Study unlocks link between sex and female brain

August 20, 2012, University of Saskatchewan
These are crystals of pure OIF used at Canadian Light Source protein crystallography beam line. Credit: Yvonne Leduc, U of S

An international team of scientists led by Gregg Adams at the University of Saskatchewan has discovered that a protein in semen acts on the female brain to prompt ovulation, and is the same molecule that regulates the growth, maintenance, and survival of nerve cells.

Male mammals have accessory sex glands that contribute to semen, but the role of this fluid and the glands that produce it are not well understood.

"From the results of our research, we now know that these glands produce large amounts of a protein that has a direct effect on the female," says Adams, a professor of veterinary biomedical sciences at the Western College of Veterinary Medicine at the U of S.

The work, which appears in the August 20, 2012 issue of the (PNAS), raises intriguing questions about fertility in mammals, including humans.

The team characterized the protein, dubbed ovulation-inducing factor (OIF), that they have found in the semen of all species of mammal they have looked at so far. In the process of discovering its identity, the team compared OIF to thousands of other proteins, including (NGF) which is found primarily in throughout the body.

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

Gregg Adams with a University of Saskatchewan llama east of Saskatoon, Saskatchewan, Canada. Credit: Liam Richards for the University of Saskatchewan

While OIF/NGF may function differently from animal to animal, it is present in all mammals studied so far, from llamas, cattle and koalas to pigs, rabbits, mice, and humans. This implies an important role in reproduction in all mammals. Just how it works, its role in various species, and its clinical relevance to human infertility are a few of the questions that remain to be answered.

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).

For this latest study, the team looked at two species: llamas and cattle. Llamas are "induced ovulators," that is, they ovulate only when they have been inseminated. Cows – and humans – are "spontaneous ovulators," meaning that a regular buildup of hormones stimulates the release of an egg.

Using a variety of techniques, the researchers compared OIF and NGF and found them to have the same size and to cause the same effects across species. Work at the Canadian Light Source synchrotron at the U of S confirmed the structure of the molecule.

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

Explore further: Fertile? Not Without the Brain

More information: “The nerve of ovulation-inducing factor in semen," by Marcelo H. Ratto et al. PNAS.

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Aug 20, 2012
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1 / 5 (1) Aug 20, 2012
I am surprised that semenal proteins are so easily absorbed. In the digestive tract, proteins are broken down into amino acids before being absorbed for safety and convenience. Yet the reproductive tract and perhaps the mouth and throat (if he's lucky) seem to be letting this protein pass into the blood as they please.
1 / 5 (4) Aug 20, 2012
Hey...fellas...this aint helpin' us in MOST cases, I mean...the female has to have a BRAIN....damn!...there is always a catch, ya know! The Smart women...are looking for money and Hugh Hefner...the OTHERS are darn near born pregnant they're so easy.
SO now blame all the over-population on earth on a protein in semen....that's weak, feminist researchers of the world...that's weak!

4 / 5 (4) Aug 21, 2012
Sea men. Is there nothing they can't do?
not rated yet Aug 21, 2012
I've heard about the effects of semen itself on the mood of female friends of mine. I'm glad to see the cause of this effect isolated. Now, they need to begin coating condoms in NGF to increase their usage if it can be shown that it doesn't increase overall ovulation in humans.
1 / 5 (2) Aug 21, 2012
This makes evolutionary sense. There would be a hormone competition between males to make females
a)want to be covered by a smelly and possibly dangerous male and
b) be triggered into falling pregnant.
Would Mother Nature push drugs? Is the Pope a catholic?
not rated yet Aug 21, 2012
Semen from the "p-nas"

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