Phototransduction and calcium.

In the early 1970s it became clear that an unknown intracellular messenger participated in signal transduction in retinal rod cells. Ca2+ and cGMP had been considered as candidates for such a messenger until 1985 when the cGMP-gated conductance of the plasma membrane was discovered. However, for the last several years, Ca2+ has taken revenge as a signal molecule which contributed to the processes underlying the photoreceptor cell recovery. This review describes the overall picture of phototransduction molecular mechanisms with special emphasis on participation of Ca2+ in visual cell signalling.