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Alexandra Luksch, Kaija Polak, Carolin Beier, Elzbieta Polska, Michael Wolzt, Guido T. Dorner, Hans–Georg Eichler, Leopold Schmetterer; Effects of Systemic NO Synthase Inhibition on Choroidal and Optic Nerve Head Blood Flow in Healthy Subjects. Invest. Ophthalmol. Vis. Sci. 2000;41(10):3080-3084.
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purpose. There is evidence from animal studies that nitric oxide (NO) is a major
determinant of ocular blood flow. In humans NO synthase inhibition
reduces pulsatile choroidal blood flow, but no data on optic nerve head
(ONH) vasculature are available yet. The goal of this study was
to investigate the effects of NO synthase inhibition on human choroidal
and ONH blood flow using laser Doppler flowmetry.
methods. The study design was a randomized, placebo-controlled, double-masked,
balanced three-way crossover. On separate study days 12 healthy male
subjects received infusions of N G-nitro-l-arginine (L-NMMA;
either 3 mg/kg over 5 minutes followed by 30 μg/kg per minute over 55
minutes or 6 mg/kg over 5 minutes followed by 60 μg/kg per minute
over 55 minutes) or placebo. The effects of L-NMMA or placebo on
choroidal and ONH blood flow were measured with laser Doppler
flowmetry. In addition, laser interferometric measurement of fundus
pulsation was performed in the macula to assess pulsatile choroidal
results. L-NMMA reduced all outcome parameters in the choroid and the ONH. The
higher dose of L-NMMA caused a significant decrease in blood flow in
the choroid (−26% ± 9%; P < 0.001) and the ONH
(−20% ± 16%; P < 0.001) as evidenced from
laser Doppler flowmetry and a significant decrease in fundus pulsation
amplitude (−26% ± 5%; P < 0.001).
conclusions. These results indicate that NO is continuously released in human
choroidal and ONH vessels.
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