‘Love hormone’ may not be crucial for social bonding after all

Prairie voles form social bonds without an oxytocin sensor in their brains.This finding challenges long-held beliefs that hormones are an important part of the bonding process in all mammals.

To Sam Jones

Monogamous prairie voles, which lack receptors for the “love hormone” oxytocin, still bond with mates and offspring. This contradicts long-held assumptions about how essential oxytocin is for these behaviors.

Oxytocin, also known as the “cuddle chemical,” is released in the brain during romantic intimacy, parenting, and other social bonding moments, as well as during labor and breastfeeding. I have studied the role of hormones in the brains of many mammalian species, including prairie voles (Microtus Okrogaster). These voles were of particular interest to researchers, unlike other experimental animals such as mice and rats. Because Prairie her voles show strong attachment to her one long-term partner. It’s a behavior called pair bonding.

For decades, pharmacological research has suggested that oxytocin receptors (proteins scattered on the outside of the cell to which oxytocin molecules bind) are essential for producing binding behavior. When Devanand Manoli and his colleagues at the University of California, San Francisco used CRISPR gene-editing technology to remove the oxytocin receptor in prairie voles, they were shocked to discover that the animals were still mating.

Manoli still remembers the moment co-author Kristen Berenzen walked into the lab and broke the news. “We fell to the floor,” he recalls.

Prairie voles lacking oxytocin receptors were also able to bear and raise young, and were able to groom and cuddle for long periods of time. I was acting very similar.

However, vole pups born to mothers lacking oxytocin receptors lost significant weight by the time they reached weaning age, suggesting that mothers had problems with milk production and feeding. . They were also less likely to survive to weaning. Thus, although pair bonding and other important social behaviors were unaffected, oxytocin receptors still appear to play an important role in the development of vole offspring.

“What I love about the paper is that it specifically looks at partner preferences, but it also has these major issues with childbirth and parenting,” said Robert Fromke of New York University’s Grossman School of Medicine. I’m here. “These basic processes of birth and lactation that make us mammals are poorly understood.”

Manoli says the findings make more sense once the initial shock subsides.

“It’s not surprising that a behavior as important to a species as attachment has no single point of failure,” he says. The failure of past clinical trials of oxytocin in people with social anxiety disorder, schizophrenia and other conditions could also be explained by a more complex system. Such trials were aimed at forming social attachments and alleviating the problems people were experiencing in handling social situations appropriately.

“When the effects from pharmacology first became apparent, there was hope that oxytocin could become a major therapeutic intervention,” says Manoli. and the patient’s social behavior did not improve dramatically. Oxytocin may be just part of the hormonal mosaic behind the bond.

Manoli and his colleagues wondered what chemical processes in the brain might be compensating in the absence of oxytocin receptors, or whether oxytocin binds to other receptors in the brain that are important. We are investigating whether it is possible that social attachment is possible.