Dopamine D2 and serotonin 5-HT2A receptors (antagonist)

Class

atypical antipsychotic

Pathway

postsynaptic dopamine D2 and serotonin 5-HT2A receptor antagonism in mesolimbic and mesocortical pathways

Dopamine D2 and serotonin 5-HT2A receptors are G-protein-coupled receptors that atypical antipsychotics block simultaneously. D2 receptors are the primary site through which excess dopaminergic signaling in mesolimbic brain circuits is thought to produce the positive symptoms of psychosis, such as hallucinations and delusions; antagonizing D2 dampens this overactive signaling. Older antipsychotics relied on D2 blockade alone, which is effective against positive symptoms but tends to cause movement disorders and elevated prolactin because dopamine pathways elsewhere in the brain are also affected. Adding antagonism of 5-HT2A receptors, which normally restrain dopamine release in some of these same circuits, partially offsets that dopamine reduction outside the mesolimbic pathway, lowering the risk of movement-related side effects while preserving antipsychotic benefit. This dual-receptor strategy defines the 'atypical' class and is used broadly across schizophrenia, bipolar disorder, and related psychotic or mood conditions where dopaminergic and serotonergic signaling are dysregulated. The specific balance between D2 and 5-HT2A affinity varies across individual agents, shaping differences in efficacy and tolerability, but the underlying rationale, dampening excessive dopaminergic drive while limiting collateral effects through serotonergic modulation, is shared across the class.