Single K+ channels closed by light and opened by cyclic GMP in molluscan extra-ocular photoreceptor cells.

We report the first recordings of the light-sensitive channel which is active during dark and is closed by light in the Onchidium extra-ocular photoreceptor cells. This light-sensitive channel was K-selective and was not blocked by extracellular Ca2+ and Mg2+. Application of cyclic GMP to excised inside-out patches activated (opened) a channel that appeared to be the same as the light-sensitive channel recorded from the same membrane in the intact cell.