Studies on responsiveness of rat retial blood vessels with a newly developed digital funduscope system for small animals

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Retinal arterioles and venules are only central blood vessels that can be observed directly from outside of the body without any surgical procedures. To investigate responsiveness of these blood vessels of the rat, we established a new digital funduscope system that includes a video camera equipped with a 410,000-pixel CCD and a special objective lens for observation of the retina of small animals, such as rats, guinea pigs, rabbits, etc..Male Wistar rats were anesthetized with urethane or sodium thiobutabarbital. Polyethylene cannulae were inserted into femoral artery and femoral vein to monitor arterial pressure (AP) and heart rate and to administer drugs, respectively. Images of the retina were captured by a digital funduscope and recorded on a digital video tape. Changes in diameters of retinal blood vessels (DV) induced by various vasoactive drugs were calculated on a personal computer after making some graphic effects.Nicardipine (1-30μg/kg) lowered AP and increased DV. Nifedipine (10-100μg/kg) lowered AP, but did not affect DV. Flunarizine (1-30μg/kg) did not change AP, but increased DV. Ibudilast (0.1-1.0 mg/kg) and vinpocetine (0.1-1.0 mg/kg) increased DV without any effect on AP.These data demonstrate that changes in DV of rats in response to drugs can be monitored by our newly developed experimental system. Since retinal and cerebral blood vessels are similar in many aspects, our method might be useful for screening of drugs that alter not only retinal but also cerebral circulation.