GABAa and GABAc receptor-mediated modulation of responses to color stimuli: electroretinographic study in the turtle Emys orbicularis

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 electror...

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Bibliographic Details
Published in:Journal of Neural Transmission 2010-04, Vol.117 (4), p.431-444
Main Authors: Kupenova, Petia, Vitanova, Lily, Popova, Elka
Format: Article
Language:English
Subjects:
Animals
Basic Neurosciences
Bicuculline - pharmacology
Color
Electroretinography
GABA Antagonists - pharmacology
GABA-A Receptor Antagonists
Genetics and Immunology - Original Article
In Vitro Techniques
Medicine
Medicine & Public Health
Neurology
Neurosciences
Photic Stimulation
Picrotoxin - pharmacology
Psychiatry
Receptors, GABA - metabolism
Receptors, GABA-A - metabolism
Retina - drug effects
Retina - physiology
Retinal Cone Photoreceptor Cells - physiology
Time Factors
Turtles
Vision, Ocular - drug effects
Vision, Ocular - physiology
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Summary: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.
ISSN:0300-9564
1435-1463
DOI:10.1007/s00702-010-0381-z