Rod photoreceptors
From The School of Biomedical Sciences Wiki
Rods are photoreceptors found in the retinas of vertebrates and are involved in non colour vision. Rods are highly specialised cells and permit vision in low light via the transduction light signals into chemical signals which van be sent to the brain. Rods produce a response by utilising G-proteins and the secondary messenger cyclic GMP.
Alberts et al, Molecular Biology of the Cell, Fifth Edition, Garland Science, 917-918.