One thing is true amongst animals and mammals: in a situation where an impending danger is more likely to overpower an animal in a combative struggle, the animal will not want to face the danger; it will either run away or freeze still so that it will not be noticed by the danger. This attribute is true for all animals (and mammals). However, the situation changes when the animal is faced with a danger in the company of her offspring that cannot afford to run on its own. In this case, instead of the animal to run away as usual, she will risk her life and attack the danger or its source as case may be, without minding if she would be overpowered in the fight. Taking a local hen for example; an hen without her chicks will never attack a danger (humans or other animals). She would rather run away. But not when she's with her chicks; in this case, she will attack as you approach them, laying down her life in defence of her offspring.
In this scenario, the question is: what could have triggered mothers to be willing to lay down their lives for the safety of their young? Why would they do that? What happened in their brains to make them switched from self-defensive posture to offspring-defensive posture? Scientists have always believed that as adrenalin, a hormone, is secreted in the body in order to prepare it to face a danger or run away from it, some kind of biochemical compound must also be responsible for the willingness of mothers to risk their lives in defence of their offspring. If that is so, then what is that compound?
In a ground breaking study involving a mommy-rat (also called dam) that was published in the Journal elife, neuroscientists from Champalimaud Centre for the Unknown in Lisbon, Portugal sought to determine what is responsible for the shift in mommy-rat's defensive behavior in the presence or absence of her pups. In the experiment, the team, which was led by Marta Moita, found that the observed radical change in the defensive behavior of mommy-rat is connected to the level of the activity of love hormone oxytocin on the neurons of the amygdala — a region of the brain that is implicated in the processing of emotional responses.
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Even before this breakthrough study that tied the mommy-rat's defensive behaviour to a change in the level of oxytocin in the amygdala, oxytocin has been known to be responsible for social bonding existing between mothers and their children, and also amongst couples. It is also implicated in the contractions of the uterus and cervix during sex and childbirth, as well as causing milk to be released in breastfeeding mothers. However, little is known of its role in the suppression of a self-defensive response in female animals until the breakthrough research by Marta Moita et al. It should also be noted that oxytocin is generally released into blood; but in the case of inhibition of fear response, the hormone is directly secreted into the central amygdala of the brainref.
Explaining the experiment
The first step in the experiment was training of mommy-rats in the absence of their pups to associate peppermint scent with imminent threat. The threat in this case is a mild electric shock. The mommy-rats having mastered the scent of the peppermint to be a danger, would always freeze upon perceiving it when their pups are not with them. However, when they are with their young, rather than freeze as usual upon perceiving the peppermint scent, they tried to protect their young by attacking the tube which is the source of the scent. They also piled up pieces of rubbishes and junks from their nest to obstruct the scent from coming out of the tube. If, however, their young is already several days older (from 19 days and more), the mommy-rats would huddle with them while keeping them closer to herself and shielding them from the source of the peppermint scent (probably because they are mature enough to run to safety if condition necessitates that).
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To establish whether oxytocin is implicated in this sudden change in the defensive behaviour of mommy-rats, the researchers inhibited the process that releases oxytocin in the amygdala. When this is done, the mommy-rats were observed to freeze upon perceiving the peppermint scent irrespective of whether their young are present or not, deviating from their usual maternal defensive behaviour.
This experiment has proven beyond any doubt that it is the love hormone, oxytocin, which triggers mother's defensive mechanism to shield their young from impending danger. Hence, demystifying the mystery of what gave mothers the courage to lay down their lives in defense of their offspring. The researchers believe that similar mechanism could also be at play in humans in all likelihood. Respect!
Sourced references
- The secret of a mother's love: study finds how the 'love hormone' oxytocin makes moms put their lives on the line to protect their children
- Rethinking the fear circuit: the central nucleus of Amygdala is required for the acquisition, consolidation, and expression of Pavlovian fear conditioning
- Why mother rats protect their children
- What makes a mother risk her life to protect her children
- Love hormone: why moms risk their lives to protect their children