Loveless voles show how alcohol harms brain’s bonding chemicals

In the wanton world of rodent hook-up culture, prairie voles (Microtus ochrogaster) stand out for their singular devotion. They would rather eat wild oats than sow them. 

After an extended courtship – about a day –  the first sexual tryst between male and female will generally excite a lasting bond, with the pair settling down to raise a rapidly growing family until death do they part – which admittedly, given the perils of prairie life, usually occurs within a year or two. 

Give a male vole an alcoholic drink, however, and the animal’s natural inclination to monogamous love and commitment evaporates like dew on a mid-western plain under the hot morning sun.

This finding comes courtesy of research by neuroscientists Andre Walcott and Andrey Ryabinin of Oregon Health and Science University in the US, who plied otherwise content vole couples with booze and then pimped a second female into the equation to observe the response. When the couple both drank, they continued to cuddle up together; when only the male drank, his ardour for his partner waned.

These observations are significant because prairie voles are considered useful proxies to study the neurological basis of human pair-bonding. They shed light on how alcohol may directly contribute to damaging brain function crucial for sustaining human intimate relationships. 

Walcott and Ryabin report that when only the males were given alcohol they showed changes to an area of the brain – the periaqueductal grey – that in prairie voles (as with humans) is dense with receptors for the chemicals vasopressin and oxytocin, both associated with social and sexual bonding. Previous studies have shown that dosing montane voles (Microtus montanus), promiscuous cousins of the prairie vole, leads to more monogamous behaviour.

“Not many rodents form long-term social attachments and not many rodents like to drink alcohol,” says Ryabnin. “However, prairie voles are unusual as they are socially monogamous and like drinking alcohol, so they are perfect to investigate the role of alcohol in relationships.” 

Ryabnin’s interest is in developing novel therapies to combat addiction and alcohol use disorders.

“We know that in humans heavy drinking is associated with increased separation rates in couples in which one of the partners is a heavy drinker and the other is not,” he says, “while separation rates don’t seem to increase when both partners drink in a similar manner, or don’t drink at all.”

The identification of biological mechanisms that explain why this is so could lead to medical strategies to mitigate the harm caused by alcohol abuse on relationships, the researchers suggest, though they acknowledge further work will be needed to confirm the neurological response observed in prairie voles is shared by humans.

The research is published in the journal Frontiers in Psychiatry.

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