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Choroidal Blood Flow Regulation During Isometric Exercise: Effects of Ca2+-Channel Blockade

NCT00280462 · Status: COMPLETED · Phase: NA · Type: INTERVENTIONAL · Enrollment: 21

Last updated 2008-07-09

No results posted yet for this study

Summary

Autoregulation is the ability of a vascular bed to maintain blood flow despite changes in perfusion pressure. For a long time it had been assumed that the choroid is a strictly passive vascular bed, which shows no autoregulation. However, recently several groups have identified some autoregulatory capacity of the human choroid. In the brain and the retina the mechanism behind autoregulation is most likely linked to changes in transmural pressure. In this model arterioles change their vascular tone depending on the pressure inside the vessel and outside the vessel. In the choroid, several observations argue against a direct involvement of arterioles. In a previous project we were able to identify that the nitric oxide (NO) - system as well as the endothelin system are involved in choroidal blood flow regulation during isometric exercise.

In the present study autoregulation of the choroid during isometric exercise will be investigated and the pressure/flow relationships will be observed in the absence or presence of a calcium antagonist - nifedipine.

Conditions

  • Ocular Physiology
  • Regional Blood Flow

Interventions

DRUG

Nifedipine (drug)

Nifedipine (Adalat®, Bayer, Leverkusen, Germany) dose: 15µg/kg bolus infusion over 5 minutes; 0.2 µg/(kg.min) maintenance dose infusion period 25 minutes

DRUG

L-Arginin (drug)

L-Arginin (Clinalfa AG, Läufelfingen, Switzerland) 30% sodium chlorid solution, dose: 1g/min over 30 minutes

DRUG

Placebo

Placebo

Sponsors & Collaborators

  • Medical University of Vienna

    lead OTHER

Principal Investigators

  • Gabriele Fuchsjäger-Mayrl, M.D. · Department of Clinical Pharmacology, Medical University of Vienna

Study Design

Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
DOUBLE
Model
CROSSOVER

Eligibility

Min Age
19 Years
Max Age
35 Years
Sex
MALE
Healthy Volunteers
Yes

Timeline & Regulatory

Start
2005-08-31
Primary Completion
2006-04-30
Completion
2006-04-30

Countries

  • Austria

Study Locations

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Entities

Drugs

Read the full study record

This page highlights key information. For complete eligibility criteria, study locations, investigator contacts, and the full protocol, visit the original record on ClinicalTrials.gov.

View NCT00280462 on ClinicalTrials.gov