Short Wave - Mix Up LOVE, And You Get V-O-L-E

Episode Date: February 14, 2023

You may have heard of the "love hormone," or oxytocin. But you may not know that scientists have relied on cuddly rodents like the prairie vole to help us understand how this protein works in our brains.Voles are stocky, mouse-like little mammals that range over most of North America. One species in particular, the prairie vole, is known for its fidelity: Prairie voles pair-bond and mate for life. And so, for years, scientists have known that oxytocin is important in facilitating the feeling of love in both humans and voles. However, a new study suggests love can prevail even without the "love hormone" – at least among prairie voles.On today's episode, NPR's science correspondent Jon Hamilton tells Short Wave co-host Emily Kwong how prairie voles, once again, are helping us understand and appreciate something as abstract as love. Struck by cupid's arrow and wondering what's love got to do, go to do with it? Email us at [e-mail]. You can follow Short Wave on Twitter @NPRShortWave.See 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

You're listening to Shortwave from NPR. Hey, shortwavers. Emily Kwong here. It's Valentine's Day. So, seems like the perfect time to take a deep dive into the neuroscience of Lerve. Specifically, rodent love. I'm here with John Hamilton, NPR's own expert on Mureen Romance. Hello, John.

Hi, Emily, and way too casually drop that AP vocabulary word. Respect. Thank you, thank you. Thank you. 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. Which rodent are we talking about? 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.

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. But how do you even know a prairie vole is in love? 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 vol couples also co-parent, they share a nest. And they spend lots of quality time. snuggled up with their life partner. Way to be, voles. 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 Vols. 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 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. I know what this is. This is just a cuddle puddle. But I guess in the case of voles, it's a huddle puddle. It's very sweet.

And I got to say, it's a little bit like some human couples, I have known. Yes. And that is probably why Prairie Vols get a lot of attention from researchers like Dave. 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. Right, the neuroscience of love. Exactly. So decades ago, Prairie Vols helped scientists show the importance of this protein in the brain called oxytocin.

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. I've heard it referred to as the potion of devotion on this very show. All of that. But there is a new study out that suggests love can prevail even without oxytocin, at least in prairie vols. Today on the show, love oxytocin and some rodent role models. John, can we call it the Voluntine special? Pretty sure you just did.

Okay, 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. at voles? I've never even heard of a vol. Okay. 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. 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 Vols. Her name is Sue Carter and she's on the faculty at both the University of Virginia and Indiana University. 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. So they're scrolling through Vol-Tinder, looking for love.

Swipe left or swipe right, you know, man. When they do, where does oxytocin come in? Well, so back in the 80s and 90s, Sue Carter helped show that oxytocin levels rise when a prairie vole meets that special someone. She and others did these lab experiments showing that if you give a prairie vole extra oxytocin, it increases their tendency to pair bond. But if you give a drug that blocks oxytocin, they won't parabond at all. And oxytocin levels, by the way, also seem to predict a lot of human pair bonding behavior.

Well, decades of research sounds like a slam dunk to me. Oxytocin really is the love hormone. Right. That is the conventional wisdom in popular culture and everything. It's even a Billy Eilish song called Oxytocin. Key lyric, you know I need you for the oxytocin. It's an expecting Billy to come in. My kids told me about her.

Oh, good. Yes. I'm glad that you're up on the latest. A totally reliable source. And speaking of scientists, you know that scientist, Dave Manoli? Yeah. The one who was talking about how Prairie Vol couples like the huddle. He was a total believer in the love hormone idea until he wasn't, at least not so much.

So what happened? What happened was Dave was part of this team at UCSF and Stanford that did an experiment with Prairie Vols. It was published last month. in the journal, Neuron. 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. And what did that do?

The idea here was that they were going to create baby voles whose cells wouldn't respond to the love hormone. You know, they would neutralize the effects of oxytocin. Got it. 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. 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 formed partner preferences perfectly like wild type. And, I mean, we were shocked because that was really, really not what we expected.

Yeah, I mean, it sounds like a complete. Shock, like that they were able to form a paribond without oxytocin, love without the love hormone. How is that possible? Well, to be precise here, we're talking about love without the love hormone receptor. Right. So, you know, the molecule 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 roll.

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 Vols really can't survive without paribonning. So they've evolved these redundant systems to produce that behavior. Because of evolution, the parts of the brain and the circuitry that are responsible for parabond 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 that one entry point. I'm so intrigued by one through eight. Do scientists know what these other love potions are?

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. We thought we would disrupt it. But remarkably, the Prairie Bowl wasn't really buying that.

Wasn't going to allow us to disrupt it just by taking away one piece. Love finds away. At least Vol Love did in this case. John, is there a life lesson for humans in all of this? Well, Sue Carter thinks there is. She says the research on oxytocin and prairie voles 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. 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. And it doesn't allow us to live comfortably without others.

I certainly can't live without others, which, yeah, suggests there's a little prairie vole in all of us. Yeah, I mean, at least when it comes to pair bonding. And speaking of that, Emily, I have heard that there might be a little pair bonding in your life. Are you talking about my upcoming nuptials, John Hamilton? I might be. I just want to ask a few questions. Specifically, you're intended. and his similarities with a prairie vole.

Like a prairie vole, I would describe my intended as also fluffy and adorable and really down for a huddle puddle. All you need to know, Emily. John Hamilton, neuroscience correspondent for the ages. Thank you so much for coming on. And, yeah, deepening my appreciation for what love really is. If you have a question about those butterflies in your stomach, send us a email at shortwave at npr.org. Today's episode was produced by Thomas Liu. It was edited by Gabriel Spitzer and Giselle Grayson and fact-checked by Anil Oza. The audio engineer was Josh Newell.

Rebecca Ramirez is our supervising producer. Brendan Crump is our podcast coordinator. Our senior director of programming is Beth Donovan and the senior vice president of programming is Anya Grundman. I'm Emily Kwong. Happy Valentine's Day, everyone. Where to stop or stop.