Clinical trial NCT00806741: Role of Nitric Oxide in Optic Nerve Head Blood Flow Regulation During Isometric Exercise in Healthy Humans
Official title: Role of Nitric Oxide in Optic Nerve Head Blood Flow Regulation During Isometric Exercise in Healthy Humans
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Healthy
Keywords: L-NG-Monomethyl Arginine
Optic Nerve Head blood flow
Intraocular Pressure
Regional blood flow
Ocular Physiology
Optic Disk
Lead sponsor: Medical University of Vienna
Sponsor class: OTHER
First posted: 2008-12-11
Enrollment: 18
Sex: ALL
Minimum age (years): 18
Maximum age (years): 35
Standard ages: ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: CROSSOVER
Primary purpose: BASIC_SCIENCE

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.


Eligibility criteria: 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

Primary outcomes:
measure: Optic nerve head pressure-flow relationship
timeFrame: in total 6x on 3 study days
Secondary outcomes:
Other outcomes:
Locations:
city: Vienna
country: Austria
facility: Department of Clinical Pharmacology, Medical University of Vienna
Study officials:
affiliation: Medical University of Vienna
name: Gabriele Fuchsjaeger-Mayrl, MD, Univ.Doz.
role: PRINCIPAL_INVESTIGATOR
References:
citation: 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.