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OpenTrials
Completed

NCT Number: NCT00806741

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

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.

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Key information

Conditions

Healthy

Age range

18 year–35 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Department of Clinical Pharmacology, Medical University of Vienna

Vienna, 1090, Austria

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

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

Treatment and study plan

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

Drug

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

Phenylephrine

Drug

1μg/kg/min, infusion period 20 minutes

Physiological saline solution (as placebo)

Drug

infusion period 20 minutes

Laser Doppler Flowmetry

Device

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

Goldmann applanation tonometer

Device

intraocular pressure measurements

squatting

Other

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

Primary outcomes

  1. Optic nerve head pressure-flow relationship

    Time frame: in total 6x on 3 study days

Sponsors and collaborators

Lead sponsor

Medical University of Vienna

Other

Registry information

Important dates

Study start
2009
Primary completion
2010
Study completion
2012
First posted
Dec 11, 2008
Registry last updated
Nov 30, 2012

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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