What Licked Rats Can Tell Us about Our Brain’s DNA for Resilience

“Our biological inheritance, the temperament with which we are born, the care we receive, our family relationships, the place where we grow up, the schools we attend, the culture in which we participate, and the historical period in which we live—all these affect the paths we take through childhood and condition the remainder of our lives.” ~Robert H. Wozniak

I wrote a post earlier this month about resilience, and I mentioned a study about how our resilience is genetically pre-determined.  I came across another study recently that discusses how while we may have the genetics that pre-determine how resilient we are, nurture may be more powerful than nurture.  In other words, even if we are genetically pre-disposed to be more or less resilient, we can influence whether the genes that control resilience are activated or suppressed.

What “licked” rats can tell us

The study, conducted by Michael Meaney, investigated why some rats, after giving birth to babies, patiently licked the rats while other mother rats ignored their newborns.  He noticed that the “licked” rats grew up to be relatively good at handling the stress of being placed in unfamiliar settings, while the “unlicked” rats grew up to be much worse at handling stress.  The calm female rats grew to be “lickers,” while the nervous rats ignored their children when they had babies.  In other words, the “licked” rats grew up to be relatively more resilient when compared to the “unlicked” rats.

The findings of the study — an explanation

It turns out that the “licked” rats secreted less stress hormone than the “unlicked” rats.  There are receptors that respond to the stress hormone in the hippocampus of the brain.  The “licked” rats had less receptors to the stress hormone than the “unlicked” rats.  So, more stress hormones plus more receptors for the stress hormones equals a more stressed rat.  Okay, now we’re getting deeper…Stay with me…

The “licking” of the rats increases the receptors in the hippocampus for serotonin, which causes the release of proteins called “transcription” factors which turns “on” the gene that inhibits a stress response.  This gene which becomes activated causes the rat to be less “rattled” by stress, thus more resilient.

A twist was added to the study.  Because “non-licked” rats seemed to grow up to give birth to “nervous” rats, they took the babies of “licking” rats and put them under the care of “non-licking” mothers, and vice versa.  The result was that the babies of the “licking” rats, who were tended to (or really not tended to) by the “non-licking” mothers became nervous and skittish, and vice versa.  This means that while the babies of the “licking” rats had the genetics to be more resilient, the genetic switch that inhibits the stress response was never turned “on,” thus resulting in a nervous rat.

What does this tell us?

The implications of this study are significant.  The study really tests the “nature versus nurture” debate.  It appears, according to this study, that “nurture” is stronger than “nature,” or at the very least “nurture” can profoundly affect “nature.”  It appears that while our brain’s DNA for resilience is pre-determined, it is not pre-determined whether those genes will become activated.  Our resilience may not only be determined by our genetics; rather it may be significantly affected by our environment and upbringing.

Hearing about this study, and being the parent of young children, it makes me wonder about the effects of physical touch and cuddling on my children in regard to their feelings of security, resilience, and their response to stress.  Is it beneficial for our children to have ample physical contact with their parents?  Does physical contact and affection make our children more likely to be resilient?  It really gets me thinking.  Very interesting indeed…

What do you think?  I’d love to hear from you!

Photo source: http://www.sxc.hu/profile/puellakas