Abstract

SO.05.07

Choroidal blood flow changes during light/dark transition – is there an involvement of the dopamine-1 receptor?

Fuchsjäger-Mayrl G.^1,2, Huemer K.-H.¹, Kircher K.², Resch H.¹, Weigert G.¹, Schmetterer L.^1,3 
1Department of Clinical Pharmacology, ²Department of Opthalmology, ³Department of Biomedical Engineering and Medical Physics, Medical University of Vienna

Objective: Recent results indicate that a light/dark transition is associated with a reduction in choroidal blood flow (CBF) due to an unknown mechanism. Dopamine has been discussed as a chemical messenger for light adaptation. Accordingly, dopamine could provide a modulatory input to the light/dark transition induced changes of choroidal circulation.
Methods: 12 healthy male subjects were included in this randomized placebo-controlled three way cross-over trial. On three different study days the D1 antagonist quetiapine, the D2 antagonist sulpiride or placebo were administered. CBF was measured using laser Doppler flowmetry during light/dark transitions and the results were expressed as %change from baseline. This dark reactivity was compared among the three study days using a one-way ANOVA.
Results: In keeping with our previous studies CBF showed a reversible decrease after light/dark transition. None of the administered drugs changed baseline CBF. The dark reactivity was 11.5±5.8% on the placebo study day. This dark reactivity was significantly altered after administration of quetiapine (5.8±4.6%, p<0.05), whereas sulpiride did not alter the dark reactivity (9.4±7.1%).
Conclusions: We have previously shown that dopamine increases CBF in healthy subjects. The results of the present study indicate that neither D1- nor D2-receptor antagonists alter CBF at baseline. The D1 receptor antagonist quetiapine does, however, alter the response of CBF during light/dark transitions indicating a role of this receptor subtype in the regulation of blood flow during changes in retinal illumination.

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