Neuronal Basis for Pre-mature Ejaculation?

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 paper…next 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!

pattij 2005-1.png

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

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

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

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