A mixed D1 and D2 antagonist does not replay pattern electroretinogram alterations observed with a selective D2 antagonist in normal humans: relationship with Parkinson's disease pattern electroretinogram alterations

The human retina produces a tuned response to stimuli of increasing spatial frequency reversed at a steady state. The peak amplitude response, at medi um spatial frequencies, is decreased in Parkinson's disease and in normal s ubjects (n = 18) treated with a D2 dopaminergic antagonist (l-sulpiride). H ere, we report that a mixed D1-D2 receptor antagonist (haloperidol) in norm al subjects (n = 18) does not produce an amplitude decrease of medium spati al frequencies (SFs) responses but it decreases low-frequency response. It could argued that the increased dopamine release produced by the presynapti c D2 antagonistic action of haloperidol is subsequently counteracted at pos t synaptic level by its D1 antagonistic effect, producing a net counterbala nce at medium SFs. These data suggest that the two dopamine receptors may p lay different roles in the retinal function and in the origin of visual alt erations in Parkinson's disease. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.