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G Garhofer, C Zawinka, K-H Huemer, GT Dorner, L Schmetterer; Effect of Short Time Exercise on Flicker Induced Vasodilatation . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3310.
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Purpose:Flicker stimulation is known to increase retinal arterial and venous diameter in animals and humans. The aim of the present study was to investigate the influence of increased lactate levels induced by short time exercise on the response of retinal vessels to photic stimulation. Methods:The study was performed in 12 healthy, male, less trained subjects. Diameters of retinal vessels were recorded continously with the Zeiss Retinal Vessel Analyzer over 3 minutes including 1 minute of square wave flicker stimulation at 8 Hz. Recordings were made at baseline and 1, 10 and 20 minutes after 6 minutes of bicycling. Blood lactate levels were measured with a reflectance photometer. Results:Flicker stimulation induced a vasodilatation of 5.3%0.9% (meanSEM) in retinal arteries and 3.5%2.1% in retinal veins at baseline lactate levels of 1.20.3 mmol/l. Exercise increased blood lactate levels to 13.83.9 mmol/l. At this lactate level, the flicker response was significantly reduced to 2.3%0.9% (p<0.03). 10 minutes and 20 minutes after exercise, at a lactate level of 9.91.1 mmol/l and 4.50.6 mmol/l, respectively, flicker response in retinal arteries was still reduced (1.7%0.6%, p<0.01; 2.8%0.8%, p<0.03). Conclusion:Increased lactate levels significantly reduce flicker induced responses of retinal arteries in healthy volunteers. This is compatible with the hypothesis that lactate is a sensor of blood flow in the retina. Flicker induced vasodilatation may depend on cytosolic NADH/NAD+, which is near-equilibrium with the lactate/pyruvate ratio.
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