Cook P B, Lukasiewicz P D, McReynolds J S
Department of Physiology, The University of Michigan, Ann Arbor, Michigan 48109-0622, USA.
J Neurosci. 2000 Jan 15;20(2):806-12. doi: 10.1523/JNEUROSCI.20-02-00806.2000.
We studied the role of GABA in adaptive changes in a lateral inhibitory system in the tiger salamander retina. In dark-adapted retinal slice preparations picrotoxin caused a slow enhancement of glycine-mediated IPSCs in ganglion cells. The enhancement of glycinergic IPSCs developed slowly over the course of 5-20 min, even though picrotoxin blocked both GABA(A) and GABA(C) receptors within a few seconds. The slow enhancement of glycinergic IPSCs by picrotoxin was much weaker in light-adapted preparations. The slow enhancement of glycinergic inhibitory inputs was not produced by bicuculline, indicating that it involved GABA(C) receptors. The responses of ganglion cells to direct application of glycine were not enhanced by picrotoxin, indicating that the enhancement was not caused by an action on glycine receptors. In dark-adapted eyecup preparations picrotoxin caused a slow enhancement of glycinergic IPSPs and transient lateral inhibition produced by a rotating windmill pattern, similar to the effect of light adaptation. The results suggest that the glycinergic inhibitory inputs are modulated by an unknown substance whose synthesis and/or release is inhibited in dark-adapted retinas by GABA acting at GABA(C) receptors.
我们研究了γ-氨基丁酸（GABA）在虎纹钝口螈视网膜侧抑制系统适应性变化中的作用。在暗适应的视网膜切片标本中，印防己毒素可使神经节细胞中甘氨酸介导的抑制性突触后电流（IPSCs）缓慢增强。尽管印防己毒素在几秒钟内就能阻断GABA(A)和GABA(C)受体，但甘氨酸能IPSCs的增强在5 - 20分钟的过程中缓慢发展。在明适应标本中，印防己毒素对甘氨酸能IPSCs的缓慢增强作用要弱得多。荷包牡丹碱不会产生甘氨酸能抑制性输入的缓慢增强现象，这表明该现象涉及GABA(C)受体。印防己毒素不会增强神经节细胞对直接施加甘氨酸的反应，这表明这种增强不是由对甘氨酸受体的作用引起的。在暗适应的眼杯标本中，印防己毒素可使甘氨酸能抑制性突触后电位（IPSPs）以及由旋转风车图案产生的瞬时侧抑制缓慢增强，这类似于明适应的效果。结果表明，甘氨酸能抑制性输入受一种未知物质的调节，在暗适应的视网膜中，GABA作用于GABA(C)受体可抑制该物质的合成和/或释放。
