In vitro dark adaptation and preservation of electrical light responses in the retina from bovine eyes.

A method is described which allows the in vitro dark adaptation of rod photoreceptors from cattle eyes, enucleated under ambient light in the slaughterhouse. Without in vitro dark adaptation these eyes are light adapted and cannot be used for certain delicate biochemical studies and for an electrophysiological characterisation of rod responses. The method is very simple and yields large amounts of dark adapted retinal material, allowing experiments that require bulk amounts of photoreceptor cells. The only source of dark adapted photoreceptors so far have been retinae from dark adapted laboratory animals, which had to be killed and processed under infrared light. Eye cups were opened under red light as soon as possible after their enucleation. Their vitreous humor was removed and their retina thoroughly rinsed with ringer's. Then the eye cup was placed in a moist, light-tight box, where dark adaptation took place. Photoreceptors could thus be kept alive for more than 24 h without showing signs of deterioration. Humidity and free access of oxygen to the retina were the only prerequisites for their survival. The physiological intactness of the photoreceptors and their degree of dark adaptation was demonstrated by measuring mass receptor potentials (ERGs). A simple device is described which can be used for the electrophysiological characterisation of these eyes.