忠誠荷爾蒙 Hormone may help protect monogamous relationships

Hormone may help protect monogamous relationships

Study shows that monogamous men given the hormone oxytocin will put extra space between themselves and an attractive woman they've just met.

Oxytocin is a brain chemical known to promote trust and bonding. (Jerome Favre / European Pressphoto Agency / November 13, 2012)

By Melissa Healy, Los Angeles Times

November 13, 2012, 6:27 p.m.

If retired Army Gen. David H. Petraeus had gotten an occasional dose of supplemental oxytocin, a brain chemical known to promote trust and bonding, he might still be director of the Central Intelligence Agency, new research suggests.

A study published Tuesday in the Journal of Neuroscience has uncovered a surprising new property of oxytocin, finding that when men in monogamous relationships got a sniff of the stuff, they subsequently put a little extra space between themselves and an attractive woman they'd just met.

Oxytocin didn't have the same effect on single heterosexual men, who comfortably parked themselves between 21 and 24 inches from the comely female stranger. The men who declared themselves in "stable, monogamous" relationships and got a dose of the hormone chose to stand, on average, about 6 1/2 inches farther away.

When researchers conducted the experiment with a placebo, they found no differences in the distance that attached and unattached men maintained from a woman they had just met.

Even when an attractive woman was portrayed only in a photograph, the monogamous men who received oxytocin put a bit more distance between themselves and her likeness. But when the new acquaintance was a man, administration of oxytocin did not prompt attached men to stand farther away than single men, the researchers reported.

The latest findings suggest that oxytocin, which floods the body in response to orgasm, early romance, breast-feeding and childbirth, may act more subtly in humans than has been widely understood.

A mounting body of recent research suggests that boosting oxytocin in the human brain will indiscriminately promote trusting, friendly behavior. Research on female prairie voles has suggested the chemical might play some role in pair-bonding, and in humans playing games of risk and power, it increased empathy and trust in males and females alike. Injected into the cerebrospinal fluid of male rats, oxytocin causes spontaneous erections.

Accordingly, researchers examining oxytocin's effects on people — including the authors of the latest study — assumed that men under its influence would draw closer to women, not farther away.

"This was quite surprising," said Dr. Rene Hurlemann, a psychiatrist at the University of Bonn in Germany, who led the study.

At the same time, the new findings make evolutionary sense, Hurlemann added: As human societies evolved to give men an increasing role in safeguarding and supporting their mates and offspring, it appears that oxytocin may have taken on a more discriminating role in human interaction by favoring staying over straying behavior among men who've already found a mate.

Paul Zak, founding director of Claremont Graduate University's Center for Neuroeconomics Studies, said the new findings squared nicely with research, including his own, suggesting oxytocin doesn't merely make people friendlier — it makes them more empathetic, more attuned to social cues, and more inclined to adjust their behavior accordingly.

But the study also suggests something important about the ways in which the human brain differs from those of other animals, said Zak, who was not involved in the German experiments.

"The finding that one's relationship status affects how oxytocin affects the brain provides some evidence that our brains evolved to form long-term romantic relationships," Zak said. "Hugh Hefner is the exception, not the role model for men."

Inhaled oxytocin was marketed until 1997 in the United States under the name Syntocinon as an aid to new mothers having difficulty with breast-feeding. (It was withdrawn for business reasons unrelated to safety concerns.) In recent years, it has been under investigation as a drug that may help those with autism or schizophrenia to strengthen social skills.

Oxytocin's effects in women are quite clear. It plays a pivotal role in childbirth (its infused synthetic form, called Pitocin, is used to induce labor) and in breast-feeding, where it facilitates the "letdown" of milk.

For men, however, the chemical's effects have been mysterious. High levels of testosterone, for instance, inhibit the release of oxytocin.

Asked whether an oxytocin nasal spray might be used to help philandering males resist temptation, Hurlemann chuckled and asked whether any drug could be so powerful. At the same time, he underscored that high levels of oxytocin — or its more masculine counterpart, the hormone vasopressin — are produced by the body in response to sexual activity, cuddling or even the touch or close physical presence of a mate.

"What we actually simulate is a kind of post-coital posture" with the nasal administration of oxytocin, Hurlemann said. "And why should you actually approach another women when you're in a post-coital situation? It doesn't make much sense."

For women whose partners seem to get a little too friendly with new female acquaintances at parties, he said, the effects of inhaled oxytocin might be achieved by other means.

"It might make a lot of sense to remind him of the relationship, and sexual activity might be one means of achieving this," Hurlemann said. "I'm not sure it's politically correct to say so, but from a biological point of view, it makes sense."

忠誠荷爾蒙 

忠誠荷爾蒙 :  男人體內存在“忠誠荷爾蒙” 可抵制美女誘惑

有的男人能“執子之手，與子偕老”，一輩子對妻子一心一意；有的男人卻連三年之癢都邁不過去，一有美女色誘立刻變心。科學家研究發現，男人對妻子是否三心 二意，與他們身體內一種叫做“忠誠荷爾蒙”的化學物質的分泌有關。能分泌較多忠誠荷爾蒙的男人更能抵制美女的誘惑，能理智控制性衝動，背叛妻子的幾率也更 低。

忠誠荷爾蒙

　　德國波恩大學的科學家對這一課題進行了研究，研究成果刊登在《自然神經科學》雜誌上。科學家發現，忠誠荷爾蒙分泌較多的男性，與異性相處時潛意識裏會 設定一個底線安全距離，大概是10～15厘米。如果異性主動突破這個距離，男性也不會對投懷送抱的美女動心，反而敬而遠之。

　　這種荷爾蒙的分泌量與一種被命名為RS3334的基因片斷相關，這種基因片段上的變化同男人是否忠貞緊密相連 ，它會抑制忠誠荷爾蒙的分泌。有一個或者兩個RS3334片斷的男人，忠誠荷爾蒙的分泌就偏少，在忠貞度上也就大打折扣。

　　科學家發現 ，當男性跟愛人在一起時，體內分泌的忠誠荷爾蒙會增加，這種荷爾蒙的另一個作用是緩解緊張情緒。研究人員收集了一些忠誠荷爾蒙，對57名異性戀男性做了實 驗，這些人當中有半數人坦白經常抑制不住對貌美異性的性衝動。科學家給每個人都噴灑了用忠誠荷爾蒙調製成的噴霧，45分鐘后用貌美女子測試他們抵抗色誘的 能力。實驗結果讓研究人員大吃一驚，有近80%的受試者竟然抵抗住了誘惑。此外，科學家用同樣的辦法對一夫一妻制的小鼠做了實驗，實驗結果與此類似，一些 有亂性習慣的小鼠收斂了許多 ，甚至當有其他雌鼠試圖誘惑它們時，也不為所動，始終忠誠於原配。

　　研究人員樂觀估計，如果這種神奇的荷爾蒙最終能被確認對人體無害，那它將有望加入商業運作，生産出類似能讓男性保持忠誠的藥物。

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