Effect of Hypoxia on the Change in Membrane Conductance evoked by Illumination in Arthropod Photoreceptors

Abstract

IN a wide variety of photoreceptor cells it has been established that the conductance of the cell membrane is altered by light and that the photoreceptor potential is a direct consequence of this change. In the studies reported so far the membrane conductance of vertebrate photoreceptors^1,2 falls on illumination (with the exception of the tunicate Salpa democratica, a primitive chordate³) whereas in invertebrate photoreceptors^4–8 it rises. The hypothesis that a light-induced isomerization of the photopigment chromophore, for example, retinal, is the primary event underlying the electrical response has been widely accepted, but the transduction mechanism connecting the change in conductance with the light-induced change in the photopigment remains to be elucidated.