Lessons in Love From Voles

For years, scientists have known that oxytocin is important in facilitating the feeling of love in humans. How do they know? Prairie voles. For years, scientists have relied on the cuddly rodents to help us humans understand how this protein works in our brains. But within the past few years, research has complicated that understanding, prompting the question: Can love prevail without the "love" hormone? (encore) Help shape the future of Short Wave by taking our survey: npr.org/shortwavesurvey http://npr.org/shortwavesurvey Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave http://plus.npr.org/shortwave. See pcm.adswizz.com https://pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences. NPR Privacy Policy https://www.npr.org/about-npr/179878450/privacy-policy

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• 0:44Emily Kwong?

  You're listening to Short Wave from NPR. Hey, short waivers. Emily Kwong here. It's Valentine's Day, so seems like the perfect time to take a deep dive into the neuroscience of lerv, specifically rodent love. I'm here with John Hamilton, NPR's own expert on merine romance. Hello, John.

• 1:07Speaker 02

  Hi, Emily. And way too casually dropped that AP vocabulary word, respect.

• 1:12Emily Kwong?

  Thank you, thank you.

• 1:13Speaker 02

  But Valentine's Day, you know, it does give us a brilliant excuse to talk about a very special rodent, one that gives love a good name.

• 1:21Emily Kwong?

  Which rodent are we talking about?

• 1:23Speaker 02

  Well, of course, we are talking about the humble prairie vole. You've probably seen one, but you might not have realized it because you thought it was a mouse. So prairie voles, you can tell the difference, I am told, because they tend to be a little thicker, smaller ears, bigger eyes. But really, for today's purposes, looks are not important. What counts about the prairie voles is their social behavior, especially when it comes to love.

• 1:49Emily Kwong?

  But how do you even know a prairie vole is in love?

• 1:53Speaker 02

  Well, you don't. I mean, obviously, there is no way to know exactly what some little furry creature is feeling in their heart of hearts. But scientists do know that prairie voles tend to mate for life. And once they do, these little vole couples also co-parent. They share a nest. And they spend lots of quality time snuggled up with their life partner.

• 2:14Emily Kwong?

  Way to be voles.

• 2:15Speaker 02

  But you don't have to take my word for it. Here is Dr. Dev Manoli. He's a psychiatrist at the University of California, San Francisco. And he has spent a lot of time studying prairie voles.

• 2:26Speaker 03

  Until they meet a member of the opposite sex, they're kind of just waiting to fall in love, as it were. And then when they mate, they form this attachment. And this attachment shows up in a couple of different ways. One of the behaviors that's really, you know, sort of the most adorable is this huddling behavior, just sort of huddling with each other. They'll sometimes groom. Sometimes they just fall asleep because it's very calming. And that's very specific to the pair bonded partner.

• 2:48Emily Kwong?

  I know what this is. This is just a cuddle puddle. But I guess in the case of voles, it's a huddle puddle.

• 2:54Speaker 02

  It's very sweet. And I gotta say, it's a little bit like some human couples I have known.

• 3:00Emily Kwong?

  Yes.

• 3:00Speaker 02

  And that is probably why prairie voles get a lot of attention from researchers like Dev. You know, it turns out these rodents are really good models of certain human social behaviors, especially what scientists call pair bonding. Which brings us to the brain science stuff.

• 3:16Emily Kwong?

  Right. The neuroscience of love.

• 3:18Speaker 02

  Exactly. So decades ago, prairie voles helped scientists show the importance of this protein in the brain called oxytocin.

• 3:25Emily Kwong?

  Ah, yeah.

• 3:26Speaker 02

  Yes, it plays a big role in pair bonding in both prairie voles and humans. And we've all heard about oxytocin because it is the love hormone.

• 3:34Emily Kwong?

  I've heard it referred to as the potion of devotion on this very show.

• 3:38Speaker 02

  All of that. But there is a new study out that suggests love can prevail even without oxytocin, at least in prairie voles.

• 3:53Emily Kwong?

  Today on the show, love, oxytocin, and some rodent role models. John, can we call it the Volentines special?

• 4:01Speaker 02

  Pretty sure you just did.

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• 5:05Emily Kwong?

  Happy fall. Yes, the days are getting shorter and colder, and the rain can be a drag. But this is also the perfect time of year to get cozy. Life Kit has lots of ideas so you can embrace the change of seasons with episodes on everything from making soup to exercising outdoors. Listen to the Life Kit podcast in the NPR app or wherever you get your podcasts.

• 5:28Emily Kwong?

  OK, John, before we get into the world of love research and this shakeup around oxytocin, explain to me why scientists, in an effort to understand human relationships, have been looking at voles? I've never even heard of a vole.

• 5:44Speaker 02

  OK, so here's the reason. Humans and prairie voles are both sort of anomalies in terms of pair bonding and parenting. Of course, we know that lots of birds mate for life, but mammals tend to be, how shall I say this, pretty promiscuous.

• 5:59Speaker 02

  And that includes most rodents and including most voles. Prairie voles are the exception, and they actually choose the partner they're going to be with. So it's not like, say, a duckling that just imprints on the first creature it sees after hatching. I actually called up one of the scientists who did a lot of the early work on prairie voles. Her name is Sue Carter, and she's on the faculty at both the University of Virginia and Indiana University.

• 6:23Speaker 06

  The wonderful thing about this species is that they're going through some kind of learning process to pick a partner. And that learning process Probably is based on the same physiology that human social attachments are.

• 6:41Emily Kwong?

  So they're scrolling through vol Tinder looking for love.

• 6:44Speaker 02

  Swipe left or swipe right, you know, man.

• 6:47Emily Kwong?

  When they do, uh, where does oxytocin come in?

• 6:51Speaker 02

  Well, so back in the eighties and nineties, Sue Carter helped show that oxytocin levels rise when a prairie vol meets that special someone. She and others did these lab experiments showing that if you give a prairie vol extra oxytocin, it increases their tendency to pair bond. But if you give a drug that blocks oxytocin, they won't pair bond at all. And oxytocin levels, by the way, also seem to predict a lot of human pair bonding behavior.

• 7:16Emily Kwong?

  Well, decades of research sounds like a slam dunk to me. Oxytocin really is the love hormone.

• 7:23Speaker 02

  That, that is the conventional wisdom in popular culture and everything. There's even a Billie Eilish song called Oxytocin. Key lyric, you know, I need you for the oxytocin.

• 7:33Emily Kwong?

  It's an expecting Billie to come in.

• 7:36Speaker 02

  My kids told me about her.

• 7:38Emily Kwong?

  Oh, good. Yes. I'm glad that you're up on the latest.

• 7:41Speaker 02

  Yeah, a totally reliable source. And speaking of scientists, you know, that scientist, Dave Manoli?

• 7:47Emily Kwong?

  Yeah.

• 7:47Speaker 02

  The one who was talking about how prairie vol couples like to huddle? He was a total believer in the love hormone idea until he wasn't, at least not so much.

• 7:57Emily Kwong?

  So what happened?

• 7:58Speaker 02

  What happened was Dave was part of this team at UCSF in Stanford that did an experiment with prairie voles. What they did is they removed fertilized eggs from female voles. Then they used a technique called CRISPR to edit the genes in a way that got rid of the oxytocin receptor. Then they put the embryos back in female voles and waited for the pups to arrive.

• 8:20Emily Kwong?

  And what did that do?

• 8:22Speaker 02

  The idea here was that they were going to create baby voles whose cells wouldn't respond to the love hormone. You know, the, they would neutralize the effects of oxytocin.

• 8:31Emily Kwong?

  Got it.

• 8:32Speaker 02

  Dave figured that the result would affect pair bonding, not surprisingly. And at least that's what he thought until he got a visit from his postdoc who was doing the actual studying of these animals.

• 8:42Speaker 03

  I still remember her coming into the office and, you know, she was holding a graph and it was kind of sat down. She said, so we finally finished the scoring and they form partner preferences perfectly like wild type. And I mean, we were shocked. Because that was really, really not what we expected.

• 8:59Emily Kwong?

  Yeah, I mean, it it sounds like a complete shock, like that they were able to form a pair bond without oxytocin, love without the love hormone. How is that possible?

• 9:10Speaker 02

  Well, to be precise here, we're talking about love without the love hormone receptor.

• 9:15Emily Kwong?

  Right.

• 9:16Speaker 02

  So you know, the molecule that that makes cells respond to oxytocin. One possibility here is that signals from oxytocin itself were still somehow, you know, getting through. Another possibility is that animals born without any oxytocin receptors are able to rely on other systems, you know, in their biology to make sure that they will find true love when they grow up. And Dev thinks it may have to do with the fact that prairie voles really can't survive without pair bonding. So they've evolved these redundant systems to produce that behavior.

• 9:48Speaker 03

  Because of evolution, the parts of the brain and the circuitry that are responsible for pair bond formation don't really rely on oxytocin. So the way that I have been phrasing it is, you know, oxytocin might be love potion number nine, but one through eight are still in play, right? There's more there than than that one entry point.

• 10:03Emily Kwong?

  I'm so intrigued by one through eight. Do scientists know what these other love potions are?

• 10:10Speaker 02

  They know a little bit. Sue Carter, actually, has done a lot of the research on another molecule called vasopressin. She thinks it also affects social behavior, though not as much as oxytocin. And she says there may be other love hormones that just haven't been discovered yet. I should also note that Sue sounded kind of pleased when she found out that removing a single receptor wasn't enough to end a rodent's search for love.

• 10:35Speaker 06

  We thought we would disrupt it. But remarkably, the prairie vole wasn't really buying that, wasn't going to allow us to disrupt it just by taking away one piece.

• 10:48Emily Kwong?

  Love finds a way. At least vole love did in this case. John, is there a life lesson for humans in all of this?

• 10:58Speaker 02

  Well, Sue Carter thinks there is. She says the research on oxytocin and prairie voles is is really kind of a reminder that even something as abstract as love can be found. I mean, at least in some form, in other mammals.

• 11:11Speaker 06

  The human condition does not allow us to give up our evolutionary past. It also doesn't, for some reasons that we truly need to better understand.

• 11:25Speaker 06

  It doesn't allow us to live comfortably without others.

• 11:31Emily Kwong?

  I certainly can't live without others, which, yeah, suggests there's a little perival in all of us.

• 11:38Speaker 02

  Yeah, I mean, at least when it comes to pair bonding.

• 11:40Emily Kwong?

  Jon Hamilton, neuroscience correspondent for the ages. Thank you so much for coming on. And, uh, yeah, deepening my appreciation for what love really is.

• 11:56Emily Kwong?

  If you have a question about those butterflies in your stomach, send us an email at [email protected]. Today's episode was produced by Thomas Lu. It was edited by Gabriel Spitzer and Gisele Grayson and fact checked by Anil Oza. The audio engineer was Josh Newell.

• 12:15Emily Kwong?

  I'm Emily Kwong. Happy Valentine's Day, everyone.