Norepinephrine: The Stress Hormone
To many of you, norepinephrine may be the least recognized of neurotransmitters involved in depression/ anxiety disorders. Though it does not play a role as major as serotonin or dopamine, it still is an integral member of the family that regulates mood (serotonin, norepinephrine, dopamine).
I’m sure most of you have heard of “fight and flight”. Scientifically, this term refers to dopamine and norepinephrine (noradrenaline) levels that rise in response to stressful situations, fear, aggravation. It is what we commonly refer to as an “adrenaline” rush. Norepinephrine is responsible for the following:
- Concentration, focus, vigilance
- Increased heart rate
- Increased blood sugar levels
- Increased blood pressure
- Increased muscle contractility
- Formation of neurons involved in memory and emotion (hippocampus)
In depression, due to severe amounts of stress, the norepinephrine system starts to alter its’ function, reducing motivation to respond to stress, or act under pressure. The altered function can induce hypothalamic–pituitary–adrenal axis (HPA axis) hyperactivation and high cortisol release. Higher level of cortisol is associated with various receptors activation leading to reduced neurotransmitter release (e.g., serotonin, dopamine noradrenaline (norepinephrine) and reduced neurogenesis (new brain cell formation). Melancholic depression is associated with hyperactivation of HPA axis.