Dopamine D2 Antagonists

The D2 dopamine receptor is a G protein-coupled receptor that, unlike the D1-type receptors, couples to Gi/Go and inhibits adenylate cyclase. In the chemoreceptor trigger zone and the gastrointestinal tract, D2 activation suppresses gut motility and triggers vomiting; in the pituitary it restrains prolactin release. Drugs in this class block D2, which is why they act as antiemetics and prokinetics and why chronic blockade raises prolactin and can cause extrapyramidal signs.