Stimulation of D2-dopamine receptors in rat neostriatum inhibits the release of acetylcholine and dopamine but does not affect the release of gamma-aminobutyric acid, glutamate or serotonin.

D1-dopamine receptor stimulation did not affect the K+-induced release of [3H]GABA, [3H]glutamate, [3H]serotonin, [3H]dopamine and [14C]acetylcholine from slices of rat neostriatum. D2-dopamine receptor stimulation did not change the release of [3H]GABA, [3H]glutamate and [3H]serotonin, but inhibited the release of both [3H]dopamine and [14C]acetylcholine; this inhibition was antagonized by (-)-sulpiride. The release-inhibiting dopamine autoreceptors and the post synaptic dopamine receptors mediating the inhibition of acetylcholine release appear to be pharmacologically similar and can be classified as D2-receptors.