Pfleger B, Bonds A B
Department of Biomedical and Electrical Engineering, Vanderbilt University, Nashville, TN 37235, USA.
Exp Brain Res. 1995;104(1):81-8. doi: 10.1007/BF00229857.
The influence of GABAA receptors on orientation selectivity of cat complex cells was tested by iontophoresis of the GABAA receptor blockers bicuculline and N-methyl-bicuculline while stimulating with drifting sinusoidal gratings. Reduction of orientation tuning was markedly less than reported in previous studies that used drifting bars as visual stimuli. Only 3/31 cells lost orientation selectivity, with an average increase in bandwidth of 33%, as opposed to half the cells losing selectivity and a bandwidth increase for the remainder of 47% as reported previously. Infusion of GABAA blockers revealed a prominent stimulus onset transient response, lasting about 120 ms, that showed a broadening of orientation selectivity comparable to that found using drifting bars under similar circumstances. We believe that drifting gratings emphasize a steady-state response component that retains, in the presence of GABAA blockers, significant orientation selectivity. Because the onset transient is initially unselective for orientation, we suggest that the steady-state, orientation-selective response component develops from an alternate inhibitory mechanism, possibly mediated by GABAB receptors.
通过离子导入γ-氨基丁酸A型（GABAA）受体阻滞剂荷包牡丹碱和N-甲基荷包牡丹碱，并同时用漂移的正弦光栅进行刺激，来测试GABAA受体对猫复合细胞方向选择性的影响。方向调谐的降低明显小于先前使用漂移棒作为视觉刺激的研究报告。只有3/31的细胞失去方向选择性，带宽平均增加33%，而先前报告称有一半的细胞失去选择性，其余细胞的带宽增加47%。注入GABAA阻滞剂显示出一个突出的刺激起始瞬态反应，持续约120毫秒，其方向选择性的拓宽与在类似情况下使用漂移棒时发现的情况相当。我们认为，漂移光栅强调了一个稳态反应成分，在存在GABAA阻滞剂的情况下，该成分保留了显著的方向选择性。由于起始瞬态最初对方向不具有选择性，我们认为稳态的、方向选择性的反应成分是由一种可能由GABAB受体介导的替代抑制机制产生的。
