Oxytocin associated with offspring protection response in parents' brains

June 14, 2017
A rat mum cuddles her pups when a threat looms. Credit: Shira Lottem/ Champalimaud Centre for the Unknown

From birds to mammals, from fish to reptiles, the immediate reaction to an impending threat to the animal itself is usually to flee or to stop moving in an attempt to go unnoticed. However, when parents feel threatened in the presence of their young, their reaction is completely different— to protect their offspring. What changes in the brains of parents causing this protective response?

A team led by neuroscientists from the Champalimaud Centre for the Unknown in Lisbon, Portugal, has discovered that this radical change in the parents' behavior (from self-defense to defending their young) depends on the action of the so-called "love hormone," , on the neurons of the amygdala, a specific brain structure known for its crucial role in the processing of emotional reactions. Their results have been published in the journal eLife.

Oxytocin is responsible for the bonding between mothers and their young, and within couples. Its effects are not well understood; oxytocin probably has many functions, making its study difficult.

Experts do know, however, that its release into the amygdala inhibits the basic self-defense reaction of freezing, when a frightened animal ceases to move. But the potential usefulness of this inhibition had not been elucidated. The new study, which involved that had recently given birth, solves this mystery by bridging the gap between these two phenomena.

"We put both things together," says Marta Moita, who led the study. "We developed a new experiment that allows us to study the mother's defensive behavior either in the presence or the absence of her pups, while at the same time testing whether oxytocin's action in the amygdala is required for the regulation of this behavior."

Since oxytocin acts on many parts of the brain, affecting many behaviors, it is usually difficult to interpret the results when manipulating this hormone. But in the new experiments. Marta Moita says, "We manipulated a circuit where we know precisely how oxytocin leads to inhibition of freezing. So we are very sure of our interpretation of the behavioral results."

The experiments consisted of conditioning the mother rats, in the absence of their pups, to associate a peppermint scent with the imminence of an innocuous electric shock. After training, these female rats perceived the odor as a threat and froze accordingly.

Once the training was over, the team started by showing that, in the pups' presence, the mothers didn't freeze, as they had when they were alone. Instead, they now tried to protect their offspring from the peppermint odor by attacking the tube where the odor originated, or piling up bits of material from the nest to block the tube—or, if the pups were a little older, by nursing them, grooming them and generally keeping them in close contact.

However, when the scientists then blocked oxytocin activity in the mothers' amygdalas, the mothers froze as soon as they perceived the threat, independently of the age of the pups—forgetting, so to speak, their maternal "duties."

This work provides a new experimental framework to study the specific stimuli of the pups that make their mother's brains release oxytocin into the in the face of danger, triggering the defensive strategy to protect their offspring, says Marta Moita. "We know that chemical communication is very important, but we still haven't identified the sensory stimuli that activate oxytocin," she adds.

Another result worthy of note was the fact that the older pups whose mothers responded to the threat by freezing did not learn to recognize the peppermint odor as a threat. More specifically, when these pups were later placed by themselves in a box and exposed to the same odor, they did not freeze. On the other hand, the pups whose mothers had protected them learned to freeze when confronted with the same situation. A pheromone emitted by the caring mother might be at the root of this type of learning by the older , Marta Moita speculates.

"In all likelihood," she concludes, "similar mechanisms may be at play in us humans."

Explore further: How oxytocin makes a mom: Hormone teaches maternal brain to respond to offspring's needs

More information: Elizabeth Rickenbacher et al, Freezing suppression by oxytocin in central amygdala allows alternate defensive behaviours and mother-pup interactions, eLife (2017). DOI: 10.7554/eLife.24080

Related Stories

How oxytocin makes a mom: Hormone teaches maternal brain to respond to offspring's needs

April 15, 2015
Neuroscientists at NYU Langone Medical Center have discovered how the powerful brain hormone oxytocin acts on individual brain cells to prompt specific social behaviors - findings that could lead to a better understanding ...

Gut microbiome of mother found to impact immunity of mice pups

March 18, 2016
(Medical Xpress)—A team of researchers from Switzerland and Germany has found that the gut microbiome of a pregnant mouse can have an impact on the development of the immune system in the pups she delivers. In their paper ...

Recommended for you

New study rebuts the claim that antidepressants do not work

August 18, 2017
A theory that has gained considerable attention in international media, including Newsweek and the CBS broadcast 60 minutes, suggests that antidepressant drugs such as the SSRIs do not exert any actual antidepressant effect. ...

Should I stay or should I leave? Untangling what goes on when a relationship is being questioned

August 17, 2017
Knowing whether to stay in or leave a romantic relationship is often an agonizing experience and that ambivalence can have negative consequences for health and well-being.

Kids learn moral lessons more effectively from stories with humans than human-like animals

August 17, 2017
A study by researchers at the Ontario Institute for Studies in Education (OISE) at the University of Toronto found that four to six-year-olds shared more after listening to books with human characters than books with anthropomorphic ...

History of stress increases miscarriage risk, says new review

August 17, 2017
A history of exposure to psychological stress can increase the risk of miscarriage by upto 42 per cent, according to a new review.

Study finds children pay close attention to potentially threatening information, avoid eye contact when anxious

August 17, 2017
We spend a lot of time looking at the eyes of others for social cues – it helps us understand a person's emotions, and make decisions about how to respond to them. We also know that adults avoid eye contact when anxious. ...

Communicating in a foreign language takes emotion out of decision making

August 16, 2017
If you could save the lives of five people by pushing another bystander in front of a train to his death, would you do it? And should it make any difference if that choice is presented in a language you speak, but isn't your ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.