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Chemistry of Desire By Michael D Lemonick; Sonja Steptoe/Los Angeles time . , 19, 2004
i , afer she had a hysterectomy hysterectomy at age 42, Roslyn WashWashington was lef with an unexpected side eect. Her doctors, who had recommended removng her ovares as well as her uterus because o brod tumors and an ovaran cyst, had warned her about a lengthy recovery perod. But, she says, “I was not aware o the act that there would be a decrease in my sexual lie” Tat’s something o an understatement Washington, an oce manager rom Silver Spring, , who is married and has a teenage daughter, says that afer the surgery she elt no sexual desire whatsoever “I didn’t think about it,” she says. “I didn’t get that urge rom a glance or a look or a touch.” It was a proound loss. “Wthout that connecton, wthout the sexual aspects, you eel in some instances like you’re really less than a woman,” she says Ten several years later Washngton Washngton heard a rado ad seekng women lke l ke her or a study o testosterone patches. People usually thnk o testosterone as a male hormone, but women have plenty in their systems too, and researchers have reason to beleve bele ve that the hormone s nvolved nvolved n the emale sex drve. About hal o women’s testosterone s produced produce d n the ovares, so the patches were an attempt to replace what had been lost through surgery Washington signed up and was one o 75 women accepted or the study
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out o 50,000 who applied; clearly she was not alone in her misery wice a week or the next year she axed a thin, clear patch onto her abdomen, alternating sites over where her right and lef ovaries used to be Washington didn’t know whether she was receiving transdermal testosterone or a placebo. plac ebo. She dd d d know that thngs were very ver y derent. “I hadn’t hadn’t elt like that in years,” she says “I elt stimulated It was like, ‘Oh, yeah, I’d orgotten that’s what it eels like’ It was good” Alas, when the trial ended, her desire ebbed It’s tempting to conclude that Procter & Gamble, manuacturer o the testosterone patch, had ound the elusve chemcal key to emale desre. Te study, publshed n 2000 n the New England Journal o Medcne, reported that many o the women who, like Washington, were on real testosterone had more sexual antasies and more sex and masturbated more than they had beore But so, albeit to a lesser extent, did women who wore patches with no testosterone at all. For women suering rom lost libido, the placebo eect was almost as strong as that o the hormone In short, the mere belie that the treatment would rekindle sexual desire was ofen enough to turn up the heat Ts ndng llustrates the promse and the perplexty o research nto the bology bolog y o human sexualty, sexualty, where mnd, body and experence are endlessly ntermngled. People nd themselves turned on n obvous stuatons—slowdancng together, seeng someone wth a sexy body, ndng a member o the opposite or same gender to be excitingly sharp-witted or unny But carnal longings strike at surprising times too—in the wake o a victory by your avorite team (or men, anyway) or at times o ear or even afer a tragedy, like the death o a parent No matter how lust is triggered, though, sex, like eating or sleeping, is ultmately bochemcal, governed g overned by hormones, neurotransmtters neurotransmtters and other substances that nteract n complcated ways to create the amlar sensatons o desire, arousal, orgasm. By understanding how that happens, scientists should in principle be able to help people like Washington or whom sex
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just isn’t working And indeed, over the past decade or two, scientists have identied many o the pieces o this complex puzzle. It clearly involves testosterone, along with other hormones, including estrogen and oxytocin, and bran chemcals such as dopamne, serotonn and norepnephrne. norepnephrne. And there are numerous other bodly chemcals that turn us on, rangng rom the commonplace, ntrc oxde, to the obscure, vasoactve ntestnal polypeptde. Scientists have also learned that the old notion that 90% o sex is in the mind is literally true: the parts o the brain involved in sexual response include, at the very least, the sensory vagus nerves, the midbrain reticular ormation, the basal ganglia, the anterior insula cortex, the amygdala, the cerebellum and the hypothalamus I all this sounds complicated, it is. Researchers are still struggling to understand how these pieces t together and how they might be dierent or men and women It’s not clear which chemicals o desire are unleashed and under whch crcumstances, because settng and mood, as women know better than men, can make all the derence between be tween arousal and annoyance. Nevertheless, scientists are light-years ahead o where they were in the 1920s and ‘30s, when estrogen and testosterone were rst identied, and they know a great deal more than they dd n the 1940s, when Alred Knsey, ollowed by the research team o Wllam Masters and Vrgna Johnson Johnson n the 1960s, published some o the rst scholarly studies o human sexuality Tose studies concluded that sexual response proceeds in distinct stages, begnnng wth exctement—erecton n men, engorgement o vagnal vag nal and clitoral tissue in women—proceeding to orgasm and nally to “resolution,” in which tissues return to their normal state Tey didn’t delve into biochemistry, though, and it turns out they probably ddn’t get the stages rght ether. In the 1970s psychatrst Helen Snger Kaplan, who ounded the Human Sexuality Program at New York Weill Cornell Medcal Center, Center, ponted out that beore you get g et physcally aroused, you have to eel sexual desire—a statement that seems pretty obvious It’s also pretty obvious to anyone who has been in a heterosexual relationship
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that men and women tend to experence sexualty somewhat derently. derently. So where Masters and Johnson Johnson saw sexual arousal as a lnear progresson toward orgasm, researchers like Dr Rosemary Basson o the University o British Columbia argued in 1999 that women, at least, operate in a more circular pattern. Desre can precede prece de stmulaton or be trggered by t. Satsacton s possible at any o the stages And orgasm org asm isn’t isn’t necessarily the ultimate goal Stimulation, moreover, can take all sorts o orms Says Dr Jennier Berman, a urologist and director o the Female Sexual Medicine Center at : “Women experience desire as a result o context—how they eel about themselves and their partner, how sae they eel, their closeness and ther attachment.” attachment.” Men, says Berman, “tend to be more vsually vsuall y drected drecte d and stmulated than women are.” are.” Tus Playboy and Hooters and the estmated $10 billion-a-year mainly male-oriented male-oriented pornography industry industry But the reasons or that dierence may be as much cultural as they are physiological. Dr. Julia Heiman, a psychologist and director o the Re productive and Sexual Medicine Clinic at the University o Washington Medical School, is one o a growing number o researchers who think it’s misguided to see men as simple and linear and women as complex and circular “I don’t think we’ve taken the time to talk to men about what desire is,” she says “I they are emotional about their sexuality, they don’t eel in step with other men” Women who don’t t stereotypes don’t are much better, says Jim Paus, a psychologst psycholog st at Concorda Unversty n Montreal who studes behavor b ehavoral al neurobiology “What “ What is a woman who expresses arousal in response to blatantly vsual sexual cues? I hope we’ve moved beyond callng her a slut whle callng a man who does doe s the same a stud.” stud.” But the cultural prejudce behnd those labels persists, he says Research by Meredith Chivers at the Center or Addiction and Mental Health, aliated with the University o oronto, shows that women do respond to sexy visual stimuli. In act, in a study recently presented at a Knsey Insttute conerence on emale sexualty, Chvers ound that women
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show physical signs o arousal in response to a wider variety o images (including lms o bonobo chimps mating) than men do But unlike in men, this physical arousal is not closely paired with a subjective eeling o being turned on. In short, physical arousal or women can come beore or even in the absence o conscious desire—doubtless a source o much conusion between the sexes Arousal and desire can also happen at once But while arousal and desire are intimately intertwined and probably nvolve all sorts o eedback between bran and gentala that have yet to be untangled, at least some o the underlying biochemistry is becoming clear Here Here is a catalog o some o the key chemicals o love: love : Letting It Flow
Desire is complicated. Arousal, by contrast, is pretty straightorward: ll the penile arteries with blood or divert blood to the vagina and clitoris, and you’re there “Once the brain gets turned on—however it gets turned on—it’s a relatively simple concept to increase blood ow,” says Dr. Alan Altman, a specalst n menopause and sexualty at Harvard Medcal School. In men, a chemical that acilitates the ow is vasoactive intestinal intestinal polypepp olypeptide, a hormone that also directs the expansion and contraction o smooth muscles in the gastrointestinal tract But the primary chemical in charge o that unction is nitric oxide It’s a vascular trac cop, activating the muscles that control the expansion and contracton o blood vessels. I the mnd s n the mood—or when you pop p op a ntrc-oxde-boostng ntrc-oxde-boostng drug such as Vagra Va gra or Levtra—the Le vtra—the body responds. Men tend to be more ocused on genital stimulation than women, so they are more lkely to perceve an ncreased blood ow to the gentals g entals as arousal, while women may be unaware o it Tat may be one reason why trials o Viagra on women have been disappointing disappointing
Fuels For Lust I there’s one substance that ultmately makes t possble to get turned on in the rst place, testosterone is probably it. “When testosterone is gone,”
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says ’s Berman, “or whatever reason—aging, medication—men ex perience erection and libido problems” Restore the testosterone, and you usually x those problems Women too seem to have problems getting interested in sex when their testosterone levels are too low, which is why Procter & Gamble is experimentng wth testosterone patches. Says Altman: “When women are havng normal menstrual cycles n ther prme reproductve ages, ther ovares make two times more testosterone than estrogen.” A ew days beore ovulation, triggered by surging levels o testosterone—along testosterone—along with other hormones including progesterone and estrogen—sexual estrogen—sexual desire peaks, according to new research by Martha McClintock o the University o Chicago that dispels a long-held theory theor y that ertility precedes desire But or women, at least, estrogen may also be crucial. “Give estrogen to women with decreased desire,” says Paus, “and you don’t restore desire Give them testosterone alone, and you get a little increase in desire. Give them estrogen and testosterone together tog ether,, and you get a whoppng ncrease.” ncrease.” Why? Some research suggests that testosterone’s role in women is diversonary: t attaches to so-called sterod-bndng globulns n the blood that would otherwse latch onto estrogen molecules and render them nert. Te testosterone is taken away to the liver, while the estrogen is ree to make a lust-inducing lust-inducing dash or the brain Paus argues urther urther that estrogen may be the ultmate love hormone or men as well “A lot o studies on rats and birds,” he says, “show that brains are lke gant ovares, n the sense that testosterone testosterone and other androgens androg ens are converted nto estrogens n the hypothalamus. And ths converson appears to be critical to the expression o male sexual behavior” Te Feel-Good Chemical
Both testosterone and estrogen trigger desire by stimulating the release o neurotransmitters in the brain. Tese chemicals are ultimately responsible or our moods, emotions and attitudes. And the most important o
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these or the eeling we call desire seems to be dopamine Dopamine is at least partly responsible or making external stimuli arousing (among other thngs, t’s thought to be the pleasure-trggerng substance underlyng drug addiction). “Being low on dopamine,” says the University o Washington Medical School’s Heiman, “correlates with being low on desire.” And in men dopamne-enhancng drugs (ncludng ( ncludng some antdepressants antdepressants and antParkinson’s medications) can increase desire and erections So can apomor phne, a Parknson Parknson’’s drug that latches drectly onto the dopamne receptors in brain cells and turns them on Another neurotransmitter almost certainly involved in the biochemistry o desire is serotonin, which, like dopamine, plays a role in eelings o satisaction Antidepressants like Prozac, which enhance mood by keeping serotonn n crculaton longer than usual, can paradoxcally depress the ablty to acheve orgasm. But “dopamne and serotonn,” says Heman, “appear to interact with each other in a complicated way to impact desire” So, researchers suspect, do the neurotransmtters epnephrne and norepnephrine, whose usual job is to pump up our energy when we’re in danger Blood-plasma levels o both chemicals increase during masturbation, masturbation, peak at orgasm and then declne, and by-products o norepnephrne metabolsm reman elevated or up to 23 hours afer sex. It’s not yet clear, though, whether this is a cause or an eect o arousal Te Cuddle Hormone
Endocrinologists have known or years that oxytocin, released by the pituitary gland, ovaries and testes, helps trigger childbirth contractions, mlk producton durng nursng and the pelvc p elvc shudders women experence during during orgasm (and possibly the contractions contractions during during male orgasm orga sm as well) well ) Te hormone is believed to play a vital role in mother-child bonding and may do the same or new athers: oxytocn surges when a new dad holds hs h s bundle o joy. Some researchers also think o oxytocin as a cuddle chemical Preliminary studies by psychiatrist psychiatrist Kathleen Light at the University University o
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North Carolna Carolna have ound that oxytocn levels rse afer couples hold hands, hug or watch romantic movies It also may be what makes you want to stay wth your partner untl the mornng afer sex. Tose who can relate to Blly Bl ly Crystal’s “How long do I have to lie here?” scene rom When Harry Met Sally might question whether oxytocin aects both genders equally But there’s increasing evidence that oxytocin is also involved in deeper bonding It certainly plays that role in a much studied little rodent called the prare vole, whch s amous or ts delty to ts mate. Te crtter’s bran releases a rush o oxytocin as it bonds b onds with its beloved Block the chemical, and voles ail a il to make a connection Inject more o the hormone, and they all or each other even aster aster A similar kind o imprinting might take place in humans “Oxytocin release may help us bond to certain eatures in our partners,” says Paus “It’s probably part o the mechanism that generates the template o what we nd attractive.” Te next time you see your partner or someone like your partner, he theorzes, “the oxytocn s actvated. It doesn’t mean you have to be aroused You just think, God, what a beautiul woman”—which might explain why we’re attracted to the same type over and over Attractive Aromas?
Probably the most controversal ssue n the chemstry o sexualty sexual ty s the role o pheromones In 1971 the University o Chicago’s McClintock, then a Wellesley undergraduate, proved scientically what women in dorms had known or decades: menstrual periods become synchronized when women live together It’s probably because o pheromones, she said—olactory chemicals that we can detect even though we’re not aware o them In 1998, she did experiments that proved this hypothesis, but, unlike animal pheromones, no human versions have been isolated Because menstrual menstrual cycles c ycles and sexuality are part o an overall system, it’s it’s possble that pheromones could trgger trgg er desre. Perume makers that market market pheromone-based scents have latched onto this notion It’s plausible, says
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Altman, “but I don’t think the science is very good on it” Paus agrees: “I hope it’s true otally on aith, I believe it Te problem is that the scientist in me says, ‘, but what are these pheromones, and who has shown it?’” A Double Shot Of Love
A newly identied substance that has captured Paus’s interest is alpha melanocyte polypeptide, also known as melanocyte-stimulating hormone () In clinical trials, this pituitary hormone had the dual eect o giving men erections and heightening their interest in sex. Paus is studying a synthetic version or Palatin echnologies o Cranbury, N.J., which is developng t as a nasal nasa l spray. spray. “It’s “It’s astonshng that you have a lttle peptde that has such a big, specic eect,” he says It interacts with dopamine, but how, precisely? “We don’t know,” he says Like all substances that promise to increase desire and perormance, whether they are prescription drugs or olk aphrodisiacs sold next to the cash register at the quick-stop store, is tough to investigate because o the placebo eect As Procter & Gamble discovered with its testosterone patch study, arousal and desire are so entangled with one’s state o mind that it’s tough to gure out cause and eect. Says Altman: “I you’re in a tribal society and taught that something something is an aphrodisiac, it probably will be But someone in Los Angeles taking the same thing probably won’t get the same eect” Maybe that’s just as well. For those who suer rom a lack o nterest n sex, lke Roslyn Washngton, t’s great to have a treatment that works. But lke the women in the testosterone testosterone study who responded to a placebo showed, the real pont s to create a sex le that works. Feelng s belevng, and vce versa. We experence attracton and sexual desre as a sort o magc, a phenomenon lled wth delghtul mystery. mystery. And scentsts scentsts contnue to be overwhelmed by the complex nterplay o dozens o substances percolatng rom mnd to body and back, that keeps the mystery nicely intact —R S S/L A
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