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Seigo Nakabayashi, Taiji Nagaoka, Tomofumi Tani, Kenji Sogawa, Akitoshi Yoshida; Effect of Acute Increase in Systemic Blood Pressure on Retinal Microcirculation in Cats: Role of Nitric Oxide, Prostanoids, Endothelin, and Rho Kinase. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6033.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the regulation of the retinal circulation during acute increases in feline systemic blood pressure (BP).
Two hours after NG-nitro-L-arginine-methyl ester (L-NAME), a nitric oxide (NO) synthase inhibitor; indomethacin, a cyclooxygenase inhibitor; BQ-123, an endothelin A receptor antagonist; fasudil, a rho kinase inhibitor; or vehicles (phosphate buffered saline [PBS], sodium carbonate) were injected intravitreously, acute increases in systemic BP were induced for 5 minutes by inflating a balloon-tipped catheter placed at the descending aorta. The vessel diameter and blood velocity were measured simultaneously in the first-order retinal arterioles by laser Doppler velocimetry (CLBF model 100, Canon); the retinal blood flow (RBF) and retinal vascular resistance (RVR) were calculated.
In the PBS group, the mean BP increased by about 60% compared with baseline (from 95.6 ± 1.8 to 151.4 ± 2.0 mmHg) 5 minutes after catheter inflation. The blood velocity and RBF rapidly increased; the vessel diameter gradually decreased in response to acute increases in systemic BP. In the L-NAME group, the vessel diameter rapidly decreased in response to acute increases in systemic BP, resulting in no significant change in the RBF. Indomethacin reduced the late phase of the increased RBF. BQ-123 enhanced the systemic hypertension-induced increases in RBF compared with PBS. In the fasudil group, the vessel diameter did not change and the increases in blood velocity and RBF were enhanced, with no change in RVR.
Our data suggested that RBF increases in response to acute increases in systemic BP induced by catheter inflation and that NO and vasodilating prostanoids may be involved in these increases in RBF. However, endothelin A receptor and rho kinase resulted in counteractive constriction of retinal arterioles in response to systemic hypertension. Retinal vascular endothelial cells may regulate RBF by releasing various vasoactive substances during acute increases in systemic BP.
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