In a discovery sure to stir intense discussion, scientists in Canada say they have discovered a powerful chemical signal embedded in semen which acts directly upon the brains of female mammals - apparently including humans.

In a just-released announcement arrestingly headlined "Team unlocks link between sex and the female brain", spokespersons at Saskatchewan uni in Canada lay out the groundbreaking boffinry.

It appears that scientists had for long known of a protein, dubbed ovulation-inducing factor (OIF), that is found in the semen of all species of mammal analysed to date including humans. In some species this chemical's effects are powerful indeed, causing a female to ovulate upon being inseminated. Human females aren't among this group, instead being among those known to science as "spontaneous ovulators", who release eggs to their own schedule.

Meanwhile another powerful chemical was also well known to science - nerve growth factor (NGF), which has a powerful effect in all mammals on all nervous tissues including those of the brain.

With the aid of a powerful atom-smasher, the Canadian Light Source synchrotron, the scientists sought to compare the molecular structure of both OIF and NGF among many other chemicals found in the body.

"To our surprise, it turns out they are the same molecule," says Gregg Adams, professor of veterinary biomedicine. "Even more surprising is that the effects of NGF in the female were not recognized earlier, since it's so abundant in seminal plasma."

Only having experimented so far upon llamas and cattle (lady llamas are of the ovulation-upon-insemination persuasion, whereas cows are spontaneous ovulators like humans), Adams and his colleagues are as yet unsure of the precise implications for human interaction of their amazing discovery. But they do note:

OIF/NGF in the semen acts as a hormonal signal, working through the hypothalamus of the female brain and the pituitary gland. This triggers the release of other hormones that signal the ovaries to release an egg (or eggs, depending on the species).

"The idea that a substance in mammalian semen has a direct effect on the female brain is a new one," comments Adams. "This latest finding broadens our understanding ... and raises some intriguing questions."

The new research is published in the new issue of the Proceedings of the National Academy of Sciences (PNAS). ®