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Clemens Strohmaier, Dietmar Link, Bernd U. Seifert, Christian Runge, Barbara Bogner, Andrea Trost, Falk Schroedl, Walthard Vilser, Herbert A. Reitsamer; Retinal Vessel Diameter Analysis in the Rat: First Functional Results. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6046.
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To evaluate a novel retinal vessel analyzer for rats. Retinal vessels lack innervations and their diameter is controlled by local factors like oxygen and nitric oxide only. Oxygen and the nitric oxide synthase inhibitor L-NAME have well-known effects on the retinal arterial and venous diameter in other species. In rats, continuous, real time measurements of the retinal vessel diameters were not possible in the past due to a lack of appropriate instruments. Here, we present a novel instrument for retinal vessel analysis and use well known vasoactive agents for functional testing.
Anesthetised Male Brown-Norway rats (n= 12) were tracheotomized respired with room air. The ventilation parameters were chosen to keep the expired CO2 in at 40 mmHg. A catheter for blood pressure measurement was inserted into the right femoral artery and advanced to the aorta, another catheter was inserted into the right femoral vein for drug administration. Sodium hyaluronate eye drops were used to keep a stable tear film and the cornea moisture. The retinal vessel diameters were measured with a custom-made, non-contact fundus camera and the Imedos DVA software tool. This setup enables a continuous measurement of the retinal vessel diameters. After a 1 minute baseline measurement, 100% oxygen or L-NAME i.v. (5 mg/kg) were given and the vessel diameters were recorded over a period of 6 minutes.
The mean arterial blood pressure was 98,91 mmHg (oxygen group) and 87,34 mmHg (L-NAME group) and was stable during the measurements. Oxygen inhalation increased the blood pressure by 12 % after 6 minutes, it decreased the arterial vessel diameter by 13% and the venous diameter by 6 %. L-NAME application increased the blood pressure by 45 %, it decreased the arterial vessel diameter by 7 % and the venous diameter by 2 %.
This is the first continuous measurement of retinal vessel diameter in rats. The effects of oxygen inhalation and L-NAME are comparable to the effects published in the literature. The instrument presented enables the use of rat models for investigations of the role of retinal vessels in ocular diseases.
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