EFFECT OF LEVODOPA ON THE HUMAN DARK-ADAPTATION THRESHOLD

Background: In several species there is strong evidence that the retin al dopamine turnover is influenced by retinal dark and light adaptatio n. In the human retina, dopamine has been found in amacrine and interp lexiform cells. Methods: In the present study, the influence of orally administered levodopa on the human dark adaptation was investigated i n healthy subjects using the Goldmann-Weekers adaptometer. To exclude effects of levodopa on the pupil size, a second group was examined aft er pupil dilation before each examination. A third and fourth group we re examined under the same conditions as the first two groups, but wit hout levodopa administration. Results: Levodopa caused a uniform thres hold elevation throughout dark adaptation with undilated and dilated p upils. No effect on sensitivity was observed in the control groups. Co nclusion: These results show a dopaminergic reduction in sensitivity d uring human dark adaptation.