Lessons in Love From Voles
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Hey, short wavers. Emily Kwong here. It's Valentine's Day. So, seems like the perfect time to take a deep dive into the neuroscience of love. Specifically, rodent love. I'm here with John Hamilton, NPR's own expert on murine romance. Hello, John. Hi, Emily. And way too casually dropped 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. A

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 vole couples also co-parent. They share a nest. Hmm.

And they spend lots of quality time snuggled up with their life partner. Way to be, Vols. 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. 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. 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 voles 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. Yeah. 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. Ah, yeah. Yes, it plays a big role in pair bonding in both Prairie Vols 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 voles. Today on the show, love, oxytocin, and some rodent role models. John, can we call it the Volentine special? Pretty sure you just did. ♪

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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. OK, so here's 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. Right.

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. 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 Vole 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 pair bond 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. 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. I wasn't expecting Billie to come in. My kids told me about her. Oh, good. Yes. I'm glad that you're up there.

On the latest. Yeah. A totally reliable source. Uh-huh. And speaking of scientists, you know that scientist Dave Manoli? Yeah. The one who was talking about how prairie vole couples like to huddle? He was a total believer in the love hormone idea. Until he wasn't. At least not so much. So what?

What happened was Dave was part of this team at UCSF and 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 receptors.

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 IVF.

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 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. Yeah. I mean, 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? 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 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. 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 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 vole wasn't really buying that. It wasn't going to allow us to disrupt it just by taking away one piece. Love finds a way! At least, vole love did in this case. John, is

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,

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. 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 an 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. I'm Emily Kwong. Happy Valentine's Day, everyone. I feel it in my heart.

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