Researchers Identify Key Pathway in the Pupil’s Response to Light

Medical investigators have demonstrated that a particular protein is important for the eye’s pupil to respond to light. The discovery may help scientists learn more about the eye’s role in non-visual functions such as the synchronization of the body’s internal, circadian clock. Reporting in the Jan. 10 issue of the journal Science, the researchers say that mice that lack the two main types of photoreceptor cells in the retina ? rods and cones ? as well as proteins in the retina called cryptochromes, lose about 99 percent of their sensitivity to light.

Scientists shed new light on the body’s internal clock

As mammals, our internal (circadian) clock is regulated by the patterns of light and dark we experience. But how that information is transmitted from the eye to the biological clock in the brain has been a matter of scientific debate. Scientists had suspected that a molecule called melanopsin, which is found in the retina, plays an important role. Now researchers have confirmed that melanopsin does indeed transmit light information from the eye to the part of the brain that controls the internal clock. According to the researchers, melanopsin may be one of several photosensitive receptors that work redundantly to regulate the circadian system.