What do tricyclic antidepressants (TCA's) primarily affect?

Tricyclic antidepressants (TCAs) primarily function by inhibiting the reuptake of norepinephrine and serotonin in the brain, which leads to increased levels of these neurotransmitters in the synaptic cleft and enhanced neurotransmission. This mechanism is crucial in alleviating symptoms of depression and anxiety. While monoamine oxidases (MAOs) are involved in the breakdown of these neurotransmitters, TCAs do not directly affect these enzymes; instead, they inhibit the reabsorption process that maintains neurotransmitter levels.

The focus on serotonin levels is somewhat misleading in this context; while TCAs do increase serotonin levels, their primary action is broader, affecting both norepinephrine and serotonin simultaneously. Although dopamine also plays a role in mood regulation, TCAs are not specifically known for altering dopamine receptor sensitivity, which is more characteristic of other types of pharmacological treatments. Thus, the emphasis of TCAs on norepinephrine and serotonin reuptake inhibition distinguishes their primary action in treating depression and related disorders.