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Autoregulation is defined as the ability of a vascular bed to adapt its vascular resistance to changes in perfusion pressure. In the eye, several studies have reported that retinal blood flow is autoregulated over a wide range of ocular perfusion pressures. The investigators recently showed that nitric oxide (NO) is a key metabolite in the regulation of vascular tone in the eye and plays an important role in the blood flow autoregulation of the choroidal circulation. However, no data is yet available for the optic nerve head. Thus, the present study is designed to test the hypothesis that NO plays also a role in optic nerve head blood flow autoregulation. Therefore, subjects will perform squatting to increase systemic perfusion pressure during administration of either a nitric oxide synthase inhibitor (L-NMMA), an α-receptor agonist (phenylephrine) or placebo. Optic nerve head blood flow will be continuously measured during the procedure to investigate optic nerve head autoregulation.
Allocation: Randomized, Control: Placebo Control, Endpoint Classification: Safety/Efficacy Study, Intervention Model: Crossover Assignment, Masking: Double Blind (Subject, Investigator, Outcomes Assessor), Primary Purpose: Basic Science
NG-monomethyl-L-arginine (L-NMMA), Phenylephrine, Physiological saline solution (as placebo), Laser Doppler Flowmetry, Goldmann applanation tonometer, squatting
Department of Clinical Pharmacology, Medical University of Vienna
Not yet recruiting
Medical University of Vienna
Published on BioPortfolio: 2014-08-27T03:25:43-0400
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