D2 dopamine receptor activation inhibits basal and forskolin-evoked acetylcholine release from dissociated striatal cholinergic interneurons

We tested whether D2 ligands inhibit basal and forskolin-stimulated [³H]ACh release from dissociated striata, as opposed to striatal slices. Quinpirole inhibited both basal (40% maximal inhibition; IC₅₀ ≈ 50 nM) and 10 μM forskolin-stimulated release (80% inhibition; IC₅₀≈25nM quinpirole) and both actions were blocked by a D2 antagonist. Vesamicol prevented the quinpirole and forskolin actions. The ability of D2 agonists to inhibit basal and cyclase-stimulated acetylcholine release emanating from vesamicol-sensitive vesicles appears to be tonically suppressed by inhibitory elements within striatal circuitry.