Effect on dopaminergic tracts

Mesocortical-mesolimbic dopamine receptor blockade presumably underlies antipsychotic effects, and a similar action on the chemoreceptor trigger zone leads to the useful antiemetic properties of some antipsychotic drugs. Adverse effects resulting from receptor blockade in the other dopaminergic tracts, a major problem with older antipsychotic drugs, include extrapyramidal dysfunction and hyperprolactinemia. Note that almost all antipsychotic agents block both α1 and histamine H1 receptors to some extent.