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Stimulation of D‐2 Dopamine Receptors Decreases the Evoked In Vitro Release of [3H] Acetylcholine from Rat Neostriatum: Role of K+ and Ca2+

Abstract: Reportedly, stimulation of D‐2 dopamine receptors inhibits the depolarization‐induced release of acetylcholine from the neostriatum in a cyclic AMP‐independent manner. In the present study, we investigated the role of K+ and Ca2+ in the D‐2 receptor‐mediated inhibition of evoked [3H]acetylcholine release from rat striatal tissue slices. It is shown that the D‐2 receptor‐mediated decrease of K+‐evoked [3H]acetylcholine release is not influenced by the extracellular Ca2+ concentration. However, increasing extracellular K+, in the presence and absence of Ca2+, markedly attenuates the effect of D‐2 stimulation on the K+‐evoked [3H]acetylcholine release. Furthermore, it is shown that activation of D‐2 receptors in the absence of Ca2+ also inhibits the veratrine‐evoked release of [3H]acetylcholine from rat striatum. These results suggest that the D‐2 dopamine receptor mediates the decrease of depolarization‐induced [3H]acetylcholine release from rat striatum primarily by stimulation of K+ efflux (opening of K+ channels) and inhibition of intracellular Ca2+ mobilization.