The study of the functional organization of the first synapse of the centripetal visual pathway at the outer plexiform layer level (OPL) ought to be made through the application of combined histological, electrophysiological, and neurochemical techniques. A large amount of new evidence has been accumu lated in the past 20 years on the structure of the retina and on the electrical responses of retinal cells to light stimulus. Also, recently, many substances considered as neurotransmitters in the brain have been found in the retina. The goal of the study of retinal function is to integrate the...