Role of Nitric Oxide in Optic Nerve Head Blood Flow Regulation During Isometric Exercise in Healthy Humans
Status:
Completed
Trial end date:
2012-09-01
Target enrollment:
Participant gender:
Summary
Autoregulation is defined as the ability of a vascular bed to adapt its vascular resistance
to changes in perfusion pressure. In the eye, several studies have reported that retinal
blood flow is autoregulated over a wide range of ocular perfusion pressures. The
investigators recently showed that nitric oxide (NO) is a key metabolite in the regulation of
vascular tone in the eye and plays an important role in the blood flow autoregulation of the
choroidal circulation. However, no data is yet available for the optic nerve head. Thus, the
present study is designed to test the hypothesis that NO plays also a role in optic nerve
head blood flow autoregulation. Therefore, subjects will perform squatting to increase
systemic perfusion pressure during administration of either a nitric oxide synthase inhibitor
(L-NMMA), an α-receptor agonist (phenylephrine) or placebo. Optic nerve head blood flow will
be continuously measured during the procedure to investigate optic nerve head autoregulation.