August 21, 2012
Sex And The Female Brain – Semen Found To Prompt Mammalian Ovulation
John Neumann for redOrbit.com - Your Universe Online
A brave team of researchers led by Canadian Gregg Adams from the University of Saskatchewan have discovered a protein in semen that acts on the brains of females prompting ovulation, and is the same molecule that regulates the growth, maintenance, and survival of nerve cells, reports e! Science News.
The international team of researchers found that male mammals have accessory sex glands that contribute seminal fluid to semen, but the role of this fluid and the glands are not well understood.
Adams, a professor of veterinary biomedical sciences at the Western College of Veterinary Medicine at the University of Saskatchewan says, “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.”
It appears that scientists had long known of a protein, dubbed ovulation-inducing factor (OIF), that is found in the semen of all species of mammal analyzed to date, including humans, and in some species this chemical´s effects are powerful indeed.
The effects cause the females of some mammal species to ovulate upon being inseminated. Humans 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, writes Lewis Page for The Register.
“To our surprise, it turns out they are the same molecule,” says Adams. “Even more surprising is that the effects of NGF in the female were not recognized earlier, since it´s so abundant in seminal plasma.”
While OIF/NGF may function differently between species, 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.
What is known about OIF/NGF in the semen is that it 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,” Adams explains. “This latest finding broadens our understanding of the mechanisms that regulate ovulation and raises some intriguing questions about fertility.”
Previous research has already shown that NGF and similar proteins are made in human ovaries and have a local effect on how the eggs develop, says Sergio Ojeda, a neuroscientist at Oregon Health and Science University in Portland.
Adams however, believes the latest study indicates that seminal NGF may be acting like a hormone – making its way through the walls of the vagina, into the blood and all the way to the brain, where it stimulates the release of other hormones that affect the ovaries.
“The beauty of this paper was that they weren´t looking for NGF,” says Ojeda. The research, he says, is “extremely exciting because, in the past, the scientific community has sometimes been guilty of only going with the established dogma”.