http://news.bbc.co.uk/2/hi/health/6676585.stm
Viagra could be used to help people flying eastwards recover from
jetlag, animal research suggests.
A team of Argentine scientists found the drug helped hamsters recover
up to 50% faster from forward shifts in their daily time cycles.
However, the drug only worked in conjunction with light therapy, and
only in one time direction - the equivalent to flying eastbound.
The study features in Proceedings of the National Academy of Sciences.
In mammals, the light-dark cycle regulates the body's biological
clock, which promotes activity during the daytime, when it is light,
and sleep at night.
Time shift
The researchers from the National University of Quilmes shifted the
light-dark cycle of hamsters six hours forwards, by switching on
lights six hours earlier than usual.
They then monitored the hamsters' running wheel activity to assess
when their body clocks had adjusted to the new time cycle - the
hamsters are active in the day but stop running when the lights go out.
Injection of Viagra before the time shift meant the hamsters adjusted
to the new time cycle faster, even when low doses of the drug, which
did not cause penile erections, were used.
Viagra, the drug sildenafil, was originally developed for the
treatment of high blood pressure and angina, and is used to treat
erectile dysfunction.
When used without the shifts in light, the drug did not induce
changes in the hamsters' activity, so it seems to work by enhancing
the light-induced response.
Dr Diego Golumbek, who led the research, said the drug seemed to work
via a molecule called cGMP which is known to have a role in setting
the body's time clock - it is present at higher levels during the day.
The Viagra blocks the activity of an enzyme which breaks down cGMP,
allowing higher levels to build up.
One direction only
Dr Golumbek said the fact that different mechanisms may be used to
slow down and speed up the body clock explains why Viagra only worked
when the lights were switched on early, not late.
Professor Robert Lucas said although looking for ways adjust
biological clocks was important, regulating light exposure was the
most widely accepted strategy for doing this.
He said the new research raised the possibility of using Viagra in
conjunction with this light treatment, but he added: "We will have to
wait for more research to know whether this will work in humans."
Pfizer, the makers of Viagra, said the drug should only be used in
accordance with the approved labelling.
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((Udhay Shankar N)) ((udhay @ pobox.com)) ((www.digeratus.com))
