Which neurotransmitter is primarily increased by the action of MAOIs?

Monoamine oxidase inhibitors (MAOIs) primarily work by inhibiting the enzyme monoamine oxidase, which is responsible for breaking down neurotransmitters such as norepinephrine, serotonin, and dopamine in the brain. By inhibiting this enzyme, MAOIs lead to increased levels of these neurotransmitters in the synaptic cleft, enhancing their availability and activity.

Dopamine plays a role in mood and motivation, while serotonin and norepinephrine are crucial for regulating mood and emotional response. The increase of all three neurotransmitters—dopamine, serotonin, and norepinephrine—contributes to the overall antidepressant effect of MAOIs, making them effective in treating certain types of depression and anxiety disorders. Thus, stating that all of the neurotransmitters listed are increased by the action of MAOIs accurately reflects the pharmacological mechanism of these agents.