Bicuculline produces reversible red-green color blindness in goldfish, as revealed by monocular behavioral testing.

The effect of the GABAA receptor antagonist bicuculline (methiodide) on goldfish wavelength discrimination was studied. This was done using a behavioral two alternative forced choice procedure at training wavelengths 500 and 600 nm, where goldfish wavelength discrimination is the best. During the experiments the goldfish could use only the eye that was intravitreally injected with bicuculline; the other eye was covered. In control experiments, to exclude systemic effects, the covering of the eyes was reversed. Bicuculline induced loss of wavelength discrimination ability around 600 nm, while this ability was not affected around 500 nm. The effect was reversible, since discrimination around 600 nm returned to normal within a day after injection. The results indicate that GABAA receptor mediated processes, like horizontal cell to cone feedback, play an important role in wavelength discrimination at the long wavelength part of the spectrum.