Viagra, commonly given to treat impotence, may one day help shift workers and flight crews recover their normal sleep cycles
Credit: stock.xchng.hu
SYDNEY: A shot of Viagra may one day help shift workers and flight crews recover their normal sleep cycles, a new study on hamsters suggests.
In a paper published in the U.S. journal Proceedings of the National Academy of Sciences, Diego Golombek from Argentina's National University of Quilmes and colleagues found that administering a hamster-sized dose of Sildenafil – more commonly known as Viagra – helped the rodents recover more quickly from laboratory-induced jet lag.
"Taking into account that jet lag is increasingly common and has profound effects on quality of life, I believe this research is particularly relevant," said Golombek. "It opens a completely original way of dealing with [jet lag]."
Winding the body clock
The body's 24 hour sleep-wake cycle is closely linked to the onset and departure of sunlight. We can bring the body clock forward by waking up early, or set it back by staying up late. When we cross many time zones rapidly, our bodies don't have time to adjust, and the result is jet lag.
Golombek and his team simulated jet lag in hamsters by switching a light on in their cages at odd hours. They wanted to see what would happen when they intervened in a key biochemical pathway involved in setting the body clock in the brain – that of cyclic guanosine monophosphate (cGMP).
"There are two ways of manipulating cGMP levels: by increasing its synthesis rate or by inhibiting its degradation," Golombek said. Enter Viagra.
The "little blue pill" commonly given to treat impotence works by preventing the breakdown of cGMP, not in the brain but in the penis, where doing so promotes blood flow and erection. "When we thought about using sildenafil – and it finally worked! – it was certainly a little eureka moment," Golombek said.
Flying hamster class
The researchers injected hamsters with Viagra at night, then turned on bright lights in their cages six hours earlier than usual. This had the effect of bringing their little hamster body clocks forward by six hours, a bit like flying from London to New York.
They then assessed the hamsters' recovery by measuring how quickly they hopped back onto their exercise wheels. Hamsters who had been injected with Viagra recovered 25 to 50 per cent earlier than other animals. The researchers believe Viagra increased the animals' sensitivity to light, allowing them to readjust more quickly.
Interestingly, the drug only worked when applied before an advance in the light/dark cycle, equivalent to an eastbound flight, rather than the reverse. "There is evidence that the molecular pathway for [body clock] delays or advances is different," Golombek said.
According to the researchers, clinical trials in human subjects could begin relatively quickly given the extensive testing Viagra has already undergone. But as Martha Merrow from the University of Groningen in the Netherlands points out, they may be underestimating the potential market for anti-jet lag drugs.
"Many of us are living against our clock, performing at times when our performance is sub-optimal," she said. Merrow calls this phenomenon 'social jet lag', attributing it to our disconnection from natural daylight hours and the predominance of artifical light.
