Subcomponents of PIII in Cold-blooded Vertebrate Retinae

Abstract

IT is generally accepted that the PII component of the vertebrate electroretinogram (ERG) arises in the bipolar cell layer. The origin of the PIII component, however, is still the subject of controversy. From experiments on the mammalian retina in situ, Brown and Wiesel^1,2 and Brown and Watanabe³ conclude that the receptor cell layer is the origin of PIII, while Tomita⁴, working on cold-blooded retinae, emphasizes the bipolar cell layer as the main origin of PIII. He observed more recently that, in the excised opened eye of the frog, a small fraction of PIII persists distal to the bipolar cell layer after the abolition of PII and the greater part of PIII by sodium azide. This suggests that PIII is made up of more than one component from different retinal layers⁴. This suggestion is strongly supported by our depth-recording experiment on isolated inverted retinae of cold-blooded vertebrates. The carp, frog and turtle were used with substantially the same result.