A male contraceptive could be on the horizon after a discovery of a novel way to block the transport of sperm during ejaculation, Australian researchers say. Lead researchers, Dr. Sab Ventura and Dr. Carl White of the Monash Institute of Pharmaceutical Sciences in Australia and colleagues at the University of Leicester in England said they found complete male infertility could be achieved by blocking two proteins found on the smooth muscle cells that trigger the transport of sperm. The researchers demonstrated the absence of two proteins in mouse models -- alpha 1A-adrenoceptor and P2X1-purinoceptor -- which mediate sperm transport, caused infertility, without effects on long-term sexual behavior or function. The researchers said the knowledge could be applied to the potential development of a contraceptive pill for men. "Previous strategies have focused on hormonal targets or mechanisms that produce dysfunctional sperm incapable of fertilization, but they often interfere with male sexual activity and cause long term irreversible effects on fertility," Ventura said in a statement. "We've shown that simultaneously disrupting the two proteins that control the transport of sperm during ejaculation causes complete male infertility, but without affecting the long-term viability of sperm or the sexual or general health of males. The sperm is effectively there but the muscle is just not receiving the chemical message to move it." Ventura said there was a drug that already targeted one of the two proteins, but they would have to find a chemical and develop a drug to block the second one. "This suggests a therapeutic target for male contraception. The next step is to look at developing an oral male contraceptive drug, which is effective, safe and readily reversible." If successful, it is hoped a male contraceptive pill could be available within 10 years, the researchers said. The findings were published in the journal Proceedings of the National Academy of Science.