Department of Physiology, Medical University-Sofia, 1 G Sofiiski Str, 1431 Sofia, Bulgaria.
J Neural Transm (Vienna). 2010 Apr;117(4):431-44. doi: 10.1007/s00702-010-0381-z. Epub 2010 Mar 6.
GABAergic transmission is involved in color coding in the retina. The specific contribution of different GABA receptors to spectral sensitivity of the retinal responses is not well characterized. We studied GABAa and GABAc receptor-mediated effects on the intensity-response functions of the electroretinographic ON (b-wave) and OFF (d-wave) responses to color stimuli. For this purpose, we compared the effects of GABAa receptor blockade by bicuculline with the effects of GABAa + GABAc receptor blockade by picrotoxin. The blockade of both GABAa and GABAc receptors caused an amplitude increase of the electroretinographic responses, but the effects of the two blockades depended in a specific manner on stimulus intensity and wavelength. The effects of GABAa receptor blockade showed distinct color ON/OFF asymmetry. The absolute and relative sensitivities of the ON responses to blue stimuli and OFF responses to red stimuli were increased to the greatest degree while the sensitivity of the ON responses to red stimuli and OFF responses to blue stimuli was least increased. In contrast, color ON/OFF asymmetry was not typical of the effects of GABAc receptor blockade. The most prominent GABAc effect was the sensitivity increase of the ON and OFF responses to blue stimuli and, to some lesser extent, to green stimuli. The results of this study indicate a specific role of GABAa and GABAc receptor-mediated influences in processing of chromatic information in the distal retina.
GABA 能传递参与视网膜的颜色编码。不同的 GABA 受体对视网膜反应光谱灵敏度的特定贡献尚未很好地描述。我们研究了 GABAa 和 GABAc 受体介导对视网膜电反应的强度-反应功能的影响ON（b-波）和 OFF（d-波）对颜色刺激的反应。为此，我们比较了 GABAa 受体阻断剂毒蕈碱与 GABAa + GABAc 受体阻断剂印防己毒素对电反应的影响。两种 GABA 受体的阻断均导致视网膜反应的振幅增加，但两种阻断的作用在特定的方式取决于刺激强度和波长。GABAa 受体阻断的作用表现出明显的颜色 ON/OFF 不对称性。蓝色刺激的 ON 反应和红色刺激的 OFF 反应的绝对和相对敏感性增加最大，而红色刺激的 ON 反应和蓝色刺激的 OFF 反应的敏感性增加最小。相比之下，GABAc 受体阻断的作用没有典型的颜色 ON/OFF 不对称性。最突出的 GABAc 作用是对蓝色刺激的 ON 和 OFF 反应以及在较小程度上对绿色刺激的敏感性增加。本研究的结果表明，GABAa 和 GABAc 受体介导的影响在处理远侧视网膜的色觉信息中具有特定的作用。
