WEDNESDAY, Oct. 15, 2008 (HealthDay News) -- Pity the lovelorn prairie vole. A new study finds that when this monogamous rodent is separated from a mate, its brain starts a process that ends in lovesickness.
The same mechanism might drive the feelings humans get when parted from a longtime mate, scientists say.
And it could also keep couples together -- even when it's not good for them.
"We all know of people who are in a long-term relationship where you can't imagine why they are together. It may be that we are getting glimpses of real brain mechanisms that are causing that," said study senior author Larry Young, a psychiatry professor at Emory University's Center for Behavioral Neuroscience, in Atlanta.
He and his colleagues published their findings Oct. 15 in the journal Neuropsychopharmacology.
It's not a stretch to compare the love life of the prairie vole to that of humans, say scientists who study the neuroscience of human coupling. The female vole lives less than two years and gives birth once every 21 days, but she spends her entire life with the same male. This kind of monogamy is rare in the animal kingdom, Young added.
"But in some species, there is something else that happens -- a bond forms between the two that can last one season or multiple seasons," he said. "It's not just about sex, it's about the relationship between the two."
So, the prairie vole has long been a relied-upon animal model for human coupling, which tends toward monogamy. In September, for example, researchers in Sweden announced they had found a "bonding gene" that seemed to encourage men to stay faithful. That work stemmed from previous studies conducted with male prairie voles.
In this latest work, Young and his group examined the brains of a variety of adult male voles. Some of the voles had lifelong female partners, while other hadn't had time to form such bonds and were best acquainted with brother or sister voles.
All of the voles were subjected to brief stress tests, such as a swimming challenge, or being placed in a maze.
"The ones who were [still] with a partner, or had just been separated from a sibling so they never formed a romantic bond in the first place, actively avoided the aversive or stressful situation," Young noted.
But what about male voles who had been recently separated from a longtime female partner?
These voles "basically were passive -- they gave up," Young said. "I would be hesitant to say that these animals were depressed, but their behavior is reminiscent of what you would see in a depressed person."
Examination of the brains of the lovesick voles revealed heightened activity of a chemical messenger called corticotropin releasing factor (CRF) in an area of the hypothalamus, a center for emotions in the brain.
When the researchers administered a drug that blocked CRF activity, voles who'd been separated from their mate began to perform just as vigorously in the stress tests as all the other voles tested. It seemed the drug "switched off" the mechanism -- and their lovesickness, as well.
Young's team said it's important to note that CRF activity kicked in only when the vole was separated from a longtime female partner, not a sibling companion.
That suggests a neurological mechanism that pushes monogamous males and females back together.
"Separating, you experience an aversive reaction. And you are driven to go back to the partner to alleviate that," Young said. "Maybe that plays an important role in maintaining relationships."
While the study is aimed at better understanding how the brain reacts to partner loss, the notion of a pharmaceutical fix for lovesickness isn't out of the question, experts said.
Drugs that suppress CRF "in some studies have been shown to function as antidepressants," noted Hasse Walum, a researcher at Sweden's Karolinska Institute who co-authored the bonding gene study.
According to Walum, it would be interesting now to see if anti-CRF drugs "would be more effective in reducing depression induced by partner loss than they would be helping patients suffering from depression caused by other factors."
He also noted that humans vary widely in how severely they react to the loss of a longtime romantic partner, perhaps because their genes govern CRF activity differently.
Another expert believes that lovesickness can lead to very real illness, so it's worth investigating.
"When it becomes detrimental to your functioning in life and health, that's when it's important to understand this and to find potential treatments," said Paul Sanberg, director of the Center of Excellence for Aging and Brain Repair at the University of South Florida, Tampa.
But the day when humans can take a pill to help forget a love affair gone bad is still far off, Young cautioned.
"I don't want to say that this is leading directly to any kind of treatment," he added. "What this will lead to is, perhaps, some investigations in humans to find if this system is involved and could it possibly be targeted, if we need to."
There's more on how the mind works at The Whole Brain Atlas.