Sexy Scent Real Turn-On For Sperm Research May Yield Male Contraceptive

The molecules the nose uses to pick up the scent of cologne have also been found on sperm, suggesting a microscopic courtship takes place in which sperm make their way by following the sweet perfume of human eggs.

The startling discovery suggests that a drug that blocks the sperm’s ability to sense that enticing aroma could be used as a male contraceptive, said Dr. Robert J. Lefkowitz of Duke University.

“Such a drug could be the ideal contraceptive,” Lefkowitz said. It would be likely to have few side effects, because the smell receptors on which it would act exist nowhere else in the body except on sperm and in the nose, he said.

In a presentation Tuesday at the New Horizons in Science briefing at Duke University, he mentioned the discovery of the sperm’s smell receptors as one example of how basic research on receptors and their signaling systems can lead to unexpected practical applications.

Lefkowitz has spent decades studying cell receptors and the signaling molecules called G proteins that carry information inside cells. When he began the work, he had only faith to go on that something useful would eventually come of it, he said.

Dr. Gabriele Ronnett and Loren Walensky of Johns Hopkins University collaborated with Lefkowitz on the sperm research.

Before they began, it was known that fish sperm, for example, must have some way to find eggs. “They definitely need a way of sensing, by chemicals, how they know where to go. They eject their sperm in billions of gallons of sea water,” Ronnett said.

The situation with mammals was unknown, but Ronnett decided to look. She first found the receptors on the sperm of laboratory rats. Then she looked at human tissue, where she found similar smell receptors.

“They’re there to smell the egg,” Lefkowitz said. “I guess that’s the going hypothesis.”

To make a contraceptive, “the idea would be to develop a drug which binds to those receptors,” Lefkowitz said. The class of drugs called beta blockers - among the most widely used treatments for heart disease - work exactly that way: They block receptors in the heart muscle, Lefkowitz said.