Mechanisms of Choroidal Blood Flow Changes During Dark/Light Transitions

Condition(s) targeted: Regional Blood Flow; Ocular Physiology

Intervention: Phenylephrine (Drug); NG-Monomethyl-L-Arginine (Drug); Propanolol (Drug); Atropine (Drug)

Phase: Phase 2

Status: Completed

Sponsored by: Medical University of Vienna

Official(s) and/or principal investigator(s):
Michael Wolzt, MD, Principal Investigator, Affiliation: Department of Clinical Pharmacology, Medical University of Vienna

There is evidence from a variety of animal studies that choroidal blood flow is under neural control. By contrast, only little information is available from human studies. Recent results indicate that a light/dark transition is associated with a short lasting reduction in choroidal blood flow. We have shown that during unilateral dark/light transition both eyes react with choroidal vasoconstriction strongly indicating a neural mechanism.

The present studies investigate this possibility by using pharmacological interventions. The pharmacological agents tested include a nitric oxide synthase inhibitor, an alpha-receptor agonist (as a control substance for the blood pressure increasing nitric oxide synthase inhibitor), a muscarinic receptor blocker, and a non-specific beta-blocker. These drugs were chosen on the basis of previous animal experiments, as the systems, which are specifically influenced by these substances, are likely involved in neural control of choroidal blood flow.

Official title: Mechanisms of Choroidal Blood Flow Changes During Dark/Light Transitions

Study design: Treatment, Randomized, Double-Blind, Placebo Control, Crossover Assignment, Safety/Efficacy Study

Primary outcome:

choroidal blood flow

fundus pulsation amplitude

Minimum age: 19 Years. Maximum age: 35 Years. Gender(s): Male.

Criteria:

Inclusion Criteria:

- Men aged between 19 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 < 3 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 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

Department of Clinical Pharmacology, Medical University of Vienna, Vienna 1090, Austria

Starting date: September 2001
Last updated: February 2, 2007