Stress

Let's face it, we live in a stressfull society.  If I ask ten people what is stressing them out right now, I will get ten different answers.  Most people focus on the things that are providing emotional or psychological stress (i.e. their significant other, the stock market, what to make for dinner, the balance of their bank account, etc.), yet very few identify physical stress (exercise) or immune stress (that cold you're fighting off) as sources of stress.  Stress, as we're talking about this week, is any number of situations that causes activation of the fight or flight response.  We all know that in stressful situations, our logical thinking patterns are less clear, attention span may be decreased, and memories are not formed as readily.  This is caused by the blockage of dopamine release and dopamine binding by epinephrine in the system.  That explains short term stress, but what about long term stress?  Very few stresses that we experience in today's society are short term, "flight or fight" responses.  To start loonking at this question, let's start at the very beginning...

Prenatal stress produces learning deficits associated with an inhibition of neurogenesis in the hippocampus, yikes.  Ok, this looks pretty bad.  The above study found that rat pups whose mothers had experienced stress during pregnancy experienced a greater decline in cells proliferation in the hippocampus than rat pups with mothers that did not experience stress during pregnancy.  Lifelong, these changes in hippocampal cell proliferation resulted in a 45% difference between prenatally stressed and non-stressed rats.  The "stress rats" also showed delayed learning on a spatial memory task and had an altered response to the spatial memory task, which normally causes increased cell growth in the hippocampus.  The theory advanced by the researchers here is that the early exposure to stress causes an increase in Hypothalamic-Pituitary-Adrenocortical Axis (HPA) activity, resulting in early exposure to corticosteroids.  Corticosteroids are known to alter the structure and function of the cells in the hippocampus, hence the changes that were demonstrated in this experiment. 

That all seems like really bad news, but here's the good news: a second study (abstract) found that postnatal care desined to decrease infant stress reduced ALL of the effects from the first study.  In addition, other studies have found that rat mothers naturally give their pups extra TLC after a stressful pregnancy.  This additional care post partum may be nature's way of correcting, or "making up for", the harm caused by corticosteriod secretion during the pregnancy process.  Smart rats, now we just need to teach people to do the same, right? :)