Effects of atropine and propranolol on retinal vessel diameters during isometric exercise

Purpose: There is controversy regarding the nervous control of retinal bloo d vessels in humans. Most in vitro studies indicate that the intraocular pa rt of the central retinal artery lacks autonomic innervation. We investigat ed the response of retinal vessels to isometric exercise during blockade of P-receptors (propranolol) or muscarinic receptors (atropine). Methods: Twe lve healthy subjects performed squatting for 6 min during infusion of eithe r propranolol atropine or placebo. Blood pressure and pulse rate were measu red non-invasively. Retinal vessel diameters were measured continuously usi ng the Zeiss Retinal Vessel Analyser. Results: Squatting induced a signific ant increase in blood pressure and pulse rate, which was paralleled by a de crease in retinal vein and artery diameters. Atropine did not change the re tinal vessel response to isometric exercise. Propranolol significantly blun ted the exercise-induced vasoconstriction in retinal arteries. Conclusion: This result likely indicates propranolol-evoked vasoconstriction in the ext raocular parts of the central retinal artery during isometric exercise. Cop yright (C) 2001 S. Karger AG, Basel.