Prairie voles are extremely social, forming monogamous mating relationships, in addition to peer relationships akin to human friendships. Finding out the hormones concerned in social bonding might assist scientists perceive human social interactions and issues that hinder the formation of shut relationships. Credit score: Beery lab / UC Berkeley
A brand new UC Berkeley research exhibits that the so-called love hormone oxytocin can also be vital for the formation of friendships. The paper is revealed within the journal Present Biology.
Oxytocin is launched within the mind throughout intercourse, childbirth, breastfeeding and social interactions and contributes to emotions of attachment, closeness and belief. By no means thoughts that it is also related to aggression; the hormone is often known as the “cuddle” or “happy” hormone, and persons are inspired to spice up their oxytocin ranges for higher well-being by touching associates and family members, listening to music and exercising.
However latest research involving the prairie vole have referred to as this love affiliation into query. They’ve proven that oxytocin, which within the mind acts as a neuromodulator, shouldn’t be important for long-term mate bonding, or “social monogamy,” or for parenting habits, although with out it, voles take longer to type such bonds.
Scientists concentrate on prairie voles, as a result of like people, they type secure and selective relationships. Whereas most research concentrate on mate bonds, the Beery lab at UC Berkeley is especially taken with selective peer relationships, analogous to human friendships. Such research might make clear human psychiatric situations, similar to autism and schizophrenia, that intervene with an individual’s means to type or keep social bonds.
“Prairie voles are special because they allow us to get at the neurobiology of friendship and how it’s similar to and different from other types of relationships,” mentioned Annaliese Beery, a UC Berkeley affiliate professor of integrative biology and neuroscience and senior writer of the research.
UC Berkeley graduate scholar Alexis “Lexi” Black holding a sagebrush vole, one of many species being surveyed to find out their social habits. Credit score: Annaliese Beery/UC Berkeley
Beery and integrative biology graduate scholar Alexis Black, one of many two first authors of the research, discovered that prairie voles that lack oxytocin receptors take longer than regular voles to type peer relationships. Prairie voles which are shut associates usually huddle facet by facet, groom and even sit on each other.
“Oxytocin seems to be particularly important in the early formation phase of relationships and especially in the selectivity of those relationships: ‘I prefer you to this stranger,’ for example,” Beery mentioned. “The animals that didn’t have intact oxytocin signaling took longer to form relationships. And then when we challenged those relationships by making new groups, they lost track of their original partners right away.”
The voles, genetically modified within the UC San Francisco laboratory of collaborator and co-author Dr. Devanand Manoli, additionally lacked the social rewards that usually come from selective attachments—they did not work very exhausting to snuggle up with their associates and had been much less avoidant of and fewer aggressive in direction of strangers.
“In other words, oxytocin is playing a crucial role not so much in how social they are, but more in who they are social with, their selectivity,” she mentioned.
Missing oxytocin receptors additionally modified the regulation of oxytocin availability and launch within the mind, which the group documented utilizing a novel oxytocin nanosensor in collaboration with postdoctoral fellow Natsumi Komatsu and Markita Landry, a UC Berkeley professor of chemical and biomolecular engineering.
“That helped us understand the feedback consequences of lacking this receptor, and how oxytocin signaling was altered in the brain,” mentioned Beery.
What social voles inform us about social people
Beery has lengthy been taken with social relationships in rodents, focusing totally on the animals’ seldom-studied peer or friendship relationships. Whereas voles are her primary focus, she believes learning related behaviors throughout a number of species is essential to figuring out what’s species-specific versus generalizable throughout species.
To enrich her laboratory analysis, she has performed subject research evaluating social habits and oxytocin receptor distribution within the mind inside and throughout species in a gaggle of South American rodents and North American Belding’s floor squirrels, which fluctuate in whether or not or not they reside in teams. She additionally lately started subject checks of a number of vole species—there are about 50 worldwide—to check their social habits.
She suspects that in rodents similar to voles, and maybe in different mammals, the formation of peer relationships could have preceded the evolution of monogamous mating relationships.
“While most rodents prefer to interact with unfamiliar individuals, it turns out that the majority of vole species we’ve tested in our early trials form peer-partner preferences, which is what we call these selective friendships. So there seems to be this widespread tendency to bond,” Beery mentioned.
“But only a couple of those species are also monogamous. Someday, I hope to be able to tell you, ‘Do selective peer relationships precede the development of monogamy? Is that why monogamy has evolved so many times in this genus?’ I think this familiarity preference is deeply rooted.”
Beery was a co-author of a 2023 research led by Manoli that threw into query the affiliation of oxytocin with intercourse and parenting. That research confirmed that prairie voles unable to reply to oxytocin exhibit the identical monogamous mating, attachment and parenting behaviors as common voles. These voles had been genetically engineered to haven’t any mobile receptors for oxytocin, and had been the identical voles used within the present research.
However whereas oxytocin is not important for eventual bond formation, extra research by the identical group revealed in 2024 confirmed that these receptor-deficient (or “null mutant”) prairie voles took about twice so long as regular voles to ascertain a relationship with a possible mate.
Involved in how the shortage of an oxytocin receptor impacts voles’ friendship bonds, versus mating bonds, Beery and Black performed three units of experiments. In a single, they examined how lengthy it took for voles to ascertain a desire for a accomplice. Whereas regular voles take about 24 hours of shut proximity to type a relationship that makes them select that accomplice over a stranger, oxytocin receptor-deficient voles confirmed no desire in that period of time, and took as much as per week to ascertain a peer desire.
“Wild-type animals form this incredibly robust preference within one day of co-housing, but the null mutants have no sign of a relationship after 24 hours. After a week, they mostly get there, and the lifetime partners look no different from each other,” Beery mentioned. “Our conclusion from that experiment is that oxytocin isn’t required to have a relationship, but it’s really important in those early phases of a relationship to facilitate it happening quickly and efficiently.”
They then put long-term pair-bonded voles in a party-like, mixed-group state of affairs: an enclosure with different voles and plenty of rooms related by tubes. In such a state of affairs, regular voles would hang around with identified associates till they finally began to socialize with strangers.
“They can all separate, they can all come together, or they can hang out in any combinations that they want,” she mentioned. “The wild-type animals keep track of who they know. It’s like if I went to a party with a friend, I would stand near that friend for the first part of the party and then I might start to mingle. The voles that lack oxytocin receptors just mixed. It was as if they didn’t even have a partner in there with them.”
Within the third experiment, they examined the power of each peer and mate bonding by having the voles press levers to get entry to both a buddy/mate or a stranger.
“Female wild-type voles typically press more to get their partner than to get a stranger, in both peer and mate relationships. The oxytocin receptor-deficient mutants also press more to get to their mating partner, but not for peer relationships,” Beery mentioned. “That makes sense at some level because we think mate relationships are more rewarding than peer relationships, or at least they depend more on reward-signaling pathways.”
Lack of oxytocin signaling thus not solely delays the formation of relationships, but in addition creates deficits in long-term peer relationships.
On the flip facet, voles missing oxytocin receptors had been additionally much less aggressive towards strangers and fewer avoidant of them.
“You can see contributions of oxytocin signaling to both sides of selectivity,” Beery mentioned. “On the prosocial side, it’s involved in wanting to be with a known friend or peer, while on the antisocial side, it’s aiding in rejecting an unfamiliar animal. We’ve seen effects of oxytocin on both affiliation and aggression in our other studies in prairie voles, and it parallels human findings on a role of oxytocin in in-group/out-group dynamics.”
Oxytocin nanosensors
The researchers used a brand new oxytocin sensor developed in Landry’s UC Berkeley lab to find out whether or not lack of an oxytocin receptor induced will increase or decreases in oxytocin launch. If oxytocin launch elevated in these voles, it might doubtlessly work together with a receptor for the same neuropeptide that can also be concerned within the formation of social relationships, compensating for the absence of oxytocin receptors.
Landry, an affiliate professor within the departments of chemical and biomolecular engineering, neuroscience, and molecular and cell biology and a co-corresponding writer of the paper, created these sensors from carbon nanotubes joined with particular single-stranded DNA sequences chosen as a result of they latch onto the oxytocin molecule and fluoresce. Komatsu and Landry discovered no extra of oxytocin within the voles’ brains. In reality, oxytocin was being launched in decrease quantities from fewer websites within the nucleus accumbens, a key mind area for social reward throughout species.
Co-authors with Black, Komatsu, Beery, Landry and Manoli are Jiaxuan Zhao, Scarlet Taskey and Nicole Serrano of UC Berkeley, and Ruchira Sharma of UCSF.
Extra info:
Alexis M. Black et al, Oxytocin receptors mediate social selectivity in prairie vole peer relationships, Present Biology (2025). DOI: 10.1016/j.cub.2025.07.042
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