Blue-sensitive cones of the cat produce a rodlike electroretinogram

Abstract

Two cone mechanisms are identifiable in the strongly yellow light-adapted electroretinogram (ERG) of the arterially perfused cat eye. One has its maximum spectral sensitivity near 555 nm; the other has its maximum near 450 nm. The former cone system produces a much larger signal with characteristics of a typical cone or inhibitory ERG. The latter cone system produces a small, saturable signal (less than 5 microV) which resembles a rodlike or excitatory ERC. The results imply that the latter ERG is generated by blue-sensitive cones, which form a small fraction of the total cone population and share some physiological and perhaps anatomical properties of rods.