Erection secrets

2002-03-19 13:04

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 discovered.

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