The Diameter of Retinal Arterioles Is Unaffected by Intravascular Administration of the Adenosine A Receptor Agonist Regadenoson in Normal Persons.

BACKGROUND

The neurotransmitter adenosine has been proposed to be involved in the pathogenesis of diabetic retinopathy, which may be due to the vasoactive properties of the compound. Previous studies have shown that adenosine can affect the tone of retinal arterioles in vitro to induce dilatation mediated by A and Areceptors and constriction mediated by A and A receptors.

PURPOSE

To investigate effects of intravenous administration of the adenosine A receptor agonist regadenoson on the diameter of retinal vessels in vivo.

METHOD

The diameter responses of larger retinal arterioles and venules were evaluated using the dynamic vessel analyser in 20 normal persons (age 22-31 years) after intravenous administration of the adenosine A receptor agonist regadenoson during exposure to systemic normoxia and hypoxia.

RESULTS

The diameter of retinal arterioles and venules increased significantly during stimulation with flickering light ( < 0.0001). Regadenoson reduced the flicker-induced dilatation of venules during normoxia ( = 0.0006), but otherwise had no effect on vessel diameters ( > 0.08 for all comparisons).

CONCLUSIONS

Intravenous administration of the adenosine A receptor agonist regadenoson had no significant effect on the diameter of retinal arterioles. Future studies should investigate differential effects of intra- and extravascular administration of adenosine receptor agonists on retinal vessels.