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DOPAMINE receptors are classified into D_l and D₂ subtypes on the basis of their pharmacological properties and the intracellular responses they mediate¹. The cerebral D₂ dopamine receptor is the target of drugs used to alleviate the main symptoms of schizophrenia^2–4. Although it is considered to be a single molecular entity, there is evidence that multiple D₂-receptor subtypes exist^5,6. A complementary DNA encoding a D₂ receptor has recently been cloned⁷ and the deduced 415-amino-acid sequence indicates that it belongs to the large superfamily of receptors coupled to G proteins, and that its topology consists of seven transmembrane domains. In this family, the genes are frequently without introns and each is believed to encode a unique polypeptide product. Here we show that the gene for the D₂ receptor produces two receptor isoforms by alternative messenger RNA splicing, providing a route to …