Clinical trial NCT00406731: Role of Endothelin- and Nitric Oxide-system in the Regulation of Optic Nerve Head Blood Flow During Changes in Ocular Perfusion Pressure
Official title: Role of endothelin-and Nitric Oxide-system in the Regulation of Optic Nerve Head Blood Flow During Changes in Ocular Perfusion Pressure
Study type: INTERVENTIONAL
Overall status: WITHDRAWN
Phase: PHASE2
Conditions: Ocular Physiology
Optic Disk
Regional Blood Flow
Keywords: Endothelin-1
L-NG-Monomethyl Arginine
Optic Nerve Head blood flow
Lead sponsor: Medical University of Vienna
Sponsor class: OTHER
First posted: 2006-12-04
Enrollment: 0
Sex: MALE
Minimum age (years): 18
Maximum age (years): 35
Standard ages: ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: CROSSOVER
Primary purpose: TREATMENT

Brief summary: Autoregulation is the ability of a vascular bed to maintain blood flow despite changes in perfusion pressure. The existence of an effective autoregulation in the optic nerve circulation has been shown in animals and humans. The exact mechanism behind this autoregulation is still unknown. The motive for the investigation of optic nerve head (ONH) blood flow autoregulation is to enhance the understanding of pathologic eye conditions associated with ocular vascular disorders. To clarify the regulatory mechanisms of ONH microcirculation is of critical importance to understand the pathophysiology of glaucoma because there is evidence that glaucoma is associated with optic nerve head ischemia. Several studies indicate that a disturbed autoregulation might contribute to glaucomatous optic neuropathy. Previous findings suggest endothelial dysfunction in glaucomatous optic neuropathy, in particular alterations in endothelin- and nitric oxide- system, which both play an important role in local regulation of vascular tone.

In the present study, changes in ocular perfusion pressure will be performed during administration of drugs, which may potentially alter the pressure-flow relationship. These drugs include endothelin-1 and the nitric oxide synthase inhibitor NG-monomethyl-L-arginine (L-NMMA).


Eligibility criteria: Inclusion Criteria:

* Men aged between 18 and 35 years, nonsmokers
* Body mass index between 15th and 85th percentile (Must et al. 1991)
* Normal findings in the medical history and physical examination unless the investigator considers an abnormality to be clinically irrelevant
* Normal laboratory values unless the investigator considers an abnormality to be clinically irrelevant
* Normal ophthalmic findings, ametropy \< 1 Dpt

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
* Symptoms of a clinically relevant illness in the 3 weeks before the first study day
* History of hypersensitivity to the trial drug or to drugs with a similar chemical structure
* History or presence of systemic or pulmonary hypertension, or other cardiac or pulmonary diseases
* 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

Primary outcomes:
measure: ONH pressure-flow relationship
timeFrame: up to 3 study days
Secondary outcomes:
Other outcomes:
Locations:
city: Vienna
country: Austria
facility: Department of Clinical Pharmacology, Medical University of Vienna
Study officials:
affiliation: Department of Clinical Pharmacology, Medical University of Vienna
name: Gabriele Fuchsjaeger-Mayrl, MD,Univ.Doz.
role: PRINCIPAL_INVESTIGATOR
References: