As you gaze across the candlelit dinner at your loved one tonight, you should hope part of her brain is flooded with oxytocin. Or in his case, vasopressin.
If there is no special someone for you on Valentine's Day, it might be the way you smell. If you are in a lousy relationship, it could be your genes (or your spouse's).
Though love has inspired countless poems and odes to its power and mystery, it is nothing more than sophisticated neurochemical signaling.
"Even complex emotions like love are really just the result of a complex series of biochemical events in the brain, neurons communicating in some way," said Larry J. Young, a professor of psychiatry at Emory University's School of Medicine and a researcher at Yerkes National Primate Center. "That experience that we feel that we think is uniquely human and very special is really the result of these biochemical reactions."
Dr. Young found components of that reaction by studying prairie voles -- rodents that are monogamous, very social and raise their young as a couple -- and comparing them to the similar but asocial meadow vole.
The neurochemical oxytocin is important in birth and breast-feeding and is thought to help the mother bond with the child, so it was a good target in figuring out why females bond to males, Dr. Young said. He found there are large concentrations of receptors for the chemical in the reward and addiction section of the female brain.
A similar concentration for the neurochemical vasopressin helps males bond to females, Dr. Young said. Meadow voles lack these concentrations of receptors in that area of the brain.
A variation in a certain gene seemed to influence whether the animals were social, and a study in humans found people who carried this variant were twice as likely to report marriage trouble or not be married at all, Dr. Young said. The variant has also been implicated in autism.
"I think that these molecules are really helping us tune into other people, into the people around us, and take in the social information, and if you have a certain variant, you process that social information differently," Dr. Young said. "I think it contributes to the natural variation that we see among people that we meet every day and how social they are, how socially attuned they are. Some people just don't get it; they're just socially inept. I think that this may contribute to that."
It also might point the way toward treatment. Studies show inhaling a spray of oxytocin makes you more trusting, Dr. Young said, and it could become a component of couples therapy.
"That drug may not actually directly produce love, but it may cause you to have a better understanding of your spouse," he said.
That or similar drugs working on these neurochemicals could also help autistic children who have trouble reading body language or picking up on facial cues, if they were given it during socialization sessions.
"These molecules might make you open up to that so that you can then learn from them," Dr. Young said.
What chemicals can't do is inspire love or mating, as pheromones do in animals. The Dana Foundation, in a recent article titled, "The Chemistry of Love: In Search of the Elusive Human Pheromone," noted that 50 years of research had failed to turn up a human pheromone, if one even exists.
Duke University neurobiologist Hiroaki Matsunami might have found part of the reason. He is studying the chemical androstenone, a pheromone secreted by male pigs to help them mate with females in heat.
The chemical appears to have an effect on people when researchers look at things such as skin conductances tests, Dr. Matsunami said. But he found reaction to the smell varied widely based on whether people had a certain gene variant in a receptor in the nose.
"These are really interesting chemicals because some people like it, other people don't, and other people like me cannot smell them at all," Dr. Matsunami said.
"The smell is a disgusting smell for some people," he said. "I bring this chemical in my class, and like 20-30 percent of people really hate it."
So the search continues for something that will explain why some chemicals can affect the appetite for love.
"It is something that we know to be affected," Dr. Matsunami said. "There are certain components, a smell affecting your emotions, yet it seems so mysterious. It's not as direct as visual cues. So it's doing something but we don't know how it is doing it or why it is doing it. I think that is the most fascinating point of the research at the moment."
So if science can't help you yet, try some roses. It might help with the smell.
Reach Tom Corwin at (706) 823-3213 or firstname.lastname@example.org.
HEAD VS. HEART
The source of love is in the head, not the heart. Researchers focused on explaining the biology of romantic love have found that love mostly can be understood through brain images, hormones and genetics.
One of the research findings isn't so complimentary: Love works chemically in the brain like a drug addiction.
"Romantic love is an addiction: a wonderful addiction when it is going well, a horrible one when it is going poorly," said Helen Fisher, a researcher and professor at Rutgers University. "People kill for love. They die for love."
-- Associated Press
Scientists examined the mystery of what happens when lips lock. Kissing, it turns out, unleashes chemicals that ease stress hormones in both sexes and encourage bonding in men, though not so much in women.
In an experiment, pairs of heterosexual college students who kissed for 15 minutes while listening to music experienced significant changes in their levels of the chemicals oxytocin, which affects pair bonding, and cortisol, which is associated with stress. Levels of the chemicals in their blood and saliva were compared before and after the kiss.
-- Associated Press