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

November 29, 2012 updated by: Gerhard Garhofer, Medical University of Vienna
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.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Actual)

18

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Austria
      • Vienna, Austria, 1090
        • Department of Clinical Pharmacology, Medical University of Vienna

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years to 35 years (Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

Description

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

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Basic Science
  • Allocation: Randomized
  • Interventional Model: Crossover Assignment
  • Masking: Triple

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Active Comparator: 1
NG-monomethyl-L-arginine (L-NMMA)
Device: Goldmann applanation tonometer
intraocular pressure measurements
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
Device: Laser Doppler Flowmetry
blood flow measurements at the temporal neuroretinal rim of the optic nerve head
Other: squatting
Subjects will perform squatting for 6 minutes while blood flow is measured
Active Comparator: 2
Phenylephrine
Device: Goldmann applanation tonometer
intraocular pressure measurements
Device: Laser Doppler Flowmetry
blood flow measurements at the temporal neuroretinal rim of the optic nerve head
Other: squatting
Subjects will perform squatting for 6 minutes while blood flow is measured
Drug: Phenylephrine
1μg/kg/min, infusion period 20 minutes
Placebo Comparator: 3
Physiological saline solution
Device: Goldmann applanation tonometer
intraocular pressure measurements
Device: Laser Doppler Flowmetry
blood flow measurements at the temporal neuroretinal rim of the optic nerve head
Other: squatting
Subjects will perform squatting for 6 minutes while blood flow is measured
Drug: Physiological saline solution (as placebo)
infusion period 20 minutes

What is the study measuring?

Primary Outcome Measures

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

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Medical University of Vienna

Investigators

  • Principal Investigator: Gabriele Fuchsjaeger-Mayrl, MD, Univ.Doz., Medical University of Vienna

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start

September 1, 2009

Primary Completion (Actual)

March 1, 2010

Study Completion (Actual)

September 1, 2012

Study Registration Dates

First Submitted

December 10, 2008

First Submitted That Met QC Criteria

December 10, 2008

First Posted (Estimate)

December 11, 2008

Study Record Updates

Last Update Posted (Estimate)

November 30, 2012

Last Update Submitted That Met QC Criteria

November 29, 2012

Last Verified

November 1, 2012

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • OPHT-300708

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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