Oxytocin Is Overrated – The Atlantic

Of the dozens of hormones found in the human body, oxytocin might be the most overrated. Linked to the pleasures of romance, orgasms, philanthropy, and more, the chemical has been endlessly touted as the “cuddle hormone,” the “moral molecule,” even “the source of love and prosperity.” He has inspired popular books and ted speaks. Scientists and writers have insisted that spraying it into human nostrils can instill compassion and generosity; Online sellers have marketed snake oil oxytocin concoctions as “Liquid Trust.”

But as my colleague Ed Yong and others have repeatedly writtenmost of what is said about the hormone is, at best, hyperbole. smell the chemical not make people more cooperative or trusting in a reliable way; trials testing it as a treatment for children with autism spectrum disorder have yielded mediocre results. And while decades of great research have shown that the versatile molecule can sometimes cause warm fuzzy lights in all sorts of species—cooperation in meerkatsmonogamy in prairie voles, parental care in marmoset Y sheep-under other circumstancesoxytocin can turn creatures from rodents to humans aggressive, fearfuleven partial.

Now, researchers are discovering that oxytocin may not only be insufficient for strong bonds, but also unnecessary. A new genetic study hints that prairie voles, fluffy, fist-sized rodents that have long been the poster child for oxytocin’s cozy effects, can permanently associate without it. The revelation could shake the foundations of an entire subfield of neuroscience and prompt scientists to reconsider some of the oldest evidence that once seemed to show that oxytocin was the be all and end all of animal affection. It turns out that cuddling can probably happen without the classic cuddle hormone, even in the cutest and most classic critters of all.

Oxytocin is not necessarily obsolete. “This shouldn’t be taken as, ‘Oh, oxytocin doesn’t do anything,’” says Lindsay Sailer, a neuroscientist at Cornell University. But the researchers have good reason to be a little stunned. For all the messy, inconsistent, and even bleak data that has been gathered from human studies of the hormone, the evidence for prairie voles has always been considered rock-solid. The small rodents, native to the Midwestern United States, are famous for being one of the few species of mammals They monogamously mate for life and co-raise their young. Over many decades and across geographies, researchers have documented how rodents pet each other in their nests and comfort each other when stressed, how aggressively rejection the advances of other voles trying to shipwreck. And every time they checked, “there was oxytocin, sitting in the middle of the story, over and over again,” says Sue Carter, a behavioral neurobiologist who pioneered some of the first studies on prairie-vole linkages. The molecular pathways that drive the behaviors seemed just as clear: When triggered by social behavior, such as snuggling or having sex, a region of the brain called the hypothalamus pumped out oxytocin; the hormone then attached to its receptor, causing a series of amorous effects.

Years of Follow, continue studies He continued to bear that thought. When scientists gave prairie voles drugs that prevented oxytocin from binding to its receptor, the rodents began snubbing their mates after any date. Meanwhile, simply stimulating the oxytocin receptor was enough to persuade the voles to settle down with strangers they had never mated with. The connection between oxytocin and pair bonding was so strong, so repeatable, so unquestionable that it became dogma. Zoe Donaldson, a neuroscientist at the University of Colorado at Boulder who studies the hormone, recalls once receiving dismissive comments about a grant because, in the critic’s words, “We already know everything there is to know about prairie voles and oxytocin.” . ”

So, more than a decade ago, when Nirao Shah, a Stanford neurogeneticist and psychiatrist, and his colleagues set out to cleave the oxytocin receptor in prairie voles using a genetic technique called CRISPR, they thought their experiments would be a complete success. Part of the goal was, Shah told me, proof of principle: Researchers have yet to perfect the genetic tools for voles in the same way they have done for more common lab animals like mice. If the team’s manipulations worked, Shah reasoned, they would breed a lineage of rodents that would be immune to oxytocin’s influence, leaving them unfaithful to their mates and indifferent to their young, thus proving that the CRISPR machinery had done its job.

That’s not what happened. The rodents continued to huddle with their families, as if nothing had changed. The finding was puzzling. At first, the team wondered if the experiment had simply failed. “I distinctly remember sitting there and just saying, Wait a second; as there is no differenceKristen Berendzen, a UC San Francisco neurobiologist and psychiatrist who led the study, told me. But when three separate teams of researchers repeated the manipulations, the same thing happened again. It was as if they had successfully removed the gas tank from a car and were still witnessing the engine roaring after a fuel infusion. Something could have gone wrong in the experiments. However, that seems unlikely, says Larry Young, a neuroscientist at Emory University who was not involved in the new study: Young’s team, he told me, has produced nearly identical results in his lab.

Explanations for how decades of oxytocin research might change are still being investigated. Perhaps oxytocin can bind to more than one hormone receptor, something studies have shown hinted at over the years, Carter told me. But some researchers, Young among them, suspect a more radical possibility. Perhaps, in the absence of its usual receptor, oxytocin no longer does anything, forcing the brain to open up an alternate pathway to affect. “I think other things take over,” Young told me.

That idea is not a complete repudiation of previous research. Other experiments with prairie voles that used drugs to alter oxytocin receptors were done in adult animals that grew up on the hormone, says Devanand Manoli, a UCSF psychiatrist and neuroscientist who helped lead the new study. Wired to respond to oxytocin throughout development, those rodent brains couldn’t compensate for their sudden loss late in life. But the Stanford-UCSF team bred animals that lacked the oxytocin receptor. From birthwhich could have caused some other molecule to intervene, capable of binding to another receptor. Perhaps the car never needed gasoline to run: stripped of its tank from the start, it went fully electric.

It would be easy to see this study as yet another blow to the oxytocin propaganda machine. But the researchers I spoke to think the results are more revealing than that. “What this shows us is how important pair bonding is,” Carter told me, for prairie voles, but also potentially for us. For social mammals, associating is not just sentimental. It is an essential piece of how we build communities, survive beyond childhood, and ensure that future generations can do the same. “These are some of the most important relationships any mammal can have,” says Bianca Jones Marlin, a neuroscientist at Columbia University. When oxytocin is around, it’s probably providing the drive behind that intimacy. And if it’s not that way? “Evolution is not going to have a single point of failure for something that is absolutely critical,” Manoli told me. Knocking oxytocin off its pedestal may seem like a disappointment. But it’s almost comforting to consider that the urge to bond is unbreakable.

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