Sun Wenzhi, Deng Qiudong, Levick William R, He Shigang
State Key Laboratory of Brain and Cognitive Sciences, Institute of Biophysics, Chinese Academy of Sciences, 15 Da-tun Road, Beijing 100101, China.
J Physiol. 2006 Oct 1;576(Pt 1):197-202. doi: 10.1113/jphysiol.2006.115857. Epub 2006 Aug 10.
Two types of ganglion cells (RGCs) compute motion direction in the retina: the ON-OFF direction-selective ganglion cells (DSGCs) and the ON DSGCs. The ON DSGCs are much less studied mostly due to the low encounter rate. In this study, we investigated the physiology, dendritic morphology and synaptic inputs of the ON DSGCs in the mouse retina. When a visual stimulus moved back and forth in the preferred-null axis, we found that the ON DSGCs exhibited a larger EPSC when the visual stimulus moved in the preferred direction and a larger IPSC in the opposite, or null direction, similar to what has been found in ON-OFF DSGCs. This similar synaptic input pattern is in contrast to other well-known differences, namely: profile of velocity sensitivity, distribution of preferred directions, and different central projection of the axons. Immunohistochemical staining showed that the dendrites of ON DSGCs exhibited tight cofasciculation with the cholinergic plexus. These findings suggest that cholinergic amacrine cells may play an important role in generating direction selectivity in the ON DSGCs, and that the mechanism for coding motion direction is probably similar for the two types of DSGCs in the retina.
视网膜中有两种神经节细胞（RGCs）负责计算运动方向：开-关方向选择性神经节细胞（DSGCs）和开DSGCs。由于遇到的概率较低，开DSGCs的研究要少得多。在本研究中，我们调查了小鼠视网膜中开DSGCs的生理学、树突形态和突触输入。当视觉刺激在偏好-零轴上来回移动时，我们发现当视觉刺激沿偏好方向移动时，开DSGCs表现出更大的兴奋性突触后电流（EPSC），而在相反方向或零方向则表现出更大的抑制性突触后电流（IPSC），这与在开-关DSGCs中发现的情况类似。这种相似的突触输入模式与其他众所周知的差异形成对比，即：速度敏感性特征、偏好方向分布以及轴突的不同中枢投射。免疫组织化学染色显示，开DSGCs的树突与胆碱能丛紧密共束。这些发现表明，胆碱能无长突细胞可能在开DSGCs的方向选择性产生中起重要作用，并且视网膜中这两种类型的DSGCs编码运动方向的机制可能相似。
