Sjoerdsma T, Kamermans M, Spekreijse H
Graduate School Neurosciences Amsterdam, The Netherlands Ophthalmic Research Institute, Laboratory for Medical Physics, The Netherlands.
Vision Res. 1996 Nov;36(21):3519-25. doi: 10.1016/0042-6989(96)83892-2.
Wavelength discrimination in goldfish was measured behaviourally. Both acute application of ethambutol injected into the eye and chronic application by feeding the animals daily 25 mg ethambutol for 1 month had the same effect on wavelength discrimination in the range of 560-640 nm. This means that: (1) electrophysiological experiments, in which drug application is primarily acute, reflect the same disturbance as behavioural experiments, in which drug application is chronic; and that (2) the origin of the color vision defect must be retinal. Furthermore reduction in stimulus intensity by 2 log units caused, in control fish, a similar disturbance in wavelength discrimination as induced by ethambutol, whereas an increase of stimulus intensity by 2 log units abolished in ethambutol-fed fish the discrimination disturbance. These results indicate that ethambutol shifts the threshold for wavelength discrimination without changing the absolute sensitivity of the cone systems.
