Department of Ophthalmology, Massachusetts Eye and Ear Infirmary and Harvard Medical School, Boston, MA, USA.
Eur J Neurosci. 2011 Jan;33(1):36-48. doi: 10.1111/j.1460-9568.2010.07484.x. Epub 2010 Nov 22.
Recent studies have shown a continued maturation of visual responsiveness and synaptic activity of retina after eye opening, including the size of receptive fields of retinal ganglion cells (RGCs), light-evoked synaptic output of RGCs, bipolar cell spontaneous synaptic inputs to RGCs, and the synaptic connections between RGCs and ON and OFF bipolar cells. Light deprivation retarded some of these age-dependent changes. However, many other functional and morphological features of RGCs are not sensitive to visual experience. To determine whether light-evoked synaptic responses of RGCs undergo developmental change, we directly examined the light-evoked synaptic inputs from ON and OFF synaptic pathways to RGCs in developing retinas, and found that both light-evoked excitatory and inhibitory synaptic currents decreased, but not increased, with age. We also examined the light-evoked synaptic inputs from ON and OFF synaptic pathways to amacrine cells in developing retinas and found that the light-evoked synaptic input of amacrine cells is also downregulated in developing mouse retina. Different from the developmental changes of RGC spontaneous synaptic activity, dark rearing has little effect on the developmental changes of light-evoked synaptic activity of both RGCs and amacrine cells. Therefore, we concluded that the synaptic mechanisms mediating spontaneous and light-evoked synaptic activity of RGCs and amacrine cells are likely to be different.
最近的研究表明，在眼睛睁开后，视网膜的视觉反应和突触活动会继续成熟，包括视网膜神经节细胞（RGC）的感受野大小、RGC 的光诱发突触输出、双极细胞对 RGC 的自发突触输入，以及 RGC 与 ON 和 OFF 双极细胞之间的突触连接。光剥夺会延迟其中一些与年龄相关的变化。然而，RGC 的许多其他功能和形态特征对视觉经验并不敏感。为了确定 RGC 的光诱发突触反应是否会发生发育变化，我们直接研究了发育中视网膜中来自 ON 和 OFF 突触通路的 RGC 的光诱发突触输入，发现光诱发的兴奋性和抑制性突触电流都随年龄而减少，但没有增加。我们还研究了发育中视网膜中来自 ON 和 OFF 突触通路的双极细胞的光诱发突触输入，发现双极细胞的光诱发突触输入在发育中的小鼠视网膜中也受到下调。与 RGC 自发突触活动的发育变化不同，暗适应对 RGC 和双极细胞的光诱发突触活动的发育变化影响很小。因此，我们得出结论，调节 RGC 和双极细胞自发和光诱发突触活动的突触机制可能不同。
