Functional classification of different dopamine receptors.

A series of experiments is described in which behavioral models and intracerebral dialysis were used to study neurotransmitter release and which illustrate the functional properties of different dopamine receptors. Evidence is presented for the existence of postsynaptic D-1 dopamine receptors, which are preferentially stimulated by apomorphine and inhibited by SCH 23390, and postsynaptic D-2 receptors, which are preferentially stimulated by pergolide and inhibited by sulpiride. On the basis of results obtained following systemic and local treatment with picrotoxin it seems probable that D-2 receptors are located on GABA interneurons in the striatum. Furthermore, lesion studies indicate that the D-1 and D-2 receptors are related to different neuronal pathways. In contrast to postsynaptic dopamine receptors, presynaptic autoreceptors, as studied by recording the decrease in exploratory behavior and dopamine release, seem not to differ in their response to apomorphine and pergolide. Sulpiride selectively inhibits dopamine autoreceptors and is equally potent in inhibiting apomorphine and pergolide autoreceptor-dependent responses. In summary, the data strongly support the existence of functionally important D-1 and D-2 receptors.