Crook J M, Eysel U T, Machemer H F
Department of Neurophysiology, Faculty of Medicine, Ruhr-Universität Bochum, F.R.G.
Neuroscience. 1991;40(1):1-12. doi: 10.1016/0306-4522(91)90169-o.
We have investigated the effect of iontophoretically applying the inhibitory transmitter gamma-aminobutyric acid (GABA) through four pipettes, each located at a horizontal distance of some 500-600 microns from the recording site, on the orientation tuning of cells in areas 17 and 18 of the cat visual cortex for moving the stationary flash-presented bar stimuli. Forty-five of 74 cells tested in area 18 (61%) showed a significant (greater than 25%) increase in orientation tuning width (at half the maximum response) during GABA application, which reflected an increase in response to non-optimal orientations. The mean orientation tuning width of these cells increased by 79%, and the ratio of responses to the orientation orthogonal to the optimum and to the optimum increased from 0.16 to 0.46. The results were similar to those from area 17, in which 36 of 54 cells (66%) showed significant broadening of orientation tuning during GABA application, with a 90% increase in mean tuning width and an increase in the relative response to the orientation orthogonal to the optimum from 0.17 to 0.42. The distributions of cells in areas 17 and 18 with respect to the magnitude of GABA-induced effects on orientation tuning width were not significantly different (mean increase in tuning width: area 17, 102%; area 18, 87%). Although most cells were tested only with moving bars, comparable effects of remote GABA application on orientation tuning were observed when stationary flash-presented bars were used. Of 11 cells thus tested in area 18, seven showed significantly broader tuning during GABA application, with a 132% increase in mean tuning width. In some 25% of cells in each area which showed a significant effect of GABA application on orientation tuning the response to at least one non-optimal orientation exceeded, during GABA application, the response to the previous optimum. There was essentially no correlation between the changes in orientation tuning and changes in the level of spontaneous activity or in the response to the optimum orientation during GABA application. Thus, an increase in the general excitability of recorded cells or the loss of an unspecific inhibitory input cannot account for the effects of GABA application on orientation tuning. Remote GABA application presumably inactivated cells with different preferred orientations from that of the recorded cell. It is thus argued that the observed broadening of orientation tuning during GABA application reflected the loss of an inhibitory input tuned to non-optimal orientations.(ABSTRACT TRUNCATED AT 400 WORDS)
我们研究了通过四个移液管离子电渗施加抑制性递质γ-氨基丁酸（GABA）对猫视觉皮层17区和18区细胞方向调谐的影响，每个移液管位于距记录部位约500 - 600微米的水平距离处，用于移动静止闪光呈现的条形刺激。在18区测试的74个细胞中有45个（61%）在施加GABA期间，方向调谐宽度（在最大反应的一半处）显著增加（大于25%），这反映了对非最佳方向反应的增加。这些细胞的平均方向调谐宽度增加了79%，对与最佳方向正交的方向和最佳方向的反应比率从0.16增加到0.46。结果与17区相似，在17区54个细胞中有36个（66%）在施加GABA期间方向调谐显著变宽，平均调谐宽度增加90%，对与最佳方向正交的方向的相对反应从0.17增加到0.42。17区和18区中细胞关于GABA诱导的方向调谐宽度变化幅度的分布没有显著差异（调谐宽度的平均增加：17区为102%；18区为87%）。虽然大多数细胞仅用移动条形进行测试，但当使用静止闪光呈现的条形时，观察到远程施加GABA对方向调谐有类似的影响。在18区这样测试的11个细胞中，7个在施加GABA期间调谐显著变宽，平均调谐宽度增加132%。在每个区域中约25%的细胞中，GABA对方向调谐有显著影响，在施加GABA期间，对至少一个非最佳方向的反应超过了对先前最佳方向的反应。在施加GABA期间，方向调谐的变化与自发活动水平的变化或对最佳方向的反应之间基本上没有相关性。因此，记录细胞的一般兴奋性增加或非特异性抑制性输入的丧失不能解释施加GABA对方向调谐的影响。远程施加GABA可能使与记录细胞偏好方向不同的细胞失活。因此有人认为，在施加GABA期间观察到的方向调谐变宽反映了对非最佳方向调谐的抑制性输入的丧失。（摘要截断于400字）
