ABSTRACT
Classically, pharmacological treatment of depression has consisted of
agents that affect neurotransmission involving three monoamines: sero-
tonin, norepinephrine, and/or dopamine. From the 1950s through the
1980s, two classes of agents, the monoamine oxidase inhibitors (MAOIs)
and the tricyclic antidepressants (TCAs), dominated the treatment of
depression. MAOIs increase levels of serotonin (5-HT), norepinephrine
(NE) and dopamine (DA) by blocking their metabolism by monoamine
oxidase (MAO). Thus, they are non-selective. The original MAOIs
also have irreversible effects, that is, they bind permanently to
MAO, inactivating the enzyme until it is metabolized. TCAs exert their
therapeutic actions through blockade of norepinephrine and/or sero-
tonin reuptake.
