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

Not Applicable

Completed

• Conditions: Healthy
• Interventions: Drug: Phenylephrine; Drug: NG-monomethyl-L-arginine (L-NMMA); Drug: Physiological saline solution (as placebo); Device: Laser Doppler Flowmetry; Device: Goldmann applanation tonometer; Other: squatting

• Registration Number: NCT00806741
• Lead Sponsor: Medical University of Vienna

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.

Detailed Description

Not available

Study Timeline

• Study First Submitted: 2008-12-10
• Study First Submitted QC: 2008-12-10
• Study First Posted: 2008-12-11
• Study Start: 2009-09
• Primary Completion: 2010-03
• Study Completion: 2012-09
• Status Verified: 2012-11
• Last Update Submitted: 2012-11-29
• Last Update Posted: 2012-11-30

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 18

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 & Design

• Study Type: INTERVENTIONAL
• Study Design: CROSSOVER

Arm && Interventions

Group	Intervention	Description
3	Goldmann applanation tonometer	Physiological saline solution
2	Phenylephrine	Phenylephrine
2	squatting	Phenylephrine
3	squatting	Physiological saline solution
1	NG-monomethyl-L-arginine (L-NMMA)	NG-monomethyl-L-arginine (L-NMMA)
2	Laser Doppler Flowmetry	Phenylephrine
2	Goldmann applanation tonometer	Phenylephrine
3	Laser Doppler Flowmetry	Physiological saline solution
1	Laser Doppler Flowmetry	NG-monomethyl-L-arginine (L-NMMA)
1	Goldmann applanation tonometer	NG-monomethyl-L-arginine (L-NMMA)
1	squatting	NG-monomethyl-L-arginine (L-NMMA)
3	Physiological saline solution (as placebo)	Physiological saline solution

Primary Outcome Measures

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

Trial Locations

Locations (1)

Department of Clinical Pharmacology, Medical University of Vienna; 🇦🇹 Vienna, Austria