Cells in the eye are key to regulating humans’ circadian rhythm, according to a scientific study. Researchers at the University of Edinburgh found that a group of cells in the retina communicate directly with the region of the brain that deals with the body’s internal clock.
All life forms respond to the daily light-dark changes of day to night, and these circadian rhythms are generated by an internal biological clock. This “clock” is controlled by neurons in one particular area of the brain, the suprachiasmatic nucleus (SCN).
The SCN is influenced by environmental signals, including information on light received by the retina, which is passed along nerve fibres. The study demonstrated that the retina contains vasopressin-expressing cells, which communicate exclusively with the SCN and have nothing to do with normal vision. Vasopressin is a critical element in re-setting the body’s internal clock, for example after travelling long haul across time zones or working night shifts.
The study involved testing on lab rats to see the effects of selectively destroying or activating the vasopressin-expressing cells in the retina.
On a practical level, the study aimed to provide a deeper understanding of the biological clock to begin to address the health problems that accompany rotational shift work – including increased propensity for cancer, depression, sleep disturbances, gastrointestinal, metabolic and cardiovascular disorders, decreased immune responses and even decreased life span.
However, on a more recreational level, the results could be the key to developing a drug to reduce the symptoms of jet lag.
“Our exciting results show a potentially new pharmacological route to manipulate our internal biological clocks,” said Mike Ludwig, professor of neurophysiology at yhe University of Edinburgh.
“Studies in the future which alter vasopressin signaling through the eye could lead to developing eye drops to get rid of jet lag; but we are still a long way off from this.”