Diameter Changes of Retinal Arterioles During Acute Hypoxia In Vivo are Modified by the Inhibition of Nitric Oxide and Prostaglandin Synthesis

Purpose: Inhibition of cyclooxygenase (COX) and nitric oxide synthesis (NOS) has previously been shown to modify hypoxia-induced relaxation of retinal arterioles in vitro. The purpose of the present study was to investigate whether these findings can be reproduced in vivo. Methods: Twenty healthy persons aged 20-55 years were examined. Using the dynamic vessels analyzer (DVA), the resting diameter and diameter changes during isometric exercise and flicker stimulation were studied before and during breathing of a hypoxic gas mixture. The examinations were carried out before and during intravenous infusion of the NOS-inhibitor l-NMMA, and were repeated on a second study day after topical administration of the COX-inhibitor diclofenac. Results: The resting diameter of retinal arterioles increased significantly during hypoxia and decreased significantly during l-NMMA infusion (p