Semen may have a direct effect on the female brain a new study says.
Researchers in Canada said that a recently discovered protein - nerve growth factor (NGF) - in semen caused females to ovulate.
Live Science reported that NGF works as a hormonal signal that acts through the hypothalamus glad and pituitary gland in females.
The protein sparks the release of other hormones that help ovulation occur.
"The whole idea of having a chemical substance in the seminal plasma in the male affecting the female's brain and causing her to ovulate is really new for us," said researcher Gregg Adams, of the Western College of Veterinary Medicine at the University of Saskatchewan, reported TG Daily.
"Even more surprising is that the effects of NGF in the female were not recognized earlier, since it's so abundant in seminal plasma."
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The researchers said they are still not sure what effect it has in humans.
Most of the testing was done on cows, which showed that NGF helped contribute to viable pregnancies, said Live Science.
According to a statement, the study authors said that the findings may help contribute to our understanding of fertility and reproduction.
"The idea that a substance in mammalian semen has a direct effect on the female brain is a new one," Adams explained in a statement.
"This latest finding broadens our understanding of the mechanisms that regulate ovulation and raises some intriguing questions about fertility."
Proceedings of the National Academy of Sciences (PNAS).