Sensitizing activity of 9,13-dicis retinal in bleached photoreceptors of the skate.

9,13-dicis Retinal was externally applied to photoreceptors of isolated skate retina that previously had been desensitized by bleaching irradiation. This treatment led to a significant lowering of photoreceptor threshold and to the intracellular formation of isorhodopsin II, an artificial visual pigment containing 9,13-dicis retinal as its chromophore. These results suggest that isorhodopsin II can function in situ to promote an increase in the visual sensitivity of skate photoreceptors.