The relation between excitation and adaptation within the rod's outer segment

Abstract

The relation between excitation and adaptation in vertebrate rod photoreceptors was studied by measuring the membrane current of toud rod outer segments in light and darkness. Steady illumination attenuated and sped the rod response to flashes, and it suppressed membrane current noise. When steady illumination ended, the rod's electrical response, and presumably the internal transmitter which caused it, decayed quickly, but adaptation's effects persisted temporarily. This new observation suggests that excitation and adaptation are loosely coupled phenomena which may be mediated by different chemical signals.