Friday Weird Science: Hyposexual, Hypersexual, and Oxytocin

Dec 04 2009 Published by under Friday Weird Science

Oh, you all thought oxytocin posts were DONE!? BY NO MEANS. For oxytocin lends itself to the truly weird science, and this one simply could not be ignored. In addition, Sci is compelled to blog this paper out of sympathy and understanding for the poor little grad student (or possibly the tech) who WITNESSED this entire experiment, on a weekly basis, for I don't know how long. Oh you devoted servant of science, Sci takes her hat off to you this day.
...moment of silence... Pattij, et al. "Individual differences in male rat ejaculatory behavior: searching for models to study ejaculation disorders." European Journal of Neuroscience, 2005.
We'll get to what the poor student did in a minute.
So what, might you think, is the biggest problem in sexual dysfunction these days? From the abundance of couples in matching bathtubs and various other really awful commercials for Cialis and Viagra, etc, you'd really think it was erectile dysfunction. But in fact, there is ANOTHER sexual disorder that is possibly more common, and which has just as big of an impact on a guy's sexual quality of life...
(Before you go below the fold, things possibly NSFW, blah de blah, it's Friday, you should know this by now.)

(I once ate a grape and I...)
That's right, lifelong premature ejaculation is considered one of the most common, if not THE most common sexual disorder. While some people believe that this results from psychological issues (a self-learned behavior during your first hurried sexual encounters as a teenager), many scientists are coming to believe that premature and delayed ejaculation are just two ends of a big bell-shaped distribution of ejaculation latency in humans.
(Interesting side note, did you know that they did a study where they timed men in intravaginal ejaculation latency, and the result was 5.4 minutes on average?! I really hope they had a positive skew...and Sci NEEDS to blog that week, kids, next week!)
The biological explanation for premature ejaculation is backed up by the fact that you can treat premature ejaculation with SSRIs (where normally the decreased sexual function in response to an SSRI, a popular type of antidepressant drug, if considered a nasty side effect, there's a use for just about every side effect if you put your mind to it), though of course the possible placebo effects of the treatment shouldn't be underestimated either.
So the big question is how to really get apart whether premature ejaculation is a biological phenomenon, or a psychological phenomenon (which could, of course, have a biological basis). And one way to do this is to attempt to change ejaculation latency in animals, like rats. Unfortunately, when people do studies to change ejaculation latency, they always take care of pick rats that display "normal" ejaculatory behavior. But not all rats are normal. There are differences in ejaculation latency between experienced and inexperienced rats, as well as differences in hormone levels. One of the hormones most involved with ejaculation in males and females? Oxytocin! So for this study, the scientists wanted to look at a full population of rats, determine just what kind of ejaculation latency was "normal", and see how this correlated with oxytocin levels in the rats' brains.
And here's where we take a moment to think about the poor grad student or lab tech who, in a huge sacrifice to science, took a whole bunch of rats, every week, and watched them mate. Every week. Watching rats mate. With a stopwatch (or probably several) recording how long it took males to mount a female, how many times he did it, when he finally ejaculated, and how frequently he ejaculated during a 30 minute session. Sci wonders a little how they could tell, by the number of cigarettes the rat smoked during the session?
Yeah. I wouldn't want to be them. Though I bet they had a GREAT time explaining their research in bars.
Based on the many, many weeks (apparently rats receiving six training sessions and then were tested, so that's seven weeks) of sexual activity, the rats were grouped into three groups, sluggish ejaculators (0-1 total during the session), normal ejaculators (1-3 total), and rapid ejaculators (more than 3).
Bring on the graphs!

You can see above the ejaculation numbers during a session for all rats over all the experiments performed. Interestingly, the curve fit has a rightward skew, with relatively few really high ejaculators, though this could be due to some rats maybe not habituating to the environment well and thus not performing as well.
To show you the other data, Sci's going to have to graph. Sigh...I graph because I love, I graph because I love...the things I do for science...
pattij 2005-2.png
So what Sci has graphed for you there is the mount frequency, or the number of times during a sexual session that a male mounted a female. You can see that the sluggish ejaculators mounts far more than normal or rapid ejaculators, but that's probably just a function of how long it took them (or possibly a measure of their sheer persistence). So we get to this graph:
pattij 2005-3.png
Here you can see the ejaculation latency for the rats, and clearly there's a pretty big difference. And Sci has to hand it to these scientists. That's 12 rats, and small error bars, which is something for behavioral measures. Excellent job habituating, peeps!
So what is the cause for some rats being slow and other rats being fast? It could be a matter of penile sensitivity, as human men who suffer from premature ejaculation are known to be more sensitive. But it could ALSO be oxytocin! The scientists point that oxytocin-containing neurons in the hypothalamus showed more activation in rapidly-ejaculating rats than in sluggish rats, as you can see below.
pattij 2005-4.png
So what did the scientists conclude from this? First, they concluded that "premature" ejaculation is probably just the far end of a bell curve in rats, and this may possibly be the same in humans, no psychological issues involved. They also suggest that rapid ejaculators may have higher oxytocin neuronal activity, which could have something to do with their impressive abilities. So who knows, perhaps carefully applied oxytocin antagonists (you wouldn't want to use too much, and you'd definitely want to watch for side effects) could save some people some major embarrassment in the future, and maybe oxytocin agonists could help out those who...take a little longer.
"You say I'm premature, I just call it ecstasy..."
Pattij T, de Jong TR, Uitterdijk A, Waldinger MD, Veening JG, Cools AR, van der Graaf PH, & Olivier B (2005). Individual differences in male rat ejaculatory behaviour: searching for models to study ejaculation disorders. The European journal of neuroscience, 22 (3), 724-34 PMID: 16101754

11 responses so far

  • becca says:

    unintelligent design. the bond-y males are all jackrabbits.

  • Dave Dell says:

    It brings to mind the old (tied for first place as most sexist) joke:
    "Why do men achieve orgasm faster than women?"
    "Who cares?"

  • DD says:

    Is there a demonstrated correlation between premature ejaculation and premature births? Maybe even causation? Got any graphics on that, perchance?

  • James Dean says:

    Oh thank god... I thought you were going to say that the grad students were made to jack off the rats.
    Well this definitely makes me feel a lot better about my grad program.

  • Escuerd says:

    Since you asked, I know you can tell with mice by the way they suddenly become tense and still. It lasts about 20 seconds and is hard to miss. I imagine something similar is true with rats.
    Having spent an inordinate amount of time watching mice ejaculate, I'm not so sure I want to consider neuroscience as a career anymore. 😉

  • dh says:

    Speaking about rats, dopamine and weird science, you might want to check out Sapolsky's description of the amazing discoveries been made about how the Toxo parasite rewires rat's amygdalas so they are attracted rather than repelled by cat urine...I like the line about the the tiny bit of protoplasm knowing more than 25,000 neuroscientists...
    Also, speaking of Oxytocin and Dopamine in humans check out Marnia Robinson's excellent new book "Cupid's Poisoned Arrow". and her web site on these topics and her Psycholgy Today blog.
    She has a lot to say about porn addiction, and a clear description of the Coolidge Effect,
    Thanks Tiger, for giving us a basic biology lesson once again..

  • lol, I love that video! And now I'm posed in an awkward stance because I...

  • Associated & Marriage Counsellors Sydney CBD says:

    Interesting take on it. We still find that reducing stimulation in males generally including reducing their level of anxiety gives a predictable efcet in reducing premature ejaculation. It seems that the cause is only half the equation and that behavioural and cognitive techniques can still have an important role before we find a more direct agent.
    Associated & Marriage Counsellors Sydney CBD

  • Bangnal says:

    can any one comment on how many times a day ejaculation is safe . like if some one can ejaculate 4-5 times day for like 3-4 months daily is it safe
    what are the drawback of heavy Mastibulation ejaculation in Human Man ...
    thanks in advance

  • Dylan says:

    Holy crap I know the second author! She was a post-doc and one of my advisers at a research internship this past summer. I know it might seem weird to be excited about that, but I am.

  • [...] always makes a lot of press. It plays roles in reproduction and mating behavior, social bonding, behavior related to morality. To call it "the love hormone" as [...]

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