Quercetin Dilates Retinal Arterioles via Nitric Oxide-Dependent Mechanisms in Rats

The purpose of this study was to investigate whether quercetin, a flavonoid abundantly found in onion leaves and other plant foods, induces the dilation of retinal blood vessels in rats. The time-course changes in retinal arteriolar diameter were measured using a retinal circulation evaluation system based on a high-resolution digital fundus camera developed in our laboratory. The intravenous administration of quercetin (10-100 µg/kg/min) increased the retinal arteriolar diameter in a dose-dependent manner. This vasodilatory effect of quercetin was almost completely suppressed through an intravitreal pretreatment with N_ω-nitro-l-arginine methyl ester (l-NAME), a nitric oxide (NO) synthase inhibitor. In contrast, the systemic intravenous infusion of quercetin did not cause significant changes in the systemic blood pressure and heart rate. These results suggest that NO production plays an important role in the quercetin-induced dilation of retinal arterioles. Quercetin, which is abundantly present in several plant foods and possesses antioxidant properties, may be a useful agent for the prevention of various ocular diseases associated with visual impairment caused by reduced retinal blood flow.