NCT00280462

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

• Status: Completed
• Phase: N/A
• Study type: Interventional
• Enrollment: 21 (actual)
• Sponsor: Medical University of Vienna · Academic / Other
• Sex: Male
• Age: 19 Years – 35 Years
• Healthy volunteers: Accepted

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

Type	Name	Description
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

Timeline

• Start date: 2005-08-01
• Primary completion: 2006-04-01
• Completion: 2006-04-01
• First posted: 2006-01-23
• Last updated: 2008-07-09

Locations

1 site across 1 country: Austria