Zapping a male's private parts with ultrasound could be one of the most effective and non-invasive forms of contraception.
Experiments conducted by James Tsuruta, from the University of North Carolina, US, have shown they lowered sperm counts in mice, potentially opening the way to reversing fertility in men.
Tsuruta, who led the study, said: "Our non-invasive ultrasound treatment reduced sperm reserves in rats far below levels normally seen in fertile men. Further studies are required to determine how long the contraceptive effect lasts and if it is safe to use multiple times."
The perfect male contraceptive would be cheap, reliable, reversible, long-acting and have few side effects, the journal Reproductive Biology and Endocrinol reports.
Tsuruta's team found that rotating a three megahertz high frequency ultrasound beam around rats' testes wiped out the germ cells that produce sperm. Best results were seen from two sessions lasting 15 minutes with the testes warmed to 37 degrees Celsius, according to the Daily Mail.
A first attempt to use ultrasound as a male contraceptive was reported 40 years ago. Several prostate cancer patients who were due to have their testicles removed underwent the treatment, which resulted in a 'dramatic loss of germ cells'.
"These men reported that the procedure was pain-free, only creating a gentle feeling of warmth," said the study co-authors. However, the idea was not pursued and the equipment used is now outdated and unavailable.