Effect Measure

Along came a spider . . .

Some stories just force themselves on you. I know I’m not special in this regard, since this story was sent by reader and frequent commenter MRK with the note, “Couldn’t resist this one. . . .” Maybe the fact we are both males has something to do with it. Mrs. R. would certainly think so. Anyway, this is The Right Moment (insincere apologies to Cialis’s ad agency):

A Brazilian spider delivers more than a painful bite that sends most victims to the hospital.

Its venom stimulates an hours-long erection. Now scientists have figured out the chemical that seems to be responsible for the penis boost.

In Brazil, emergency room staff can immediately spot the victims of a bite from the Brazilian wandering spider (Phoneutria nigriventer).

Patients not only experience overall pain and an increase in blood pressure, they also sport an uncomfortable erection.(Fox News)

Penis boost? “Sporting an uncomfortable erection”? Hmmm. Well, it’s Fox News, guardian of public morals, so I guess it’s OK. There is a more serious scientific and medical issue here, leaving aside (as hard as this might be [sorry]) the diction with its implied naughtiness. If we can find the element in the spider venom causing the inappropriate erections (when the time “isn’t right”), we might learn something about the biology of reproduction and maybe even other matters, like blood pressure control. Such are the strange ways of scientific discovery.

In this case scientists at the Medical College of Georgia identified a small peptide they called Tx2-6. The test bed (sorry, again) involved experiments with rats, “stimulated to begin an erection.” The experimental set-up is a toe curler (at least for males):

A tiny needle-like device inserted into each rat’s penis measured the pressure change, which corresponds with the increase in blood flow to the blood vessels inside the penis.

Ouch. It’s impressive an erection is possible under those conditions, even if you’re a rat. But as medical students are taught, the most important sex organ is the one between your ears. Even if you’re a rat, stimulated to begin an erection. The long and the short of it is (sorry, a third time) that rats injected with the peptide had increased penis pressure. The increase in pressure was accompanied by an increase in nitric oxide in the corpus cavernosum. Nitric oxide is a neurotransmitter known to be involved in smooth muscle relaxation important in the mechanism of erection.

The significance of the nitric oxide is clear when the science behind an erection is considered: The brain senses sexual arousal in the body and certain neurons produce nitric oxide, a message telling the body to get started in making an erection.

A cascade of biochemical steps occurs, one of which includes the production of an enzyme dubbed cGMP [cyclic guanosine monophosphate].

This enzyme causes the smooth muscles of the penis’ two cylinders to relax so that blood can rush in and fill up the now expandable tubes. (A human penis can hold about 10 times more blood when erect compared with its non-erect state.)

[Aside for off-color joke: Anatomy professor is quizzing class and asks student sitting in front row and not doing a sufficiently effective job of eye-aversion, “Ms. Jones, what organ of the human body changes size 40 times when stimulated?” Ms. Jones turns beet red, stammers and then falls silent. Her professor replies: “I have just three things to say to you, Ms. Jones. First, you have not studied today’s topic very well. Second, the correct answer is the pupil of the human eye. The third thing is that you are destined for a very big disappointment.”]

After the relaxation of the penile smooth muscle and the localized increase in blood volume, things need to be “turned off” (sorry yet again). The normal mechanism works through PDE-5 [phosphodiesterase type 5] which breaks down cGMP and the penis detumesces. Viagra and Cialis interfere with PDE-5. The spider somehow increases nitric oxide:

Somehow, the toxin ups the amount of nitric oxide, which sort of sets into motion an erection.

The scientists suggest that a combination of a synthetic version of the spider venom with a drug like Viagra would result in a magnified effect.

“So the combination of the two drugs could be even more efficient in patients that don’t respond well to Viagra,” Leite said.

Ask your doctor if a combination of spider venom and Viagra are right for you. If you have an erection lasting longer than four hours, call the Medical College of Georgia.


  1. #1 Victoria
    May 5, 2007


    It would seem that no body wants to touch this one.

  2. #2 revere
    May 5, 2007

    Victoria: Hmmm. Maybe it wasn’t The Right Time.

  3. #3 Victoria
    May 6, 2007


    Did you here the story about General De Gaul’s wife, when she was being interviewed by the American press at the end of WWII?

  4. #4 Melanie
    May 6, 2007


    Do tell. A quick Google turned up nothing.

  5. #5 Victoria
    May 6, 2007

    Mrs De Gaul was being interviewed by an American Press Reporter shortly after the end of World War Two.

    “Madame De Gaul. What is it that you most want out of life now” asked the reporter.

    Madame De Gaul replied “A Penis”.

    “I do beg your pardon Madam De Gaul. What was it that you most wanted out of life now” asked the shocked reporter.

    Madame De Gal replied “A penis of course”.

    “Oh! You mean happiness of course”. said the reporter.

    “What else would I have been talking about” replied Madame De Gaul.

    This was apparently quite a true story.

  6. #6 M. Randolph Kruger
    May 6, 2007

    Well that might be the problem. What would I do with an erection lasting for four hours or more? I can think of a lot of things and mowing the grass aint one of them.

  7. #7 Rob Thompson
    May 6, 2007

    Actually I remember it was David Frost, the skilled Britich TV interviewer who claimed that incident happended during an interview he had with le President and Madame De Gaulle. It was the President who leaned across and corrected his wife by saying “no,no, you mean ‘appiness.”

    David Frost said it was the coup of his TV interviewing career.

  8. #8 Victoria
    May 6, 2007

    Rob T. – Thanks,for the life of me, I just could not remember from whence I gained the info.

    Revere – you have given new meaning to the words – spider bite and spiderman.

  9. #9 mollishka
    May 6, 2007

    Have you seen the movie “Kinsey”? Aside from being a pretty good film, it’s got a great delivery of that particular off-color joke.

  10. #10 revere
    May 6, 2007

    mollishka: No, haven’t seen the movie. I first heard the joke — where else? — in medical school, more than 40 years ago.

  11. #11 sleeve
    May 6, 2007

    Revere, I was wondering…is the nitric oxide-cGMP-PDE5 system for erection the same in women? Of the clitoris, of course, and general enlargement of labia. Or is there a different mechanism?

  12. #12 revere
    May 6, 2007

    sleeve: Yes, apparently. See this.

  13. #13 Jon Singleton
    May 6, 2007

    The word “tumescent” is so wonderfully florid. I can just imagine Dubya casually mentioning to Queen Elizabeth II she looks healthily tumesce…silence, silence…RADIANT at the Washington state dinner on Monday!

  14. #14 sleeve
    May 6, 2007

    Interesting! Thanks. (although, I’m glad I wasn’t the research assistant on that study).

    Also, funny coincidence that the acronym for pelvic nerve electrical stimulation is PNES.

  15. #15 g510
    May 7, 2007

    Great, what the world needs now is another Bigger Better Boners pill.

    What I want to know is, where’s the research on a male contraceptive pill that will shut down sperm production for a month at a time? *That* would be a world-saver. Or if not, then an entactogen (empathy-inducer) that makes males experience what females go through with labor and delivery.

    6.5 billion humans, heading toward 9 billion, will not make it. One way or the other.

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