Posted by Elroy on June 21, 2005, at 18:06:56
In reply to Re: HPA Axis and Anti-Cortisol Therapy » 4WD, posted by Elroy on June 20, 2005, at 12:44:20
http://www.mcmanweb.com/article-44.htm
In an article in the Sept 2003 Scientific American, Robert Sapolsky PhD of Stanford writes on how the fight or flight response underpins both anxiety and depression.
The primate stress response, Dr Sapolsky begins, can be set in motion by the mere anticipation of an event, and when we erroneously believe a stressor is about to happen we "have entered the realm of neurosis, anxiety, and paranoia." The amygdala in the brain receives input on a conscious level from the cortex and unconsciously from specialized parts of the brain. In response to a perceived threat, the amygdala sets off a chain of events that results in the hormone CRF signaling the brain stem, which activates the sympathetic nervous system. In response, the adrenal glands produce adrenaline (epinephrine) and through a different pathway cortisol, both which prepare the body for fight or flight.
In addition, the amygdala sends information back to the frontal cortex and to sensory cortices, which accounts for emotionally-influenced decision-making and vivid sensations, respectively. In addition, the amygdala is involved in memory. Paradoxically, stress can strengthen the ability of the amygdala to form implicit or preconscious memories while inhibiting the hippocampus’ ability to form explicit or conscious memories. The individual may thus experience a fight or flight response to a voice in a crowd without knowing why, being unable to link the sound of that voice to the similar-sounding voice of a past assailant, resulting in "free-floating" anxiety.
Meanwhile, cortisol activates a brain region called the locus coeruleus, which sends norepinephrine to communicate back to the amygdala, thus initiating the stress response all over again and resulting in a destructive feedback cycle... The torpor of depression may appear to be the opposite of anxiety, but like anxiety can be related to stress. Moreover, depression is not a passive state. According to Dr Sapolsky, "the dread is active, twitching, energy-consuming, distracting, exhausting - but internalized. A classic conception of depression is that it represents aggression turned inward ..." In addition, several pharmaceutical companies have a CRF antagonist in development. Researchers are also working on drugs that target another hormone that regulates cortisol, glucocorticoid receptors (GRs). And the pregnancy-termination drug, RU486 (mifepristone) has demonstrated that it can zero in on the excess cortisol and ACTH that figure in psychotic depression....
poster:Elroy
thread:515432
URL: http://www.dr-bob.org/babble/20050617/msgs/516736.html