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

NCT ID: NCT00806741

Last Updated: 2012-11-30

Study Results

Results pending

The study team has not published outcome measurements, participant flow, or safety data for this trial yet. Check back later for updates.

Basic Information

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Recruitment Status

COMPLETED

Clinical Phase

NA

Total Enrollment

18 participants

Study Classification

INTERVENTIONAL

Study Start Date

2009-09-30

Study Completion Date

2012-09-30

Brief Summary

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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.

Detailed Description

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Conditions

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Healthy

Keywords

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

Study Design

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Allocation Method

RANDOMIZED

Intervention Model

CROSSOVER

Primary Study Purpose

BASIC_SCIENCE

Blinding Strategy

TRIPLE

Participants Investigators Outcome Assessors

Study Groups

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1

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

Group Type ACTIVE_COMPARATOR

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

Intervention Type DRUG

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

Laser Doppler Flowmetry

Intervention Type DEVICE

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

Goldmann applanation tonometer

Intervention Type DEVICE

intraocular pressure measurements

squatting

Intervention Type OTHER

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

2

Phenylephrine

Group Type ACTIVE_COMPARATOR

Phenylephrine

Intervention Type DRUG

1μg/kg/min, infusion period 20 minutes

Laser Doppler Flowmetry

Intervention Type DEVICE

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

Goldmann applanation tonometer

Intervention Type DEVICE

intraocular pressure measurements

squatting

Intervention Type OTHER

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

3

Physiological saline solution

Group Type PLACEBO_COMPARATOR

Physiological saline solution (as placebo)

Intervention Type DRUG

infusion period 20 minutes

Laser Doppler Flowmetry

Intervention Type DEVICE

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

Goldmann applanation tonometer

Intervention Type DEVICE

intraocular pressure measurements

squatting

Intervention Type OTHER

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

Interventions

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

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

Intervention Type DRUG

Phenylephrine

1μg/kg/min, infusion period 20 minutes

Intervention Type DRUG

Physiological saline solution (as placebo)

infusion period 20 minutes

Intervention Type DRUG

Laser Doppler Flowmetry

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

Intervention Type DEVICE

Goldmann applanation tonometer

intraocular pressure measurements

Intervention Type DEVICE

squatting

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

Intervention Type OTHER

Eligibility Criteria

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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
Minimum Eligible Age

18 Years

Maximum Eligible Age

35 Years

Eligible Sex

ALL

Accepts Healthy Volunteers

Yes

Sponsors

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Medical University of Vienna

OTHER

Sponsor Role lead

Responsible Party

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Gerhard Garhofer

Assoc. Prof. PD Dr.

Responsibility Role PRINCIPAL_INVESTIGATOR

Principal Investigators

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Gabriele Fuchsjaeger-Mayrl, MD, Univ.Doz.

Role: PRINCIPAL_INVESTIGATOR

Medical University of Vienna

Locations

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Department of Clinical Pharmacology, Medical University of Vienna

Vienna, , Austria

Site Status

Countries

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Austria

References

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Schmidl D, Boltz A, Kaya S, Lasta M, Pemp B, Fuchsjager-Mayrl G, Hommer A, Garhofer G, Schmetterer L. Role of nitric oxide in optic nerve head blood flow regulation during isometric exercise in healthy humans. Invest Ophthalmol Vis Sci. 2013 Mar 15;54(3):1964-70. doi: 10.1167/iovs.12-11406.

Reference Type DERIVED
PMID: 23439596 (View on PubMed)

Other Identifiers

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OPHT-300708

Identifier Type: -

Identifier Source: org_study_id