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Scientists Discover “Reset” Button for Circadian Rhythm

Could a simple reboot turn exhaustion into a thing of the past?

Being able to control "clock neurons" could help with combatting jet lag and fatigue. (Corbis)
smithsonian.com

Our circadian rhythms rule our lives, regulate our sleep and tell us when to get up in the morning. But though scientists know how critical our internal clocks are to health and human performance, they haven’t been able to predictably control them.

That could be about to change. At Vanderbilt University, biologists have figured out how to stimulate and manipulate the neurons that control the circadian rhythms of mice. The rodents may be nocturnal, but otherwise their biological clocks are nearly identical to those of humans. 

The study hinges on a part of the brain called the suprachiasmatic nucleus (SCN), home to the body’s master clock. Scientists used to think that more activity in the SCN meant that they'd see more neurons firing—that the firing rate of neurons was an output of the clock's natural activity. But the research team from Vanderbilt learned that they had it all backwards, when they inserted genes into the neurons of mice to make those cells respond to light. 

In the experiment, one group of mice had neurons that would fire more often when exposed to light; another had neurons that would fire more often when light was suppressed. That meant the researchers were able to control the neurons' firing rate, and they were able to show that by manipulating the firing rate, they could actually stimulate the SCN. "This suggests that SCN firing rate is fundamental to circadian pacemaking as both an input to and output of the molecular clockworks," they write in their paper. In other words, triggering or suppressing the right neurons effectively reset the SCN, rebooting the biological clock.

“This puts clock neurons under our control for the first time,” said Jeff Jones, a doctoral student who co-conducted the study, in a release. The team hopes that this strategy—causing cells to respond to light—could be the key to a cure for jet lag, seasonal affective disorder or the clock confusion caused by shift work. 

Given last week’s announcement that a new pill could help fool the body into thinking it’s a different time of day, it could be a mere matter of time until a genetic modification or a prescription helps us feel less sleepy. But hold on to your coffee cup—it could be years before optogenetics hit the medical mainstream.

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