Oxytocin: Let's hear it for the boys!

Nov 17 2009 Published by under Behavioral Neuro

Sci will be honest. The migraine continues apace. But the oxytocin, it must be blogged. And the migraine medication, it makes Sci loopy! Given what I'll be blogging today, that might not be a bad thing...
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(From the Devil's Panties, which is a super-cute webcomic if you're into geeks like Sci is. I met the artist once and she drew me one of these! Also, Sci would like to note that she does not use paint fumes as migraine medication.)
I've already gone through some of the basics of oxytocin, and the famous effects that oxytocin has on females. But what most general biology and physiology courses don't tell you is the big role that oxytocin plays in MALES. This molecule isn't just for the ladies.
Let's hear it for the boys:

(Nothing says manly men like high kicks)

If you've been following Sci's recent posts on oxytocin, you'll recall that oxytocin is a hormone secreted from the posterior pituitary (but made in the hypothalamus) which has actions all over the body, including but not limited to major roles in birth, lactation, and maternal bonding. But oxytocin plays big roles in men, too. The biggest roles that it plays in men is in social awareness, social bonding, trust, and possibly empathy, which is stuff that Sci is going to have to go into in her next post, because they are in both men and women, and they are in the public awareness so much that I think they need a post of their own.
So what does oxytocin do in men? Well, for a long time, people didn't think it did much. They thought it was essential to pair bonding in females due to studies in female prairie voles, but those same studies found that vasopressin was the necessary molecule for pair bonding in male voles, not oxytocin. However, it's now known that oxytocin is very important for things like bonding in male HUMANS, and the voles can go screw. And oxytocin is also important for one thing that men find to be very, very, very important.
Bring on the sex.
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(I think she's gonna get squished)
It turns out that oxytocin in men is important in sexual arousal. During sexual arousal, large amounts of oxytocin and dopamine (which I've written about before) are released. It is believed that oxytocin contributes to the perception of sexual arousal, while dopamine may be correlated with the positive feelings associated with sexual arousal. There are lots of receptors for oxytocin present in the penis, particularly in the corpus cavernosa, the long tubes that fill with blood during an erection.
And the sexual arousal induced by oxytocin is some potent stuff. Rats given oxytocin get both an erection and an increase in dopamine in an area of the brain called the nucleus accumbens, an area associated with the "motivational properties of stimuli". It's the area that gets hit hard when people (or rats) take cocaine, and the area that hits up whenever anything that feels really good goes on. And what feels better than sex? It appears that oxytocin feels very good indeed.
And oxytocin is not just big in sexual arousal, it is also very important in orgasm (this is true for both women and men, as you may have seen in previous posts). For male orgasm, oxytocin is very important in the muscle contractions that occur during orgasm, possibly contracting the epididymis (the tube connecting the testes to the vas deferens, and hence to the out-route). While oxytocin probably isn't the only thing in charge of male ejaculation, some case studies have found it to be effective in restoring problems with ejaculation (which Sci imagines must be a very frustrating problem indeed).
And oxytocin may have a third role to play. It is very possible that oxytocin plays a role in the aftermath of sex as well, in the role of "postorgasmic penile detumescence". The English translation of that is what we like to call a "soft-off" (I would link to Urban Dictionary there, except that their "examples" are always just...really immature. Even for Sci).
Now you might sit there and think "wait, hard-ons AND soft-offs?" How does THAT work? Well the current hypothesis is that estrogen (that's right, estrogen) plays a role in this, causing certain areas of the penis (like the corpus cavernosa and the arteries leading in) to be sensitive to the muscle-contracting effects of oxytocin during arousal, and other areas (like the veins leading out) to be more sensitive to the effects of oxytocin after the deed is done. That's some crazy awesome science right there.
So that's the main physical effect of oxytocin in men (and one of those studies I cited MIGHT be this Friday's Weird Science. Something about huffing oxytocin and masturbation...). Next up, the effects of oxytocin on the soft grey matter, the bonding, trust, and other stuff that give oxytocin it's reputation as being the "love molecule". Yeah, whatevs. We'll get to that.

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