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---------------------------------------------------------------------------- Analyzing the sweet smell of romance ---------------------------------------------------------------------------- (September 15, 1997 11:33 a.m. EDT) -- Having no luck pursuing the object of your desire? It could be time to ditch the etiquette manual. The key to success might be in swapping expensive aftershave for good old body odour. It might sound dubious but just think of the results. In an ideal world, those animal smells would send a subliminal sexual signal capable of inspiring great passion. Then again, he or she might never want to come within three feet of you again. Scientists have not been able to agree whether human beings have the right olfactory equipment to pick up on the scent of lust. However, the dispute is set to intensify with the news this month that researchers have discovered a new system of smell in rats and mice. The system refines their ability to detect pheromones, chemical signals related to sexual behavior. Such signals are known to exist in the animal world; they trigger the urge to mate, among other things. Despite scant, if any, scientific evidence, some people believe that humans exchange similar subliminal chemical signals. The latest discovery bestows upon the rat a third system of smell. The animal sniffs out everyday odours, such as food, using receptors on the nasal membrane which link up, via nerve fibers, to the olfactory bulb. Human beings employ an identical technique of identifying ordinary aromas. The rodent, however, goes one better. It possesses a distinct structure responsible for detecting pheromones. Scientists were astonished to find that this structure, called the vomeronasal organ (VNO), boasts its own complement of odour receptors, determined by a separate family of genes. The nerve fibers from these pheromone receptors trace back to a special part of the olfactory bulb known as the accessory olfactory bulb. The latest twist, reported in the current issue of Cell, is that the VNO in rats and mice has a second set of odour receptors, associated with yet another set of genes. Dr. Linda Buck, from Harvard Medical School, made the discovery in rats; Dr. Catherine Dulac, from Harvard University, reported her results in mice independently. Why the VNO in these animals should have two autonomous detection systems is a mystery. One suggestion is that each system is tuned to pheromones performing different roles, such as reproduction and social status. Another idea is that the various sets of receptors lock onto different portions of an odour molecule. The brain processes each portion and reassembles it into an identifiable smell. What does this have to do with us? Because mice, rats and humans share a substantial genetic heritage, gene families in these small mammals are often mirrored by groups of genes in human beings. Supporters of pheromone research are likely to claim that, somewhere in their genetic make-up, people do indeed possess a "sixth sense" of smell that governs relationships with the opposite sex. In fact, there is evidence that we have one of these special organs up our noses. "We have known over the past 300 years that the VNO develops in embryos but it was always reported to disappear," Professor Michael Meredith, a VNO expert from Florida State University, says. "Then researchers looked in a different place in adults and found it again. It isn't like the VNO organ in any other animal, but there is something there." The pertinent question, Professor Meredith says, is whether the organ is actively connected to the brain. "We know from studying corpses that there are nerve bundles from the VNO to the brain but we have no proof they were active." The waters are muddied by beliefs that the nerves link up only to the lower brain, and bypass the cerebral cortex, the seat of human experience. "It conveniently means we cannot obtain proof through personal experience." If anything, Meredith believes the new research destabilises the theory that human beings can detect pheromones. This is because the receptor proteins generated by these brand new genes are flawed. Dulac, who has found some matching human genes, therefore thinks that these faults will appear in the human proteins, too. In other words, even if we choose to believe we send out chemical signals to each other, our pheromone antennae are genetically switched off. This view will not be universally popular. Scientists such as Dr. Clive Jennings-White, from the multimillion-dollar Pherin Corporation, thrive on the assumption that human beings can pick up each other's scent. The research organisation, whose laboratories are at the University of Utah, earns its keep through selling bottled human pheromones through a company called Erox. Both Pherin and Erox were set up by Dr. David Berliner, a Professor of Anatomy at the university. Pherin holds a patent on the use of human pheromones in fragrances, and is planning to bring its concoctions, Realm Man and Realm Woman, to Britain soon. Jennings-White, an organic chemist at Pherin, says the evidence for human sensitivity to pheromones goes back to the early seventies with the finding that women in regular contact develop menstrual synchrony. "That is assumed to be a pheromone-based communication," says Jennings-White. "In living, breathing people, we can also deliver chemicals exclusively to the VNO and record a brain signal half a second later. The pheromones induce changes in skin temperature and conductance." He also cites psychological evidence; the preparations can, he says, relieve anxiety, promote well-being, induce hormonal changes and eventually be used to combat stress and premenstrual tension. Of the physical experiments, Professor Meredith says it is difficult to isolate completely the VNO from other organs, so the changes could have been accidentally induced. He doesn't hide his scepticism. "The human pheromone business runs on rumour and hope, not on fact. And now it looks like the issue is going to get interesting." By ANJANA AHUJA, The Times of London news service Copyright 1997 Nando.net Copyright 1997 Times of London <http://www.nando.net/newsroom/ntn/health/091597/health14_7446_noframes.html> ---------------------------------------------------------------------------- [log in to unmask]