Posted by Shawn. T. on July 5, 2005, at 0:58:20
In reply to Re: Saredutant looks like a winner, posted by linkadge on July 4, 2005, at 15:25:11
In general, the brain can best take care of business when extracellular neurotransmitter levels are neither too low nor too high. An increase in the activation of alpha-1-adrenoceptors by norepinephrine in the prefrontal cortex can result in stress-induced cognitive deficits.
An article in Science by Amy Arnsten (1998) called "The Biology of Being Frazzled" addressed this point:
"These studies emphasize the importance of dopamine D1 receptor actions in taking the prefrontal cortex 'off line' during stress. Other neuromodulators may contribute as well [for example, norepinephrine via a1-adrenoceptors (14)], ensuring rapid yet reversible loss of prefrontal cortical control over behavior.
This bimodal reaction to stress likely had survival value in evolution: Under stress, the faster, habitual, or instinctual mechanisms regulated by the amygdala, hippocampus, striatum, and posterior cortices would control behavior, and long-lasting memories of aversive stimuli would be enhanced in order to avoid such stimuli in the future. However, in modern human society these brain actions may often be maladaptive; now we need prefrontal cortex regulation to act appropriately."
I wouldn't use the same language to describe this phenomenon, but she is basically explaining why excess neurotransmitter levels are not always a good thing.
Shawn
poster:Shawn. T.
thread:523047
URL: http://www.dr-bob.org/babble/20050702/msgs/523605.html