Bonaventure N, Wioland N, Jardon B
Eur J Pharmacol. 1986 Mar 4;121(3):327-36. doi: 10.1016/0014-2999(86)90253-0.
When GABA antagonists (picrotoxin, bicuculline methiodide and SR 95103) were intravitreally injected in the frog, they increased the number of spikes of transient retinal ganglion cells, as well as the duration of the response. Thus, the transient pattern of the response became more sustained. GABA antagonists also provoked a marked increase in the size of the receptive field, which might be due to the abolition of the inhibition exerted by the surround upon the centre of the field. In fact, a stimulus applied to the surround of the field simultaneously with one applied to the centre no longer provoked the reduction of the field area nor that of the number of spikes. These are effects which were always observed before drug injection. After picrotoxin injection, the enlarged field was concentric with the initial one, both angular diameters doubled, whereas after bicuculline or SR 95103, the enlarged field was not concentric with the initial one and only one diameter increased. Thus, GABA inhibition appears to be distributed according to an anisotropic spatial pattern. Whether this anisotropy might be an input for direction selectivity in the frog visual system is a topic of discussion. With respect to SR 95103, this compound proved to act like a selective GABA antagonist with long lasting effects.
当向青蛙玻璃体内注射γ-氨基丁酸（GABA）拮抗剂（印防己毒素、碘化荷包牡丹碱和SR 95103）时，它们会增加瞬态视网膜神经节细胞的尖峰数量以及反应持续时间。因此，反应的瞬态模式变得更加持久。GABA拮抗剂还会使感受野的大小显著增加，这可能是由于消除了周边对感受野中心施加的抑制作用。事实上，同时施加于感受野周边和中心的刺激不再引起感受野面积或尖峰数量的减少。这些效应在注射药物前总是可以观察到。注射印防己毒素后，扩大的感受野与初始感受野同心，两个角直径都加倍了，而注射碘化荷包牡丹碱或SR 95103后，扩大的感受野与初始感受野不同心，只有一个直径增加。因此，GABA抑制似乎是按照各向异性的空间模式分布的。这种各向异性是否可能是青蛙视觉系统中方向选择性的一个输入，是一个有待讨论的话题。就SR 95103而言，该化合物被证明表现得像一种具有长效作用的选择性GABA拮抗剂。
