Dopamine D2 and serotonin 5-HT1A receptors (partial agonist)

Class

Atypical antipsychotic (quinolinone-class dopamine-serotonin system stabilizer); also antagonist at serotonin 5-HT2A receptors; Abilify Maintena is an extended-release intramuscular injectable suspension administered monthly in the deltoid or gluteal muscle

Pathway

Partial agonism at dopamine D2 and serotonin 5-HT1A receptors combined with antagonism at serotonin 5-HT2A receptors is proposed to underlie aripiprazole's antipsychotic effect, distinguishing it mechanistically from full D2-antagonist antipsychotics

This mechanism targets the dopamine D2 receptor and two serotonin receptors, 5-HT1A and 5-HT2A, which together regulate mood, thought, and motor control. In several psychiatric conditions, dopamine signaling becomes unevenly distributed across brain circuits — overactive in pathways linked to hallucinations and delusions, but underactive in circuits governing motivation and cognition. Traditional antipsychotics block D2 receptors uniformly, calming the overactive pathway but worsening the underactive ones, producing movement and cognitive side effects. This mechanism instead uses partial agonism at D2: the molecule activates the receptor weakly, damping excessive signaling while still providing a baseline of activity where dopamine tone is low. Partial agonism at 5-HT1A contributes to mood regulation, while antagonism at 5-HT2A modulates cortical dopamine release and can offset movement-related side effects. Together, these actions are described as a 'system stabilizer' approach rather than blunt blockade. This mechanism is broadly relevant to schizophrenia, bipolar disorder, and as an adjunct in major depressive disorder, where restoring balance across dopamine and serotonin circuits, rather than uniformly suppressing them, is the therapeutic goal.