Effects of atropine and propranolol on retinal vessel diameters during isometric exercise.
OBJECTIVE
There is controversy regarding the nervous control of retinal blood vessels in humans. Most in vitro studies indicate that the intraocular part of the central retinal artery lacks autonomic innervation. We investigated the response of retinal vessels to isometric exercise during blockade of beta-receptors (propranolol) or muscarinic receptors (atropine).


METHODS
Twelve healthy subjects performed squatting for 6 min during infusion of either propranolol atropine or placebo. Blood pressure and pulse rate were measured non-invasively. Retinal vessel diameters were measured continuously using the Zeiss Retinal Vessel Analyser.


RESULTS
Squatting induced a significant increase in blood pressure and pulse rate, which was paralleled by a decrease in retinal vein and artery diameters. Atropine did not change the retinal vessel response to isometric exercise. Propranolol significantly blunted the exercise-induced vasoconstriction in retinal arteries.


CONCLUSIONS
This result likely indicates propranolol-evoked vasoconstriction in the extraocular parts of the central retinal artery during isometric exercise.
Jandrasits
K
K
Department of Clinical Pharmacology, University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria.
Polak
K
K
Luksch
A
A
Stark
B
B
Dorner
G T
GT
Eichler
H G
HG
Schmetterer
L
L
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000328:Adult; D001285:Atropine / Q000494:pharmacology*; D001341:Autonomic Nervous System / Q000502:physiology; D001794:Blood Pressure; D018592:Cross-Over Studies; D004311:Double-Blind Method; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate; D006706:Homeostasis / Q000187:drug effects; D006801:Humans; D008297:Male; D018727:Muscarinic Antagonists / Q000494:pharmacology*; D011433:Propranolol / Q000494:pharmacology*; D012171:Retinal Vessels / Q000187:drug effects / Q000294:innervation / Q000502:physiology*; D014661:Vasoconstriction / Q000187:drug effects
D000319:Adrenergic beta-Antagonists; D018727:Muscarinic Antagonists; D001285:Atropine; D011433:Propranolol