Doctor Ravi Allada, an Indian-American circadian rhythms expert at Northwestern University in Illinois has identified how an animal's biological clock wakes it up in the morning and puts it to sleep at night.
The clock's mechanism, it turns out, is much like a light switch.
At night, high potassium channel activity turn them off, allowing the animal to sleep.
Investigating further, Allada was surprised to discover the same sleep-wake switch in both flies and mice.
"This suggests the underlying mechanism controlling our sleep-wake cycle is ancient," Allada said.
This oscillation mechanism appears to be conserved across several hundred million years of evolution.
"And if it is in the mouse, it is likely in humans, too," he noted.
Better understanding of this mechanism could lead to new drug targets to address sleep-wake trouble related to jet lag, shift work and other clock-induced problems.
Eventually, it might be possible to reset a person's internal clock to suit his or her situation.
The researchers call this a "bicycle" mechanism: two pedals that go up and down across a 24-hour day, conveying important time information to the neurons.
The researchers found the two pedals -- a sodium current and potassium currents -- active in both the simple fruit fly and the more complex mouse was unexpected.
The balance between sodium and potassium currents controls the animal's circadian rhythms.
"Our starting point for this research was mutant flies missing a sodium channel who walked in a halting manner and had poor circadian rhythms," Allada noted.
"Now, of course, we have more questions about what's regulating this sleep-wake pathway, so there is more work to be done," he concluded.
The findings were published in the journal, Cell