New Approach to Male Contraceptive Shows Promise in Mice

By Breanna Draxler | December 3, 2013 12:43 pm

sperm and egg

One tiny sperm is enough to make a baby, so coming up with a male contraceptive is tricky. It has to be 100 percent effective—which is just what researchers have now achieved in mice.

Most previous attempts at making a male contraceptive have aimed at producing dysfunctional sperm, but the results have been mixed, and often have unpleasant side effects like a reduced sex drive or permanent infertility. These outcomes, for most men, are unacceptable. So this time researchers have taken a different approach. Instead of interfering with sperm production, they decided to block sperm transportation.

Stopping Up Sperm

Scientists deleted the genes in male mice that code for production of two particular proteins. These proteins, α1A-adrenergic and P2X1-purinoceptor, are receptors that trigger the contraction of the muscles surrounding the vas deferens, causing the sperm to move from the testes into the penis during ejaculation. Without these two proteins, the muscles didn’t contract and the sperm didn’t leave the testes. As a result, the mice shot blanks.

The study reported the male mice were 100 percent infertile without losing any of their sex drive or ability to perform. Plus, the sperm themselves were unaffected. Researchers extracted sperm from the mice’s testes after the study and found they could fertilize eggs in a petri dish just fine.

The Pill for Men

Since these mice were genetically modified, their infertility was permanent. But a duo of drugs could reversibly produce a similar effect in men.

One such drug, an adrenoceptor-blocker, already exists. It is a commonly used treatment for high blood pressure and benign prostate hyperplasia. But the researchers will have to concoct the second drug from scratch, which could take a decade, according to the study published in Proceedings of the National Academy of Sciences yesterday.

In terms of side effects, the mice showed a slight decrease in blood pressure. This is because the proteins, in addition to contracting the vas deferens, also play a role in constricting blood vessels. That means that administering a protein-blocking drug to humans could potentially have side effects on blood pressure and heart rate too. But time and drug testing will tell.

 

 Image credit: koya979/Shutterstock

CATEGORIZED UNDER: Health & Medicine, top posts
MORE ABOUT: sex & reproduction
  • Jennifer Aldoretta

    “Most previous attempts at making a male contraceptive have aimed at producing dysfunctional sperm, but the results have been mixed, and often have unpleasant side effects like a reduced sex drive or permanent infertility. These outcomes, for most men, are unacceptable.”

    Does this frustrate anyone else? Most side effects are deemed unacceptable for men, yet women are simply expected to deal with the same things when given hormonal contraceptives!

    • 01shade10

      I would expect that its related to the fact that men are VERY clear with whats acceptable for them.

    • http://blogs.discovermagazine.com Don Hubin

      It might be worth acknowledging at the outset of any discussion of gender asymmetry with respect to birth control that women have far more birth control options than men. I’m not sure by whom “women are expected to deal with the same things” but if a woman doesn’t like the side effects of hormonal contraceptives, she has alternatives.

      Second, while some formulations of hormonal contraceptives decrease libido in some women, this can often be avoided by using different hormonal methods. And I’ve never heard that permanent infertility is a common side effect of any female hormonal contraceptive. If it were, I would assume that drug companies would consider this to be an unacceptable side-effect for most women. It’s not clear to me, then, that “women are simply expected to deal with *the same* things.”

      Finally, for a couple, the “unpleasant side effects” of “reduced sex drive or permanent infertility” are not experienced only by one partner. Many women would prefer that the birth control method used by the men that they love not make their partner permanently infertile or cause him to lose his sex drive. (And vice versa, of course.) And this is not just because they love their partner. It’s also because they want their partner to have a sex drive directed toward them and they might want to have children with their partner.

      Really, it’s just not the case that everything is a “boys vs. girls” issue.

      • Jennifer Aldoretta

        While it’s certainly true that women have more birth control options than men (I’m not saying that’s at all fair), it’s important to note that a majority of those options are, in fact, hormonal. I’m not trying to turn this into a gender discussion just for the sake of saying something “feminist”, so perhaps I should have provided a more sound argument than I did in my first comment. All of your points and criticisms are incredibly valid.

        The big issue I have here is that it has been 60+ years since a female “pill” was put on the market, and while many of the original side effects have been decreased by decreasing dosage, nobody is really attempting to make strides by offering a non-hormonal option for women that is just as effective as hormonal methods. The fact that a male pill has *still* yet to be released and that doctors like the one quoted above seem to attribute that to the “side effects” of hormones just feels unacceptable. There are countless side effects that women endure or are at risk of experiencing while on hormonal contraceptives (loss of libido, ectopic pregnancy, stroke, heart attack, blood clots, depression, anxiety, hair loss, headaches, etc.), which also effect more than just the female partner. I can speak for many women when I say that, oftentimes, doctors dismiss concerns that women bring up about these side effects and simply tell them to stick with it or wait it out.

        Infertility in men is absolutely an unacceptable side effect, but one could also argue that a stroke, blood clot, or heart attack that results in a woman’s death is also an unacceptable side effect. Or that severe depression, anxiety, hair loss, or mood swings outweigh the benefits (especially since all of these things can have a huge impact on the relationship, which I believe was part of your point).

        My point is, why are severe side effects “okay” in a female-only method but unacceptable for a male-only method? The increased care that is being taken with the development of a male option is great, and I think it’s the right choice. But I also think that women deserve that same standard of care when researchers are developing a method for us, and that seems to be missing (or at least it wasn’t considered when the pill was first developed).

        If the only difference is the *when* in the development of these drugs, then I think now is also a great time to work on a more suitable, highly-effective option for women that does not have the same risks of serious side effects. I think it’s time to move beyond hormones (for men and women), and development of a male pill that’s non-hormonal just goes to show that it’s a conversation also worth having about female methods.

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