Keeping sperm from ejaculation may provide the key to creating a birth control drug for men, according to a new mouse study, Fox News reports.

The research is far from translating to a pill that human males could pop to keep from making babies; to reach that stage, any drug would have to undergo years of testing for safety and effectiveness. Nevertheless, the study offers hope for a new method of birth control for men, the researchers said.

Compared with female birth control, the male version is a biological challenge.  

Sperm are made in the testes, and stored in a tightly coiled tube called the epididymis, inside the testicles. When a man ejaculates, smooth muscle propels the sperm out of the epididymis, through a tube called the vas deferens, into the urethra and out of the body. Receptors on the muscles receive hormonal signals that instruct the muscles to contract, sending the sperm on its way.

Previous attempts to block these receptors had only decreased male fertility.

In the new study, the researchers bred mice that lacked both 1A-adrenoceptors and P2X1-purinoceptors. They found that female mice without the receptors could still reproduce as normal. Male mice pursued females and mated with them as usual, but they never sired babies.

In fact, drugs that block 1A-adrenoceptors are already on the market to treat benign prostate enlargement.

A drug that blocks the P2X1-purinoceptor would still need to be developed and tested.

Of course, even if a combination 1A-adrenoceptor and P2X1-purinoceptorblocking drug were developed, men would have to be on board, psychologically. The anti- 1A-adrenoceptor drugs already on the market have the side effect of the occasional orgasm without ejaculation.