Single shot delivery for long-term contraception

Researchers have developed a nonsurgical method to deliver long-term contraception to both male and female animals with a single shot.

The technique -- so far used only in mice -- holds promise as an alternative to spaying and neutering feral animals.

Dubbed "vectored contraception", the new approach was developed in the lab of Bruce Hay, professor of biology and biological engineering at California Institute of Technology in the US.

The scientists used a harmless virus called adeno-associated virus (AAV) to deliver a gene that directs muscle cells to produce an antibody that neutralizes gonadotropin-releasing hormone (GnRH) in mice.

GnRH is what the researchers refer to as a "master regulator of reproduction" in vertebrates - it stimulates the release of two hormones from the pituitary that promote the formation of eggs, sperm, and sex steroids. Without it, an animal is rendered infertile.

"Inhibiting GnRH is an ideal way to inhibit fertility and behaviours caused by sex steroids, such as aggression and territoriality," Hay said.

In the past, other teams have tried neutralising GnRH through vaccination.

However, the loss of fertility that was seen in those cases was often temporary.

In the new study,the researchers saw that the mice were unable to conceive after about two months, and the majority - both male and female - remained infertile for the remainder of their lives.

The findings were detailed in the journal Current Biology.