Prairie voles and the science of love and loss

A new study of a small native North American rodent – that might break your heart – has shown that the neurotransmitter dopamine plays a crucial role in in keeping the love alive in intimate relationships.

By studying these tiny rodents, scientists aim to gain new insights into what happens inside human brains that allows us to form intimate social relationships, and how we can recover when those relationships end.

Prairie voles are one of the mere 3-5% of mammals that form monogamous pair bonds. They tend to form long-term partnerships in which they share a home and raise offspring together.

But the researchers had to break the intimate relationships to test their theories.

In one experiment, in which female prairie voles attempted to access a room containing their male partner, researchers used a tiny fibre-optic sensor to track dopamine activity in the nucleus accumbens – a brain region which, in humans, motivates us to seek out rewarding things like water and food.

In one scenario the vole had to press a lever to open a door, and in the other she had to climb over a fence to reunite with her partner.

They found that when the female tried to get to her partner a huge surge of dopamine occurred and continued as they snuggled and sniffed one another. Dopamine levels increased much less when the vole on the other side was a stranger to her.

In another experiment, the couple were kept apart for 4 weeks – long enough for voles in the wild to find another partner. Despite remembering one another when reunited, exhibiting more direct physical contact when investigating their former partner than a stranger, this signature dopamine surge had almost vanished.

“We think of this as sort of a reset within the brain that allows the animal to now go on and potentially form a new bond,” says Zoe Donaldson, associate professor of behavioural neuroscience at the University of Colorado at Boulder in the US and senior author of the paper in the journal Current Biology.

As the study was undertaken in a prairie vole model more research is needed to determine how the results translate to human brains. But the authors believe that the findings could potentially have important implications for people who have trouble forming close relationships, or for those who struggle to recover from loss – a condition known as Prolonged Grief Disorder.

“This [finding] suggests that not only is dopamine really important for motivating us to seek out our partner, but there’s actually more dopamine coursing through our reward center when we are with our partner than when we are with a stranger,” says first-author Anne Pierce, who worked on the study as a graduate student in Donaldson’s lab.

“This research suggests that certain people leave a unique chemical imprint on our brain that drives us to maintain these bonds over time. What we have found, essentially, is a biological signature of desire that helps us explain why we want to be with some people more than other people.”

Donaldson adds: “As humans, our entire social world is basically defined by different degrees of selective desire to interact with different people, whether it’s your romantic partner or your close friends. “The hope is that by understanding what healthy bonds look like within the brain, we can begin to identify new therapies to help the many people with mental illnesses that affect their social world.”

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