Researchers discovered that monoamine oxidase breaks down and removes from the synapses two neurotransmitters: noradrenaline and serotonin. Without enough of these neurotransmitters, people experience symptoms of depression. The scientists reasoned that inhibiting the action of the enzyme that removes the monoaminergic transmitter from the synapse leaves more noradrenaline and serotonin in the synapses, thereby relieving the symptoms of depression. Thus, the idea of monoamine oxidase inhibitors as a treatment for depression was born.
