Dopaminergic Modulation of Choroidal Blood Flow Changes During Dark/Light Transitions
Status:
Completed
Trial end date:
2006-08-01
Target enrollment:
Participant gender:
Summary
There is evidence from a variety of animal studies that choroidal blood flow is under neural
control. By contrast, only little information is available from human studies. Recent results
indicate that a light/dark transition is associated with a reduction in choroidal blood flow
due to an unknown mechanism. We have shown that during unilateral dark/light transitions both
eyes react with choroidal vasoconstriction strongly indicating a neural mechanism responsible
for the blood flow changes.
Dopamine has been discussed as a chemical messenger for light adaptation. However,
dopaminergic effects in the eye are not restricted to synaptic sites of release, but dopamine
also diffuses to the outer retinal layers and pigment epithelium. Accordingly, dopaminergic
effects also include a modulatory role on retinal vessel diameter and animal studies provide
evidence for vasodilatory effects in the choroid. There is evidence that during darkness
retinal and choroidal dopamine levels decrease. Accordingly, dopamine could provide a
modulatory input to the light/dark transition induced changes of choroidal circulation. The
aim of the present study is to test this hypothesis.