Seven years after the cloning of the rat dopamine D receptor, and four 2 years after the cloning of the last mammalian dopamine receptor identified to date, this seems to be an excellent time to put together the present The Dopamine Receptors volume ofthis series, The Receptors. There has been time for considerable characterization of the novel receptor subtypes, and new, exciting lines of research from the molecular to the behavioral levels are taking shape. We asked the contributors to The Dopamine Receptors to follow the superb example set by the previous volumes in this series by writing compre hensive, historical reviews that will comprise an essential resource for nonspe cialists and newcomers to the dopamine receptor field, while at the same time providing up-to-date summaries of the most active areas of research. It is difficult these days to write about receptors without addressing the issue of receptor nomenclature. For dopamine receptors, valid arguments can be made for a system in which the subtypes are classified as belonging to the Dl or D2 classes, with letters assigned in the order of cloning (D A, D , D A, 1 18 2 D , Dc). We decided, however, that common usage counts for something, and 28 2 chose to use D , D , and D for the D2-like receptors because these names are 2 3 4 nearly unanimously used in the literature.
