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 at Stanford University and Deltagen Inc. 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.

"This study clarifies the role of melanopsin in setting and maintaining the circadian clock," said Bruce O'Hara, senior research scientist at Stanford and co-author of the study published in the Dec. 13 issue of the journal Science.

O'Hara noted that without a circadian clock many behavioral and physiological traits of mammals would be disturbed - including body temperature, activity levels and sleep.

"Instead of being able to sleep for extended periods of time, we would be at the mercy of unpredictable bursts of sleep and activity," added Stanford senior research scientist Norman Ruby, lead author of the study.

Photoreceptors

For a circadian clock to function, it must be able to detect and respond to light. In mammals, the only cells specialized to do this are in the eyes, which means that our eyes not only allow us to see the world but also synchronize our body's internal rhythms.

Photoreceptors are specialized cells that can detect light and send signals to the brain, which then processes and interprets the information - allowing us to see. Rods and cones, which are located in the retina, are the primary photoreceptors for vision. Researchers first thought that these molecules had dual roles in vision and setting t
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Contact: Mark Shwartz
mshwartz@stanford.edu
650-723-9296
Stanford University
12-Dec-2002

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