Washington - US researchers can now describe how the male erection is maintained, based on studies of genetically modified rats and mice.
Researchers at Johns Hopkins University discovered ten years ago
that erection is caused when an erotic thought or physical
sensation triggers the release of nitric oxide from nerve endings
in the penis, stimulating blood flow and the swelling of tissues.
But that response lasts only a few seconds.
The secret to maintaining the erection is continued production
of nitric oxide by the blood vessels, the same scientists have
An article about their work is to appear on Tuesday in the
Proceedings of the National Academy of Sciences.
Like driving a car
"The physiology of erection is like driving a car. You can't just turn the key and expect to go anywhere. You also need to hit and hold the accelerator," said Arthur Burnett, an associate professor of urology at Johns Hopkins.
Burnett and his team, based in Baltimore, Maryland, discovered
that blood vessels take over for the nerves, releasing a continual supply of nitric oxide and thereby hardening and maintaining the erection.
"Once blood starts flowing into the penis, the source of nitric oxide in the blood vessels is continuously activated so that more nitric oxide is released, more tissue relaxes, more blood comes in and a sustained erection is achieved," Burnett said.
The flow of blood creates a minor stress on the blood vessel
wall, which activates the release of more nitric oxide from the
endothelial cells of the blood vessel wall.
The source of nitric oxide in the blood vessel is an enzyme
called endothelial nitric oxide synthase, which until now had been the missing piece of the puzzle, according to Burnett.
Scientists hope the discovery will open new avenues for the
treatment of erectile dysfunction. - Sapa-AFP