The Scicurious Brain

The Scicurious Brain

The Good, Bad, and Weird in Physiology and Neuroscience

When is comfort most comforting? When you've got a specific Oxytocin gene!


Hi. In a few minutes I'd like you to stand up and give a short public speech to a judgmental group of people. The speech will be about the current national and international effects of Marbury v Madison, with particular focus on violations of interstate commerce. You have 15 minutes to prepare and the speech will have to be 15 minutes long. I hope you've done your research.

Nervous yet? If you are, you're not alone. Fear of public speaking (glossophobia, or just stage fright) is one of the most common fears in the Western world. But it's ok. We're going to have you sit with your loved one, who will be able to give you encouragement as you prepare.

Do you feel a little bit better? I bet you do. But do you really, actually feel better? Does your body react to stress differently when you've got a loved one with you to help you out?

It turns out that it might. At least, if you've got a specific kind of oxytocin receptor gene.

(Oxytocin. Image via Wikipedia)

(And don't worry, I was kidding about the speech)

Chen et al. "Common oxytocin receptor gene (OXTR) polymorphism and social support interact to reduce stress in humans" PNAS, 2011.

Oxytocin gets a lot of press. And well it should. Recent findings on oxytocin have shown effects on trust, on generosity, on behaviors in austistic children even. Not to mention all the effects that oxytocin has on parental bonding and on your sex life. While many of these studies have looked at levels of circulating oxytocin, or the effects of giving oxytocin (usually as a nasal spray) on behavior, people have recently started to look at the other side of oxytocin: the oxytocin receptor.

You see, any chemical in the brain (or anywhere else in the body for that matter) which is floating around, is only as good as the receptor it binds to. Which receptors (proteins in cell membranes or in cytoplasm that bind other molecules) it binds to, where those receptors are, how they react, and what they connect to, can really make a world of difference (not to mention fascinating scientists for a lifetime or three). And little changes in receptors, single nucleotide changes in the genes that code for receptor proteins (we call these gene changes single nucleotide polymorphisms or SNPs, which is usually pronounced "snip"), can change the proteins within the genes, and can change how well the receptors work, where they go, and what they do.

And so when you've got a receptor for oxytocin, and when you've got a SNP in it in humans, of course you want to know what it's going to do and whether it's going to change how people act.

In this case, we are looking at the polymorphism rs53576 (don't you wish we could name them all something interesting and memorable, like Pauline? Sigh, precision above all I guess), which turns a single nucleotide in the oxytocin receptor gene from a G to an A (remember there are four possible nucleotides in DNA: A, G, C, and T). We don't know yet how exactly this can change the oxytocin receptor's shape, whether it makes oxytocin bind less well, or what. What we do know is that it's relatively common in the human population. So this study wanted to see what effect it had on how people respond to stress in the presence of a loved one.

The idea is basically this: oxytocin has a lot to do with social bonding and social behavior. Social bonding is thought to help us during times of stress. If the oxytocin receptor SNP is function, then people with one SNP (say, GG) might do better on measures of anxiety when they have their social bonds around, benefiting more from the social behavior.

And this is where the public speaking coming in. The authors of the study took 173 guys (there might be major sex effects here, oxytocin is known to have very different effects in men and women, so it's best to study one sex at a time here), and told them they'd be giving a speech shortly. They genotyped all of them to see whether, at this SNP, they were GG, GA, or AA (remember you have two copies of each gene so that will vary). They then left half of each group to prepare alone, while the other half got to prepare with a female friend or female loved one (I wonder if the results would be different with male friends, but I guess that's for another study). Then, they took levels of cortisol (a stress hormone) right before the public speaking even and right after.

What you can see here are the blood cortisol levels immediately before and after the public speaking event (the bit in grey). Obviously no one liked public speaking very much, the cortisol levels went up significantly in all groups. But you can see that those people with a G in their genotypes (one or two) had a smaller increase in cortisol...but ONLY when they had the social support of their lady friends. The AA group of guys, on the other hand, had cortisol levels that were just as high, regardless of social support.

So that's cortisol levels, but what about the stress that people were actually feeling?

It turns out that here it made no difference. People were just as nervous with or without the social support. This means that even though the GG/GA guys were less physically stressed, it didn't really change how they FELT about it.

This may show that the oxytocin receptor gene variant controls how we PHYSICALLY response to stress in the presence or absence of social support. But remember, correlation is not causation and there are a lot of other factors to consider. First is, of course, whether a person even WANTS the social support around. Overt encouragement in the face of stress varies a great deal culturally, and so not all cultures may take this the same way (though all the guys in this study were native Germans). But there are more questions. Did these people differ in how much social support they received in the past? Did their upbringings, even within the culture, vary in terms of social support (probably)? And what does it MEAN that, even though the guys showed differences in stress hormones in the presence of social support, that they all rated it the same way?

Not to mention all the questions this raises about whether exogenous oxytocin helps with this, how the polymorphism affects oxytocin signaling in the first place, and how growing up with one version of this gene could affect responses to stress. And of course, is it the same with male friends? What about in women? What about with family members? What about with other kinds of stress? Are these effects beneficial?

This is a cool study, and provides some very interesting clues as to how changes in oxytocin receptors may affect stress responses, but it's clear we're only at the very beginning of understanding how oxytocin really works here. No sure cure for your public speaking fears yet. Ah science, always raising more questions than it answers!

The views expressed are those of the author and are not necessarily those of Scientific American.

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