Friday Weird Science: Oxytocin in your Cavernosa

This post brought to you by Ben and Jerry’s Dublin Mudslide Ice Cream. Because the Twitter people are like little devils on my shoulder, making me eat the cake…
dublin mudslide.jpg
So Sci was going to do her final oxytocin post on another study in humans for oxytocin levels during male masturbation, but you know, you've seen one, you've seen them all. I know that they were looking at slightly different things, but…well…it all looked the same: oxytocin measured while a guy is in a room with some porn, measure some other stuff as well, look at the correlations. So Sci started digging around for something a little more unusual.
And when Sci saw this one, her little eyes brightened, and she said "oooooh! THAT ONE!"' much to the surprise of the nice evening janitorial lady in the lab. Because if you thought the LAST Friday Weird Science was one that you wouldn’t want to volunteer for…
…how would you like a butterfly needle in your penis? What, that’s not stimulating?! Uckert et al. “Oxytocin plasma levels in the systemic and cavernous blood of healthy males during different penile conditions” World Journal of Urology, 2003.
For those not in the know, a butterfly needle looks like this:
(Insert into penis pointy end first)
Yadda yadda. Photos below NSFW, yadda yadda. It’s Friday Weird Science, not like there’s going to be puppies and kittens here.

puppies kittens.JPG
(Ok, I lied, just the one!)
So anyway, things you’re going to need to know for this post:
1) Oxytocin. As you might know from my series of posts on the topic, oxytocin is a hormone involved in a lot of things in the body, including parts of birth and lactation, emotional aspects like trust and bonding, and of course, sexual arousal and orgasm.
2) The Corpus Cavernosa: If you’ve read my previous posts on this topic (and oh, there are many at this point), you will know that you there are TWO corpus cavernosa (latin for “cave body”) which are long tubes (well, I suppose they’re long, depending) that run along the male urethra inside the penis. Here:
tunica albuginea1.jpeg
The corpus cavernosa is the pale space, and the dark line is the tunica that surrounds it. During sexual arousal, the corpus cavernosa, which is made of smooth muscle and has a spongy inside, fills with blood, making it turgid and tumescent.
Now, the tumescence (or lack thereof) of the penis is controlled by several different factors, including neurotransmission and hormonal effects. But this study set out to explore the role of oxytocin in the penis in particular during an erection, in an effort to see if oxytocin levels differed locally as opposed to in the rest of the bloodstream.
So what did they do? Got a bunch of guys (I REALLY hope they paid them), and inserted two needles, one into the arm, and one into the penis, directly into the corpus cavernosa. Then told them to go at it, using whatever erotic stimuli (visual or physical, though I imagine you had to be very careful) necessary. Guaranteed to get you in the mood. Hit it, boys!
Two subjects actually ended up dropping out due to persistent pain and dislodging the needle when they got an erection, and two more never made it to the erection part (unable to get it in front of a bunch of scientists. That is both not surprising and probably extremely embarrassing). In those that did make it, however, the scientists observed something interesting. During sexual arousal and the formation of an erection, oxytocin levels went up in both the systemic blood and the cavernosa blood. But as the penis reached full rigidity, oxytocin continued to rise in the penis, but flattened off in the systemic circulation. Then, during the soft-off, blood levels of oxytocin the penis dropped (as expected), but rose AGAIN in the systemic circulation. Oxytocin is known to contract smooth muscle, which is how it is thought to control erections in men, and so the time course in the penis reflects the smooth muscle contraction very well. You can see the results here:
oxytocin corpus cavernosa.png
Sci was actually more than a little surprised by these findings. I thought that it would not be possible to have blood levels of oxytocin (or anything, for that matter) higher in one area of the body than another, unless of course it is RIGHT after release or injection or something. They suggest that the changes present during detumescence (the soft-off) are due to changes in penile hemodynamics, less blood flow in, less oxytocin in, and the opposite might account for the changes during tumescence and rigidity (more flow in, more oxytocin in, and less flow out meaning the oxytocin would stay). This makes a certain amount of sense, but I can’t help wondering if there’s another possible mechanism (perhaps inhibited breakdown in the area compared to the rest of the systemic circulation? A study for another time, perhaps).
In fact, there are a LOT of other studies for oxytocin that Sci would like to see. For example, she’d like to see studies done with oxytocin and actual social encounters, say, with colleagues that you have to work with. Does a burst of oxytocin make you work more productively or cooperatively with others? Also, I’d like to see effects and changes in oxytocin during actual sex in males and females. Finally, it would be interesting to see the effects of oxytocin on positive memory encoding for familiar faces (friends and family) vs unfamiliar faces, and positive vs negative relationships.
For now, though, we will leave oxytocin. But fear not! Sci has several other weird oxytocin papers that she has found, and they may come to light on future Fridays. Nothing says “future big pharmaceutical moneymaker” quite like cures for premature ejaculation.
Uckert S, Becker AJ, Ness BO, Stief CG, Scheller F, Knapp WH, & Jonas U (2003). Oxytocin plasma levels in the systemic and cavernous blood of healthy males during different penile conditions. World journal of urology, 20 (6), 323-6 PMID: 12811490

9 Responses

  1. jeez, I thought you were talking about oxytocin in nasal conchae! Oops!

  2. Needles here, needles there… Sounds like some kind of acupuncture? Anyway, great respect for those unnamed men, who did so much in the name of science.
    As for local oxytocin, it has to be something with breakdown involved, as it is only produced in the brain. Or maybe penis is capable of some synthesis on its own? Some say men use it for thinking, so there’s an analogy here…
    Great post, Sci – waiting for more, as usual!

  3. *still squirming in discomfort after looking at the picture of the needle

  4. “Soft-off”. Pure, total poetry.

  5. Hard-on, soft-off. Why does this make me think of the old ‘clapper’ commercials? And wouldn’t that be cool?

  6. Corpora cavernosa.
    Thinking about needles being stuck in my corpora cavernosa made me wince and cross my legs tightly. I don’t even have corpora cavernosa!
    With that said, oxytocin is known to be released during female orgasm. So I am surprised that it would be released prior to orgasm in males; I figured the processes would be homologous. Or is there evidence that there is substantial oxytocin release in females, too, prior to orgasm.
    As an undergrad, endocrinology was always my favorite topic. I loved reading papers on oxytocin in particular. At one point, I pondered the feasibility of using oxytocin (Pitocin?) recreationally (delivered by way of a pump, similar to the ones we use to deliver insulin). It’s an idea I often revisit in my daydreams.

  7. I think there is oxytocin being released before orgasm in both sexes in response to stimuli such as nipple stimulation etc. Only the levels are much lower than during the Big O…
    As for recreational use, a pump should be necessary, as the best things in life come in pulses – that’s the way oxytocin is being released you-know-when.

  8. DD: Thanks! I’d like to hope they read my series for the background…but probably not. SOMEDAY!!!

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: