Frumkes T E, Nelson R
Laboratory of Neurophysiology, National Institute of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, USA.
Vis Neurosci. 1995 Jul-Aug;12(4):641-50. doi: 10.1017/s0952523800008932.
Putative GABAergic mechanisms were studied in perfused cat retina by means of intracellular recording and application of GABA and the GABAA agonists delta-amino valeric acid (dAVA), muscimol, and THIP. In contrast to results reported previously for cold-blooded vertebrates, introduction of 20 mM GABA into the superfusate had no influence upon the response properties of cat retinal horizontal cells (HCs). In common with results reported in cold-blooded vertebrates, introduction of the GABAA agonists dAVA (2-12 mM) and THIP or muscimol (0.2-1 mM) had four consistent reversible influences upon the response properties of cat retinal HCs: (1) they reduced photic-response amplitude, (2) slowed response onset, (3) slowed response offset, and (4) depolarized the dark membrane potential. Both rod and cone signal components were affected. GABAA agonists had similar influences upon both the time course and amplitude of responses recorded from amacrine and ganglion cells. In all cell types examined, the influence upon response kinetics was made particularly apparent with rapidly flickering stimuli. Flicker responses were reduced in amplitude much more than sustained responses. These results suggest that, in addition to other influences, GABAergic action serves to modify the time course of photic responses in both the inner and outer plexiform layer of mammalian retina making responses slower and less phasic.
通过细胞内记录以及应用γ-氨基丁酸（GABA）和GABAA激动剂δ-氨基戊酸（dAVA）、蝇蕈醇和4,5,6,7-四氢异喹啉-3-醇（THIP），对灌注猫视网膜中的假定GABA能机制进行了研究。与先前报道的冷血脊椎动物的结果相反，向灌流液中加入20 mM GABA对猫视网膜水平细胞（HCs）的反应特性没有影响。与冷血脊椎动物报道的结果相同，加入GABAA激动剂dAVA（2 - 12 mM）以及THIP或蝇蕈醇（0.2 - 1 mM）对猫视网膜HCs的反应特性有四个一致的可逆影响：（1）它们降低了光反应幅度，（2）减缓了反应起始，（3）减缓了反应终止，（4）使暗膜电位去极化。视杆和视锥信号成分均受到影响。GABAA激动剂对无长突细胞和神经节细胞记录的反应的时间进程和幅度都有类似影响。在所有检测的细胞类型中，对反应动力学的影响在快速闪烁刺激下尤为明显。闪烁反应幅度的降低比持续反应大得多。这些结果表明，除了其他影响外，GABA能作用有助于改变哺乳动物视网膜内、外网状层光反应的时间进程，使反应变慢且更少呈相位性。
