PHEROMONES – Scientific Research

Since the 20th-century hygiene revolution and the rise of the personal-care industry, however, companies have pitched deodorants, perfumes, and colognes to consumers as the epitome of sex appeal. But instead of furthering our quest to find the perfect mate, such products may actually derail it, say researchers, by masking our true scent and making it difficult for prospects to assess compatibility. "Humans abuse body smell signals by hiding them, masking them, putting on deodorant," says Devendra Singh, a psychologist at the University of Texas. "The noise-to-signal ratio was much better in primitive society." Miller argues that modern hygiene may be such an impediment to sexual signaling that it could explain why so many people in our culture get so physical so fast. "Hunter-gatherers didn't have to do a lot of kissing, because they could smell each other pretty clearly from a few feet away," Miller says. "With all the showering, scents, and soap, we have to get our noses and mouths really up close to people to get a good idea of their biochemistry. People are more motivated to do a lot more kissing and petting, to do that assessment before they have sex." In other words, the need to smell our mates—and the comparative difficulty of doing so in today's environment of perfumes and colognes—may actually be driving the sexual disinhibition of modern society.

All it takes is a few molecules of a certain chemical to enable mammals to smell their own species up to a half-mile away, says Milos Novotny, Distinguished Professor of chemistry and director of the Institute for Pheromone Research.

The chemicals, called pheromones, are detected by the vomeronasal organ (VNO) in the animal's nose. Unlike the part of the nose that detects ordinary smells, this super-sensitive organ is connected directly to the mid-brain.

Professor Novotny current emphasis is on the neurochemistry of neurons in the VNO and OE. He is the leader of interdisciplinary studies that bridge the physical sciences, life sciences and social sciences, including chemistry, neurobiology, psychobiology, biochemistry, wildlife ecology, medical sciences, and animal physiology and behavior.

Ever notice how male dogs come from the other side of the neighborhood when a female dog is in heat?

In a paper published July 12 in the journal Nature, Novotny and co-workers at Harvard Medical School in Boston headed by Linda Buck reported that the vomeronasal organ can actually detect both odorants and pheromones. The VNO detected odorants classified as animalic, camphoraceous, citrus, floral, fruity, green/minty, musky, sweet or woody. Like pheromones, these odorants were detected at extremely small concentrations.

"This suggests that in mammals, as in insects, odorous compounds released from plants or other animal species may act as 'semiochemicals' -- signaling molecules that elicit behaviors that are advantageous to the sender or the receiver," Novotny said.

Compared with many other creatures, human women and men simply don't rely too heavily on their noses for sniffing out a  partner. But new studies suggest that our sense of smell may be more important than was previously assumed. In fact, says Alan Hirsch, neurological director at the Smell & Taste Treatment Research Foundation in Chicago, people can lose sexual function if they lose their sense of smell.

Some researchers think olfactory research in animals may help explain human behaviors. Let's start with mice. Claus Wedekind, a zoologist at Bern University in Switzerland, says female mice sniff for mating partners with DNA that's different from their own, to help their offspring resist a wider range ofdiseases. Specifically, Wedekind says, female mice look for a mate with a different MHC (major histocompatibility complex), a protein complex that lets the immune system know when disease is
present, spurring killer T cells into action. Similarly, researchers say, human females are more likely to be attracted by a man's body odor if he has different MHC.

Even if a woman turns up her nose at first, researchers have learned, a relationship may flower later, when her body is more receptive. In studies at the Ludwig-Bolzman-Institut in Vienna, 290 young women who were ordinarily turned off by androsterone (a key component in men's sweat) were less so by it while they were ovulating. Androsterone, it seems, may act as a pheromone that attracts women, increasing the likelihood of fertilization

Scientists at the University of Pennsylvania and the Monell Chemical Senses Center in Philadelphia have found that exposure to male perspiration has marked psychological and physiological effects on women: It can brighten women's moods, reducing tension and increasing relaxation, and also has a direct effect
on the release of luteinizing hormone, which affects the length and timing of the menstrual cycle.

The results will be published in June in the journal Biology of Reproduction and currently appears on the journal's Web site.

"It has long been recognized that female pheromones can affect the menstrual cycles of other women," said George Preti, a member of the Monell Center and adjunct professor of dermatology in Penn's School of Medicine. "These findings are the first to document mood and neuroendocrine effects of male pheromones on females."

In a study led by Preti and colleague Charles J. Wysocki, extracts from the underarms of male volunteers were applied to the upper lip of 18 women ages 25 to 45. During the six hours of exposure to the compound, the women were asked to rate their mood using a fixed scale.

"Much to our surprise, the women reported feeling less tense and more relaxed during exposure to the male extract," said Wysocki, a member of the Monell Center and adjunct professor of animal biology in Penn's School of Veterinary Medicine. "This suggests that there may be much more going on in social settings like singles bars than meets the eye."

After the women's exposure to the underarm extract, further testing revealed a shift in blood levels of luteinizing hormone. Levels of this reproductive hormone, produced in pulses by the pituitary gland, typically surge right before ovulation but also experience hundreds of smaller peaks throughout the menstrual cycle.

Preti and Wysocki found that application of male underarm secretions hastened onset of these smaller pulses. Duration to the next pulse of luteinizing hormone was shortened by an average 20 percent, from 59 to 47 minutes.

Preti and Wysocki are now looking at the several dozen individual compounds that make up male perspiration to determine which may be responsible for the effects they observed. They also plan to study whether female pheromones can affect men's moods or physiological functions.

"This may open the door to pharmacological approaches to manage onset of ovulation or the effects of premenstrual syndrome or even natural products to aid relaxation," Wysocki said. "By determining how
pheromones impact mood and endocrine response, we might be able to build a better male odor: molecules that more effectively manipulate the effects we observed."

The underarm extracts used in the study came from men who bathed with fragrance-free soap and refrained from deodorant use for four weeks. The extracts were blended to avoid reactions to individual men's odors. None of the women involved in the study discerned that male sweat had been applied right under their noses; some believed they were involved in a study of alcohol, perfume or even lemon floor wax.

Half the women received three applications of the male secretions during a six-hour period, followed three controlled exposures to ethanol, used as control substance, over a six-hour period. For the other half, the regimen was reversed. The women did not report feeling any more orless energetic, sensuous, tired, calm, sexy, anxious, fatigued or active after exposure to male perspiration.

Research on human putative pheromones has recently focused on the effects of exposure to 4,16-androstadien-3-one (androstadienone). This steroid has been observed in the skin, axillary hair,
and blood plasma, primarily in males. In addition to effects of the steroid on measures of physiological
arousal and brain blood flow, positive mood effects have also been reported. The current study further
investigated mood effects of androstadienone exposure (250 M) in women in two experiments.
Through psychophysical testing of each individual we controlled for whether any observed mood
effects could be related to sensory detection of the steroid. In both experiments, we observed positive
changes of women's feeling of being focused, which could not be related to sensory detection of
the steroid. Overall, the patterns of results were significantly correlated between the two experiments. In conclusion, this study corroborates earlier findings suggesting that androstadienone exposure yields effects on women's mood; the feeling of being focused. The mood effects were not dependent on menstrual cycle phase. Further, these effects are replicable and occur also when androstadienone detection is rigorously controlled for across variation in menstrual cycle.

We examined the physiological and psychological effects of nanomolar amounts of steroids applied directly under the nose (Delta4,16-androstadien-3-one and 1,3,5,(10),16-estratetraen-3-ol). These potential human chemosignals were not consciously discernible in a strong-odor carrier (clove oil and propylene glycol). In a double-blind, within-subject, repeated-measures experiment with 65 subjects,
we demonstrated that both steroids produced sustained changes in digit skin temperature and palmar skin conductance (an indicator of sympathetic nervous system tone) while the subjects were completing psychological questionnaires or reading. These effects, however, did not follow the sex-stereotyped pattern predicted by a sex attractant function. Both androstadienone and estratetraenol raised the skin temperature of men's hands and lowered it in women. Likewise, each steroid increased skin conductance, with a significantly greater effect on women than men. Women's responses were observed only in the sessions run by the male tester, an effect that may or may not be solely attributable to tester sex. Men's responses, in contrast, were not affected by this difference in socioexperimental condition.

Similarly, women experienced an immediate increase in positive mood only in the presence of the male tester, while men's responses were unaffected by this socioexperimental context. One source of this sex difference may be the fact that the majority of women were in the late follicular phase of their menstrual cycle. Although it is premature to classify these steroids as pheromones, our data suggest that they function as chemosignals that modulate autonomic nervous system tone as well as psychological state.

For laboratory certified human pheromone products see …

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