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Role of Nitric Oxide in Optic Nerve Head Blood Flow Regulation During Isometric Exercise in Healthy Humans

NCT00806741 · Status: COMPLETED · Phase: NA · Type: INTERVENTIONAL · Enrollment: 18

Last updated 2012-11-30

No results posted yet for this study

Summary

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.

Conditions

  • Healthy

Interventions

DRUG

NG-monomethyl-L-arginine (L-NMMA)

bolus 6mg/kg over 5 minutes followed by a continuous infusion of 60µg/kg/min over 15 minutes

DRUG

Phenylephrine

1μg/kg/min, infusion period 20 minutes

DRUG

Physiological saline solution (as placebo)

infusion period 20 minutes

DEVICE

Laser Doppler Flowmetry

blood flow measurements at the temporal neuroretinal rim of the optic nerve head

DEVICE

Goldmann applanation tonometer

intraocular pressure measurements

OTHER

squatting

Subjects will perform squatting for 6 minutes while blood flow is measured

Sponsors & Collaborators

  • Medical University of Vienna

    lead OTHER

Principal Investigators

  • Gabriele Fuchsjaeger-Mayrl, MD, Univ.Doz. · Medical University of Vienna

Study Design

Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
TRIPLE
Model
CROSSOVER

Eligibility

Min Age
18 Years
Max Age
35 Years
Sex
ALL
Healthy Volunteers
Yes

Timeline & Regulatory

Start
2009-09-30
Primary Completion
2010-03-31
Completion
2012-09-30

Countries

  • Austria

Study Locations

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Read the full study record

This page highlights key information. For complete eligibility criteria, study locations, investigator contacts, and the full protocol, visit the original record on ClinicalTrials.gov.

View NCT00806741 on ClinicalTrials.gov