Fig. 2.

Schematic drawings of a gamma-aminobutyric acid-ergic (GABAergic) synapse onto a striatal cholinergic interneuron in wild type and dopamine D2 receptor knockout (D2R KO) mice summarizing current data. Left Hypothesized localization of N- and P/Q-type calcium channels as well as of D2R in wild-type mice. Pharmacological results using selective blockers suggest the possibility that P/Q-type calcium channels are localized more closely to the release site than N-type calcium channels, which are coupled to D2R. The bar below GABA _A R on the postsynaptic membrane represents the inhibitory effect, with the width corresponding to the magnitude of inhibition. Right In D2R KO mice, deletion of D2R results in a reduced contribution of N-type calcium channels and an increased contribution of P/Q-type calcium channels. Note the smaller size of the N-type calcium channels in D2R KO mice in the schema and the larger size of the P/Q-type calcium channels, compared with those in wild-type mice. Additional unknown factors should mediate the change in total neuronal activity of cholinergic interneurons