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

Status

Completed

Phases

Study type

Interventional

Source

ClinicalTrials.gov

Registry ID

NCT00806741

Enrollment

Registered

2008-12-11

Start date

2009-09-30

Completion date

2012-09-30

Last updated

2012-11-30

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

Healthy

Keywords

L-NG-Monomethyl Arginine, Optic Nerve Head blood flow, Intraocular Pressure, Regional blood flow, Ocular Physiology, Optic Disk

Brief 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.

Interventions

DRUGNG-monomethyl-L-arginine (L-NMMA)

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

DRUGPhenylephrine

1μg/kg/min, infusion period 20 minutes

DRUGPhysiological saline solution (as placebo)

infusion period 20 minutes

DEVICELaser Doppler Flowmetry

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

DEVICEGoldmann applanation tonometer

intraocular pressure measurements

OTHERsquatting

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

Study design

Allocation

RANDOMIZED

Intervention model

CROSSOVER

Primary purpose

BASIC_SCIENCE

Masking

TRIPLE (Subject, Investigator, Outcomes Assessor)

Eligibility

Sex/Gender

ALL

Age

18 Years to 35 Years

Healthy volunteers

Yes

Inclusion criteria

* Men and women aged between 18 and 35 years, nonsmokers * Men and women will be included in equal parts * Normal findings in the medical history and physical examination unless the investigator considers an abnormality to be clinically irrelevant * Normal findings in the laboratory testings unless the investigator considers an abnormality to be clinically irrelevant * Normal ophthalmic findings, ametropia less than 3 diopters

Exclusion criteria

* Regular use of medication, abuse of alcoholic beverages, participation in a clinical trial in the 3 weeks preceding the study * Treatment in the previous 3 weeks with any drug (except intake of oral contraceptives) * Symptoms of a clinically relevant illness in the 3 weeks before the first study day * History or presence of gastrointestinal, liver or kidney disease, or other conditions known to interfere with distribution, metabolism or excretion of study drugs * Blood donation during the previous 3 weeks * Pregnancy

Design outcomes

Primary

Measure	Time frame
Optic nerve head pressure-flow relationship	in total 6x on 3 study days

Countries

Austria

Outcome results

None listed

Source: ClinicalTrials.gov · Data processed: Mar 24, 2026