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Role of Endothelin- and Nitric Oxide-system in the Regulation of Optic Nerve Head Blood Flow During Changes in Ocular Perfusion Pressure

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ClinicalTrials.gov Identifier: NCT00406731
Recruitment Status : Withdrawn
First Posted : December 4, 2006
Last Update Posted : August 15, 2019
Sponsor:
Information provided by (Responsible Party):
Gerhard Garhofer, Medical University of Vienna

Study Description
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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).


Condition or disease Intervention/treatment Phase
Ocular Physiology Optic Disk Regional Blood Flow Drug: NG-monomethyl-L-arginine (L-NMMA) Drug: Endothelin-1 (ET-1) Drug: Physiologic saline solution (placebo control) Device: Laser Doppler flowmetry Device: Goldmann applanation tonometer Device: HP-CMS patient monitor Procedure: Suction cup method Phase 2

Study Design
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Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 0 participants
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary Purpose: Treatment
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 Start Date : January 2008
Actual Primary Completion Date : November 2014
Actual Study Completion Date : November 2014
Arms and Interventions
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Intervention Details:
  • Drug: NG-monomethyl-L-arginine (L-NMMA)
    bolus 6 mg/kg over 5 minutes followed by a continuous intravenous infusion of 60 µg/kg/min over 12 minutes; twice on 1 study day
  • Drug: Endothelin-1 (ET-1)
    5 ng/kg/min intravenous infusion over 17 minutes; twice on 1 study day
  • Drug: Physiologic saline solution (placebo control)
    intravenous infusion over 20 minutes; twice on 1 study day
  • Device: Laser Doppler flowmetry
    blood flow measurements at the temporal neuroretinal rim of the optic nerve head
  • Device: Goldmann applanation tonometer
    Intraocular pressure measurements
  • Device: HP-CMS patient monitor
    blood pressure and pulse rate measurements
  • Procedure: Suction cup method
    The IOP will be raised by an 11 mm diameter, standardized suction cup placed on the temporal sclera with the anterior edge at least 1 mm from the limbus.

Outcome Measures
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Primary Outcome Measures :
  1. ONH pressure-flow relationship [ Time Frame: up to 3 study days ]

Eligibility Criteria
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Ages Eligible for Study:   18 Years to 35 Years   (Adult)
Sexes Eligible for Study:   Male
Accepts Healthy Volunteers:   Yes
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
Contacts and Locations
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Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT00406731


Locations
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Austria
Department of Clinical Pharmacology, Medical University of Vienna
Vienna, Austria, 1090
Sponsors and Collaborators
Medical University of Vienna
Investigators
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Principal Investigator: Gabriele Fuchsjaeger-Mayrl, MD,Univ.Doz. Department of Clinical Pharmacology, Medical University of Vienna
More Information
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Responsible Party: Gerhard Garhofer, Assoc. Prof. PD Dr., Medical University of Vienna
ClinicalTrials.gov Identifier: NCT00406731    
Other Study ID Numbers: OPHT-080206
First Posted: December 4, 2006    Key Record Dates
Last Update Posted: August 15, 2019
Last Verified: August 2019
Keywords provided by Gerhard Garhofer, Medical University of Vienna:
Endothelin-1
L-NG-Monomethyl Arginine
Optic Nerve Head blood flow
Additional relevant MeSH terms:
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omega-N-Methylarginine
Enzyme Inhibitors
Molecular Mechanisms of Pharmacological Action