updated 9/6/2005 9:07:12 AM ET 2005-09-06T13:07:12

Drug companies make $2.5 billion a year selling Viagra, Cialis and Levitra to help men enjoy sex. Since more women suffer from sexual dysfunction than men, developing a drug that could double those sales would seem to be a no-brainer.

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Yet the pharmaceutical industry has failed women miserably — there isn’t a single sexual dysfunction drug on the market that can help them. Pfizer Inc. last year abandoned an eight-year Viagra study involving 3,000 women, conceding that its famous blue pill only works for men.

“I hate to say it, but women are much more complex than men,” said Beverly Whipple, the sex researcher who co-wrote “The G-Spot.”

Viagra and its two competitors are rather blunt instruments — they work simply, by increasing blood flow down below. Women who take the drugs tend to experience the same physical effect, but this alone rarely satisfies them.

“You are not going to make a product by looking at what works in men and apply it to women,” said Amy Allina, program director at the National Women’s Health Network in Washington D.C. “That does reflect, in part, a lack of knowledge of what is underlying women’s sexual problems.”

Neurological solution needed
The latest research — being done by academics, rather than commercial drug companies — suggests a neurological solution is needed. Because when it comes to achieving orgasms, women are more affected by mood, self-esteem and other issues of the psyche than men.

While Pfizer and other pharmaceutical titans have abandoned the pursuit of a Viagra for females as too complicated, a growing number of university researchers are reporting progress with the help of brain scanners and other technology.

Yes, they’re watching women’s brains while they have orgasms. And they’re coming to some interesting conclusions.

For example, by studying paralyzed women who can still experience orgasm, they discovered that for women, the vagus nerve appears to be quite important, and therefore may be a promising target for drugs. This nerve — which is outside the spinal cord — carries information to areas of the brain that control mood.

“We basically found the areas of the brains that are activated in orgasm in women,” said Barry Komisaruk, who worked with Whipple on this research, which is being funded by the federal government and the Christopher Reeve Paralysis Foundation.

Brain scans measure the blood flow of research volunteers, whose heads are strapped tightly down inside the noisy machines. When brain cells start firing in a part of the brain that governs a particular emotion or activity, they need more oxygen, which is carried by the blood. During a brain scan, active regions of the brain can be seen lighting up on a computer monitor.

Pain centers shut down
The scans reveal something else about women — during orgasms, the pain centers in their brains shut down, and pleasure centers — the same ones that become active when people ingest cocaine — light up.

But a big problem with these scans — done through magnetic resonance imaging — is that no machine yet built is designed to simultaneously monitor both the brain and the body. And even if they could, the images’ clarity would be muddied by “background noise” such as hand movements.

That’s why Komisaruk is currently studying the brains of women who can self-stimulate purely through thought — an apparently rare attribute that eliminates the noise — as he seeks to find out exactly what makes women tick during sex.

“The strange thing is that everyone knows that it all happens between the ears and not between the legs,” said Gert Holstege, a leading sexual researcher at Groningen University in The Netherlands.

In June, Holstege published one of the first studies that mapped brain activity during orgasm for men and women, who were stimulated by their partners.

Among other results, Holstege found that the part of the brain thought to control fear and anxiety — the amygdala — deactivated during orgasm for both women and men.

He acknowledged that his data for men is a little suspect — however — because they don’t orgasm long enough to take a proper brain scan.

New drugs are years away
Brain scanning technology has been available for close to 20 years, but is only now being used to study sex. Researchers attribute the delay to several factors, including managerial skepticism and government reluctance to fund much of the work.

“In the United States people are little more reserved when it comes to sex than in the Netherlands,” said Holstege. He said that his U.S. colleagues told him they’d be afraid to propose such a project to their own bosses.

Sex research using brain scans is only just getting started, and scientists warn that any potential new drugs — or even better diagnoses of sexual dysfunction — are years away.

Still, many researchers — including those at the Kinsey Institute for Research, Sex, Gender and Reproduction at Indiana University — see brain scans as an important tool.

“We tried to come to conclusions about the brain through all kinds of detours,” said Erick Janssen, a Kinsey researcher. “This is a much more direct way to do it.”

© 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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