Choroidal Blood Flow Regulation During Isometric Exercise: Effects of Ca2+-Channel Blockade
Status:
Completed
Trial end date:
2006-04-01
Target enrollment:
Participant gender:
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.