The Effect of A2A Adrenoceptor Stimulation on the Diameter of Retinal Arterioles During Hypoxia in Vivo

The purpose is to investigate how the adenosine affects the diameter regulation of retinal arterioles during changes in oxygen tension. A deeper understanding of the mechanisms involved in diameter regulation of retinal arterioles during changes in oxygen tension can be used to obtain a more detailed understanding of diseases where changes in the diameter regulation of retinal vessels are involved in the disease pathogenesis and possibly point to new therapeutic options for patients with retinal vascular disease, such as diabetic retinopathy and retinal vein thrombosis. Preliminary, a routine ophthalmological evaluation, measurement of blood pressure, and electrocardiogram will be preformed to insure that only healthy test persons are included in the study. The test persons will be randomly allocated to two groups, one group in which protocol 1 is followed by protocol 2, and the other group with the two protocols performed in the reverse order. Protocol 1: Using the DVA, a video recording will capture the diameter of retinal vessels and the changes occurring during stimulation with flickering light. The recording lasts 4.5 minutes and is preformed before and after intravenous injection of adenosine. Protocol 2: The procedures are similar to those of protocol 1 but are performed during breathing of a gas mixture with a reduced oxygen tension to 12,5 %, which results in a reduced oxygen saturation in the blood to 85-90 %.