Synapse

The objective for this study is to understand the mechanism of non-visual reflexes such as regulation of the circadian clock and pupillary reflexes. The suprachiasmatic nucleus (SCN) is a site for photoentrainment in the brain. A portion of light-sensitive retinal ganglion cells protrude into the SCN. The authors hypothesized that melanopsin is a photopigment on the retinal ganglion cells (RPG’s) that generate action potentials to the brain in response to light, and play a role in photoentrainment. Although it was known that some RPG’s are photosensitive, the reasons for this phenomenon were unknown. It was also known that rods and cones are not photoentraining receptors. Provided this context, the reason for the study was to understand the function of RPG photosensitivity, and to use them to study the pathway that gives rise to photoentrainment.