Dopamine D2 receptor (partial agonist)

Class

atypical antipsychotic; partial agonist at dopamine D2 and D3 receptors and serotonin 5-HT1A receptor, antagonist at serotonin 5-HT2A receptor (Ki 0.34/0.8/1.7/3.4 nM at D2/D3/5-HT1A/5-HT2A respectively); Abilify Maintena is an intramuscular extended-release injectable suspension of aripiprazole dosed monthly, requiring oral aripiprazole overlap for 14 days after the first injection

Pathway

partial agonism at D2 receptors stabilizes dopaminergic neurotransmission in mesolimbic and mesocortical pathways, producing a submaximal response relative to full agonism by dopamine but greater than antagonism, reducing positive symptoms while limiting extrapyramidal side effects

The dopamine D2 receptor is a G-protein-coupled receptor that mediates the actions of dopamine in brain circuits governing mood, cognition, and motor control. In psychotic disorders, excessive dopaminergic signaling in mesolimbic pathways is thought to drive positive symptoms such as hallucinations and delusions, while relative deficiency in mesocortical pathways contributes to negative and cognitive symptoms. Traditional antipsychotics block D2 receptors outright, which controls psychosis but can excessively dampen dopamine tone elsewhere, producing movement disorders and elevated prolactin. Partial agonism offers an alternative approach: the drug binds D2 receptors and produces a submaximal response—weaker than dopamine itself but stronger than an inert blocker—so that signaling is stabilized rather than shut off. In dopamine-rich states, the partial agonist behaves functionally as an antagonist, dampening excess activity; in dopamine-poor states, it behaves as a modest agonist, supporting baseline tone. This mechanism also extends to related receptors, including the D3 receptor and the serotonin 5-HT1A receptor (also partial agonism) and 5-HT2A receptor (antagonism), which together shape mood, anxiety, and side-effect profile. This class is used broadly across schizophrenia, bipolar disorder, and as adjunctive treatment for depression.