Abstract

The stress of foot shock in rats induces large decreases in the level of brain norepinephrine but does not greatly alter the concentration of serotonin or dopamine in brain. These decrements in norepinephrine are not limited to any region and occur uniformly throughout the brain. However, absolute levels of these amines are not a true indicator of their dynamic state. By various techniques it could be demonstrated that the stress of foot shock accelerates the metabolism of dopamine and serotonin to the same degree as norepinephrine; the only difference being that dopamine and serotonin are rapidly resynthesized, whereas norepinephrine in the brain cannot be regenerated at the same rate. Furthermore, the increased catabolism of brain norepinephrine with stress is blocked by monoamine oxidase inhibitors, whereas catechol-O-methyltransferase inhibitors do not impede accelerated degradation.