Many of the medications to treat depression are thought to involve systems utilizing the monoamine neurotransmitters, noradrenaline, dopamine, and serotonin (5-HT). Draw the structures of these neurotransmitters. Why are they called monoamines? Illustrate their structural resemblance to one another. Monoamine oxidase inhibitors (MAOIS) increase CNS synaptic concentrations of these monoamines by inhibiting an enzyme responsible for their degradation. Draw the reaction scheme for the biological degradation of noradrenaline by monoamine oxidase. 3. Illustrate how the TCAs and SSRIs might resemble the monoamine neurotransmitters, providing one example of each class of antidepressant.