神经毒素ECMA对家鸽视网膜神经节单元反应特性的影响

EFFECTS OF ECMA (ETHYLCHOLINE MUSTARD AZIRIDINIUM ION)ON THE RESPONSE PROPERTIES OF THE RETINAL GANGLION UNITS IN PIGEON

从家鸽视差表层总共记录了１０１个视网膜神经节单元，并定量分析研究ＥＣＭＡ损伤对其反应特性的影响，在对照组中，神经节单元都没有自发放电，而需要视觉刺激才能引起反应，对闪光刺激的反应，分别为ＯＮ—ＯＦＦ，ＯＮ，ＯＦＦ三种，其反应均是瞬变的，而且也都对在感受野内运动的小条纹起反应。４２个单元中有１４个是方向选择性单元。其它的则为运动敏感单元。方向选择性单元的无效方向不是均等分布的，其中有８个单元的无效是从前向后的，但没有发现其无效方向是从后向前的单元。与对照组相比，经ＥＣＭＡ损伤后的实验组中只记录到ＯＮ－ＯＦＦ反应和ＯＮ反应单元，未能找到单独的ＯＦＦ反应单元。神经节单元的ＯＮ反应部分为持续成分。所有的单元对运动条纹刺激都失掉了方向选择性，这些现象的机理可能是由于ＥＣＭＡ去除了胆碱能无足细胞所致。

A total of 101 retinal ganglion units were recorded from axons and terminal arbours in the superficial layer of the optic tectum of pigeon (Columba livia) and quantitatively analyzed to study the effects of ECMA-lesion on the response properties of retinal ganglion units.In control group, units could be classified into the ON, OFF and ON-OFF transient responses to flashing spots. In response to the moving bars, 14 out of 42 unitS (29%) were directionally selective and the others were only motion-sensitive. The null directions of the directionally selective units were not evenly distributed. 8 out of them had their null directions from anterior in the receptive field to the back, while none was its null direction from posterior in the field to the front.After ECMA-lesion of the retina, only ON-OFF and ON responses were recorded and they almost showed a sustained ON-response component which was not detected in the control group. The directionally selective units did not be found in response to moving bar and all units were non -directional motion -sensitive.It was discussed that the mechanism underlying the disappearance of the transient responses and of the directional selectivity of ganglion units might be due to elimination of the cholinergic amacrine cells with ECMA.