Oxytocin is a chemical that affects the brain and the entire body, functioning like a hormone. (Image credit: KATERYNA KON/SCIENCE PHOTO LIBRARY via Getty Images)
Studies in laboratory animals have shown that oxytocin, known as the “cuddle hormone” for its role in bonding, may also be involved in delaying early pregnancy.
New experiments in mice show that the hormone can put embryos in the earliest stages of their development into a state similar to hibernation. Once this process, known as “diapause,” is triggered, it can allow a mother mouse to delay pregnancy during times of resource scarcity — for example, while she is still nursing a previous litter of newborns.
“It was a little surprising to us that oxytocin had this effect,” study co-author Moses Chao, a neuroscientist at NYU Grossman School of Medicine, told Live Science.
Overall, diapause remains a bit of a mystery. It occurs in marsupials such as kangaroos and opossums, as well as at least 130 species of mammals, including mice and bats.
It can even happen in humans – although it’s hard to track in most human pregnancies, there are a few anecdotal reports from in vitro fertilization (IVF) clinics that suggest that, in rare cases, embryos transferred to the uterus can remain there for weeks before actually implanting. One case, reported in 1996, showed that it took five weeks after embryo transfer before pregnancy began.
It's currently unclear how long diapause can last, and little is known about how embryos enter this state of suspended animation, Chao said.
The study's first author, Jessica Minder, a graduate student at NYU Grossman School of Medicine, was interested in the role of oxytocin in diapause because the hormone is also known to be involved in embryonic development and lactation in mammals, including humans.
Minder and her colleagues began their work by placing male mice in the enclosures of females that had just given birth, allowing the rodents to mate while the females were still nursing their first pups. The researchers found that pregnancies produced under these conditions lasted about a week longer in lactating females than in those that weren’t.
The researchers suggest that this reflects a preimplantation “pause.” Since pregnancy in mice typically lasts only 19 to 21 days, this pause represents a significant slowdown in the process.
The team then began to explore how this pause might arise.
In another group of newly pregnant mice, the team used a technique called optogenetics, which uses light to activate specific neurons to trigger the mother mice's brains to produce oxytocin. The researchers timed this stimulation to mimic the oxytocin pulses seen during breastfeeding.
After five days of this treatment, they removed the mice's uteruses to assess embryonic development. Five of the six mouse mothers had embryos that were in a state of diapause, which means they weren't developing.
In the control group, pregnant mice that were not stimulated with oxytocin showed no signs of diapause.
In another experiment, the team treated early-stage mouse embryos with oxytocin in laboratory petri dishes, which also caused cellular changes characteristic of diapause.
Taken together, the data suggest that oxytocin caused the embryonic cells to slow down the translation of genes into proteins, the researchers reported March 5 in the journal Science Advances. This multistep process involves copying instructions from DNA into a new molecule called RNA, which is then delivered to the sites where the cell's proteins are assembled.
Sourse: www.livescience.com
