Development and neurotransmitter-environmental interactions

Norepinephrine (NE), dopamine (DA), and serotonin (5HT) are three of the more than thirty neurotransmitters (NTs) in the brain. Axons from a relatively small number of cell bodies located in the midbrain and brainstem branch out to connect with virtually all areas of the brain. Via these connections, these three NTs participate in the regulation of several behavioral systems that help modulate the interaction of the individual with his/her environment. Because the NT systems continue to develop after birth, interactions between the individual and his/her environment after birth may affect the development of these systems and have long-term effects on the individual's behavior. Animal studies indicate that early experience affects behavior and biogenic amine systems in the adult. For instance, one study showed that maternal deprivation, which is analogous to human neglect, affects the NE system in monkeys and may have a long-lasting effect on its development and function. In a previous study, similar relationships between early neglect and the NE system in humans were examined. Our results show that emotionally disturbed children with a history of neglect have lower dopamine-beta-hydroxylase (D beta H) activity, an enzyme involved in the synthesis of NE, than do children with no history of neglect. Additionally, the children with a history of neglect have lower systolic and diastolic blood pressure, both of which are functions mediated by the NE system, than the other children studied. These results support findings in animal studies that neglect affects the development of the NE system in a long-lasting, if not permanent way.