发育过程中视神经节细胞的膜特性和突触稳定性

Changes of membrane properties and synaptic stability of rat retinal ganglion cells during postnatal development

目的视神经节细胞(RGC)的膜特性和突触稳定性在发育过程中的变化。方法运用全细胞膜片钳技术,分别记录出生后7、15和40 d 3个年龄段的SD大鼠视神经节细胞的动作电位及微小兴奋性突触后电流(m EPSC),通过Patchmaster软件数据采集分析神经节细胞的膜特性和突触稳定性。膜特性从主动和被动两方面来分析,突触稳定性从m EPSC的幅度、频率、上升时间和下降时间等方面来分析。结果通过比较不同年龄段新生SD大鼠RGC的电生理反应特性,发现在发育过程中存在显著改变:主动膜特性中P15组SD大鼠动作电位发放频率相较于P7组明显变大,动作电位半峰宽变小(P<0.01),但比较P15组和P40组的大鼠动作电位发放频率、半峰宽(P=0.086)并无统计学差异;被动膜特性中膜时间常数在发育过程中随着年龄的增加逐渐降低(P<0.01)。突触稳定性中SD大鼠m EPSCs的频率随着年龄的增加逐渐增大(P<0.01),但比较P15组和P40组时频率并无明显统计学差异(P=0.302)。结论发育过程中,RGC的膜特性和突触稳定性发生了规律性改变,并出现了一个关键期,关键期前RGC的电生理特性变化显著,之后逐渐趋于稳定,这种发育电生理变化是RGC对视觉信号处理的基础特性,有助于了解RGC在视觉信息中发挥的内在机制。

Objective To investigate the changes in the membrane properties and synaptic stability of the rat retinal ganglion cells（RGCs） during postnatal development. Methods Whole-cell patch-clamp technique was used to record the action potentials（AP） and miniature excitatory postsynaptic currents（m EPSC） of SD rat RGCs at postnatal days 7, 14 and 40. The active and passive membrane properties and the synaptic stability（measured by the amplitude, frequency, rise time and decay time of m EPSC） of the RGCs were analyzed using Patchmaster software. Results Comparison of the RGCs in SD rats across different postnatal ages revealed significant changes in the electrophysiological characteristics of the RGCs during postnatal development. The discharge rate was significantly greater while the AP half-peak width was significantly smaller at postnatal day 15（P15） than at P7（P0.01）, but were both similar between P15 and P40（P=0.086）; in terms of the passive membrane properties, the membrane time constant gradually decreased during the development. The frequency of m EPSCs increased significantly over time during postnatal development（P0.01）, but was similar between P15 and P40 rats. Conclusion In SD rats, the membrane properties and synaptic stability of the RGCs undergo alterations following a specific pattern, which highlights a critical period where distinct changes occur in the electrophysiological characteristics of RGCs, followed by gradual stabilization over time. Such changes in the electrophysiological characteristics represent the basic characteristics of RGCs for visual signal processing, and understanding of this mechanism may provide insights into the exact role of the RGC in visual information processing.