December 10, 2015

Flickering candles, rose petals, smooth music, and… nothing? Many women who are premenopausal experience  inhibited sexual desire, or hypoactive sexual desire disorder, making physical intimacy seemingly impossible – and scientists are unclear as to why. As the drug touted as “the female Viagra” hit the market, researchers at the Wisconsin National Primate Research Center studied more about how the drug, called flibanserin, actually works, which may also lead to ways to improve its safety.

Dr. David Abbott, a professor of obstetrics and gynecology in the University of Wisconsin School of Medicine and Public Health, and Dr. Alexander Converse, associate scientist at UW–Madison’s Waisman Center, studied the effects of flibanserin in the common marmoset. Similar to humans, marmosets rely on pair bonding for mating success and family life. They also exhibit similar hormonal signaling activity and mating behaviors, especially in response to sexual cues such as touch and scent, providing an unparalleled model of the primate brain.

Scientists are especially interested in better understanding flibanserin due to its adverse side effects. These can be serious and include severely low blood pressure and potential loss of consciousness. In addition, alcohol consumption, certain medicines and liver impairment can exacerbate the risks.

To explore flibanserin’s effect on the brain, Abbott and Converse compared flibanserin-treated monkeys to untreated monkeys using noninvasive PET scanning on live common marmosets at the Wisconsin National Primate Research Center. After mapping the animals’ brains with MRI scans, Converse used PET imaging to correlate changes in brain chemistry, particularly the use of glucose at specific locations with flibanserin-induced behavioral changes. Together with colleague Yves Aubert, Converse and Abbott found glucose metabolism declined in the brain center linked to intimate grooming and solicitation of sex.

Study results link flibanserin-initiated decreases in female metabolism to increased pair bonding, meaning the bigger the metabolic dip in brain activity, the more grooming. Although both males and females in the study initiated more grooming, the behavior was more pronounced in the males, even though only females received the drug.

Although the female marmosets did not have hypoactive sexual desire disorder, the study nonetheless shows that flibanserin, by altering metabolic brain activity, prompts increased female behavior responses to grooming, a form of intimate, gentle touching from males. That, said Abbott, “offers the first insight into how the drug may be working in the brains of women.”

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