antibody and anti-NR2B antibody respectively.After streptomycin avidin biotin peroxidase complex（SABC）staining,microscope and computer-assisted image analyses were used to explore the dynamic changes of NMDA receptor subunit protein.Results The neurons in every layer lined in order.The positive expression of NR2A,NR2B showed brown staining mainly in cell body,dendrites and axons of neuron.Majority of the positive cells were pyramidal cells and granular cells.NR2A and NR2B were expressed in neonatal rats.The quantity of the expression of NR2A was gradually increased upon rats age with the climax value in 35-day rats and then decreased slightly and kept a stably level in adult rats.The expression of NR2B peaked in 14-day and then decreased gradually and trended stable status in the postnatal 60-day.Conclusion The expression level of NR2A and NR2B correlated with the onset and decline of the critical period.It propose that one of the mechanisms for experience-dependent modulation of synaptic plasticity in the visual cortex may be regulated by NMDAR subunits.