Body clock 'reset button' found
Drugs that rapidly tweak the body clock in order to avoid jet lag and the pains of shift work have moved a step closer after research in Japan.
The team at Kyoto University has found the clock's 'reset button' inside the brain.
Their study, published in the journal Science, showed the button could be used to switch the clock to a new time zone in a single day.
Experts said the team was "close to the money" in the hunt for a jet lag cure.
There are clocks throughout the body and a "master clock" in the brain, keeping the body in sync with the world around it to make people sleepy at night.
Anyone who has ever done shift work or a long-haul flight has experienced the disrupted sleep and hunger patterns of a body clock which is out of tune with the rising and setting of the sun.
The clock uses light to help keep track of time, but it is naturally stubborn and adjusts slowly.
The rough rule is that for every time zone crossed it takes a full day for the body to catch up. Fly from London to Beijing and it would take a week for the body clock to fully adapt.
The team in Japan have come up with a way to get the master clock to be a bit more flexible.
It is a group of 10,000 brain cells - about the same size as a grain of rice - which constantly talk to each other to keep a strict control over the time.
The scientists found that interfering with the vasopressin receptors, essentially a brain cell's ears that allow it to keep in touch with its neighbours, let the clock shift rapidly.
Genetically modified mice which had no vasopressin receptors were able to adjust to the clocks being put back eight hours within a single day, while normal mice took six days.
When the clocks were put forward eight hours then it took normal mice eight days to adapt, but those without vasopressin receptors adjusted in two.
Similar results were then achieved in normal mice using a drug.
The study's authors concluded: "Studies have shown that chronic jet lag and rotating shift work can increase an individual's risk of developing hypertension, obesity, and other metabolic disorders.
"Our results identify vasopressin signalling as a possible therapeutic target for the management of circadian rhythm [body clock] misalignment."
Dr Michael Hastings, a Medical Research Council body clock researcher, told the BBC's Science in Action programme: "It's a remarkable study, it really is very exciting for our field.
"There's been many false dawns when it comes to a cure for jet lag, but I think this time they're close to the money."
However, he cautioned that vasopressin receptors were also heavily involved in kidney function so any drug developed would need to be designed carefully to target the body clock without disrupting the kidneys.
Dr Hastings added that with an increasingly 24-7 society a drug which can adjust the body clock could, in theory, improve the health of shift workers.
"The issue here in terms of public health is rotational shift work, the epidemiological evidence that we have now shows that if a worker has spent a working life doing rotational shift work they're at higher risk of contracting certain forms of cancer, cardiovascular disease or metabolic syndrome like diabetes."