The Chemistry of Love - Hóa học tình yêu

There are a lot of chemicals racing around your brain and body when you're in love. Researchers are gradually learning more and more about the roles they play both when we are falling in love and when we're in long-term relationships. Of course, estrogen and testosterone play a role in the sex drive area (see How Sex Works). Without them, we might never venture into the "real love" arena.

That initial giddiness that comes when we're first falling in love includes a racing heart, flushed skin and sweaty palms. Researchers say this is due to the dopamine, norepinephrine and phenylethylamine we're releasing. Dopamine is thought to be the "pleasure chemical," producing a feeling of bliss. Norepinephrine is similar to adrenaline and produces the racing heart and excitement. According to Helen Fisher, anthropologist and well-known love researcher from Rutgers University, together these two chemicals produce elation, intense energy, sleeplessness, craving, loss of appetite and focused attention. She also says, "The human body releases the cocktail of love rapture only when certain conditions are met and ... men more readily produce it than women, because of their more visual nature."

Researchers are using functional magnetic resonance imaging (fMRI) to watch people's brains when they look at a photograph of their object of affection. According to Helen Fisher, a well-known love researcher and an anthropologist at Rutgers University, what they see in those scans during that "crazed, can't-think-of-anything-but stage of romance" -- the attraction stage -- is the biological drive to focus on one person. The scans showed increased blood flow in areas of the brain with high concentrations of receptors for dopamine -- associated with states of euphoria, craving and addiction. High levels of dopamine are also associated with norepinephrine, which heightens attention, short-term memory, hyperactivity, sleeplessness and goal-oriented behavior. In other words, couples in this stage of love focus intently on the relationship and often on little else.

Another possible explanation for the intense focus and idealizing view that occurs in the attraction stage comes from researchers at University College London. They discovered that people in love have lower levels of serotonin and also that neural circuits associated with the way we assess others are suppressed. These lower serotonin levels are the same as those found in people with obsessive-compulsive disorders, possibly explaining why those in love "obsess" about their partner.

Chemical Bonding

Love Junkies There are those who may be addicted to that love "high." They need that amphetamine-like rush of dopamine, norepinephrine and phenylethylamine. Because the body builds up a tolerance to these chemicals, it begins to take more and more to give love junkies that high. They go through relationship after relationship to get their fix.

In romantic love, when two people have sex, oxytocin is released, which helps bond the relationship. According to researchers at the University of California, San Francisco, the hormone oxytocin has been shown to be "associated with the ability to maintain healthy interpersonal relationships and healthy psychological boundaries with other people." When it is released during orgasm, it begins creating an emotional bond -- the more sex, the greater the bond. Oxytocin is also associated with mother/infant bonding, uterine contractions during labor in childbirth and the "let down" reflex necessary for breastfeeding.

Vasopressin, an antidiuretic hormone, is another chemical that has been associated with the formation of long-term, monogamous relationships (see "Are We Alone in Love?"). Dr. Fisher believes that oxytocin and vasopressin interfere with the dopamine and norepinephrine pathways, which might explain why passionate love fades as attachment grows.

Endorphins, the body's natural painkillers, also play a key role in long-term relationships. They produce a general sense of well-being, including feeling soothed, peaceful and secure. Like dopamine and norepinephrine, endorphins are released during sex; they are also released during physical contact, exercise and other activities. According to Michel Odent of London's Primal Health Research Center, endorphins induce a "drug-like dependency."

The Long Haul?

©2002 FOX BROADCASTING Homer and Marge of "The Simpsons" stay together week after week.

What about when that euphoric feeling is gone? According to Ted Huston at the University of Texas, the speed at which courtship progresses often determines the ultimate success of the relationship. What they found was that the longer the courtship, the stronger the long-term relationship.

The feelings of passionate love, however, do lose their strength over time. Studies have shown that passionate love fades quickly and is nearly gone after two or three years. The chemicals responsible for "that lovin' feeling" (adrenaline, dopamine, norepinephrine, phenylethylamine, etc.) dwindle. Suddenly your lover has faults. Why has he or she changed, you may wonder. Actually, your partner probably hasn't changed at all; it's just that you're now able to see him or her rationally, rather than through the blinding hormones of infatuation and passionate love. At this stage, the relationship is either strong enough to endure, or the relationship ends.

If the relationship can advance, then other chemicals kick in. Endorphins, for example, are still providing a sense of well-being and security. Additionally, oxytocin is still released when you're having sex, producing feelings of satisfaction and attachment. Vasopressin also continues to play a role in attachment.

Are We Alone in Love?

Photo courtesy USGS Prairie vole

Only three percent of mammals (aside from the human species) form "family" relationships like we do. The prairie vole is one such animal. This vole mates for life and prefers spending time with its mate over spending time with any other voles. Voles even go to the extreme of avoiding voles of the opposite sex.

When they have offspring, the couple works together to care for them. They spend hours grooming each other and just hanging out together. Studies have been done to try to determine the chemical makeup that might explain why the prairie vole forms this lifelong, monogamous relationship when its very close relative, the montane vole, does not.

According to studies by Larry Young, a social attachment researcher at Emory University, what happens is that when the prairie vole mates, like humans, the hormones oxytocin and vasopressin are released. Because the prairie vole has the needed receptors in its brain for these hormones in the regions responsible for reward and reinforcement, it forms a bond with its mate. That bond is for that particular vole based on its smell -- sort of like an imprint. As further reinforcement, dopamine is also released in the brain's reward center when they have sex, making the experience enjoyable and ensuring that they want to do it again. And because of the oxytocin and vasopressin, they want to have sex with the same vole.

Because the montane vole does not have receptors for oxytocin or vasopressin in its brain, those chemicals have no effect, and they continue with their one-night stands. Other than those receptors, the two vole species are almost entirely the same in their physical makeup.

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