title: Propranolol and atropine do not alter choroidal blood flow regulation during isometric exercise in healthy humans.
abstract: Recent studies indicate that the human choroid has a considerable capacity to keep blood flow constant despite exercise-induced increases in perfusion pressure. The mechanisms underlying this vasoconstrictor response remain unclear. We hypothesized that pharmacological modulation of the autonomic nervous system may alter the choroidal pressure/flow relationship during squatting. To test this hypothesis, we performed a randomized, double-masked, placebo-controlled, three-way crossover study in 15 healthy male volunteers. Subjects received, on different study days, intravenous infusions of the beta-adrenoceptor antagonist propranolol, the muscarinic receptor antagonist atropine, or placebo. During these infusions, subjects performed squatting for 6 min. Choroidal blood flow was assessed with laser Doppler flowmetry and ocular perfusion pressure (OPP) was calculated from mean arterial pressure and intraocular pressure. As expected, propranolol reduced basal pulse rate, whereas atropine increased pulse rate, indicating that the drugs were administered at systemically effective doses. None of the drugs altered the choroidal pressure/flow relationship during isometric exercise. These data indicate that the regulatory vasoconstrictor capacity of the choroid during exercise is not affected by systemic blockade of beta-adrenoceptors or muscarinic receptors.
authors.affiliation: Department of Clinical Pharmacology, University of Vienna, Vienna, Austria.
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Polska
authors.forename: Alexandra
authors.initials: A
authors.lastname: Luksch
authors.forename: Joanne
authors.initials: J
authors.lastname: Schering
authors.forename: Barbara
authors.initials: B
authors.lastname: Frank
authors.forename: Andrea
authors.initials: A
authors.lastname: Imhof
authors.forename: Gabriele
authors.initials: G
authors.lastname: Fuchsjäger-Mayrl
authors.forename: Michael
authors.initials: M
authors.lastname: Wolzt
authors.forename: Leopold
authors.initials: L
authors.lastname: Schmetterer
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000328:Adult; D001285:Atropine / Q000494:pharmacology*; D001341:Autonomic Nervous System / Q000187:drug effects / Q000502:physiology; D001783:Blood Flow Velocity / Q000187:drug effects; D002829:Choroid / Q000098:blood supply* / Q000187:drug effects*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D015444:Exercise / Q000502:physiology*; D006706:Homeostasis; D006801:Humans; D008297:Male; D018727:Muscarinic Antagonists / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology*; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology
chemical_list: D000319:Adrenergic beta-Antagonists; D018727:Muscarinic Antagonists; D001285:Atropine; D011433:Propranolol