Jet lag: It can strike even professional athletes. For the haggard traveler, remedies abound, from wearing sunglasses indoors to getting afternoon sun to drinking plenty of water to popping melatonin. The fundamental problem, of course, is that flying across time zones can wrench your body's physiological rhythms out of sync. There's hope that we can hack those rhythms, and a new discovery suggests the eyes may offer another way to do it.
Researchers from the University of Edinburgh recently found a group of cells in the retina—the light-sensitive layer at the back of your eyeball, home to the rods and cones—that send signals to the part of the brain that governs our daily sleep-wake cycles. Those cycles, known as circadian rhythms, are synced to changes in light and darkness and they're well-studied, leading scientists to suggest that school should start later because teens need more sleep, for example.
We've long known that disrupting those cycles doesn't just make you groggy. Our biological clocks help regulate body temperature, brain activity, and hormone production and, in the long term, disruptions can lead to a host of health problems, including heart disorders and gastrointestinal issues, the authors say. People working against their circadian rhythms (like night-shift workers) may develop depression and face an increased cancer risk.
The region of the brain that coordinates these rhythms is called the suprachiasmatic nucleus (SCN) and while researchers knew that the retina signals changes in environmental light to the SCN—which is why seeing more sunlight can affect your internal clock—they didn't understand exactly how that worked.
One of the molecules the SCN uses to do its job is vasopressin, a hormone produced by nerve cells, and this study found for the first time that the retina has its own group of nerve cells that make vasopressin when exposed to light and these cells communicate directly with the SCN. The researchers made this discovery in rats by interfering with the way information about light was signalled to their SCN. They found that the retinal cells that make vasopressin are directly involved in regulating circadian rhythm.
Knowing where those cells are and how they work offers new insight into the biological clock and it also suggests ways to fix messed-up circadian rhythms through the eye—imagine an eye drop that cures jet lag.
Vasopressin-altering eye drops are a possibility, but they're a long, long way off. For now, though, think of it as a hopeful bit of good news to share with your fellow passengers next time you're suffering through an ill-advised red-eye flight.
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