Changes induced in spectral sensitivity and form of retinal action potential of the cockroach eye by selective adaptation

Abstract

The relative spectral sensitivity and the shape of the slow monophasic action potential of the compound eye of the cockroach, Periplaneta americana L., were investigated using monochromatic light for stimulation and adaptation. It was demonstrated that different areas of this eye differ in function. Ventral parts show a one-peak spectral sensitivity curve (maximum at about 507 mμ) which is unaltered by the state of adaptation. Spectral sensitivity of areas at the upper edge of the eye shows the same maximum as a result of dark adaptation, but the sensitivity curve rises towards violet wavelengths. Adaptation with monochromatic light changes the relative spectral sensitivity considerably. Colour specific differences in the shape of the action potential are seen in the latter areas only. The results indicate that two receptor systems exist in the cockroach eye, which differ in spectral sensitivity and which may mediate true colour vision, at least in the blue-green and violet range of the spectrum. The meaning of the different time course of potentials following stimulation with different colours is discussed.