Increased Serotonin Release -> acts as a functional “indirect agonist” at the serotonin 5-HT1A receptor
Increased serotonin 5-HT1A receptor activation is believed to be major mediator of mirtazapine and most antidepressant drugs
However, mirtazapine does not have any significant affinity for the serotonin, norepinephrine, or dopamine transporters -> lacks any significant effects as a reuptake inhibitor of these neurotransmitters
Also, mirtazapine does not have any significant inhibitory effects on monoamine oxidase (MAO)
Antagonism at Serotonin 5-HT2 Subfamily Receptors and Inverse Agonism at 5-HT2C Serotonin Receptor: likely responsible for at least part of mirtazapine’s antidepressant effect