Scientists may be a step closer to developing a new male contraceptive. Scientists from the Monash Institute of Pharmaceutical Sciences found they could block two proteins that trigger sperm transport. The two proteins, α1A-adrenoceptor and P2X1-purinoceptor, tell the smooth muscles lining the male reproductive tract to contract at the right time to move the sperm along. When the two proteins are blocked simultaneously, the muscles do not receive the chemical message to move the sperm down the reproductive tract.
Blocking the two proteins causes temporary and complete infertility, even though the semen still contains active sperm. This approach does not disrupt sexual activity, nor does it cause long-term infertility.
A drug already exists to block one of the proteins but pharmacologists must still develop a drug to block the second protein. This discovery about proteins, combined with a drug to block the second protein, could lay the groundwork for development of a male contraceptive pill.
The information published in Proceedings of the National Academy of Science may someday help scientists develop a contraceptive pill for men. Currently, strategies for a male contraceptive pill focus on hormones or other mechanisms that create dysfunctional sperm. These approaches can sometimes hinder sexual activity or even cause long-term and irreversible effects.
Today, men rely on condoms, withdrawal, outercourse, spermicides, and vasectomy to prevent unwanted pregnancies. These methods are not at all comfortable nor are they altogether reliable – even vasectomy has a failure rate of 11 cases per 1,000 over two years, according to the Centers for Disease Control and Prevention. The typical failure rate for condoms is 18 percent. Spermicides fail about 28 percent of the time.
Using proteins to “switch off” muscles lining the reproductive tract seems to have no failure rate – it provides complete infertility even though the sperm are still alive and intact. This breakthrough in understanding may mean the end of unwanted pregnancies, ineffective contraceptives, and superior comfort during sexual activity.
Source: White, Carl W. "Male contraception via simultaneous knockout of α1A-adrenoceptors and P2X1-purinoceptors in mice " Proceedings of the National Academy of Science Series Volume. December 3 (2013): PNAS. Web. 10 Dec 2013.