M. Carter Cornwall

TL;DR: There is increasing evidence that the second messenger responsible for the modulation of the transduction cascade during background adaptation is primarily, if not exclusively, Ca(2+), whose intracellular free concentration is decreased by illumination.

TL;DR: It is found that the Müller cells in the salamander neural retina promote cone-specific pigment regeneration and dark adaptation that are independent of the pigment epithelium.

TL;DR: Results from immunohistochemistry, spectrophotometry, and single-cell RT-PCR demonstrate that, in the tiger salamander, the green rods and blue-sensitive cones contain the same opsin, suggesting that neither the cell topology or the transducin is sufficient to differentiate the rod and the cone response.

TL;DR: Evidence is presented that in solitary cone photoreceptors isolated from the salamander retina, the latter effect is due to the presence of free opsin in the outer segment and this "opsin adaptation" can be reversed by treating the cells with synthetic retinoids similar to 11-cis retinal but having polyene chains too short to form protonated Schiff base attachments to opsin.

TL;DR: It is demonstrated that the formation of the covalent bond between opsin and 11-cis retinal is reversible in darkness in amphibian red cones, but essentially irreversible in red rods, contributing to the sensitivity difference between rods and cones.