Fig. 3.

Quinpirole- and haloperidol-induced changes in extracellular concentration of dopamine in WT and D2R−/− mice. The D2-specific agonist (quinpirole) and antagonist (haloperidol) were administered in WT and D2R−/− mice. Quinpirole and haloperidol, respectively, decrease and increased DA release in WT animals. In contrast, the two drugs had no effects in D2R −/− mice. Dialysates were collected in the striatum of freely moving animals every 20 min, and data are expressed as mean ± SEM of changes from baseline.