The “love hormone” makes mothers risk their lives to protect their young, study on rats reveals

A study on rats reveals that oxytocin, also called the love hormone, makes mothers risk their lives to protect their young. And scientists say the same process could be present in humans too. 

A team of neuroscientists from the Champalimaud Centre for the Unknown in Portugal discovered that the parents’ reaction to risk their own lives to protect their young is linked to the action of the so-called “love hormone”, on the amygdala, a specific brain structure that plays a crucial role when it comes to emotional reactions.

The scientists wanted to know why, when parents feel threatened in the presence of their young, their reaction is completely different than that exhibited the rest of times. Usually, when facing danger, animals respond by fleeing or stop moving, in an attempt to go unnoticed. But when the youngsters are present, parents seek to protect them.

The new study, which was done on female rats that had recently given birth, solves this mystery by bridging the gap between oxytocine and its effect on the amygdala.

“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, says Marta Moita, “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 in 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. But in the presence of the pups, the mothers did not freeze but tried to protect their young for the peppermint odor by attacking the tube where the scent came form.

The mothers also exhibited other behaviors. Some tried to block the tube by using nesting materials while those that had older pups started grooming them and keeping them in close contact with themselves.

Then scientists blocked oxytocin activity in the mothers’ amygdalas and the mothers started to freeze as soon as they perceived the threat, independently of the age of the pups.

Another result worthy of note was the fact that the older pups whose mother, instead of tending to them, had responded to the threat by freezing, because oxytocin in her amygdala was inhibited, did not learn to recognize the peppermint odor as a threat.

On the other hand, the pups whose mothers had duly cuddled them did freeze when confronted with the same situation.

Scientists think that similar processes could also be present in humans.